CN111909618A

CN111909618A - Inner-surface reflection preventing black coating, inner-surface reflection preventing black coating film, and optical element

Info

Publication number: CN111909618A
Application number: CN202010385868.3A
Authority: CN
Inventors: 中谷直治; 井野口翔大
Original assignee: Canon Chemicals Inc
Current assignee: Canon Chemicals Inc
Priority date: 2019-05-10
Filing date: 2020-05-09
Publication date: 2020-11-10
Anticipated expiration: 2040-05-09
Also published as: JP7129946B2; JP2020186289A; CN111909618B

Abstract

The invention relates to an inner surface reflection preventing black coating, an inner surface reflection preventing black coating film and an optical element. Provided is an internal reflection preventing black paint, which includes: binder resin, coal tar pitch, dye and solvent, wherein toluene insoluble matter of the coal tar pitch is more than 20 mass%.

Description

Inner-surface reflection preventing black coating, inner-surface reflection preventing black coating film, and optical element

Technical Field

The invention relates to an inner surface reflection preventing black coating, an inner surface reflection preventing black coating film and an optical element.

Background

In an optical system constituted by combining optical elements such as a lens and a triangular prism, if light is scattered at the edge and the convex ridge portion of each optical element and peripheral portions such as a rim to generate stray light (stray light), ghost and flare (flare) occur in an image formed by the optical system, deteriorating the image quality.

Therefore, in order to suppress deterioration of image quality due to such stray light, an optical element is used, the inside of which is coated with an inner-reflection preventing black paint to form an inner-reflection preventing black coating film, thereby suppressing the occurrence of ghost images and flare.

Japanese patent publication No. 58-4946 discloses an anti-internal reflection coating for optical glass comprising a vinylidene chloride copolymer which is a copolymer of coal tar or coal tar pitch and vinyl ester or acrylonitrile.

The coating film formed using the inner-surface reflection preventing coating material for optical glass described in Japanese patent publication Sho-58-4946 has excellent performance of preventing inner-surface reflection in an optical element, but there is room for improvement in the anti-reflection performance in terms of solvent resistance and long-term use under high-temperature and high-humidity environments.

Specifically, in the case of a coating film formed by applying an inner surface reflection preventing coating for optical glass described in japanese patent publication No. 58-4946 in the production of an optical element, coal tar pitch in the coating film sometimes melts out in a step of cleaning with a solvent and contaminates the surface of the optical element. In addition, when an optical element having a coating film formed by applying the inner-surface reflection preventing coating material for optical glass described in japanese patent laid-open No. 58-4946 is used for a long period of time under a high-temperature and high-humidity environment, minute spots are formed in the interface between the coating film and the optical element, which lowers the antireflection performance in some cases.

Disclosure of Invention

Accordingly, an object of the present invention is to provide an inner-surface reflection preventing black paint which has high solvent resistance and can form a coating film having excellent inner-surface reflection preventing performance even in long-term use under a high-temperature and high-humidity environment.

Another object of the present invention is to provide an inner-surface reflection preventing black coating film formed using the inner-surface reflection preventing black coating material, and an optical element having the inner-surface reflection preventing black coating film.

The above object is achieved by the present invention described below. That is, an inner reflection preventing black paint according to an aspect of the present invention is an inner reflection preventing black paint including a binder resin, coal tar pitch, a dye, and a solvent, wherein toluene insolubles of the coal tar pitch are 20 mass% or more.

Further, the inner-surface reflection preventing black coating film according to another aspect of the present invention is an inner-surface reflection preventing black coating film comprising a binder resin, coal tar pitch and a dye, wherein

The coal tar pitch has a toluene insoluble matter of 20 mass% or more.

Further, an optical element according to still another aspect of the present invention has the inner-surface reflection preventing black coating film.

According to the present invention, an inner-surface reflection preventing black coating material having high solvent resistance and capable of forming a coating film having excellent inner-surface reflection preventing performance even in long-term use under a high-temperature and high-humidity environment can be provided.

In addition, according to the present invention, an inner-surface reflection preventing black coating film and an optical element can be provided, which have excellent workability and inner-surface reflection preventing performance.

Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.

Drawings

Fig. 1 is a schematic diagram for describing an internal reflection preventing function in an optical element according to the present invention.

Fig. 2 is a schematic diagram for describing inner-face reflection in the optical element according to the present invention.

Fig. 3 is a schematic diagram of a right triangular prism for measuring the intensity of internal regular reflected light.

Fig. 4 is a schematic diagram for describing a measurement method of the intensity of the inner-face regular reflection light.

Fig. 5 is a schematic diagram of an apparatus for measuring the intensity of inner-face diffusely-reflected light.

Detailed Description

Hereinafter, embodiments for carrying out the present invention will be described. Hereinafter, the inner-surface reflection preventing black paint may be simply referred to as "paint", and the inner-surface reflection preventing black coating film may be simply referred to as "coating film".

An interior reflection preventing black paint according to an aspect of the present invention includes a binder resin, coal tar pitch, a dye, and a solvent.

Hereinafter, each component included in the dope will be described in detail.

(coal tar pitch)

The coal tar pitch included in the inner surface reflection preventing black paint according to an aspect of the present invention has a toluene insolubles of 20 mass% or more.

