Optical adhesive composition with light uniformity effect and preparation method thereof

Abstract

The application discloses an optical adhesive composition with uniform light effect and a preparation method thereof, and belongs to the technical field of optical adhesives. The preparation method of the composition comprises the following steps: after soft monomers, hard monomers, functional monomers, thiourea monomers and uniform light materials are mixed, a photoinitiator is added, and a prepolymer is formed under ultraviolet light irradiation in nitrogen protection; then, a chain transfer agent, an adhesion coupling agent, an antioxidant, a leveling agent and a crosslinking agent are sequentially added and mixed to prepare a glue solution; finally, the glue solution is coated on a heavy release film, and after a light release film is overlapped, ultraviolet curing is performed to form a product. Compared with the prior art, the optical adhesive composition can significantly improve display brightness uniformity while maintaining high light transmittance and good adhesion, is suitable for middle and high-end display modules, and has the advantages of strong process adaptability, uniform light effect and clearness.

Description

Technical Field

[0001] This invention relates to the field of optical adhesive technology, and in particular to an optical adhesive composition with a light-uniforming effect and its preparation method. Background Technology

[0002] Optical adhesive compositions with uniform light distribution are key functional bonding materials in display modules. By adjusting light scattering and transmission characteristics, they can effectively improve the uneven brightness distribution of backlight modules or pixel arrays, enhancing the visual uniformity and comfort of the displayed image. With the development of flexible screens, curved screens, and high-resolution display technologies, the market has placed higher demands on the light transmittance, haze control precision, and brightness uniformity of optical adhesives: while maintaining high transparency and good adhesion, they must precisely control the light scattering angle and intensity to eliminate bright spots, dark areas, and glare, meeting the dual requirements of clear display and soft light field for mid-to-high-end display devices.

[0003] In the prior art, Chinese Patent Publication No. CN118580792A improves the adhesion of optical adhesive to low surface energy substrates by modifying the main resin with organosilicon and introducing functional additives, but it does not involve light uniformity design and cannot solve the problem of uneven display brightness. Chinese Patent Publication No. CN115124928A developed a semi-cured high creep OCA adhesive for curved screens, which achieved the filling of ink step differences and anti-bubble rebound effects, but did not focus on light field distribution control and lacked light uniformity effect. Chinese Patent Publication No. CN119662168A improves the high temperature and high humidity resistance of optical adhesive by introducing thiourea monomer and polyurethane acrylate prepolymer, but its system does not contain light uniformity components and cannot balance transmittance and brightness uniformity.

[0004] The aforementioned existing technologies generally suffer from the following shortcomings: First, the light-diffusing function is difficult to coordinate with properties such as adhesion and weather resistance; optimizing a single function often leads to the sacrifice of other properties. Second, there is a lack of systematic design for matching light scattering and refractive index; the light-diffusing effect relies on a single mechanism (such as simply adding scattering particles), which can easily lead to decreased light transmittance or excessive haze, resulting in a washed-out image. Third, a precisely controllable integrated solution for light transmittance, light-diffusing, and adhesion has not been developed, failing to meet the stringent requirements of high-resolution displays for light field uniformity. Therefore, developing an optical adhesive composition that combines high light transmittance, moderate haze, excellent brightness uniformity, and good process adaptability has become an urgent technical problem to be solved in this field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention aims to provide an optical adhesive composition with uniform light distribution and a method for its preparation.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: A method for preparing an optical adhesive composition with a light-uniforming effect is as follows: Step 1: Heat and stir the soft monomer, hard monomer, functional monomer, thiourea monomer and homogenizing material together to make the system uniform and fully degas. Then add the photoinitiator, continue stirring, and irradiate with ultraviolet light under nitrogen protection to obtain the prepolymer. Step 2: Add chain transfer agent, thickening coupling agent, antioxidant, leveling agent and crosslinking agent to the prepolymer prepared in step 1 in sequence, and continue mixing under stirring conditions to obtain adhesive solution; Step 3: Apply the adhesive solution prepared in Step 2 to the release surface of the heavy release film, control the wet film thickness, then cover the adhesive layer with a light release film, remove air by pressure rollers, and cure under ultraviolet light source to obtain the optical adhesive composition.

