Coating, composite brightening film and method for preparing the same

Abstract

The application discloses a coating, a composite brightening film and a preparation method thereof, and belongs to the field of high polymer materials. The coating comprises the following components in parts by weight: photocuring resin 30-60 parts, monofunctional photocuring monomer 30-60 parts, multifunctional photocuring monomer 2-10 parts and photoinitiator 1-10 parts, wherein the functionality of the multifunctional photocuring monomer is 3-6. The adhesive layer obtained from the coating has high peeling force, high temperature and humidity resistance, high brightness, is not prone to warping and adhesive opening after being attached, and the like, and the adhesive layer is suitable for preparing a composite brightening film, and can effectively improve the structural stability of the composite brightening film and make the composite brightening film maintain excellent brightening effect.

Description

Technical Field

[0001] This invention relates to the field of polymer materials, and particularly to coatings, composite brightening films, and their preparation methods. Background Technology

[0002] Brightness enhancement films with prismatic microstructures (also known as prism sheets, light-concentrating sheets, etc.) can concentrate light from different emission directions on the front to improve illumination brightness and uniformity. Brightness enhancement films can be used in display devices such as LCD displays.

[0003] To ensure that light is concentrated as much as possible in front, multiple brightness enhancement films are usually combined into composite brightness enhancement films. Common types of composite brightness enhancement films include DOP, MOP and POP.

[0004] However, all of the above types of composite brightening films involve bonding the adhesive layer and the prism structure layer, which results in at least the following technical problems: low peel strength, low brightness, large shrinkage after bonding, severe warping, and easy delamination at the edges. Summary of the Invention

[0005] In view of this, the present invention provides coatings, composite brightening films, and methods for preparing the same, which can solve the above-mentioned technical problems. Specifically, it includes the following technical solutions:

[0006] On one hand, a coating is provided, the coating comprising the following components in parts by weight: 30-60 parts of a photocurable resin, 30-60 parts of a monofunctional photocurable monomer, 2-10 parts of a multifunctional photocurable monomer, and 1-10 parts of a photoinitiator, wherein the functionality of the multifunctional photocurable monomer is 3-6.

[0007] In some possible implementations, the monofunctional photocurable monomer is selected from at least one of the following monomers:

[0008] Acryloylmorpholine, isobornyl acrylate, 2-phenoxyethyl acrylate, (2-ethoxy)phenoxy acrylate, isobornyl methacrylate, tetrahydrofuran acrylate, N,N-dimethylacrylamide, hydroxyethyl acrylate, hydroxypropyl acrylate.

[0009] In some possible implementations, the monofunctional photocurable monomer is selected from at least one of the following monomers: (2-ethoxy)phenoxy acrylate, tetrahydrofuran acrylate, hydroxyethyl acrylate, isobornyl methacrylate, and hydroxypropyl acrylate; the multifunctional photocurable monomer has a functionality of 5-6; or,

[0010] The monofunctional photocurable monomer is selected from at least one of the following monomers: acrylomorpholine, isobornyl acrylate, 2-phenoxyethyl acrylate, N,N-dimethylacrylamide; the multifunctional photocurable monomer has a functionality of 3-4.

[0011] In some possible implementations, the multifunctional photocurable monomer is selected from at least one of the following monomers: trimethylolpropane triacrylate, pentaerythritol triacrylate, (3-propoxy)trimethylolpropane triacrylate, pentaerythritol tetraacrylate, and dipentaerythritol hexaacrylate.

[0012] In some possible implementations, the photocurable resin is selected from at least one of polyurethane acrylate resin, polyester acrylate resin, polycarbonate acrylate resin, and epoxy acrylate resin.

[0013] In some possible implementations, the photocurable resin is selected from at least one of polyurethane acrylate resin and polycarbonate acrylate resin, and the functionality of the photocurable resin is 2-3.

[0014] In some possible implementations, the photoinitiator is an α-hydroxyalkylone photoinitiator and / or an acyl oxide photoinitiator; and / or,

[0015] The coating also includes initiators and additives.

[0016] On the other hand, the application of any of the above-mentioned coatings in composite brightening films is provided.

[0017] On another front, a composite brightening film is provided, the composite brightening film comprising: a lower substrate layer, a lower prism structure layer, an adhesive layer and an upper substrate layer stacked sequentially from bottom to top;

[0018] The adhesive layer is prepared using any of the coatings described above.

