Low-refractive optical resin

Abstract

The present application provides a low refractive index optical resin, which comprises a polysiloxane composition and an organic solvent composition, wherein the polysiloxane composition comprises a polysiloxane and a hydroxyalkyl silane monomer, and the organic solvent composition comprises a high-boiling solvent with a boiling point higher than 180℃ and a low-boiling solvent with a boiling point lower than 150℃; wherein the amount of the organic solvent composition used is 50 to 120 parts by weight per 10 parts by weight of the polysiloxane composition. The low refractive index optical resin can be used in micro light emitting diode displays to achieve the effect of improving light extraction efficiency, and can maintain good optical properties at sufficient thickness.

Description

Technical Field

[0001] This invention relates to a low-refractive-index optical resin, and more particularly to a low-refractive-index optical resin for use in micro-LED displays. Background Technology

[0002] As self-emissive electroluminescent displays gradually replace non-self-emissive liquid crystal displays (LCDs), the function of light-emitting diodes (LEDs) has shifted from providing backlights for LCDs to serving as self-emissive display pixels. However, when LEDs are used as display pixels, in addition to the need to shrink their size to the micrometer level to form so-called micro-LED displays, the light-emitting chips are generally formed directly into display pixels by mass transfer to the substrate after epitaxy. This makes it impossible to individually set microlenses for each light-emitting chip to adjust the light pattern and increase the light emission efficiency, making it difficult to achieve the theoretical value of luminous efficiency. Furthermore, although the internal quantum efficiency of micro-LEDs can easily reach over 90%, the large difference in refractive index between the light-emitting chips made of high-refractive-index inorganic materials and the external air, without the ability to use microlenses with specific curvatures to change the light emission angle, easily leads to total internal reflection, resulting in extremely low external quantum efficiency (only about 10%).

[0003] Therefore, it is known that by filling and covering the surface of a micro-LED display with a low-refractive-index layer lower than that of the LED chip, total internal reflection between the LED chip and the air interface can be reduced, thereby improving light extraction efficiency. However, since these micron-sized LED chips occupy a very small area in the overall display area and pixels, there is a height difference between the LED chip and the substrate in each pixel. Therefore, the coated low-refractive-index layer must also have excellent filling properties to further avoid flickering and poor visual appearance under ambient light caused by excessive refractive index difference between numerous tiny LED chips and the surrounding substrate.

[0004] Various methods for implementing low-refractive-index optical resin layers have been disclosed in known technologies. For example, a low-refractive-index optical resin layer is formed by coating hollow inorganic particles with a suitable binder. However, to achieve the ideal refractive index, a large number of hollow inorganic particles need to be added. A large number of inorganic particles increases the haze of the low-refractive-index layer, affecting its optical properties, and is prone to cracking during curing. Fluoropolymers have also been disclosed as materials for low-refractive-index optical resin layers; however, their low surface energy results in poor adhesion between the low-refractive-index optical resin layer and the surface of the micro-LED display, and their hardness and durability are also poor. Furthermore, in waveguide optics, it has been disclosed to use siloxane compositions to cure at temperatures above 150°C on the surface of optical guide components to form a porous coating with nanoscale pores, achieving a coating with dielectric properties and low refractive index. However, when this siloxane composition is used for coating optical displays, the porous structure makes it difficult to obtain a sufficiently thick and crack-free cured coating while maintaining low refractive index and low yellowing.

[0005] Therefore, there is a need for a low-refractive-index optical resin that can be used in micro-LED displays to improve light extraction efficiency while maintaining good optical properties with sufficient coating thickness. Summary of the Invention

[0006] The purpose of this invention is to provide a low-refractive-index optical resin that can be used in micro-LED displays to improve light extraction efficiency. The low-refractive-index optical resin of this invention exhibits almost no yellowing after curing, does not affect the hue and chroma of displays when used, and can achieve sufficient coating thickness without cracking.