[0007] Preferably, the optical adhesive composition with uniform light effect is prepared by the following method, in parts by weight: Step 1: Add 35-60 parts of soft monomer, 10-30 parts of hard monomer, 10-20 parts of functional monomer, 5-15 parts of thiourea monomer and 0.3-1 parts of homogenizing material to a sealed reaction vessel with a stirrer. Heat to 25-35℃ and stir to mix the system evenly and degas it completely. Then add 0.3-0.8 parts of photoinitiator and continue stirring. Irradiate with ultraviolet light for 3-5 minutes under nitrogen protection to obtain the prepolymer. Step 2: Add 0.05-0.2 parts of chain transfer agent, 0.1-0.5 parts of thickening coupling agent, 0.1-0.5 parts of antioxidant, 0.1-0.2 parts of leveling agent, and 0.13-0.25 parts of crosslinking agent to the prepolymer prepared in Step 1 in sequence, and continue mixing for 20-60 minutes under stirring conditions to obtain the adhesive solution; Step 3: Apply the adhesive prepared in Step 2 through a die onto the release surface of a heavy release film with a thickness of 50-100 μm and a peel force of 20-40 gf / in. Control the wet film thickness so that the final cured OCA adhesive layer thickness is 50-300 μm. Then, coat the adhesive layer with a light release film with a thickness of 40-80 μm and a peel force of 3-8 gf / in. Remove air by pressure rollers and heat under a UV light source with a total energy of 2800-3500 mJ / cm². 2 The optical adhesive composition is obtained by irradiation and curing.

[0008] The soft monomer is at least one of ethyl acrylate, isooctyl acrylate, isodecanyl acrylate, lauryl acrylate, and butyl acrylate; The hard monomer is at least one of methyl acrylate, vinyl acetate, isopropyl methacrylate, isobutyl methacrylate, methyl methacrylate, and ethyl methacrylate. The functional monomers include at least one of acrylic acid, acrylamide, glycidyl methacrylate, hydroxyethyl acrylate, and hydroxybutyl acrylate.

[0009] The thiourea monomer includes at least one of 1,3-diallyl-2-thiourea, 1-allyl-3-(pyridin-3-yl)thiourea, and 1-allyl-3-(4-benzylphenyl)thiourea; The photoinitiator is at least one of benzophenone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, methyl benzoylformate, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and α-hydroxyisobutyroxene.

[0010] The chain transfer agent is at least one selected from dodecyl mercaptan, ethanethiol, butanethiol, 1,4-bis(3-mercaptobutyrooxy)butane, 2-mercaptoethanol, isooctyl 3-mercaptopropionate, and benzenethiol.

[0011] The antioxidant is selected from at least one of butylated hydroxytoluene, tert-butylhydroquinone, and butylated hydroxyanisole.

[0012] The thickening coupling agent is at least one of dimethyldimethoxysilane, vinyltriethoxysilane, methyltriethoxysilane, and vinyltrimethoxysilane.

[0013] The leveling agent is at least one of BYK-358N, BYK370, and BYK371.

[0014] The crosslinking agent includes at least one of ethylene glycol dimethacrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol dimethacrylate, and trimethylolpropane triacrylate.

[0015] The light-diffusing material is at least one of 2-phenoxyethyl acrylate, benzyl acrylate, benzyl methacrylate, 2,2,2-trifluoroethyl methacrylate, nano alumina, nano zirconium dioxide, polymethylsilsesquioxane, and 2-(phenylthio)ethyl acrylate.

[0016] Preferably, the homogenizing material is composed of 2-phenoxyethyl acrylate and polymethylsilsesquioxane in a mass ratio of 0.5-2:0.5-2.

[0017] More preferably, the homogenizing material is composed of 2-phenoxyethyl acrylate, polymethylsilsesquioxane and 2-(phenylthio)ethyl acrylate in a mass ratio of 0.5-2:0.5-2:0.1-0.5.

