Aqueous inner surface antireflection coating material, inner surface antireflection coating film, and glass optical element

Abstract

Provided is an aqueous inner surface antireflection coating material having good workability and storage stability and capable of obtaining a coating film excellent in adhesion to a glass substrate and solvent resistance. This aqueous inner surface antireflection coating material for a glass optical element comprises a dispersion containing carbon black and a hydroxyl group-containing acrylic emulsion, a polyisocyanate compound, and an epoxy group-containing compound, the aqueous inner surface antireflection coating material being characterized in that the hydroxyl value of the solid content of the hydroxyl group-containing acrylic emulsion is 5-50 mgKOH / g, the carbon black is coated with a nonionic surfactant, and 15-25 parts by mass of the carbon black is contained in 100 parts by mass of the solid content of the aqueous inner surface antireflection coating material.

Description

Water-based internal anti-reflection paint, internal anti-reflection coating film, and glass optical element

[0001] The present invention relates to a water-based internal antireflection coating material, an internal antireflection coating film formed using the water-based internal antireflection coating material, and a glass optical element having the internal antireflection coating film.

[0002] In an optical system constructed by combining optical elements such as lenses and prisms, if light is scattered around the edges, ridges, edges, and other peripheral portions of each optical element, causing stray light, ghosts and flares will appear in the image formed by the optical system, resulting in a deterioration in image quality. Therefore, in order to suppress the deterioration in image quality caused by such stray light, optical elements are used that suppress the occurrence of ghosts and flares by applying an internal anti-reflective coating to the peripheral portions of the optical elements and forming a black internal anti-reflective coating film to prevent internal reflections.

[0003] Traditionally, epoxy-based paints using organic solvents have been widely used as black paints with the function of preventing stray light reflection. However, in recent years, growing environmental concerns have led to an increasing demand for environmentally friendly internal anti-reflection paints that use less volatile organic compounds (VOCs).

[0004] In order to reduce VOC emissions into the environment, it is conceivable to use an aqueous medium instead of an organic solvent as the paint medium.

[0005] Patent Document 1 proposes an aqueous multi-component polyurethane coating composition that contains a first component (X) and a second component (Y) and that exhibits excellent coating film appearance, corrosion resistance, water resistance, and coating film hardness. The first component (X) contains a hydroxyl-containing resin emulsion (A), a pigment (C), and water. The second component (Y) contains an epoxy-containing compound (B) having an epoxy equivalent of 100 to 1,000 g / eq, a polyisocyanate compound (D), and an organic solvent (E).

[0006] Patent Document 2 proposes a highly jet-black carbon black dispersion characterized by dispersing specific carbon black into fine particles in an aqueous medium using a pigment dispersant. Patent Document 2 also describes an ink composition in which the highly jet-black carbon black dispersion is uniformly mixed with an acrylic-urethane copolymer emulsion. The specific carbon black has a DBP oil absorption of 150 ml / 100 g or less, an average primary particle diameter of 15 nm or less, and a specific surface area of ​​500 m ２ / g or less and has a pH in the acidic to neutral range.

[0007] JP 2024-31829 A JP 2008-285632 A

[0008] In the aqueous multi-component polyurethane coating composition described in Patent Document 1, when carbon black is used as the pigment (C), gelation may occur with only the first component (X), resulting in significantly poor workability and storage stability. Furthermore, the ink composition described in Patent Document 2 results in coating films that are insufficient in solvent resistance and adhesion to glass. Furthermore, when the highly jet-black carbon black dispersion described in Patent Document 2 is combined with an aqueous coating containing a resin that provides a coating film with high solvent resistance and adhesion to glass, rapid thickening and gelation may occur after mixing.

[0009] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a water-based internal anti-reflection coating material that has good workability and storage stability and is capable of forming a coating film that has excellent adhesion to glass substrates and solvent resistance.

[0010] The water-based internal antireflection coating composition of the present invention is a water-based internal antireflection coating composition for glass optical elements, comprising a dispersion containing carbon black and a hydroxyl-containing acrylic emulsion, a polyisocyanate compound, and an epoxy-group-containing compound, wherein the hydroxyl-containing acrylic emulsion has a hydroxyl value of 5 to 50 mgKOH / g in solids, the carbon black is coated with a nonionic surfactant, and the water-based internal antireflection coating composition contains 15 to 25 parts by mass of carbon black per 100 parts by mass of solids. The water-based internal antireflection coating film of the present invention is an internal antireflection coating film formed by applying the internal antireflection coating composition. The glass optical element of the present invention is a glass optical element having the internal antireflection coating film.

[0011] According to the present invention, it is possible to provide a water-based internal anti-reflection coating material that has good workability and storage stability and is capable of forming a coating film that has excellent adhesion to glass substrates and solvent resistance.

[0012] It is a figure for explaining a method for evaluating solvent resistance in an example. It is a figure for explaining a method for measuring transmittance in an example. It is a figure for explaining a method for measuring internal reflectance in an example. It is a schematic diagram showing a state observed from the side of a process of applying paint to an edge portion of a glass lens in an example.

[0013] Hereinafter, an embodiment of the present invention will be described. Hereinafter, the water-based internal reflection anti-coating material may be simply referred to as an "internal reflection anti-coating material" or "coating material." The internal reflection anti-coating film may be simply referred to as a "coating film."

[0014] Water-based internal anti-reflection paints are composed of multiple materials such as binder resins and carbon black, and their paint compositions are classified into two types: one-component paints that consist only of a base agent, and paints that consist of multiple paint components, including a base agent and a curing agent, etc. In paints that consist of multiple paint components, each paint composition is prepared, and before application, the base agent and the paint components other than the base agent are mixed to form the final paint.

[0015] For example, a paint composed of multiple paint compositions can be a paint composed of a paint composition containing a binder resin and a pigment as a base (hereinafter referred to as "Z-1 Liquid"), a curing agent (hereinafter referred to as "Z-2 Liquid"), and a silane coupling agent (hereinafter referred to as "Z-3 Liquid"). If Z-2 Liquid or Z-3 Liquid is mixed with Z-1 Liquid in advance and supplied as a single liquid, the reaction will proceed after mixing, causing an increase in viscosity and making it unusable for application. Therefore, it is necessary, and commonly done, to mix Z-2 Liquid or Z-3 Liquid with Z-1 Liquid immediately before application.

[0016] In the case of the aqueous multi-component polyurethane coating composition described in Patent Document 1, the first component (X) and the second component (Y) are mixed together immediately before application to initiate a curing reaction, and then applied to form a coating film with excellent appearance, corrosion resistance, water resistance, and hardness. For this reason, it is conceivable to use carbon black as the pigment (C) in the aqueous multi-component polyurethane coating composition described in Patent Document 1 to produce a black internal anti-reflection coating. However, according to the inventors' investigations, gelation may occur even with the first component (X) alone, which contains the hydroxyl-containing resin emulsion (A), pigment (C), and water. In this case, it is conceivable to further decompose the first component (X) and mix them immediately before application. For example, it is conceivable to separate the first component (X) into (X)-1, which contains the hydroxyl-containing resin emulsion (A) and water, and (X)-2, which contains the pigment (C) and water.

