High-refractive-index photocuring 3D printing enamel material and preparation method thereof

Abstract

The invention relates to the technical field of photocuring 3D printing materials, and discloses a high-refractive-index photocuring 3D printing enamel material and a preparation method thereof. According to the material, epoxy acrylate and polyurethane acrylate compound resin is used as a matrix, rutile type nano titanium dioxide and yttrium-stabilized tetragonal phase nano zirconium oxide composite powder is used as a high-refractive-index filler, and a silane coupling agent, a photoinitiator and a sintering aid precursor are used as auxiliary materials; the sintering aid precursor optimizes the subsequent sintering effect. The preparation method comprises the steps of filler surface modification, resin compounding, multi-stage gradient dispersion, photocuring 3D printing forming and subsequent programmed sintering treatment. The material can be used for preparing high-precision enamel products in the fields of jewelry, clocks and the like, can well give consideration to photocuring formability, high refractive index and adaptive sintering performance, and is beneficial to improving the comprehensive quality of the products; the preparation method is standard and controllable, and efficient forming of personalized enamel products of complex structures can be achieved.

Description

Technical Field

[0001] This application relates to the field of photopolymer 3D printing materials technology, specifically to a high refractive index photopolymer 3D printing enamel material and its preparation method, the obtained material can be used to prepare inorganic non-metallic enamel products. Background Technology

[0002] Enamel products, with their excellent chemical stability, decorative properties, and durability, have broad application prospects in jewelry, watches, art decoration, and architectural decoration. Their high refractive index further enhances their optical performance and added value. Photopolymerization 3D printing technology possesses advantages such as high forming precision, excellent detail reproduction, and the ability to fabricate complex three-dimensional structures. It can overcome the limitations of traditional enamel preparation processes, enabling the efficient molding of personalized, high-precision enamel products. Therefore, developing high-refractive-index enamel materials adapted to photopolymerization 3D printing has become a research direction with practical application value in the industry. Such materials typically need to simultaneously possess good photopolymerization molding characteristics, a high refractive index, and compatibility with subsequent sintering processes to ensure the final enamel product's molding quality and reliability.

[0003] Currently, existing photopolymer 3D printing enamel materials often suffer from unreasonable component selection and proportioning designs, making it difficult to achieve effective synergy among components. While some materials can meet the basic requirements of photopolymerization, the poor compatibility between inorganic fillers and the resin matrix not only makes it difficult to achieve the expected refractive index but may also introduce defects during subsequent sintering. Other materials, which focus on increasing the refractive index, may lead to decreased photopolymerization stability, making it difficult to meet the precision requirements of photopolymer 3D printing. They struggle to simultaneously achieve photopolymerization formability, high refractive index, and good sintering performance, thus affecting the overall quality of enamel products and failing to fully meet the high-performance requirements of practical applications. Summary of the Invention

[0004] To address the problem that existing photocurable 3D printing enamel materials suffer from unreasonable component selection and proportioning, making it difficult for each component to achieve effective synergy and simultaneously achieve photocurability, high refractive index, and good sintering performance, thus affecting the overall quality of enamel products, this application provides a high refractive index photocurable 3D printing enamel material and its preparation method.

[0005] In a first aspect, this application provides a high-refractive-index photopolymerizable 3D printing enamel material, employing the following technical solution: A high-refractive-index photocurable 3D printing enamel material, comprising the following components by mass: 30-55 parts photosensitive resin matrix; 40-65 parts high-refractive-index inorganic filler; 0.5-3 parts surface modifier; 0.1-2 parts sintering aid precursor; 1-6 parts photoinitiator; and 0.5-4 parts dispersing and stabilizing agent.

[0006] By adopting the above technical solution, the photosensitive resin matrix provides a cross-linked curing framework for the photopolymerization reaction, the high refractive index inorganic filler endows the material with core optical properties, the surface modifier builds a connection bridge between the inorganic and organic phases, the sintering aid precursor provides sintering active sites for subsequent heat treatment, the photoinitiator triggers the curing reaction of the system, the dispersing and stabilizing aid maintains the stability of the slurry system, and the components work together in proportion to form a complete material system that can meet the processing requirements of photopolymerization 3D printing and has the potential for subsequent sintering densification, providing core component support for the preparation of high-performance enamel products.

[0007] Preferably, the high-refractive-index inorganic filler is a composite powder of nano-titanium dioxide and nano-zirconia, wherein the nano-titanium dioxide is rutile type with an average primary particle size of 30-100 nm, and the nano-zirconia is yttrium-stabilized tetragonal phase with an average primary particle size of 50-150 nm; based on the total mass of the high-refractive-index inorganic filler, the mass proportion of nano-titanium dioxide is 60% to 90%, and the mass proportion of nano-zirconia is 10% to 40%.

[0008] By adopting the above technical solution, both rutile nano-titanium dioxide and yttrium-stabilized tetragonal nano-zirconia have high refractive index and stable crystal structure. The combination of the two can form a complementary high refractive index inorganic phase system. The specific primary particle size range can effectively avoid hard agglomeration and sedimentation of nanoparticles in the resin matrix. This mass ratio can enable the two inorganic powders to form a continuous and uniformly distributed inorganic phase structure inside the material, which not only ensures the overall high refractive index characteristics of the material, but also meets the requirements of fusion and densification of inorganic particles in the subsequent sintering process, thereby improving the structural uniformity and optical performance of the final enamel glaze layer.

[0009] Preferably, the surface modifier is γ-methacryloyloxypropyltrimethoxysilane.

[0010] By adopting the above technical solution, the surface modifier molecule has reactive groups at both ends. One end can undergo a covalent bonding reaction with the hydroxyl groups on the surface of the high refractive index inorganic filler, and be firmly adsorbed on the filler surface. The other end can participate in the photopolymerization and crosslinking reaction of the photosensitive resin matrix, and tightly connect the inorganic filler and the organic resin matrix through chemical bonds to construct a stable organic-inorganic interpenetrating network structure green skeleton. This greatly improves the dispersion stability and interfacial compatibility of the inorganic filler in the resin system, effectively improves the activation index and surface grafting rate of the modified filler, and fundamentally avoids problems such as agglomeration, stratification and sedimentation of the inorganic filler.

[0011] Preferably, the sintering aid precursor is one or more of tetrabutyl titanate, tetrabutyl zirconate, aluminum isopropoxide, or cerium acetylacetone; the photosensitive resin matrix is ​​a compound of epoxy acrylate and polyurethane acrylate, with a compounding ratio of 2:1 to 1:1.

[0012] By adopting the above technical solution, the selected organometallic sintering aid precursor can stably decompose to generate nanoscale metal oxide active centers during the thermal debinding stage. These active centers can form a composite low-melting-point eutectic system with the silicon-oxygen species remaining after the surface modifier decomposes, inducing liquid-phase sintering during the sintering stage and promoting the rapid densification and fusion of inorganic filler particles. Epoxy acrylate can ensure that the resin system has excellent photocuring reactivity, which is suitable for the rapid prototyping requirements of 3D printing. Polyurethane acrylate can significantly improve the mechanical strength and structural stability of the cured green body. The two are compounded in a specific ratio to simultaneously take into account the photocuring efficiency and the structural strength of the green body to withstand subsequent heat treatment.

[0013] Preferably, the photoinitiator is a compound system of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 1-hydroxycyclohexylphenyl ketone, with a mass ratio of 5:2 to 4:1; the dispersing and stabilizing agent comprises a block copolymer type polymeric superdispersant, a polyether-modified polydimethylsiloxane as a leveling agent, and a polysiloxane as an antifoaming agent.

