CN109504135B

CN109504135B - High-temperature coating for glass/glass ceramic hot-pressing treatment and hot-pressing forming method of glass/glass ceramic

Info

Publication number: CN109504135B
Application number: CN201710829174.2A
Authority: CN
Inventors: 胡伟; 陈振宇; 索平平; 常瑞荆
Original assignee: Chongqing Aureavia Hi Tech Glass Co Ltd
Current assignee: Chongqing Aureavia Hi Tech Glass Co Ltd
Priority date: 2017-09-14
Filing date: 2017-09-14
Publication date: 2021-07-30
Anticipated expiration: 2037-09-14
Also published as: CN109504135A

Abstract

The invention is suitable for the field of glass processing, and particularly relates to a high-temperature coating for glass/glass ceramic hot-pressing treatment and a hot-pressing forming method of glass/glass ceramic. The high-temperature coating comprises inorganic matters and organic matters; the inorganic substance comprises at least one amorphous particle which is a glass particle; the organic matter comprises at least two of resin, organic solvent, coupling agent, film forming agent, defoaming agent, dispersing agent, leveling agent and photoinitiator. The protective coating used in the high-temperature environment for the glass/glass ceramic hot press molding treatment comprises organic matters and inorganic matters, wherein the main function of the organic matters is to assist a stable suspension dispersion system of the coating, so that the coating construction is more convenient; the inorganic substance has high heat resistance and is used for protecting glass or glass ceramic subjected to hot pressing.

Description

High-temperature coating for glass/glass ceramic hot-pressing treatment and hot-pressing forming method of glass/glass ceramic

Technical Field

The invention belongs to the field of glass processing, and particularly relates to a high-temperature coating for glass/glass ceramic hot-pressing treatment and a hot-pressing forming method of glass/glass ceramic.

Background

With the popularization of flexible display screens, the application of curved surface special-shaped protective glass matched with the flexible display screens is more and more popularized; on the other hand, on the premise that the requirements of the handheld terminal on the communication speed and strength of wireless signals are higher and higher, non-conductive hard materials such as glass, glass ceramic and the like become mainstream materials, and the hard materials are processed into special-shaped structures by a thermoforming method to meet the comprehensive structural design of the handheld terminal; in the traditional optics industry, most optical lenses in an optical lens are curved glass.

The most popular method for forming curved glass and glass ceramic is a hot press forming method, in which the glass to be processed is placed in a graphite, glass ceramic or metal mold, and is formed under a certain pressure in a closed environment filled with inert protective gas and in a high-temperature environment (usually higher than 630 ℃) near the softening point of the glass. However, the greatest disadvantage of this method is that the process temperature, time or pressure are not well controlled, the mold mark is easily transferred to the area with the largest pressure bearing surface of the processed glass in the forming process, and other surface defects such as scratches, orange peel, small bubbles and the like; the mould prints are usually 10-20 μm deep, the whole surface of the glass is required to be polished to remove the mould prints, the polishing of the formed curved profile glass is very difficult, and the whole surface of the mould prints can be removed by polishing for 1-2 hours by using rare earth polishing powder attached to a brush. The prior method has very low yield and efficiency, the higher the dependence on the die is, the higher the requirement on the surface condition precision of the die is, the higher the processing cost is, and the environmental protection is not facilitated by using a large amount of rare earth and graphite.

Therefore, the prior art has defects and needs to be improved urgently.

Disclosure of Invention

In order to solve the technical problems, the invention provides a high-temperature coating for glass/glass ceramic hot-pressing treatment and a hot-pressing forming method of glass/glass ceramic, aiming at overcoming the problems in the existing hot-pressing forming method of glass/glass ceramic.

The invention is realized in such a way that the high-temperature coating for the hot-pressing treatment of the glass/glass ceramic comprises inorganic matters and organic matters; the inorganic substance comprises at least one amorphous particle which is a glass particle; the organic matter comprises at least two of resin, organic solvent, coupling agent, film forming agent, defoaming agent, dispersing agent, leveling agent and photoinitiator.

Further, the mass ratio of the inorganic matters to the organic matters is 1: 0.05-20.

Further, the inorganic substance also comprises oxide and salt compounds with crystal structures, and the melting temperature of the oxide and salt compounds is more than 630 ℃.

