Resin having thermal crosslinking structure, method for preparing same, optical adhesive composition, microlens, and method for preparing same

Abstract

The present application belongs to the technical field of high polymer materials, and relates to a resin with a thermal crosslinking structure, a preparation method thereof, an optical glue composition, a microlens and a preparation method thereof. The resin is synthesized by mixing a hydroxyl-containing acrylate monomer A, an epoxy acrylate monomer B and a carboxyl-containing acrylate monomer C according to a specific molar ratio, dropping into a reaction solvent, performing a copolymerization reaction at a specific temperature and adding a free radical initiator. The resin gives the photoresist good reflow characteristics, can maintain a stable form at high temperature, and further prepares an optical glue composition with excellent optical performance and durability. The optical glue composition not only has excellent optical performance, but also performs well in terms of thermal stability, chemical resistance and aging resistance. After spin coating, pre-baking, exposure, development and then heating and reflow, a microlens with a good shape can be formed.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, and relates to a resin with a thermal cross-linking structure and its preparation method, an optical adhesive composition, a microlens and its preparation method. Background Technology

[0002] Optical system materials in existing imaging optical systems such as fax machines, electronic copiers, and solid-state imaging elements utilize microlenses with diameters ranging from 1 μm to 100 μm. Microlens arrays, formed by regularly arranging these microlenses, can effectively improve light extraction efficiency within display devices, increase screen brightness, and reduce power consumption. In the formation of such microlenses, a known method involves forming a pattern equivalent to a microlens, then melting and flowing the pattern through heat treatment, and directly using it as a microlens.

[0003] Based on the above-mentioned formation principle, existing Chinese Patent Document 1 (Publication No.: CN111352301A, Publication Date: June 30, 2020) discloses a thermosensitive resin composition and a method for forming microlenses. This resin composition, when heated to a temperature below 140°C, generates sufficient thermal melt flow, thus forming microlenses with good shapes. Furthermore, this resin composition exhibits high sensitivity and good storage stability, while the formed microlenses possess chemical resistance and high transparency. However, the refractive index of this resin composition is somewhat reduced, failing to meet the requirements of high refractive index applications. Additionally, the resin contains aromatic side chains, which may pose a risk of yellowing under UV light exposure.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a resin with a thermal cross-linking structure and its preparation method, an optical adhesive composition, a microlens and its preparation method.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] In a first aspect, the present invention provides a resin having a thermally crosslinked structure, the general formula of which is as follows:

[0008]

[0009] In formula (1), R1 is methyl or H, R2 and R4 represent hydrocarbon or alkoxy groups, R3 is an epoxy group, R5 and R6 are each independently hydrogen atoms, halogen atoms, C1-C4 alkyl groups or C1-C4 fluorinated alkyl groups, * represents a bond with the main chain, x = 0-30 mol%, y = 40-60 mol%, z = 20-40 mol%.

[0010] Specifically, when R2 and R4 represent aliphatic hydrocarbon groups, alkyl groups are preferred. The alkyl group is preferably a C1-C20 alkyl group, and more preferably a C1-C6 alkyl group. The alkyl group can be straight-chain, branched, or cyclic, but is preferably straight-chain. Additionally, the alkyl group may have substituents or not, for example: methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, hexadecyl, octadecyl, eicosyl, isopropyl, isobutyl, dibutyl, tributyl, isopentyl, neopentyl, 1-methylbutyl, isohexyl, 2-ethylhexyl, 2-methylhexyl, cyclohexyl, cyclopentyl, 2-norbornyl, etc.; wherein, methyl or ethyl is preferred.

[0011] Specifically, R3 is an epoxy group, including any one of the following formulas (1-1) to (1-6):

[0012]

[0013]

[0014] Wherein, * represents the linking site; R7 and R8 are any one of H, C1 to C6 alkyl, C1 to C6 fluoroalkyl, or alkenyl.

[0015] Specifically, the above-mentioned resin with a thermal cross-linking structure has a molecular weight of 7,000 to 10,000, preferably 7,500 to 9,500.

[0016] Secondly, the present invention also provides a method for preparing a resin with a thermally crosslinked structure, comprising: mixing a hydroxyl-containing acrylate monomer A, an epoxy acrylate monomer B, and a carboxyl-containing acrylate monomer C to perform a copolymerization reaction; wherein, the copolymerization reaction specifically comprises:

[0017] At a reaction temperature of 60–70°C, hydroxyl-containing acrylate monomer A, epoxy acrylate monomer B, and carboxyl-containing acrylate monomer C are mixed in a molar ratio of (0–30):(40–60):(20–40) and added dropwise to the reaction solvent to carry out the polymerization reaction, while a free radical initiator is added simultaneously for synthesis.