[0014] By adopting the above technical solutions, the combination of two photoinitiators can be precisely adapted to the 405nm wavelength photopolymerization 3D printing light source, taking into account the curing uniformity of the material surface and deep layers, and avoiding problems such as incomplete curing and loose internal structure. The block copolymer type polymeric superdispersant in the dispersing and stabilizing agent is an acrylate-phosphate functionalized AB block copolymer. One end of the molecular chain contains a multidentate anchoring group composed of phosphate ester group and carboxyl group, which can form strong coordination adsorption with the hydroxyl group on the surface of inorganic filler. The other end is a long-chain polyacrylate solvation segment, which has excellent compatibility with the resin matrix. It effectively inhibits the agglomeration of inorganic filler through steric hindrance effect, ensuring the long-term dispersion and stability of the filler. The polyether modified polydimethylsiloxane can improve the flow and spreading properties of the slurry, adapting to the process characteristics of layer-by-layer molding in 3D printing. Polysiloxane can quickly eliminate the bubbles generated during the slurry preparation process, ensuring the light transmittance and molding accuracy of the slurry. The synergistic effect of multiple agents ensures that the slurry has rheological properties suitable for photopolymerization 3D printing.

[0015] Secondly, this application provides a method for preparing a high-refractive-index photopolymerizable 3D printing enamel material, employing the following technical solution: A method for preparing a high-refractive-index photopolymerizable 3D printing enamel material includes the following steps: S1. Pre-dispersion of sintering aid precursor: Dissolve the sintering aid precursor in a small amount of photosensitive resin matrix, stir and mix evenly under an inert atmosphere to form a pre-dispersion of sintering aid precursor. S2. Preparation of resin premix: The remaining photosensitive resin matrix is ​​mixed with the dispersion stabilizer and stirred evenly to obtain the resin premix. S3. Preparation of high solids content composite slurry: Modified composite filler and sintering aid precursor pre-dispersion liquid obtained in step S2 are added in batches under stirring conditions. After high shear fine dispersion treatment, photoinitiator is added. After stirring and mixing evenly in the dark, vacuum degassing is performed to finally obtain high refractive index photocurable 3D printing enamel material.

[0016] By adopting the above technical solution and employing a step-by-step, orderly dispersion preparation process, the sintering aid precursor is first pre-dispersed separately in a small amount of photosensitive resin. This avoids premature hydrolysis or oxidative deterioration caused by direct contact with other components. The resin premix allows the dispersion and stabilizing aids to be fully dissolved and distributed. The addition of modified composite filler in stages reduces the dispersion difficulty of high solids content systems. High-shear fine dispersion can completely break up the agglomerates of inorganic fillers. Light-protected operation can protect the activity of photoinitiators from being lost. Vacuum degassing can completely remove residual bubbles in the system. Finally, a high solids content composite slurry with uniform dispersion, excellent stability, and rheological properties suitable for photopolymerization 3D printing is obtained.

[0017] Preferably, in step S1, when preparing the sintering aid precursor pre-dispersion liquid, the inert atmosphere is nitrogen or argon, the stirring speed is 200-500 rpm, the stirring time is 30-60 min, and the temperature is room temperature to 40°C.

[0018] By adopting the above technical solution, the nitrogen or argon inert atmosphere can effectively isolate air and moisture, preventing premature hydrolysis, oxidation or deterioration of the metal-organic sintering aid precursor during the dispersion process. The specific stirring speed, stirring time and temperature range can fully dissolve and uniformly disperse the sintering aid precursor in the photosensitive resin matrix, forming a stable and uniform pre-dispersion system, avoiding the problem of local aggregation and uneven distribution of the precursor, and ensuring the uniform distribution of active centers in the subsequent sintering process.

[0019] Preferably, in step S3, the high-shear fine dispersion treatment adopts a multi-stage gradient grinding process, and is cyclically treated 3-5 times at dispersion gaps of 45-55μm, 20-30μm, and 10-20μm respectively; the modified composite filler is gradually added to the resin premix in 3-5 batches.

[0020] By adopting the above technical solutions, the multi-stage gradient grinding process gradually reduces the dispersion gap, refines the agglomerated particles of inorganic fillers, and gradually improves the dispersion fineness and uniformity of fillers in the resin system, avoiding the damage to the filler structure caused by one-time high-intensity grinding. The modified composite filler is added in stages, which avoids the problem of excessively high local concentration and incomplete dispersion caused by one-time addition, so that the modified filler and the resin matrix are fully impregnated and mixed, further improving the uniformity and long-term stability of the slurry system.

[0021] Thirdly, this application provides a method for preparing high refractive index enamel articles, employing the following technical solution: A method for preparing a high-refractive-index enamel product includes the following steps: A1. Photopolymer additive manufacturing: High refractive index photopolymer 3D printing enamel material is photopolymerized layer by layer to prepare a green blank with a preset three-dimensional structure; A2. Cleaning and drying of the green green body: The green green body is subjected to multi-stage ultrasonic cleaning to remove uncured slurry residue on the surface and in the internal pores. After cleaning, it is dried at low temperature. A3. Programmed gradient heat treatment: The dried green body is placed in a programmed temperature-controlled furnace. First, it is pre-carbonized at low temperature under an inert atmosphere, and then it is switched to an oxidizing atmosphere for hot degreasing treatment to completely remove the organic components in the green body and obtain an inorganic porous green body. Finally, it is heated for glazing and sintering treatment to densify the inorganic filler particles and form a continuous vitrified enamel glaze layer. After natural cooling in the furnace, a high refractive index enamel product is obtained.

[0022] By adopting the above technical solutions, photopolymer additive manufacturing can achieve high-precision layer-by-layer molding of complex three-dimensional structures, accurately prepare green blanks of preset shapes, and thoroughly remove uncured slurry from the surface and internal pores of the blank, avoiding the impact of residual slurry on the quality of subsequent heat treatment. Low-temperature drying can remove moisture without damaging the blank structure, maintaining the structural integrity of the green blank. Programmed gradient heat treatment completes the pretreatment of the blank, removal of organic components and densification of inorganic phases in stages. The orderly heat treatment process can avoid defects such as cracking, deformation and pores in the blank, and finally form a continuous and dense vitrified enamel glaze layer.

[0023] Preferably, in step A3, the low-temperature pre-carbonization treatment is as follows: under a nitrogen or argon inert atmosphere, the temperature is increased from room temperature to 250-350℃ at a heating rate of 1-2℃ / min, and held for 30-60min; the thermal degreasing treatment is as follows: switching to an air oxidizing atmosphere, first heating from 250-350℃ to 300℃ at a heating rate of 0.8-1.2℃ / min, then heating from 300℃ to 480-520℃ at a heating rate of 0.4-0.6℃ / min, and held for 80-100min; the glazing sintering treatment is as follows: heating to 710-800℃ at a heating rate of 2.5-5.5℃ / min, and held for 10-30min.

[0024] By adopting the above technical solutions, low-temperature pre-carbonization under an inert atmosphere can gently pre-treat the green body, avoiding rapid decomposition of organic components that could lead to cracking and damage. The segmented gradient heating hot degreasing process can slowly and thoroughly remove all organic components from the green body, forming a structurally complete inorganic porous green body and reducing the risk of defects. The specific glazing sintering temperature and holding time can fully activate the role of the sintering aid precursor, promote the efficient densification and fusion of inorganic filler particles, and form a smooth, continuous, and defect-free high-refractive-index glassy enamel glaze layer, thereby improving the overall performance of the product.