[0017] In this case, however, (X)-1 and (X)-2 must be weighed and mixed before application, and there is a risk that the desired properties will not be obtained or the paint itself will become unusable due to a mixing error, etc. Furthermore, if there is a large amount of paint composition before mixing, the manufacturing costs for containers and filling will also increase, so it is desirable not to increase the number of types of paint composition.

[0018] Furthermore, the ink composition described in Patent Document 2 is a paint in which a coating film is formed using only an acrylic-urethane copolymer emulsion resin as a binder resin, and the resulting coating film lacks sufficient solvent resistance and adhesion to glass. Furthermore, when the highly jet-black carbon black dispersion described in Patent Document 2 is combined with another binder resin to form an aqueous internal antireflection coating, the coating may experience rapid thickening and gelation after production. After extensive research, the present inventors have found that combining an emulsion-type aqueous acrylic polyol having certain characteristics with a carbon black dispersion can suppress rapid thickening and gelation. Furthermore, they have found that the above-mentioned problems in the prior art can be solved by further combining the above combination with a polyisocyanate compound and an epoxy group-containing compound to form a curable coating liquid. That is, the internal antireflection coating according to the present invention is an aqueous internal antireflection coating for glass optical elements, which contains a dispersion containing carbon black and a hydroxyl group-containing acrylic emulsion, a polyisocyanate compound, and an epoxy group-containing compound. The hydroxyl group-containing acrylic emulsion has a hydroxyl value of 5 to 50 mgKOH / g of solid content, and the carbon black is coated with a nonionic surfactant. The aqueous internal anti-reflection coating material contains 15 to 25 parts by mass of the carbon black per 100 parts by mass of solid content (105°C, 60 min).

[0019] The internal anti-reflection coating composition of the present invention contains a hydroxyl-containing acrylic emulsion having a hydroxyl value of 5 to 50 mgKOH / g of solids and carbon black coated with a nonionic surfactant. In the present invention, a hydroxyl-containing acrylic emulsion having a hydroxyl value of 5 to 50 mgKOH / g of solids is combined with a dispersion of carbon black coated with a nonionic surfactant. The inventors discovered that only this combination can maintain the stable structure of the emulsion for a long period of time. This allows for the production of a black resin dispersion that can suppress thickening and gelation without increasing the number of coating compositions, resulting in an excellent pot life. Furthermore, by combining the black resin dispersion with a polyisocyanate compound and an epoxy group-containing compound, an internal anti-reflection coating composition can be produced that can form a coating film with excellent adhesion to glass substrates and solvent resistance.

[0020] The elements constituting the internal reflection preventing coating material according to the present invention are described in detail below. <Hydroxyl-containing acrylic emulsion> The hydroxyl-containing acrylic emulsion according to the present invention is the main material forming the binder resin, and preferably contains at least a hydrophobic alkyl group-containing (meth)acrylate monomer unit and a hydroxyl-containing ethylenically unsaturated monomer unit. The hydroxyl value of the solid content of the obtained acrylic emulsion can be controlled to 5 to 50 mgKOH / g by adjusting the content of the hydroxyl-containing ethylenically unsaturated monomer unit. By ensuring that the hydroxyl value of the solid content of the acrylic emulsion is within the above range, both the curing reaction with the isocyanate curing agent during coating film formation and the stability of the black resin dispersion containing both carbon black and the hydroxyl-containing acrylic emulsion can be achieved. The hydroxyl-containing ethylenically unsaturated monomer unit may be of one type or multiple types. The hydroxyl value of the solid content of the acrylic emulsion referred to here is the mass (mg) of potassium hydroxide (KOH) equivalent to the hydroxyl groups in 1 g of sample, and can be measured in accordance with the commonly used JIS K1557-1 and JIS K1557-6.

[0021] The hydroxyl group-containing acrylic emulsion according to the present invention is preferably an emulsion polymer of a monomer mixture as shown below. Examples of hydrophobic alkyl group-containing (meth)acrylate monomers include methyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, neopentyl (meth)acrylate, isopentyl (meth)acrylate, sec-pentyl (meth)acrylate, 3-pentyl (meth)acrylate, cyclopentyl (meth)acrylate, n-hexyl (meth)acrylate, and cyclohexyl (meth)acrylate. Examples of hydroxyl group-containing ethylenically unsaturated monomers include (meth)acrylic acid, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and ε-caprolactone-modified (meth)acrylic monomers. In this specification, the term "(meth)acrylic acid" refers to a compound of acrylic acid or methacrylic acid. For example, n-butyl (meth)acrylate refers to n-butyl acrylate or n-butyl methacrylate. Similarly, the term "(meth)acrylate" refers to an acrylate compound or methacrylate compound.

[0022] There are no particular limitations on the method for producing the hydroxyl-containing acrylic emulsion, and examples thereof include the following methods. First, an acrylic resin obtained by polymerizing a polymerizable unsaturated compound component containing a (meth)acryloyl compound as an essential component and other polymerizable unsaturated compounds in one or multiple steps in the presence of an organic solvent is dispersed in water. Another example is a method of emulsion-polymerizing a polymerizable unsaturated compound component containing a (meth)acryloyl compound as an essential component and other polymerizable unsaturated compounds in one or multiple steps in the presence of water and a dispersion stabilizer. In the case of a hydroxyl-containing acrylic emulsion, an example of a method for dispersing the resin in water is to neutralize some or all of the anionic groups, such as carboxy groups, contained in the acrylic resin with a basic compound and then disperse the resulting resin in water. Alternatively, the acrylic resin can be added to an aqueous medium containing a basic compound and dispersed.

[0023] The hydroxyl-containing acrylic emulsion preferably has a 90% diameter (D90) in the volume-based cumulative distribution (hereinafter simply referred to as the 90% diameter (D90)) of 300 nm or less, more preferably 150 nm or less. When the average particle diameter of the hydroxyl-containing acrylic emulsion is within the above range, a dense coating film is obtained upon drying. This in turn enables the formation of an internal reflection prevention coating film with higher adhesion and excellent solvent resistance. The 90% diameter (D90) of the hydroxyl-containing acrylic emulsion can be measured by dynamic light scattering. Specifically, for example, it can be measured as follows using a particle size distribution analyzer (trade name: Nanotrac WAVE-EZ150, manufactured by Microtrac-Bell Corporation). The dispersion containing the hydroxyl-containing acrylic emulsion to be measured is diluted to 0.05% by mass with ion-exchange water, stirred and mixed with a stirrer for 1 minute, and then set in the analyzer to measure the particle size distribution.