[0007] The low-refractive-index optical resin of the present invention comprises a polysiloxane composition and an organic solvent composition, wherein the polysiloxane composition comprises a polysiloxane and a hydroxyalkylsilane monomer, and the organic solvent composition comprises a high-boiling-point solvent with a boiling point above 180°C and a low-boiling-point solvent with a boiling point below 150°C; wherein the amount of the organic solvent composition used is 50 to 120 parts by weight per 10 parts by weight of the polysiloxane composition.

[0008] In the low-refractive-index optical resin of the present invention, the organic solvent composition comprises 97 to 80 weight percent of a high-boiling-point solvent and 3 to 20 weight percent of a low-boiling-point solvent, and preferably comprises 95 to 85 weight percent of a high-boiling-point solvent and 5 to 15 weight percent of a low-boiling-point solvent.

[0009] The low-refractive-index optical resin of the present invention can be cured between 50°C and 170°C, preferably between 60°C and 160°C. The yellowness index of the cured low-refractive-index optical resin layer is not greater than 1.5, preferably not greater than 1, and the refractive index is between 1.1 and 1.35, preferably between 1.2 and 1.3.

[0010] The surface roughness Sa of the low-refractive-index optical resin layer formed after curing of the low-refractive-index optical resin of the present invention is between 5 μm and 50 μm.

[0011] The low-refractive-index optical resin of the present invention has a viscosity between 2 and 20 mPa·s at 25°C and a surface tension between 20 and 40 dyne / cm.

[0012] In the low-refractive-index optical resin of the present invention, the surface tension of the high-boiling-point solvent in the organic solvent composition is between 30 dyne / cm and 38 dyne / cm, and the surface tension of the low-boiling-point solvent is between 23 dyne / cm and 30 dyne / cm.

[0013] In one embodiment of the low-refractive-index optical resin of the present invention, the high-boiling-point solvent of the organic solvent composition may partially include a medium-boiling-point organic solvent with a boiling point between 150°C and 180°C and a surface tension between 20 dyne / cm and 30 dyne / cm, wherein the content of the medium-boiling-point organic solvent in the high-boiling-point solvent is 25 to 45% by weight.

[0014] In the low refractive index optical resin of the present invention, 10 to 70 parts by weight of hydroxyalkylsilane monomer are used for every 10 parts by weight of polysiloxane in the polysiloxane composition.

[0015] In the low refractive index optical resin of the present invention, the polysiloxane in the polysiloxane composition is obtained by hydrolysis and condensation or co-condensation of silane monomers, and the weight-average molecular weight (Mw) is between 5,000 and 100,000 g / mol.

[0016] In the low refractive index optical resin of the present invention, the structure of the hydroxyalkylsilane monomer is as shown in formula (I):

[0017]

[0018] R1, R2, R3, R4 and R5 are each independently selected from C1-C10 alkyl and C5-C20 aryl groups, and may be optionally monosubstituted, disubstituted or trisubstituted by C1-C10 alkyl or C3-C10 alicyclic groups; R6 is an alkyl chain from C6 to C30, and contains 1 to 3 double or triple bonds thereon, and contains at least one hydroxyl group; n is an integer between 0 and 10, and the boiling point of the hydroxyalkylsilane monomer is between 80 and 180 °C.

[0019] The foregoing summary is intended to provide a simplified overview of this disclosure, enabling the reader to gain a basic understanding. This summary is not a complete overview of the invention and is not intended to identify key components of the embodiments or define the scope of the invention. Upon reviewing the following embodiments, those skilled in the art will readily understand the basic spirit of the invention and the technical means and implementation methods employed. Detailed Implementation

[0020] To make the disclosure of this invention more detailed and complete, illustrative descriptions of embodiments and specific examples of this invention are provided below; however, these are not the only forms of implementing or utilizing the specific examples of this invention. The embodiments disclosed below can be combined or substituted with each other where advantageous, and other embodiments can be added to one embodiment without further description or explanation.