[0025] In summary, this application has the following beneficial effects: 1. Because this application adopts a multi-component synergistic system with a specific ratio, using epoxy acrylate and polyurethane acrylate composite as the photosensitive resin matrix, rutile nano-titanium dioxide and yttrium-stabilized tetragonal nano-zirconia composite powder as high refractive index inorganic filler, and combined with γ-methacryloyloxypropyltrimethoxysilane surface modifier and specific sintering aid precursor, the components complement each other and work synergistically. The surface modifier achieves good compatibility between the inorganic filler and the resin matrix, and the sintering aid precursor provides support for subsequent densification sintering. This results in a material that has excellent photocurable molding properties, high refractive index and good sintering performance, and can be stably adapted to photocurable 3D printing process to prepare high-performance enamel products.

[0026] 2. In this application, a specific preparation process is preferably adopted, in which the sintering aid precursor is pre-dispersed in the photosensitive resin matrix under an inert atmosphere, and then finely dispersed under high shear through a multi-stage gradient grinding process. Modified composite fillers are added in stages to effectively avoid filler agglomeration, ensure that the sintering aid is uniformly dispersed in the system, give full play to the role of each component, and obtain the effect of high solid content composite slurry with excellent dispersion stability, viscosity suitable for 3D printing, and uniform and defect-free green body structure after molding.

[0027] 3. The enamel product preparation method of this application achieves precise molding of a preset three-dimensional structure through photopolymerization additive manufacturing, removes residual uncured slurry through multi-stage ultrasonic cleaning and low-temperature drying, and then completes low-temperature pre-carbonization in an inert atmosphere, thermal degreasing in an oxidizing atmosphere and glazing sintering through programmed gradient heat treatment in sequence, orderly removing organic components and promoting the densification of inorganic fillers. Therefore, the product has high three-dimensional structural precision, continuous and dense glaze layer, strong bonding with the substrate, and stable comprehensive performance.

[0028] 4. In this application, rutile nano-titanium dioxide and yttrium-stabilized tetragonal nano-zirconia are preferably used in a specific ratio to form a high refractive index inorganic filler. The two powders have stable crystal forms and complementary refractive index characteristics. By controlling a specific particle size range, a continuous high refractive index phase can be formed in the material system, which effectively improves the optical refractive index of the material and the product. This results in enamel products with excellent optical performance, which can meet the application requirements of high refractive index. Attached Figure Description

[0029] Figure 1 This is a flowchart of a method for preparing a high-refractive-index photocurable 3D printing enamel material provided in this application; Figure 2 This is a flowchart of a method for preparing a high refractive index enamel product provided in this application. Detailed Implementation

[0030] The present application will be further described in detail below with reference to embodiments and comparative examples. Unless otherwise specified, the experimental methods used below are conventional methods. Unless otherwise specified, the materials, reagents, methods and instruments used are all conventional materials, reagents, methods and instruments in the art, which can be obtained by those skilled in the art through commercial channels or prepared according to literature methods.

[0031] Technical concept: Current photopolymer 3D printing enamel materials generally suffer from poor performance adaptability. The core reason is the lack of systematic design in component selection and ratio, poor interfacial compatibility between inorganic fillers and resin matrix, and difficulty in adapting the selection of sintering aids to the photopolymerization system and subsequent heat treatment process. In addition, traditional heat treatment processes are prone to causing defects in the green body structure. Ultimately, the material cannot simultaneously achieve photopolymerization formability, high refractive index characteristics and good sintering densification effect, making it difficult to meet the requirements for the preparation of high-precision enamel products.

[0032] This application addresses the aforementioned issues by constructing a multi-component synergistic material system. It selects a compounded photosensitive resin as the matrix, combines it with a high-refractive-index composite inorganic filler with a specific crystal form and particle size, employs a silane coupling agent to improve the interfacial bonding between the filler and the resin, and selects an organometallic compound as a sintering aid precursor. Simultaneously, it incorporates an inert atmosphere pre-dispersion and multi-level gradient fine dispersion preparation process, as well as a three-stage programmed gradient heat treatment process. This comprehensive optimization from material composition and preparation process to post-processing achieves a synergistic improvement in the material's photocurability, refractive index, and sintering performance.

[0033] The following are the main raw materials and reagents used in this application, and their sources and specifications are as follows; unless otherwise specified, all reagents are commercially available analytical grade or higher products: 1. Epoxy acrylate was purchased from Jiangsu Boquan Biotechnology Co., Ltd., CAS: 71281-65-7; 2. The polyurethane acrylate was purchased from Shandong Yinglang Chemical Co., Ltd., with a purity of 99%. γ-methacryloyloxypropyltrimethoxysilane was purchased from Chongqing Ruiya Biotechnology Co., Ltd., product number: 2530-85-0; 3. Tetrabutyl titanate was purchased from Shanghai Yuanye Biotechnology Co., Ltd., product number: S48406; 4. 2,4,6-Trimethylbenzoyl-diphenylphosphine oxide was purchased from Jiangsu Congzhong Chemical Co., Ltd., item number: 20080; 5. 1-Hydroxycyclohexylphenyl ketone was purchased from Henan Alpha Chemical Co., Ltd., item number: A947193; 6. Polyether-modified polydimethylsiloxane was purchased from Shanghai Jiadeer Chemical Technology Co., Ltd., item number: ZY-129 7. The polysiloxane was purchased from Hunan Deqian New Materials Co., Ltd., CAS: 9011-19-2.

[0034] Example 1: This example provides a high refractive index photocurable 3D printing enamel material, comprising the following raw materials in parts by weight: 42.5 parts of photosensitive resin matrix, 52.5 parts of high refractive index inorganic filler, 1.75 parts of surface modifier, 1.05 parts of sintering aid precursor, 3.5 parts of photoinitiator, and 2.25 parts of dispersion and stabilizing agent.

[0035] The high-refractive-index inorganic filler is a composite powder of nano-titanium dioxide and nano-zirconia. The nano-titanium dioxide is rutile type with an average primary particle size of 65 nm, and the nano-zirconia is yttrium-stabilized tetragonal phase with an average primary particle size of 100 nm. Based on the total mass of the high-refractive-index inorganic filler, the mass proportion of nano-titanium dioxide is 75%, and the mass proportion of nano-zirconia is 25%. Among them, the surface modifier is γ-methacryloxypropyltrimethoxysilane, one end of which is bonded to the hydroxyl groups on the surface of the high refractive index inorganic filler through chemical bonds, and the other end provides a methacryloxy functional group that can participate in the photopolymerization reaction. This functional group can undergo a copolymerization reaction with the photosensitive resin matrix during the photocuring stage to form chemical crosslinking points and construct a green body skeleton with an organic-inorganic interpenetrating network structure. Among them, the sintering aid precursor is tetrabutyl titanate, which can decompose to generate nano-sized titanium dioxide active centers during the hot degreasing stage. It forms a composite low-melting-point eutectic system with the silicon and oxygen species remaining after the surface modifier decomposes, which induces liquid phase sintering during the sintering stage, reduces the sintering temperature and promotes the densification of inorganic filler particles. The photosensitive resin matrix is ​​a compound of epoxy acrylate and polyurethane acrylate, with a compounding ratio of 1.5:1. The photoinitiator is a compound system of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 1-hydroxycyclohexylphenyl ketone, with a mass ratio of 3:1. The dispersing and stabilizing agents include block copolymer-type polymeric superdispersant, polyether-modified polydimethylsiloxane as a leveling agent, and polysiloxane as an antifoaming agent, with a mass ratio of 80%, 13.3%, and 6.7%, respectively. The block copolymer-type superdispersant stabilizes the filler particles through steric hindrance, the polyether-modified polydimethylsiloxane improves the leveling properties of the slurry, and the polysiloxane eliminates bubbles generated during slurry mixing.