Coal tar pitch is obtained using coal tar, which is produced when coal is carbonized in a coke oven, as a starting material. After removing sludge and ammonia water contained in coal tar or performing combined treatment of distillation and heat treatment by a special process, distillation is performed to obtain a residue, which is coal tar pitch. The proportion of toluene insoluble matter in the coal tar pitch can be adjusted by performing secondary treatment such as thermal modification or vacuum distillation.

The proportion of toluene insolubles in the coal tar pitch can be determined in accordance with JIS K2425: 200614.2.

Conventionally, coal tar pitch having low toluene insolubles is used for coating from the viewpoint of dissolving in the coating at a molecular level. The present inventors have found that not only the inner-face reflection preventing performance equal to or higher than that of the conventional art can be obtained but also the problems associated with the prior art can be solved by using, as a coating component, a coal tar pitch having a low solubility in a solvent in which the toluene insolubles are 20 mass% or more. That is, the coating film formed from the coating material has excellent solvent resistance and excellent inner surface reflection preventing performance in long-term use under a high-temperature and high-humidity environment.

The coal tar pitch used for the coating material preferably has a toluene insoluble matter content of 25 mass% or more and 50 mass% or less. When the toluene insolubles are 25 mass% or more, the resulting coating film can have higher solvent resistance. When the content of the toluene insoluble matter is 50% by mass or less, the effect of maintaining the inner surface reflection preventing performance in the case of using the obtained coating film for a long period of time under a high-temperature and high-humidity environment can be further enhanced.

Toluene insolubles when a plurality of coal tar pitches are used together can be calculated as follows. For example, when 10g of coal tar pitch a (toluene insoluble 20%) and 10g of coal tar pitch B (toluene insoluble 40%) are used together, the toluene insoluble can be calculated as (20% × 10g + 40% × 10g)/20g ═ 30%.

The content of the coal tar pitch used for the coating material is preferably 20 mass% or more and 50 mass% or less based on the total solid content in the coating material.

When the content of the coal tar pitch is 20% by mass or more, the resulting coating film may have higher solvent resistance. When the content of the coal tar pitch is 50% by mass or less, the effect of maintaining the anti-internal reflection performance in the case of using the obtained coating film for a long period of time under a high-temperature and high-humidity environment can be further enhanced.

More preferably, the content of the coal tar pitch used for the coating material is 25 mass% or more and 40 mass% or less based on the total solid content in the coating material.

In the present invention, it is considered that at least a portion of the coal tar pitch in the coating material is dispersed in the form of particles. That is, the degree of dispersion of the coating material measured by a particle meter is preferably 5 μm or more and 50 μm or less. The granulometer measurement can be performed according to JIS K5600-2-5.

When the dispersion degree is 5 μm or more, the coatability of the coating material and the matte effect of the surface of the resulting coating film are improved. When the dispersion degree is 50 μm or less, the effect of maintaining the inner-surface reflection preventing performance in the case of using the obtained coating film for a long period of time under a high-temperature and high-humidity environment can be further enhanced. More preferably, the degree of dispersion of the coating material as measured by a particle meter is 10 μm or more and 30 μm or less.

In order to have a proper value of the dispersibility of the coating material, the coal tar pitch may be pulverized before being mixed with other materials, or may be pulverized during a dispersion treatment after being mixed with other materials.

(dyes)

The dye preferably has an absorption coefficient of 10L/(g cm) or more with respect to light having a wavelength of 555 nm. This makes it possible to obtain a coating film having high inner-face reflection preventing properties. Here, the absorption coefficient corresponds to absorbance measured at an optical path length of 1cm for a solution obtained by dissolving 1g of the dye in 1L of the solvent, and can be determined according to Lambert-Beer law.

As the dye, commercially available dyes can be used. Examples of the dyes that can be used include azo-based, anthraquinone-based, phthalocyanine-based, triallylmethane-based, indigo-based, and metal complex-based dyes, and the like.

Specific dyes include, but are not limited to, c.i. solvent yellow 2, 13, 14, 16, 21, 25, 29, 33, 56, 60, 88, 89, 93, 104, 105, 112, 113, 114, 157, 160, and 163, c.i. solvent red 3, 18, 22, 23, 24, 27, 49, 52, 60, 111, 122, 125, 127, 130, 132, 135, 149, 150, 168, 179, 207, 214, 225, and 233, c.i. solvent blue 7, 14, 25, 35, 36, 58, 59, 63, 67, 68, 70, 78, 87, 94, 95, 132, 136, and 197, c.i. solvent black 3, 5, 7, 27, 28, 29, and 34, c.i. solvent violet 8, 13, 31, 33, and 36, c.i. solvent orange 11, 55, 60, 63, 80, 99, and 114, c.i. solvent brown 42 and 44, c.i. solvent green 8, 5, 42, 5, 17, 5, 1,5, 17, 5, and c.i. direct blue 87, and the like. Commercially available dyes not designated c.i. number may also be used.

The content of the dye in the coating material is preferably 3 mass% or more and 20 mass% or less based on the total solid content. When the content of the dye is 3% by mass or more, a coating film having high inner-surface diffuse reflection preventing performance can be obtained. When the content of the dye is 20% by mass or less, a coating film having high solvent resistance can be obtained.

More preferably, the content of the dye in the coating material is 5 mass% or more and 15 mass% or less based on the total solid content.

