Coating composition for forming a film and method for producing a coated substrate

Abstract

The present invention addresses the problem of providing a coating composition for forming a coating film, the coating composition being capable of forming a fully cured coating film in a short time. The problem is solved by a coating composition for forming a coating film, the coating composition containing titanium-based particles as a filler, an alkoxysilane as a matrix, and 1,2,3,4-butanetetracarboxylic acid as a curing agent, wherein the content of the 1,2,3,4-butanetetracarboxylic acid is at least 0.8 mass%, and the ratio (WF / WM) of the content (WF) of the filler to the content (WM) of the matrix is in the range of 1-4.

Description

[Technical Field]

[0001] The present invention relates to a coating composition for forming a film and a method for producing a coated substrate. [Background technology]

[0002] In recent years, a wide variety of coatings have been used in the optical field. For example, anti-reflection coatings that reduce reflected light, water-repellent coatings that repel water, and hard coatings that protect substrates from physical impacts are used in optical lenses and films. In recent years, plastic substrates have increasingly replaced inorganic glass substrates as materials for optical lenses, particularly eyeglass lenses. This is because plastic substrates have excellent properties such as light weight, impact resistance, processability, and dyeability. Furthermore, in recent years, improvements and developments in materials have been made, resulting in lighter weight and higher refractive indexes. However, these plastic lens substrates have the disadvantage of being more easily scratched than inorganic glass substrates. To avoid this drawback, a silicone-based thermosetting coating, i.e., a hard coating layer, is usually applied to the surface of the plastic lens substrate. Such optical lenses and films are mass-produced and distributed worldwide. From the perspective of further improving the production efficiency of these lenses and films, there has been a need for a coating-forming coating composition that can form a coating in a short period of time while taking advantage of the hardness unique to silicone-based thermosetting coatings.

[0003] For example, Patent Document 1 discloses that the heating time required to form a hard coat layer can be shortened by using a coating composition for forming a hard coat layer, which comprises surface-coated inorganic oxide particles (α0) in which inorganic oxide particles (β0) selected from the group consisting of aluminum oxide particles, silicon oxide particles, titanium oxide particles (β), and zirconium oxide particles are surface-coated with a quaternary alkoxysilane, a hydrolyzate and / or condensate of an organosilicon compound having an epoxy group, 1,2,3,4-butanetetracarboxylic acid, and a curing agent, wherein the number-average molecular weight of the hydrolyzate and / or condensate is 80 to 500, and the content of the 1,2,3,4-butanetetracarboxylic acid is 8 to 25 parts by mass per 100 parts by mass of the surface-coated inorganic oxide particles (α0). However, there has been a demand for a coating composition for forming a hard coat layer that can form a coating in a shorter time. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. WO2022 / 230864 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a coating composition for forming a film, which is capable of forming a sufficiently cured film on a substrate in a short period of time, and a method for producing a coated substrate. [Means for solving the problem]

[0006] The present inventors have discovered a coating composition containing titanium-based particles as a filler, alkoxysilane as a matrix, and 1,2,3,4-butanetetracarboxylic acid as a curing agent, wherein the content of the 1,2,3,4-butanetetracarboxylic acid is 0.8 mass % or more, and the content of the filler (W F ) and the matrix content (W M ) and the ratio (W F / WM ) is in the range of 1 to 4, a sufficiently cured coating can be formed in a short time, and the present invention has been completed based on this finding. DETAILED DESCRIPTION OF THE INVENTION

[0007] The present invention includes an invention relating to a coating composition for forming a film that can form a sufficiently cured coating in a short time (hereinafter also referred to as the "coating composition of the present invention"). The coating composition of the present invention will be described in detail below. In the present invention, when a numerical range is indicated by "to", the numerical range includes both the upper and lower limits. For example, when "1 to 2" is stated, it means "1 or more and 2 or less."