[0036] In this embodiment, a modified composite filler was prepared by surface modification of the aforementioned high-refractive-index inorganic filler. This modified composite filler maintains its original crystal form and primary particle size, without the formation of hard agglomerates, and its surface is grafted with methacryloyloxy functional groups that can participate in photopolymerization. The specific preparation method is as follows: Rutile nano-titanium dioxide and yttrium-stabilized tetragonal nano-zirconia were mixed in a high-speed mixer at 800 rpm for 15 minutes to obtain a uniform nanocomposite filler powder. The mixed powder was then dried in a vacuum drying oven at 120℃ and -0.095 MPa for 4 hours to thoroughly remove physically adsorbed free water and volatile impurities from the powder surface. Simultaneously, 1.75 parts of γ-methacryloyloxypropyltrimethoxysilane were added to a mixed solvent of 100 parts (95:5 volume ratio) of anhydrous ethanol and deionized water, and the pH of the system was slowly adjusted to 4.5 with glacial acetic acid. The silane coupling agent was continuously hydrolyzed at 300 rpm for 30 minutes at room temperature to ensure complete hydrolysis and formation of a homogeneous and stable silanol solution. The dried nanocomposite filler powder was then added to 400 parts of anhydrous ethanol and ultrasonically pre-dispersed at 300W for 20 minutes to obtain a stable filler suspension with no significant sedimentation. The filler suspension was transferred to a three-necked flask equipped with a reflux condenser, nitrogen protection, and mechanical stirring. Under continuous nitrogen purging and 400 rpm mechanical stirring, the silanol solution was added dropwise to the filler suspension at a uniform rate over 1 hour. After the addition was completed, the temperature was raised to [temperature missing]. The reaction was carried out at 70℃ under reflux condensation and nitrogen protection for 3 hours with continuous stirring to ensure that the silanol groups and the hydroxyl groups on the filler surface fully undergo covalent bonding. After the reaction, the mixture was transferred to a centrifuge and centrifuged at 3000 rpm for 15 minutes to collect the solid product. The solid product was washed three times with anhydrous ethanol, and centrifuged after each wash until the conductivity of the washing supernatant was consistent with that of pure anhydrous ethanol, thus thoroughly removing unreacted silane coupling agent and impurities physically adsorbed on the powder surface. The washed and purified solid product was then placed in a 250W microwave drying device. The powder was dried for 12 minutes to initially remove the solvent and prevent secondary agglomeration during the drying process. Then, the powder was transferred to a vacuum drying oven at 80℃ and a vacuum degree of -0.095MPa for 12 hours. After drying, it was thoroughly ground with an agate mortar and passed through a 200-mesh standard sieve. Finally, a modified composite filler with methacryloyloxy functional groups grafted onto its surface to participate in the photopolymerization reaction was obtained. The modified composite filler was tested and found to have an activation index ≥96% and a surface grafting rate of 3.2%. It has excellent compatibility with acrylate photosensitive resin matrix and can be stably dispersed in the resin system without sedimentation.

[0037] The preparation method of the above-mentioned high refractive index photopolymerizable 3D printing enamel material includes the following steps: S1. Pre-dispersion of sintering aid precursor: Dissolve the sintering aid precursor in a small amount of photosensitive resin matrix, stir and mix evenly under an inert atmosphere to form a pre-dispersion of sintering aid precursor. The inert atmosphere was nitrogen, the stirring speed was 350 rpm, the stirring time was 45 min, and the temperature was 25℃. S2. Preparation of resin premix: The remaining photosensitive resin matrix is ​​mixed with the dispersing and stabilizing agent and stirred evenly to obtain the resin premix; S3. Preparation of high solids content composite slurry: Modified composite filler and sintering aid precursor pre-dispersion liquid obtained in step S1 are added in batches under stirring conditions. After high shear fine dispersion treatment, photoinitiator is added. After stirring and mixing evenly in the dark, vacuum degassing is performed to finally obtain high refractive index photocurable 3D printing enamel material. The high-shear fine dispersion treatment employed a multi-stage gradient grinding process, with each stage being cyclically treated four times at dispersion gaps of 50μm, 25μm, and 15μm. The modified composite filler was added to the resin premix in four separate additions. Vacuum degassing was performed at a pressure below -0.095MPa with low-speed stirring for 45 minutes. The final material had a viscosity of 3500 mPa·s at 25℃ and a transmittance of 76% at a wavelength of 405nm. This embodiment also provides a method for preparing high refractive index enamel products, using the above-mentioned high refractive index photocurable 3D printing enamel material, including the following steps: A1. Photopolymer additive manufacturing: High refractive index photopolymer 3D printing enamel material is photopolymerized layer by layer to prepare a green blank with a preset three-dimensional structure; The process employed digital light processing technology with a light source wavelength of 405nm, with slicing parameters set to a layer thickness of 37.5μm, a bottom layer exposure time that was 2.5 times that of the top layer exposure time, and a top layer exposure time of 5 seconds per layer. A2. Cleaning and drying of the green green body: The green green body is subjected to multi-stage ultrasonic cleaning to remove uncured slurry residue on the surface and in the internal pores. After cleaning, it is dried at low temperature. The multi-stage ultrasonic cleaning process involves first ultrasonically cleaning with an aliphatic hydrocarbon solvent for 3.5 minutes, followed by ultrasonic cleaning with isopropanol for 3.5 minutes; the low-temperature drying process involves drying in a 50°C forced-air drying oven for 22.5 minutes. A3. Programmed gradient heat treatment: The dried green body is placed in a programmed temperature-controlled furnace. First, it is pre-carbonized at low temperature under an inert atmosphere, and then it is switched to an oxidizing atmosphere for hot degreasing treatment to completely remove the organic components in the green body and obtain an inorganic porous green body. Finally, it is heated for glazing and sintering treatment to densify the inorganic filler particles and form a continuous vitrified enamel glaze layer. After natural cooling in the furnace, a high refractive index enamel product is obtained. The low-temperature pre-carbonization treatment is as follows: under a nitrogen inert atmosphere, the temperature is increased from room temperature to 300℃ at a heating rate of 1.5℃ / min and held for 45 min; the hot degreasing treatment is as follows: switching to an air oxidizing atmosphere, the temperature is first increased from 300℃ to 300℃ at a heating rate of 1.0℃ / min and held at that temperature, and then increased from 300℃ to 500℃ at a heating rate of 0.5℃ / min and held for 90 min; the glazing sintering treatment is as follows: the temperature is increased to 755℃ at a heating rate of 4℃ / min and held for 20 min.

[0038] Example 2: This example provides a high refractive index photocurable 3D printing enamel material, comprising the following raw materials in parts by weight: 30 parts photosensitive resin matrix, 40 parts high refractive index inorganic filler, 0.5 parts surface modifier, 0.1 parts sintering aid precursor, 1 part photoinitiator, and 0.5 parts dispersing and stabilizing agent.