[0024] <Carbon Black Dispersion> The carbon black dispersion of the present invention is a dispersion in which carbon black coated with a nonionic surfactant is dispersed in an aqueous medium. The inventors have discovered that the use of a carbon black dispersion coated with a nonionic surfactant can suppress unintended thickening, gelation, and the like when mixed with the hydroxyl-containing acrylic emulsion of the present invention. This has enabled the production of a black resin dispersion containing both carbon black and a hydroxyl-containing acrylic emulsion that is stable over a long period of time. Furthermore, the use of this black resin dispersion that is stable over a long period of time has made it possible to reduce the number of liquids mixed immediately before use, and to provide an aqueous internal anti-reflection coating material that has a long usable time and good workability. This is thought to be because the carbon black is coated with a nonionic surfactant, making it less susceptible to changes in pH and ionicity in the coating material when used in an aqueous medium.

[0025] The nonionic surfactants that can be used in the present invention are not particularly limited, but can be broadly classified into ester types (polyhydric alcohol types) having a structure in which a polyhydric alcohol such as glycerin, sorbitol, sucrose, etc., and a fatty acid are ester-bonded, ether types such as polyoxyethylene alkyl ethers and polyoxyethylene alkylphenyl ethers, ester-ether types in which ethylene oxide is added to an ester of a polyhydric alcohol such as glycerin or sorbitol, etc., and a fatty acid, and having both an ester bond and an ether bond in the molecule, and fatty acid alkanolamide types in which a hydrophobic group and a hydrophilic group are bonded by an amide bond, etc. Specific examples of these include polyoxyethylene alkyl ethers, polyoxyethylene alkylaryl ethers, polyoxyethylene derivatives, polyoxyethylene oxypropylene block copolymers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, glycerin fatty acid esters, polyoxyethylene fatty acid esters, acetylene diols, polyoxyethylene alkylamines, polyoxyethylene alkylphenyl ether-modified silicones, etc. The molecular structure of the nonionic surfactant may be either a linear single-chain structure or a comb-shaped structure having side chains. The nonionic surfactant preferably has a comb-shaped structure, as this allows for a more stable dispersion of the carbon black particles.

[0026] The carbon black that can be used in the present invention is not particularly limited, but preferably satisfies the following conditions in order to further reduce internal reflectance, an important characteristic of an internal reflection-preventing coating. Specifically, the carbon black preferably has a pH in the range of 6.0 to 8.0, a primary particle size in the range of 10 to 30 nm, and a DBP oil absorption of 100 ml / 100 g or less. When the pH of the carbon black is within the above range, the nonionic surfactant most effectively stabilizes the dispersion, allowing the dispersion to be maintained at a finer particle size. Furthermore, the smaller the primary particle size of the carbon black, the more advantageous it is for reducing internal reflectance. However, as the primary particle size of the carbon black decreases, the carbon black tends to aggregate, making it difficult to disperse the particles without leaving any coarse particles. Furthermore, when the primary particle size of the carbon black exceeds 30 nm, the internal reflectance increases. Therefore, when the primary particle size of the carbon black is within the range of 10 to 30 nm, it is easier to achieve both a uniform dispersion and high internal reflectance. The DBP oil absorption is preferably 100 ml / 100 g or less to prevent the carbon black from having a high thixotropy and a lack of fluidity, resulting in a decrease in dispersion stability, when finely dispersed. The pH of the carbon black is measured in accordance with ASTM D1512. The DBP oil absorption of the carbon black is measured in accordance with JIS K 6217-4:2001. The primary particle size of the carbon black can be determined by measuring the particle sizes of, for example, 500 or more particles in a transmission electron microscope (TEM) photograph and calculating the arithmetic average value.

[0027] The method for coating (treating) carbon black with a nonionic surfactant is not particularly limited, but an example thereof is a method in which carbon black is added to a nonionic surfactant dispersed or dissolved in water, and the mixture is mixed and stirred.

[0028] The nonionic surfactant can be neutralized with a basic compound, if necessary, to stably dissolve it in water. Examples of the basic compound include organic amines such as aliphatic amines, ethanolamine, diethanolamine, triethanolamine, N-methylethanolamine, diisopropanolamine, 2-ethyl-2-amino-1,3-propanediol, triethylamine, and aqueous ammonia.

[0029] The dispersing device used to disperse carbon black as fine particles in an aqueous medium is not particularly limited, but is preferably a wet grinding device, such as a bead mill device that uses beads made of glass, alumina, zirconia, modified zirconia, etc. Specific examples include a paint shaker, a ball mill, a visco mill, and a star mill.

[0030] The water-based internal anti-reflective coating according to the present invention contains 15 to 25 parts by mass of carbon black per 100 parts by mass of the solid content of the water-based internal anti-reflective coating from the viewpoints of glass adhesion, solvent resistance, and internal reflection performance. When the carbon black content is 15 parts by mass or more, sufficient internal anti-reflective performance can be obtained, while when the carbon black content is 25 parts by mass or less, glass adhesion and solvent resistance can be maintained at a sufficiently high level. In this specification, the "solid content of the water-based internal anti-reflective coating" refers to the solid components remaining after drying the internal anti-reflective coating at 105°C for 60 minutes. The "solid content of the water-based internal anti-reflective coating" corresponds to the portion of the components constituting the internal anti-reflective coating, excluding the components lost during the process of forming an internal anti-reflective coating film using the internal anti-reflective coating. This portion may be simply referred to as the "solid content." The detailed method for measuring the solid content in this specification is as follows. First, the mass of an aluminum cup is measured (measurement value A). Approximately 1.0 g of the measurement target (paint) is weighed onto the aluminum cup (measurement value B), and the aluminum cup is air-dried for 30 minutes. The sample is then dried in an electric furnace at 105°C for 60 minutes and then removed. The removed sample is aged for 2 hours in an environment at a temperature of 23±3°C and a relative humidity of 50±10%, and the mass of the heating residue, including the aluminum cup, is measured (measured value C). The obtained measured value is used to calculate the solid content (mass%) using the following formula: Solid content (mass%) = 100 × (measured value C - measured value A) / measured value B

[0031] An example of a method for measuring the carbon black content is a measurement method using TG-DTA. Specifically, a solid material corresponding to the solid content defined in the present invention is first prepared, and TG-DTA measurement is performed using the solid material. The measurement conditions are as follows: First, the material is heated from 40°C to 600°C in a nitrogen atmosphere, and then the heating temperature is temporarily reduced to 400°C. Next, the atmospheric gas is switched from nitrogen to air, and the heating temperature is increased to 800°C. The mass loss when heated to 600°C in a nitrogen atmosphere corresponds to the amount of organic matter, and the mass loss when heated to 800°C after switching to an air atmosphere corresponds to the carbon black content.

[0032] <Polyisocyanate Compound> The polyisocyanate compound according to the present invention is a water-dispersible polyisocyanate compound that can be dispersed without separation when added to an aqueous medium. The water-dispersible polyisocyanate compound may be modified with a hydrophilic compound having a hydrophilic group, as necessary. The hydrophilic group may be an ionic hydrophilic group or a nonionic hydrophilic group.