Further, the resin includes at least one of phenolic resin, epoxy resin, petroleum resin, acrylic resin, polyethylene resin, polystyrene resin, polytetrafluoroethylene, polyester resin, and polyamide resin.

Further, the maximum particle size of the glass particles is less than 100 μm, and the central particle size is less than 50 μm; the maximum grain diameter of the oxide and salt compounds is less than 50 μm, and the central grain diameter is less than 25 μm.

Further, the softening point TSa of the glass particles and the softening point TSb of the glass or glass-ceramic are related by: the absolute value of TSb-TSa is not more than 250, and the softening point of the glass particles is 480-1100 ℃.

Further, the mass content of the glass particles in the inorganic substance is more than or equal to 20%; the glass particles include at least one of silicate glass, phosphate glass, borate glass, aluminate glass, chalcogenide glass, bismuthate glass, and halide glass.

The invention also provides a hot-press molding method of the glass/glass ceramic, which comprises the following steps:

coating the high-temperature coating on at least one surface of glass or glass ceramic to obtain a coating layer, and drying;

carrying out hot pressing treatment;

and placing the glass or glass ceramic subjected to the hot pressing treatment in a mold release agent to remove the coating.

Furthermore, the temperature of the hot-pressing treatment is 610-850 ℃, the pressure is less than or equal to 0.98Mpa, and the time is 5-300 s.

Further, the coating method is screen printing, blade coating, spin coating, dip coating or spray coating.

Compared with the prior art, the invention has the beneficial effects that: the high-temperature coating for glass/glass ceramic hot-pressing treatment provided by the embodiment of the invention comprises organic matters and inorganic matters, wherein the main function of the organic matters is to assist a stable suspension dispersion system of the coating, so that the coating is more convenient to coat and construct; the inorganic substance has high heat resistance and is used for protecting glass or glass ceramic subjected to hot pressing.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The first embodiment of the invention provides a high-temperature coating for glass/glass ceramic hot-pressing treatment, which comprises inorganic substances and organic substances; the inorganic substance comprises at least one amorphous particle which is a glass particle; the organic matter comprises at least two of resin, organic solvent, coupling agent, film forming agent, defoaming agent, dispersing agent, leveling agent and photoinitiator.

The high-temperature coating for glass/glass ceramic hot-pressing treatment provided by the first embodiment of the invention comprises organic matters and inorganic matters, wherein the main function of the organic matters is to assist a stable suspension dispersion system of the coating, so that the coating is more convenient to coat and construct; the inorganic substance has high heat resistance and is used for protecting glass or glass ceramic subjected to hot pressing.

The organic solvent is petroleum ether, benzophenone, acetone, terpineol or alcohols (such as ethanol, isopropanol and the like);

the coupling agent is titanate, organosilane, triethylamine and methyldiethanolamine;

the film-forming agent comprises: cellulose film-forming agent, protein film-forming agent, acrylic resin film-forming agent, butadiene resin film-forming agent, polyurethane film-forming agent and nitrocellulose film-forming agent, or modified varieties thereof, such as carboxymethyl cellulose, methyl cellulose, ethyl cellulose, acrylic resin modified casein film-forming agent, acrylic resin polyurethane copolymer resin, polyethylene, acrylate modified butadiene resin, polyurethane modified nitrocellulose film-forming agent and the like; the film forming agent plays a decisive role in the performance of the coating and can form a key material of a continuous and uniform film coating;

the defoaming agent is organosilane or polysiloxane;

the dispersing agent is BYK-450, fatty acids, fatty amides, esters, paraffin, metal salts of higher fatty acids and low molecular wax;

the leveling agent is polytetrafluoroethylene, and various polyethylenes (homopolymers or copolymers), polypropylene, polystyrene or other high-molecular modifiers are used as raw materials and are cracked and oxidized to form a series of oligomers with different properties;

the photoinitiator comprises: radical polymerization photoinitiators, cationic polymerization photoinitiators and the like, and radical type photoinitiators are classified into cleavage type photoinitiators and hydrogen abstraction type photoinitiators according to the action mechanism of generating radicals, and include: benzoin and derivatives, benzils, alkylbenzophenones, acylphosphine oxides, benzophenones, thioxanthones, and the like; the cationic photoinitiator includes onium salts, metal organics, organosilanes, iodonium salts, sulfonium salts, iron aromatics, and the like. The primary purpose of the photoinitiator is to be capable of being excited by ultraviolet light to cause the entire printed coating to be cured.

