Inner surface antireflection coating material, inner surface antireflection coating film, and optical element

Abstract

To provide an inner surface antireflection coating material that has low impact on the environment, has excellent film-forming properties on base materials made of a resin, and can form an inner surface antireflection coating film excellent in adhesion to the base material and optical characteristics.　Provided is an inner surface antireflection coating material that contains a binder resin, a black pigment, an additive, and an aqueous medium, wherein the binder resin contains an acid-modified polyolefin resin and a polyurethane resin, the acid-modified polyolefin resin contains a propylene component and an ethylene component in a specific mass ratio, the content of the acid-modified polyolefin resin in the inner surface antireflection coating material is 60 mass% or more when the heating residue of the inner surface antireflection coating material at 105°C is taken to be 100 mass%, the black pigment is carbon black having a particle size (D90) of 200 nm or less, the carbon black is coated with a nonionic surfactant, and the additive is a urethane associative thickener.

Description

Inner surface anti-reflection paint, inner surface anti-reflection coating film, and optical element

[0001] The present invention relates to an internal antireflection coating material, an internal antireflection coating film formed using the internal antireflection coating material, and an 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] In recent years, with the widespread use of resin lenses and the like, there has been a demand for internal anti-reflection coatings that can be suitably applied to optical elements made of resin as well as glass.

[0004] Patent Document 1 proposes a light-shielding coating material for forming a light-shielding film on a resin lens made of a cycloolefin polymer as a light-shielding coating material for a resin lens for an optical element.

[0005] Patent Document 2 proposes a water-based coating agent containing an acid-modified polyolefin resin that can form a coating film that has good adhesion to and chemical resistance with cyclic polyolefin materials without requiring special surface treatment of the materials.

[0006] JP 2013-250440 A JP 2014-237813 A

[0007] The light-shielding coating material described in Patent Document 1 uses an organic solvent as a medium. However, in recent years, with growing concern about the environment, there has been an increasing demand for environmentally friendly internal anti-reflection coating materials that use less volatile organic compounds (VOCs) in the coating material. Therefore, the light-shielding coating material described in Patent Document 1 has room for improvement in terms of its impact on the environment.

[0008] To reduce VOC emissions into the environment, it is conceivable to use an aqueous medium rather than an organic solvent as the paint medium. Patent Document 2 proposes a water-based coating agent with good adhesion to resin materials. It is conceivable to disperse a black pigment, dye, or the like in the water-based coating agent disclosed in Patent Document 2 to create an environmentally friendly internal reflection prevention coating. However, according to the inventors' investigations, when a black pigment, dye, or the like is dispersed in a water-based coating agent containing an acid-modified polyolefin resin, such as that disclosed in Patent Document 2, to create an internal reflection prevention coating, the film-forming properties and adhesion of the formed coating film to the substrate may be reduced. Furthermore, the formation of aggregates in the coating may cause unintended thickening or gelation, leading to localization of the black pigment or dye in the coating film and the formation of an uneven coating film, which may result in reduced optical properties of the coating film.

[0009] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an internal antireflection coating material that has little impact on the environment, has excellent film-forming properties on substrates made of resin, and is capable of forming an internal antireflection coating film that has excellent adhesion to the substrate and excellent optical properties.

[0010] The internal reflection-preventing coating according to the present invention is an internal reflection-preventing coating containing a binder resin, a black pigment, a thickener, and an aqueous medium, wherein the binder resin contains an acid-modified polyolefin resin and a polyurethane resin, the acid-modified polyolefin resin is composed of a propylene component and an ethylene component, the mass ratio of the propylene component to the ethylene component in the acid-modified polyolefin resin being in the range of propylene component:ethylene component = 10:90 to 60:40, and when the heating residue of the internal reflection-preventing coating at 105°C is taken as 100 mass%, the content of the acid-modified polyolefin resin in the internal reflection-preventing coating is 60 mass% or more, the black pigment is carbon black having a particle size (D90) of 200 nm or less in a volume-based particle size distribution, the carbon black is coated with a nonionic surfactant, and the thickener is a urethane associative thickener.

[0011] The internal reflection anti-coating film according to the present invention is an internal reflection anti-coating film obtained by applying the internal reflection anti-coating material described above. Furthermore, the optical element according to the present invention has the internal reflection anti-coating film described above.

[0012] According to the present invention, it is possible to provide an internal antireflection coating material that has little impact on the environment, has excellent film-forming properties on substrates made of resin, and is capable of forming an internal antireflection coating film that has excellent adhesion to the substrate and excellent optical properties.

[0013] FIG. 2 is a diagram for explaining a method for measuring internal reflectance in the examples.

