Composition for manufacturing metasurface reflectors and method for manufacturing metasurface reflectors

Abstract

The present invention provides a composition for manufacturing metasurface reflectors and a method for manufacturing metasurface reflectors, which can be produced by coating them to create metasurface reflectors with high reflectivity. [Solution] A composition for manufacturing a metasurface reflector, used for forming a pattern on a metasurface reflector or a coating on the pattern, comprising a metal compound, a nitrogen-containing organic compound, and a solvent, wherein the metal compound is at least one selected from the group consisting of metal salts and metal complexes.

Description

[Technical Field]

[0001] The present invention relates to a composition for manufacturing a metasurface reflector and a method for manufacturing a metasurface reflector. [Background technology]

[0002] Metasurface reflectors have been developed that can be designed to obtain a desired reflection angle with respect to the angle of incidence, serving as reflectors for electromagnetic waves (see Patent Documents 1 and 2). When ordinary metal plates are used as reflectors, the metal plates specularly reflect electromagnetic waves, limiting the direction of reflection. For this reason, high-frequency electromagnetic waves, in particular, which have higher directivity than conventional electromagnetic waves, have the disadvantage of not being able to reach terminals etc. if there are shielding objects. In contrast, metasurface reflectors, which have fine patterns formed on their surface, are attracting attention as reflectors that can control the reflection angle of electromagnetic waves. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2021-141359 [Patent Document 2] Japanese Patent Publication No. 2024-56339 [Overview of the project] [Problems that the invention aims to solve]

[0004] To reduce reflection loss in metasurface reflectors, it is desirable for the reflectivity of the pattern surface of the metasurface reflector to be high. Therefore, to increase reflectivity, it is conceivable to create a metal pattern with few impurities by sputtering, or to coat the pattern surface with a metal film with few impurities by sputtering. However, the sputtering method is not suitable for mass production due to its complicated operation.

[0005] The object of the present invention is to provide a composition for manufacturing a metasurface reflector and a method for manufacturing a metasurface reflector that can be produced by coating a metasurface reflector with high reflectivity. [Means for solving the problem]

[0006] The invention made to solve the above problems is a composition for manufacturing a metasurface reflector, which is used to form a pattern on a metasurface reflector or a coating on the above pattern, and contains a metal compound, a nitrogen-containing organic compound, and a solvent, wherein the metal compound is at least one selected from the group consisting of metal salts and metal complexes.

[0007] Another invention made to solve the above problems is a method for manufacturing a metasurface reflector, comprising the steps of directly or indirectly coating a substrate having a pattern or not having a pattern with a metasurface reflector composition, and heating the coating film formed by the coating step, wherein the metasurface reflector manufacturing composition contains a metal compound, a nitrogen-containing organic compound, and a solvent, and the metal compound is at least one selected from the group consisting of metal salts and metal complexes. [Effects of the Invention]

[0008] According to the composition for manufacturing a metasurface reflector and the method for manufacturing a metasurface reflector of the present invention, a metasurface reflector with high reflectivity can be manufactured by coating. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic cross-sectional view showing a first embodiment of a metasurface reflector manufactured using a metasurface reflector manufacturing composition according to one embodiment of the present invention. [Figure 2] Figure 2 is a schematic cross-sectional view showing a second embodiment of a metasurface reflector manufactured using a metasurface reflector manufacturing composition according to one embodiment of the present invention. [Modes for carrying out the invention]

[0010] The following describes in detail a composition for manufacturing a metasurface reflector and a method for manufacturing a metasurface reflector according to one embodiment of the present invention.

[0011] Unless otherwise specified, the upper and lower limits of numerical ranges in this specification may be either "less than or equal to" or "less than," and the lower limit may be either "greater than or equal to" or "greater than." Furthermore, the upper and lower limits can be any combination of the disclosed numerical values. When a numerical range is indicated using the symbol "~," it means that the range includes both the upper and lower limits. For example, "carbon number 1 to 6" means "carbon number 1 or greater and 6 or less."

[0012] In this specification, "hydrocarbon group" includes linear hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups. This "hydrocarbon group" includes saturated hydrocarbon groups and unsaturated hydrocarbon groups. "Linear hydrocarbon group" means a hydrocarbon group that does not contain a ring structure and consists only of a linear structure, and includes both linear hydrocarbon groups and branched hydrocarbon groups. "Alicyclic hydrocarbon group" means a hydrocarbon group that contains only an alicyclic structure as its ring structure and does not contain an aromatic ring structure, and includes both monocyclic alicyclic hydrocarbon groups and polycyclic alicyclic hydrocarbon groups (however, it is not necessary to consist only of an alicyclic structure, and it may contain a linear structure as part). "Aromatic hydrocarbon group" means a hydrocarbon group that contains an aromatic ring structure as its ring structure (however, it is not necessary to consist only of an aromatic ring structure, and it may contain an alicyclic structure or a linear structure as part).