[0021] The advantages, features, and technical methods of the present invention will be more readily understood by referring to exemplary embodiments, and the invention may be implemented in different forms. Therefore, it should not be understood as limited to the embodiments set forth herein. Rather, the embodiments provided will enable those skilled in the art to more thoroughly and completely convey the scope of the invention, and the invention will be defined only by the appended claims.

[0022] Unless otherwise defined, all terms (including technical and scientific terms) and proper nouns used below shall, in substance, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains, and terms defined, for example, in commonly used dictionaries shall be understood to have the same meaning as the content of the relevant field, and shall not be interpreted in an overly idealized or overly formal sense unless explicitly defined below.

[0023] The purpose of this invention is to provide a low-refractive-index optical resin comprising a polysiloxane composition and a solvent composition. The low-refractive-index optical resin layer formed after curing has a refractive index between 1.1 and 1.35, thereby improving light extraction efficiency. It also has a thickness suitable for filling micro-LED display components while maintaining good crack resistance, exhibiting almost no yellowing and not affecting the color tone and chroma of the display.

[0024] The low refractive index optical resin of the present invention comprises a polysiloxane composition and an organic solvent composition, wherein the polysiloxane composition comprises a polysiloxane and a hydroxyalkylsilane monomer, and the organic solvent composition comprises a high-boiling-point solvent with a boiling point above 180°C and a low-boiling-point solvent with a boiling point below 150°C; wherein the amount of the organic solvent composition used is 50 to 120 parts by weight of the polysiloxane composition for every 10 parts by weight.

[0025] When the low-refractive-index optical resin of the present invention is heated and cured at 50°C to 170°C, the polysiloxane in the polysiloxane composition of the resin begins to cure due to the directional volatilization dominated by the organic solvent composition with a boiling point gradient, thereby homogenizing the vaporization of hydroxyalkylsilanes to form a uniform porous polysiloxane layer. This allows the coating to maintain its low refractive index even with sufficient coating thickness, without cracking or yellowing. In one embodiment of the low-refractive-index optical resin of the present invention, the organic solvent composition comprises 97 to 80 weight percent of a high-boiling-point solvent and 3 to 20 weight percent of a low-boiling-point solvent. In a preferred embodiment, the organic solvent composition comprises 95 to 85 weight percent of a high-boiling-point solvent and 5 to 15 weight percent of a low-boiling-point solvent.

[0026] The low-refractive-index optical resin of the present invention can be coated using coating methods commonly used in this technical field, such as roller coating, doctor blade coating, dip coating, spin coating, and inkjet coating, and cured at a temperature between 50°C and 170°C, preferably between 60°C and 160°C, to form a low-refractive-index optical resin layer with a yellowness index of not more than 1.5, preferably not more than 1, and a refractive index between 1.1 and 1.35, preferably between 1.2 and 1.3. The low-refractive-index optical resin of the present invention can achieve a cured thickness of more than 1 μm after coating. Furthermore, to better achieve the vaporization of the aforementioned hydroxyalkylsilane, in a preferred embodiment of the low-refractive-index optical resin of the present invention, multiple coating layers can be applied as needed to achieve the required thickness. During the heating and curing process, the polysiloxane molecular chains of the low refractive index optical resin of the present invention are aligned with the specific diffusion and volatilization conditions of the solvent composition. Therefore, even if the low refractive index optical resin is coated in multiple layers, it is a macroscopically continuous coating film, and its optical properties such as refractive index or yellowness index are almost unaffected by the interlayer interface.

[0027] The surface roughness Sa of the low-refractive-index optical resin layer formed after curing is between 5 μm and 50 μm. If the surface roughness Sa is too low, the surface energy of the film is insufficient, which is not conducive to subsequent encapsulation or other functional layer coating processes; if the surface roughness Sa is too high, the formed low-refractive-index optical resin layer will have excessive haze.