[0039] The high-refractive-index inorganic filler is a composite powder of nano-titanium dioxide and nano-zirconia. The nano-titanium dioxide is rutile type with an average primary particle size of 30 nm, and the nano-zirconia is yttrium-stabilized tetragonal phase with an average primary particle size of 50 nm. Based on the total mass of the high-refractive-index inorganic filler, the mass proportion of nano-titanium dioxide is 60%, and the mass proportion of nano-zirconia is 40%. Among them, the surface modifier is γ-methacryloxypropyltrimethoxysilane, one end of which is bonded to the hydroxyl groups on the surface of the high refractive index inorganic filler through chemical bonds, and the other end provides a methacryloxy functional group that can participate in the photopolymerization reaction. This functional group can undergo a copolymerization reaction with the photosensitive resin matrix during the photocuring stage to form chemical crosslinking points and construct a green body skeleton with an organic-inorganic interpenetrating network structure. Among them, the sintering aid precursor is tetrabutyl zirconate, which can decompose to generate nano-sized zirconium dioxide active centers during the hot degreasing stage. It forms a composite low-melting-point eutectic system with the silicon and oxygen species remaining after the surface modifier decomposes, which induces liquid phase sintering during the sintering stage, reduces the sintering temperature and promotes the densification of inorganic filler particles. The photosensitive resin matrix is ​​a mixture of epoxy acrylate and polyurethane acrylate, with a mixing ratio of 1:1. The photoinitiator is a compound system of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 1-hydroxycyclohexylphenyl ketone, with a mass ratio of 5:2. The dispersing and stabilizing agents include block copolymer-type polymeric superdispersant, polyether-modified polydimethylsiloxane as a leveling agent, and polysiloxane as an antifoaming agent, with a mass ratio of 80%, 14%, and 6%, respectively. The block copolymer-type superdispersant stabilizes the filler particles through steric hindrance, the polyether-modified polydimethylsiloxane improves the leveling properties of the slurry, and the polysiloxane eliminates bubbles generated during slurry mixing.

[0040] In this embodiment, a modified composite filler was prepared by surface modification of the aforementioned high-refractive-index inorganic filler. This modified composite filler maintains its original crystal form and primary particle size, without the formation of hard agglomerates, and its surface is grafted with methacryloyloxy functional groups that can participate in photopolymerization. The specific preparation method is as follows: Rutile nano-titanium dioxide and yttrium-stabilized tetragonal nano-zirconia were mixed in a high-speed mixer at 600 rpm for 10 minutes to obtain a uniform nanocomposite filler powder. The mixed powder was then dried in a vacuum drying oven at 120℃ and -0.095 MPa for 4 hours to thoroughly remove physically adsorbed free water and volatile impurities from the powder surface. Simultaneously, 0.5 parts of γ-methacryloyloxypropyltrimethoxysilane were added to a mixed solvent of 100 parts (95:5 volume ratio) of anhydrous ethanol and deionized water, and the pH of the system was slowly adjusted to 4.0 with glacial acetic acid. Hydrolyze the silane coupling agent at room temperature with continuous stirring at 200 rpm for 20 minutes to ensure complete hydrolysis and formation of a homogeneous and stable silanol solution. Then, add the dried nanocomposite filler powder to 400 parts of anhydrous ethanol and ultrasonically pre-disperse it at 200W for 15 minutes to obtain a stable filler suspension with no significant sedimentation. Transfer the filler suspension to a three-necked flask equipped with a reflux condenser, nitrogen protection, and mechanical stirring. Under continuous nitrogen purging and mechanical stirring at 300 rpm, the silanol solution is added dropwise to the filler suspension at a uniform rate over 45 minutes. After the addition is complete, the temperature is raised to 60°C. The reaction was carried out at 5℃ under reflux condensation and nitrogen protection for 2.5 hours with continuous stirring to ensure that the silanol groups and the hydroxyl groups on the filler surface fully undergo covalent bonding. After the reaction, the mixture was transferred to a centrifuge and centrifuged at 3000 rpm for 15 minutes to collect the solid product. The solid product was washed twice with anhydrous ethanol, and centrifuged after each wash until the conductivity of the washing supernatant was consistent with that of pure anhydrous ethanol, thus thoroughly removing unreacted silane coupling agent and impurities physically adsorbed on the powder surface. The washed and purified solid product was then placed in a 200W microwave drying device. The powder is dried for 10 minutes to initially remove the solvent and prevent secondary agglomeration during the drying process. Then, the powder is transferred to a vacuum drying oven at 70℃ and a vacuum degree of -0.095MPa for 10 hours. After drying, it is thoroughly ground with an agate mortar and passed through a 200-mesh standard sieve. Finally, a modified composite filler with methacryloyloxy functional groups grafted on its surface to participate in the photopolymerization reaction is obtained. The modified composite filler has an activation index of ≥92% and a surface grafting rate of 1.1%. It has excellent compatibility with acrylate photosensitive resin matrix and can be stably dispersed in the resin system without sedimentation.

[0041] The preparation method of the above-mentioned high refractive index photopolymerizable 3D printing enamel material includes the following steps: S1. Pre-dispersion of sintering aid precursor: Dissolve the sintering aid precursor in a small amount of photosensitive resin matrix, stir and mix evenly under an inert atmosphere to form a pre-dispersion of sintering aid precursor. The inert atmosphere was argon, the stirring speed was 200 rpm, the stirring time was 30 min, and the temperature was room temperature. S2. Preparation of resin premix: The remaining photosensitive resin matrix is ​​mixed with the dispersing and stabilizing agent and stirred evenly to obtain the resin premix; S3. Preparation of high solids content composite slurry: Modified composite filler and sintering aid precursor pre-dispersion liquid obtained in step S1 are added in batches under stirring conditions. After high shear fine dispersion treatment, photoinitiator is added. After stirring and mixing evenly in the dark, vacuum degassing is performed to finally obtain high refractive index photocurable 3D printing enamel material. The high-shear fine dispersion treatment employed a multi-stage gradient grinding process, with each stage being cyclically treated three times at dispersion gaps of 45μm, 20μm, and 10μm. The modified composite filler was gradually added to the resin premix in three separate additions. Vacuum degassing was performed at a pressure below -0.095MPa with low-speed stirring for 30 minutes. The final material had a viscosity of 2200 mPa·s at 25℃ and a transmittance of 72% at a wavelength of 405nm. This embodiment also provides a method for preparing high refractive index enamel products, using the above-mentioned high refractive index photocurable 3D printing enamel material, including the following steps: A1. Photopolymer additive manufacturing: High refractive index photopolymer 3D printing enamel material is photopolymerized layer by layer to prepare a green blank with a preset three-dimensional structure; Among them, stereolithography with a light source wavelength of 405nm was used, the slicing parameters were set to a layer thickness of 25μm, the bottom layer exposure time was twice the surface layer exposure time, and the surface layer exposure time was 2 seconds / layer; A2. Cleaning and drying of the green green body: The green green body is subjected to multi-stage ultrasonic cleaning to remove uncured slurry residue on the surface and in the internal pores. After cleaning, it is dried at low temperature. The multi-stage ultrasonic cleaning process involves first ultrasonically cleaning with an aliphatic hydrocarbon solvent for 2 minutes, followed by ultrasonic cleaning with isopropanol for 2 minutes; the low-temperature drying process involves drying in a 40°C forced-air drying oven for 15 minutes. A3. Programmed gradient heat treatment: The dried green body is placed in a programmed temperature-controlled furnace. First, it is pre-carbonized at low temperature under an inert atmosphere, and then it is switched to an oxidizing atmosphere for hot degreasing treatment to completely remove the organic components in the green body and obtain an inorganic porous green body. Finally, it is heated for glazing and sintering treatment to densify the inorganic filler particles and form a continuous vitrified enamel glaze layer. After natural cooling in the furnace, a high refractive index enamel product is obtained. The low-temperature pre-carbonization treatment is as follows: under an inert argon atmosphere, the temperature is increased from room temperature to 250℃ at a heating rate of 1℃ / min and held for 30 min; the hot degreasing treatment is as follows: switching to an air oxidizing atmosphere, the temperature is first increased from 250℃ to 300℃ at a heating rate of 0.8℃ / min and held at that temperature for transition, and then increased from 300℃ to 480℃ at a heating rate of 0.4℃ / min and held for 80 min; the glazing sintering treatment is as follows: the temperature is increased to 710℃ at a heating rate of 2.5℃ / min and held for 10 min.