[0013] <Composition for manufacturing metasurface reflectors> The composition for manufacturing a metasurface reflector according to an embodiment of the present invention (hereinafter, also simply referred to as "composition") is used for forming a pattern of a metasurface reflector or a coating of the above pattern, and contains a metal compound (hereinafter, also referred to as "[A] metal compound"), a nitrogen-containing organic compound (hereinafter, also referred to as "[B] nitrogen-containing organic compound"), and a solvent (hereinafter, also referred to as "[C] solvent"), and the [A] metal compound is at least one selected from the group consisting of metal salts and metal complexes.

[0014] The composition can be used to manufacture a metasurface reflector with high reflectivity by coating. Specifically, the composition is used for forming a pattern of a metasurface reflector or a coating of the above pattern, and the pattern itself or the coating formed from the composition has high reflectivity. In other words, since the metal film formed from the composition has high reflectivity, this metal film is useful as the pattern itself or the coating covering the pattern in the metasurface reflector. Therefore, by using the composition, a metasurface reflector can be manufactured with high productivity by coating. Hereinafter, each component constituting the composition will be described in detail.

[0015] [[A] Metal Compound] [A] The metal compound is at least one selected from the group consisting of metal salts and metal complexes. The metal salt and the metal complex may be hydrates. It is preferable that the [A] metal compound is a metal salt.

[0016] As the metal atom contained in the [A] metal compound, atoms of metals with high reflectivity such as gold, silver, copper, etc. are preferable, and copper is more preferable. That is, it is preferable that the [A] metal compound is a copper compound. The metal atoms contained in the [A] metal compound may be one kind or two or more kinds. However, from the viewpoint of forming a highly homogeneous metal film (the pattern itself or the coating covering the pattern), it is preferable that the metal atoms contained in the [A] metal compound are only one kind.

[0017] Examples of the metal salt include salts of the above metal atoms, such as oxoacid salts such as carboxylates, nitrates, sulfates, phosphates, perchlorates, carbonates, borates, etc.; halides such as fluorides, chlorides, bromides, iodides, etc.; hydroxides, and the like. Examples of the carboxylate include formate, acetate, propionate, stearate, naphthenate, citrate, oxalate, succinate, and the like.

[0018] As the metal salt, oxoacid salts are preferred, at least one selected from the group consisting of carboxylates, nitrates and sulfates is more preferred, carboxylates are even more preferred, carboxylates having 1 to 4 carbon atoms are even more preferred, and at least one selected from the group consisting of formate and acetate is particularly preferred.

[0019] Preferable specific examples of the metal salt include, for example, copper formate, copper acetate, copper sulfate, copper nitrate and their hydrates, and the like.

[0020] The metal complex is a compound in which a metal atom and a ligand are bonded by a coordination bond. Examples of the metal atom forming the metal complex include the above-mentioned metal atoms as the metal atoms contained in the [A] metal compound.

[0021] Examples of the ligand include monodentate ligands and polydentate ligands.

[0022] Examples of the monodentate ligand include hydroxo ligand, amide ligand, halogen ligand, alkoxy ligand, acyloxy ligand, amine ligand, phosphine ligand, ammonia ligand, and the like.

[0023] Examples of the amide ligand include unsubstituted amide ligand (NH2), methylamide ligand (NHCH3), dimethylamide ligand (N(CH3)2), diethylamide ligand (N(C2H5)2), dipropylamide ligand (N(C3H7)2), and the like.

[0024] Examples of the halogen ligand include fluorine ligand, chlorine ligand, bromine ligand, iodine ligand, and the like.

[0025] Examples of alkoxy ligands include methoxy ligands, ethoxy ligands, propoxy ligands, and butoxy ligands.

[0026] Examples of acyloxy ligands include acetoxy ligand, ethyloxy ligand, butyryloxy ligand, t-butyryloxy ligand, t-amyryloxy ligand, n-hexanecarbonyloxy ligand, and n-octanecarbonyloxy ligand.

[0027] Examples of amine ligands include methylamine ligands, dimethylamine ligands, piperidine ligands, morpholine ligands, and pyridine ligands.

[0028] Examples of phosphine ligands include trimethylphosphine ligand, triethylphosphine ligand, tributylphosphine ligand, and triphenylphosphine ligand.