Specifically, the mass ratio of the inorganic matter to the organic matter is 1: 0.05-20. Further, the mass content of the inorganic matters in the high-temperature coating is 10% -95%, and the mass content of the organic matters in the high-temperature coating is not lower than 3%. The construction mode of the coating can be adjusted according to different mass contents of the inorganic substance in the high-temperature coating, the silk-screen printing requires high viscosity, and the silk-screen printing mode can be used if the inorganic substance content is high (the mass ratio of the inorganic substance to the organic substance is 1: 0.05-1); the spraying needs a mixture ratio with lower viscosity, and the spraying can be used if the content of inorganic matters is low (the mass ratio of the inorganic matters to the organic matters is 1: 2-20). The content of the inorganic substance or the organic substance is too low, so that the corresponding functions and the corresponding technical effects cannot be obtained.

Specifically, the inorganic substance also comprises oxide and salt compounds with crystal structures, and the melting temperature of the oxide and salt compounds is more than 630 ℃. The oxide and salt compounds are used for adjusting the working temperature of the high-temperature coating. The oxide comprises at least one of titanium oxide, silicon oxide, aluminum oxide, zirconium oxide, chromium oxide, copper oxide and iron oxide, and the salt compound comprises at least one of magnesium sulfate, barium sulfate and calcium carbonate. The maximum particle size of the oxide and salt compounds is 2-10 μm.

Specifically, the resin includes at least one of a phenol resin, an epoxy resin, a petroleum resin, an acrylic resin, a polyethylene resin, a polystyrene resin, polytetrafluoroethylene, a polyester resin, and a polyamide resin.

Specifically, the maximum particle size of the glass particles is less than 100 μm, and the central particle size is less than 50 μm; the maximum grain diameter of the oxide and salt compounds is less than 50 μm, and the central grain diameter is less than 25 μm. Research proves that the problem of forming larger concave-convex particles on the surface of the glass after hot pressing treatment and removal of the protective coating film is caused by the overlarge particle size of the inorganic substance.

In particular, the softening point TSa of the glass particles is related to the softening point TSb of the glass or glass-ceramic by: the absolute value of TSb-TSa is not more than 250, and the softening point of the glass particles is 480-1100 ℃. The softening point of the glass particles can ensure that the high-temperature coating can be cured to form a film when the glass/glass ceramic is subjected to hot pressing treatment, the inherent performance can be still maintained, surface defects from a mold are prevented, the glass/glass ceramic is protected, and the hot pressing treatment of the glass/glass ceramic is facilitated.

Specifically, the mass content of the glass particles in the inorganic substance is more than or equal to 20%; the glass particles include at least one of silicate glass, phosphate glass, borate glass, aluminate glass, chalcogenide glass, bismuthate glass, and halide glass.

The second embodiment of the invention provides a hot press molding method of glass/glass ceramic, which comprises the following steps:

carrying out hot pressing treatment;

In the hot press molding method of glass/glass ceramic provided by the second embodiment of the present invention, the high temperature coating provided by the first embodiment of the present invention is applied before the hot press treatment of the glass/glass ceramic, and the coating is directly removed by using alkaline liquid after the treatment. The high-temperature coating protects the surface of the glass/glass ceramic from being changed almost in the hot-pressing treatment process, so that the glass/glass ceramic subjected to hot-pressing treatment does not need to be subjected to curved surface polishing.

Specifically, the hot pressing treatment is to place the glass coated with the dried coating in a mold, and perform hot pressing treatment after the upper and lower molds are closed.

Specifically, the mold closing gap reserved by the upper mold and the lower mold is larger than or equal to the total thickness of the glass and the dry coating. The glass is coated with ink on both sides, so the total thickness of the glass is increased, and if the mold closing gap is maintained to be the same as the original thickness of the glass, the mold closing gap is relatively reduced, so that the ink glass can be cracked after mold closing, and the mold closing gap is larger than or equal to the total thickness of the dry coating and the glass.