[0028] When using the low-refractive-index optical resin of the present invention on the surface of a micro-light-emitting diode display component, inkjet coating is preferred as it facilitates coating with stepped surfaces. In this embodiment, the viscosity of the low-refractive-index optical resin of the present invention at 25°C is preferably between 2 and 20 mPa·s. If the viscosity at 25°C is lower than 2 mPa·s, it is not conducive to producing stable, continuous, and well-supported droplets during inkjet coating; if the viscosity is higher than 20 mPa·s, the fluidity during inkjet coating is reduced.

[0029] Furthermore, the low-refractive-index optical resin of the present invention can form a low-refractive-index optical resin layer of sufficient thickness on the micro-light-emitting diode display component, and can maintain good crack resistance. The surface tension of the low-refractive-index optical resin of the present invention is between 20 and 40 dyne / cm. If the surface tension of the low-refractive-index optical resin is less than 20 dyne / cm, it is not conducive to maintaining stable droplets at the coating nozzle during inkjet coating, and it is not easy to recoat the surface; if the surface tension is greater than 40 dyne / cm, the flowability of the low-refractive-index optical resin is poor, and it is easy for the low-refractive-index optical resin to crystallize after curing, thereby affecting the transparency and adhesion of the low-refractive-index optical resin layer.

[0030] In a preferred embodiment of the low-refractive-index optical resin of the present invention, the low-refractive-index optical resin layer formed after curing has a light transmittance of not less than 91% and a yellowness index of not more than 1.5, preferably not more than 1, so it does not affect the hue and chroma of the display component.

[0031] In the low-refractive-index optical resin of the present invention, the surface tension of the high-boiling-point solvent in the organic solvent composition is between 30 dyne / cm and 38 dyne / cm, and the surface tension of the low-boiling-point solvent is between 23 dyne / cm and 30 dyne / cm.

[0032] In the low-refractive-index optical resin of the present invention, the high-boiling-point solvent of the organic solvent composition may be, for example, but not limited to, ester solvents such as dimethyl succinate, dimethyl glutarate, γ-butyrolactone, or ethylene glycol butyl ether acetate; ether solvents such as ethylene glycol monobutyl ether, triethylene glycol butyl ether, diethylene glycol monoethyl ether, or tetraethylene glycol dimethyl ether; or pyrrole solvents such as 1-phenylpyrrolidone, 2-pyrrolidone, or N-methylpyrrolidone, or a combination thereof, but not limited thereto. In a preferred embodiment of the low-refractive-index optical resin of the present invention, the high-boiling-point solvent may be one or a combination of γ-butyrolactone, diethylene glycol monoethyl ether, or N-methylpyrrolidone.

[0033] In the low-refractive-index optical resin of the present invention, the low-boiling-point solvent may be, for example, but not limited to, alcohol solvents or alcohol ether solvents. Alcohol solvents may be, for example, but not limited to, one or a combination of n-pentanol, isoamyl alcohol, 2-ethylbutanol, 2-methyl-2-butanol, or 2,2-dimethylpropanol. Alcohol ether solvents may be, for example, but not limited to, one or a combination of ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, propylene glycol methyl ether, or propylene glycol methyl ether acetate. In a preferred embodiment of the low-refractive-index optical resin of the present invention, the low-boiling-point solvent is one or a combination of 2-ethylbutanol, 2-methyl-2-butanol, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, or propylene glycol monomethyl ether.

[0034] In the low-refractive-index optical resin of the present invention, the high-boiling-point solvent of the organic solvent composition may partially include a medium-boiling-point organic solvent with a boiling point between 150°C and 180°C and a surface tension between 20 dyne / cm and 30 dyne / cm, wherein the content of the medium-boiling-point organic solvent in the high-boiling-point solvent is 25 to 45% by weight.