[0029] Examples of polydentate ligands include ligands derived from hydroxy acid esters, ligands derived from β-diketones, ligands derived from β-ketoesters, ligands derived from α,α-dicarboxylic acid esters, hydrocarbons having π bonds, and diphosphines.

[0030] Examples of hydroxy acid esters include glycolic acid esters, lactate esters, 2-hydroxycyclohexane-1-carboxylic acid esters, and salicylic acid esters.

[0031] Examples of β-diketones include 2,4-pentanedione, 3-methyl-2,4-pentanedione, and 3-ethyl-2,4-pentanedione.

[0032] Examples of β-ketoesters include acetoacetic acid esters, α-alkyl-substituted acetoacetic acid esters, β-ketopentanoic acid esters, benzoyl acetate esters, and 1,3-acetonedicarboxylic acid esters.

[0033] Examples of α,α-dicarboxylic acid esters include malonic acid diesters, α-alkyl-substituted malonic acid diesters, α-cycloalkyl-substituted malonic acid diesters, and α-aryl-substituted malonic acid diesters.

[0034] Examples of hydrocarbons containing π bonds include linear dienes such as butadiene and isoprene; cyclic dienes such as cyclopentadiene, methylcyclopentadiene, pentamethylcyclopentadiene, cyclohexadiene, and norbornadiene; and aromatic hydrocarbons such as benzene, toluene, xylene, hexamethylbenzene, naphthalene, and indene.

[0035] Examples of diphosphines include 1,1-bis(diphenylphosphino)methane, 1,2-bis(diphenylphosphino)ethane, 1,3-bis(diphenylphosphino)propane, 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl, and 1,1'-bis(diphenylphosphino)ferrocene.

[0036] [A] As the metal compound, a metal salt is preferred, a copper salt is more preferred, and a copper carboxylate is even more preferred. [A] One or more metal compounds can be used. When two or more [A] metal compounds are used, it is preferable to use two metal salts in which the metal atoms are of the same species but the counterions are of different types, it is more preferable to use two metal salts in which the metal atoms are of the same species but the counterions are of different carboxylate ions, and a combination of formate and acetate is even more preferred.

[0037] The lower limit of the content of the [A] metal compound in the composition is preferably 0.5% by mass, more preferably 1% by mass, even more preferably 2% by mass, and even more preferably 3% by mass. The upper limit of the content of the [A] metal compound in the composition is preferably 20% by mass, more preferably 10% by mass, even more preferably 7% by mass, and even more preferably 5% by mass. By having the content of the [A] compound in the composition within the above range as the content of metal atoms contained in the [A] metal compound, it is possible to manufacture a metal film with high reflectivity more efficiently.

[0038] Furthermore, the lower limit of the copper atom or copper ion content in the composition is preferably 0.5% by mass, more preferably 1% by mass, even more preferably 2% by mass, and even more preferably 3% by mass. The upper limit of the copper atom or copper ion content in the composition is preferably 20% by mass, more preferably 10% by mass, even more preferably 7% by mass, and even more preferably 5% by mass.

[0039] [[B]Nitrogen-containing organic compounds] [B] Nitrogen-containing organic compounds are not particularly limited as long as they are organic compounds containing nitrogen atoms, but they include divalent nitrogen-containing groups (-NR) between carbon atoms constituting the chain hydrocarbon. P -) or a structure in which a trivalent nitrogen atom (-N=) is inserted, or a part or all of the hydrogen atoms in a chain hydrocarbon are replaced with a monovalent nitrogen-containing group (-NR Q R R A structure in which the above is substituted, or a structure having a combination thereof, is preferred.

[0040] The above-mentioned chain hydrocarbons are preferably linear or branched chain hydrocarbons having 2 to 20 carbon atoms, and examples include alkanes such as ethane, propane, n-butane, i-butane, n-pentane, isopentane, and neopentane; alkenes such as ethylene, propene, and butene; and alkynes such as acetylene, propyne, and butyne.