[0008] [Paint composition of the present invention] The coating composition of the present invention contains titanium-based particles as a filler, an alkoxysilane as a matrix, and 1,2,3,4-butanetetracarboxylic acid as a curing agent, and the content of the 1,2,3,4-butanetetracarboxylic acid is 0.8 mass% or more, and the content of the filler (W F ) and the matrix content (W M ) and the ratio (W F / W M ) is in the range of 1 to 4. The coating composition of the present invention will be described in detail below.

[0009] [Filler] The coating composition of the present invention contains titanium-based particles as a filler. In this context, filler refers to a filler commonly used in the optical field. This filler has functions such as refractive index adjustment, anti-reflection, UV protection, and antibacterial properties, and serves to impart these functions to the coating. Titanium-based particles are inorganic compounds with these functions and are one of the materials commonly used in the optical field. For example, titanium oxide particles can exhibit the above-mentioned functions. Below, the titanium-based particles contained in the coating composition of the present invention will be described in detail, focusing on titanium oxide particles. However, the titanium-based particles of the present invention are not limited to titanium oxide particles. Any particles containing titanium and having the above-mentioned functions can be included in the titanium-based particles of the present invention.

[0010] It is known that the properties of titanium oxide particles vary greatly depending on their crystal structure. Known crystal structures of titanium oxide particles include anatase, rutile, and brookite. In the optical field, titanium oxide particles with anatase or rutile crystal structures, which have high refractive indices, are used.

[0011] The average particle size of the titanium oxide particles is preferably in the range of 1 nm to 200 nm, more preferably in the range of 5 nm to 100 nm, and particularly preferably in the range of 5 nm to 50 nm. When titanium oxide particles having an average particle size within the above range are used, the coloring of the titanium oxide particles themselves is reduced, resulting in a more transparent coating. Such transparent coatings are suitable for use in the optical field. The average particle size refers to a value calculated by cumulant analysis from particle size distribution data obtained using a dynamic scattering method (ELS-Z, manufactured by Otsuka Electronics Co., Ltd.).

[0012] The coating composition of the present invention preferably contains silica particles as a filler together with titanium-based particles. The silica particles are particles whose particle shape, such as silica sol and fumed silica, can be confirmed under a microscope with a clear outer edge. By including such silica particles as a filler, the coating composition of the present invention can obtain a coating that is more fully cured in a short period of time.

[0013] The average particle size of the silica particles is preferably in the range of 1 nm to 200 nm, more preferably in the range of 5 nm to 100 nm, and particularly preferably in the range of 5 nm to 50 nm. Using silica particles with an average particle size within the above range allows for the formation of a sufficiently cured coating in a shorter time. This average particle size refers to a value calculated by cumulant analysis from particle size distribution data obtained using a dynamic scattering method (ELS-Z, manufactured by Otsuka Electronics Co., Ltd.).

[0014] The filler content (W F The filler content (unit: mass %) is preferably in the range of 5% to 40% by mass, more preferably in the range of 10% to 35% by mass, and particularly preferably in the range of 10% to 30% by mass, relative to the total mass of the coating composition. When a coating composition having a filler content within the above range is used, a coating that is more sufficiently cured can be obtained in a short period of time.

[0015] The content of titanium-based particles in the coating composition of the present invention (W Ti : The unit is mass % and the silica particle content (W Si : The unit is the ratio of mass% to Ti / W Si ) is preferably in the range of 0.01 to 1, more preferably in the range of 0.1 to 0.9, and particularly preferably in the range of 0.2 to 0.8. When a coating composition having a mass ratio of titanium-based particles to silica particles in the above-mentioned range is used, a coating that is more sufficiently cured can be obtained in a short period of time.