[0014] DETAILED DESCRIPTION OF THE INVENTION Hereinafter, the internal reflection preventing paint may be simply referred to as a "paint" and the internal reflection preventing coating film may be simply referred to as a "coating film."

[0015] In the present invention, the "heating residue of the internal reflection anti-coating at 105°C" refers to the solid components remaining after the internal reflection anti-coating is dried at 105°C. The "heating residue of the internal reflection anti-coating at 105°C" corresponds to the portion of the components constituting the internal reflection anti-coating excluding the components that are lost in the process of forming an internal reflection anti-coating film using the internal reflection anti-coating. This portion may be simply referred to as the "solid content."

[0016] Conventionally, paints prepared by dispersing and dissolving each component in an organic solvent have been widely used. However, in recent years, growing environmental concerns have led to a demand for paints in which each component is dispersed and dissolved in an aqueous medium instead of an organic solvent. However, paints prepared by dispersing and dissolving each component in an aqueous medium generally have the problem of difficulty in achieving both film-forming properties and adhesion of the formed coating film on substrates made of resins, particularly low-polarity resins. Patent Document 2 describes a water-based coating agent capable of forming a coating film with excellent adhesion and chemical resistance on the surface of a material made of low-polarity cyclic polyolefin. Therefore, it is conceivable to produce an internal reflection prevention coating by mixing the water-based coating agent described in Patent Document 2 with components other than the organic solvent, such as a black pigment, from among the components contained in the light-shielding coating disclosed in Patent Document 1. This is expected to result in an aqueous coating that can form an internal reflection prevention coating film that not only has excellent optical properties but also has excellent adhesion to low-polarity resins.

[0017] Therefore, the present inventors investigated the preparation of an internal reflection preventing coating by dispersing a black pigment, dye, or the like in a water-based coating agent containing an acid-modified polyolefin resin as disclosed in Patent Document 2. However, as mentioned above, there were cases where the film-forming properties and the adhesion of the formed coating film to the substrate were reduced, and cases where aggregates were generated in the coating, causing unintended thickening or gelation, etc., resulting in a reduction in the optical properties of the coating film.

[0018] As a result of further investigation, the present inventors have found that the above object can be achieved when the binder resin contains an acid-modified polyolefin resin containing an ethylene component and a propylene component in a specific ratio, and further when a specific carbon black and a specific thickener are used.

[0019] Specifically, the present invention provides an anti-reflective coating composition comprising a binder resin, a black pigment, a thickener, and an aqueous medium, wherein the binder resin comprises an acid-modified polyolefin resin and a polyurethane resin, the acid-modified polyolefin resin is composed of a propylene component and an ethylene component, the mass ratio of the propylene component to the ethylene component in the acid-modified polyolefin resin being in the range of 10:90 to 60:40, the content of the acid-modified polyolefin resin in the anti-reflective coating composition being 60% by mass or more when the residual content of the anti-reflective coating composition at 105°C is taken as 100% by mass, the black pigment is carbon black having a particle size (D90) of 200 nm or less in a volume-based particle size distribution, the carbon black is coated with a nonionic surfactant, and the thickener is a urethane associative thickener. The elements constituting the anti-reflective coating composition of the present invention are described in detail below.

[0020] <Binder Resin> The internal reflection-preventing coating of the present invention contains an acid-modified polyolefin resin and a polyurethane resin as binder resins. By including a specific proportion of the acid-modified polyolefin resin in the coating film, good adhesion can be achieved even to substrates made of low-polarity resins, such as cyclic olefin resins (hereinafter sometimes referred to as "COP") and cyclic olefin copolymers. Furthermore, the inventors have discovered that by configuring the olefin component, which is the main component of the acid-modified polyolefin resin, with propylene and ethylene in a specific ratio range, both adhesion and film-forming properties can be achieved. That is, for low-polarity resin compositions, the propylene component is believed to contribute significantly to improving adhesion, while the ethylene component is believed to be highly effective in improving film-forming properties. Therefore, it is believed that controlling their component ratios allowed for both excellent film-forming properties and adhesion.

[0021] Acid-modified polyolefin resins are polyolefin resins that have been acid-modified with an unsaturated carboxylic acid component. Examples of unsaturated carboxylic acid components include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, fumaric acid, and crotonic acid. Among these, acrylic acid and maleic anhydride are preferred. The unsaturated carboxylic acid component may be copolymerized in the acid-modified polyolefin resin, and the form of the copolymer is not limited. Specific examples of the copolymerization state include graft copolymerization.