[0041] R P 、R Q and R R are each independently a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms. R P 、R Q and R R are preferably a hydrogen atom or a monovalent hydrocarbon group having 1 to 3 carbon atoms, more preferably a hydrogen atom. <>

[0042] <> Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms include a monovalent chain hydrocarbon group having 1 to 20 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms, and the like. <>

[0043] <> Examples of the monovalent chain hydrocarbon group having 1 to 20 carbon atoms include alkyl groups such as methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, sec-butyl group, tert-butyl, n-pentyl group, isopentyl group, neopentyl group; alkenyl groups such as ethenyl group, propenyl group, butenyl group; alkynyl groups such as ethynyl group, propynyl group, butynyl group, and the like. <>

[0044] <> Examples of the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms include cycloalkyl groups such as cyclopentyl group, cyclohexyl group; cycloalkenyl groups such as cyclopropenyl group, cyclopentenyl group, cyclohexenyl group; bridged ring saturated hydrocarbon groups such as norbornyl group, adamantyl group, tricyclodecyl group; bridged ring unsaturated hydrocarbon groups such as norbornenyl group, tricyclodecenyl group, and the like. <>

[0045] <> Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms include phenyl group, tolyl group, naphthyl group, anthracenyl group, pyrenyl group, and the like. <>

[0046] <> R P 、R Q and R RIf the compound has substituents, examples of substituents include monovalent chain hydrocarbon groups having 1 to 10 carbon atoms, halogen atoms such as fluorine, chlorine, bromine, and iodine atoms, alkoxy groups such as methoxy, ethoxy, and propoxy groups, alkoxycarbonyl groups such as methoxycarbonyl and ethoxycarbonyl groups, alkoxycarbonyloxy groups such as methoxycarbonyloxy and ethoxycarbonyloxy groups, acyl groups such as formyl, acetyl, propionyl, and butyryl groups, cyano groups, and nitro groups.

[0047] [B] The nitrogen-containing organic compound preferably has at least one group selected from the group consisting of hydroxyl groups and amino groups, and more preferably has both hydroxyl and amino groups. When the [B] nitrogen-containing organic compound has these groups, the lone pairs of electrons of the hydroxyl and amino groups enhance the interaction between the [A] metal compound and the [B] nitrogen-containing organic compound, improving the homogeneity and fluidity of the composition, and allowing for the more efficient acquisition of a metal film with high reflectivity. The amino group of the [B] nitrogen-containing organic compound is preferably a monovalent group represented by -NH2 or a divalent group represented by -NH-.

[0048] [B] Nitrogen-containing organic compounds preferably have one or two amino groups. Furthermore, [B] nitrogen-containing organic compounds preferably have one or two hydroxyl groups. [B] Nitrogen-containing organic compounds may have a structure in which a divalent amino group (-NH-) is inserted between the carbon atoms constituting the alkane, or one of the hydrogen atoms of the alkane is replaced with a monovalent amino group (-NH2). [B] Nitrogen-containing organic compounds are particularly preferred to have a structure in which one or two of the hydrogen atoms of the alkane are replaced with hydroxyl groups, and a divalent amino group (-NH-) is inserted between the carbon atoms constituting the alkane, or one of the hydrogen atoms of the alkane is replaced with a monovalent amino group (-NH2).

[0049] [B] The upper limit of the molecular weight of the nitrogen-containing organic compound can be, for example, 300, but 200 is preferred, and 150 is more preferred. [B] When the molecular weight of the nitrogen-containing organic compound is below the above upper limit, [B] the nitrogen-containing organic compound is more likely to volatilize during heat treatment after coating, making it easier to obtain a metal film with less organic content and higher reflectivity. [B] The lower limit of the molecular weight of the nitrogen-containing organic compound can be, for example, 50, 70, or 90.

[0050] [B] The upper limit of the boiling point of the nitrogen-containing organic compound at 1 atmosphere is preferably 400°C, more preferably 300°C, even more preferably 250°C, and even more preferably 200°C. [B] When the boiling point of the nitrogen-containing organic compound is below the above upper limit, the nitrogen-containing organic compound is more likely to volatilize during heat treatment after coating, making it easier to obtain a metal film with less organic content and higher reflectivity. [B] The lower limit of the boiling point of the nitrogen-containing organic compound may be 100°C, 120°C, or 150°C.

[0051] [B] Examples of nitrogen-containing organic compounds include compounds represented by the following formulas (B-1) to (B-9).

[0052] [ka]

[0053] [B] The lower limit of the nitrogen-containing organic compound content is preferably 0.5 moles, more preferably 1.0 mole, and even more preferably 1.5 moles per 1.0 mole of the metal compound [A]. The upper limit of the above content is preferably 5.0 moles, more preferably 4.0 moles, even more preferably 3.0 moles, and even more preferably 2.5 moles per 1.0 mole of the metal compound [A]. By setting the content of the nitrogen-containing organic compound [B] within the above range, the reflectivity of the resulting metal film can be further increased.