[0018] Specifically, the reaction solvents include halogenated hydrocarbons such as chlorobutane, bromohexane, dichloroethane, 1,6-dibromohexane, and chlorobenzene; saturated carboxylic acid esters such as ethyl acetate, n-butyl acetate, isobutyl acetate, and methyl propionate; ketones such as acetone, methyl ethyl ketone, 4-methyl-2-pentanone, and 2-heptanone; ethers such as tetrahydrofuran, dimethoxyethanes, and diethoxyethanes; and alcohols such as methanol, ethanol, 1-propanol, 2-propanol, and 4-methyl-2-pentanol. These solvents can be used alone or in combination of two or more.

[0019] Specifically, the free radical initiator includes one or more of the following: azobisisobutyronitrile (AIBN), azobisisoheptanenitrile, azobisisobutylamidine hydrochloride, cyclohexanone peroxide, benzoyl peroxide, and persulfate; preferably azobisisobutyronitrile (AIBN).

[0020] Furthermore, the general structural formula of hydroxyl-containing acrylate monomer A is as follows:

[0021]

[0022] Based on the structure shown in formula (2) above, the hydroxyl-containing acrylate monomer A can be any of the structures shown in formulas (2-1) to (2-8):

[0023]

[0024] Furthermore, the general structural formula of epoxy acrylate monomer B is as follows:

[0025]

[0026] Based on the structure shown in formula (3) above, epoxy acrylate monomer B can be any of the structures shown in formulas (3-1) to (3-6):

[0027]

[0028] Furthermore, the general structural formula of the carboxyl acrylate monomer C is as follows:

[0029]

[0030] Based on the structure shown in formula (4) above, the carboxyl acrylate monomer C can be any of the structures shown in formula (4-1) to formula (4-4):

[0031]

[0032] It should be noted that: (1) The hydroxyl-containing acrylate monomer A and the carboxyl-containing acrylate monomer C were chosen to be non-aryl monomers because the introduction of aryl groups would reduce the toughness and impact strength of the resin. The rigid structure of the aromatic ring would make the molecular chain of the resin more compact, resulting in reduced flexibility and making it more prone to brittle fracture. In addition, the aromatic ring would also bring the risk of yellowing due to UV aging. Therefore, the inventors of this application abandoned acrylate monomers with aryl groups.

[0033] (2) Hydroxyl groups can react with epoxy groups in other monomers to form ether bonds, thereby enhancing the crosslinking degree of the resin. This crosslinking network structure endows the resin with excellent thermal stability and mechanical strength, allowing it to maintain good morphology during high-temperature treatment and improving adhesion. Epoxy acrylate monomers are highly reactive and undergo ring-opening reactions with hydroxyl groups to form stable polymer chains, which not only promotes the crosslinking of the resin but also improves its heat resistance and chemical resistance. The carboxyl groups of carboxyl acrylate monomers C can form stable coordination bonds with metal ions such as zirconium ions, stably dispersing nano-zirconia particles in the resin. This not only helps to improve the transparency of the optical adhesive composition but also enhances its absorption of light of specific wavelengths, thereby increasing the refractive index of the optical adhesive composition. The introduction of carboxyl groups also helps to increase the polarity of the resin, thereby improving its compatibility with high-refractive-index nano-zirconia particles.

[0034] (3) The introduction of precursor liquid particles significantly increases the refractive index of the optical adhesive composition, thereby increasing the contrast between the exposed and unexposed areas and facilitating the formation of fine patterns. In addition, nanoscale particles can effectively scatter incident light, reducing the penetration depth of light and thus improving resolution.

[0035] It is important to emphasize that this application, by optimizing the monomer ratio, namely by mixing hydroxyl-containing acrylate monomer A, epoxy acrylate monomer B, and carboxyl-containing acrylate monomer C in a molar ratio of (0-30):(40-60):(20-40) and adding an appropriate free radical initiator, can inhibit the free radical polymerization of the resin, reduce photo-induced aging, and improve adhesion.

[0036] Thirdly, the present invention provides an optical adhesive composition with a thermal reflux effect, comprising at least the following raw materials by weight: 10-20 parts of the above-mentioned resin with a thermal crosslinking structure, 3-10 parts of precursor liquid particles, 1-5 parts of photoinitiator, 0.01-0.5 parts of surfactant, and 40-80 parts of solvent.

