A black OCA optical adhesive and its preparation method

Abstract

This invention relates to optically transparent adhesives, and particularly to a black OCA optical adhesive for direct display panels, possessing integrated black color and easy reworkability, and its preparation method. To address the problem of uneven dispersion of carbon black in OCA adhesives in existing black OCA optical adhesives, this invention provides a black OCA optical adhesive and its preparation method. The black OCA optical adhesive comprises, from top to bottom, an upper OCA optical adhesive layer, a black layer, and a lower OCA optical adhesive layer. In the black OCA optical adhesive provided by this invention, carbon black is composited with graphene to form a film, and then the OCA layer is attached, avoiding the dispersion of carbon black in the OCA adhesive and solving the problem of uneven dispersion of carbon black in OCA adhesive.

Description

Technical Field

[0001] This invention relates to optically transparent adhesives, and more particularly to a black OCA optical adhesive for direct display panels, which has integral black color and easy rework properties, and a method for preparing the same. Background Technology

[0002] OCA (Optically Clear Adhesive) is an important special adhesive for bonding transparent optical components. It has stable chemical properties and has the advantages of reducing light loss from backlight, increasing transmittance, reducing energy consumption, increasing the contrast of optical components under strong light, improving surface bonding strength and avoiding Newton's rings.

[0003] For OCA directly bonded to mini LED / micro LED light panels, higher and more demanding performance is required. For example, the optical adhesive needs to be a monolithic black with suitable transmittance and haze to improve black contrast without affecting light transmission through the light panel; the monolithic black OCA needs to be quickly peeled off the light panel when the LEDs need to be replaced; and it needs UV resistance for outdoor applications. Monolithic black OCA formulated with organic pigments has a uniform film surface and high transmittance, but poor weather resistance, requiring additional heating equipment for peeling and repair. Monolithic black OCA prepared with carbon materials (such as carbon black, graphene, carbon nanotubes, fullerenes, or carbon spheres) has adjustable transmittance and superior weather resistance compared to organic pigments, but carbon materials are difficult to disperse in OCA adhesives, making uniform coating difficult and resulting in an uneven film surface. Summary of the Invention

[0004] To address the problem of uneven dispersion of carbon black in existing black OCA optical adhesives, this invention provides a black OCA optical adhesive and its preparation method. In the black OCA optical adhesive provided by this invention, carbon black and graphene are composited into a film, and then an OCA layer is attached, avoiding the problem of uneven dispersion of carbon black in the OCA adhesive. The advantages of this invention are mainly reflected in: (1) Pre-forming a graphene-carbon black composite film and then bonding it to a transparent OCA utilizes the high light transmittance of graphene and the coloring properties of carbon black, not only avoiding the dispersion problem between carbon materials and acrylic resin systems, but also achieving adjustable transmittance, haze, and hue of the integrated black OCA; (2) Utilizing the heat-generating property of graphene when electrically conductive, the problem of needing additional heating equipment to assist in the rework and peeling of the integrated black OCA from mini LEDs / Micro LEDs is solved; (3) Utilizing the excellent thermal conductivity of graphene, the heat generated during the operation of mini LEDs / Micro LEDs can be effectively transferred, solving the heat dissipation problem and extending the lifespan of the lamp board.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0006] The present invention provides a black OCA optical adhesive, which comprises, from top to bottom, an upper OCA optical adhesive layer, a black layer, and a lower OCA optical adhesive layer.

[0007] Furthermore, the black OCA optical adhesive comprises, from top to bottom, an upper OCA optical adhesive layer, a black layer, and a lower OCA optical adhesive layer.

[0008] The present invention provides a black OCA optical adhesive, which comprises, from top to bottom, a light release film, an upper OCA optical adhesive layer, a black layer, a lower OCA optical adhesive layer, and a heavy release film.

[0009] Furthermore, the black OCA optical adhesive comprises, from top to bottom, a light release film, an upper OCA optical adhesive layer, a black layer, a lower OCA optical adhesive layer, and a heavy release film.