[0054] [[C] Solvent] [C] The solvent is not particularly limited, but it is preferable that it contains an organic solvent. Examples of solvents other than organic solvents include water. The lower limit of the organic solvent content in [C] is preferably 80% by mass, more preferably 90% by mass, even more preferably 97% by mass, and still more preferably 99% by mass. The upper limit of the above content may be 100% by mass, 99.9% by mass, or 99% by mass.

[0055] Examples of organic solvents include alcohol-based solvents, ketone-based solvents, ether-based solvents, and ester-based solvents.

[0056] Examples of alcohol-based solvents include monoalcohol solvents such as methanol, ethanol, propanol, and butanol; and polyhydric alcohol solvents such as ethylene glycol, propylene glycol, triethylene glycol, and tripropylene glycol.

[0057] Examples of ketone solvents include linear ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone; and cyclic ketone solvents such as cyclohexanone.

[0058] Examples of ether-based solvents include polyhydric alcohol ether-based solvents and polyhydric alcohol partial ether-based solvents. Examples of polyhydric alcohol ether-based solvents include linear ether-based solvents such as n-butyl ether and cyclic ether-based solvents such as tetrahydrofuran and 1,4-dioxane. Examples of polyhydric alcohol partial ether-based solvents include propylene glycol monoethyl ether, tripropylene glycol monomethyl ether, and tetraethylene glycol monomethyl ether.

[0059] Examples of ester solvents include carbonate solvents such as diethyl carbonate; acetic acid monoester solvents such as methyl acetate and ethyl acetate; lactone solvents such as γ-butyrolactone; polyhydric alcohol partial ether carboxylate solvents such as diethylene glycol monomethyl ether acetate and propylene glycol monomethyl ether acetate; and lactic acid ester solvents such as methyl lactate and ethyl lactate.

[0060] [C] The solvent is preferably at least one selected from the group consisting of alcohol-based solvents and ether-based solvents, more preferably at least one selected from the group consisting of monoalcohol-based solvents, polyhydric alcohol-based solvents and polyhydric alcohol partial ether-based solvents, and even more preferably at least one selected from the group consisting of butanol, propylene glycol, and propylene glycol monoethyl ether. The lower limit of the carbon number of the [C] solvent is preferably 2, more preferably 3. The upper limit of the carbon number of the [C] solvent is preferably 6, more preferably 5, and even more preferably 4. The lower limit of the boiling point of the [C] solvent is preferably 80°C, more preferably 100°C. The upper limit of the boiling point of the [C] solvent is preferably 300°C, more preferably 250°C, and even more preferably 200°C. By using such a [C] solvent, it is possible to manufacture metal films with high reflectivity more efficiently. One or more types of [C] solvents can be used.

[0061] The lower limit of the [C] solvent content in the composition is preferably 50% by mass, but may be 60% by mass or 70% by mass. The upper limit of the above content is preferably 95% by mass, but may be 90% by mass or 85% by mass. By setting the [C] solvent content within the above range, the fluidity of the composition can be controlled, and metal films with high reflectivity can be manufactured more efficiently.

[0062] [Other optional components] The composition may contain any components other than [A] metal compounds, [B] nitrogen-containing organic compounds, and [C] solvents. Examples of optional components include polymer additives and surfactants.

[0063] When the composition contains polymer additives, it can improve the coatability on substrates and the continuity of the coating film. One or more polymer additives can be used.

[0064] Examples of polymer additives include fluorine-containing polymer compounds and non-fluorine polymer compounds.

[0065] Examples of fluorine-containing polymer compounds include those described in Japanese Patent Publication No. 2011-89090. Examples of fluorine-containing polymer compounds include compounds containing repeating units derived from a (meth)acrylate compound having a fluorine atom and repeating units derived from a (meth)acrylate compound having two or more (preferably five or more) alkylene oxy groups (preferably ethylene oxy groups, propylene oxy groups).

[0066] Examples of non-fluorinated polymer compounds include linear or branched alkyl(meth)acrylates such as lauryl(meth)acrylate, 2-ethylhexyl(meth)acrylate, n-butyl(meth)acrylate, t-butyl(meth)acrylate, isooctyl(meth)acrylate, isostearyl(meth)acrylate, and isononyl(meth)acrylate; alkoxyethyl(meth)acrylates such as methoxyethyl(meth)acrylate; alkylene glycol di(meth)acrylates such as ethylene glycol di(meth)acrylate and 1,3-butylene glycol di(meth)acrylate; hydroxyalkyl(meth)acrylates such as 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, 2-hydroxybutyl(meth)acrylate, and 4-hydroxybutyl(meth)acrylate; dicyclopentenyloxyethyl(meth)acrylate; and nonylphenoxypolyethylene glycol (-(CH2CH2O) nExamples include compounds having a structure (n=1~17) that contain one or more repeating units derived from (meth)acrylate monomers such as (meth)acrylate.