Specifically, the upper and lower molds are made of ceramic, metal or graphite molds. The ceramic material is at least one of silicon carbide and silicon nitride, and the metal material is at least one of iron, chromium, tungsten, iridium, molybdenum, titanium or alloy materials thereof.

Specifically, the drying is carried out in an environment with the temperature lower than the hot pressing treatment temperature of the glass or the glass ceramic and higher than 80 ℃ until the surface of the coating is dry and is not sticky. Preferably, the drying temperature is 180-350 ℃, and the drying time is 8-15 minutes. The coating method is screen printing, blade coating, spin coating, dip coating or spray coating.

Specifically, the pH of the release agent can be various values, and when the pH of the release agent is greater than or equal to 7, the release agent contains at least two of a surfactant, a penetrating agent, a pH regulator, alcohols, soaps, an organic base, an inorganic base, a soluble alkaline compound, a solvent and water. When the glass/glass ceramic is placed in alkaline liquid, the surface roughness of the glass/glass ceramic can be obviously changed, and the surface roughness can be increased, wherein the range of the increase is 0.01-0.2 mu m. When the pH value of the release agent is less than 7, the release agent comprises at least two of surfactant, pH regulator, alcohol, soap, organic acid, inorganic acid, soluble acidic compound, solvent and water.

Specifically, the solvent is an aqueous solvent or an oily solvent. The aqueous solvent comprises water, methyl pyrrolidone, terpineol, dipropylene glycol, anisole and dipropylene glycol methyl ether; the oily solvent comprises butyl lower fatty acid, castor oil and nylon acid ester.

Specifically, the temperature of the hot-pressing treatment is 610-850 ℃, the pressure is less than or equal to 0.98Mpa, and the time is 5-300 s. The time is related to the pressure, and when the pressure is high, the time is short, and when the pressure is low, the time is long. The hot pressing temperature is different for different glasses. For example, the softening point of the soda-lime silicate glass is lower, and the hot press molding temperature is also lower, namely 630-730 ℃; the softening point of the high-aluminosilicate glass is higher, and the hot-press forming temperature is correspondingly increased to 700-850 ℃. The hot pressing temperature cannot be increased and is maintained at a level of 700 c. Mainly because there are two important parameters during hot pressing: temperature and time, since the glass is an amorphous material, if the temperature is lower, the time can be extended, or high temperature short time can be used to accomplish the same hot press forming.

Specifically, the surfactant is sulfated castor oil, sodium alkyl sulfonate, sodium alkyl benzene sulfonate, sodium alkyl sulfate, secondary sodium alkyl sulfonate, secondary sodium alkyl sulfate, sodium alpha-olefin sulfonate, sodium alkyl naphthalene sulfonate, sodium alkyl sulfosuccinate, tryptone T, sodium sulfamate, fatty alcohol polyoxyethylene ether, alkylphenol ethoxylates, polyether, phosphate compounds, alcohol compounds, ketones, ethers and the like. The pH regulator is citric acid, oxalic acid, sorbic acid, sodium bicarbonate, disodium hydrogen phosphate, etc.

Preferably, the formula of the release agent is as follows: 5-10% of triethylamine, 5-20% of potassium hydroxide, 15-25% of sodium dodecyl benzene sulfonate, 5-15% of diethanolamine, 5-10% of sodium bicarbonate and 35-60% of deionized water. The pH value is 11-13, the application temperature is 40-80 ℃, and the demoulding time is 5-10 minutes.

The technical scheme of the invention is further explained by combining a comparative example and a specific example.

Comparative example 1

The glass is subjected to hot press molding by adopting a conventional process, and then single-side polishing is carried out for 60min, so that the obtained glass product has 12% of concave-convex points, 3% of indentations, 3% of scratches and 82% of yield.

Example 1

Preparing a high-temperature coating: mixing glass 8205 powder, inorganic particles and an organic solvent according to a mass ratio of 5:2:4, and fully stirring to obtain the high-temperature coating. The inorganic particles are alumina and calcium carbonate which are mixed according to the mass ratio of 7: 3; the maximum particle diameter of the inorganic particles is 2-10 mu m.