[0010] Furthermore, the black layer is a graphene composite carbon black black layer, a graphene black layer, or a carbon black black layer.

[0011] The graphene in the graphene-carbon black composite layer provides light transmittance, electrical heating, and thermal conductivity for the integrated black OCA optical adhesive; the carbon black provides black coloring properties for the integrated black OCA optical adhesive. Carbon black has different hues, such as blue-phase carbon black and yellow-phase carbon black, which can give the integrated black OCA different hues.

[0012] Furthermore, the graphene composite carbon black black layer comprises graphene and carbon black.

[0013] Furthermore, the graphene is dispersed in carbon black.

[0014] Furthermore, the mass ratio of graphene to carbon black is 1:5.

[0015] The ratio of graphene to carbon black is not fixed and can be adjusted according to the desired hue. For example, graphene has a yellowish hue, and if yellowish carbon black is added, an overall yellowish black can be obtained, with the a value approaching 0 and the b value becoming positive; if blueish carbon black is added, a purer black can be obtained, with both the a and b values ​​approaching 0.

[0016] Furthermore, the graphene composite carbon black black layer is composed of graphene and carbon black combined together.

[0017] Furthermore, the thickness of the light release film is 30–150 μm; the thickness of the heavy release film is 50–150 μm.

[0018] Furthermore, the adhesion between the light release film and the upper OCA optical adhesive layer is less than the adhesion between the heavy release film and the lower OCA optical adhesive layer.

[0019] Furthermore, the upper OCA optical adhesive layer has a light transmittance greater than 90%, a haze of less than 0.5%, and a thickness of 5–100 μm. Light transmittance is simply referred to as transmittance or light transmittance.

[0020] Furthermore, the lower OCA optical adhesive layer has a transmittance greater than 90%, a haze less than 0.5%, and a thickness of 10–100 μm.

[0021] Furthermore, the upper OCA optical adhesive layer and the lower OCA optical adhesive layer are formed by acrylate adhesive, which contains 100-500 parts of acrylic polyol, 0.3-3.0 parts of toluene diisocyanate curing agent, 0.03-0.5 parts of bismuth salt catalyst, 0.2-2.0 parts of siloxane coupling agent, and 10-100 parts of ethyl acetate; the parts are by weight.

[0022] Furthermore, the graphene-carbon black composite layer is formed by mixing graphene nanosheets with carbon black, or by combining graphene and carbon black together. The black layer is translucent and conductive. Furthermore, the thickness of the black layer is 0.01–50 μm. Furthermore, the thickness of the black layer is 0.3–50 μm. Furthermore, the thickness of the black layer is 1–50 μm. Furthermore, the thickness of the black layer is 1–5 μm. Furthermore, the light transmittance of the black layer is greater than 40%.

[0023] Furthermore, the adhesion between the upper OCA optical adhesive layer and the graphene composite carbon black layer is greater than that between the heavy release film and the lower OCA optical adhesive layer; the adhesion between the lower OCA optical adhesive layer and the graphene composite carbon black layer is greater than that between the heavy release film and the lower OCA optical adhesive layer.

[0024] This invention also provides a method for preparing black OCA optical adhesive, the method comprising the following steps:

[0025] Step 1: Disperse graphene and carbon black in ethanol, and then spray the ethanol dispersion of graphene composite carbon black onto the water surface through a spray gun to form a thin film of graphene composite carbon black on the water surface.

[0026] Step 2: Spray the ethyl acetate solution of OCA adhesive upwards through a spray gun onto the graphene composite carbon black film, heat it to evaporate the ethyl acetate, and cure it into the lower OCA optical adhesive layer;

[0027] Step 3: Apply OCA adhesive to the other side of the graphene composite carbon black film and then cure it to form an upper OCA optical adhesive layer.