[0037] Specifically, the precursor liquid particles are selected from one or two of ZrO2, TiO2, In2O3, Al2O3, ZnO or SnO2, preferably 3 to 8 parts.

[0038] Furthermore, the precursor liquid particles have an average particle size of 5–22 nm and a refractive index of 1.8–2.0. The precursor liquid particles in this invention are ligand-modified, with acrylate ligands attached to their surface, and are purchased from companies such as JSR and Nippon Shokubai.

[0039] The inventors of this application would like to emphasize that only when the mass ratio of the precursor liquid particles to the resin with the thermal cross-linking structure is within the range of (2-5):(4-15) can the introduction of the resin with the thermal cross-linking structure be guaranteed not to affect the dispersibility of the precursor liquid particles in the optical adhesive, thereby reducing nanoparticle aggregation and improving the transmittance and refractive index of the composition.

[0040] Specifically, the photoinitiator includes oxime ester photoinitiators, which include any one or at least two of OXE-01, OXE-02, OXE-E12, or OXPI-405. OXE-01 is 1-(4-phenylthiophenyl)-octane-1,2-dione-2-benzoic acid oxime ester (CAS No.: 253585-83-0), and OXE-02 is 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazole-3-yl]acetophenone 1-(O-acetyl oxime) (CAS No.: 478556-66-0).

[0041] Specifically, the surfactants include F-114, F-553, F-562, and F-570 from DIC; FC-135 and FC-170C from 3M; S-211, S-221, S-231, and S-242 from AGC; and BYK-300, BYK-301, BYK-302, BYK-306, BYK-310, BYK-313, BYK-320, BYK-366P, BYK-368P, BYK-370, BYK-375, BYK-377, BYK-378, and / or BYK-394 from BYK. Surfactants can improve the wettability of the developer on the photoresist by reducing the interfacial tension between the developer and the photoresist, thereby promoting the contact and dissolution of the developer and the photoresist. In addition, surfactants can improve leveling, ensure uniform film thickness, and enhance adhesion. These combined effects improve the developing effect, making the developing process smoother and more efficient.

[0042] Specifically, the solvent is an alcohol such as 3-methoxy-1-butanol and diacetone alcohol; a ketone such as acetone, methyl ethyl ketone, cyclohexanone, and N-methyl-2-pyrrolidone; a glycol ether such as diethylene glycol ethyl methyl ether, propylene glycol methyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, triethylene glycol monomethyl ether, and triethylene glycol monoethyl ether; and ethyl acetate, butyl acetate, ethyl lactate, 3-methoxybutyl acetate, 3-methoxy-3-butyl acetate, and propylene glycol methyl ether acetate.

[0043] Furthermore, the present invention provides a microlens formed by thermal reflow of the aforementioned optical adhesive composition with thermal reflow effect, which has a good lens shape and a diameter of 1–100 μm. Moreover, the microlens exhibits excellent chemical resistance and high light transmittance, and can be used in solid-state imaging elements, display element microlens arrays, array planarization film patterns, protective film patterns, insulating film patterns, etc., but is not limited thereto; it is particularly suitable for microlens arrays.

[0044] Specifically, the above-mentioned optical adhesive composition undergoes spin coating, pre-baking, exposure, and development, followed by heating and reflow to form a well-shaped microlens. The specific preparation process is as follows:

[0045] Step 1: First, the optical adhesive composition is coated onto a substrate (semiconductor substrate, silicon nitride substrate, quartz substrate, glass substrate, or glass substrate with ITO film) using a spin coater, coating machine, roller coating, slot coating, or other coating methods. Then, it is vacuum desolventized for 120 seconds and pre-baked to form a coating film. The film thickness is typically 2–10 μm, preferably 2–4 μm. The pre-baking temperature is 70–100°C and the baking time is 0.3–10 min.

[0046] Step 2: Then, the coating is exposed to obtain a film with the target pattern. The film is then irradiated with ultraviolet light through a photomask, so that the film cured by ultraviolet light comes into contact with the developing solution to dissolve the unexposed areas. After development, the pattern is washed with water and dried with nitrogen. The developing solution can be an aqueous solution of alkali metal hydroxides such as potassium hydroxide and sodium hydroxide, or an aqueous solution of quaternary ammonium hydroxides such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, and choline, or an alkaline aqueous solution such as an aqueous solution of amines such as ethanolamine, propylamine, and ethylenediamine.