[0022] The graft amount of unsaturated carboxylic acid, unsaturated carboxylic acid anhydride, and unsaturated carboxylic acid derivative in the acid-modified polyolefin resin is preferably 0.5% by mass or more, more preferably 1% by mass or more. A graft amount of 0.5% by mass or more facilitates the formation of an aqueous dispersion composition of the acid-modified polyolefin resin, and the adhesiveness of the aqueous dispersion composition to polar substrates can be maintained. The graft amount is preferably 10% by mass or less. A graft amount of 10% by mass or less can prevent the generation of unreacted materials, and can further enhance the adhesion of the coating film to resins with low polarity.

[0023] The polyolefin resin used as a raw material for obtaining the acid-modified polyolefin resin contains at least one component selected from the group consisting of a propylene component and an ethylene component. The method for obtaining the polyolefin resin is not particularly limited, and examples include copolymerization of ethylene and propylene using a Ziegler-Natta catalyst or a metallocene catalyst as a polymerization catalyst. The raw polyolefin resin may be a single type or a combination of two or more types. That is, the raw polyolefin resin may be a copolymer of ethylene and propylene alone, or a combination of polyethylene and polypropylene, or may further be combined with the above copolymer. The raw polyolefin resin is preferably a polyolefin resin obtained using a metallocene catalyst as a polymerization catalyst. Known metallocene catalysts can be used.

[0024] The acid-modified polyolefin resin is composed of a propylene component and an ethylene component derived from the polyolefin resin used as the raw material. In other words, the propylene component and the ethylene component constituting the acid-modified polyolefin resin are each acid-modified. When the heating residue at 105°C of the internal anti-reflection coating according to the present invention is taken as 100% by mass, the content of the acid-modified polyolefin resin in the internal anti-reflection coating is 60% by mass or more. Furthermore, the mass ratio of the propylene component to the ethylene component in the acid-modified polyolefin resin is in the range of 10:90 to 60:40 (propylene component:ethylene component). The mass ratio of the propylene component to the ethylene component in the acid-modified polyolefin resin is preferably in the range of 30:70 to 49:51 (propylene component:ethylene component). By having the mass ratio of the propylene component in the acid-modified polyolefin resin be 10% or more, sufficient adhesion of the coating film to a substrate made of a resin with low polarity can be obtained. Furthermore, when the mass ratio of the ethylene component in the acid-modified polyolefin resin is 40% or more, sufficient film-forming properties can be obtained on a substrate made of a resin with low polarity.

[0025] In the present invention, the heating residue (solid content) of an internal anti-reflection coating at 105°C refers to the amount of residue when the coating is dried at 105°C for 60 minutes. The detailed measurement method is as follows: First, the weight of the aluminum cup is measured (measured value A). Approximately 1.0 g of the measurement object (coating) is weighed onto the aluminum cup (measured value B) and air-dried for 30 minutes. After that, the sample is dried in an electric furnace in an atmosphere of 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 weight 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 %) according to the following formula: Solid content (mass %) = 100 × (measured value C - measured value A) / measured value B

[0026] The internal reflection preventing coating material according to the present invention also contains a polyurethane resin as a binder resin. By including a polyurethane resin in the binder resin in addition to an acid-modified polyolefin resin, it is possible to form a coating film that has good adhesion even to substrates made of highly polar resins or glass.

[0027] Polyurethane resins are polymers having urethane bonds in the main chain, and are obtained, for example, by the reaction of a polyol compound with a polyisocyanate compound. Polyether-type polyurethane resins are preferred from the viewpoint of improving adhesion to highly polar resins and glass.

[0028] The polyol compound includes a polyether polyol. Examples of polyether polyols include polyoxyethylene polyols such as polyethylene glycol, polyoxypropylene polyols such as polypropylene glycol, and polyoxyethylene / propylene polyols such as polytetramethylene ether glycol. Among these, polyether diols such as polyethylene glycol and polytetramethylene glycol are preferred because of their ease of availability, with polytetramethylene glycol being more preferred. As polyols other than polyether polyols, 1,3-butanediol, 1,4-butanediol, 1,2-propanediol, 1,3-propanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, methyl-1,5-pentanediol, 1,8-octanediol, 2-ethyl-1,3-hexanediol, and the like may also be used within the scope of the present invention.

[0029] On the other hand, the polyisocyanate compound constituting the polyurethane resin can be one or a mixture of two or more aromatic, aliphatic, or alicyclic diisocyanates. Specific examples of diisocyanates include tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,3-phenylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, 1,5-naphthalene diisocyanate, isophorone diisocyanate, dimethyl diisocyanate, lysine diisocyanate, hydrogenated 4,4'-diphenylmethane diisocyanate, hydrogenated tolylene diisocyanate, dimer diisocyanate in which the carboxyl group of a dimer acid is converted to an isocyanate group, and adducts, biurets, and isocyanurates thereof. Of these, isophorone diisocyanate is preferred from the viewpoint of improving adhesion.

