Optical adhesive, curved surface bonding structure and application of optical adhesive in curved surface bonding structure

Abstract

The present application relates to an optical adhesive, a curved surface bonding structure and the application of the optical adhesive in the curved surface bonding structure, wherein the optical adhesive comprises 20 to 45 parts of polyurethane acrylate, 20 to 45 parts of methyl methacrylate, 20 to 35 parts of butyl acrylate, 3 to 3.5 parts of epoxy acrylate, 2.7 to 4.6 parts of reactive monomers, 0.5 to 1 part of photoinitiator and 0.1 to 0.2 parts of antioxidant. No high-temperature bonding is required, which avoids deformation of the optical film due to high temperature, thereby ensuring the product yield, and also avoids the equipment working at an excessively high temperature, which leads to an increase in the loss rate, and the relatively high-temperature process reduces the production time and reduces the production cost; the low-frequency modulation transfer function index is guaranteed, so it has better contrast, resolution and field of view, and has better performance in optical indicators such as surface waviness, local curvature error, color uniformity, light transmittance and astigmatism, ensuring the display effect.

Description

Technical Field

[0001] The present application relates to the field of optical adhesives, and in particular to optical adhesives, curved surface bonding structures, and applications of optical adhesives in curved surface bonding structures. Background Art

[0002] Augmented Reality (AR) and Virtual Reality (VR) are referred to as AR / VR. The imaging effect of AR / VR display modules is closely related to the quality of module bonding. Inappropriate materials and bonding process selection will lead to failure of optical functions such as optical resolution, contrast, and brightness uniformity. How to improve the quality of optical imaging through the combination of materials and processes has become a problem that many manufacturers in the AR / VR industry are eager to solve. Inappropriate materials and bonding processes will cause defects such as uneven mura, distortion, orange peel, and surface pinholes.

[0003] To solve the above problems, conventional technology improves the imaging quality by increasing the lamination temperature to soften the optical film at high temperature. Patent document with publication number CN115505355A discloses a UV optical adhesive, which includes, by mass: 25 to 45 parts of polyurethane acrylate, 24 to 42 parts of methyl methacrylate, 21 to 35 parts of butyl acrylate, 0.05 to 1.5 parts of acrylic acid, 1 to 3 parts of N,N-vinyl bisacrylamide, 0.2 to 1.3 parts of photoinitiator, 0.05 to 0.8 parts of antioxidant, and 0.1 to 1 parts of silane coupling agent. The above-mentioned UV optical adhesive has high light transmittance, high adhesion and high reaction temperature through formula adjustment, thereby avoiding volatilization of the UV optical adhesive during high-temperature bonding, and further avoiding the decrease in gel content and cross-linking modulus after curing, thereby eliminating the factors that cause bubbles to appear in the glue after bonding, ensuring the display effect and improving the product yield.

[0004] However, the applicant found in further research that excessively high temperatures can easily cause optical film materials to deform, which can reduce product yields. In addition, the loss rate of equipment increases at excessively high temperatures, which greatly increases production costs. That is, the solution of softening the film material by increasing the temperature produces the following three negative effects: high-temperature deformation of the film material increases the defect rate caused by the film material; at the same time, the loss rate of high-temperature equipment increases; and the process time is extended, increasing production costs. Summary of the invention

[0005] Based on this, it is necessary to provide an optical adhesive, a curved surface bonding structure, and the application of the optical adhesive in the curved surface bonding structure.

[0006] In one embodiment, an optical adhesive comprises, by weight:

[0007] Polyurethane acrylate 20 to 45 parts,

[0008] 20 to 45 parts of methyl methacrylate,

[0009] Butyl acrylate 20 to 35 parts,

[0010] Epoxy acrylate 3 to 3.5 parts,

[0011] 2.7 to 4.6 parts of reactive monomers,

[0012] 0.5 to 1 part of photoinitiator, and

[0013] Antioxidant 0.1 to 0.2 parts.

[0014] The above-mentioned optical adhesive has been further optimized through formula. On the one hand, it does not need to be bonded at a high reaction temperature, which avoids deformation of the optical film material due to high temperature, thereby ensuring the product yield, and also avoids the equipment working at excessively high temperatures, which leads to an increase in the loss rate. The relatively high temperature process reduces the production time, thereby reducing the production cost to a certain extent; on the other hand, it ensures the low-frequency modulation transfer function indicators, so it has better contrast, resolution and field of view, and has better performance in optical indicators such as surface waviness, local curvature error, color uniformity, light transmittance and astigmatism, thereby ensuring the display effect.

[0015] In one embodiment, the reaction monomers include, by mass:

[0016] 1.5 to 2 parts of hydroxy acrylate,

[0017] 0.2 to 0.6 parts of ethylene glycol dimethacrylate, and

[0018] Dipentaerythritol hexaacrylate 1.0 to 2.0 parts.

[0019] In one embodiment, the photoinitiator comprises, by weight:

[0020] 0.5 to 1.0 parts of diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide.

[0021] In one embodiment, the antioxidant comprises, by mass: 0.05 to 0.1 parts of 2,6-di-tert-butyl-4-methylphenol, and

[0022] 0.05 to 0.1 parts of tri(2,4-di-tert-butyl)phenyl phosphite.