[0016] [matrix] The coating composition of the present invention contains an alkoxysilane as a matrix. The term "matrix" as used herein refers to a component that hardens to form a coating. This matrix hardens to fix the filler in the coating and form a coating that adheres well to the substrate to which it is applied. Alkoxysilane is a general term for compounds in which an alkoxy group is bonded to silicon. An alkoxy group (Si-OR; R = alkyl, etc.) undergoes a hydrolysis reaction to form a silanol group (Si-OH), and these silanol groups undergo dehydration condensation to form a siloxane (Si-O-Si). This reaction hardens the alkoxysilane, ultimately forming a coating with the filler dispersed therein. Representative alkoxysilanes include tetramethoxysilane and tetraethoxysilane. The coating composition of the present invention may also contain a resin as a matrix along with the alkoxysilane.

[0017] The alkoxysilane is preferably an alkoxysilane having an epoxy group. In the present invention, the alkoxysilane having an epoxy group is represented by the following general formula (I): R1 a R2 b Si(OR3) 4-(a+b) (I) In general formula (I), R1 is a functional group containing an epoxy group and having 8 or less carbon atoms, R2 is an alkyl group having 1 to 3 carbon atoms, a cycloalkyl group having 3 carbon atoms, a halogenated alkyl group having 1 to 3 carbon atoms, or an allyl group, and R3 is an alkyl group having 1 to 4 carbon atoms or a cycloalkyl group having 3 to 4 carbon atoms. In addition, a and b are numbers in the range of 0 to 4, and a+b does not exceed 4.

[0018] Examples of alkoxysilanes having epoxy groups represented by general formula (I) include α-glycidoxymethyltrimethoxysilane, α-glycidoxyethyltrimethoxysilane, β-glycidoxyethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, β-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane, and β-(3,4-epoxycyclohexyl)-ethyltriethoxysilane. In the present invention, at least one selected from γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, and β-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane is preferred. Furthermore, some of the alkoxy groups may be hydrolyzed. Using such a compound as a matrix allows for the formation of a coating that exhibits excellent adhesion to the substrate and scratch resistance.

[0019] The matrix content (W M The matrix content (unit: mass %) is preferably in the range of 1 mass % to 40 mass %, more preferably in the range of 5 mass % to 35 mass %, and particularly preferably in the range of 10 mass % to 30 mass %, relative to the total mass of the coating composition. When a coating composition having a matrix content within the above range is used, a coating that is more sufficiently cured can be obtained in a short period of time.

[0020] [Hardening agent] The coating composition of the present invention contains 1,2,3,4-butanetetracarboxylic acid (hereinafter also referred to as "BTCA") as a curing agent. The curing agent functions to bond silanol groups obtained by hydrolysis of the aforementioned alkoxysilane through a dehydration reaction. In the coating composition of the present invention, 1,2,3,4-butanetetracarboxylic acid is an important element for obtaining a coating that is sufficiently cured in a short period of time.

[0021] The 1,2,3,4-butanetetracarboxylic acid content (W BTCA(unit: mass %) is 0.8 mass % or more, preferably in the range of 1 to 8 mass %, more preferably in the range of 1 to 5 mass %, and particularly preferably in the range of 2.9 to 4 mass %, based on the total mass of the coating composition. Even with such a low 1,2,3,4-butanetetracarboxylic acid content, the coating composition of the present invention can form a sufficiently cured coating in a short period of time.

[0022] The ratio of the content (mass%) of 1,2,3,4-butanetetracarboxylic acid to the content (mass%) of titanium-based particles contained in the coating composition of the present invention (W BTCA / W Ti ) is preferably in the range of 0.01 to 1.00, more preferably in the range of 0.05 or more and less than 0.75, and particularly preferably in the range of 0.10 or more and less than 0.50. A coating composition of the present invention in which the mass ratio of 1,2,3,4-butanetetracarboxylic acid to titanium-based particles is in the above-mentioned range can form a coating that is more sufficiently cured in a short period of time.