[0033] The polyisocyanate compound contained in the water-dispersible polyisocyanate compound is not particularly limited as long as it does not deviate from the scope of the present invention. Examples of polyisocyanate compounds include aromatic diisocyanates such as tolylene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), xylylene diisocyanate (XDI), and metaxylylene diisocyanate (MXDI); aliphatic diisocyanates such as hexamethylene diisocyanate (HDI); alicyclic polyisocyanates such as isophorone diisocyanate (IPDI); and multimers thereof such as biuret type, nurate type, and trimethylolpropane (TMP) adduct type. The polyisocyanate compound according to the present invention may be a mixture of two or more of these polyisocyanate compounds.

[0034] Preferably, the polyisocyanate compound is an aliphatic diisocyanate and / or an alicyclic polyisocyanate compound, more preferably hexamethylene diisocyanate (HDI) and / or isophorone diisocyanate (IPDI). Such polyisocyanate compounds have lower reactivity than aromatic polyisocyanate compounds, and can suppress side reactions with aqueous media such as water.

[0035] Within the scope of the present invention, the polyisocyanate chain may be modified as desired, and further, a crosslinking reaction may occur via the isocyanate groups contained in the polyisocyanate. In a polyisocyanate compound that is a trifunctional or higher polymer, at least one of the multiple isocyanate groups may be modified, and a crosslinking reaction may occur via at least two isocyanate groups.

[0036] In the internal reflection anti-coating according to the present invention, the equivalent ratio between the isocyanate groups of the water-dispersible polyisocyanate and the hydroxyl groups of the hydroxyl group-containing acrylic emulsion is defined as NCO / OH. The content of the water-dispersible polyisocyanate compound in the internal reflection anti-coating according to the present invention is preferably an amount such that the NCO / OH ratio falls within the range of 0.8 to 3.0, and more preferably falls within the range of 1.2 to 2.5. By ensuring that the equivalent ratio (NCO / OH) falls within the above range, the curing reactivity of the aqueous coating composition can be ensured within a favorable range. Note that the above equivalent ratios are all molar ratios in the solid content.

[0037] <Epoxy Group-Containing Compound> The epoxy group-containing compound in the present invention is a compound having an epoxy group. As the compound having an epoxy group, an epoxy group-containing silane compound can be preferably used from the viewpoints of adhesion to glass, corrosion resistance, and coating hardness. Specific examples of the epoxy group-containing silane compound include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane. As the epoxy group-containing silane compound, an epoxy group-containing alkoxysilane compound can be particularly preferably used from the viewpoints of corrosion resistance and coating hardness. As the alkoxy group of the epoxy group-containing alkoxysilane compound, a trimethoxy group is preferred from the viewpoint of corrosion resistance. The solids content of the epoxy group-containing compound contained in the internal reflection anti-coating according to the present invention is preferably within the range of 5 to 15 mass %, particularly 8 to 12 mass %, based on the total solids content of the hydroxyl group-containing acrylic emulsion and the water-dispersible polyisocyanate compound. By ensuring that the solids content of the epoxy group-containing compound contained in the internal reflection anti-coating according to the present invention is within the above range, the coating workability of the coating can be improved, and a coating film excellent in glass adhesion and solvent resistance can be formed.

[0038] <Other Additives> The internal reflection anti-coating according to the present invention may contain other additives as needed, as long as the internal reflection anti-coating maintains its internal reflection performance. Examples of other additives that may be contained in the coating include defoamers, film-forming aids, thickeners, leveling agents, preservatives, and mildew-proofing agents. Because the internal reflection anti-coating according to the present invention is a water-based coating containing a surfactant, it may generate bubbles during stirring or application, compared to solvent-based coatings. Furthermore, as will be explained using FIG. 4 in the examples below, bubbles are particularly likely to occur when the internal reflection anti-coating according to the present invention is applied to a stepped lens edge surface, etc., while rotating an optical lens. Therefore, to break down generated bubbles and achieve a smooth coated surface, the internal reflection anti-coating according to the present invention preferably contains a defoamer. Examples of defoamers include mineral oil-based, silicone-based, polyether-based, and mixtures thereof. While not particularly limited, silicone-based or polyether-based agents are preferred from the viewpoint of achieving both defoaming and film-forming properties. The content of the antifoaming agent is preferably in the range of 0.1 to 1.0 mass %, particularly 0.2 to 0.5 mass %, based on the total amount of the aqueous internal reflection anti-coating at the time of application. In addition to the nonionic surfactant, an aqueous solvent can be added to the internal reflection anti-coating according to the present invention to enhance wettability.Examples of aqueous solvents include alcohols such as methyl alcohol, ethyl alcohol, n-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, n-propyl alcohol, and isopropyl alcohol; amides such as dimethylformaldehyde and dimethylacetamide; ketones such as acetone, methyl ethyl ketone, and isobutyl ketone; ethers such as tetrahydrofuran, dioxane, ethylene glycol methyl ether, ethylene glycol ethyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, triethylene glycol monomethyl ether, and triethylene glycol monoethyl ether; and polyols such as ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, diethylene glycol, polyethylene glycol, polypropylene glycol, and glycerin. Among these aqueous solvents, alcohols, glycols, and ketones are preferred, and these can be used alone or in combination of two or more. The internal anti-reflection coating according to the present invention may also contain an organic solvent, if necessary. Examples of organic solvents include butyl acetate, xylene, toluene, methyl isobutyl ketone, propylene glycol, dipropylene glycol dimethyl ether, methyl ether acetate, tetrahydrofuran, ethanol, methanol, propanol, isopropanol, 2-butanol, t-butyl alcohol, dioxane, methyl ethyl ketone, ethylene glycol, ethylene glycol monobutyl ether, ethylene glycol monobutyl ether acetate (butyl cellosolve acetate), propylene glycol monomethyl ether acetate, 2-methoxypropanol, 2-butoxypropanol, diethylene glycol monobutyl ether, butyl diglycol, N-methylpyrrolidone, ethylene carbonate, and propylene carbonate. These organic solvents may be the same organic solvents used in the preparation of hydroxyl group-containing acrylic emulsions, water-dispersible polyisocyanate compounds, etc., or may be organic solvents added separately in the preparation of the aqueous coating composition.These additives may be used singly or in combination depending on the storage environment and application method.