[0019] In some possible implementations, the upper substrate layer also has an upper prism structure layer on the surface opposite to the adhesive layer.

[0020] Furthermore, a method for preparing a composite brightness enhancement film is provided, the method comprising:

[0021] A first composite layer is provided, the first composite layer comprising a lower substrate layer and a lower prism structure layer formed on the lower substrate layer;

[0022] A second composite layer is provided, the second composite layer comprising an upper substrate layer and an adhesive layer coated on the upper substrate layer, wherein the adhesive layer is prepared using the coating according to any one of claims 1-7;

[0023] The first composite layer and the second composite layer are bonded together and then cured to obtain the composite brightening film, wherein the bonding adhesive layer is bonded to the upper surface of the lower prism structure layer.

[0024] In some possible implementations, the method for preparing the composite brightness enhancement film further includes:

[0025] An upper prism coating and an upper prism structure template are provided. Based on the upper prism structure template, the upper prism coating located on the upper substrate layer is subjected to photocuring treatment to obtain an upper prism structure layer.

[0026] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following:

[0027] The coating provided in this invention can be used to prepare an adhesive layer. Based on the synergistic effect of the above components, the adhesive layer obtained by the coating has the advantages of high peel strength, high temperature and humidity resistance, high brightness, and is not easy to warp or delaminate after bonding. The adhesive layer is suitable as an adhesive layer for composite brightness enhancement films, which can effectively improve the structural stability of composite brightness enhancement films and maintain their excellent brightness enhancement effect. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of an exemplary composite brightening film provided in an embodiment of the present invention;

[0030] Figure 2 This is a schematic diagram of another exemplary composite brightening film provided in an embodiment of the present invention.

[0031] The reference numerals in the attached figures represent:

[0032] 1-Lower substrate layer; 2-Lower prism structure layer; 3-Adhesive layer;

[0033] 4-Upper basal layer; 5-Upper prism structure layer. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] The directional terms used in the embodiments of this invention, such as "up" and "down", are generally in the form of... Figure 1 The relative positions shown are based on the given information, and these directional terms are used only to more clearly describe the relationships between structures, not to describe absolute positions. Positions may change when the product is placed in different orientations; for example, "up" and "down" may be interchanged.

[0036] In this invention, the term "luminance" refers to the light intensity per unit projection area. The unit is candela per plane (cd / m²). 2 ).

[0037] Luminance indicates the brightness of a light source, also known as luminance. Luminance is inversely proportional to the luminous area and directly proportional to the intensity of the light source. When the light intensity from a given light source is the same, the larger its luminous area, the smaller its luminance; conversely, when the luminous area is the same, the greater the light intensity, the greater the luminance.

[0038] To make the technical solutions and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0039] Currently, the composite brightening films provided by related technologies have at least the following technical problems: low peel strength, low brightness, large shrinkage after lamination, severe warping, and easy delamination at the edges.

[0040] To address the technical problems existing in related technologies, embodiments of the present invention provide a coating comprising the following components in parts by weight: 30-60 parts of photocurable resin, 30-60 parts of monofunctional photocurable monomer, 2-10 parts of multifunctional photocurable monomer, and 1-5 parts of photoinitiator, wherein the functionality of the multifunctional photocurable monomer is 3-6.

[0041] The coating provided in this invention can be used to prepare an adhesive layer. Based on the synergistic effect of the above components, the adhesive layer obtained by the coating has the advantages of high peel strength, high temperature and humidity resistance, high brightness, and is not easy to warp or delaminate after bonding. The adhesive layer is suitable for bonding with the lower prism structure layer in a composite brightness enhancement film, which can effectively improve the structural stability of the composite brightness enhancement film and maintain its excellent brightness enhancement effect.

[0042] In some implementations, embodiments of the present invention also provide a coating having a preferred formulation, the coating comprising the following components in parts by weight: 45-60 parts of a photocurable resin, 30-45 parts of a monofunctional photocurable monomer, 3-8 parts of a multifunctional photocurable monomer, and 3-6 parts of a photoinitiator.

[0043] The weight parts of the UV-curable resin in the coating include, but are not limited to: 30 parts, 35 parts, 40 parts, 45 parts, 46 parts, 47 parts, 48 ​​parts, 49 parts, 50 parts, 51 parts, 52 parts, 53 parts, 54 parts, 55 parts, 60 parts, etc.