[0023] The coating composition of the present invention may contain a curing agent other than 1,2,3,4-butanetetracarboxylic acid, and preferably contains a cyanamide derivative compound as the curing agent. Examples of cyanamide derivative compounds include guanidine, guanidine organic acids, guanidine inorganic acid salts, alkyl guanidines, aminoguanidine, and dicyandiamide. Examples of guanidine organic acids include guanidine acetic acid and guanidine propionic acid. Examples of guanidine inorganic acid salts include guanidine hydrochloride, guanidine nitrate, and guanidine phosphate. Examples of alkyl guanidines include n-dodecylguanidine. Among these, it is preferable to contain at least one selected from guanidine organic acids, guanidine inorganic acid salts, and dicyandiamide.

[0024] [W F / W M ] The coating composition of the present invention has a filler content (W F ) (mass%) and the matrix content (W M ) (mass%) and the ratio (W F / WM ) is in the range of 1 to 4, preferably in the range of 1 to 3, and more preferably in the range of 1 to 2.5. This ratio is important for the coating composition of the present invention, and is higher than that of the coating composition of Patent Document 1. By containing 0.8 mass % or more of 1,2,3,4-butanetetracarboxylic acid and keeping this ratio within the above-mentioned range, a coating that is sufficiently cured can be formed in a short time.

[0025] [Optional additives] In addition to the filler, matrix, and curing agent, the coating composition of the present invention preferably contains optional additives, such as a hydrolysis catalyst, a leveling agent, an ultraviolet absorber, and a light stabilizer. The hydrolysis catalyst functions to promote the reaction of hydrolyzing the alkoxy groups contained in the alkoxysilane of the matrix to generate silanol groups. The coating composition of the present invention preferably contains an inorganic acid as the hydrolysis catalyst, and more preferably contains hydrochloric acid. The leveling agent also functions to orient on the surface of the coating composition and improve the smoothness of the coating film. The coating composition of the present invention preferably contains a surfactant as a leveling agent, more preferably a silicone surfactant such as polyoxyalkylene dimethyl polysiloxane, or a fluorine-based surfactant such as a perfluoroalkyl carboxylate or a perfluoroalkyl ethylene oxide adduct, and particularly preferably a silicone surfactant. Furthermore, the ultraviolet absorber has the function of suppressing deterioration of the substrate due to ultraviolet rays. The coating composition of the present invention preferably contains a benzophenone-based ultraviolet absorber, a benzotriazole-based ultraviolet absorber, or the like as the ultraviolet absorber. In addition, the light stabilizer has the function of removing radicals generated by the titanium-based particles when they absorb light, thereby preventing deterioration of the coating film. The coating composition of the present invention preferably contains a hindered amine-based light stabilizer. The content of these optional additives (W EA ) is preferably in the range of 0 mass % to 2 mass %, more preferably in the range of 0 mass % to 1 mass %, relative to the total mass of the coating composition.

[0026] [solvent] The coating composition of the present invention contains a solvent. In the present invention, the solvent is a liquid for dispersing the filler, matrix, curing agent, and optional additives. The inclusion of a solvent increases the fluidity of the coating composition of the present invention, making it easier to apply to a substrate. The coating composition of the present invention preferably contains, as a solvent, water such as distilled water or pure water; alcohols such as methanol, ethanol, and propanol; ketones such as methyl ethyl ketone and diacetone alcohol; esters such as ethyl acetate and butyl acetate; and cellosolves such as ethyl cellosolve and butyl cellosolve. It is more preferable that the coating composition contains a lower alcohol such as methanol or water. Furthermore, these solvents may be used alone or in combination of two or more.

[0027] The coating composition of the present invention can be used as a coating for forming on the surface of a substrate a coating such as an antireflection layer for reducing reflected light, a water-repellent layer for repelling water, a hard coat layer for protecting the substrate from physical impacts, etc., a primer layer for improving adhesion to the substrate, etc. The coating composition of the present invention is preferably used as a coating composition for forming a hard coat film.

[0028] [Method of manufacturing the coating composition of the present invention] The coating composition of the present invention can be prepared, for example, by a method of mixing titanium-based particles, 1,2,3,4-butanetetracarboxylic acid, and an alkoxysilane. Hereinafter, a method of producing the coating composition of the present invention will be described in detail, taking this method as an example, but the method of producing the coating composition of the present invention is not limited to this method.