The specific process comprises the following steps:

preparation of glass 8205 powder:

TABLE 1

Raw materials	Bi₂O₃	ZnO	TiO₂	ZrO₂	Al₂O₃	MgO	K₂O	Na₂O	SiO₂
										Mass ratio (%)	3.8	5.5	1.9	2.4	15	5	8	15	43.4

(1) Weighing the raw materials in the mass ratio according to the formula of the content of each raw material in the table 1, and mixing and stirring uniformly;

(2) putting into a crucible, and heating to 1300 ℃ or higher to make the glass in a molten state;

(3) introducing molten glass into water for quenching to obtain smaller glass particles;

(4) putting the glass particles obtained in the firing process into a jet mill for crushing;

(5) carrying out air flow classification, and selecting out glass particles with the particle size of less than 100 mu m;

(6) mixing with water (the mass ratio of glass to water to aqueous solvent (such as ethanol) is 50:25:25, and glass to water is 50:50), introducing into a bead mill, grinding, and pulverizing to maximum particle size of less than 50 μm to obtain glass-containing water solution;

(7) heating the water solution containing the glass to completely evaporate the water to obtain glass 8205 powder.

The preparation process of the organic solvent is as follows:

340g of terpineol serving as a solvent is taken and added with 160g C₅Fully stirring the modified petroleum resin; adding 2.4% of ethyl cellulose N-50 as filler, and stirring thoroughly; adding 3% WinSperse3090 and fully stirring; adding SER2035A 3% baking varnish non-silicon defoamer and fully stirring; 8% of JL-156 (titanate coupling agent) was added thereto and sufficiently stirred to obtain an organic solvent solution.

Carrying out hot-press molding on the glass/glass ceramic, wherein the process comprises the following steps:

coating the high-temperature coating on at least one surface of the glass to obtain a coating layer, and drying;

carrying out hot pressing treatment, wherein the temperature of the hot pressing treatment is 650 ℃, the pressure is 0.8Mpa, and the time is 230 s;

and placing the glass subjected to the hot pressing treatment in a release agent to remove the coating.

The formula of the demoulding liquid is as follows: 30 wt% NaHCO₃70 wt% of deionized water, the pH value is 11, the working temperature is 80 ℃, and the demoulding time is 10 min.

Polishing the single surface of the stripped glass for 15min to finally obtain a product with the concave-convex points of 4.36%, the indentation of 1.05%, the scratch of 0.88% and the yield of 91%.

Example 2

Preparing a high-temperature coating: mixing the glass 9205 powder, the inorganic particles and the organic solvent according to the mass ratio of 5:5:4, and fully stirring to obtain the high-temperature coating. The inorganic particles are prepared by mixing barium sulfate, chromium oxide and silicon oxide according to the mass ratio of 4:1: 5; the maximum particle diameter of the inorganic particles is 2-10 mu m.

The specific process comprises the following steps:

preparation of glass 9205 powder:

TABLE 2

Raw materials	B₂O₃	Bi₂O₃	ZnO	TiO₂	ZrO₂	Al₂O₃	MgO	K₂O	Na₂O	SiO₂
											Mass ratio (%)	3.7	3.8	4.5	2.3	3.75	10.85	13.82	17.2	3.28	36.8

(1) Weighing the raw materials in the mass ratio according to the formula of the content of each raw material in the table 2, and mixing and stirring uniformly;

(7) heating the water solution containing glass to evaporate water completely to obtain glass 9205 powder.

The preparation process of the organic solvent is as follows:

carrying out hot pressing treatment, wherein the temperature of the hot pressing treatment is 700 ℃, the pressure is 0.9Mpa, and the time is 100 s;

The formula of the demoulding liquid is as follows: 15 wt% of inorganic base is KOH, 10 wt% of sodium dodecyl benzene sulfonate, 7 wt% of diethanolamine, 5 wt% of triethylamine, 63 wt% of solvent is deionized water, the pH value is 13, the working temperature is 40 ℃, and the demoulding time is 5 min.

Polishing the single surface of the stripped glass for 20min to finally obtain a product with the concave-convex points of 4.36%, the indentation of 1.05%, the scratch of 0.88% and the yield of 100%.

Example 3

Preparing a high-temperature coating: mixing the glass 6205 powder, the inorganic particles and the organic solvent according to the mass ratio of 5:8:4, and fully stirring to obtain the high-temperature coating. The inorganic particles are alumina, zirconia and magnesium sulfate and are mixed according to the mass ratio of 1:6: 3; the maximum particle diameter of the inorganic particles is 2-10 mu m.