[0067] If the composition contains a surfactant, it can improve the coatability on substrates and the continuity of the coating film. One or more surfactants can be used.

[0068] Examples of commercially available surfactants include "Newcol 2320", "Newcol 714-F", "Newcol 723", "Newcol 2307", and "Newcol 2303 (all from Nippon Emulsifier Co., Ltd.), "Pionin D-1107-S", "Pionin D-1007", "Pionin D-1106-DIR", "New Calgen TG310", "New Calgen TG310", "Pionin D-6105-W", "Pionin D-6112", "Pionin D-6512" (all from Takemoto Oil & Fat Co., Ltd.), "Surfinol 420", "Surfinol 440", "Surfinol 465", "Surfinol 2502" (all from Nippon Air Products Co., Ltd.), "Megafuck F171", "Same F172", "Same F173", "Same F176", "Same F177", "Same F141", "Same F142", "Same F143", "Same Examples include "F144", "R30", "F437", "F475", "F479", "F482", "F562", "F563", "F780", "R-40", "DS-21", "RS-56", "RS-90", and "RS-72-K" (all from DIC Corporation), "Florard FC430" and "FC431" (both from Sumitomo 3M Co., Ltd.), "Asahi Guard AG710", "Surflon S-382", "SC-101", "SC-102", "SC-103", "SC-104", "SC-105", and "SC-106" (all from AGC Inc.), and "FTX-218" and "NBX-15" (from Neos Co., Ltd.).

[0069] If the composition contains optional components, the upper limit of the content of optional components (total if multiple types are included) is preferably 10 parts by mass, more preferably 5 parts by mass, and may also be 3 parts by mass or 1 part by mass, per 100 parts by mass of the metal compound [A].

[0070] The composition preferably contains a small amount of other metal compounds other than the [A] metal compound (at least one selected from the group consisting of metal salts and metal complexes). Specifically, the upper limit of the content of other metal compounds is preferably 10 parts by mass, more preferably 5 parts by mass, and may be 3 parts by mass, 1 part by mass, or 0.1 parts by mass per 100 parts by mass of the [A] metal compound. By having a small amount of other metal compounds, the metal atoms contained in the [A] metal compound can be distributed with high uniformity in the coating film, and the reflectivity and homogeneity of the resulting metal film can be improved.

[0071] The composition may contain one or more types of metal atoms, but it is preferable that it contains substantially only one type. Specifically, the lower limit of the content of a particular atom among all the metal atoms in the composition may be, for example, 50% by mass or 90% by mass, but 99% by mass is preferred, 99.9% by mass is more preferred, and 99.99% by mass is even more preferred. For example, the lower limit of the content of copper atoms among all the metal atoms in the composition is preferably 99% by mass, 99.9% by mass is more preferred, and 99.99% by mass is even more preferred. When the composition contains substantially only one type of metal atom in this way, a metal film consisting substantially only of that one type of metal atom can be formed, and this metal film can exhibit good reflectivity and other properties.

[0072] [Applications, etc.] The composition is used to form a pattern on a metasurface reflector or a coating over the pattern. The metal film formed by coating and heating the composition becomes either the pattern on the metasurface reflector itself or a coating that covers the pattern.

[0073] The composition may be used in the manufacture of metasurface reflectors for communication waves. Preferably, the composition is used in the manufacture of metasurface reflectors for electromagnetic waves having frequencies in the terahertz region (THz). Electromagnetic waves having frequencies in the terahertz region are expected to be used in sixth-generation mobile communication systems (6G) and beyond, and have short wavelengths and extremely high directivity. On the other hand, the metal film formed from the composition has particularly high reflectivity for electromagnetic waves having frequencies in the terahertz region. Therefore, the composition is particularly useful as a composition for the manufacture of metasurface reflectors for electromagnetic waves having frequencies in the terahertz region, which are expected to see increased use in the future. The terahertz region may be, for example, a frequency band of 100 GHz to 10 THz, or a frequency band of 300 GHz to 3 THz. The composition may also be used in the manufacture of metasurface reflectors for electromagnetic waves in frequency bands other than the terahertz region.

[0074] <Method for manufacturing a composition for a metasurface reflector> The composition can be prepared by mixing [A] a metal compound, [B] a nitrogen-containing organic compound, [C] a solvent, and other components as needed. After mixing, the resulting mixture may be filtered using a filter or the like, if necessary.