[0042] Example 3: This example provides a high refractive index photocurable 3D printing enamel material, comprising the following raw materials in parts by weight: 55 parts of photosensitive resin matrix, 65 parts of high refractive index inorganic filler, 3 parts of surface modifier, 2 parts of sintering aid precursor, 6 parts of photoinitiator, and 4 parts of dispersing and stabilizing agent.

[0043] The high-refractive-index inorganic filler is a composite powder of nano-titanium dioxide and nano-zirconia. The nano-titanium dioxide is rutile type with an average primary particle size of 100 nm, and the nano-zirconia is yttrium-stabilized tetragonal phase with an average primary particle size of 150 nm. Based on the total mass of the high-refractive-index inorganic filler, the mass proportion of nano-titanium dioxide is 90%, and the mass proportion of nano-zirconia is 10%. Among them, the surface modifier is γ-methacryloxypropyltrimethoxysilane, one end of which is bonded to the hydroxyl groups on the surface of the high refractive index inorganic filler through chemical bonds, and the other end provides a methacryloxy functional group that can participate in the photopolymerization reaction. This functional group can undergo a copolymerization reaction with the photosensitive resin matrix during the photocuring stage to form chemical crosslinking points and construct a green body skeleton with an organic-inorganic interpenetrating network structure. Among them, the sintering aid precursor is aluminum isopropoxide, which can decompose to generate nano-sized alumina active centers during the hot degreasing stage. It forms a composite low-melting-point eutectic system with the silicon and oxygen species remaining after the surface modifier decomposes, which induces liquid phase sintering during the sintering stage, reduces the sintering temperature and promotes the densification of inorganic filler particles. The photosensitive resin matrix is ​​a mixture of epoxy acrylate and polyurethane acrylate, with a mixing ratio of 2:1. The photoinitiator is a compound system of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 1-hydroxycyclohexylphenyl ketone, with a mass ratio of 4:1. The dispersing and stabilizing agents include block copolymer-type polymeric superdispersant, polyether-modified polydimethylsiloxane as a leveling agent, and polysiloxane as an antifoaming agent, with a mass ratio of 80%, 12.5%, and 7.5%, respectively. The block copolymer-type superdispersant stabilizes the filler particles through steric hindrance, the polyether-modified polydimethylsiloxane improves the leveling properties of the slurry, and the polysiloxane eliminates bubbles generated during slurry mixing.

[0044] In this embodiment, a modified composite filler was prepared by surface modification of the aforementioned high-refractive-index inorganic filler. This modified composite filler maintains its original crystal form and primary particle size, without the formation of hard agglomerates, and its surface is grafted with methacryloyloxy functional groups that can participate in photopolymerization. The specific preparation method is as follows: Rutile nano-titanium dioxide and yttrium-stabilized tetragonal nano-zirconia were mixed in a high-speed mixer at 1000 rpm for 20 minutes to obtain a uniform nanocomposite filler powder. The mixed powder was then dried in a vacuum drying oven at 120℃ and -0.095 MPa for 4 hours to thoroughly remove physically adsorbed free water and volatile impurities from the powder surface. Simultaneously, 3 parts of γ-methacryloyloxypropyltrimethoxysilane were added to a 95:5 volume ratio mixture of anhydrous ethanol and deionized water, and the pH of the system was slowly adjusted to 5.0 with glacial acetic acid. The silane coupling agent was continuously hydrolyzed at 400 rpm for 40 minutes under constant temperature to ensure complete hydrolysis and formation of a homogeneous and stable silanol solution. The dried nanocomposite filler powder was then added to 400 parts of anhydrous ethanol and ultrasonically pre-dispersed at 400W for 25 minutes to obtain a stable filler suspension with no significant sedimentation. The filler suspension was transferred to a three-necked flask equipped with a reflux condenser, nitrogen protection, and mechanical stirring. Under continuous nitrogen purging and mechanical stirring at 500 rpm, the silanol solution was added dropwise to the filler suspension at a uniform rate over 1.5 hours. After the addition was completed, the temperature was raised to 7°C. The reaction was carried out at 5℃ under reflux condensation and nitrogen protection for 3.5 hours with continuous stirring to ensure that the silanol groups and the hydroxyl groups on the filler surface fully undergo covalent bonding. After the reaction, the mixture was transferred to a centrifuge and centrifuged at 3000 rpm for 15 minutes to collect the solid product. The solid product was washed four times with anhydrous ethanol, and centrifuged after each wash until the conductivity of the supernatant was consistent with that of pure anhydrous ethanol, thus thoroughly removing unreacted silane coupling agent and impurities physically adsorbed on the powder surface. The washed and purified solid product was then placed in a 300W microwave drying device. The powder was dried for 15 minutes to initially remove the solvent and prevent secondary agglomeration during the drying process. Then, the powder was transferred to a vacuum drying oven at 90℃ and a vacuum degree of -0.095MPa for 14 hours. After drying, it was thoroughly ground with an agate mortar and passed through a 200-mesh standard sieve. Finally, a modified composite filler with methacryloyloxy functional groups grafted onto its surface to participate in the photopolymerization reaction was obtained. The modified composite filler was tested and found to have an activation index ≥98% and a surface grafting rate of 4.1%. It has excellent compatibility with acrylate photosensitive resin matrix and can be stably dispersed in the resin system without sedimentation.

[0045] The preparation method of the above-mentioned high refractive index photopolymerizable 3D printing enamel material includes the following steps: S1. Pre-dispersion of sintering aid precursor: Dissolve the sintering aid precursor in a small amount of photosensitive resin matrix, stir and mix evenly under an inert atmosphere to form a pre-dispersion of sintering aid precursor. The inert atmosphere was nitrogen, the stirring speed was 500 rpm, the stirring time was 60 min, and the temperature was 40℃. S2. Preparation of resin premix: The remaining photosensitive resin matrix is ​​mixed with the dispersing and stabilizing agent and stirred evenly to obtain the resin premix; S3. Preparation of high solids content composite slurry: Modified composite filler and sintering aid precursor pre-dispersion liquid obtained in step S1 are added in batches under stirring conditions. After high shear fine dispersion treatment, photoinitiator is added. After stirring and mixing evenly in the dark, vacuum degassing is performed to finally obtain high refractive index photocurable 3D printing enamel material. The high-shear fine dispersion treatment employed a multi-stage gradient grinding process, with each stage involving five cycles at dispersion gaps of 55μm, 30μm, and 20μm. The modified composite filler was added to the resin premix in five separate additions. Vacuum degassing was performed at a pressure below -0.095MPa with low-speed stirring for 60 minutes. The final material had a viscosity of [missing value] at 25℃. The transmittance at a wavelength of 405nm is 70%; This embodiment also provides a method for preparing high refractive index enamel products, using the above-mentioned high refractive index photocurable 3D printing enamel material, including the following steps: A1. Photopolymer additive manufacturing: High refractive index photopolymer 3D printing enamel material is photopolymerized layer by layer to prepare a green blank with a preset three-dimensional structure; Among them, digital light processing technology with a light source wavelength of 405nm was used, the slicing parameters were set to a layer thickness of 50μm, the bottom layer exposure time was 3 times the top layer exposure time, and the top layer exposure time was 8 seconds / layer; A2. Cleaning and drying of the green green body: The green green body is subjected to multi-stage ultrasonic cleaning to remove uncured slurry residue on the surface and in the internal pores. After cleaning, it is dried at low temperature. The multi-stage ultrasonic cleaning process involves first ultrasonically cleaning with an aliphatic hydrocarbon solvent for 5 minutes, followed by ultrasonic cleaning with isopropanol for 5 minutes; the low-temperature drying process involves drying in a 60°C forced-air drying oven for 30 minutes. A3. Programmed gradient heat treatment: The dried green body is placed in a programmed temperature-controlled furnace. First, it is pre-carbonized at low temperature under an inert atmosphere, and then it is switched to an oxidizing atmosphere for hot degreasing treatment to completely remove the organic components in the green body and obtain an inorganic porous green body. Finally, it is heated for glazing and sintering treatment to densify the inorganic filler particles and form a continuous vitrified enamel glaze layer. After natural cooling in the furnace, a high refractive index enamel product is obtained. The low-temperature pre-carbonization treatment is as follows: under a nitrogen inert atmosphere, the temperature is increased from room temperature to 350℃ at a heating rate of 2℃ / min and held for 60min; the hot degreasing treatment is as follows: switching to an air oxidizing atmosphere, the temperature is first increased from 350℃ to 300℃ at a heating rate of 1.2℃ / min and held at that temperature, and then increased from 300℃ to 520℃ at a heating rate of 0.6℃ / min and held for 100min; the glazing sintering treatment is as follows: the temperature is increased to 800℃ at a heating rate of 5.5℃ / min and held for 30min.