[0044] The weight parts of monofunctional photocurable monomers in coatings include, but are not limited to: 30 parts, 35 parts, 40 parts, 41 parts, 42 parts, 43 parts, 44 parts, 45 parts, 50 parts, 55 parts, 60 parts, etc.

[0045] The weight parts of multifunctional photocurable monomers in coatings include, but are not limited to: 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, etc.

[0046] The weight parts of photoinitiator in the coating include, but are not limited to: 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, 5.5 parts, 6 parts, 6.5 parts, etc.

[0047] In some implementations, the photocurable resin is selected from at least one of polyurethane acrylate resin, polyester acrylate resin, polycarbonate acrylate resin, and epoxy acrylate resin.

[0048] As an example, the light-curing resin is at least one of polyurethane acrylate resin and polycarbonate acrylate resin.

[0049] Taking polyurethane acrylate resin as an example, the polyurethane acrylate resin may be selected from at least one of polyurethane acrylate and polyester-type polyurethane acrylate.

[0050] By using the aforementioned types of photocurable resins and limiting their weight proportions in the coating as described above, it is possible not only to ensure that the coating has a faster curing speed, thereby increasing the degree of reaction under the same energy conditions and correspondingly increasing the peel strength and gloss, but also to inhibit the curing shrinkage of the coating caused by the coating and prevent warping.

[0051] In some examples, the functionality of the light-curing resin is 2-3. Taking polyurethane acrylate as an example, its functionality is 2-3. The ratio of the molar amount of trifunctional groups to the molar amount of difunctional groups is less than or equal to 10%. This is because if the amount of trifunctional groups is too high, it will lead to large curing shrinkage and large warping.

[0052] For polyester-based polyurethane acrylates, for example, compared to polyether-based polyurethane acrylates, they have better tensile strength and modulus, resulting in better flexibility. Good flexibility and tensile strength can ensure that the adhesive layer has greater peel force.

[0053] In some implementations, the monofunctional photocurable monomer contains at least one of a cyclic structure, a hydroxyl group, or an amine structure, wherein the cyclic structure includes, but is not limited to, benzene rings, aliphatic rings, or bridged rings.

[0054] In some examples, the monofunctional photocurable monomer contains zero or one ring structure. For example, the monofunctional photocurable monomer includes a benzene ring, and the number of benzene rings is one, in order to prevent increased curing shrinkage and thus prevent warping.

[0055] In some implementations, the monofunctional photocurable monomer is selected from at least one of the following monomers: acrylamide morpholine (ACMO), isobornyl acrylate (IBOA), 2-phenoxyethyl acrylate (PHEA), (2-ethoxy)phenoxy acrylate (PH(EO)2A), isobornyl methacrylate (IBOMA), tetrahydrofuran acrylate (THFA), N,N-dimethylacrylamide (DMAA), hydroxyethyl acrylate (HEA), hydroxypropyl acrylate (HPA), and o-phenylphenoxyethyl acrylate (OPPEA). Among these, (2-ethoxy)phenoxy acrylate can also be referred to as (2-ethoxy)phenolic acrylate.

[0056] By using the aforementioned monofunctional photocurable monomers and limiting their weight proportions in the coating as described above, it is possible not only to ensure that the coating system has moderate viscosity and fluidity for easy application and to obtain a suitable bonding width, but also to enhance the coating's gloss and ensure a high degree of curing during curing to prevent delamination and ensure that the adhesive layer maintains stable peel strength in high temperature and high humidity environments.

[0057] Some preferred monofunctional photocurable monomers are at least one of the following monomers: acrylamide morpholine (ACMO), isobornyl acrylate (IBOA), 2-phenoxyethyl acrylate (PHEA), and tetrahydrofuran acrylate (THFA).

[0058] In some implementations, the monofunctional photocurable monomer is selected from at least one of the following monomers: (2-ethoxy)phenoxy acrylate, tetrahydrofuran acrylate, hydroxyethyl acrylate, isobornyl methacrylate, hydroxypropyl acrylate, and the multifunctional photocurable monomer has a functionality of 5-6.

[0059] In this implementation, the weight parts of the monofunctional photocurable monomer are 30-45 parts, and the weight parts of the multifunctional photocurable monomer with a functionality of 5-6 are 3-8 parts.