[0047] Step 3: Finally, heat the film at 90–150°C for 3–20 minutes to allow it to melt and flow, utilizing its own surface tension to form microlenses through thermal reflow. The lowest temperature at which a lens-like pattern can be formed is defined as the thermal reflow temperature.

[0048] Finally, the present invention also provides an image display device for the above-mentioned microlens array, which includes liquid crystal display devices, organic light-emitting diodes, flexible displays, etc., but is not limited thereto, and may also include all known image display devices that can be applied to the present technical field.

[0049] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0050] 1) This invention, through the rational design of the structure and molar ratio of hydroxyl-containing acrylate monomers, epoxy acrylate monomers, and carboxyl-containing acrylate monomers, prepares a resin structure with a thermal reflow effect. The preparation method is simple, low-cost, stable in performance, highly operable, and reproducible. It can form hemispherical microlenses, which exhibit excellent transparency, chemical resistance, and long-term reliability. This resin structure effectively prevents yellowing of photoresist caused by ultraviolet radiation, ensuring the stability of performance after long-term use. Combined with high-refractive-index nano-zirconia particles, the material's performance is further enhanced, forming a novel negative optical adhesive. It not only possesses excellent optical properties but also demonstrates outstanding performance in thermal stability, chemical resistance, and aging resistance, showing broad application prospects.

[0051] 2) The thermally cross-linked resin structure provided by this invention endows the photoresist with excellent reflow characteristics, allowing it to maintain a stable morphology at high temperatures and enabling the preparation of optical adhesive compositions with superior optical performance and durability. The addition of nano-zirconia particles can increase the refractive index of the optical adhesive composition to 1.6, meeting the requirements of high-refractive-index optical components. Simultaneously, the uniform dispersion of nanoparticles helps improve the transmittance of the optical adhesive composition in the visible light band and also enhances its anti-aging and anti-yellowing properties. Detailed Implementation

[0052] Exemplary embodiments will now be described in detail. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples consistent with some aspects of the invention as detailed in the appended claims.

[0053] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to embodiments.

[0054] Preparation Example

[0055] This preparation example provides a method for preparing a resin with a thermally crosslinked structure. Hydroxyacrylate monomer A, epoxy acrylate monomer B, and carboxyl acrylate monomer C are mixed in a molar ratio of 10:40:20 and then added dropwise to a n-butyl acetate solvent for copolymerization. Hydroxyacrylate monomer A uses the structure shown in formula (2-2), epoxy acrylate monomer B uses the structure shown in formula (3-1), and carboxyl acrylate monomer C uses the structure shown in formula (4-1). The reaction temperature is 70°C, and azobisisobutyronitrile (AIBN) is added simultaneously to synthesize a resin (M-1) with a thermally crosslinked structure and a molecular weight of 7000.

[0056] Based on the above preparation principle, resins (M-2), (M-3), (M-4), (M-5), and (M-6) with thermal crosslinking structures were also prepared. The selection and molar ratio of hydroxyl acrylate monomer A, epoxy acrylate monomer B, and carboxyl acrylate monomer C, as well as the molecular weights of the different resins obtained, are shown in Table 1 below.

[0057] Table 1. Raw material selection, molar ratio, and molecular weight of resins (M-1) to (M-6)

[0058]

[0059] Comparative Example 1

[0060] This comparative example provides a method for preparing a resin, wherein hydroxyl-containing acrylate monomer A and carboxyl-containing acrylate monomer C are mixed in a molar ratio of 20:25 and then added dropwise to a n-butyl acetate solvent for copolymerization; wherein the hydroxyl-containing acrylate monomer A adopts the structure shown in formula (2-5) and the carboxyl-containing acrylate monomer C adopts the structure shown in formula (4-2), the reaction temperature is 70℃, and azobisisobutyronitrile (AIBN) is added simultaneously to synthesize resin (D-1) with a molecular weight of 7500.

[0061] Comparative Example 2

[0062] This comparative example provides another method for preparing the resin. Hydroxy acrylate monomer A and epoxy acrylate monomer B are mixed in a molar ratio of 20:40 and then added dropwise to a n-butyl acetate solvent for copolymerization. Hydroxy acrylate monomer A uses the structure shown in formula (2-5), and epoxy acrylate monomer B uses the structure shown in formula (3-5). The reaction temperature is 70℃, and azobisisobutyronitrile (AIBN) is added simultaneously to synthesize the resin (D-2) with a molecular weight of 8000.