(Binder resin)

The binder resin is not particularly limited as long as it is a resin that can closely adhere to the surface of an object to be coated such as an optical element and the like and ensure the strength of a coating film to such an extent that it is harmless when the object to be coated is used.

Specific examples of the binder resin include epoxy resins, urethane resins, acrylic resins, vinyl resins, polyester resins, silicone resins, fluorine resins, phenol resins, nitrocellulose, and the like. Among them, epoxy resins, urethane resins, and acrylic resins are preferable and epoxy resins are more preferable.

Epoxy resins are a general term for compounds having two or more oxirane rings (epoxy groups) in the molecule and are usually cured in combination with a curing agent.

Examples of the epoxy resin include the following: heterocyclic epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, brominated epoxy resin, bisphenol S type epoxy resin, diphenyl ether type epoxy resin, hydroquinone type epoxy resin, naphthalene type epoxy resin, biphenyl type epoxy resin, fluorene type epoxy resin, bisphenol A type formaldehyde novolac type epoxy resin, novolak type epoxy resin, o-cresol formaldehyde novolac type epoxy resin, dicyclopentadiene phenol type epoxy resin, trishydroxyphenylmethane-type epoxy resin, trifunctional-type epoxy resin, tetrahydroxyphenylethane-type epoxy resin, tetrafunctional-type epoxy resin, hydrogenated bisphenol a-type epoxy resin, bisphenol a-nucleated polyol-type epoxy resin, polypropylene glycol-type epoxy resin, glycidyl ester-type epoxy resin, glycidylamine-type epoxy resin, glyoxal-type epoxy resin, alicyclic polyfunctional epoxy compound, and triglycidyl isocyanate (TGIC).

Examples of the curing agent include active hydrogen compounds such as amine-based curing agents, acid or acid anhydride-based curing agents, basic active hydrogen compounds, and imidazoles. As the curing agent, a latent curing agent (latent curing agent) such as ketimine (ketiminated amine), boron trifluoride-amine complex, dicyandiamide, or organic acid hydrazide may be used, and a latent curing agent for ensuring the pot life of the coating material is preferably used. Among them, ketimine is particularly preferable.

Examples of the amine-based curing agent include the following: aliphatic polyamines such as ethylenediamine, diethylenetriamine, and triethylenetetramine; alicyclic polyamines such as isophorone diamine and 1, 3-bisaminomethylcyclohexane; aromatic polyamines such as diaminodiphenylmethane and diaminodiphenylsulfone; linear diamines and secondary and tertiary amines such as tetramethylguanidine, triethanolamine, piperidine, pyridine and benzyldimethylamine; and polyamidoamines such as diethylenetriamine and triethylenetetramine obtained by reacting a dimer acid with a polyamine.

Examples of the acid or acid anhydride-based curing agent include the following: polycarboxylic acids such as adipic acid, azelaic acid, trimellitic acid, pyromellitic acid, and decane dicarboxylic acid; aromatic acid anhydrides such as phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, and 3,3 ', 4, 4' -benzophenone tetracarboxylic anhydride; cyclic aliphatic anhydrides such as maleic anhydride, succinic anhydride, tetrahydrophthalic anhydride and methyltetrahydrophthalic anhydride; and aliphatic anhydrides such as polyhexamic anhydride, polyazelaic anhydride, polysebacic anhydride, dodecenyl succinic anhydride and poly (ethyl) octadecanoic anhydride.

Examples of the basic active hydrogen compound include organic acid dihydrazides and the like.

Examples of imidazoles include 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-heptadecylimidazole (2-heptadececylimidazole), and the like.

In addition to the curing agent, a catalyst may be used to control the curing reaction rate.

Examples of the catalyst include tertiary amines, imidazoles, boron trifluoride-amine complexes, organic acid compounds, phenols, organometallic compounds, and the like.

The polyurethane resin is cured by using a compound having two or more isocyanate groups (isocyanate compound) as a curing agent among compounds having two or more hydroxyl groups (polyols). At this time, a catalyst may be used to control the curing reaction rate.

The isocyanate compound undergoes a curing reaction with an active hydrogen compound having a functional group other than a hydroxyl group, such as an amino group, a mercapto group, and a carboxyl group. Therefore, for example, the strength of the cured coating film and the stability of the coating material can be adjusted by using a polyol and an active hydrogen compound in combination, or by introducing an active hydrogen functional group into the polyol molecule.

The isocyanate compound may be made to coexist with the polyol in the coating material by masking the isocyanate group with a blocking agent in advance, and may be cured by heating at the time of forming a coating film. Alternatively, the curing reaction may be slowed by using an isocyanate compound having a high molecular weight, and curing may be performed by reacting with moisture in the air.

Examples of the polyhydric alcohol include the following:

polyvalent alcohols such as 1, 4-butanediol, 1, 5-pentanediol, 1, 6-hexanediol, ethylene glycol, propylene glycol, glycerin and trimethylolpropane having a relatively low molecular weight, and polypropylene glycol, polybutylene glycol, condensation-type polyester polyol, lactone-type polyester polyol, polycarbonate polyol, polybutadiene polyol, hydrogenated polybutadiene polyol, acrylic polyol, phosphorus-containing polyol, castor oil polyol, hydrogenated castor oil polyol and phenol polyol having a relatively high molecular weight.