[0030] The content of polyurethane resin in the internal reflection anti-coating according to the present invention is not particularly limited, but when the heating residue of the coating at 105°C is taken as 100% by mass, the content of polyurethane resin is preferably 7.0% by mass or more but less than 17.0% by mass. Furthermore, the content of urethane resin is more preferably 9.0% by mass or more but less than 15.0% by mass. When the content of polyurethane resin in the coating is 7.0% by mass or more, a coating film having high adhesion to substrates made of highly polar resins or glass can be formed. Furthermore, when the content of polyurethane resin in the coating is less than 17.0% by mass, a coating film having high adhesion to substrates made of low polarity resins can be formed.

[0031] The content ratio of the propylene component to the ethylene component and the content ratio of the ethylene component to the polyurethane in the binder resin can be calculated as follows: That is, the binder resin is measured by Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance (H-NMR), and gas chromatography mass spectrometry (GC-MS), and the respective values ​​can be calculated using the obtained results.

[0032] <Black Pigment> The internal reflection preventing coating material according to the present invention contains, as a black pigment, carbon black having a particle size (D90) of 200 nm or less, and the carbon black is coated with a nonionic surfactant. In this specification, the particle size (D90) refers to the particle size (D90) in the volume-based particle size distribution.

[0033] By using carbon black with a particle size (D90) of 200 nm or less, internal reflection can be effectively suppressed over a wide range from the visible light region to the near-infrared region (wavelengths of 400 nm to 1,500 nm). This allows for clearer imaging, for example, when applied to an optical element constituting an imaging device as a coating, compared to using carbon black with a particle size (D90) exceeding 200 nm.

[0034] The inventors have also found that the use of carbon black coated with a nonionic surfactant provides high adhesion and film-forming properties and also suppresses unintended thickening and gelation of the coating solution. This makes it possible to suppress deterioration of the optical properties of the coating film due to localization of the black pigment in the coating film and the formation of an uneven coating film. It is believed that the carbon black coated with a nonionic surfactant makes it less susceptible to changes in pH and ionicity in paints using aqueous media.

[0035] Nonionic surfactants are surfactants with hydrophilic groups that do not ionize when dissolved in water, and are therefore less susceptible to the effects of water hardness and electrolytes. Nonionic surfactants that can be used in the present invention are not particularly limited, but include ester types (polyhydric alcohol types) having an ester bond between a polyhydric alcohol such as glycerin, sorbitol, or sucrose and a fatty acid; 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 and a fatty acid, and which have both ester and ether bonds in the molecule; and fatty acid alkanolamide types in which a hydrophobic group and a hydrophilic group are bonded by an amide bond. In the present invention, it is preferable to use ether types, which can provide a more stable dispersion of carbon particles.

[0036] The method for coating (treating) carbon black with a nonionic surfactant is not particularly limited, but examples include a method in which the surfactant is added to a water-dispersed carbon black particle, followed by mixing and stirring. From a manufacturing standpoint, it is preferable to then add the resulting dispersion as is to the paint composition. In the present invention, it is preferable to prepare carbon black coated with a nonionic surfactant in advance and use this as one of the materials in preparing the paint.

[0037] The particle size (D90) of carbon black can be measured by dynamic light scattering. Specifically, for example, it can be measured using a particle size distribution analyzer (trade name: Nanotrac WAVE-EZ150, manufactured by Microtrac Bell Co., Ltd.) as follows: A solution containing the carbon black to be measured is diluted to 0.05% by mass with ion-exchanged water, stirred and mixed with a stirrer for 1 minute, and then placed in the analyzer to measure the particle size distribution.

[0038] In the present invention, the carbon black content in the internal anti-reflection coating is preferably 6.0% by mass or more and 12.0% by mass or less, based on the solid content (coating film) of the internal anti-reflection coating. If the carbon black content in the coating film is 6.0% by mass or more, the effect of absorbing light in the near-infrared region can be fully obtained, and the coating film can exhibit high internal anti-reflection performance. Furthermore, if the carbon black content in the coating film is 12.0% by mass or less, it is possible to suppress scattering of internally reflected light caused by carbon black at the interface with the substrate. The carbon black content in the coating film is more preferably 8.0% by mass or more and 10.0% by mass or less, based on the solid content of the coating. If the carbon black content in the coating film is 8.0% by mass or more and 10.0% by mass or less, the above-mentioned effect of absorbing light in the near-infrared region and the effect of suppressing scattering of internally reflected light can be more effectively exhibited.