[0046] Comparative Example 1: The only difference between this comparative example and Example 1 is that the sintering aid precursor tetrabutyl titanate is not added to the raw material formula. The other raw material components, the amount of each component, all preparation methods, and the product preparation process are completely consistent with Example 1.

[0047] Comparative Example 2: The only difference between this comparative example and Example 1 is that no surface modifier γ-methacryloyloxypropyltrimethoxysilane is added, the high refractive index inorganic filler is not subjected to any surface grafting modification treatment, and it is directly used in the original nanopowder form for slurry preparation. The other raw material components, the amount of each component, all preparation methods, and product preparation processes are completely consistent with Example 1.

[0048] Comparative Example 3: The only difference between this comparative example and Example 1 is that the sintering aid precursor tetrabutyl titanate is replaced with an equal amount of rutile nano-titanium dioxide powder with an average primary particle size of 50 nm. The other raw material components, the amount of each component, all preparation methods, and the product preparation process are completely consistent with Example 1.

[0049] Comparative Example 4: The only difference between this comparative example and Example 1 is that the inert atmosphere low-temperature pre-carbonization stage is omitted in the programmed gradient heat treatment process for enamel product preparation. The dried blank is directly placed in an air atmosphere and heated from room temperature to 500°C at a heating rate of 0.5°C / min and held for 90 minutes to complete the hot degreasing. The remaining heating rate, sintering temperature, holding time, raw material composition, and other preparation processes are completely consistent with Example 1.

[0050] Comparative Example 5: This comparative example uses a conventional photocurable 3D printing enamel slurry solution from the prior art. The only difference from Example 1 is that: no sintering aid precursor is added to the raw material formulation; the inorganic filler is an unmodified rutile nano-titanium dioxide and yttrium-stabilized tetragonal nano-zirconia composite powder; and the photosensitive resin is a single epoxy acrylate. The inorganic filler surface grafting modification step and the inert atmosphere pre-dispersion step of the sintering aid precursor are omitted during the preparation process. The heat treatment step adopts the conventional one-step degreasing sintering process in air atmosphere, that is, directly heating from room temperature to 500°C at a heating rate of 1°C / min and holding for 90 minutes, and then heating to 850°C at a heating rate of 4°C / min and holding for 20 minutes. Except for the above adjustments, the total amount of other raw materials is completely consistent with that of Example 1.

[0051] Experiment 1: Rheological Properties and Transmittance Testing of Photocurable 3D Printing Slurry. This experiment referenced GB / T2794 "Determination of Viscosity of Coatings" and GB / T2410 "Determination of Transmittance and Haze of Transparent Plastics". 100g each of the high-refractive-index photocurable 3D printing enamel materials prepared in Examples 1, 2, 3, and Comparative Examples 1, 2, 3, 4, and 5 were taken. All samples were placed in a constant temperature and humidity chamber and allowed to stand for 2 hours at 25℃ and 50% relative humidity. Then, using a rotational viscometer according to the above viscosity determination standards, the viscosity of each sample was measured at 60 r / min using an adapted rotor. The average value of three parallel tests was recorded. After completing the viscosity test, a transmittance meter was used according to the above transmittance determination standards, with a 405nm wavelength light source as the test light source. Each sample was uniformly coated onto a standard quartz glass slide to form a thin film of uniform thickness. The transmittance of each sample was measured in the meter, and the average value of three parallel tests was recorded.

[0052] Experiment 2: Refractive Index Test of Enamel Glaze. This experiment references GB / T7962.1 "Test Methods for Colorless Optical Glass - Part 1: Refractive Index and Dispersion Coefficient". High-refractive-index enamel products obtained through the complete preparation process of Examples 1, 2, 3, and Comparative Examples 1, 2, 3, 4, and 5 were used. Flat test samples of uniform size were cut from the glaze surface of each product. Using an Abbe refractometer according to the above standard, under a test environment of 25°C and with sodium D-rays as the test light source, the refractive index of the glaze layer of each sample was measured at at least five different locations. After removing outliers, the average value was calculated as the final refractive index of the glaze layer of that sample.

[0053] Experiment 3: Enamel Glaze Density and Cross-Cut Adhesion Test. This experiment referenced GB / T25995 "Determination of Apparent Porosity and Bulk Density of Ceramic Materials" and GB / T9286 "Cross-Cut Test of Paint and Varnish Films". Enamel products prepared in Examples 1, 2, and 3, as well as Comparative Examples 1, 2, 3, 4, and 5, were used. First, the density of the glaze layer of each product was tested using Archimedes' water displacement method according to the standard for determining the density of ceramic materials. Defect-free glaze areas on each product were selected, and their mass in the dry state was accurately weighed. Then, their suspended mass in deionized water and their mass after saturation were weighed. The glaze density was calculated using a formula, and the average value of three parallel tests was recorded. After completing the density test, according to the cross-cut test standard, a grid with a spacing of 1 mm was drawn on the glaze surface of each product using a cross-cut tester. The grid depth penetrated the glaze layer to the substrate. Then, a soft brush was used to lightly brush five times along the diagonal direction of the grid. After that, standard pressure-sensitive adhesive tape was applied and quickly peeled off. The glaze layer peeling in the grid area was observed. The adhesion of each sample was rated according to the standard grading rules.