[0063] Example 1

[0064] This embodiment provides an optical adhesive composition (I) with a thermal reflux effect, which includes the following raw materials by weight: 10 parts of resin (M-1) with a thermal crosslinking structure, 3 parts of precursor liquid particles, 2 parts of photoinitiator, 0.1 parts of surfactant, and 50 parts of solvent.

[0065] The precursor liquid particles are selected from ZrO2 with an average particle size of 6 nm and a refractive index of 1.85; and the mass ratio of the precursor liquid particles to the resin (M-1) with a thermal cross-linking structure is 3:10.

[0066] The photoinitiator selected is OXE-01;

[0067] The surfactant used is BYK-310 manufactured by BYK Corporation;

[0068] The solvent used is propylene glycol methyl ether acetate.

[0069] The optical adhesive composition (I) with thermal reflow effect prepared in this embodiment is spin-coated, pre-baked, exposed, developed, and then heated and reflowed to form a microlens; wherein the heating temperature is 90°C.

[0070] Example 2

[0071] This embodiment provides an optical adhesive composition (II) with a thermal reflux effect, which includes the following raw materials by weight: 10 parts of resin (M-2) with a thermal crosslinking structure, 5 parts of precursor liquid particles, 5 parts of photoinitiator, 0.1 parts of surfactant, and 50 parts of solvent.

[0072] The precursor liquid particles are selected from ZnO with an average particle size of 12nm and a refractive index of 1.85; and the mass ratio of the precursor liquid particles to the resin (M-2) with a thermal cross-linking structure is 5:10.

[0073] The photoinitiator selected is OXE-01;

[0074] The surfactant used is BYK-310 manufactured by BYK Corporation;

[0075] The solvent used is propylene glycol methyl ether acetate.

[0076] The optical adhesive composition (II) with thermal reflow effect prepared in this embodiment is spin-coated, pre-baked, exposed, developed, and then heated and reflowed to form a microlens; wherein the heating temperature is 130°C.

[0077] Example 3

[0078] This embodiment provides an optical adhesive composition (III) with a thermal reflux effect, comprising the following raw materials by weight: 15 parts of resin (M-3) with a thermal crosslinking structure, 5 parts of precursor liquid particles, 5 parts of photoinitiator, 0.2 parts of surfactant, and 50 parts of solvent.

[0079] The precursor liquid particles are TiO2 with an average particle size of 18 nm and a refractive index of 1.9; and the mass ratio of the precursor liquid particles to the resin (M-3) with a thermal cross-linking structure is 5:15.

[0080] The photoinitiator selected is OXE-01;

[0081] The surfactant used is BYK-320 manufactured by BYK Corporation;

[0082] The solvent used is propylene glycol methyl ether acetate.

[0083] The optical adhesive composition (III) with thermal reflow effect prepared in this embodiment is spin-coated, pre-baked, exposed, developed, and then heated and reflowed to form a microlens; wherein the heating temperature is 140°C.

[0084] Example 4

[0085] This embodiment provides an optical adhesive composition (IV) with a thermal reflow effect, comprising the following raw materials by weight: 15 parts of a resin (M-4) with a thermal crosslinking structure, 5 parts of precursor liquid particles, 4 parts of a photoinitiator, 0.3 parts of a surfactant, and 50 parts of a solvent.

[0086] The precursor liquid particles are TiO2 with an average particle size of 18 nm and a refractive index of 1.9; and the mass ratio of the precursor liquid particles to the resin (M-4) with a thermal cross-linking structure is 5:15.

[0087] The photoinitiator selected is OXE-02;

[0088] The surfactant used is BYK-320 manufactured by BYK Corporation;

[0089] The solvent used is propylene glycol methyl ether acetate.

[0090] The optical adhesive composition (IV) with thermal reflow effect prepared in this embodiment is spin-coated, pre-baked, exposed, developed, and then heated and reflowed to form a microlens; wherein the heating temperature is 140°C.

[0091] Example 5

[0092] This embodiment provides an optical adhesive composition (V) with a thermal reflux effect, comprising the following raw materials by weight: 20 parts of resin (M-5) with a thermal crosslinking structure, 8 parts of precursor liquid particles, 4 parts of photoinitiator, 0.4 parts of surfactant, and 50 parts of solvent.

[0093] The precursor liquid particles are a mixture of SnO2 and TiO2 with an average particle size of 1:1, an average particle size of 20 nm, and a refractive index of 2.0; and the mass ratio of the precursor liquid particles to the resin (M-5) with a thermal crosslinking structure is 2:5.