Among the above polyols, addition polymers with propylene glycol, condensation polyester polyols, lactone polyester polyols, acrylic polyols, polycarbonate polyols and phenol polyols are preferred. These polyols may be used in combination of two or more kinds as required.

The isocyanate compound is not particularly limited as long as it has two isocyanate groups in one molecule, and examples thereof include the following:

aliphatic diisocyanates such as hexamethylene diisocyanate (HMDI) and trimethylhexamethylene diisocyanate (TMDI); alicyclic diisocyanates such as isophorone diisocyanate (IPDI); aromatic-aliphatic diisocyanates such as Xylylene Diisocyanate (XDI), aromatic diisocyanates such as Tolylene Diisocyanate (TDI) and 4, 4-diphenylmethane diisocyanate (MDI); hydrogenated diisocyanates such as dimer acid diisocyanate (DDI), hydrogenated tdi (htdi), hydrogenated XDI (H6XDI) and hydrogenated MDI (H12 MDI); the dimer, trimer, tetramer and higher polyisocyanates thereof; adducts thereof with polyvalent alcohols such as trimethylolpropane, water or low molecular weight polyester resins; and so on.

Since urethane curing reaction starts when the polyol and isocyanate compounds are mixed in the coating, the pot life is short. In order to extend the pot life, a blocked isocyanate compound in which a reactive group (isocyanate group) of an isocyanate compound is blocked with an appropriate blocking agent may be used.

The end-capping agent is not particularly limited, but examples thereof include the following:

oxime blocking agents such as methyl ethyl ketoxime, acetone oxime, cyclohexanone oxime, acetophenone oxime and benzophenone oxime; phenol-based end-capping agents such as m-cresol and xylenol; alcohol-based blocking agents such as methanol, ethanol, butanol, 2-ethylhexanol, cyclohexanol and ethylene glycol monoethyl ether; lactam-based blocking agents such as caprolactam; diketone-series blocking agents such as diethylmalonate and acetoacetate; thiol-based blocking agents such as thiophenol; urea-based blocking agents such as thiourea; an imidazole-based capping agent; and a urethane-based blocking agent. Among them, lactam-based blocking agents, oxime-based blocking agents, alcohol-based blocking agents, and diketone-based blocking agents are preferable.

Acrylic resins are useful as (meth) acrylate polymers and copolymers thereof. In the present specification, "(meth) acrylate" means acrylate and/or methacrylate.

Examples of (meth) acrylates include the following: alkyl (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and butyl (meth) acrylate; and hydroxyalkyl (meth) acrylates such as hydroxymethyl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate and hydroxypentyl (meth) acrylate.

(solvent)

The solvent is used to ensure the fluidity of the coating material and a commonly known solvent used in coating materials can be applied. Specific examples of the solvent include the following:

chain hydrocarbons such as neopentane, n-hexane, n-heptane and aromatic oil solvents (Solvesso); aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as trichloroethylene and perchloroethylene; alcohols such as methanol, ethanol, isopropanol, and n-butanol; ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; esters such as ethyl acetate and n-butyl acetate; ethers such as cellosolve, butyl cellosolve and cellosolve acetate; and mineral spirits (hydrocarbon oils).

The above solvents may be used alone or in combination of two or more in any ratio.

(Fine particles of silica)

Preferably, the coating material further includes silica fine particles in a content of 3 mass% or more and 25 mass% or less based on the total solid content. Therefore, the viscosity of the coating material can be appropriately adjusted, and the matte effect on the surface of the resulting coating film can be enhanced. That is, when the content of the silica fine particles is 3% by mass or more, the viscosity of the coating material becomes sufficiently high, and therefore, the coating material is less dropped at the time of coating, and it is not necessary to repeatedly apply the coating material to form a coating film having a certain degree of film thickness, thereby preventing a decrease in the work efficiency. When the content of the silica fine particles is 25% by mass or less, the viscosity does not excessively increase, and the occurrence of film thickness unevenness due to coating streaks can be suppressed.

More preferably, the coating material includes 5 mass% or more and 20 mass% or less of silica fine particles based on the total solid content. When the content of the silica fine particles is 5% by mass or more, the coatability can be further improved and the matte effect on the surface of the resulting coating film can be further increased. When the content of the silica fine particles is 20% by mass or less, the storage stability of the coating material can be improved.

The particle diameter of the silica fine particles included in the coating material is preferably 5nm or more and 50nm or less. The particle diameter of the silica fine particles herein is a volume-average primary particle diameter. When the particle diameter of the silica fine particles is 5nm or more, the rate of increase in viscosity of the coating material with the amount of the silica fine particles does not excessively increase, and the viscosity of the coating material is easily adjusted. In addition, when the particle diameter of the silica fine particles is 50nm or less, an increase in the inner diffuse reflectance of the resulting coating film due to the addition of the silica fine particles can be suppressed.

(silane coupling agent)

The coating may further include a silane coupling agent. When the silane coupling agent is included, the decrease in the inner-surface reflection preventing performance of the resulting coating film can be suppressed even in the case of storing the optical element according to the present invention under a high-temperature and high-humidity environment for a long period of time.

When an optical element having an inner-surface reflection preventing black coating film is stored for a long period of time under a high-temperature and high-humidity environment, minute spots of about 1 μm to 50 μm, which can be observed with a microscope, appear at the interface between the coating film and the optical element. It is considered that the fine spots are caused by peeling at the fine interface, and the spots are generated at positions having no function of preventing the inner surface reflection and causing an increase in the inner surface reflectance as a whole.