[0028] On the other hand, the present invention also provides a method for preparing black OCA optical adhesive, the method comprising the following steps:

[0029] Step 1: Disperse graphene in ethanol, and then spray the graphene ethanol dispersion onto the water surface through a spray gun to form a thin film of graphene on the water surface.

[0030] Step 2: Spray the ethyl acetate solution of OCA adhesive upwards through a spray gun onto the graphene film, heat it to evaporate the ethyl acetate, and cure it into the lower OCA optical adhesive layer;

[0031] Step 3: Apply OCA adhesive to the other side of the graphene film and then cure it to form an upper OCA optical adhesive layer.

[0032] On the other hand, the present invention also provides a method for preparing black OCA optical adhesive, the method comprising the following steps:

[0033] Step 1: Disperse carbon black in ethanol, and then spray the carbon black ethanol dispersion onto the water surface through a spray gun to form a thin film of carbon black on the water surface.

[0034] Step 2: Spray the ethyl acetate solution of OCA adhesive upwards through a spray gun onto the carbon black film, heat it to evaporate the ethyl acetate, and cure it into the lower OCA optical adhesive layer;

[0035] Step 3: Apply OCA adhesive to the other side of the carbon black film and then cure it to form an upper OCA optical adhesive layer.

[0036] On the other hand, the present invention also provides a method for preparing black OCA optical adhesive, the method comprising the following steps:

[0037] Step 1: Disperse carbon black in ethanol and disperse graphene in ethanol; spray the carbon black ethanol dispersion onto the water surface through a spray gun to form a carbon black film on the water surface; then spray the graphene ethanol dispersion upward through a spray gun and onto the carbon black film on the water surface to form a graphene composite carbon black film (i.e., black layer).

[0038] Step 2: Spray the ethyl acetate solution of OCA adhesive upwards through a spray gun onto the graphene composite carbon black film, heat it to evaporate the ethyl acetate, and cure it into the lower OCA optical adhesive layer;

[0039] Step 3: Apply OCA adhesive to the other side of the graphene composite carbon black film and then cure it to form an upper OCA optical adhesive layer.

[0040] On the other hand, the present invention also provides a method for preparing black OCA optical adhesive, the method comprising the following steps:

[0041] Step 1: Disperse graphene and carbon black in ethanol; spray the graphene ethanol dispersion onto the water surface through a spray gun to form a graphene film on the water surface; then spray the carbon black ethanol dispersion upward through a spray gun and onto the graphene film on the water surface to form a graphene composite carbon black film (i.e., black layer).

[0042] Step 2: Spray the ethyl acetate solution of OCA adhesive upwards through a spray gun onto the graphene composite carbon black film, heat it to evaporate the ethyl acetate, and cure it into the lower OCA optical adhesive layer;

[0043] Step 3: Apply OCA adhesive to the other side of the graphene composite carbon black film and then cure it to form an upper OCA optical adhesive layer.

[0044] A better preparation process is to first spray graphene ethanol solution to form a film, and then spray carbon black ethanol solution. This can effectively avoid the graphene coating carbon black first due to intermolecular hydrogen bonds, van der Waals forces, etc., which would prevent it from dispersing in ethanol.

[0045] This invention also provides a method for preparing black OCA optical adhesive, the method comprising the following steps:

[0046] Step 1: Disperse graphene and carbon black in ethanol, and then spray the ethanol dispersion of graphene composite carbon black onto the water surface through a spray gun to form a thin film of graphene composite carbon black on the water surface.

[0047] Step 2: Spray the ethyl acetate solution of OCA adhesive upwards through a spray gun onto the graphene composite carbon black film, heat it to evaporate the ethyl acetate and solidify it into the lower OCA optical adhesive layer, and then transfer it to the release film so that the release film is bonded to the other side of the lower OCA optical adhesive layer.

[0048] Step 3: Apply OCA adhesive to the other side of the graphene composite carbon black film using a coating machine, cure it to form an upper OCA optical adhesive layer, and then attach a light release film to the other side of the upper OCA optical adhesive layer.