[0039] 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 weight loss when heated to 600°C in a nitrogen atmosphere corresponds to the amount of organic matter, and the weight loss when heated to 800°C after switching to an air atmosphere corresponds to the carbon black content.

[0040] <Thickener> The internal reflection preventing coating according to the present invention contains a urethane associative thickener. An associative thickener is a polymer with a molecular weight of several thousand to several tens of thousands, consisting of a hydrophobic portion and a hydrophilic portion. The hydrophobic portion of the thickener associates with itself and with hydrophobic substances such as resins through hydrophobic interactions to form a network structure, thereby thickening the target liquid. Furthermore, a urethane associative thickener is a surfactant that has a hydrophobic group at the molecular end and a urethane structure within the molecule. Furthermore, a urethane associative thickener is also sometimes called a hydrophobe-modified polyoxyethylene urethane resin (HEUR: Hydrophobe-modified Ethoxylated Urethane).

[0041] In the present invention, the use of a urethane associative thickener creates a resin network structure in the paint, effectively suppressing localization of the black pigment during the paint film-forming process (drying) and the deterioration of the optical properties of the paint film due to the formation of an uneven paint film, etc. Therefore, compared to when no urethane associative thickener is used, a paint film with excellent internal reflectance can be formed over a wide range from the visible light region to the near-infrared region (wavelengths of 400 nm to 1,500 nm).

[0042] Examples of commercially available urethane associative thickeners that can be used in the present invention include RHEOBYK-H3300VF and RHEOBYK-L1400VF (both manufactured by BYK Japan KK), ADEKA NOL UH-756VF and ADEKA NOL UH-450VF (both manufactured by ADEKA Corporation). Of these, RHEOBYK-H3300VF and RHEOBYK-L1400VF can be preferably used from the viewpoint of long-term storage stability of the coating material.

[0043] <Aqueous Medium> In the present invention, the aqueous medium refers to a medium whose main component is water, such as ion-exchanged water, pure water, purified water, or distilled water. The aqueous medium may optionally 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. Furthermore, a mixture of multiple aqueous media may be used to control the drying speed after application of the internal reflection prevention coating. The proportion of the aqueous medium in the coating (dilution ratio) can be adjusted as desired depending on the application. For example, the dilution ratio can be adjusted appropriately for application methods such as spraying, dipping, dispenser application, and brush application, or when controlling the coating film thickness depending on the application. Furthermore, the dilution ratio may be changed as needed to adjust the viscosity of the coating to a desired level.

[0044] <Viscosity> The viscosity of the internal reflection anti-coating according to the present invention may be adjusted as appropriate 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 reflection anti-coating is 20 mPa·s or more, dripping can be suppressed and control of the film thickness becomes easy. If the viscosity of the internal reflection anti-coating is 1,000 mPa·s or less, it is possible to suppress film thickness variations and foaming.

[0045] <Other Additives> The internal reflection anti-coating according to the present invention may contain other additives as needed within the range in which the internal reflection anti-coating performance is maintained. Examples of other additives that the coating may contain include an antifoaming agent, a film-forming aid, a crosslinking agent, an adhesion promoter, a leveling agent, an antiseptic, and an anti-fungal agent.

[0046] Since the binder resin in the coating material according to the present invention is an emulsion, if the storage environment is high, some of the emulsion may collapse, resulting in a decrease in the adhesion of the coating film to the substrate and in the anti-reflection performance. In response to this, by adding an appropriate amount of a known silicone-based or acetylene-based leveling agent to the coating material, the collapse of the emulsion can be suppressed, and the stability of performance can be improved even in a high-temperature storage environment.

[0047] Furthermore, in order to improve adhesion, a crosslinking agent for crosslinking the acid-modified polyolefin resin and / or polyurethane resin may be added to the coating material according to the present invention. Examples of the crosslinking agent include isocyanate compounds, melamine compounds, urea compounds, epoxy compounds, carbodiimide compounds, oxazoline group-containing compounds, hydrazide compounds, zirconium salt compounds, and silane coupling agents.

[0048] In the present invention, the coating material preferably further contains at least one selected from the group consisting of a crosslinking agent and a silane coupling agent, from the viewpoint of improving the adhesion of the coating film to the glass.

[0049] These additives may be used singly or in combination depending on the storage environment and application method.

[0050] <Method of manufacturing internal anti-reflection coating> The internal anti-reflection coating according to the present invention can be manufactured by mixing a binder resin, a black pigment, a thickener, an aqueous medium, and other materials. Mixing can be carried out by a known method, and mixing can be carried out using, for example, a magnetic stirrer, a propeller mixer, a ball mill, a paint shaker, a basket mill, a Dyno Mill, an Ultra Visco Mill, an annular disperser, or the like. The form of each material before mixing is not particularly limited, but a method in which each material is first prepared into an aqueous dispersion and then mixed is preferred.