[0029] In this manufacturing method, it is preferable to mix the titanium-based particles with 1,2,3,4-butanetetracarboxylic acid after partially or completely hydrolyzing the alkoxysilane. The hydrolysis of the alkoxysilane can be promoted by mixing water with a hydrolysis catalyst. For example, the use of an aqueous solution containing an inorganic acid can efficiently promote the hydrolysis of the alkoxysilane. Furthermore, the degree of progress of the hydrolysis of the alkoxysilane can be controlled by the amount of water added. In this way, by mixing the titanium-based particles with 1,2,3,4-butanetetracarboxylic acid in a state in which the alkoxysilane has been partially or completely hydrolyzed, a coating composition that cures in a shorter time can be obtained.

[0030] [Method of manufacturing the coated substrate of the present invention] The present invention includes an invention relating to a method for producing a coated substrate (hereinafter also referred to as "the production method of the present invention"). The method of the present invention will be described in detail below.

[0031] The manufacturing method of the present invention comprises a coating preparation step of preparing a coating composition for forming a coating containing titanium-based particles; a coating step of applying the coating composition to a substrate to obtain a coated substrate; and a coating formation step of curing the coated substrate at a temperature range of 100°C to 150°C for 30 minutes or less to obtain a coated substrate. A feature of the manufacturing method of the present invention is that the coating can be formed in a short time of 30 minutes or less. In the technical field of hard coating films containing titanium-based particles, which typically involve slow curing over time through two-stage heat treatment (pre-curing and main curing), it is difficult even for those skilled in the art to achieve the characteristic of curing in a short time of 30 minutes or less. This method is superior to the aforementioned Patent Documents 1 and 2 in that it can form a sufficiently cured coating even in such a short time. The coated substrate obtained using this manufacturing method has excellent cost performance due to the shortened manufacturing time. Furthermore, in addition to cost performance, it is expected to contribute to energy conservation and environmental protection from the perspective of the SDGs. Each step is described in detail below.

[0032] [Paint preparation process] In this step, a coating composition for forming a film containing titanium-based particles is prepared. As the coating composition for forming a film containing titanium-based particles, it is preferable to use, for example, the coating composition of the present invention described above. However, it is not necessary to use the coating composition of the present invention as long as the coating composition can achieve the characteristic of the method of the present invention, which is to cure in 30 minutes or less.

[0033] [Coating process] In this step, the coating composition prepared in the previous step is applied to a substrate to obtain a coated substrate. Conventionally known substrates can be used in this step. For example, glass substrates and plastic substrates can be used. As plastic substrates, polycarbonate resins, polyamide resins, PMMA resins, allyl resins, polythiourethane resins, polythioepoxy resins, etc. are preferably used. Furthermore, known methods such as dipping and spin coating can be used to apply the coating composition to the substrate. By such methods, a coated substrate can be obtained in which the coating composition is applied to the surface of the substrate.

[0034] [Film formation process] In this step, the coated substrate obtained in the previous step is cured in a temperature range of 100°C to 150°C for 30 minutes or less to obtain a coated substrate. The time in this step refers to the total time the coated substrate is exposed to the temperature range. In this step, curing is preferably carried out for a time range of 10 to 30 minutes, and more preferably for a time range of 10 to 20 minutes.

[0035] In this process, the coated substrate is preferably cured in a temperature range of 100°C to 140°C, more preferably in a temperature range of 100°C to 130°C, and particularly preferably in a temperature range of 100°C to 120°C. Furthermore, it is preferable not to perform pre-curing in this process. Specifically, not performing pre-curing refers to a so-called one-stage heat treatment in which heating, holding, and cooling are each performed only once. Conventional methods typically perform a so-called two-stage heat treatment in which heating, holding, and cooling are performed for pre-curing, and then heating, holding, and cooling are performed again for main curing after the state of pre-curing is confirmed. In the present invention, even if pre-curing is not performed and only main curing is performed by fixing the temperature within the aforementioned temperature range, a coating with extremely little cracking or curling can be formed. Furthermore, not performing pre-curing enables the process to be simplified and the time to be reduced, thereby enabling the production of a coated substrate with excellent cost performance.