[0039] <Aqueous Medium> In the present invention, the aqueous medium refers to a medium containing water, such as ion-exchanged water, pure water, purified water, or distilled water, as its main component. The aqueous medium may contain a water-soluble or water-miscible organic solvent, such as an alcohol solvent, an ester solvent, a ketone solvent, an amine solvent, or an amide solvent, as necessary. Furthermore, a mixture of multiple aqueous media may be used to control the drying speed after application of the internal anti-reflection coating. The aqueous internal anti-reflection coating according to the present invention preferably contains a solvent having a boiling point of 180°C or higher and 200°C or lower (hereinafter also referred to as a high-boiling-point solvent) as the aqueous medium. By containing a high-boiling-point solvent in the aqueous medium, leveling time can be ensured, and a smooth coating film can be obtained, even if bubbles present after application are broken. If the boiling point of the high-boiling-point solvent is 180°C or higher, the high-boiling-point solvent gradually volatilizes, thereby ensuring an appropriate leveling time. If the boiling point is 200°C or lower, there is no risk that the high-boiling-point solvent will not be removed from the coating film when curing the coating film. The content of the high-boiling-point solvent in the coating is preferably 1.0% by mass or more and 5.0% by mass or less based on the total weight of the water-based internal anti-reflection coating composition of the present invention. If the content of the high-boiling-point solvent is 1.0% by mass or more based on the total weight of the coating composition, the leveling time can be ensured. If the content is 5.0% by mass or less, there is no risk of the high-boiling-point solvent being unable to be removed from the coating film during curing. Specific examples of usable high-boiling-point solvents (boiling points indicated in parentheses) include glycol-based ether solvents such as dipropylene glycol monomethyl ether (188°C), diethylene glycol diethyl ether (188°C), and diethylene glycol monomethyl ether (194°C), as well as other solvents such as propylene glycol (187°C). These solvents may be used alone or in combination of two or more. The proportion of the aqueous medium in the coating composition (dilution ratio) can be adjusted as desired depending on the application. For example, the dilution ratio can be adjusted appropriately depending on the application method, such as spraying, dipping, dispenser application, or brush application, or when controlling the coating film thickness depending on the application. The dilution rate may be changed as needed to adjust the viscosity of the paint to a desired level.

[0040] <Viscosity> The viscosity of the internal anti-reflection coating material according to the present invention may be adjusted as needed depending on the desired film thickness or to prevent dripping after application, but is preferably 20 mPa·s or more and 1,000 mPa·s or less. If the viscosity of the internal anti-reflection coating material is 20 mPa·s or more, dripping can be suppressed, making it easier to control the film thickness. If the viscosity of the internal anti-reflection coating material is 1,000 mPa·s or less, film thickness variations and bubbling can be suppressed. Here, viscosity refers to the viscosity measured using a Brookfield viscometer at a temperature of 23±1°C. Furthermore, as will be explained using FIG. 4 in the examples described later, when the internal anti-reflection coating material according to the present invention is applied to a stepped lens edge surface or the like using a sponge while rotating an optical lens, bubbling is particularly likely to occur. In such cases, adjusting the viscosity of the internal anti-reflection coating material to 20 mPa·s or more and 40 mPa·s or less by appropriately adding a solvent such as water makes it possible to obtain a uniform coating material with reduced bubbling.

[0041] <Method for producing internal anti-reflection coating> The internal anti-reflection coating according to the present invention can be produced by mixing a dispersion containing carbon black and a hydroxyl group-containing acrylic emulsion, a polyisocyanate compound, an epoxy group-containing compound, and other additional materials. Mixing can be carried out by a known method. Specifically, mixing can be carried out using, for example, a magnetic stirrer, a propeller mixer, a ball mill, a paint shaker, a basket mill, a circulating bead mill (screw type, stirring tank type, flow pipe type, annular type disperser), or the like.

[0042] [Internal Anti-Reflection Coating Film] The internal anti-reflection coating film according to the present invention is a coating film formed using the internal anti-reflection paint according to the present invention described above. That is, the internal anti-reflection coating film according to the present invention contains a cured reaction product of a hydroxyl group-containing acrylic emulsion, a water-dispersible polyisocyanate compound, and an epoxy group-containing compound, and carbon black. The thickness of the internal anti-reflection coating film is preferably 2.0 μm or more and 100 μm or less. When the thickness of the internal anti-reflection coating film is 2.0 μm or more, it can effectively absorb light that enters from the side of the substrate opposite to the surface coated with the paint and then passes through the substrate, thereby achieving a high effect of suppressing internal reflection and blocking light. Furthermore, when the thickness of the internal anti-reflection coating film is 100 μm or less, it is possible to suppress variation in film thickness when the internal anti-reflection paint is formed.

[0043] <Method for Producing an Internal Antireflection Coating Film> The internal antireflection coating film according to the present invention can be produced by applying the internal antireflection coating material according to the present invention described above to a substrate, followed by drying and curing. Known substrates, such as glass and resin, can be used as the substrate on which the coating film is formed. The coating film formation method is not particularly limited, and any known coating method may be used. Examples of application methods include spraying, dispensers, brushes, rollers, roll coating, applicators, wire bars (bar coaters), dip coating, and sponge coating. When applying an internal antireflection coating material to the periphery of an optical element, application is performed using a sponge, since masking of the lens surface is unnecessary. When using a sponge, any material, porosity, and pore size can be used. Among these, polyvinyl alcohol (PVA)-based or urethane-based materials are preferred to suppress bubble generation during application, and a porosity of 80% to 90% and a pore size of 40 μm to 100 μm are preferred. Furthermore, a sponge with an Asker F hardness of 60° to 70° is particularly preferred. The porosity can be measured by the Archimedes method. The pore diameter can be measured by observing an arbitrary cross section under a microscope, measuring the major and minor axes of the pores, averaging the measured lengths, and measuring the pore diameters of 30 pores in the same manner to calculate the average.

[0044] Furthermore, the method for drying and curing the coating liquid after application may be any method that volatilizes the aqueous medium and then fuses and reacts the dispersed particles of the resin used with each other, and any known drying and curing method may be selected according to the intended use and the required drying and curing speed. Known drying and curing methods include, for example, heating using an electric furnace, hot air, far infrared rays, etc. The drying and curing temperature is not particularly limited, but a temperature of 80°C to 120°C is preferred because it is unlikely that the dispersion state of the black pigment, etc. in the coating material will change during drying and curing, and the drying and curing time will not be long.

[0045] [Glass Optical Element] The glass optical element according to the present invention has the above-described internal antireflection coating film according to the present invention. Specifically, for example, the glass optical element may have the internal antireflection coating film according to the present invention formed on a surface of a lens through which light does not pass (called a side surface or edge surface of the lens).

[0046] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. Table 1 shows the types of substrates used as targets for coating with the internal anti-reflection coating material.