Therefore, for the purpose of increasing close adhesion between the coating film and the optical element, it is preferable to use a silane coupling agent in order to suppress peeling at the minute interface even if the coating film is stored for a long period of time under a high-temperature and high-humidity environment. It is preferable that the silane coupling agent has at least one active hydrogen group or electron withdrawing group as the reactive functional group.

Examples of the active hydrogen group include a hydroxyl group, an amino group and a mercapto group, and examples of the electron-withdrawing group include an isocyanate group, an epoxy group, a (meth) acryloyl group, a styryl group and a vinyl group.

Particularly when a coating film is formed on a glass optical element, a silane coupling agent forms a chemical bond by a coupling reaction with the surface of the optical element, and also forms a chemical bond by an addition reaction with an active hydrogen compound or an electron-withdrawing compound. By forming continuous chemical bonds from the inside of the coating film to the surface of the optical element through both chemical bonds, it is possible to suppress the occurrence of minute spots at the interface between the coating film and the optical element even in the case of storing the optical element for a long period of time under a high-temperature and high-humidity environment.

Examples of the hydroxyl group-containing silane coupling agent include the following: n, N-bis (2-hydroxyethyl) -3-aminopropyltriethoxysilane, 2-bis (3-triethoxysilylpropoxymethyl) butanol, N- (2-hydroxyethyl) -N-methylaminopropyltrimethoxysilane.

Examples of the amino group-containing silane coupling agent include the following: 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3- (2-aminoethylamino) propyltrimethoxysilane, 3- (2-aminoethylamino) propylmethyldimethoxysilane, 3-phenylaminopropyltrimethoxysilane, bis (trimethoxysilylpropyl) amine, N-butylaminopropyltrimethoxysilane, N-methylaminopropyltrimethoxysilane and ketiminosilane (ketiminane).

Examples of the mercapto silane-containing coupling agent include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, and 3-mercaptopropyltriethoxysilane.

Examples of the isocyanate-containing silane coupling agent include 3-isocyanato (isocyanato) propyltrimethoxysilane and 3-isocyanatopropyltriethoxysilane.

Examples of the epoxy group-containing silane coupling agent include the following: 2- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane and 3-glycidoxypropyltriethoxysilane.

Examples of the (meth) acryloyl group-containing silane coupling agent include the following: 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-acryloxypropyltriethoxysilane.

Examples of the silane coupling agent containing a styryl group include p-styryl-trimethoxysilane, and examples of the silane coupling agent containing a vinyl group include vinyltrimethoxysilane and vinyltriethoxysilane.

In addition to these monomeric silane coupling agents, silicone alkoxy oligomers having alkoxy groups in a relatively low molecular silicone backbone may be used as the silane coupling agent. Specific examples of silicone alkoxy oligomers include the following: x-40-2651 (product name, containing amino group), X-41-1805 (product name, containing mercapto group), X-41-1818 (product name, containing mercapto group), X-41-1810 (product name, containing mercapto group), X-41-1053 (product name, containing epoxy group), X-41-1059A (product name, containing epoxy group), X-40-2655A (product name, containing methacryl group), and KR-513 (product name, containing acrylic group) (all manufactured by Shin-Etsu Chemical Co., Ltd.). The amount of alkoxy groups in the silicone alkoxy oligomer molecule is preferably 5 to 80% by mass, and the active group equivalent is preferably 100 to 1000 g/eq.

The coating material preferably contains 0.5 mass% or more and 10.0 mass% or less of a silane coupling agent based on the entire coating material. When the content is 0.5% by mass or more, the effect of reducing the inner-surface reflection preventing performance of the obtained coating film can be enhanced even if the optical element is stored for a long period of time under a high-temperature and high-humidity environment. In addition, when the content is 10.0 mass% or less, occurrence of "dripping" due to the unreacted coupling agent remaining temporarily as a liquid after evaporation of the solvent during coating can be prevented.

The silane coupling agent may be used alone or in combination of two or more.

(other additives)

The coating material may include various additives in addition to the above materials as long as the effects of the present invention are not impaired. Various additives are used for, for example, viscosity adjustment of a coating material, improvement of close adhesion of the resulting coating film to a substrate, improvement of leveling property of the resulting coating film, matte surface of the resulting coating film, adjustment of black color tone, improvement of light resistance of the resulting coating film, antifungal properties, rust prevention, and the like.

For adjusting the viscosity of the coating material, for example, a thickener such as bentonite, a silicone elastomer, a thickening polysaccharide, or a glycol, or a diluting solvent may be used.

In order to improve the close adhesion between the obtained coating film and the substrate, a silicone-based coupling agent, an aluminate-based coupling agent, a titanate-based coupling agent, or the like may be used in addition to the silane coupling agent.

In order to improve the leveling property of the resulting coating film, leveling agents such as silicone oils and surfactants can be used.

In order to enhance the matte property of the surface of the obtained coating film, resin particles having a size of about 0.1 μm or more and 20 μm or less, glass powder, quartz powder, mica powder, or the like can be used.

For adjusting the black tone, a dye, an organic pigment, or an inorganic pigment may be used as a complementary color.

In order to improve the light resistance of the resulting coating film, benzophenone-based, salicylate-based, triazine-based, or benzotriazole-based, zinc oxide fine particles, titanium oxide fine particles, or the like can be used as the ultraviolet absorber.