[0023] In one embodiment, the optical adhesive comprises, by weight:

[0024] Polyurethane acrylate 25 to 40 parts, methyl methacrylate 25 to 40 parts, butyl acrylate 25 to 30 parts,

[0025] Epoxy acrylate 3.1 to 3.4 parts,

[0026] 3 to 4.2 parts of reactive monomers,

[0027] 0.6 to 0.9 parts of photoinitiator, and

[0028] Antioxidant 0.1 to 0.2 parts.

[0029] In one embodiment, the optical adhesive comprises, by weight:

[0030] Polyurethane acrylate 25 to 40 parts, methyl methacrylate 25 to 40 parts, butyl acrylate 25 to 30 parts,

[0031] Epoxy acrylate 3.1 to 3.4 parts,

[0032] Hydroxyacrylate 1.6 to 1.9 parts,

[0033] Ethylene glycol dimethacrylate 0.3 to 0.5 parts,

[0034] 1.2 to 1.8 parts of dipentaerythritol hexaacrylate,

[0035] 0.6 to 0.9 parts of diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide,

[0036] 0.06 to 0.09 parts of 2,6-di-tert-butyl-4-methylphenol, and

[0037] 0.06 to 0.09 parts of tri(2,4-di-tert-butyl)phenyl phosphite.

[0038] In one embodiment, the optical adhesive includes or only includes, by mass ratio:

[0039] 30.1 parts of polyurethane acrylate, 33.5 parts of methyl methacrylate, 29 parts of butyl acrylate, 3.4 parts of epoxy acrylate, 1.6 parts of hydroxy acrylate, 0.6 parts of diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, 0.2 parts of ethylene glycol dimethacrylate, 0.05 parts of 2,6-di-tert-butyl-4-methylphenol, 0.05 parts of tris (2,4-di-tert-butyl) phenyl phosphite and 1.5 parts of dipentaerythritol hexaacrylate; or,

[0040] 35.3 parts of polyurethane acrylate, 30.5 parts of methyl methacrylate, 26.5 parts of butyl acrylate, 3.1 parts of epoxy acrylate, 1.8 parts of hydroxy acrylate, 0.9 parts of diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, 0.3 parts of ethylene glycol dimethacrylate, 0.05 parts of 2,6-di-tert-butyl-4-methylphenol, 0.05 parts of tris (2,4-di-tert-butyl) phenyl phosphite and 1.5 parts of dipentaerythritol hexaacrylate; or,

[0041] 25 parts of polyurethane acrylate, 41 parts of methyl methacrylate, 25.7 parts of butyl acrylate, 3.4 parts of epoxy acrylate, 2 parts of hydroxy acrylate, 0.5 parts of diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, 0.3 parts of ethylene glycol dimethacrylate, 0.05 parts of 2,6-di-tert-butyl-4-methylphenol, 0.05 parts of tris (2,4-di-tert-butyl) phenyl phosphite and 2 parts of dipentaerythritol hexaacrylate; or,

[0042] 42 parts of polyurethane acrylate, 25 parts of methyl methacrylate, 26.2 parts of butyl acrylate, 3 parts of epoxy acrylate, 1.5 parts of hydroxy acrylate, 1 part of diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, 0.2 parts of ethylene glycol dimethacrylate, 0.05 parts of 2,6-di-tert-butyl-4-methylphenol, 0.05 parts of tris (2,4-di-tert-butyl) phenyl phosphite and 1 part of dipentaerythritol hexaacrylate.

[0043] In one embodiment, a curved surface bonding structure includes at least two substrate layers and an optical adhesive layer disposed between two adjacent substrate layers, wherein the optical adhesive layer is formed by curing an optical adhesive, and the optical adhesive includes, by mass:

[0044] Polyurethane acrylate 20 to 45 parts,

[0045] 20 to 45 parts of methyl methacrylate,

[0046] Butyl acrylate 20 to 35 parts,

[0047] Epoxy acrylate 3 to 3.5 parts,

[0048] 2.7 to 4.6 parts of reactive monomers,

[0049] 0.5 to 1 part of photoinitiator, and

[0050] Antioxidant 0.1 to 0.2 parts.

[0051] In one embodiment, the curved surface fitting structure is specifically a multi-layer film structure module for glasses.

[0052] In one embodiment, an optical adhesive is used in a curved surface bonding structure, wherein the optical adhesive comprises, by weight:

[0053] Polyurethane acrylate 20 to 45 parts,

[0054] 20 to 45 parts of methyl methacrylate,

[0055] Butyl acrylate 20 to 35 parts,

[0056] Epoxy acrylate 3 to 3.5 parts,

[0057] 2.7 to 4.6 parts of reactive monomers,

[0058] 0.5 to 1 part of photoinitiator, and

[0059] Antioxidant 0.1 to 0.2 parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the conventional technology, the drawings required for use in the embodiments or the conventional technology descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0061] Figure 1 This is the waviness diagram of the control example.

[0062] Figure 2 This is a waviness diagram of the optical adhesive embodiment 1 described in this application.

[0063] Figure 3 This is the sharpness diagram of the control example.

[0064] Figure 4 This is the sharpness diagram of the optical adhesive embodiment 1 described in this application.

[0065] Figure 5 This is a virtual imaging distance diagram for the control example.

[0066] Figure 6 This is a virtual imaging distance diagram of the optical adhesive embodiment 1 described in this application.

[0067] Figure 7 This is the color uniformity diagram of the control example.

[0068] Figure 8 This is a color uniformity diagram of the optical adhesive embodiment 1 described in this application.

[0069] Fig. 9 Molar mass diagram for the control example.