[0047] <Preparation of Carbon Black Dispersion> (Production Example 1) 6.8 parts by mass of SOLSPERSE 27000 (manufactured by Lubrizol Japan Corporation, nonionic adsorption group, single structure, active ingredient 100%) as a pigment dispersant was dissolved in 68.2 parts by mass of ion-exchanged water. To this was added carbon black (Tokai Carbon Co., Ltd., Toka Black #7550SB, average primary particle diameter 21 nm, specific surface area 135 m). ２ 25.0 parts by mass of a carbon black dispersion (25.0 parts by mass of carbon black powder (100%), 100% ethanol / g (BET method), DBP oil absorption 53 ml / 100 g, pH 7.5) was mixed to obtain a dispersion mill base. This was pre-stirred for 1 hour using a stirrer (100 rpm). The mixture was then dispersed using a circulating bead mill (Ultraviscomill UVM-2, manufactured by Imex Co., Ltd.) filled to 70% with glass beads (GB200M, manufactured by Potters Ballotini Co., Ltd., median particle size 850-600 μm) at a peripheral speed of 8 m / sec and a residence time of 60 minutes. The resulting dispersion was filtered through a 120-mesh screen to obtain carbon black dispersion (CB-1).

[0048] (Production Example 2) 13.5 parts by mass of SOLSPERSE 43000 (manufactured by Lubrizol Japan, nonionic adsorption group, comb-type structure, 50% active ingredient) as a pigment dispersant was dissolved in 61.5 parts by mass of ion-exchanged water. To this was added carbon black (Tokai Carbon Co., Ltd., Toka Black #7550SB, average primary particle diameter 21 nm, specific surface area 135 m). ２ 25.0 parts by mass of carbon black dispersion (CB-2) was prepared in the same manner as in Production Example 1, except for the above.

[0049] (Production Example 3) 6.8 parts by mass of SOLSPERSE 45000 (manufactured by Lubrizol Japan Corporation, adsorptive group anion, single structure, active ingredient 100%) as a pigment dispersant was dissolved in 68.2 parts by mass of ion-exchanged water. Except for this, the same preparation as in Production Example 1 was carried out to obtain a carbon black dispersion (CB-3).

[0050] (Production Example 4) 6.8 parts by mass of SOLSPERSE 20000 (manufactured by Lubrizol Japan Corporation, adsorptive group cation, single structure, active ingredient 100%) as a pigment dispersant was dissolved in 68.2 parts by mass of ion-exchanged water. Except for this, the procedure was the same as in Production Example 1 to obtain a carbon black dispersion (CB-4). The formulation of the carbon black dispersion and the characteristics of the dispersant used in each Production Example are shown in Table 1.

[0051]

[0052] <Preparation of Internal Antireflection Coating> The materials were mixed in the ratios shown in Tables 2 to 5 to obtain internal antireflection coatings according to Examples 1 to 25 and Comparative Examples 1 to 7.

[0053]

[0054]

[0055]

[0056]

[0057] Example 1 The following materials were prepared. Hydroxyl-containing acrylic emulsion (DIC Corporation, Burnock WE-304, hydroxyl value 43 mg KOH / g, 90% diameter (D90) 146 nm, solids content 45.2%, main components: polymer of methyl methacrylate, butyl methacrylate, and methacrylic acid): 34.3 parts by mass; Carbon black dispersion (CB-1): 32.0 parts by mass; Ion-exchanged water: 19.3 parts by mass. These were mixed and stirred for 10 minutes with a propeller stirrer to obtain a black resin dispersion containing carbon black and hydroxyl-containing acrylic emulsion. A portion of the black resin dispersion was also taken and stored in a 20°C environment for 30 days. Next, the following materials were prepared. Water-dispersible polyisocyanate compound (DIC Corporation, Burnock DNW-6000, NCO value 16.0%, solids content 100%): 10.4 parts by mass Epoxy group-containing compound (Shin-Etsu Chemical Co., Ltd., KBM-403): 4.0 parts by mass These were stirred and mixed for 10 minutes with a propeller stirrer to obtain a curing agent mixture. Next, 14.4 parts by mass of the curing agent mixture was added to 85.6 parts by mass of the black resin dispersion, and the mixture was further stirred and mixed for 10 minutes with a propeller stirrer. Finally, the mixture was filtered through a nylon mesh (#120) to obtain an internal anti-reflection coating material with a solids content of 40.0% by mass. The carbon black content per 100 parts by mass of the solids content of the coating material (105°C, 60 min) was 20.0 parts by mass. The viscosity of the paint during application was measured using a TVB-15 viscometer (manufactured by Toki Sangyo Co., Ltd.) fitted with a THM-type small sample adapter, a THM-11 rotor, measurement range M, 30 rpm, and a temperature of 23±1°C. The measured values ​​are shown in Table 2.

[0058] Examples 2 to 25 Internal anti-reflection coatings according to Examples 2 to 25 were prepared in the same manner as in Example 1, except that the materials were mixed in the ratios shown in Tables 2 to 4. The carbon black content per 100 parts by mass of the solids content of the coating (105°C, 60 min) was as shown in Tables 6 to 8. The defoaming agent used in Examples 7 to 13 was Olfine SPC (polyether-based, manufactured by Nissin Chemical Industry Co., Ltd.). The defoaming agent used in Examples 14 to 18 was BYK-028 (silicone-based, manufactured by BYK Japan KK). The defoaming agent used in Examples 19 to 25 was SN Deformer 180 (polyether-based, manufactured by San Nopco Ltd.). The high-boiling point solvent used in Examples 7 to 25 was dipropylene glycol monomethyl ether (isomer mixture) (manufactured by Tokyo Chemical Industry Co., Ltd.).

[0059] Comparative Example 1 An internal reflection-preventing coating material according to Comparative Example 1 was prepared in the same manner as in Example 1, except that the materials were mixed in the ratios shown in Table 5. The carbon black content per 100 parts by mass of the solid content of the coating material (105°C, 60 min) was 10.0 parts by mass.

[0060] Comparative Example 2 An internal reflection-preventing coating material according to Comparative Example 2 was prepared in the same manner as in Example 1, except that the materials were mixed in the ratios shown in Table 5. The carbon black content per 100 parts by mass of the solid content of the coating material (105°C, 60 min) was 30.0 parts by mass.

[0061] Comparative Example 3 Burnock WE-300 (manufactured by DIC Corporation, hydroxyl value 80 mgKOH / g, 90% diameter (D90) 169 nm, solids content 44.7%, main components: polymers of methyl methacrylate, butyl acrylate, 2-hydroxyethyl methacrylate, 4-hydroxybutyl acrylate, butyl methacrylate, and methacrylic acid) was used as the hydroxyl group-containing acrylic emulsion. An internal anti-reflection coating material according to Comparative Example 3 was prepared in the same manner as in Example 1, except that the materials were mixed in the ratios shown in Table 5. The carbon black content per 100 parts by mass of the solids content of the coating material (105°C, 60 min) was 20.0 parts by mass.

[0062] (Comparative Example 4) Burnock WE-306 (manufactured by DIC Corporation, hydroxyl value 100 mgKOH / g, 90% diameter (D90) 202 nm, solid content 45.0%, main component: polymer of styrene, methyl methacrylate, butyl acrylate, and 2-hydroxyethyl methacrylate) was used as the hydroxyl group-containing acrylic emulsion. An internal anti-reflection coating material according to Comparative Example 4 was prepared in the same manner as in Example 1, except that the materials were mixed in the ratios shown in Table 5. The carbon black content per 100 parts by mass of the solid content of the coating material (105°C, 60 min) was 20.0 parts by mass.