[0060] The reaction rate of the aforementioned monofunctional photocurable monomers is relatively slow, so the functionality of multifunctional photocurable monomers is 5-6 to ensure a faster reaction rate. By combining the aforementioned monofunctional photocurable monomers with multifunctional photocurable monomers of 5-6 functionality, a suitable crosslinking density can be obtained and the curing shrinkage can be balanced. This ensures stable peel strength under high temperature and high humidity conditions, while preventing warping and delamination.

[0061] In other implementations, the monofunctional photocurable monomer is selected from at least one of the following monomers: acrylomorpholine, isobornyl acrylate, 2-phenoxyethyl acrylate, N,N-dimethylacrylamide; and the multifunctional photocurable monomer has a functionality of 3-4.

[0062] For example, the amount of monofunctional photocurable monomer used is 30-45 parts, and the amount of multifunctional photocurable monomer with a functionality of 3-4 used is 3-8 parts.

[0063] The aforementioned monofunctional photocurable monomers have relatively fast reaction rates, while multifunctional photocurable monomers have a functionality of 3-4 to prevent excessive warpage and delamination, while also maintaining a high reaction rate. By combining the aforementioned monofunctional photocurable monomers with multifunctional photocurable monomers of 3-4 functionality, a suitable crosslinking density can be obtained and curing shrinkage balanced. This ensures stable peel strength under high temperature and humidity conditions while preventing warpage and delamination. In particular, this combination also facilitates achieving a higher reaction rate.

[0064] In some examples, the multifunctional photocurable monomer is selected from at least one of the following monomers: trimethylolpropane triacrylate (TMPTA), pentaerythritol triacrylate (PET3A), (3-propoxy)trimethylolpropane triacrylate (TMPT3POA), pentaerythritol tetraacrylate (PET4A), and dipentaerythritol hexaacrylate (DPHA).

[0065] By selecting the aforementioned types of multifunctional photocurable monomers and limiting their weight proportions in the coating as described above, the coating exhibits characteristics of rapid reaction, complete curing, and high crosslinking density. It is understood that a suitable crosslinking density ensures the stability of the cured adhesive layer, prevents the peel strength of the adhesive layer from decreasing under high temperature and humidity conditions, helps reduce curing shrinkage of the adhesive layer, and avoids warping and delamination.

[0066] In some implementations, the photoinitiator is an α-hydroxyalkyl ketone photoinitiator and / or an acyl oxide photoinitiator.

[0067] For α-hydroxyalkyl ketone photoinitiators, such as but not limited to photoinitiator 184, photoinitiator 1173, photoinitiator 2959, etc.

[0068] For acyl oxide initiators, such as including but not limited to photoinitiator TPO, photoinitiator BPO, photoinitiator CP-02, photoinitiator 819, etc.

[0069] In some examples, the photoinitiator is a mixture of α-hydroxyalkanone photoinitiators and acyl oxide photoinitiators, wherein the mass ratio of the α-hydroxyalkanone photoinitiator to the acyl oxide photoinitiator is (1-1.5):(1-2.5), for example, 1:1, 1:1.5, 1:1.7, 1:1.8, 1:1.9, 1:2, 1:2.5, etc. By limiting the type and proportion of photoinitiators, the coating can achieve a suitable curing speed and also improve peel strength.

[0070] When the adhesive coating thickness is low (<3μm) and there are gaps between the adhesive layer and the lower prism structure layer, oxygen can be present in these gaps, leading to oxygen inhibition of polymerization. In some implementations, the coating provided in this invention also includes a co-initiator, which can reduce the effect of oxygen inhibition of polymerization to ensure curing effect.

[0071] For example, the co-initiator is a reactive amine co-initiator, such as CN371NS. The reactive amine co-initiator is present in the coating at a weight of 0.1 to 5 parts, for example, 0.1 to 3 parts.

[0072] In this embodiment of the invention, by using photoinitiators and co-initiators in a reasonable combination, both surface curing and deep curing can be achieved, the influence of oxygen inhibition can be reduced, a better curing effect can be achieved, the peel strength of the coating can be guaranteed, and the attenuation of the peel strength of the coating in high temperature and high humidity environments can be reduced.

[0073] In some examples, the coatings provided in embodiments of the present invention further include 0.01-1 parts by weight of an additive that improves the wettability and leveling properties of the coating.