[0070] Fig.10 This is a molar mass diagram of the optical adhesive embodiment 1 described in this application.

[0071] Fig.11 The storage modulus diagram of the control example.

[0072] Fig.12 This is a storage modulus diagram of the optical adhesive embodiment 1 described in this application. DETAILED DESCRIPTION

[0073] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0074] It should be noted that when a component is referred to as being "fixed to" or "disposed on" another component, it may be directly on the other component or there may also be a central component. When a component is considered to be "connected to" another component, it may be directly connected to the other component or there may be a central component at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used in the specification of this application are for illustrative purposes only and do not represent the only implementation method.

[0075] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0076] In the present application, unless otherwise clearly specified and limited, a first feature being “above” or “below” a second feature may mean that the first feature is directly in contact with the second feature, or the first feature and the second feature are in contact indirectly through an intermediate medium. Moreover, a first feature being “above”, “above”, or “above” a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being “below”, “below”, or “below” a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0077] Unless otherwise defined, all technical and scientific terms used in the specification of this application have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used in the specification of this application includes any and all combinations of one or more related listed items.

[0078] The present application discloses an optical adhesive, a curved surface bonding structure, and an application of the optical adhesive in the curved surface bonding structure, which includes some or all of the features of the following embodiments. In one embodiment of the present application, an optical adhesive includes, by mass: 20 to 45 parts of polyurethane acrylate, 20 to 45 parts of methyl methacrylate, 20 to 35 parts of butyl acrylate, 3 to 3.5 parts of epoxy acrylate, 2.7 to 4.6 parts of reactive monomers, 0.5 to 1 part of photoinitiator, and 0.1 to 0.2 parts of antioxidant. The above optical adhesive is further optimized through formula. On the one hand, it does not need to be bonded at a higher reaction temperature. For example, it can be used for 3D curved surface bonding of ARVR glasses, avoiding deformation of optical film materials due to high temperature, thereby ensuring product yield, and avoiding the equipment working at excessively high temperatures, which leads to increased loss rate. The relatively high temperature process reduces the production time, thereby reducing production costs to a certain extent; on the other hand, it ensures the low-frequency modulation transfer function indicators, so it has better contrast, resolution and field of view, and has better performance in optical indicators such as surface waviness, local curvature error, color uniformity, light transmittance and astigmatism, thereby ensuring the display effect.

[0079] It should be noted that, in each embodiment, the part, i.e., the mass part, i.e., the mass part number, can be understood as grams, milligrams, kilograms, catties, kilograms, pounds, tons, etc. Taking grams as an example, for example, 1 part is a mass between 0.0001 and 10000 grams; for example, 1 part can be 0.001g, 0.01g, 0.02g, 0.05g, 0.1g, 0.2g, 0.5g, 1g, 2g, 3g, 4g, 5g, 10g, 15g, 20g, 30g, 50g, 80g, 100g, 500g, 1000g, 5000g, 10000g or 50000g, etc., and is not limited thereto, and can be selected according to actual production and manufacturing, and the same applies to each embodiment. For example, 1 part is 1 gram, 0.1 part is 0.1 gram; or, 1 part is 10 grams, 0.1 part is 1 gram; or, 1 part is 100 grams, 0.1 part is 10 grams; and so on. In specific applications, it can be flexibly designed according to actual needs, as long as a certain mass ratio or mass proportion of each component is met.

[0080] Optical adhesives can be divided into liquid adhesives and solid adhesive tapes or solid adhesive films according to the application form. The present application involves the research and development design of solid adhesive films. The optical adhesives described in each embodiment are suitable for display modules, flexible modules and curved modules, etc., so they can also be called flexible optical adhesives. Further, the following describes the ratio design principle of the optical adhesive. The optical adhesive described in the present application improves the imaging quality, especially the imaging quality of the 3D curved bonding module of AR / VR glasses, by improving the softness of the material and adjusting the curing and cross-linking properties. In this case, it is necessary to modify the polyurethane acrylate prepolymer so that the colloid has a lower elastic modulus before curing to adapt to the bonding of lenses with various curvatures; after curing, it has a higher elastic modulus and high adhesion to pass the high temperature and high humidity and cold and hot cycle reliability verification; at the same time, it is necessary to overcome the problems mentioned above to avoid the need for bonding at a higher reaction temperature due to material reasons.

[0081] In one embodiment, 20 to 45 parts of polyurethane acrylate are used as PUA resin to provide prepolymer, and further, the molecular weight of polyurethane acrylate is 45,000 to 60,000, in one embodiment, the molecular weight of polyurethane acrylate is 48,000 to 52,000, and in one embodiment, the molecular weight of polyurethane acrylate is 50,000, that is, the polyurethane acrylate prepolymer with a molecular weight of about 50,000 is used to increase the rigidity, temperature resistance and crosslinking density of the material. In one embodiment, 20 to 45 parts of methyl methacrylate are used as comonomers to improve cohesion, 20 to 35 parts of butyl acrylate are used as comonomers to adjust the softening temperature, and 3 to 3.5 parts of epoxy acrylate are used as comonomers to improve temperature softening performance.