[0051] [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 the binder resin, black pigment, and thickener described above. The thickness of the internal anti-reflection coating film is preferably 0.5 μm or more and 100 μm or less. When the thickness of the internal anti-reflection coating film is 0.5 μm or more, it can effectively absorb light that enters from the side opposite to the surface of the substrate where the paint is applied and then passes through the substrate, thereby achieving a high degree of internal reflection suppression and light blocking effects. 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. The internal anti-reflection coating film preferably has an internal reflectance of 3.0% or less for light with a wavelength of 400 nm to 1500 nm. Furthermore, the adhesive strength of the internal anti-reflection coating film to cyclic olefin resin (COP resin) is preferably 10 N or more.

[0052] <Method for Producing an Internal Anti-Reflection Coating Film> The internal anti-reflection coating film according to the present invention can be produced by applying the internal anti-reflection coating material according to the present invention described above to a substrate and then drying it. Known substrates, such as glass and resin, can be used as the substrate on which the coating film is formed. The method for forming the coating film 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. The drying method may be any method that volatilizes the aqueous medium and subsequently fuses the dispersed particles of the resin used to one another, and any known drying method may be selected according to the intended application and the required drying speed. Examples of known drying methods include heating using an electric furnace, hot air, and far infrared rays. The drying temperature is also not particularly limited, but a temperature of 80°C to 110°C is preferred because it is less likely to cause changes in the dispersion state of the black pigment, etc. in the coating during drying and does not require a long drying time.

[0053] [Optical Element] The optical element according to the present invention has the above-described internal antireflection coating film according to the present invention. Specifically, for example, an optical element according to the present invention may have the internal antireflection coating film according to the present invention formed on the non-transmitting surface of a lens.

[0054] The present invention will be described in further detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. Table 1 shows the materials used in each example and comparative example. Table 2 also shows the types of substrates used to apply the internal reflection prevention coating. PP, PE, and PU shown in Table 1 indicate the mass-based content ratios of the propylene component, ethylene component, and polyurethane, respectively. Each content ratio was calculated from the results of FT-IR, H-NMR, and GC-MS measurements. The heating residue was calculated by preparing a solid according to the definition of solid content described above and measuring its weight.

[0055]

[0056]

[0057] <Preparation of Internal Anti-Reflection Coating> The materials were mixed in the ratios shown in Tables 3 and 4 to obtain internal anti-reflection coatings for Examples 1 to 24 and Comparative Examples 1 to 9. Mixing conditions included a 5-L stainless steel cylinder and a propeller mixer, with the total liquid volume set to 3.0 kg. For Examples 1 to 15, 18, 19, and 24 and Comparative Examples 1 to 7, the binder resin was first mixed in the ratios shown in Tables 3 and 4 and stirred and mixed for 10 minutes. A black pigment was then added and stirred and mixed for an additional 10 minutes. Next, a leveling agent was added as an additive and stirred and mixed for an additional 10 minutes. Next, a thickener was added while stirring, and the mixture was stirred and mixed for an additional 10 minutes. Finally, the mixture was filtered through a nylon mesh (#100) to obtain internal anti-reflection coatings. For Examples 16 and 17, ion-exchanged water was added to the coating prepared in the same manner as in Example 1, and the coating was diluted to the viscosity shown in Table 7 to obtain internal anti-reflection coatings. In Example 20, an internal reflection coating was obtained in the same manner as in Example 1, except that no leveling agent was added as an additional additive. In Examples 21 to 23, the materials were mixed in the same order as in Example 1, and immediately before film formation, crosslinkers 1 to 3 were added as additional additives, respectively, followed by stirring and mixing for 10 minutes to obtain an internal reflection coating. In Comparative Example 8, since the thickener was in paste form, an internal reflection coating was obtained in the same manner as in Example 1, except that a 10% by mass aqueous solution of the thickener was prepared in advance and added. In Comparative Example 9, since the thickener was in powder form, an internal reflection coating was obtained in the same manner as in Example 1, except that a 1% by mass aqueous solution of the thickener was prepared in advance.

[0058] [Rule 26, 16.07.2024]

[0059]

[0060] <Preparation of Internal Antireflection Coating Films A-1 and A-2> The internal antireflection coating obtained in the preparation of the internal antireflection coating material described above was applied to a slide plate of a cyclic olefin polymer resin (COP) substrate using a wire bar (wet film thickness 12 μm), air-dried for 5 minutes, and then dried at 105° C. for 30 minutes to prepare internal antireflection coating film A-1. Furthermore, the drying temperature after air-drying was changed to 80° C. to prepare internal antireflection coating film A-2.