[0094] The photoinitiator selected is OXE-02;

[0095] The surfactant used is BYK-320 manufactured by BYK Corporation;

[0096] The solvent used is 3-methoxybutylacetic acid ester.

[0097] The optical adhesive composition (V) with thermal reflow effect prepared in this embodiment is spin-coated, pre-baked, exposed, developed, and then heated and reflowed to form a microlens; wherein the heating temperature is 150°C.

[0098] Example 6

[0099] This embodiment provides an optical adhesive composition (VI) with a thermal reflux effect, comprising the following raw materials by weight: 20 parts of resin (M-6) with a thermal crosslinking structure, 10 parts of precursor liquid particles, 3 parts of photoinitiator, 0.5 parts of surfactant, and 50 parts of solvent.

[0100] The precursor liquid particles are a mixture of ZrO2 and TiO2 with a mass ratio of 1:1, an average particle size of 20 nm, and a refractive index of 2.0; and the mass ratio of the precursor liquid particles to the resin (M-6) with a thermal crosslinking structure is 5:4.

[0101] The photoinitiator selected is OXE-02;

[0102] The surfactant used is BYK-370 manufactured by BYK Corporation;

[0103] The solvent used is 3-methoxybutylacetic acid ester.

[0104] The optical adhesive composition (VI) with thermal reflow effect prepared in this embodiment is spin-coated, pre-baked, exposed, developed, and then heated and reflowed to form a microlens; wherein the heating temperature is 150°C.

[0105] Comparative Example 3

[0106] Based on Example 1, the difference from Example 1 is that the optical adhesive composition (VII) provided in this comparative example uses the resin (D-1) obtained in Comparative Example 1; the optical adhesive composition (VII) is spin-coated, pre-baked, exposed, developed, and then heated; wherein, the heating temperature is 130°C.

[0107] Comparative Example 4

[0108] Based on Example 1, the difference from Example 1 is that the optical adhesive composition (eight) provided in this comparative example uses the resin (D-2) obtained in Comparative Example 2; the optical adhesive composition (eight) is spin-coated, pre-baked, exposed, developed, and then heated; wherein, the heating temperature is 130°C.

[0109] Comparative Example 5

[0110] Based on Example 1, the difference from Example 1 is that the optical adhesive composition (IX) provided in this comparative example uses bisphenol A type epoxy resin as its resin; the optical adhesive composition (IX) is spin-coated, pre-baked, exposed, developed, and then heated; wherein, the heating temperature is 130°C.

[0111] Comparative Example 6

[0112] Based on Example 3, the difference from Example 3 is that the optical adhesive composition (x) provided in this comparative example has a precursor liquid particle weight of 1 part; the optical adhesive composition (x) is spin-coated, pre-baked, exposed, developed, and then heated; wherein, the heating temperature is 140°C.

[0113] Comparative Example 7

[0114] Based on Example 3, the difference from Example 3 is that the optical adhesive composition (XI) provided in this comparative example has a precursor liquid particle weight of 15 parts; the optical adhesive composition (XI) is spin-coated, pre-baked, exposed, developed, and then heated; wherein, the heating temperature is 140°C.

[0115] Comparative Example 8

[0116] Based on Example 1, the difference from Example 1 is that the optical adhesive composition (twelve) provided in this comparative example is subjected to spin coating, pre-baking, exposure, development, and then heating; wherein, the heating temperature is 80°C, which is not in the aforementioned temperature range of 90-150°C.

[0117] Comparative Example 9

[0118] Based on Example 2, the difference from Example 2 is that the optical adhesive composition (thirteen) provided in this comparative example is subjected to spin coating, pre-baking, exposure, development, and then heating; wherein, the heating temperature is 200°C, which is not in the aforementioned temperature range of 90-150°C.

[0119] Comparative Example 10

[0120] Based on Example 2, the difference from Example 2 is that the optical adhesive composition (fourteen) provided in this comparative example uses resin (D-3); D-3 is different from D-2 prepared in Comparative Example 2 in that the hydroxyl acrylate monomer A is made with the structure shown in the following formula (5), and is then spin-coated, pre-baked, exposed, developed, and then heated.

[0121]

[0122] Here, the applicant needs to explain that the process of preparing microlenses based on the above-mentioned optical adhesive composition in this invention is as follows:

[0123] Step 1: First, the optical adhesive composition is coated onto a silicon nitride substrate. The optical adhesive composition can be coated by other coating methods such as spin coater, coating machine, roller coating, slot coating, etc. Then, it is pre-baked at 85°C for 1.5 minutes to form a 3μm coating film.