[0035] In the low-refractive-index optical resin of the present invention, suitable medium-boiling-point organic solvents may be, for example, but not limited to, alcohol solvents or alcohol ether solvents. Alcohol solvents may be, for example, but not limited to, one or a combination of 3-methoxybutanol, 4-methyl-1-pentanol, or diacetone alcohol. Alcohol ether solvents may be, for example, but not limited to, one or a combination of propylene glycol n-propyl ether, ethylene glycol monotert-butyl ether, or ethylene glycol monobutyl ether. In a preferred embodiment of the low-refractive-index optical resin of the present invention, the medium-boiling-point solvent is one or a combination of 3-methoxybutanol, 4-methyl-1-pentanol, or a combination thereof. In the low-refractive-index optical resin of the present invention, the amount of polysiloxane and hydroxyalkylsilane monomer used in the polysiloxane composition is 10 to 70 parts by weight of hydroxyalkylsilane monomer per 10 parts by weight of polysiloxane.

[0036] In the low-refractive-index optical resin of the present invention, the polysiloxane composition can be prepared by hydrolysis and condensation or co-condensation of silane monomers. Suitable silane monomers may be, for example, but not limited to, one or a combination of tetramethoxysilane, tetraethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, trimethylmethoxysilane, vinyltrimethoxysilane, propylene oxide propyltrimethoxysilane, or phenyltrimethoxysilane. The weight-average molecular weight (Mw) of the polysiloxane is between 5,000 g / mol and 100,000 g / mol, and preferably between 20,000 g / mol and 50,000 g / mol.

[0037] In the low-refractive-index optical resin of the present invention, the hydroxyalkylsilane monomer of the polysiloxane composition may be a monomer having the structure shown in formula (I):

[0038]

[0039] In this embodiment, R1, R2, R3, R4, and R5 are each independently selected from C1 to C10 alkyl and C5-C20 aryl groups, and may be optionally mono-, di-, or tri-substituted by C1-C10 alkyl or C3-C10 alicyclic groups; R6 is a C6-C30 alkyl chain, which may contain one to three double or triple bonds and at least one hydroxyl group; n is an integer between 0 and 10. In a preferred embodiment of the low refractive index optical resin of the present invention, in the structure of the hydroxyalkylsilane monomer as shown in formula (I), R6 is a C10-C20 alkyl chain, and the boiling point of the hydroxyalkylsilane monomer is preferably between 80 and 180°C.

[0040] In the low refractive index optical resin of the present invention, the polysiloxane composition may also include a short-chain polysiloxane, such as a bis(hydroxy)-oligomeric (dialkylsiloxane) with 1 to 20 silicon atoms, which can enhance the mechanical properties of the low refractive index optical resin during curing.

[0041] The polysiloxane composition used in the low refractive index optical resin of the present invention is preferably a commercially available product, such as “IOC-572-JO1”, “IOC-573-J2”, “IOC-573-J6” or “IOC-573-J4” manufactured by NAGASE & CO., LTD. of Japan.

[0042] In other embodiments of the low-refractive-index optical resin of the present invention, additives such as curing catalysts, antistatic agents, ultraviolet absorbers, antioxidants, surface modifiers, leveling agents, and defoamers may be added as needed to provide different functional properties.

[0043] The following embodiments are used to further illustrate the present invention, but the content of the present invention is not limited thereto.

[0044] Example

[0045] Example 1

[0046] A low-refractive-index optical resin with a surface tension of 37 dyne / cm and a viscosity of 7.6 mPa·s at 25°C was obtained by thoroughly mixing 10 g of polysiloxane composition (IOC-573-J2, purchased from NAGASE & CO., LTD., Japan), 5 g of propylene glycol monomethyl ether (PGME), and 85 g of N-methylpyrrolidone (NMP).

[0047] The low-refractive-index optical resin was inkjet-coated onto the surface of a glass substrate and then cured at 150°C to form a low-refractive-index optical resin layer with a thickness of 1.75 micrometers and a refractive index of 1.25, which was free of cracks. The optical properties of the aforementioned low-refractive-index optical resin layer were measured using the optical testing methods described later, and the measurement results are listed in Table 1 below.