[0061] <Preparation of Internal Antireflection Coating Films B-1 and B-2> Internal antireflection coating films B-1 (drying temperature 105°C) and B-2 (drying temperature 80°C) were prepared in the same manner as for internal antireflection coating films A-1 and A-2, except that the type of substrate used was changed from a cycloolefin polymer resin (COP) substrate slide plate to a polycarbonate resin (PC) slide plate.

[0062] <Preparation of Internal Antireflection Coating Films C-1 and C-2> A right-angled triangular prism (30 × 30 mm, t 15 mm, apex angle 90°) was prepared as a substrate. First, all surfaces of the right-angled triangular prism were polished to a mirror finish using #2000 waterproof sandpaper. Next, the right-angled triangular prism was held using a jig with the bottom surface (hypothetic side surface) of the right-angled triangular prism facing upward and horizontal, and the internal antireflection coating material obtained above was applied to the bottom surface of the right-angled triangular prism using a wire bar (wet film thickness 12 μm). Thereafter, the resultant was dried at 105 ° C. for 30 minutes to prepare an internal antireflection coating film C-1. Furthermore, the drying temperature after air drying was changed to 80 ° C. to prepare an internal antireflection coating film C-2.

[0063] <Evaluation> The internal reflection preventing paints and internal reflection preventing coating films A-1 to C-1 and A-2 to C-2 prepared in each of the Examples and Comparative Examples were evaluated as follows.

[0064] [Breakdown of Components of Internal Anti-Reflection Coating] Tables 5 and 6 show the results of calculating the breakdown of each component (ratio of each component on a mass basis) from the material composition shown in Table 1.

[0065] [Rule 26, 16.07.2024]

[0066]

[0067] [Viscosity] The viscosity was measured at a temperature of 23±1°C using a TVB-15 viscometer (manufactured by Toki Sangyo Co., Ltd.) equipped with a THM-type small sample adapter. The rotor rotation speed was adjusted appropriately to be optimal depending on the viscosity of the liquid to be measured. The measurement results are shown in Tables 7 and 8. In Table 8, N.D. indicates that the paint gelled and therefore measurements and evaluations could not be performed.

[0068] [Film-forming properties] Film-forming properties were confirmed using internal anti-reflection coating films A-1 and B-1. The surface condition of internal anti-reflection coating film A was visually observed and rated as follows: A: Uniform surface condition with absolutely no cissing, cracking, or uneven film thickness with respect to the substrate. B: No cissing or cracking with respect to the substrate, but slight unevenness in film thickness observed. C: Occurrence of cissing or cracking with respect to the substrate, or significant unevenness in film thickness observed. The evaluation results are shown in Tables 7 and 8.

[0069] [Adhesion] The adhesion between the internal reflection anti-coating film and the substrate was evaluated using internal reflection anti-coating films A-1, A-2, B-1, and B-2 based on the cross-cut method (JIS K 5600-5-6:1999) as follows: A: "Class: 0" or "Class: 1" in the cross-cut evaluation B: "Class: 2" or "Class: 3" in the cross-cut evaluation C: "Class: 4" or "Class: 5" in the cross-cut evaluation The evaluation results are shown in Tables 7 and 8.

[0070] [Internal Reflectance] [Method for Measuring Internal Reflectance] Internal reflectance was measured using internal antireflection coatings C-1 and C-2. As shown in FIG. 1 , a right-angled triangular prism provided with an internal antireflection coating 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. The incident light 12 was refracted upon entering the right-angled triangular prism 10, incident on the internal antireflection coating 3 at an incident angle θ, and further reflected to emit 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 right-angled triangular prism 10 to the tangent surface 16 of the integrating sphere entrance was 15√√2 mm, and the opening diameter B of the integrating sphere 14 was φ15 mm. Without the right-angled triangular 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 designated as 100% internal reflectance. Then, with the right-angled triangular prism 10 provided with the internal reflection anti-reflection coating 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 right-angled triangular prism 10 was not installed was calculated. The arithmetic mean of the percentages obtained at each wavelength was then calculated to represent the internal reflectance (L) of the sample. The internal reflection light intensity was similarly measured for light with wavelengths of 700 nm to 1500 nm, and the arithmetic mean of the percentage was calculated to obtain the internal reflectance (M) of the sample. The internal reflectance (L) in the visible light region (400 nm to 700 nm) obtained as described above was evaluated for internal reflection prevention performance according to the following criteria: A: Internal reflectance (L) is 2.0% or less B: Internal reflectance (L) is greater than 2.0% and 3.0% or less C: Internal reflectance (L) is greater than 3.0% The internal reflectance (M) in the near-infrared region (700 nm to 1500 nm) obtained as described above was evaluated for internal reflection prevention performance according to the following criteria: A: Internal reflectance (M) is 2.0% or less B: Internal reflectance (M) is greater than 2.0% and 3.0% or less C: Internal reflectance (M) is greater than 3.0%