[0124] Step 2: Then, the coating is exposed to obtain a film with the target pattern. A mask with a line / gap pattern of 1-50 μm is irradiated with 365 nm ultraviolet light to bring the film cured by ultraviolet light into contact with the developer to dissolve the unexposed areas for development. After development, the pattern is washed with water containing tetramethylammonium hydroxide and dried with nitrogen.

[0125] Step 3: Finally, heat the developed silicon nitride substrate at 90-150°C for 3-20 minutes to allow the adhesive film to melt and flow, thereby forming a photocured pattern through thermal reflow, which can be directly used as a microlens.

[0126] Performance testing

[0127] (1) Adhesion: The coating was cut into 100-grid sections using a cross-cutting tool and a utility knife. 3M transparent tape was then applied to the cut grid, ensuring it adhered firmly to the coating surface and the grid areas. The extent and degree of coating peeling on the substrate were visually assessed to determine the ASTM rating. ASTM ratings are as follows: 5B – Smooth cut edges with no peeling at grid edges; 4B – Peeling area within the grid area ≤ 5%; 3B – Peeling area within the grid area > 5%–15%; 2B – Peeling area within the grid area > 15%–35%; 1B – Peeling area within the grid area > 35%–65%; 0B – Peeling area within the grid area > 65%.

[0128] (2) Refractive index:

[0129] A 5cm×5cm×1.5μm (width×length×thickness) adhesive film was formed on the surface of a silicon nitride substrate. Except for the absence of a mask, the sample was prepared according to the method for forming the curing pattern. An ellipsometer was used for testing and fitting, and the wavelength corresponding to the refractive index value was selected as 550nm.

[0130] (3) Light transmittance:

[0131] Except for not using a mask, the samples were prepared according to the method for forming the curing pattern, and the transmittance of the cured single film (unpatterned surface) in the visible light range of 380nm to 800nm ​​was measured by a UV-Vis spectrophotometer (U-3900Hitachi).

[0132] (4) Reflowability: Samples are prepared according to the method for forming the cured pattern, using different heating temperatures in step 3. ◎ indicates reflowability and good microlens shape; ○ indicates reflowability and poor microlens shape; × indicates no reflowability.

[0133] (5) Yellowing Index YI: Xenon lamp aging test conditions: 0.55W / m 2 Irradiation at 340nm, 40℃, 20%-30%RH, and 300-800nm ​​light conditions for 20h + 4h, then stored at room temperature (without light) for 10 cycles, totaling 240h. Measurements were taken using a UV-Vis spectrophotometer according to ASTM E313 standard.

[0134] To further verify the effectiveness of the technical solution provided by the present invention, performance tests were conducted on the photocurable patterns formed in Examples 1-6 and Comparative Examples 3-9, and the results are shown in Table 1 below:

[0135] Table 1. Test results of the photocured patterns formed in Examples 1-6 and Comparative Examples 3-9

[0136] Test Project Adhesion Refractive index / % transmittance / % reflux Yellowing Index Example 1 5B 1.5882 98.8 ◎ 0.6 Example 2 5B 1.6054 98.5 ◎ 0.5 Example 3 5B 1.5921 98.3 ◎ 0.6 Example 4 5B 1.5973 98.2 ◎ 0.7 Example 5 5B 1.6063 98.0 ◎ 0.6 Example 6 4B 1.6132 98.0 ◎ 0.8 Comparative Example 3 4B 1.5895 98.7 ◎ 1.2 Comparative Example 4 3B 1.5889 98.7 × 1.5 Comparative Example 5 2B 1.5935 97.9 ○ 1.6 Comparative Example 6 4B 1.5512 98.8 ◎ 1.7 Comparative Example 7 2B 1.6315 96.7 × 1.9 Comparative Example 8 3B 1.6049 96.5 × 2.1 Comparative Example 9 3B 1.6054 96.2 × 2.5 Comparative Example 10 2B 1.6051 97.1 ○ 8.1

[0137] As shown in Table 1 above, the yellowing index of the photocured patterns formed in Examples 1 to 6 is less than 0.8. The photocured patterns corresponding to Examples 1 to 5 have high refractive index and light transmittance, and the adhesion can reach 5B. At the same time, reflow can occur, and the formed lens shape is good with high precision and integrity. Example 6 uses non-hydroxyl acrylic monomer A resin (M-6), with an adhesion of 4B and other excellent properties.