[0049] This invention also discloses a method for preparing the above-mentioned black OCA optical adhesive, comprising the following steps:

[0050] Step 1: Using ultrasonic equipment, graphene and carbon black are dispersed in ethanol at a suitable ratio and concentration. Then, the ethanol dispersion of graphene-carbon black composite is sprayed onto a water surface using a spray gun. Due to the surface energy difference between the tiny droplets of ethanol dispersion and water, the Marangoni effect causes the graphene-carbon black composite to form a thin film on the water surface, i.e., a graphene-carbon black composite film. Furthermore, the mass of graphene must not be less than 20% of the mass of carbon black; otherwise, the heating and thermal conductivity properties will be weakened or lost. Further, the concentrations of graphene and carbon black are 0.3-1.0 wt%, for example, 0.3 wt%, 0.5 wt%, 0.8 wt%, and 1.0 wt%.

[0051] Step 2: Spray an ethyl acetate solution of OCA adhesive of appropriate concentration upwards onto the graphene composite carbon black film using a spray gun. Heat the film at 50℃~150℃ to evaporate the ethyl acetate and cure it into the lower OCA optical adhesive layer. Due to the small amount of oxygen-containing groups present in graphene and carbon black, they will react with the acrylate in the OCA adhesive to form covalent bonds. Combined with the adhesiveness of the OCA adhesive itself, the graphene composite carbon black film is tightly bonded to the lower OCA optical adhesive layer. Then, transfer it to the release film to bond the release film to the other side of the lower OCA optical adhesive layer.

[0052] Step 3: Apply a certain concentration of OCA adhesive to the other side of the graphene composite carbon black film using a coating machine, and cure it at 50℃~120℃ to form an upper OCA optical adhesive layer. Finally, attach a light release film to the other side of the upper OCA optical adhesive layer.

[0053] The beneficial effects of the present invention are as follows: (1) In the prior art, graphene and carbon black are directly dispersed in acrylic resin adhesive. Due to the large difference between the surface energy of graphene and carbon black and the acrylic resin adhesive solution, graphene / carbon black is very easy to agglomerate, resulting in uneven OCA adhesive film surface. However, the present invention uses a layer-by-layer method (layer-by-layer refers to: upper OCA layer - graphene composite carbon black layer - lower OCA layer, one layer on top of another) to first disperse graphene and / or carbon black in ethanol, and then spray it on the water-air interface. Under the Marangoni effect, the low surface energy area rich in ethanol will drive graphene and / or carbon black to flow to the high surface energy area rich in water, so that graphene and / or carbon black form a uniform film on the water surface. This film is bonded to the OCA adhesive / adhesive layer, completely avoiding the problem of graphene and / or carbon black precipitation in acrylic resin. (2) The film formed by the interpenetration of graphene nanosheets and carbon black has a uniform color, providing the blackness required for integrated black OCA, and the blackness can be adjusted by the type and amount of graphene and carbon black added; (3) Due to the resistance difference between the inside of the graphene nanosheets and the overlapping parts of the graphene nanosheets, it can generate heat and reach a temperature of 45-100°C when a small external voltage is applied. When it is necessary to peel off the adhesive layer, it can be quickly peeled off from the lamp plate without the aid of additional heating equipment, that is, it has easy rework performance. (4) The chemical stability of graphene and carbon black is stronger than that of organic pigments, and the UV resistance is stronger, which makes the integrated black black OCA optical adhesive disclosed in this invention have broad prospects for outdoor and automotive applications. Attached Figure Description

[0054] Figure 1 Photograph of the film surface after carbon black is dispersed in OCA adhesive and coated;

[0055] Figure 2 This is a schematic diagram of the cross-sectional structure of a black OCA optical adhesive provided by the present invention. Detailed Implementation

[0056] To better understand the structure, functional features, and advantages of this invention, the following description, in conjunction with the accompanying drawings and specific embodiments, will further illustrate the invention so that those skilled in the art can better understand and implement it. However, the embodiments described are not intended to limit the invention.