[0082] The components here are selected to meet the design concept of avoiding high-temperature bonding. Therefore, there is no need to consider how to increase the reaction temperature and avoid the volatilization of optical glue during high-temperature bonding at high reaction temperatures. The obtained optical glue has high leveling properties, so that the optical film material can better adapt to the variation of lens curvature and have better bonding optical performance, avoiding linear ripples caused by wrinkles, and avoiding annular ripples caused by the shrinkage of optical film materials after reliability verification; therefore, there is no orange peel phenomenon, annular ripples and other defects. The surface of the material is flat after bonding, which effectively improves the optical uniformity of the curved surface product; it has excellent MTF values ​​at low spatial frequencies and excellent color contrast; and it still has good MTF values ​​at higher spatial frequencies, with delicate and clear perception and excellent resolution. Moreover, the local curvature error is small after bonding with the optical film, which can better fit the design value than traditional glue materials. At the same time, the astigmatism is small, the viewing angle is large, and good clarity can be retained at the edge of the field of view, which is helpful to achieve the design purpose. The AR / VR products made with the optical glue have excellent color uniformity and better color difference performance than traditional glue products.

[0083] The reactive monomers can be used as crosslinking agents, which are also called crosslinking aids, to improve the strength and elasticity of the material. It is understandable that some reactive monomers can also have photocuring or other effects at the same time. Further, in one of the embodiments, the reactive monomers include hydroxy acrylate and ethylene glycol dimethacrylate. In one of the embodiments, the reactive monomers include, by mass, 1.5 to 2 parts of hydroxy acrylate, 0.2 to 0.6 parts of ethylene glycol dimethacrylate, and 1.0 to 2.0 parts of dipentaerythritol hexaacrylate. That is, the optical adhesive includes, by mass, 20 to 45 parts of polyurethane acrylate, 20 to 45 parts of methyl methacrylate, 20 to 35 parts of butyl acrylate, 3 to 3.5 parts of epoxy acrylate, 1.5 to 2 parts of hydroxy acrylate, 0.2 to 0.6 parts of ethylene glycol dimethacrylate, 1.0 to 2.0 parts of dipentaerythritol hexaacrylate, 0.5 to 1 parts of photoinitiator, and 0.1 to 0.2 parts of antioxidant. The rest of the embodiments are similar and will not be described in detail.

[0084] Photoinitiators are also called photosensitizers or photocuring agents, which are used to initiate monomer polymerization and crosslinking curing under certain conditions. It is understandable that some photoinitiators can also have the characteristics of crosslinking agents. Further, in one of the embodiments, the photoinitiator includes diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide. In one of the embodiments, the photoinitiator includes 0.5 to 1.0 parts of diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide by mass. That is, the optical adhesive includes 20 to 45 parts of polyurethane acrylate, 20 to 45 parts of methyl methacrylate, 20 to 35 parts of butyl acrylate, 3 to 3.5 parts of epoxy acrylate, 2.7 to 4.6 parts of reactive monomers, 0.5 to 1.0 parts of diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide and 0.1 to 0.2 parts of antioxidants. This design balances the ratio and has better effects on light transmittance, normal temperature adhesion and multiple optical indicators.

[0085] Antioxidants are mainly used for anti-oxidation. Depending on the selected materials, some antioxidants may also have the characteristics of cross-linking agents or other characteristics, which should not be regarded as a limitation on the selection of materials for this application. Further, in one of the embodiments, the antioxidant includes by mass: 2,6-di-tert-butyl-4-methylphenol and tris(2,4-di-tert-butyl)phenyl phosphite. In one of the embodiments, the antioxidant includes by mass: 0.05 to 0.1 parts of 2,6-di-tert-butyl-4-methylphenol and 0.05 to 0.1 parts of tris(2,4-di-tert-butyl)phenyl phosphite. That is, the optical adhesive includes, by mass, 20 to 45 parts of polyurethane acrylate, 20 to 45 parts of methyl methacrylate, 20 to 35 parts of butyl acrylate, 3 to 3.5 parts of epoxy acrylate, 2.7 to 4.6 parts of reactive monomers, 0.5 to 1 part of photoinitiator, 0.05 to 0.1 parts of 2,6-di-tert-butyl-4-methylphenol and 0.05 to 0.1 parts of tris(2,4-di-tert-butyl)phenyl phosphite. This design further uses 30% to 40% of polyurethane acrylate as prepolymer; 50% to 70% of methyl methacrylate, butyl acrylate, hydroxy acrylate, etc. as copolymers to improve the cohesion of the adhesive, adjust the softening temperature, and increase the curing rate; photoinitiators, crosslinking agents, and antioxidants ensure the physical properties and appearance of the optical adhesive.

[0086] In one embodiment, the optical adhesive includes, by mass: 25 to 40 parts of polyurethane acrylate, 25 to 40 parts of methyl methacrylate, 25 to 30 parts of butyl acrylate, 3.1 to 3.4 parts of epoxy acrylate, 3 to 4.2 parts of reactive monomer, 0.6 to 0.9 parts of photoinitiator and 0.1 to 0.2 parts of antioxidant. In one embodiment, the optical adhesive includes, by mass, 25 to 40 parts of polyurethane acrylate, 25 to 40 parts of methyl methacrylate, 25 to 30 parts of butyl acrylate, 3.1 to 3.4 parts of epoxy acrylate, 1.6 to 1.9 parts of hydroxy acrylate, 0.3 to 0.5 parts of ethylene glycol dimethacrylate, 1.2 to 1.8 parts of dipentaerythritol hexaacrylate, 0.6 to 0.9 parts of diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, 0.06 to 0.09 parts of 2,6-di-tert-butyl-4-methylphenol and 0.06 to 0.09 parts of tris (2,4-di-tert-butyl) phenyl phosphite. Such a design further optimizes the ingredient ratio, using polyurethane acrylate as the main resin, methyl methacrylate to improve temperature resistance, butyl acrylate to improve adhesion, epoxy acrylate to improve temperature softening, hydroxy acrylate and ethylene glycol dimethacrylate as UV diluents and to improve crosslinking degree, dipentaerythritol hexaacrylate to improve photocuring speed and crosslinking degree, diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide as a photoinitiator, 2,6-di-tert-butyl-4-methylphenol to improve antioxidant properties and crosslinking properties, and tris (2,4-di-tert-butyl) phenyl phosphite to improve antioxidant properties and improve thermal stability of the material.