[0138] Conversely, the adhesion of Comparative Examples 3–9 was 2–4B, and the yellowing index was greater than 1. Specifically:

[0139] Comparative Example 3 used resin (D-1) prepared without epoxy acrylate monomer B, and Comparative Example 4 used resin (D-2) prepared without carboxyl-containing acrylate monomer C, which affected adhesion and reflow properties, respectively. Comparative Example 5 used bisphenol A type epoxy resin, which showed poor adhesion and poor reflow shape.

[0140] In Comparative Examples 6 and 7, the amount of precursor liquid particles added was either too little or too much, falling outside the range of 3 to 10 parts as required above. This affected the refractive index and light transmittance, resulting in poor overall performance of the corresponding photocured patterns.

[0141] The heating temperature of Comparative Example 8 was too low, and it did not reach the reflow temperature, so no reflow occurred. The heating temperature of Comparative Example 9 was too high, and the optical adhesive composition formed a network structure and was directly set. In Comparative Example 10, the resin composition prepared with aromatic rings produced more severe yellowing, with a yellowing index greater than 8, and the adhesion was also affected.

[0142] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention.

[0143] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A resin having a thermally cross-linked structure, characterized in that, Its general structural formula is as follows: Equation (1) In formula (1), R1 is methyl or H, R2 represents an aliphatic hydrocarbon group, R4 represents a hydrocarbon group or alkoxy group, R3 is an epoxy group, and R5 and R6 are each independently hydrogen atom, halogen atom, C1~C4 alkyl group or C1~C4 fluorinated alkyl group. * indicates a key associated with the main chain; x÷(x+y+z)=0~30mol%, y÷(x+y+z)=40~60mol%, z÷(x+y+z)=20~40mol%.

2. The resin with a thermally crosslinked structure according to claim 1, characterized in that, The molecular weight of the resin is 7000~10000.

3. The resin with a thermally crosslinked structure according to claim 1, characterized in that, The epoxy group includes any one of the following formulas (1-1) to (1-6): Equation (1-1) Equation (1-2) Equation (1-3) Equation (1-4) Equation (1-5) Equation (1-6) Wherein, * represents the linking site; R7 and R8 are any one of H, C1 to C6 alkyl, C1 to C6 fluoroalkyl, or alkenyl.

4. A method for preparing a resin with a thermally crosslinked structure according to any one of claims 1-3, characterized in that, Hydroxyl acrylate monomer A, epoxy acrylate monomer B, and carboxyl acrylate monomer C are mixed and added dropwise to a reaction solvent for copolymerization. A free radical initiator is then added to synthesize a resin with a thermal crosslinking structure.

5. The method for preparing the resin with a thermally cross-linked structure according to claim 4, characterized in that, The general structural formula of the hydroxyl-containing acrylate monomer A is as follows (2), the general structural formula of the epoxy acrylate monomer B is as follows (3), and the general structural formula of the carboxyl-containing acrylate monomer C is as follows (4): Equation (2) Equation (3) Equation (4) Wherein, R1 is methyl or H, R2 represents an aliphatic hydrocarbon group, R4 represents a hydrocarbon group or alkoxy group, R3 is an epoxy group, and R5 and R6 are independently hydrogen atoms, halogen atoms, C1~C4 alkyl groups or C1~C4 fluorinated alkyl groups, respectively.

6. An optical adhesive composition with a thermal reflow effect, characterized in that, The product comprises, by weight, at least the following raw materials: 10-20 parts of the resin having a thermal crosslinking structure as described in any one of claims 1 to 3, 3-10 parts of precursor liquid particles, 1-5 parts of photoinitiator, 0.01-0.5 parts of surfactant, and 40-80 parts of solvent.

7. The optical adhesive composition with thermal reflow effect according to claim 6, characterized in that, The precursor liquid particles are selected from one or two of ZrO2, TiO2, In2O3, Al2O3, ZnO or SnO2.

8. The optical adhesive composition with thermal reflow effect according to claim 6, characterized in that, The photoinitiator includes oxime ester photoinitiators, which include any one or at least two of OXE-01, OXE-02, OXE-E12 or OXPI-405.

9. A microlens, characterized in that, The optical adhesive composition with thermal reflow effect as described in any one of claims 6 to 8 is formed by thermal reflow.

10. A method for preparing a microlens as described in claim 9, characterized in that, The optical adhesive composition with thermal reflow effect according to any one of claims 6 to 8 is coated on a substrate and pre-baked to obtain a coating film; then the coating film is exposed to obtain an adhesive film with a target pattern; then the adhesive film is developed and rinsed, and finally heated and reflowed at 90 to 150°C to form a microlens.

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