[0071] [COP Adhesion] The adhesive strength (COP adhesion) to a cyclic olefin resin (COP resin) was evaluated as follows. The internal antireflection coating material according to each Example and Comparative Example was applied to a cyclic polyolefin (COP) film (ZEONOR film, 100 μm thick, manufactured by Zeon Corporation) using a Mayer bar so that the dried coating thickness was 5 μm, and then dried at 100°C for 1 minute. The resulting laminates were pressed in a heat press at 120°C and a sealing pressure of 0.8 MPa for 10 seconds, with the coating surfaces of the laminates in contact with each other. The pressed laminates were cut into 15 mm widths and left for 1 day. The peel strength of the coating was measured using a universal testing machine (manufactured by A&D Co., Ltd.) at a tensile speed of 500 mm / min and a tensile angle of 180°. The measured values ​​were evaluated as COP adhesion according to the following criteria. A: COP adhesion force is 15 N or more B: COP adhesion force is less than 15 N, 10 N or more C: COP adhesion force is less than 10 N Tables 7 and 8 show the evaluation results.

[0072] [Overall Evaluation] The overall evaluation was performed using the evaluation results of film-forming ability, adhesion, internal reflectance, and COP adhesion according to the following criteria: A: All evaluation results were "A". B: At least one evaluation result was "B" and no "C" was given. C: At least one evaluation result was "C" or "N.D." The evaluation results are shown in Tables 7 and 8.

[0073] [Rule 26, 16.07.2024]

[0074]

[0075] 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.

[0076] This application claims priority based on Japanese Patent Application No. 2023-107234, filed on June 29, 2023, the entire contents of which are incorporated herein by reference.

[0077] 3. Internal anti-reflection coating 10. Right-angle triangular prism 11. Light source 12. Incident light 13. Internally reflected light 14. Integrating sphere 15. Plumb line (perpendicular line) to the base of the right-angle triangular prism 16. Tangent surface of the entrance to the integrating sphere 17. Polarizing plate 18. Slit

Claims

1. An internal anti-reflective coating containing a binder resin, black pigment, thickener, and aqueous medium, The binder resin comprises an acid-modified polyolefin resin and a polyurethane resin. The aforementioned acid-modified polyolefin resin consists of a propylene component and an ethylene component. In the acid-modified polyolefin resin, the mass ratio of the propylene component to the ethylene component is within the range of propylene component:ethylene component = 10:90 to 60:

40. When the residual content of the internal anti-reflective coating at 105°C is assumed to be 100% by mass, the content of the acid-modified polyolefin resin in the internal anti-reflective coating is 60% by mass or more. The aforementioned black pigment is carbon black having a particle size (D90) of 200 nm or less in a volume-based particle size distribution. The carbon black is coated with a nonionic surfactant. The aforementioned thickening agent is a urethane-associated thickening agent. Internal anti-reflection paint.

2. The anti-reflective coating for the interior surface according to claim 1, wherein the mass ratio of the propylene component to the ethylene component in the acid-modified polyolefin resin is in the range of propylene component:ethylene component = 30:70 to 49:

51.

3. The anti-reflective coating according to claim 1 or 2, wherein, when the residual content of the anti-reflective coating at 105°C is taken as 100% by mass, the carbon black content in the anti-reflective coating is 6.0% by mass or more and 12.0% by mass or less.

4. The anti-reflective coating for the internal surface according to claim 1 or 2, wherein the viscosity of the anti-reflective coating for the internal surface is 20 mPa·s or more and 1,000 mPa·s or less.

5. The anti-reflective coating for internal surfaces according to claim 1 or 2, further comprising at least one selected from the group consisting of crosslinking agents and silane coupling agents.

6. An internal anti-reflective coating film obtained by applying the internal anti-reflective coating paint described in claim 1.

7. The anti-reflective coating film according to claim 6, wherein the anti-reflective coating film has an internal reflectance of 3.0% or less for light with a wavelength of 400 nm to 1500 nm.

8. The anti-reflective coating film on the inner surface according to claim 6, wherein the adhesive strength of the anti-reflective coating film on the inner surface to the cyclic olefin resin is 10 N or more.

9. An optical element having an internal anti-reflective coating according to any one of claims 6 to 8.