Fungicides can be used to combat fungi and rust inhibitors can be used to prevent rust.

Fig. 1 is a schematic diagram for describing an internal reflection preventing function in an optical element according to the present invention. In fig. 1, a lens 1 as an optical element according to the present invention has an inner-surface reflection preventing black coating film 2 according to the present invention at an edge portion thereof. The inner-surface reflection preventing black coating film 2 is a coating film formed using the inner-surface reflection preventing paint according to an aspect of the present invention. That is, the inner-reflection preventing black coating film 2 includes a binder resin, coal tar pitch, and a dye, and the toluene-insoluble matter of the coal tar pitch is 20 mass% or more.

The lens 1 has an inner-surface reflection preventing black coating 2 on its edge portion, which suppresses and prevents incident light 3 incident from outside the lens 1 from reaching the edge portion and reflecting light (stray light) 4 on its inner surface. Therefore, the occurrence of ghost and flare in an image formed by the optical system including the lens 1 can be suppressed.

Fig. 2 is a schematic diagram for describing inner-face reflection in the optical element according to the present invention. Light (stray light) 4, which reaches an edge portion and is internally reflected by incident light 3 incident from the outside of the lens 1, can be classified into two types: the inner surface regular reflection light 4a and the inner surface diffused reflection light 4 b. The inner surface normal reflected light 4a is light returning to the inside of the lens 1 at the same angle (incident angle) as the angle when the light incident inside the lens 1 reaches the edge portion of the lens 1. The inner surface diffuse reflected light 4b is reflected at various angles different from the incident angle. Here, the intensity of the inner-surface regular reflection light 4a tends to increase as the incident angle increases (the incident angle approaches 90 °). On the other hand, the intensity of the inner-surface diffusely-reflected light 4b increases as the incident angle decreases (the incident angle approaches 0 °).

The internal specular reflection light greatly affects the occurrence of abnormal images such as ghosts and flare on the image mainly captured by the camera. However, the inner diffuse reflected light is also a cause of impaired appearance, so that when the camera lens is viewed from the outside, in addition to the occurrence of an abnormal image due to flare, the blackening property of the antireflection film portion cannot be obtained.

The degree of suppression of the internal-normally reflected light can be evaluated by, for example, measuring the intensity of the internal-normally reflected light by the measuring method shown in fig. 4 using a right-angled triangular prism 5 having a coating film 2 on the entire bottom surface thereof as shown in fig. 3.

That is, the light emitted from the light source 6 passes through the polarizing plate 12 set to be N-polarized light, and the incident light 7 condensed by the slit 13 is incident into the right-angled triangular prism 5 and reflected by the inner face of the coating film 2. Next, the internal-surface regular reflection light 8 emitted from the right triangular prism 5 is received by the integrating sphere 9 provided with the light receiver 14, and the light intensity is measured. At this time, the following conditions affect the measurement value of the internal-surface normally reflected light 8, and therefore care needs to be taken: the direction of the polarizing plate 12, the degree of convergence of the slit 13 to the incident light 7, the size of the right-angled triangular prism 5, the distance a from a perpendicular line (normal line) 10 to the bottom of the triangular prism to the contact surface 11 having the entrance of the integrating sphere, the size of the integrating sphere 9, and the size B of the opening diameter.

In the right-angled triangular prism 5 without the coating film 2, the critical angle of total reflection of the incident light 7 on the bottom surface of the right-angled triangular prism 5 is obtained by the following formula a according to Snell's law:

theta ═ sin-1(sin 90 DEG/n) formula A

Where n is the refractive index of the right triangular prism 5, θ is the angle formed from the vertical line (normal line) 10 to the bottom face of the triangular prism, and the refractive index of air is 1.0.

That is, for example, in the right triangular prism 5 in which n is 1.8

θ＝sin-1(sin 90°/1.8)≈33.7°

This is the critical angle for total reflection, and the incident light 7 causes total reflection within the range of incident angles of 33.7 ° to 90 °.

In order to narrow the range of angles in which such total reflection occurs, it is considered effective to make the refractive index of the coating film 2 close to or higher than the refractive index of the right triangular prism 5.

Further, the degree of suppression of the inner-surface diffuse reflected light can be evaluated by measuring the light intensity based on the inner-surface diffuse reflected light, for example, using the apparatus shown in fig. 5.

That is, first, the integrating sphere 9 provided with the light receiving unit 15 and the light trapping unit 17 and having the incident light opening 19, the regular reflection light trapping opening 20, and the sample mounting opening 21 is mounted in the spectrophotometer. Subsequently, a disk-shaped glass plate 18 provided with the coating film 2 is mounted outside the sample mounting opening 21. At this time, the disk-shaped glass plate 18 is mounted by bringing the surface opposite to the surface having the coating film 2 into contact with the integrating sphere. Thus, the incident light 22 from the light source 6 is caused to enter the disk-shaped glass plate 18 from the surface opposite to the surface having the coating film 2, reach the coating film 2, and be internally reflected. At this time, the inner-surface regular reflection light 23 is absorbed by the regular reflection light catcher 16, emits the inner-surface diffuse reflection light 24 and is collected inside the integrating sphere 9, and the light intensity at each wavelength is measured by the light receiving unit 15.

[ examples ]

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples.