[0063] (Comparative Example 5) (CB-3) was used as the carbon black dispersion. An internal reflection preventing coating material according to Comparative Example 5 was prepared in the same manner as in Example 1, except that the materials were mixed in the ratios shown in Table 5. The carbon black content per 100 parts by mass of the solid content of the coating material (105°C, 60 min) was 20.0 parts by mass.

[0064] (Comparative Example 6) (CB-4) was used as the carbon black dispersion. An internal reflection preventing coating material according to Comparative Example 5 was prepared in the same manner as in Example 1, except that the materials were mixed in the ratios shown in Table 5. The carbon black content per 100 parts by mass of the solid content of the coating material (105°C, 60 min) was 20.0 parts by mass.

[0065] (Comparative Example 7) Urethane-acrylic emulsion ceranate WHW-822 (manufactured by DIC Corporation, 90% diameter (D90) 81 nm, solid content 35.0%) was used as the binder resin. An internal anti-reflection coating material according to Comparative Example 7 was prepared in the same manner as in Example 1, except that the materials were mixed in the ratios shown in Table 5. The carbon black content per 100 parts by mass of the solid content of the coating material (105°C, 60 min) was 20.0 parts by mass.

[0066] <Preparation of Internal Antireflection Coating Films A-1 and A-2> A glass slide (product name: Frosted Slide Glass, Water-Edged Polished, S2215, manufactured by Matsunami Glass Industry Co., Ltd.) was prepared as a substrate. The internal antireflection coating material obtained above was applied to a glass slide whose surface had been previously cleaned with acetone using a wire bar (wet film thickness 12 μm), and air-dried for 5 minutes. This was then dried and cured at 105°C for 60 minutes to prepare internal antireflection coating film A-1. In addition, an internal antireflection coating material prepared using a black resin dispersion that had been stored in a 20°C environment for 30 days was similarly applied, dried, and cured to prepare internal antireflection coating film A-2.

[0067] <Preparation of Internal Antireflection Coating Films B-1 and B-2> A glass prism (trade name: right-angled triangular prism LaSF03, 30 × 30 mm, t 15 mm, apex angle 90 °, refractive index 1.8, manufactured by Canon Optron Inc.) was prepared as a substrate. First, all surfaces of the glass prism were polished to a mirror finish using #2000 waterproof sandpaper, and then the surface was washed with acetone. Next, the glass prism was held using a jig with the bottom surface (hypothetic surface) of the glass prism facing up and horizontal, and the internal antireflection coating material obtained above was applied to the bottom surface of the glass prism using a wire bar (wet film thickness 12 μm). Thereafter, the internal antireflection coating film B-1 was prepared by drying and curing at 105 ° C. for 60 minutes. In addition, an internal antireflection coating material prepared using a black resin dispersion liquid stored in a 20 ° C. environment for 30 days was similarly applied, dried, and cured to prepare an internal antireflection coating film B-2.

[0068] <Preparation of Internal Antireflection Coatings C-1 and C-2> A glass slide (product name: Frosted Glass Slide, Water-Edged Polished, S2215, manufactured by Matsunami Glass Industry Co., Ltd.) was prepared as a substrate. The internal antireflection coating obtained by the preparation of the internal antireflection coating described above was applied to a glass slide whose surface had been previously cleaned with acetone using a wire bar (wet film thickness 5 μm), and air-dried for 5 minutes. The coating was then dried and cured at 105°C for 60 minutes to prepare internal antireflection coating film C-1. Similarly, an internal antireflection coating prepared using a black resin dispersion that had been stored in a 20°C environment for 30 days was similarly applied, dried, and cured to prepare internal antireflection coating film C-2.

[0069] <Evaluation> The internal anti-reflection paints and internal anti-reflection coating films A-1, A-2, B-1, B-2, and C-1, C-2 prepared in each of the Examples and Comparative Examples were evaluated as follows. The breakdown of the solid content (ratio of each component on a mass basis) of the internal anti-reflection coating film of each Example and Comparative Example and the results of each evaluation are shown in Tables 6 to 9. In Table 9, N.D. indicates that the paint gelled and therefore each measurement and evaluation could not be performed.

[0070] [Coating Adhesion] The adhesion between the internal reflection antireflection coating film and the substrate was evaluated using internal reflection antireflection coating films A-1 and A-2 based on the cross-cut method (JIS K 5600-5-6:1999) as follows. A: Cross-cut evaluation: "Class: 0" or "Class: 1". B: Cross-cut evaluation: "Class: 2" or "Class: 3". C: Cross-cut evaluation: "Class: 4" or "Class: 5". The evaluation results are shown in Tables 6 to 9.

[0071] [Solvent Resistance] Slide glasses on which the internal anti-reflection coating films A-1 and A-2 were formed were used as test pieces. Also, cleaning paper (Dasper K-3, manufactured by Ozu Sangyo Co., Ltd.) folded to a size of approximately 1.5 cm square was soaked in a solution of 0.22 g of a 1:1 mixture of diethyl ether and methanol. The cleaning paper soaked in the solution was used to measure the solvent resistance at a rate of approximately 300 g / cm. ２The surfaces of the internal antireflection coating films A-1 and A-2 were rubbed 30 times (back and forth) with a force of 1000 psi. The test specimens and cleaning paper after the test were observed and compared with the test specimen 30 and cleaning paper 31 shown in Figures 1(a) to 1(c), which serve as the evaluation criteria, and evaluated as follows. Figure 1(a) shows the test specimen 30 and cleaning paper 31 corresponding to evaluation A, "no discoloration," and Figure 1(b) shows the test specimen 30 and cleaning paper 31 corresponding to evaluation B, "slight discoloration, but at a level that is not problematic for practical use." Figure 1(c) is a diagram showing the test specimen 30 and cleaning paper 31 corresponding to evaluation C, "severe discoloration or film peeling." A: No discoloration. B: Slight discoloration, but at a level that is not problematic for practical use. C: Severe discoloration or film peeling occurred. The evaluation results are shown in Tables 6 to 9.

[0072] [Transmittance] As shown in FIG. 2, a slide glass 23 provided with an internal anti-reflection coating film 22 (C-1, C-2) was used as a test piece 20, and the total diffuse transmittance was measured using a spectrophotometer (manufactured by JASCO Corporation, V-670) equipped with an ILN-725 type 150 mmφ integrating sphere unit. In the measurement, as shown in FIG. 2, incident light 21 in the visible light region (wavelength 400 nm to 700 nm) was incident on the test piece 20 from a perpendicular direction while changing the conditions in 1 nm increments, and the transmitted light 24 was measured, and the average value of the total diffuse transmittance was calculated. The obtained measurement results were evaluated as follows. A: Total diffuse transmittance is 0.1% or less. B: Total diffuse transmittance is greater than 0.1% and less than 1.0%. C: Total diffuse transmittance is greater than 1.0%. The evaluation results are shown in Tables 6 to 9.