The specific process comprises the following steps:

preparation of glass 6205 powder:

TABLE 3

(1) Weighing the raw materials in the mass ratio according to the formula of the content of each raw material in the table 3, and mixing and stirring uniformly;

(7) heating the water solution containing glass to evaporate water completely to obtain glass 6205 powder.

The preparation process of the organic solvent is as follows:

340g of terpineol serving as a solvent is taken,160g C was added₅Fully stirring the modified petroleum resin; adding 2.4% of ethyl cellulose N-50 as filler, and stirring thoroughly; adding 3% WinSperse3090 and fully stirring; adding SER2035A 3% baking varnish non-silicon defoamer and fully stirring; 8% of JL-156 (titanate coupling agent) was added thereto and sufficiently stirred to obtain an organic solvent solution.

carrying out hot pressing treatment, wherein the temperature of the hot pressing treatment is 850 ℃, the pressure is 0.98Mpa, and the time is 5 s;

The formula of the demoulding liquid is as follows: 20 wt% of inorganic base NaOH, 5 wt% of triethylamine and 75 wt% of solvent deionized water, wherein the pH value is 12, the working temperature is 60 ℃, and the demoulding time is 8 min.

Polishing the single surface of the stripped glass for 10min to finally obtain a product with concave-convex points of 2.36%, indentation of 3.09%, scratch of 1.75% and yield of 98%.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims

1. A hot press molding method of glass or glass ceramic is characterized by comprising the following steps:

coating high-temperature paint on at least one surface of the glass or the glass ceramic to obtain a paint coating, and drying;

carrying out hot pressing treatment;

placing the glass or glass ceramic subjected to the hot pressing treatment in a release agent to remove the coating;

the high-temperature coating comprises inorganic matters and organic matters; the inorganic substance comprises at least one amorphous particle which is a glass particle; the organic matter comprises at least two of resin, an organic solvent, a coupling agent, a film forming agent, a defoaming agent, a dispersing agent, a flatting agent and a photoinitiator;

wherein the glass particles are prepared as follows: the raw materials by mass ratio: 3.8% Bi₂O₃、5.5%ZnO、1.9%TiO₂、2.4%ZrO₂、15%Al₂O₃、5%MgO、8%K₂O、15%Na₂O、43.4%SiO₂Carrying out preparation;

weighing the raw materials according to the weight proportion according to the formula of the content of the raw materials, and mixing and stirring uniformly;

putting into a crucible, and heating to 1300 ℃ or higher to make the glass in a molten state;

introducing molten glass into water for quenching to obtain smaller glass particles;

putting the glass particles obtained in the firing process into a jet mill for crushing;

carrying out air flow classification, and selecting out glass particles with the particle size of less than 100 mu m;

mixing with water at a mass ratio of glass to water = 50:50, introducing into a bead mill, and grinding until the maximum particle size is less than 50 μm to obtain a water solution containing glass;

heating the water solution containing the glass to completely evaporate the water to obtain the glass particles.

2. The method according to claim 1, wherein the hot pressing treatment temperature is 610-850 ℃, the pressure is 0.98Mpa or less, and the time is 5-300 s.

3. The thermoforming method of claim 1, wherein the coating method is screen printing, blade coating, spin coating, dip coating, or spray coating.

4. The molding method according to claim 1, wherein the mass ratio of the inorganic substance to the organic substance is 1:0.05 to 20.

5. The molding method according to claim 1, wherein the inorganic substance further comprises an oxide and salt compound having a crystal structure, and the melting temperature of the oxide and salt compound is more than 630 ℃.

6. The molding method according to claim 1, wherein the resin comprises at least one of a phenol resin, an epoxy resin, a petroleum resin, an acrylic resin, a polyethylene resin, a polystyrene resin, a polytetrafluoroethylene, a polyester resin, and a polyamide resin.

7. The molding method according to claim 5, wherein said oxide and salt compounds have a maximum particle size of less than 50 μm and a central particle size of less than 25 μm.

8. The molding method according to claim 1, wherein the inorganic substance contains glass particles in an amount of 20% by mass or more.