[0074] The additives in the coating are 0.01 to 1 part by weight, including but not limited to: 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, etc.

[0075] In some examples, the additives are silicone wetting agents and / or leveling agents.

[0076] Organosilicon wetting aids include, but are not limited to, at least one of the following aids: BYK-306, BYK-3505, TEGO100, TEGO 110, TEGO 410, TEGO 270, etc.

[0077] By using the aforementioned low-migration silicone wetting aids, the surface tension and wettability of the coating can be improved, ensuring the integrity of the prism structure. In particular, the selection of the aforementioned reactive silicone wetting aids can, to a certain extent, inhibit the migration of the aids, which not only ensures the adhesion of the adhesive layer but also facilitates obtaining greater peel strength.

[0078] On the other hand, embodiments of the present invention also provide the application of any of the above-described coatings in composite brightening films.

[0079] The coating provided in this invention can be used in composite brightening films. As an adhesive layer, it is bonded to the lower prism structure layer in the composite brightening film, so that the composite brightening film has the advantages of excellent peel strength, high temperature and high humidity resistance, high brightness, and is not easy to shrink or delaminate after bonding.

[0080] Furthermore, embodiments of the present invention also provide a composite brightening film, as shown in the attached figure. Figure 1 As shown, the composite brightening film includes: a lower base layer 1, a lower prism structure layer 2, an adhesive layer 3, and an upper base layer 4, which are stacked sequentially from bottom to top; wherein the adhesive layer 3 is prepared from any of the coatings described above.

[0081] The composite brightening film provided in this embodiment of the invention has an adhesive layer 3 prepared from the above-mentioned coating, which makes the composite brightening film have excellent peel strength, high temperature and high humidity resistance, high brightness, and is not easy to shrink or delaminate after lamination, thus ensuring the brightening effect and structural stability of the composite brightening film.

[0082] In some examples, the materials of the lower substrate 1 and the upper substrate 4 include, but are not limited to, polyethylene terephthalate (PET).

[0083] In some examples, the lower prism structure layer 2 is prepared by wrapping the coating in a structure roller with a base layer, such as a PET film (e.g., semi-wrapping), and simultaneously irradiating it with UV light to cure it. After release, a lower prism structure layer with a prism structure is obtained. Subsequently, the pre-cured lower prism structure layer is bonded to the adhesive layer, and then UV light is irradiated from the lower prism surface for a second curing process to obtain a fully cured lower prism structure layer 2.

[0084] In some examples, the thickness of the lower prism structure layer 2 in the composite brightness enhancement film can be 25μm-40μm, such as 25μm, 26μm, 27μm, 28μm, 29μm, 30μm, 31μm, 32μm, 33μm, 34μm, 35μm, 36μm, 37μm, 38μm, 39μm, 40μm, etc.

[0085] In some examples, the thickness of the adhesive layer 3 in the composite brightening film can be 2μm-3μm, such as 2μm, 2.1μm, 2.2μm, 2.3μm, 2.4μm, 2.5μm, 2.6μm, 2.7μm, 2.8μm, 2.9μm, 3μm, etc., which helps the coating to have both excellent peel strength and brightness.

[0086] For the prism structure set on the lower prism structure layer 2, its structural parameters include, but are not limited to, the following: apex angle 89°-91°, height 30μm-40μm, and pich 50μm-70μm. Here, pich refers to the spacing between any two adjacent structural units in the lower prism structure.

[0087] In some examples, the bonding width of the lower prism structure layer 2 in the composite brightness enhancement film is 3μm-10μm. Here, the bonding width of the lower prism structure layer 2 refers to the fact that after the lower prism structure layer 2 is bonded to the adhesive layer 3, the apex corner of each structural unit in the lower prism structure is lost, resulting in a trapezoidal cross-sectional shape for each structural unit in the lower prism structure. Therefore, the length of the upper side of this trapezoid is the bonding width of the lower prism structure layer 2.

[0088] The method for measuring the bonding width of the lower prism structure layer 2 is as follows: Separate the lower prism structure layer 2 from the adhesive layer 3 in the composite brightening film, observe the top surface of the lower prism structure layer 2 with a 3D microscope, and measure its bonding width.

[0089] By making the bonding width of the lower prism structure layer 2 3μm-10μm, it is possible to achieve both excellent peel strength and brightness.