[0087] In one embodiment, the optical adhesive includes, by mass proportion: 30.1 parts of polyurethane acrylate, 33.5 parts of methyl methacrylate, 29 parts of butyl acrylate, 3.4 parts of epoxy acrylate, 1.6 parts of hydroxy acrylate, 0.6 parts of diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, 0.2 parts of ethylene glycol dimethacrylate, 0.05 parts of 2,6-di-tert-butyl-4-methylphenol, 0.05 parts of tris (2,4-di-tert-butyl) phenyl phosphite and 1.5 parts of dipentaerythritol hexaacrylate. In one embodiment, the optical adhesive includes, by mass proportion: 35.3 parts of polyurethane acrylate, 30.5 parts of methyl methacrylate, 26.5 parts of butyl acrylate, 3.1 parts of epoxy acrylate, 1.8 parts of hydroxy acrylate, 0.9 parts of diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, 0.3 parts of ethylene glycol dimethacrylate, 0.05 parts of 2,6-di-tert-butyl-4-methylphenol, 0.05 parts of tris (2,4-di-tert-butyl) phenyl phosphite and 1.5 parts of dipentaerythritol hexaacrylate. In one embodiment, the optical adhesive includes, by mass proportion: 25 parts of polyurethane acrylate, 41 parts of methyl methacrylate, 25.7 parts of butyl acrylate, 3.4 parts of epoxy acrylate, 2 parts of hydroxy acrylate, 0.5 parts of diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, 0.3 parts of ethylene glycol dimethacrylate, 0.05 parts of 2,6-di-tert-butyl-4-methylphenol, 0.05 parts of tris (2,4-di-tert-butyl) phenyl phosphite and 2 parts of dipentaerythritol hexaacrylate. In one of the embodiments, the optical adhesive comprises, by mass ratio, 42 parts of polyurethane acrylate, 25 parts of methyl methacrylate, 26.2 parts of butyl acrylate, 3 parts of epoxy acrylate, 1.5 parts of hydroxy acrylate, 1 part of diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, 0.2 parts of ethylene glycol dimethacrylate, 0.05 parts of 2,6-di-tert-butyl-4-methylphenol, 0.05 parts of tris (2,4-di-tert-butyl) phenyl phosphite and 1 part of dipentaerythritol hexaacrylate. Alternatively, for the above four embodiments, the optical adhesive is only composed of the corresponding component ratios, and does not include other substances.

[0088] Several examples of specific ratios are given below to further illustrate the ratios of the optical adhesives described in the embodiments of the present application and their technical effects, wherein 0.5 grams or 1 gram is taken for each portion, and the same applies to the other embodiments, which will not be described in detail.

[0089] Control example: The traditional optical adhesive used as a control only includes 55.0 parts of butyl acrylate, 2.2 parts of tert-butyl acrylate, 12.0 parts of methyl acrylate, 13.0 parts of methyl methacrylate, 10.5 parts of N,N-dimethylacrylamide, 0.1 parts of vinyl trimethoxysilane, 6.6 parts of ethoxylated trimethylolpropane triacrylate and 0.6 parts of phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide in proportion by mass.

[0090] Example 1: The optical adhesive includes only 30.1 parts of polyurethane acrylate, 33.5 parts of methyl methacrylate, 29 parts of butyl acrylate, 3.4 parts of epoxy acrylate, 1.6 parts of hydroxy acrylate, 0.6 parts of diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, 0.2 parts of ethylene glycol dimethacrylate, 0.05 parts of 2,6-di-tert-butyl-4-methylphenol, 0.05 parts of tris (2,4-di-tert-butyl) phenyl phosphite and 1.5 parts of dipentaerythritol hexaacrylate in proportion by mass.

[0091] Example 2: The optical adhesive includes only 35.3 parts of polyurethane acrylate, 30.5 parts of methyl methacrylate, 26.5 parts of butyl acrylate, 3.1 parts of epoxy acrylate, 1.8 parts of hydroxy acrylate, 0.9 parts of diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, 0.3 parts of ethylene glycol dimethacrylate, 0.05 parts of 2,6-di-tert-butyl-4-methylphenol, 0.05 parts of tris (2,4-di-tert-butyl) phenyl phosphite and 1.5 parts of dipentaerythritol hexaacrylate in proportion by mass.

[0092] Example 3: The optical adhesive includes only 25 parts of polyurethane acrylate, 41 parts of methyl methacrylate, 25.7 parts of butyl acrylate, 3.4 parts of epoxy acrylate, 2 parts of hydroxy acrylate, 0.5 parts of diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, 0.3 parts of ethylene glycol dimethacrylate, 0.05 parts of 2,6-di-tert-butyl-4-methylphenol, 0.05 parts of tris (2,4-di-tert-butyl) phenyl phosphite and 2 parts of dipentaerythritol hexaacrylate in proportion by mass.