[0075] <Metasurface reflector> Examples of metasurface reflectors obtained using the metasurface reflector manufacturing composition according to one embodiment of the present invention include the metasurface reflector 10 shown in Figure 1 and the metasurface reflector 20 shown in Figure 2.

[0076] The metasurface reflector 10 in Figure 1 comprises a substrate 11 having a pattern and a coating 12 directly or indirectly provided on one surface of the substrate 11 (the upper surface in Figure 1). The substrate 11 has a substrate body 11a and a pattern 11b provided on one surface of the substrate body 11a (the upper surface in Figure 1). The pattern 11b has a metamaterial structure. The coating 12 is provided to cover the surface of the substrate 11 on which the pattern 11b is provided (the upper surface in Figure 1). The coating 12 may be provided to directly cover the substrate 11 having the pattern 11b. The coating 12 is a metal film formed from a composition for manufacturing a metasurface reflector according to one embodiment of the present invention.

[0077] The metasurface reflector 20 in Figure 2 comprises a substrate 21 without a pattern and a pattern 22 directly or indirectly provided on one surface of the substrate 21 (the upper surface in Figure 2). The pattern 22 has a metamaterial structure and is a metal film formed by a metasurface reflector manufacturing composition according to one embodiment of the present invention.

[0078] The Metasurface reflectors 10 and 20 have high reflectivity and excellent performance as Metasurface reflectors because the coating 12 or pattern 22 is formed of a Metasurface reflector manufacturing composition according to one embodiment of the present invention. The substrate material and other details of the Metasurface reflector will be explained later in the manufacturing method of the Metasurface reflector. Note that the configuration of the Metasurface reflector is not limited to the structures shown in Figures 1 and 2. For example, a protective layer covering the surface, a ground layer for canceling electromagnetic waves that have passed through the pattern, etc., may be provided.

[0079] <Manufacturing method for metasurface reflectors> A method for manufacturing a metasurface reflector according to one embodiment of the present invention comprises the steps of directly or indirectly coating a metasurface reflector manufacturing composition onto a substrate having or not having a pattern, and heating the coating film formed by the coating step. The metasurface reflector manufacturing composition used in this manufacturing method is the metasurface reflector manufacturing composition according to the embodiment of the present invention described above. According to this manufacturing method, a metasurface reflector with high reflectivity can be manufactured by coating. The steps of this manufacturing method will be described below.

[0080] [Coating Process] In this process, the composition is applied directly or indirectly to a substrate with or without a pattern. This process forms a coating film on the substrate, either directly or indirectly. An example of indirect application of the composition to the substrate is when a surface modification film is formed on the substrate.

[0081] The substrate to be coated may or may not have a pattern.

[0082] In the case of a substrate 11 having a pattern 11b as shown in Figure 1, the pattern 11b has a metamaterial structure. The substrate 11 having a pattern 11b may consist of a substrate body 11a and a pattern 11b, and the substrate body 11a and the pattern 11b may be made of the same material or different materials.

[0083] Examples of substrates include metal substrates, silicon substrates, and resin substrates. Metal patterns are common. Patterns may also be formed from dielectric materials other than metal (such as SiO2, Si3N4, GaN, and TiO2). If the pattern is a metal pattern, the metal constituting the pattern and the metal constituting the film formed from the composition may be the same or different.

[0084] When a pattern is to be formed on the substrate, this pattern can be formed by known methods such as photolithography, nanoimprint, inkjet printing, patterning coating, vapor deposition, and plating. The pattern can be formed, for example, by using a mask to ensure that material is deposited only in a predetermined area. Alternatively, the pattern may be formed by removing material from areas other than the predetermined area by etching or the like.

[0085] The pattern size depends on the frequency of the reflected electromagnetic waves, but can be appropriately designed from a range of, for example, 0.1 μm to 1 mm. For example, in the case of electromagnetic waves with frequencies in the terahertz range, the pattern size may be 1 μm to 500 μm, or 10 μm to 200 μm. The pattern size is selected from the pattern's length, width, major axis, minor axis, height, etc., depending on the pattern's shape.

[0086] The shape of the pattern is not particularly limited; examples of shapes in plan view include convex polygons such as squares and rectangles, concave polygons such as X shapes, and curved shapes such as circles and ellipses. The pattern can also be selected from line and space patterns, trench patterns, hole patterns, dot patterns, etc.

[0087] In the case of a patternless substrate 21 as shown in Figure 2, the metal film formed from the composition becomes the pattern 22. Examples of patternless substrates include metal substrates, silicon substrates, resin substrates, and the like.