[0054] Table 1: Summary Table of Performance Tests for High-Refractive-Index Photopolymerizable 3D Printed Enamel Materials and Products As can be seen from Examples 1-3 and Comparative Example 1, and Table 1, the sintering aid precursor can decompose to generate nanoscale active centers during the thermal degreasing stage. These active centers can form a composite low-melting-point eutectic system with the silicon and oxygen species remaining after the surface modifier decomposes. This synergistic effect can induce liquid-phase sintering and promote the densification of inorganic filler particles. At the same time, it will also affect the bonding force between the glaze layer and the substrate. The lack of sintering aid precursor will destroy this synergistic effect, thereby affecting the normal performance of the product. As can be seen from Examples 1-3 and Comparative Example 2, and Table 1, the surface modifier can bind to the hydroxyl groups on the surface of the high-refractive-index inorganic filler through chemical bonds, and at the same time provide functional groups that can participate in the photopolymerization reaction. These functional groups can undergo copolymerization with the photosensitive resin matrix to form chemical crosslinking points, construct a stable organic-inorganic interpenetrating network structure green body skeleton, and also improve the compatibility between the inorganic filler and the resin matrix, and avoid filler agglomeration. Without adding the surface modifier and without surface grafting modification of the inorganic filler, the filler dispersibility will be poor, the stability of the green body skeleton will be destroyed, and thus the various properties of the entire product will be adversely affected. Combining Examples 1-3 and Comparative Example 3 with Table 1, it can be seen that the core function of the sintering aid precursor is to decompose and generate active centers during the thermal debinding stage, forming a composite low-melting-point eutectic system with silicon-oxygen species to promote sintering densification. However, when it is replaced with ordinary nano-titanium dioxide powder, this function of decomposing and generating active centers cannot be achieved, and it cannot form a synergistic effect with the silicon-oxygen species remaining after the surface modifier decomposes. It is difficult to achieve the effect of promoting the densification of inorganic fillers and improving product performance. This shows that the type and function of the sintering aid precursor have a key impact on product performance. As can be seen from Examples 1-3 and Comparative Example 4, and Table 1, the inert atmosphere low-temperature pre-carbonization stage in the programmed gradient heat treatment plays an important role. This stage can pre-treat the green body in an inert environment, avoiding the rapid decomposition of organic components in the subsequent hot degreasing stage, which would lead to defects in the green body. This lays a good foundation for subsequent hot degreasing and glazing sintering. If this stage is omitted, the green body will be directly hot degreased in an air atmosphere, which will affect the removal effect of organic components and the formation quality of inorganic porous green bodies, thereby affecting the densification degree of the glaze layer and its adhesion to the substrate. As can be seen from Examples 1-3 and Comparative Example 5, and Table 1, there is a significant synergistic effect among the various technical optimization measures in the embodiments of this application. These include adding sintering aid precursors, surface grafting modification of inorganic fillers, using a photosensitive resin compound system, retaining relevant preparation steps, and using a programmed gradient heat treatment process. These measures work together to effectively improve the rheological properties and light transmittance of the slurry, as well as the refractive index, density, and adhesion of enamel products. However, the existing technical solutions lack these optimization measures, and the various links cannot form a synergistic effect, resulting in product performance that is difficult to reach the level of the embodiments.

[0055] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A high-refractive-index photopolymerizable 3D printing enamel material, characterized in that: The composition by weight is as follows: 30-55 parts photosensitive resin matrix; 40-65 parts high refractive index inorganic filler; 0.5-3 parts surface modifier; 0.1-2 parts sintering aid precursor; 1-6 parts photoinitiator; and 0.5-4 parts dispersing and stabilizing aid.

2. The high refractive index photopolymerizable 3D printing enamel material according to claim 1, characterized in that: The high-refractive-index inorganic filler is a composite powder of nano-titanium dioxide and nano-zirconia, wherein the nano-titanium dioxide is rutile type with an average primary particle size of 30-100 nm, and the nano-zirconia is yttrium-stabilized tetragonal phase with an average primary particle size of 50-150 nm; based on the total mass of the high-refractive-index inorganic filler, the mass proportion of nano-titanium dioxide is 60% to 90%, and the mass proportion of nano-zirconia is 10% to 40%.

3. The high refractive index photopolymerizable 3D printing enamel material according to claim 1, characterized in that: The surface modifier is γ-methacryloyloxypropyltrimethoxysilane.

4. The high refractive index photopolymerizable 3D printing enamel material according to claim 1, characterized in that: The sintering aid precursor is one or more of tetrabutyl titanate, tetrabutyl zirconate, aluminum isopropoxide, or cerium acetylacetone; the photosensitive resin matrix is ​​a compound of epoxy acrylate and polyurethane acrylate, with a compounding ratio of 2:1 to 1:

1.

5. The high refractive index photopolymerizable 3D printing enamel material according to claim 1, characterized in that: The photoinitiator is a compound system of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 1-hydroxycyclohexylphenyl ketone, with a mass ratio of 5:2 to 4:1; the dispersing and stabilizing agent includes a block copolymer type polymeric superdispersant, a polyether-modified polydimethylsiloxane as a leveling agent, and a polysiloxane as an antifoaming agent.

6. A method for preparing a high-refractive-index photopolymerizable 3D printing enamel material, characterized in that, The high refractive index photopolymerizable 3D printing enamel material according to any one of claims 1-5 comprises the following steps: S1. Pre-dispersion of sintering aid precursor: Dissolve the sintering aid precursor in a small amount of photosensitive resin matrix, stir and mix evenly under an inert atmosphere to form a pre-dispersion of sintering aid precursor. S2. Preparation of resin premix: The remaining photosensitive resin matrix is ​​mixed with the dispersion stabilizer and stirred evenly to obtain the resin premix. S3. Preparation of high solids content composite slurry: Modified composite filler and sintering aid precursor pre-dispersion liquid obtained in step S2 are added in batches under stirring conditions. After high shear fine dispersion treatment, photoinitiator is added. After stirring and mixing evenly in the dark, vacuum degassing is performed to finally obtain high refractive index photocurable 3D printing enamel material.

7. The method for preparing a high refractive index photopolymerizable 3D printing enamel material according to claim 6, characterized in that: In step S1, when preparing the pre-dispersion liquid of the sintering aid precursor, the inert atmosphere is nitrogen or argon, the stirring speed is 200-500 rpm, the stirring time is 30-60 min, and the temperature is room temperature to 40°C.

8. The method for preparing a high refractive index photopolymerizable 3D printing enamel material according to claim 6, characterized in that: In step S3, the high-shear fine dispersion treatment adopts a multi-stage gradient grinding process, and is cyclically treated 3-5 times at dispersion gaps of 45-55μm, 20-30μm, and 10-20μm respectively; the modified composite filler is gradually added to the resin premix in 3-5 batches.

9. A method for preparing a high-refractive-index enamel product, characterized in that, The high refractive index photopolymerizable 3D printing enamel material according to any one of claims 1-5 comprises the following steps: A1. Photopolymer additive manufacturing: High refractive index photopolymer 3D printing enamel material is photopolymerized layer by layer to prepare a green blank with a preset three-dimensional structure; A2. Cleaning and drying of the green green body: The green green body is subjected to multi-stage ultrasonic cleaning to remove uncured slurry residue on the surface and in the internal pores. After cleaning, it is dried at low temperature. A3. Programmed gradient heat treatment: The dried green body is placed in a programmed temperature-controlled furnace. First, it is pre-carbonized at low temperature under an inert atmosphere, and then it is switched to an oxidizing atmosphere for hot degreasing treatment to completely remove the organic components in the green body and obtain an inorganic porous green body. Finally, it is heated for glazing and sintering treatment to densify the inorganic filler particles and form a continuous vitrified enamel glaze layer. After natural cooling in the furnace, a high refractive index enamel product is obtained.

10. The method for preparing a high refractive index enamel article according to claim 9, characterized in that: In step A3, the low-temperature pre-carbonization treatment is as follows: under a nitrogen or argon inert atmosphere, the temperature is increased from room temperature to 250-350℃ at a heating rate of 1-2℃ / min, and held for 30-60min; the thermal degreasing treatment is as follows: switching to an air oxidizing atmosphere, first heating from 250-350℃ to 300℃ at a heating rate of 0.8-1.2℃ / min, then heating from 300℃ to 480-520℃ at a heating rate of 0.4-0.6℃ / min, and held for 80-100min; the glazing sintering treatment is as follows: heating to 710-800℃ at a heating rate of 2.5-5.5℃ / min, and held for 10-30min.

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