[0093] Example 4: The optical adhesive includes only 42 parts of polyurethane acrylate, 25 parts of methyl methacrylate, 26.2 parts of butyl acrylate, 3 parts of epoxy acrylate, 1.5 parts of hydroxy acrylate, 1 part of diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, 0.2 parts of ethylene glycol dimethacrylate, 0.05 parts of 2,6-di-tert-butyl-4-methylphenol, 0.05 parts of tris (2,4-di-tert-butyl) phenyl phosphite and 1 part of dipentaerythritol hexaacrylate in proportion by mass.

[0094] The comparison of Examples 1 to 4 is shown in Table 1 below:

[0095] Formula ingredients % Example 1 Example 2 Example 3 Example 4 Polyurethane acrylate 30.1 35.3 25 42 Methyl Methacrylate 33.5 30.5 41 25 Butyl acrylate 29 26.5 25.7 26.2 Epoxy Acrylate 3.4 3.1 3.4 3 Hydroxyacrylate 1.6 1.8 2 1.5 Diphenyl (2,4,6-trimethylbenzoyl)phosphine oxide 0.6 0.9 0.5 1 Ethylene glycol dimethacrylate 0.2 0.3 0.3 0.2 2,6-Di-tert-butyl-4-methylphenol 0.05 0.05 0.05 0.05 Tris(2,4-di-tert-butyl)phenyl phosphite 0.05 0.05 0.05 0.05 Dipentaerythritol hexaacrylate 1.5 1.5 2 1

[0096] The performance test comparison of Table 1 is shown in Table 2 below.

[0097]

[0098] Table 2

[0099] The smaller the surface waviness, the better. The optical adhesive has excellent surface waviness after being bonded to the optical film. The surface waviness of Examples 1, 2 and 4 is about 50-60 μrad, and the surface waviness of Example 3 is slightly larger, but significantly smaller than that of the control example. The surface waviness of Examples 1, 2 and 4 is about 40% of that of the control example. The surface waviness of the control example is shown in the figure Figure 1 As shown, the surface waviness diagram of Example 1 is as follows Figure 2 As shown, by comparison, it can be seen that the surface waviness of Example 1 is better, so the surface of the material is smoother after bonding, which effectively improves the optical uniformity of the curved surface product.

[0100] The peak to valley value is also called the peak to valley value, and the smaller the value, the better. The PV values ​​of Examples 1 to 4 are 2.7 to 4.0, which are significantly smaller than those of the control example, and the maximum value is about 60% of that of the control example.

[0101] The local curvature error (LCE) of the optical adhesive described in the present application after bonding with the optical film is small, and is approximately 0.27 to 0.65 in Examples 1 to 4, which are significantly smaller than the control example, and the maximum value is approximately 80% of the control example, which is more in line with the design value than traditional adhesives.

[0102] Sharpness is also called contrast, and the larger the contrast, the better. The sharpness of Examples 1 to 4 is significantly better than that of the control example, about 150% or more of the control example. Figure 3 As shown, the sharpness diagram of Example 1 is as follows Figure 4 As shown, by comparison, it can be seen that the sharpness performance of Example 1 is better, so the sample has better clarity and uniform distribution after bonding, which effectively improves the optical uniformity of the curved surface product.

[0103] The low-frequency Modulation Transfer Function (MTF) value of traditional optical adhesive products decreases greatly with the increase of spatial frequency. This will cause the low-frequency MTF of traditional optical adhesive to be excellent, but the MTF decreases too much at high frequencies, resulting in a decrease in resolution and a poor visual experience. The AR / VR products made with the optical adhesive described in the present application have excellent color contrast—excellent MTF values ​​at low spatial frequencies, excellent contrast performance, and 5PPD (Pixels Per Degree, angular resolution) of approximately 0.8 to 0.9. And the AR / VR products made with the optical adhesive described in the present application have a delicate and clear look—still have good MTF values ​​at higher spatial frequencies, excellent resolution, and 20PPD of approximately 0.7 to 0.8. The AR / VR products made with the optical adhesive described in the present application can also retain good clarity at the edges of the field of view, have the advantage of a wide field of view, and are helpful in achieving the design value. The waviness graph of the control example is shown below. Figure 3 As shown, the waviness diagram of Example 1 is as follows Figure 4 As shown, by comparison, it can be seen that the surface flatness and color contrast of Example 1 are better.

[0104] The virtual imaging distance (VID) is the distance from the human eye to the virtual image. This embodiment shows the 4sigma value of VID, and the smaller the better. It can be seen from Table 2 that the virtual imaging distance fluctuations of embodiments 1 to 4 are smaller than those of the control example. The virtual imaging distance of the control example is shown in FIG. Figure 5 As shown, the virtual imaging distance diagram of Example 1 is as follows Figure 6 As shown, by comparison, it can be seen that the virtual imaging distance of Example 1 is more stable, more uniform, and has fewer defects than that of the control example.

[0105] The fact that the S&T directions of the same field of view are not in the same focal plane is called astigmatism. Due to the difference in sensitivity, traditional optical adhesives are affected by eccentricity and the image plane movement in the T direction is several times that in the S direction, making the foci in the S and T directions not on the same plane. In addition, the difference in the surface shape of the lens at different angles will also lead to different focal lengths in the S&T directions, resulting in astigmatism. Therefore, the smaller the astigmatism, the better. In the AR / VR products made with the optical adhesive described in this application, the astigmatism of Examples 1 to 4 is smaller than that of the control example.