[0036] The thickness of the coating formed in this process varies depending on the type of film to be formed. For example, the thickness of the hard coat layer is preferably in the range of 1.0 μm to 5.0 μm, more preferably 1.5 μm to 3.5 μm. The thickness can be adjusted by the amount of liquid applied to the substrate and the number of applications. Furthermore, when forming a hard coat layer, the refractive index of the hard coat layer is preferably adjusted to 1.52 or higher, more preferably 1.57 to 1.75. The refractive index of the hard coat layer can be adjusted by the refractive index of the filler contained in the coating composition. In addition, depending on the intended use, an anti-reflection layer may be formed on the surface opposite the adhesive surface between the hard coat layer and the substrate, or a primer layer may be formed between the substrate and the hard coat layer. The anti-reflection layer and primer layer may be formed using the coating composition of the present invention or a conventionally known coating composition. [Example]

[0037] The production method of the present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0038] The measurement and evaluation methods used in the examples are as follows [1] and [2].

[0039] [1] Dyeing test When a coated substrate is immersed in a dye solution, the dye passes through the coating and the substrate is dyed. If the coating is sufficiently hardened, not much dye passes through the coating, and the substrate is not dyed. On the other hand, if the coating is not sufficiently hardened, more dye passes through the coating, and the substrate is dyed. This phenomenon was used to evaluate whether the coating was sufficiently hardened. Specifically, the coated substrate obtained in each of the Examples and Comparative Examples was immersed in a dye under the conditions (1) below, and then the luminous transmittance (%) of the dyed lens was measured using the luminous transmittance measuring device (2) below. (1) Dyeing conditions Dye name: Optisafe Gray #C250-10 (Phantom Research Laboratories Inc.) Dye concentration: 2.6% by weight Dispersion medium: Purified water Dyeing temperature and time: 92℃-10 minutes (2) Luminous transmittance measurement Measuring instrument: Visual transmittance checker TLV-304 (manufactured by Asahi Spectroscopy Co., Ltd.)

[0040] [2] Membrane physical properties For the coated substrates obtained in each of the Examples and Comparative Examples, the reflectance spectra of the coating and substrate were measured using an optical measuring device (USPM-RU III manufactured by Olympus Corporation), and the film thickness and refractive index of the coating were calculated.

[0041] In each of the examples and comparative examples, the following raw materials were used.

[0042] [Raw material: filler] Titanium-based particle 1 dispersion: commercially available titania sol (product name: OPTOLAKE 1130Z (8RU-25·A15), manufactured by JGC Catalysts and Chemicals Co., Ltd., titanium-based particle content: 30% by mass, average particle diameter: 13 nm, dispersion medium: methanol) Titanium-based particle 2 dispersion: commercially available titania sol (product name: 1130Z (8RX-7·A15), manufactured by JGC Catalysts and Chemicals Co., Ltd., titanium-based particle content: 30% by mass, average particle diameter: 13 nm, dispersion medium: methanol) Silica particle dispersion: commercially available silica sol (product name: SI-30, manufactured by JGC Catalysts and Chemicals Co., Ltd., silica particle content: 30% by mass, average particle diameter: 11 nm, dispersion medium: water)

[0043] [Raw material: Matrix] γ-Glycidoxypropyltrimethoxysilane (also known as γ-GTS): (Product name: SILQUEST A-187, manufactured by Momentive Performance Materials Japan, LLC)

[0044] [Raw material: hardener] 1,2,3,4-butanetetracarboxylic acid (also known as "BTCA") (product name, manufactured by Kanto Chemical Co., Ltd., purity 98% by mass) Itaconic acid (product name, Kanto Chemical Co., Ltd., purity 98% by mass) Dicyandiamide (also known as "DICY") (product name, manufactured by Kishida Chemical Co., Ltd., purity 99%)

[0045] [Raw materials: optional additives] Hydrolysis catalyst: 0.01N hydrochloric acid solution Leveling agent: Silicone surfactant (product name: DOWSIL L-7001, manufactured by Dow Toray Industries, Inc.)