[0057] This invention provides a black OCA optical adhesive, such as... Figure 2 As shown, from top to bottom, it includes a light release film 1, an upper OCA optical adhesive layer 2, a black layer 3, a lower OCA optical adhesive layer 4, and a heavy release film 5. The sheet-like structure in the black layer 3 is graphene, and the spherical structure is carbon black.

[0058] The main properties of the black OCA optical adhesive provided by this invention are determined using the following standards or methods.

[0059] 1. Transmittance: ISO 13468-1 Determination of total light transmittance of transparent plastic materials - Part 1: Single beam light emission apparatus.

[0060] 2. Haze: ISO 14782 Determination of haze in transparent plastic materials.

[0061] 3. Color difference: ISO / CIE11664-6 Colorimetry Part 6: CIEDE2000 Color Difference Formula.

[0062] 4. Temperature: Measured by a handheld temperature sensor.

[0063] 5. Adhesive thickness: Measured with a micrometer.

[0064] Comparative Example 1

[0065] Weigh 0.3g of carbon black powder, 0.5g of carbon black dispersant and 99.2g of ethyl acetate, put them into a contact cell disruptor and ultrasonically disperse them for 2 hours at 200W power.

[0066] Subsequently, 20g of a 0.3wt% carbon black ethyl acetate dispersion and 300g of OCA adhesive were weighed and stirred at 1000r / min for 0.5h to obtain an integrated black OCA adhesive. The integrated black OCA adhesive was coated onto a 75μm heavy release film using a 250μm four-sided coater and cured in an oven at 80℃ for 2h. Then, a 75μm light release film was laminated to obtain an integrated black OCA optical film.

[0067] The final product is a monolithic black OCA optical film containing carbon black, with a thickness of 50 μm and a film surface like... Figure 1 As shown: the film surface is uneven in color, with obvious horizontal and vertical lines, and there are tiny agglomerated particles (i.e., the carbon black is not evenly dispersed in the OCA adhesive).

[0068] Comparative Example 2

[0069] Weigh 0.3g of graphene powder, 0.5g of graphene dispersant and 99.2g of ethyl acetate, put them into a contact cell disruptor and ultrasonically disperse them for 2 hours at 200W power.

[0070] Subsequently, 20g of a 0.3wt% graphene ethyl acetate dispersion and 300g of OCA adhesive were weighed and stirred at 1000r / min for 0.5h to obtain an integrated black OCA adhesive. The integrated black OCA adhesive was then coated onto a 75μm heavy release film using a 250μm four-sided coater and cured in an oven at 80℃ for 2h. Finally, a 75μm light release film was laminated to obtain the final integrated black OCA optical film.

[0071] The final product was a monolithic black OCA optical film containing graphene, with a thickness of 50 μm. The film surface was uneven, and there were obvious agglomerated and precipitated particles (i.e., the carbon black was not evenly dispersed in the OCA adhesive).

[0072] Example 1

[0073] 0.3 g of graphene and 99.7 g of ethanol were ultrasonicated at 200 W for 1 h in a cell disruptor to obtain a 0.3 wt% graphene-ethanol dispersion. Subsequently, 60 g of the graphene-ethanol dispersion was sprayed onto a water surface the size of an A4 sheet of paper using a pneumatic spray gun. Under the Marangoni effect, the graphene formed a film of uniform thickness at the water-air interface.

[0074] A 25g solution of ethyl acetate with a concentration of 50wt% OCA adhesive was sprayed upwards at a 45° angle using a pneumatic spray gun (spraying is achieved pneumatically; direct spraying would damage the graphene composite carbon black layer. Upward spraying involves spraying the OCA adhesive solution upwards (generally at 10-45°) and then gently letting it fall onto the graphene film under gravity, thus avoiding damage to its surface structure). The resulting fine droplets gently fell onto the graphene film under gravity. The film was then transferred to an 80°C oven and left to stand for 10 minutes to allow the ethyl acetate to completely evaporate. Next, a 75μm thick release film was applied to the OCA adhesive layer, and the film was then flipped over and cured in the oven for 2 hours to obtain the lower OCA optical adhesive layer bonded to the graphene film. Next, 25g of OCA adhesive was applied to the other side of the graphene film using a 100μm coater and cured in a 60℃ oven for 2 hours to obtain the upper OCA optical adhesive layer. Finally, a 75μm thick light release film was laminated on the upper OCA optical adhesive layer to obtain the black OCA optical adhesive film.