[0018] The design concept of this invention is based on the synergy of optical and structural performance. Building upon existing optical adhesive systems, it achieves a balance between high transmittance and high light uniformity by meticulously constructing a cross-linked network with refractive index matching and introducing a controllable scattering field. First, a main chain framework is constructed using soft monomers, hard monomers, and functional monomers in combination with sulfur-containing structural monomers. This provides a stable carrier for optical control while ensuring the transparency, adhesive strength, and durability of the adhesive layer. Second, a light-monopolating material is introduced during the prepolymerization stage to form localized high-refractive-index regions within the adhesive layer. By adjusting the overall refractive index and interface transitions, multi-interface reflections and interference fringes are reduced, improving display uniformity from the source. Furthermore, microparticle-type light-monopolating components with specific particle sizes and refractive index differences are added to form uniformly distributed micro-scattering centers within the adhesive layer. Multiple small-angle scattering smooths backlight and pixel brightness fluctuations, while controlling particle size, content, and distribution to improve haze without causing significant whitening or resolution degradation. Ultimately, by combining different types of refractive index regulating components with scattering components in specific proportions, a multi-layered light homogenization system is formed, which combines precise refractive index matching, high refractive index focusing, and micro-scattering diffusion. While maintaining high transmittance and good adhesion, it achieves moderate haze and significantly improved brightness uniformity, providing an optical adhesive solution for mid-to-high-end display modules that combines clarity and visual comfort.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects: 1) While maintaining the high transparency and good adhesion of the optical adhesive, this invention improves the brightness uniformity of the display screen and reduces bright spots and dark areas by combining refractive index matching and bulk scattering, thus significantly improving the overall viewing experience.

[0020] 2) This invention achieves a more reasonable haze level and a smoother light field distribution with similar dosage by synergistic design of multiple light-averaging components compared to a single light-averaging system, thus balancing light-averaging effect and image clarity.

[0021] 3) The homogenizing component of this invention has good compatibility with the matrix network and does not significantly affect the rheology and curing behavior of the system. It can be directly matched with existing optical adhesive production and bonding processes, which facilitates large-scale preparation and long-term stable mass production. Detailed Implementation

[0022] Some material parameters and their sources: Nano-alumina, average particle size: 30nm, purity: 99%, crystal form: γ phase, color: white.

[0023] Nano-zirconia, particle size: 20nm, specific surface area: 20-50m² 2 / g, Crystal form: monoclinic.

[0024] Polymethylsilsesquioxane, grade: KMP-590, brand: Shin-Etsu Chemical, Japan.

[0025] All other raw materials used in the embodiments and comparative examples of this invention are commercially available products.

[0026] Example 1 A method for preparing an optical adhesive composition with a light-averaging effect is as follows, in parts by weight: Step 1: Add 40 parts lauryl acrylate, 8 parts isooctyl acrylate, 20 parts isobutyl methacrylate, 15 parts glycidyl methacrylate, 10 parts 1-allyl-3-(4-benzylphenyl)thiourea, and 0.5 parts homogenizing material to a sealed reaction vessel with a stirrer. Heat to 30°C and stir to ensure the system is mixed evenly and fully degassed. Then add 0.5 parts benzophenone and continue stirring. Irradiate with ultraviolet light at a wavelength of 365 nm for 3 minutes under nitrogen protection to obtain the prepolymer. Step 2: Add 0.1 parts of 1,4-bis(3-mercaptobutyryloxy)butane, 0.3 parts of vinyltrimethoxysilane, 0.25 parts of butylated hydroxytoluene, 0.15 parts of BYK-358N, 0.08 parts of ethylene glycol dimethacrylate, and 0.12 parts of trimethylolpropane triacrylate to the prepolymer prepared in Step 1 in sequence. Continue mixing for 40 minutes under stirring to obtain the adhesive solution. Step 3: Apply the adhesive prepared in Step 2 through a die onto the release surface of a heavy release film with a thickness of 80µm and a peel force of 35gf / in. Control the wet film thickness so that the final cured OCA adhesive layer thickness is 180µm. Then, coat the adhesive layer with a light release film with a thickness of 60µm and a peel force of 6gf / in. Remove air by a pressure roller and heat under a 365nm ultraviolet light source with a total energy of 3200mJ / cm². 2 The optical adhesive composition is obtained by irradiation and curing.