[0048] The aforementioned inkjet coating and curing process was repeated twice on the obtained low-refractive-index optical resin layer to form a low-refractive-index optical resin layer with a thickness of 3.82 micrometers and a refractive index of 1.22, which was free of cracks. The optical properties of the aforementioned low-refractive-index optical resin layer were measured according to the optical testing methods described later, and the measurement results are listed in Table 1 below.

[0049] Example 2

[0050] A low-refractive-index optical resin with a surface tension of 24 dyne / cm and a viscosity of 12.5 mPa·s at 25°C was obtained by thoroughly mixing 15 g of polysiloxane composition (IOC-573-J4, purchased from NAGASE & CO., LTD., Japan), 7 g of propylene glycol monomethyl ether (PGME), and 80 g of diethylene glycol diethyl ether (DEMEE).

[0051] The low-refractive-index optical resin was inkjet-coated onto the surface of a glass substrate and then cured at 80°C to form a low-refractive-index optical resin layer with a thickness of 3.18 micrometers and a refractive index of 1.26, which was free of cracks. The optical properties of the aforementioned low-refractive-index optical resin layer were measured using the optical testing methods described later, and the measurement results are listed in Table 1 below.

[0052] The obtained low-emissivity optical resin layer was subjected to the aforementioned inkjet coating and curing process once to form a low-refractive-index optical resin layer with a thickness of 3.28 micrometers and a refractive index of 1.26, which was free of cracks. The optical properties of the aforementioned low-emissivity layer were measured using the optical testing methods described later, and the measurement results are listed in Table 1 below.

[0053] Example 3

[0054] In Example 2, the low-refractive-index optical resin was inkjet-coated onto the surface of a glass substrate and then cured at 150°C to form a low-refractive-index optical resin layer with a thickness of 2.82 micrometers and a refractive index of 1.24, which was free of cracks. The optical properties of the aforementioned low-refractive-index optical resin layer were measured using the optical testing methods described later, and the measurement results are listed in Table 1 below.

[0055] The aforementioned inkjet coating and curing process was repeated five times on the obtained low-refractive-index optical resin layer to form a low-refractive-index optical resin layer with a thickness of 8.02 micrometers and a refractive index of 1.23, which showed no cracks. The optical properties of the aforementioned low-refractive-index optical resin layer were measured using the optical testing methods described later, and the measurement results are listed in Table 1 below.

[0056] Example 4

[0057] A low-refractive-index optical resin with a surface tension of 24 dyne / cm and a viscosity of 8.1 mPa·s at 25 °C was obtained by thoroughly mixing 10 g of polysiloxane composition (IOC-573-J6, purchased from NAGASE & CO., LTD., Japan), 7 g of propylene glycol monomethyl ether (PGME), 54 g of diethylene glycol diethyl ether (DEMEE), and 29 g of propylene glycol n-propyl ether (PnP).

[0058] The low-refractive-index optical resin was inkjet-coated onto the surface of a glass substrate and then cured at 80°C to form a low-refractive-index optical resin layer with a thickness of 3.26 micrometers and a refractive index of 1.26, which was free of cracks. The optical properties of the aforementioned low-refractive-index optical resin layer were measured using the optical testing methods described later, and the measurement results are listed in Table 1 below.

[0059] The aforementioned inkjet coating and curing process was repeated five times on the obtained low-refractive-index optical resin layer to form a low-refractive-index optical resin layer with a thickness of 7.47 micrometers and a refractive index of 1.26, which showed no cracks. The optical properties of the aforementioned low-refractive-index optical resin layer were measured using the optical testing methods described later, and the measurement results are listed in Table 1 below.

[0060] Comparative Example 1

[0061] A low-refractive-index optical resin was obtained by thoroughly mixing 10 g of polysiloxane composition (IOC-572-J1, purchased from NAGASE & CO., LTD., Japan), 30 g of propylene glycol monomethyl ether (PGME), and 60 g of ethylene glycol (EG).

[0062] The optical resin was inkjet-coated onto the surface of a glass substrate and then cured at 100°C to form a low-refractive-index optical resin layer with a thickness of 2.8 micrometers and a refractive index of 1.25. The optical properties of the aforementioned low-refractive-index optical resin layer were measured using the optical testing methods described later, and the measurement results are listed in Table 1 below.