[0090] In some examples, such as the attached Figure 2 As shown, the upper substrate layer 4 also has an upper prism structure layer 5 on its surface opposite to the adhesive layer 3. That is, the composite brightening film includes: a lower substrate layer 1, a lower prism structure layer 2, an adhesive layer 3, an upper substrate layer 4, and an upper prism structure layer 5 stacked sequentially from bottom to top.

[0091] For example, the upper prism structure of the upper prism structure layer 5 can be a microlens structure, and each structural unit contained in the microlens structure is hemispherical in shape. Multiple structural units of the hemispherical structure are arranged closely at fixed points in an equilateral hexagon. Its diameter is equal to the side length of the equilateral hexagon.

[0092] On the other hand, embodiments of the present invention also provide a method for preparing a composite brightness enhancement film, wherein the composite brightness enhancement film is as described above. The method for preparing the composite brightness enhancement film includes:

[0093] A first composite layer is provided, comprising a lower substrate layer and a lower prism structure layer formed on the lower substrate layer. Understandably, the lower prism structure layer in the first composite layer has only undergone preliminary curing.

[0094] A second composite layer is provided, comprising an upper substrate layer and an adhesive layer coated on the upper substrate layer. The adhesive layer is prepared using any of the aforementioned coatings, and the adhesive layer in the second composite layer undergoes only simple baking and curing.

[0095] The first and second composite layers are bonded together and then cured to obtain a composite brightening film, wherein the adhesive layer is bonded to the lower prism structure layer. During this process, the initially cured lower prism structure layer undergoes a second curing, and the baked-cured adhesive layer undergoes further curing.

[0096] In this context, the curing process of the coating during the preparation of the first composite layer is defined as the initial curing, and the curing process of the lower prism structure layer after the first and second composite layers are bonded together is defined as the secondary curing.

[0097] For the initial curing process, the UVA energy used can be 30 mJ / cm². 2 -80mj / cm 2 Furthermore, for the secondary curing process, the UVA energy used can be 800 mJ / cm². 2 -1200mj / cm 2 In order to achieve their respective desired level of solidification.

[0098] For the first composite layer, the coating is wrapped in a structural roller using a base layer, such as a PET film, and then cured by UV light. After release, the first composite layer is obtained.

[0099] The preparation steps for the second composite layer are as follows: First, dilute the adhesive to a solid content of 15-30% with a suitable solvent (including but not limited to ethyl acetate, butyl acetate, butanone, and toluene), and stir until homogeneous to obtain a uniform adhesive solution. Second, coat the adhesive solution onto the upper substrate layer and bake at 50℃-110℃ until the solvent completely evaporates to form the second composite layer.

[0100] After the first and second composite layers are bonded together, UVA is irradiated by the lower prism surface to achieve complete curing of the lower prism structure layer.

[0101] In some examples, when stirring the components in the coating, the stirring speed can be 500 rpm to 2000 rpm and / or the stirring time can be 30 min to 120 min to ensure that the components in the coating are fully and evenly mixed.

[0102] Furthermore, the well-stirred coating can be filtered and purified to ensure that the coating has a fine and uniform texture. For example, the filtration operation includes filtering the well-stirred coating through a filter bag with a pore size of 1 micrometer.

[0103] For the second composite layer, the adhesive layer is coated on the upper substrate using a microgravure coating method. The microgravure roller has a mesh size of 150-200 mesh.

[0104] The coating corresponding to the adhesive layer is diluted with a diluent during use. The solid content of the diluted adhesive coating is 15%-20%, such as 15%, 16%, 17%, 18%, 19%, 20%, etc., to obtain a good coating effect.

[0105] The diluents used for bonding adhesive coatings include, but are not limited to, at least one of ethyl acetate, butyl acetate, butanone, acetone, toluene, and cyclohexanone.

[0106] In some examples, after the adhesive coating is applied to the upper substrate, the diluent solvent can be evaporated through a drying tunnel, where the tunnel length can be 10m-30m and the tunnel temperature can be 50℃-110℃.

[0107] In some implementations, the method for preparing the composite brightening film involved in the embodiments of the present invention further includes: providing an upper cooling coating and an upper prism structure template, and performing photocuring treatment on the upper prism coating located on the upper substrate layer based on the upper prism structure template to obtain an upper prism structure layer.