[0027] The light-diffusing material is 2-phenoxyethyl acrylate.

[0028] Example 2 The preparation method of an optical adhesive composition with a light-diffusing effect is basically the same as that in Example 1, except that the light-diffusing material is benzyl acrylate.

[0029] Example 3 The preparation method of an optical adhesive composition with a light-averaging effect is basically the same as that in Example 1, except that the light-averaging material is benzyl methacrylate.

[0030] Example 4 The preparation method of an optical adhesive composition with a light-diffusing effect is basically the same as that in Example 1, except that the light-diffusing material is 2,2,2-trifluoroethyl methacrylate.

[0031] Example 5 The preparation method of an optical adhesive composition with a light-uniforming effect is basically the same as that in Example 1, except that the light-uniforming material is nano-alumina.

[0032] Example 6 The preparation method of an optical adhesive composition with a light-averaging effect is basically the same as that in Example 1, except that the light-averaging material is nano-zirconia.

[0033] Example 7 The preparation method of an optical adhesive composition with a light-averaging effect is basically the same as that in Example 1, except that the light-averaging material is polymethylsilsesquioxane.

[0034] Example 8 The preparation method of an optical adhesive composition with a light-averaging effect is basically the same as that in Example 1, except that the light-averaging material is composed of 2-phenoxyethyl acrylate and polymethylsilsesquioxane in a mass ratio of 1:1.

[0035] Example 9 The preparation method of an optical adhesive composition with a light-diffusing effect is basically the same as that in Example 1, except that the light-diffusing material is composed of 2,2,2-trifluoroethyl methacrylate and nano-zirconia in a mass ratio of 1:1.

[0036] Example 10 The preparation method of an optical adhesive composition with a light-averaging effect is basically the same as that in Example 1, except that the light-averaging material is composed of 2-phenoxyethyl acrylate and 2,2,2-trifluoroethyl methacrylate in a mass ratio of 1:1.

[0037] Example 11 The preparation method of an optical adhesive composition with a light-averaging effect is basically the same as that in Example 1, except that the light-averaging material is composed of 2-phenoxyethyl acrylate, polymethylsilsesquioxane and 2-(phenylthio)ethyl acrylate in a mass ratio of 1:1:0.3.

[0038] Comparative Example 1 The preparation method of an optical adhesive composition with a light-averaging effect is basically the same as that in Example 1, except that the light-averaging material is not added.

[0039] Test Example 1 Total transmittance and haze tests; The optical adhesive compositions prepared in each embodiment and comparative example were sandwiched between two pieces of optical-grade glass, ensuring the sample surface was clean and free of bubbles. Testing was performed according to GB / T 2410-2008 "Determination of transmittance and haze of transparent plastics"; the instrument was preheated and zero-point and full-scale calibrations were performed according to the standard; the incident luminous flux was measured without a sample and recorded as I0; the bonded sample was placed in the sample holder, and the total transmitted luminous flux through the sample was recorded as I0. t ; Calculate the total transmittance T using the formula: T = (I t / I0)×100%; Read the values ​​in both total transmission and scattered transmission modes of the instrument and calculate the haze H (%).

[0040] Each group was tested three times, and the average value was taken. The test results are shown in Table 1.

[0041] Table 1

[0042] Test Example 2 Brightness uniformity test: A uniform 7-inch display module was selected, and the white field was illuminated. The glass cover, the optical adhesive compositions prepared in each embodiment and comparative example, and the display module were sequentially bonded together, eliminating air bubbles and ensuring uniform curing conditions. In a darkroom environment, the ambient illuminance was controlled below 1 lx. The display module was illuminated in the darkroom, displaying a pure white image, and preheated for 30 minutes to stabilize it. Nine test points were arranged on the display panel surface using a nine-point method (four corners, four sides center, and screen center, totaling nine test points). The luminance meter probe was held at a fixed distance and perpendicular to the screen, and the luminance value (L) at each point was measured sequentially. i (Unit: cd / m) 2 Record the maximum brightness L. max Minimum brightness L min The brightness uniformity U is calculated using the following formula: U (%) = (L min / L max )×100%; Each group was tested three times, and the average value was taken. The relevant test data are summarized in Table 2.