[0063] Optical testing methods

[0064] Light transmittance measurement: The light transmittance was measured using an NDH-2000 haze meter (manufactured by Nippon Denshoku Kogyo Co., Ltd.) according to the measurement method of JIS K7361.

[0065] Haze measurement: The haze was measured using an NDH-2000 haze meter (manufactured by Nippon Denshoku Kogyo Co., Ltd.) according to the measurement method of JIS K7136.

[0066] Refractive index measurement: The refractive index was measured using a CM-26d spectrophotometer (manufactured by Konica Minolta Inc., Japan) in accordance with the measurement method of JISK0062:1992 [Method for measurement of refractive index of chemical products].

[0067] Measurement of L*, a*, b* and yellowness index (YI): L*, a* and b* were measured using a CDM-08 colorimeter (manufactured by Kunling Technology Co., Ltd., Taiwan, China) according to the CIE-Lab definition; and the yellowness index was determined according to the measurement method of ASTM E313.

[0068] Table 1: Optical quality measurement results of low refractive index optical resin layers in Examples 1 to 4 and Comparative Example 1

[0069]

[0070] The low-refractive-index optical resins prepared in Examples 1 to 4 of this invention, after curing on a glass substrate, form low-refractive-index optical resin layers with thicknesses ranging from 1.75 to 8.02 micrometers, yellowness indices ranging from 0.4 to 0.8, and refractive indices ranging from 1.22 to 1.26, respectively, and without cracking. Furthermore, the desired thickness of the low-refractive-index optical resin layer can be achieved through multiple coating and curing processes, and optical properties such as refractive index or yellowness index are almost unaffected by interlayer interfaces. As a comparative example, Comparative Example 1, which uses a large amount of the low-boiling-point solvent propylene glycol monomethyl ether, has a low-refractive-index optical resin layer with a refractive index of 1.25, but a yellowness index as high as 2.2, making it unsuitable for coating micro-LED displays. Therefore, when the low-refractive-index optical resins of Examples 1 to 4 are used for coating micro-LED displays, sufficient coating thickness can be achieved without cracking, further improving light extraction efficiency, and there is almost no yellowing after curing, thus not affecting the hue and chroma of the display.

[0071] Although the present invention has been disclosed above by way of embodiments, it is not intended to limit the present invention. Any person skilled in the art can make various modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A low-refractive-index optical resin, comprising: A polysiloxane composition comprising a polysiloxane and a hydroxyalkylsilane monomer; and An organic solvent composition comprising a high-boiling-point solvent with a boiling point above 180°C and a low-boiling-point solvent with a boiling point below 150°C. in, The polysiloxane is prepared by hydrolysis and condensation or co-condensation of silane monomers; The structure of the hydroxyalkylsilane monomer is shown in formula (I): R1, R2, R3, R4, and R5 are each independently selected from C1 to C10 alkyl and C5-C20 aryl groups, and may be optionally monosubstituted, disubstituted, or trisubstituted by C1-C10 alkyl or C3-C10 alicyclic groups; R6 is a C6-C30 alkyl chain, which contains one to three double or triple bonds and at least one hydroxyl group; n is an integer between 0 and 10; and the boiling point of the hydroxyalkylsilane monomer is between 80 and 180°C. The low-boiling-point solvent is 2-ethylbutanol, 2-methyl-2-butanol, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, propylene glycol monomethyl ether, or a combination thereof. The amount of the organic solvent composition used is 50 to 120 parts by weight per 10 parts by weight of the polysiloxane composition. The high-boiling-point solvent in the organic solvent composition comprises 80 to 97% by weight, and the low-boiling-point solvent comprises 3 to 20% by weight; and The low-refractive-index optical resin has a refractive index between 1.1 and 1.35 after curing.