[0106] The AR / VR products made of the optical adhesive described in this application have excellent color uniformity (Transmittance & Color Uniformity), and have better color difference performance than traditional adhesive products. Figure 7 As shown, the color uniformity diagram of Example 1 is as follows Figure 8As shown, by comparison, it can be seen that the color uniformity of Example 1 is better than that of the control example, so it has better color difference performance in practical applications. At the same time, the AR / VR product made of the optical adhesive described in this application has high transmittance, and the wavelength is 940cm- 1 The transmittance of light with a wavelength of about 11.38 microns is about 0.8 to 0.9; for light with a wave number of 850cm- 1 The transmittance of light (i.e., a wavelength of about 12.59 microns) is about 0.6 to 0.7.

[0107] The molar mass diagram of the control example is shown in Fig. 9 As shown, the molar mass diagram of Example 1 is as follows Fig.10 As shown, by comparison, it can be seen that the optical adhesive of Example 1 has higher leveling properties, which is beneficial to improving the bonding flatness, thereby improving the orange peel phenomenon.

[0108] The optical adhesive has a higher uncured tan delta at 85°C, i.e., a loss tangent value. The hard segment acrylate is replaced by polyurethane acrylate with higher softness, and the glass transition temperature (Tg) of the optical adhesive, i.e., the glass transition temperature of the resin, is lowered to overcome the local stress points caused by stress concentration due to the large variation in lens curvature when the curved surfaces are bonded.

[0109] The optical adhesive has a lower uncured modulus at 85°C and a higher cured modulus at 85°C. The lower uncured modulus at 85°C allows the optical film to better adapt to lens curvature variations, have better lamination optical performance, and avoid linear ripples caused by wrinkles; the higher cured modulus at 85°C allows the lamination lens to avoid annular ripples caused by shrinkage of the optical film after reliability verification. Therefore, the overall optical film can better adapt to lens curvature variations, have better lamination optical performance, avoid linear ripples caused by wrinkles, and avoid annular ripples caused by shrinkage of the optical film after reliability verification.

[0110] The storage modulus of the control example is shown in the figure Fig.11 As shown, the storage modulus diagram of Example 1 is as shown Fig.12 The comparative analysis is shown in Table 3 below.

[0111] TG 85℃ uncured tan delta 85℃cured modulus Comparison example 10℃ 0.485 134kPa Example 1 -35℃ 1.05 2349kPa

[0112] Table 3

[0113] By comparison, it can be seen that the optical adhesive of Example 1 has a lower glass transition temperature, a larger uncured dielectric loss tangent at 85°C, and a higher cured modulus at 85°C. Compared with the control example, Example 1 has higher softness and lower glass transition temperature, which makes various ARVR optical imaging indicators excellent and more suitable for 3D curved surface bonding modules. As mentioned above, there is no orange peel phenomenon, annular ripples and other defects. The surface of the material is smooth after bonding, which effectively improves the optical uniformity of the curved surface product.

[0114] By comparing Examples 1 to 4 and the control example, it can be seen that in terms of performance testing, each embodiment of the present application has obvious advantages over the control example, especially in Example 1, except for the sharpness index, the other test indicators are relatively good. The following will continue to explain from the aspects of design principles and specific tests. The optical adhesive described in the present application is mixed with photoinitiators, multifunctional cross-linking agents and antioxidants by two or more flexible co-monomers, and replaces the high molecular weight polymer prepolymer with a low molecular weight polyurethane acrylate co-monomer. By increasing the leveling property of the optical adhesive, the bonding flatness is improved, and the orange peel phenomenon is improved. At the same time, it has the advantages of high flexibility, low glass transition temperature, high light transmittance and low haze. It can be applied to AR / VR glasses 3D curved surface bonding modules, which can avoid optical defects such as uneven lines, distortion, orange peel and surface pinholes in the display module.

[0115] In one of the embodiments, a curved surface bonding structure includes at least two substrate layers and an optical adhesive layer disposed between two adjacent substrate layers, wherein the optical adhesive layer is formed by curing the optical adhesive described in any embodiment. In one of the embodiments, the optical adhesive includes, by mass: 20 to 45 parts of polyurethane acrylate, 20 to 45 parts of methyl methacrylate, 20 to 35 parts of butyl acrylate, 3 to 3.5 parts of epoxy acrylate, 2.7 to 4.6 parts of reactive monomers, 0.5 to 1 part of photoinitiator, and 0.1 to 0.2 parts of antioxidant. The same applies to the remaining embodiments and will not be described in detail. In one of the embodiments, the curved surface bonding structure is specifically a multi-layer film structure module for glasses. In one of the embodiments, the curved surface bonding structure is a multi-layer film structure module of virtual reality (VR) glasses, that is, the optical adhesive described in each embodiment of the present application can be used for bonding of multi-layer film structure modules of VR glasses; such a curved surface bonding structure, on the one hand, does not need to be bonded at a higher reaction temperature, thereby avoiding deformation of the optical film material due to high temperature, thereby ensuring product yield, and also avoiding the equipment working at an excessively high temperature, which leads to an increase in the loss rate, and the relatively high temperature process reduces the production time, thereby reducing the production cost to a certain extent; on the other hand, it ensures the low-frequency modulation transfer function index, so it has better contrast, resolution and field of view, and has better performance in optical indicators such as surface waviness, local curvature error, color uniformity, light transmittance and astigmatism, thereby ensuring the display effect.