[0043] Table 2

[0044] First, comparing Comparative Example 1 with Examples 1-7, Comparative Example 1 did not introduce any light-monopolizing material. Although it had the highest total transmittance and a haze of only 0.8%, and the light passed through in a basically straight line, it had almost no ability to adjust scattering. The difference between backlight and pixel brightness was directly reflected on the observation surface, resulting in a brightness uniformity of only 80.4%, which easily led to bright spots, dark areas and glare. Examples 1-4 introduce aromatic (meth)acrylates such as 2-phenoxyethyl acrylate and benzyl acrylate, which are high-refractive-index monomers. They can enter the adhesive layer network and improve and finely adjust the overall refractive index of the optical adhesive to make it closer to glass / ITO, reducing the interfacial refractive index difference and multiple reflections. This maintains high light transmittance while introducing slight haze. Examples 5-7 form uniformly distributed scattering centers in the adhesive layer using nano-alumina, nano-zirconia, and polymethylsilsesquioxane. While sacrificing some light transmittance, the haze is increased to 5.6%-7.8%, which more effectively disperses local brightness peaks. Therefore, the overall brightness uniformity of each example is better than that of Comparative Example 1, indicating that a single light-diffusing material can improve display uniformity with moderate scattering. Secondly, under the premise of the same total addition amount, Example 8 simultaneously introduces 2-phenoxyethyl acrylate and polymethylsilsesquioxane to form a binary combination of high refractive index monomer and organosilicon diffusion particles. 2-phenoxyethyl acrylate increases the refractive index of the matrix through aromatic rings, reduces interface reflection loss and suppresses interference fringes, ensuring the high transmittance level of the adhesive layer. Polymethylsilsesquioxane provides micron-sized and moderately numerous scattering centers inside the adhesive layer, converting direct light into multiple small-angle scatterings, which flattens the local brightness difference and increases haze, falling just within the appropriate range of both significant light uniformity and excessive whitening. Therefore, the brightness uniformity jumps to 92.1%, which is significantly higher than any single light uniformity material example. This shows that the two mechanisms of refractive index matching and bulk scattering produce a significant synergistic effect in this combination. Finally, Example 11 further introduces sulfur-containing 2-(phenylthio)ethyl acrylate, a high-refractive-index specialty monomer, based on Example 8. This constructs a network with a higher and more continuous refractive index within the adhesive layer, resulting in a more refined refractive index matching of the matrix. Simultaneously, it achieves a similar effect of micro-focusing and redistribution of light at the microscale. Combined with the stable micro-scattering field provided by polymethylsilsesquioxane, on the one hand, the haze is increased to 9.3% at a similar transmittance (93.1%), further enhancing the smoothing ability of backlight and pixel brightness fluctuations. On the other hand, it avoids the significant decrease in transmittance or obvious haze caused by simply increasing the particle content, thereby further improving the brightness uniformity to 94.0%.

Claims

1. A method for preparing an optical adhesive composition with a homogenizing effect, characterized in that, The method is as follows: Step 1: Heat and stir the soft monomer, hard monomer, functional monomer, thiourea monomer and homogenizing material together to make the system uniform and fully degas. Then add the photoinitiator, continue stirring, and irradiate with ultraviolet light under nitrogen protection to obtain the prepolymer. Step 2: Add chain transfer agent, thickening coupling agent, antioxidant, leveling agent and crosslinking agent to the prepolymer prepared in step 1 in sequence, and continue mixing under stirring conditions to obtain adhesive solution; Step 3: Apply the adhesive prepared in Step 2 to the release surface of the heavy release film, control the wet film thickness, then cover the adhesive layer with the light release film, remove air by pressure rollers, and cure under ultraviolet light source to obtain the optical adhesive composition. The homogenizing material is 2 Phenoxyethyl acrylate, polymethylsilsesquioxane and 2 (Phenylthio)ethyl acrylate is composed of (phenylthio)ethyl acrylate in a mass ratio of 0.5-2:0.5-2:0.1-0.