[0108] The upper prism structure on the upper prism structure layer can be a microlens structure, which can be prepared by UV imprinting using a microlens structure template.

[0109] The imprinting process involved in the fabrication of microlens structures includes medium- and low-pressure UV imprinting and medium- and high-pressure curing.

[0110] The low-to-medium pressure UV embossing process includes: UV embossing on an upper substrate layer using an upper prism coating and a microlens structural template, followed by a release treatment to remove the microlens structural template. The UVA energy used in this low-to-medium pressure UV embossing process can be 30 mJ / cm². 2 -150mj / cm 2 .

[0111] Medium- and high-pressure curing includes: irradiating the surface on the side containing the microlens structure with 300 mJ / cm². 2 -500mj / cm 2 The UVA energy allows the coating on the upper prism to fully cure after molding.

[0112] Preferred embodiments of the present invention will now be described in more detail. While preferred embodiments of the present invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products. In the following embodiments, unless otherwise specified, "%" refers to weight percentage.

[0113] (1) The polyurethane acrylate resin involved in the following embodiments was purchased from Guangzhou Songda New Material Technology Co., Ltd., model number SD871; the polycarbonate acrylate resin involved was purchased from Wuxing Material Technology Co., Ltd., model number W2526B.

[0114] (2) Based on the following embodiments and comparative examples, performance tests were conducted on each type of coating. The specific test parameters and test methods are shown below.

[0115] (2.1) Glow: Different adhesive layers corresponding to different coatings are bonded together with the same lower prism structure layer to obtain a bonded diaphragm sample. The relative glow ratio of the diaphragm sample to the standard diaphragm is measured. A relative glow ratio ≥115% is considered qualified, and a relative glow ratio ≥118% is considered excellent.

[0116] (2.2) Curing degree: The coating is applied to the glass plate to form a coating layer, and a release film is covered on the coating layer. The curing degree is then determined by passing a curing test at 1000 mJ / cm². 2 The coating is cured completely using UVA energy (equivalent to the initial curing mentioned above), then the release film is peeled off, and the cured coating is removed from the glass plate. The infrared spectra of the coating and the coating layer are measured using an infrared spectrometer, and the ratio of the carbon-carbon double bond peak area to the carbonyl peak area is calculated to obtain the degree of curing, which represents the extent of reaction.

[0117] Degree of curing refers to (the ratio of carbon-carbon double bond area to carbonyl peak area in the coating before curing - the ratio of carbon-carbon double bond area to carbonyl peak area in the coating after curing) / the ratio of carbon-carbon double bond area to carbonyl peak area in the coating before curing * 100%.

[0118] (2.3) Warpage Degree: Composite brightening films were prepared separately using each coating as an adhesive layer, with all other layers in the composite brightening film maintaining consistency. The composite brightening film was cut to A3 size and laid flat on a horizontal table. The height of the four corners of the composite brightening film from the horizontal table was measured with a ruler, and the average value was taken. Warpage ≤3mm was considered acceptable, and warpage ≤1.5mm was considered excellent.

[0119] (2.4) Peel strength: Different adhesive layers corresponding to different coatings are bonded together with the same lower prism structure layer to obtain bonded diaphragm samples. The diaphragm samples are cut to a width of 25 mm, and the 90° peel strength is measured. A 90° peel strength ≥ 250 gf is considered qualified, and a 90° peel strength ≥ 300 gf is considered excellent.

[0120] (2.5) High Temperature and High Humidity Peel Strength: The laminated membrane sample was obtained using the same method as in (2.4). The membrane sample was placed in a high temperature and high humidity chamber at 85℃ and 85% humidity for 7 × 24 hours (7 days). After removal and restoration to room temperature, it was cut to a width of 25mm, and the 90° peel strength was measured. The ratio of the reduced peel strength after high temperature and high humidity to the original peel strength is the high temperature and high humidity peel strength attenuation. Attenuation < 50% is acceptable, and attenuation < 30% is excellent.