[0116] In one embodiment, an optical adhesive is used in a curved surface bonding structure, wherein the optical adhesive is the optical adhesive described in any embodiment; that is, the optical adhesive described in any embodiment is used in a curved surface bonding structure. In one embodiment, the optical adhesive includes, by mass: 20 to 45 parts of polyurethane acrylate, 20 to 45 parts of methyl methacrylate, 20 to 35 parts of butyl acrylate, 3 to 3.5 parts of epoxy acrylate, 2.7 to 4.6 parts of reactive monomers, 0.5 to 1 part of photoinitiator, and 0.1 to 0.2 parts of antioxidant. The rest of the embodiments are similar and will not be described in detail.

[0117] It should be noted that other embodiments of the present application also include optical adhesives, curved surface bonding structures and applications of optical adhesives in curved surface bonding structures that can be implemented by combining the technical features in the above embodiments.

[0118] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0119] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the scope of patent protection of the present application shall be subject to the attached claims.

Claims

1. An optical adhesive, characterized in that: Included by mass: Polyurethane acrylate 20 to 45 parts, 20 to 45 parts of methyl methacrylate, Butyl acrylate 20 to 35 parts, Epoxy acrylate 3 to 3.5 parts, 2.7 to 4.6 parts of reactive monomers, wherein the reactive monomers include hydroxy acrylate and ethylene glycol dimethacrylate, 0.5 to 1 part of photoinitiator, and Antioxidant 0.1 to 0.2 parts.

2. The optical adhesive according to claim 1, characterized in that: The reaction monomers include by mass: 1.5 to 2 parts of hydroxy acrylate, 0.2 to 0.6 parts of ethylene glycol dimethacrylate, and Dipentaerythritol hexaacrylate 1.0 to 2.0 parts.

3. The optical adhesive according to claim 2, characterized in that: The photoinitiator comprises by mass: 0.5 to 1.0 parts of diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide.

4. The optical adhesive according to claim 3, characterized in that: The antioxidants include by mass: 0.05 to 0.1 parts of 2,6-di-tert-butyl-4-methylphenol, and 0.05 to 0.1 parts of tri(2,4-di-tert-butyl)phenyl phosphite.

5. The optical adhesive according to claim 1, characterized in that: Included by mass: Polyurethane acrylate 25 to 40 parts, 25 to 40 parts of methyl methacrylate, Butyl acrylate 25 to 30 parts, Epoxy acrylate 3.1 to 3.4 parts, 3 to 4.2 parts of reactive monomers, 0.6 to 0.9 parts of photoinitiator, and Antioxidant 0.1 to 0.2 parts.

6. The optical adhesive according to claim 5, characterized in that: Included by mass: Polyurethane acrylate 25 to 40 parts, 25 to 40 parts of methyl methacrylate, Butyl acrylate 25 to 30 parts, Epoxy acrylate 3.1 to 3.4 parts, Hydroxyacrylate 1.6 to 1.9 parts, Ethylene glycol dimethacrylate 0.3 to 0.5 parts, 1.2 to 1.8 parts of dipentaerythritol hexaacrylate, 0.6 to 0.9 parts of diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, 0.06 to 0.09 parts of 2,6-di-tert-butyl-4-methylphenol, and 0.06 to 0.09 parts of tri(2,4-di-tert-butyl)phenyl phosphite.

7. The optical adhesive according to claim 1, characterized in that: Included by mass proportion only: 30.1 parts of polyurethane acrylate, 33.5 parts of methyl methacrylate, 29 parts of butyl acrylate, 3.4 parts of epoxy acrylate, 1.6 parts of hydroxy acrylate, 0.6 parts of diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, 0.2 parts of ethylene glycol dimethacrylate, 0.05 parts of 2,6-di-tert-butyl-4-methylphenol, 0.05 parts of tris (2,4-di-tert-butyl) phenyl phosphite and 1.5 parts of dipentaerythritol hexaacrylate.

8. A curved surface bonding structure, characterized in that: The invention comprises at least two substrate layers and an optical adhesive layer disposed between two adjacent substrate layers, wherein the optical adhesive layer is formed by curing an optical adhesive, and the optical adhesive comprises, by weight: Polyurethane acrylate 20 to 45 parts, 20 to 45 parts of methyl methacrylate, Butyl acrylate 20 to 35 parts, Epoxy acrylate 3 to 3.5 parts, 2.7 to 4.6 parts of reactive monomers, wherein the reactive monomers include hydroxy acrylate and ethylene glycol dimethacrylate, 0.5 to 1 part of photoinitiator, and Antioxidant 0.1 to 0.2 parts.

9. The curved surface bonding structure according to claim 8, characterized in that: Specifically, it is a multi-layer film structure module for glasses.

10. An application of optical adhesive in a curved surface bonding structure, characterized in that: The optical adhesive comprises, by mass: Polyurethane acrylate 20 to 45 parts, 20 to 45 parts of methyl methacrylate, Butyl acrylate 20 to 35 parts, Epoxy acrylate 3 to 3.5 parts, 2.7 to 4.6 parts of reactive monomers, wherein the reactive monomers include hydroxy acrylate and ethylene glycol dimethacrylate, 0.5 to 1 part of photoinitiator, and Antioxidant 0.1 to 0.2 parts.

Images