(example 1)

Hereinafter, the following materials were prepared.

Binder resin A (product name: jER828, manufactured by Mitsubishi Chemical Corporation, epoxy resin): 32.0g

Curing agent A (product name: JeR Cure H3, manufactured by Mitsubishi Chemical Corporation): 22.5g

Coal tar pitch A (product name: MCP-110, manufactured by JFE Chemical Corporation, toluene insolubles 30 mass%): 35.0g

Dye A (product name: VALIFAST BLACK 3810, manufactured by Orient chemical industries Co., Ltd., absorption coefficient for light having a wavelength of 555 nm: 31L/(g. cm)): 10.0g

Fine particles of silica (product name: Aerosil #200, manufactured by Nippon Aerosil co., ltd.): 12.0g

Silane coupling agent A (product name: KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd., 3-glycidoxypropyltrimethoxysilane): 11.0g

1-methoxy-2-propanol as solvent (solvent a): 50.0g

Toluene as solvent (solvent B): 50.0g

All the above materials except curing agent A were weighed and placed in a 1.5L ball mill pot with 30 magnetic balls of 20mm diameter. Thereafter, the ball mill pot was placed on a pot mill rotating base and stirred at 60rpm until a suitable degree of dispersion was obtained.

Subsequently, the curing agent a was added to the stirred mixed solution and the mixture was further stirred for 5 minutes, thereby obtaining a coating material according to example 1.

(examples 2 to 27 and comparative examples 1 and 2)

The kind and amount of the material used for preparing the dope in example 1 were changed as shown in table 1. Except for this, the coating materials of examples 2 to 27 and comparative examples 1 and 2 were obtained in the same manner as in example 1.

Here, materials other than the above materials used in examples and comparative examples are as follows:

binder resin B (product name: Nippollan 983, manufactured by Tosoh Corporation, polyol)

Curing agent B (product name: Duranate TPA-100, manufactured by Asahi Kasei Corporation)

Coal tar pitch B (product name: PK-U, manufactured by JFE Chemical Corporation, toluene insoluble 20 mass%)

Coal tar pitch C (product name: MCP-150, manufactured by JFE Chemical Corporation, toluene insoluble 40 mass%)

Coal tar pitch D (product name: MCP-250, manufactured by JFE Chemical Corporation, toluene insoluble 65 mass%)

Coal tar pitch E (product name: MCP-350, manufactured by JFE Chemical Corporation, toluene insoluble 82 mass%)

Coal tar pitch F (product name: PK-QL, manufactured by JFE Chemical Corporation, toluene insoluble 10 mass%)

Dye B (product name: VALIFAST BLUE 603, manufactured by Orient Chemical industries Co., Ltd., absorption coefficient for light having a wavelength of 555 nm: 9.5L/(g. cm))

Dye C (product name: ORASOL BROWN 324, manufactured by BASF, absorption coefficient for light having a wavelength of 555 nm: 10L/(g cm))

Dye D (product name: OIL BLACK HBB, manufactured by Orient Chemical Industries Co., Ltd., absorption coefficient for light having a wavelength of 555 nm: 55L/(g-cm))

Silane coupling agent B (product name: KBE-9007N, manufactured by Shin-Etsu Chemical Co., Ltd., 3-isocyanatopropyltrimethoxysilane)

1-methoxy-2-propanol (as solvent A)

Toluene (as solvent B)

In examples and comparative examples, the dispersion was adjusted as follows. After the materials other than the curing agent were placed in a ball mill pot together with the magnetic balls, stirring was performed at 60rpm until the degree of dispersion shown in table 2 was obtained. For the degree of dispersion, 5g of the mixed solution in the ball mill pot was sampled to measure the degree of dispersion. When the measurement result is higher than the desired dispersion, additional stirring is performed, and 5g of the mixed solution is sampled again to measure the dispersion. Measurement of the dispersion by additional stirring and sampling was repeated until the desired dispersion was obtained. When the degree of dispersion was too low than the predetermined value, each material was again placed in the ball mill pot, and the additional stirring time was set to be shorter, and the degree of dispersion measurement by stirring sampling was repeated. The amount of the curing agent added was adjusted so that the weight ratio was as described in each of the examples and comparative examples in table 1 and used.

TABLE 1

In addition, the content and the degree of toluene insolubles of the coal tar pitch, the degree of dispersion, the absorption coefficient and the content of the dye with respect to light having a wavelength of 555nm, and the content of the silica fine particles included in the coating materials obtained in the above examples and comparative examples are summarized and shown in Table 2.

TABLE 2

[ evaluation ]

(inner surface regular reflectance)

A right-angled triangular prism for evaluation (product name: S-LAH53, manufactured by OHARA inc., n 1.8, and 30mm in length for each of both sides sandwiched at a right angle) polished in advance to a mirror surface on all surfaces was placed on a turntable of a spin coater with the bottom surface facing horizontally upward. Subsequently, the dope according to each example and comparative example was applied on the entire bottom surface by spin coating so that the film thickness was uniform. Then, after drying at room temperature for 30 minutes, curing was carried out in an electric furnace at 140 ℃ for 1 hour to obtain a sample for evaluation of the internal regular reflectance as shown in FIG. 3. When the thickness of the coating film is adjusted to 10 μm or more, the transparency of the coating film is lost.