[0073] [Internal Reflectance] [Method for Measuring Internal Reflectance] Internal reflectance was measured using the internal anti-reflection coating film B. As shown in Figure 3, a glass prism 10 provided with an internal anti-reflection coating film 3 was placed in the sample mounting section of a spectrophotometer. Light emitted from a light source 11 was passed through a polarizing plate 17 set to N-polarization and collected by a slit 18 (a rectangular aperture measuring 1 mm long x 3 mm wide) to obtain incident light 12. Upon entering the glass prism 10, the incident light 12 was refracted and incident on the internal anti-reflection coating film 3 at an incident angle θ, where it was further reflected and emitted as internally reflected light 13. The internally reflected light 13 was received by a φ60 mm integrating sphere 14 equipped with a photodetector, and the light intensity at each wavelength was measured. The distance A from the plumb line (perpendicular) 15 to the base of the glass prism 10 to the tangent surface 16 of the integrating sphere entrance was 15√√2 mm, and the aperture diameter B of the integrating sphere 14 was φ15 mm. Without the glass prism 10 installed, the internal reflection intensity of light with wavelengths of 400 nm to 1500 nm was measured at 5 nm intervals, and the light intensity at each wavelength was defined as 100% internal reflectance. Then, with the glass prism 10 provided with the internal reflection anti-coating film 3 installed, the internal reflection intensity of light with wavelengths of 400 nm to 700 nm was measured at 5 nm intervals, and the percentage of the internal reflection intensity at each wavelength relative to the internal reflection intensity when the glass prism 10 was not installed was calculated. The arithmetic mean of the percentages obtained at each wavelength was then taken as the internal reflectance of the sample. The internal reflectance in the visible light region (400 nm to 700 nm) obtained above was evaluated for internal reflection prevention performance according to the following criteria: A: Internal reflectance is 38.0% or less; B: Internal reflectance is greater than 38.0% and less than 43.0%; C: Internal reflectance is greater than 43.0%. The evaluation results are shown in Tables 6 to 9.

[0074] [Storage Stability of Black Resin Dispersion] The storage stability of the black resin dispersion was evaluated by comparing the evaluation results of the internal antireflection coating films A-1, A-2, B-1, B-2, and C-1 and C-2 prepared above, and evaluating them according to the following criteria. A: No difference in the evaluation results was observed when A-1 and A-2, B-1 and B-2, and C-1 and C-2 were compared, respectively. B: There was a difference in the evaluation results when A-1 and A-2, B-1 and B-2, and C-1 and C-2 were compared, respectively, but no "C" was observed in any of the evaluations. C: A-2, B-2, and C-2 were evaluated as "C" or "N.D." The evaluation results are shown in Tables 6 to 9. [Defoaming Property When Applying the Coating to a Glass Lens] Figure 4 is a schematic diagram showing the side view of the process of applying the internal antireflection coatings prepared in each Example and Comparative Example to the edge of a glass lens. As shown in FIG. 4 , a 60 mm diameter glass lens 41 was placed on a lens support 46 on a turntable 45. The turntable 45 was rotated to rotate the glass lens 41 at 50 rpm, while coating the stepped, polished edge 42 of the glass lens 41. During coating, a sponge 43 cut to a size of 12 mm length x 8 mm width x 5 mm thickness was impregnated with an appropriate amount of coating material, and the sponge 43, supported by tweezers 44, was placed along the grain of the glass lens. The sponge used was Ruby Cell (U4C1, Asker F hardness 65, pore size 70 μm, porosity 85%) manufactured by Toyo Polymer Co., Ltd. The foam generation during the coating process shown in FIG. 4 was monitored, and the defoaming ability was evaluated according to the following criteria: A: No foam generation, or completely disappears after a short time; B: Slight foam generation, but at a level that is not problematic for practical use; C: Excessive foam generation, making practical use difficult. The evaluation results are shown in Tables 6 to 9.

[0075] [Overall Evaluation] The overall evaluation was performed using the evaluation results of adhesion, solvent resistance, transmittance, internal reflectance, and storage stability of the black resin dispersion liquid according to the following criteria. A: All evaluation results were "A". B: At least one evaluation result was "B" and no evaluation result was "C". C: At least one evaluation result was "C". The evaluation results are shown in Tables 6 to 9.

[0076]

[0077]

[0078]

[0079]

[0080] The present invention is not limited to the above-described embodiments, and various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the following claims are appended to apprise the public of the scope of the present invention.

[0081] This application claims priority based on Japanese Patent Application No. 2024-112567, filed July 12, 2024, the entire contents of which are incorporated herein by reference.

[0082] 3. Internal anti-reflection coating 10. Glass prism 11. Light source 12. Incident light 13. Internally reflected light 14. Integrating sphere 15. Plumb line (perpendicular) to the base of the right-angled triangular prism 16. Contact surface of the integrating sphere entrance 17. Polarizing plate 18. Slit 20. Test piece for measuring transmittance 21. Incident light 22. Coating 23. Slide glass 24. Transmitted light 30. Test piece after solvent resistance test 31. Cleaning paper after solvent resistance test 41. Glass lens 42. Edge 43. Sponge

Claims

1. A water-based internal anti-reflection coating for glass optical elements, comprising: a dispersion containing carbon black and a hydroxyl group-containing acrylic emulsion; a polyisocyanate compound; and an epoxy group-containing compound, wherein the hydroxyl group-containing acrylic emulsion has a hydroxyl value of 5 to 50 mgKOH / g in the solids; the carbon black is coated with a nonionic surfactant; and the water-based internal anti-reflection coating contains 15 to 25 parts by mass of the carbon black per 100 parts by mass of the solids.

2. The water-based internal anti-reflection coating according to claim 1, wherein the hydroxyl-containing acrylic emulsion has a 90% diameter (D90) in a volume-based cumulative distribution of 150 nm or less.

3. A water-based internal anti-reflective coating according to claim 1 or 2, having a viscosity of 20 mPa·s or more and 40 mPa·s or less, containing at least one of a polyether-based anti-foaming agent and a silicone-based anti-foaming agent in a proportion of 0.1 mass% or more and 1.0 mass% or less relative to the water-based internal anti-reflective coating, and containing, as the aqueous medium, a solvent having a boiling point of 180°C or more and 200°C or less in an amount of 1.0 mass% or more and 5.0 mass% or less relative to the entire water-based internal anti-reflective coating.

4. The water-based internal anti-reflection coating material according to any one of claims 1 to 3, wherein the nonionic surfactant has a comb structure.

5. An internal anti-reflection coating film obtained by applying the water-based internal anti-reflection coating material according to any one of claims 1 to 4.

6. A glass optical element having the internal antireflection coating film according to claim 5.

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