[0075] The prepared black OCA optical film has a transmittance of 52%, a haze of 12%, CIE L: 55, a: -0.01, b: 2.10, and a total film thickness of 50 μm (excluding the release film). It consists of a 1 μm black graphene layer, a 26 μm upper OCA layer, and a 23 μm lower OCA layer. The film surface is uniform. Under an external 12V voltage, the temperature reaches 71.3℃ after 30 seconds.

[0076] Example 2

[0077] 0.3 g of carbon black powder and 99.7 g of ethanol were ultrasonicated at 200 W for 1 h in a cell disruptor to obtain a 0.3 wt% carbon black ethanol dispersion. Subsequently, 60 g of the carbon black ethanol dispersion was sprayed onto a water surface the size of an A4 sheet of paper using a pneumatic spray gun. Under the Marangoni effect, the carbon black formed a thin film of uniform thickness at the water-air interface.

[0078] A 25g solution of 50wt% OCA adhesive in ethyl acetate was sprayed upwards at a 45° angle using a pneumatic spray gun. The resulting fine droplets gently fell onto the carbon black film under gravity. The film was then transferred to an 80°C oven and left to stand for 10 minutes to allow the ethyl acetate to completely evaporate. Next, a 75μm thick heavy release film was applied to the OCA adhesive layer. The film was then flipped over and cured in an oven for 2 hours to obtain the lower OCA optical adhesive layer bonded to the carbon black film. Then, 25g of OCA adhesive was applied to the other side of the carbon black film using a 100μm coater and cured in a 60°C oven for 2 hours. Finally, a 75μm thick light release film was laminated onto the upper OCA optical adhesive layer to obtain the black OCA optical adhesive film.

[0079] The prepared black OCA optical film has a transmittance of 5%, a haze of 15%, a CIE L: 12, a: -0.11, b: -2.40, and a total film thickness of 50 μm (excluding the release film), consisting of a 5 μm carbon black layer, a 25 μm upper OCA layer, and a 20 μm lower OCA layer. The film surface is uniform. Under an external 12V voltage, the temperature reaches 42.1℃ after 30 seconds.

[0080] Example 3

[0081] 0.3g of graphene and carbon black powder (mass ratio 1:5) was added to ethanol (99.7g), totaling 100g. The mixture was ultrasonicated for 1 hour using a 200W contact cell disruptor. Subsequently, 60g of the graphene-carbon black ethanol dispersion was sprayed onto a water surface the size of an A4 sheet of paper using a spray gun. Under the Marangoni effect, the graphene and carbon black particles formed a uniform thin film (i.e., a black layer) at the water-air interface. Next, 25g of ethyl acetate solution of 50% OCA adhesive was sprayed upwards at 45° using a spray gun (spraying is achieved pneumatically; direct spraying would damage the graphene composite carbon black layer. Upward spraying involves spraying the OCA adhesive solution upwards (generally at 10-45°) and then gently letting it fall onto the graphene composite carbon black film under gravity, thus avoiding damage to its film structure). The fine droplets gently fell onto the graphene composite carbon black film under gravity, and then the film was transferred to an 80°C oven for 10 minutes to allow the ethyl acetate to completely evaporate. Then, a 75μm release film was attached to the OCA adhesive layer, and the film was flipped over and cured in the oven for 2 hours to obtain the OCA optical adhesive layer bonded to the graphene composite carbon black film. Next, using a 100μm thick coater, 25g of OCA adhesive was applied to the other side of the graphene composite carbon black film and cured at 60℃ for 2 hours. Finally, a 75μm thick light release film was laminated onto the OCA optical adhesive layer.