[0046] [Raw material: solvent] Methanol (also known as "MeOH") (product name: Methanol, manufactured by Hayashi Pure Chemical Industries, Ltd.) Propylene glycol monomethyl ether (PGME) (product name: 1-methoxy-2-propanol, manufactured by Kishida Chemical Co., Ltd.)

[0047] [Example 1] [Preparation of Coating Composition] 46.7 g of γ-glycidoxypropyltrimethoxysilane was mixed with 7.0 g of methanol, and 13.8 g of 0.01 N aqueous hydrochloric acid was added dropwise to the resulting solution while stirring. The resulting solution was stirred overnight at room temperature. Next, 15.5 g of methanol, 137.8 g of titanium-based particle 1 dispersion, 91.9 g of silica particle dispersion, 19.0 g of propylene glycol monomethyl ether, 8.0 g of 1,2,3,4-butanetetracarboxylic acid, 2.9 g of dicyandiamide, and 0.6 g of leveling agent were added and stirred overnight at room temperature to prepare a coating composition. The properties of the resulting coating composition are shown in Table 2.

[0048] [Preparation of coated substrate] A lens made of CR-39 (allyl diglycol carbonate) (product name: 150UC, manufactured by Shanghai Conant Optics Co., Ltd.) was immersed in an 8% NaOH aqueous solution for 10 minutes to perform an etching treatment. The coating composition was applied to the etched lens surface by dipping, adjusting the pulling speed so that the film thickness would be 2.8 to 3.3 μm. The lenses coated with the coating compositions were then heated at 120°C for 10 minutes to prepare coated substrates, and the substrates were heated at 120°C for 30 minutes to prepare coated substrates. The stainability evaluation test described above in [1] was carried out on each coated substrate. The results are shown in Table 3.

[0049] [Examples 2 to 10, Comparative Examples 1 to 4] A coating composition was prepared in the same manner as in Example 1, except that the type and amount of each component were changed as shown in Table 1. Furthermore, a coated substrate was prepared using the resulting coating composition in the same manner as in Example 1. The resulting coated substrate was subjected to the dyeability evaluation test described above in [1]. The results are shown in Table 3.

[0050] [Table 1]

[0051] [Table 2]

[0052] [Table 3]

[0053] This application claims priority based on Japanese Patent Application No. 2023-167692, filed September 28, 2023, the disclosure of which is incorporated herein in its entirety.

Claims

1. Contains titanium oxide particles and silica particles as fillers, the filler content is in the range of 5% by mass to 40% by mass, The matrix contains an alkoxysilane containing an epoxy group, the matrix content is in the range of 1% by mass to 40% by mass, Contains 1,2,3,4-butanetetracarboxylic acid as a hardener. the content of the 1,2,3,4-butanetetracarboxylic acid is in the range of 1% by mass to 8% by mass, The content of the filler (W F ) and the matrix content (W M ) and the ratio (W F / W M ) is in the range of 1 to 4, Coating composition for film formation.

2. The content of the titanium-based particles (W Ti ) and the content of the silica particles (W Si 2. The coating composition for forming a film according to claim 1, wherein the ratio (W Si / W Ti ) of W Si to W Ti is in the range of 0.01 to 1.

3. A coating process in which the coating composition for forming a film according to claim 1 or 2 is applied to a substrate to obtain a coated substrate; a coating forming step of curing the coated substrate at a temperature of 100°C to 150°C for 30 minutes or less to obtain a coated substrate; Method for producing coated substrate.

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