2. The low-refractive-index optical resin of claim 1, wherein the content of the high-boiling-point solvent in the organic solvent composition is 85 to 95% by weight, and the content of the low-boiling-point solvent is 5 to 15% by weight.

3. The low refractive index optical resin as claimed in claim 1, wherein the curing temperature of the low refractive index optical resin is between 50°C and 170°C.

4. The low refractive index optical resin as described in claim 1, wherein the yellowness index of the low refractive index optical resin after curing is not greater than 1.

5.

5. The low refractive index optical resin as claimed in claim 1, wherein the surface roughness Sa of the low refractive index optical resin after curing is between 5 μm and 50 μm.

6. The low refractive index optical resin of claim 1, wherein the viscosity of the low refractive index optical resin at 25°C is between 2 and 20 mPa·s, and the surface tension is between 20 and 40 dyne / cm.

7. The low-refractive-index optical resin of claim 1, wherein the surface tension of the high-boiling-point solvent is between 30 dyne / cm and 38 dyne / cm, and the surface tension of the low-boiling-point solvent is between 23 dyne / cm and 30 dyne / cm.

8. The low refractive index optical resin of claim 1, wherein the high boiling point solvent is γ-butyrolactone, diethylene glycol monoethyl ether, N-methylpyrrolidone, or a combination thereof.

9. The low refractive index optical resin of claim 1, wherein 10 to 70 parts by weight of hydroxyalkylsilane monomer are used for every 10 parts by weight of polysiloxane in the polysiloxane composition.

10. The low refractive index optical resin of claim 1, wherein the silane monomer is selected from the group consisting of tetramethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane, vinyltrimethoxysilane, propyleneoxypropyltrimethoxysilane, phenyltrimethoxysilane, methacryloxypropyltrimethoxysilane, and combinations thereof, and the weight-average molecular weight (Mw) is between 5,000 and 100,000 g / mol.

11. A low-refractive-index optical resin, comprising: A polysiloxane composition comprising a polysiloxane and a hydroxyalkylsilane monomer; and An organic solvent composition comprising a high-boiling-point solvent with a boiling point above 180°C, a medium-boiling-point organic solvent with a boiling point between 150°C and 180°C and a surface tension between 20 dyne / cm and 30 dyne / cm, and a low-boiling-point solvent with a boiling point below 150°C. in, The polysiloxane is prepared by hydrolysis and condensation or co-condensation of silane monomers; The structure of the hydroxyalkylsilane monomer is shown in formula (I): R1, R2, R3, R4, and R5 are each independently selected from C1 to C10 alkyl and C5-C20 aryl groups, and may be optionally monosubstituted, disubstituted, or trisubstituted by C1-C10 alkyl or C3-C10 alicyclic groups; R6 is a C6-C30 alkyl chain, which contains one to three double or triple bonds and at least one hydroxyl group; n is an integer between 0 and 10; and the boiling point of the hydroxyalkylsilane monomer is between 80 and 180°C. The low-boiling-point solvent is 2-ethylbutanol, 2-methyl-2-butanol, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, propylene glycol monomethyl ether, or a combination thereof. The amount of the organic solvent composition used is 50 to 120 parts by weight per 10 parts by weight of the polysiloxane composition. The total content of the high-boiling-point solvent and the medium-boiling-point organic solvent in the organic solvent composition is 80 to 97% by weight, and the content of the low-boiling-point solvent is 3 to 20% by weight; and The low-refractive-index optical resin has a refractive index between 1.1 and 1.35 after curing.

12. The low refractive index optical resin of claim 11, wherein the content of the intermediate boiling point organic solvent is 25 to 45% by weight of the total amount of the high boiling point solvent and the intermediate boiling point organic solvent.

13. The low refractive index optical resin of claim 11, wherein the medium-boiling-point organic solvent is 3-methoxybutanol, 4-methyl-1-pentanol, diacetone alcohol, propylene glycol n-propyl ether, ethylene glycol monotert-butyl ether, or ethylene glycol monobutyl ether.

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