Subsequently, the right triangular prism 5 having no coating film 2 mounted thereon was mounted in a spectrophotometer and the intensity of the internal-surface normally reflected light for light having a wavelength of 400nm to 700nm was measured in advance at intervals of 5nm by the measurement method shown in fig. 4 described above.

Next, a rectangular prism 5 (sample for evaluation of internal surface regular reflectance) having the coating film 2 was mounted, and the intensity of internal surface regular reflection light with respect to light having a wavelength of 400nm to 700nm was measured in advance at intervals of 5nm by the measurement method shown in fig. 4. The light intensity at each wavelength, which was previously measured in a spectrophotometer using a right-angled triangular prism 5 without the coating film 2, was defined as the inner surface regular reflectance of 100% and the inner surface regular reflectance of the sample for inner surface regular reflectance evaluation was determined. The arithmetic average of the internal surface normal reflectance at each wavelength was defined as the internal surface normal reflectance of the sample. The inner face regular reflectance values obtained from the samples according to examples and comparative examples were evaluated according to the following criteria:

a: less than 35 percent

B: more than 35 percent and less than 45 percent

C: more than 45 percent and less than 55 percent

D: over 55 percent

The results are shown in Table 3.

(inner diffuse reflectance)

The coating materials according to each of examples and comparative examples were applied to a disk-shaped glass plate (product name: S-LAH53, manufactured by OHARA inc., n 1.8,

thickness 1.5 mm). Then, the coating film was dried and cured in the same manner as in the preparation of the sample for inner surface regular reflectance evaluation, thereby preparing a sample for inner surface diffuse reflectance evaluation.

Subsequently, the inner-face diffuse reflectance was measured using the apparatus shown in fig. 5.

First, a standard white plate as the disk-shaped glass plate 18 was mounted in the sample mounting opening 21, the intensity of the inner-surface diffuse reflected light for light having wavelengths of 400nm to 700nm was measured at intervals of 5nm, and the light intensity at each wavelength was defined as the inner-surface diffuse reflectance of 100%. Subsequently, the above-prepared sample for inner surface diffuse reflectance evaluation was mounted as the disk-shaped glass plate 18, and the intensity of inner surface diffuse reflected light for light having a wavelength of 400nm to 700nm was measured at intervals of 5nm, thereby determining the inner surface diffuse reflectance. The arithmetic average of the inner surface diffuse reflectance at each wavelength was defined as the inner surface diffuse reflectance of the sample. The values of the inner surface diffuse reflectance obtained from the samples according to the examples and comparative examples were evaluated according to the following criteria:

a: less than 0.20 percent

B: more than 0.20 percent and less than 0.25 percent

C: more than 0.25 percent and less than 0.30 percent

D: more than 0.30 percent

The results are shown in Table 3.

(durability against aging under high-temperature and high-humidity Environment)

A glass plate was laminated on a disk-shaped glass plate (product name: S-LAH53, manufactured by OHARA inc., n 1.8,

one side of the thickness 1.5mm) (count #600) was subjected to frost treatment (frost processing), and the surface subjected to the frost treatment was coated in the same manner as in the preparation of the sample for evaluation of the internal surface regular reflectance. Thereafter, the sample was heat-cured at 90 ℃ for 1 hour to prepare a sample for evaluation of storage durability with time under a high-temperature and high-humidity environment. Subsequently, after the obtained sample for durability evaluation was left in a high-temperature high-humidity environment (temperature 60 ℃ C. and humidity 90%) for 200 hours, the interface between the glass and the coating film was observed with a microscope for 4mm²Thereby counting the number of white spots having a diameter of 0.02mm or more. The results obtained were evaluated according to the following criteria:

a: less than 10

B: 11 or more and 30 or less

C: 31 or more and 50 or less

D: over 51

The results are shown in Table 3.

(solvent resistance)

The same samples as those for evaluation of storage durability with time under the above-mentioned high-temperature and high-humidity environment were prepared, and the obtained samples were immersed in 50g of methyl ethyl ketone for 3 minutes. Thereafter, the coloring state of methyl ethyl ketone was visually observed. The results obtained were evaluated according to the following criteria:

a: hardly colored

B: slightly colored to light yellow

C: slightly colored black

D: coloring to strong black

The results are shown in Table 3.

TABLE 3

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. An interior reflection preventing black paint, comprising: binder resin, coal tar pitch, dye and solvent, wherein toluene insoluble matter of the coal tar pitch is more than 20 mass%.

2. The inner-face reflection preventing black paint according to claim 1, wherein the content of the coal tar pitch is 20 mass% or more and 50 mass% or less based on the total solid content.

3. The interior reflection preventing black paint according to claim 1 or 2, wherein the degree of dispersion as measured by a particle meter is 5 μm or more and 50 μm or less.

4. The interior reflection preventing black paint according to claim 1 or 2, wherein the dye has an absorption coefficient of 10L/(g-cm) or more for light having a wavelength of 555 nm.

5. The inner-face reflection preventing black paint according to claim 1 or 2, further comprising fine silica particles in a content of 3% by mass or more and 25% by mass or less based on the total solid content.

6. An inner-surface reflection preventing black coating film, comprising: binder resin, coal tar pitch and dye, wherein

The coal tar pitch has a toluene insoluble matter of 20 mass% or more.

7. An optical element comprising the inner-surface reflection preventing black coating film according to claim 6.