5.

2. The method for preparing the optical adhesive composition with uniform light distribution effect as described in claim 1, characterized in that, The method is as follows, by weight: Step 1: Add 35-60 parts of soft monomer, 10-30 parts of hard monomer, 10-20 parts of functional monomer, 5-15 parts of thiourea monomer and 0.3-1 parts of homogenizing material to a sealed reaction vessel with a stirrer. Heat to 25-35℃ and stir to mix the system evenly and degas it completely. Then add 0.3-0.8 parts of photoinitiator and continue stirring. Irradiate with ultraviolet light for 3-5 minutes under nitrogen protection to obtain the prepolymer. Step 2: Add 0.05-0.2 parts of chain transfer agent, 0.1-0.5 parts of thickening coupling agent, 0.1-0.5 parts of antioxidant, 0.1-0.2 parts of leveling agent, and 0.13-0.25 parts of crosslinking agent to the prepolymer prepared in Step 1 in sequence, and continue mixing for 20-60 minutes under stirring conditions to obtain the adhesive solution; Step 3: Apply the adhesive prepared in Step 2 through a die onto the release surface of a heavy release film with a thickness of 50-100µm and a peel force of 20-40gf / in. Control the wet film thickness so that the final cured OCA adhesive layer thickness is 150-200µm. Then, coat the adhesive layer with a light release film with a thickness of 40-80µm and a peel force of 3-8gf / in. Remove air by pressure rollers and heat under a UV light source with a total energy of 2800-3500mJ / cm². 2 The optical adhesive composition is obtained by irradiation and curing.

3. The method for preparing the optical adhesive composition with uniform light effect as described in claim 1 or 2, characterized in that, The soft monomer is at least one of ethyl acrylate, isooctyl acrylate, isodecanyl acrylate, lauryl acrylate, and butyl acrylate; the hard monomer is at least one of methyl acrylate, vinyl acetate, isopropyl methacrylate, isobutyl methacrylate, methyl methacrylate, and ethyl methacrylate; the functional monomer includes at least one of acrylic acid, acrylamide, glycidyl methacrylate, hydroxyethyl acrylate, and hydroxybutyl acrylate.

4. The method for preparing the optical adhesive composition with uniform light effect as described in claim 1 or 2, characterized in that, The thiourea monomer includes at least one of 1,3-diallyl-2-thiourea, 1-allyl-3-(pyridin-3-yl)thiourea, and 1-allyl-3-(4-benzylphenyl)thiourea; the photoinitiator is at least one of benzophenone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, methyl benzoylformate, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and α-hydroxyisobutyroxene.

5. The method for preparing the optical adhesive composition with uniform light effect as described in claim 1 or 2, characterized in that, The chain transfer agent is at least one selected from dodecyl mercaptan, ethanethiol, butanethiol, 1,4-bis(3-mercaptobutyryloxy)butane, 2-mercaptoethanol, isooctyl 3-mercaptopropionate, and benzenethiol; the antioxidant is at least one selected from dibutylhydroxytoluene, tert-butylhydroquinone, and butyl hydroxyanisole.

6. The method for preparing the optical adhesive composition with uniform light effect as described in claim 1 or 2, characterized in that, The tackifying coupling agent is at least one of dimethyldimethoxysilane, vinyltriethoxysilane, methyltriethoxysilane, and vinyltrimethoxysilane; the leveling agent is at least one of BYK-358N, BYK370, and BYK371; and the crosslinking agent includes at least one of ethylene glycol dimethacrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol dimethacrylate, and trimethylolpropane triacrylate.

7. An optical adhesive composition with a light-uniforming effect, characterized in that, It is prepared by the preparation method described in any one of claims 1-6.

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