[0082] The cross-sectional structure of the prepared black OCA optical adhesive (also known as monolithic black OCA) is as follows: Figure 2As shown, the black OCA optical adhesive has a transmittance of 42%, a haze of 25%, a CIE L: 46, a: 0.05, b: 0.10, and a total film thickness of 50 μm, comprising a 5 μm graphene composite carbon black layer, a 25 μm upper OCA layer, and a 20 μm lower OCA layer. The film surface is uniform, without horizontal or vertical lines or uneven brightness. Under an external 12V voltage, the temperature reaches 65.4℃ after 30 seconds.

[0083] Example 4

[0084] 0.5 g of graphene and 99.7 g of ethanol were placed in a cell disruptor and sonicated at 200 W for 1 h to obtain a 0.5 wt% graphene-ethanol dispersion; 0.3 g of carbon black powder and 99.7 g of ethanol were placed in a cell disruptor and sonicated at 200 W for 1 h to obtain a 0.3 wt% carbon black-ethanol dispersion.

[0085] First, 30g of the graphene-ethanol dispersion was sprayed onto a water surface the size of an A4 sheet of paper using a spray gun. Under the Marangoni effect, a uniform graphene film was formed at the water-air interface. Then, 10g of the carbon black-ethanol dispersion was sprayed upwards using a spray gun, falling onto the same water surface (spraying onto the graphene film surface). Similarly, under the Marangoni effect, a uniform graphene composite carbon black film (i.e., a black layer) was formed at the water-air interface. Next, 15g of a 50% concentration of ethyl acetate solution of OCA adhesive was sprayed upwards at a 45° angle using a spray gun. The fine droplets gently fell onto the graphene composite carbon black film under gravity. Afterwards, it was transferred to an 80°C oven for 10 minutes to allow the ethyl acetate to completely evaporate. Then, a 75μm release film was attached to the OCA adhesive layer, and then it was turned over and cured in the oven for 2 hours to obtain a graphene composite carbon black film with an OCA optical adhesive layer. Next, using a 100μm thick coater, 15g of OCA adhesive was applied to the other side of the graphene composite carbon black film and cured at 60℃ for 2 hours. Finally, a 75μm thick light release film was laminated onto the OCA optical adhesive layer.

[0086] The prepared black OCA optical adhesive has a transmittance of 68%, a haze of 24%, CIE L: 56, a: -0.03, b: 1.59, and a total film thickness of 42 μm, consisting of a 5 μm graphene-carbon black layer, a 17 μm upper OCA layer, and a 20 μm lower OCA layer. The film surface is uniform. Under an external 12V voltage, the temperature reaches 63.3℃ after 30 seconds.

[0087] Example 5

[0088] 0.5 g of graphene and 99.7 g of ethanol were placed in a cell disruptor and sonicated at 200 W for 1 hour to obtain a 0.5 wt% graphene-ethanol dispersion. 1.0 g of carbon black powder and 99.0 g of ethanol were also placed in the same cell disruptor and sonicated at 200 W for 1 hour to obtain a 1.0 wt% carbon black-ethanol dispersion. The above 20 g of carbon black-ethanol dispersion was first sprayed onto a water surface the size of an A4 sheet of paper using a spray gun. Under the Marangoni effect, a uniform carbon black film was formed at the water-air interface. Then, the above 20 g of graphene-ethanol dispersion was sprayed upwards through the spray gun onto the same water surface, forming a uniform graphene composite carbon black film (i.e., a black layer) at the water-air interface.