[0121] Examples 1-13

[0122] This invention provides Examples 1-13 and Comparative Examples 1-3 to provide a coating. The coating formulations for Examples 1-3 and Comparative Examples 1-3 are shown in Table 1-1, the coating formulations for Examples 4-7 are shown in Table 2-1, and the coating formulations for Examples 8-13 are shown in Table 3-1. All data in Tables 1-1, 2-1, and 3-1 are parts by weight, and the " / " indicates that the item is 0. Details are as follows:

[0123] Table 1-1

[0124]

[0125] Table 2-1

[0126]

[0127] Table 3-1

[0128]

[0129] Performance tests were conducted on the coatings provided in Examples 1-13 and Comparative Examples 1-3. The performance test results of Examples 1-3 and Comparative Examples 1-3 are shown in Table 1-2, the performance test results of Examples 4-7 are shown in Table 2-2, and the performance test results of Examples 8-13 are shown in Table 3-2.

[0130] Table 1-2

[0131]

[0132] Table 2-2

[0133] Brightness / % 119.7 118.6 117.8 120.0 Warp / mm 1.5 1.0 0.5 3.0 Peel force / gf 317.0 301.0 282.0 251.0 degree of reaction / % 86 83 74 87 High temperature and high humidity attenuation / % 26 29 39 25

[0134] Table 3-2

[0135]

[0136] As can be seen from the tables above, when the coating provided in the embodiments of the present invention is used as an adhesive layer for composite brightening film, the composite brightening film can simultaneously meet various advantages such as brightness ≥115%, peel force ≥250gf, warpage ≤3mm, and peel force attenuation rate <50% under high temperature and high humidity. In fact, under some preferred conditions, it can simultaneously meet the following requirements: brightness ≥118%, peel force ≥300gf, warpage ≤1.5mm, and peel force attenuation rate <50% under high temperature and high humidity.

[0137] In embodiments of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The term "multiple" refers to two or more unless otherwise expressly defined.

[0138] The above description is merely for the purpose of enabling those skilled in the art to understand the technical solutions of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A composite brightness enhancement film, characterized by, The composite brightening film comprises, from bottom to top, a lower base layer, a lower prism structure layer, an adhesive layer, and an upper base layer; The adhesive layer is prepared using a coating, which comprises the following components in parts by weight: 30-60 parts of photocurable resin, 30-60 parts of monofunctional photocurable monomer, 2-10 parts of multifunctional photocurable monomer, and 1-10 parts of photoinitiator, wherein the functionality of the multifunctional photocurable monomer is 3-6. The monofunctional photocurable monomer is selected from at least one of the following monomers: (2-ethoxy)phenoxyacrylate, tetrahydrofuran acrylate, hydroxyethyl acrylate, isobornyl methacrylate, hydroxypropyl acrylate, and 2-phenoxyethyl acrylate; and the polyfunctional photocurable monomer is dipentaerythritol hexaacrylate; or... The monofunctional photocurable monomer is selected from at least one of the following monomers: acrylmorpholine, isobornyl acrylate, 2-phenoxyethyl acrylate, tetrahydrofuran acrylate; and the polyfunctional photocurable monomer is selected from at least one of the following monomers: trimethylolpropane triacrylate, pentaerythritol triacrylate, (3-propoxy)trimethylolpropane triacrylate, pentaerythritol tetraacrylate. The photoinitiator is an α-hydroxyalkylone photoinitiator and / or an acyl oxide photoinitiator; The photocurable resin is selected from at least one of polyurethane acrylate resin and polycarbonate acrylate resin, and the functionality of the photocurable resin is 2-3.

2. The composite brightness enhancement film of claim 1, wherein, The coating also includes initiators and additives.

3. The composite brightness enhancement film of claim 1, wherein, The upper base layer also has an upper prism structure layer on the surface opposite to the adhesive layer.

4. A method for preparing a composite brightening film, characterized in that, The composite brightening film is as described in any one of claims 1-3, and the method for preparing the composite brightening film includes: A first composite layer is provided, the first composite layer comprising a lower substrate layer and a lower prism structure layer formed on the lower substrate layer; A second composite layer is provided, the second composite layer comprising an upper substrate layer and an adhesive layer coated on the upper substrate layer; The first composite layer and the second composite layer are bonded together and then cured to obtain the composite brightening film, wherein the bonding adhesive layer is bonded to the upper surface of the lower prism structure layer.

5. The method for preparing the composite brightening film according to claim 4, characterized in that, The method for preparing the composite brightening film further includes: An upper prism coating and an upper prism structure template are provided. Based on the upper prism structure template, the upper prism coating located on the upper substrate layer is subjected to photocuring treatment to obtain an upper prism structure layer.

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