[0089] Next, 15g of a 50% OCA adhesive solution in ethyl acetate was sprayed upwards at a 45° angle using a spray gun. The fine droplets gently fell onto the graphene composite carbon black film under gravity. The film was then transferred to an 80°C oven for 10 minutes to allow the ethyl acetate to completely evaporate. A 75μm thick heavy release film was then applied to the OCA adhesive layer, and the film was flipped over and cured in the oven for 2 hours, resulting in a lower OCA optical adhesive layer bonded to the graphene composite carbon black film. Next, 15g of OCA adhesive was applied to the other side of the graphene composite carbon black film using a 100μm thick coater and cured at 60°C for 2 hours. Finally, a 75μm thick light release film was laminated onto the upper OCA optical adhesive layer.

[0090] The prepared black OCA optical adhesive has a transmittance of 42%, a haze of 11%, a CIE L: 38, a: -0.04, b: 2.11, and a total film thickness of 40 μm, consisting of a 4 μm graphene-carbon black composite layer, a 15 μm upper OCA layer, and a 21 μm lower OCA layer. The film surface is uniform. Under an external 12V voltage, the temperature reaches 68.8℃ after 30 seconds.

[0091] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. All equivalent variations and modifications made based on the content of the present invention are covered within the patent scope of the present invention.

Claims

1. A black OCA optical adhesive, characterized in that, The black OCA optical adhesive comprises, from top to bottom, an upper OCA optical adhesive layer, a black layer, and a lower OCA optical adhesive layer; the black layer is a graphene composite carbon black layer; the graphene composite carbon black layer is composed of graphene and carbon black combined together.

2. The black OCA optical adhesive according to claim 1, characterized in that, The black OCA optical adhesive comprises, from top to bottom, a light release film, an upper OCA optical adhesive layer, a black layer, a lower OCA optical adhesive layer, and a heavy release film.

3. The black OCA optical adhesive according to claim 1, characterized in that, The graphene is dispersed in carbon black.

4. The black OCA optical adhesive according to claim 1, characterized in that, The upper and lower OCA optical adhesive layers are formed of acrylate adhesive, which contains 100-500 parts of acrylic polyol, 0.3-3.0 parts of toluene diisocyanate curing agent, 0.03-0.5 parts of bismuth salt catalyst, 0.2-2.0 parts of siloxane coupling agent, and 10-100 parts of ethyl acetate; the parts are by weight.

5. The black OCA optical adhesive according to claim 1 or 2, characterized in that, The black layer is both light-transmitting and conductive.

6. A method for preparing the black OCA optical adhesive according to claim 3, characterized in that, The method includes the following steps: Step 1: Disperse graphene and carbon black in ethanol, and then spray the ethanol dispersion of graphene composite carbon black onto the water surface through a spray gun to form a thin film of graphene composite carbon black on the water surface. Step 2: Spray the ethyl acetate solution of OCA adhesive upwards through a spray gun onto the graphene composite carbon black film, heat it to evaporate the ethyl acetate, and cure it into the lower OCA optical adhesive layer; Step 3: Apply OCA adhesive to the other side of the graphene composite carbon black film and then cure it to form an upper OCA optical adhesive layer.

7. A method for preparing the black OCA optical adhesive according to claim 1, characterized in that, The method includes the following steps: Step 1: Disperse graphene and carbon black in ethanol; spray the graphene ethanol dispersion onto the water surface through a spray gun to form a graphene film on the water surface; then spray the carbon black ethanol dispersion upward through a spray gun onto the graphene film on the water surface to form a graphene composite carbon black film. Alternatively, carbon black and graphene can be dispersed in ethanol; the carbon black ethanol dispersion can be sprayed onto the water surface through a spray gun to form a carbon black film on the water surface; then the graphene ethanol dispersion can be sprayed upward through a spray gun and fall onto the carbon black film on the water surface to form a graphene composite carbon black film. Step 2: Spray the ethyl acetate solution of OCA adhesive upwards through a spray gun onto the graphene composite carbon black film, heat it to evaporate the ethyl acetate, and cure it into the lower OCA optical adhesive layer; Step 3: Apply OCA adhesive to the other side of the graphene composite carbon black film and then cure it to form an upper OCA optical adhesive layer.

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