[0088] The coating method for the composition is not particularly limited and can be carried out by any suitable method, such as rotary coating, casting coating, or roll coating. Furthermore, when coating a substrate without a pattern, the composition may be coated in a patterned manner by nanoimprint, inkjet printing, patterning coating, or the like.

[0089] After coating the substrate, the coating film may be dried as needed. Conventional known methods can be used for the drying process. The drying temperature is not particularly limited, but 50 to 100°C is preferred. The drying time is also not particularly limited, but 1 to 30 minutes is preferred.

[0090] [Heating process] This step involves heating the coating film formed by the above coating step. This step causes the following components in the coating film to volatilize: [A] anions and ligands constituting the metal compound, [B] nitrogen-containing organic compound, [C] solvent, etc. These components may also volatilize through thermal decomposition. Furthermore, this step reduces the metal atoms in the coating film to zero valence, resulting in a metal film with high reflectivity.

[0091] The lower limit of the heating temperature in this process is preferably 150°C, more preferably 200°C, even more preferably 250°C, and even more preferably 270°C. By heating the temperature above the above lower limit, other components other than metal atoms are particularly sufficiently volatilized, resulting in a metal film with high purity of metal atoms and higher reflectivity. The upper limit of the heating temperature is preferably 500°C, more preferably 400°C, and even more preferably 350°C.

[0092] There are no particular restrictions on the heating time in this process; for example, it may be between 1 minute and 30 minutes, or between 3 minutes and 20 minutes.

[0093] The atmosphere used for heating the coating film is preferably one with an oxygen concentration of 30 ppm or less. The upper limit of the oxygen concentration is more preferably 25 ppm, even more preferably 20 ppm, and particularly preferably 10 ppm. The lower the oxygen concentration, the better, and the lower limit is preferably 0 ppm, but it may also be 0.01 ppm or 0.02 ppm. Heating in a low oxygen concentration atmosphere prevents unintentional oxidation of metal atoms in the coating film and promotes reduction, thereby increasing the reflectivity of the resulting metal film.

[0094] For the heating process, it is preferable to use an inert or non-oxidizing gas, and a nitrogen gas-containing atmosphere is more preferable. By using such an atmosphere during the heating process, the reduction of metal atoms in the coating film can be promoted.

[0095] If the composition is applied to the entire surface of a substrate that does not have a pattern, and the formed coating film is heated to obtain a metal film, a pattern can be obtained by etching this metal film. The etching method is not particularly limited, and examples include the known subtractive method and semi-additive method.

[0096] The average thickness of the resulting metal film (the pattern or coating formed from the composition) is not particularly limited and can be determined as appropriate. The lower limit of the average thickness of the metal film is preferably 1 nm, more preferably 5 nm, and even more preferably 10 nm. The upper limit of the average thickness is preferably 10,000 nm, more preferably 7,000 nm, and even more preferably 5,000 nm. The average thickness of the metal film can be determined by observing a cross-section with a scanning electron microscope, measuring the film thickness at three arbitrary points, and calculating the average of these film thicknesses. [Examples]

[0097] The following describes some examples. It should be noted that the following examples are representative examples of the present invention and should not be interpreted as narrowing the scope of the invention.

[0098] <Preparation of Compositions for Manufacturing Metasurface Reflectors> The following describes the [A] metal compound, [B] nitrogen-containing organic compound, and [C] solvent used in the preparation of the composition for manufacturing metasurface reflectors (composition).

[0099] [[A] Metal compound] A-1: Copper(II) formate dihydrate A-2: Copper(II) acetate tetrahydrate A-3: Copper(II) sulfate pentahydrate A-4: Copper(II) nitrate trihydrate

[0100] [[B]Nitrogen-containing organic compounds] B-1: Compound represented by the following formula (B-1) B-2: Compound represented by the following formula (B-2) B-3: Compound represented by the following formula (B-3) B-4: Compound represented by the following formula (B-4) B-5: Compound represented by the following formula (B-5) B-6: Compound represented by the following formula (B-6) B-7: Compound represented by the following formula (B-7) B-8: Compound represented by the following formula (B-8) B-9: Compound represented by the following formula (B-9)

[0101] [ka]

[0102] [[C] Solvent] C-1: Propylene glycol monoethyl ether C-2: Propylene glycol C-3: Butanol

[0103] [Example 1-1] Preparation of composition (J-1) [A] (A-1) (molar ratio 0.3) and (A-2) (molar ratio 0.7) as metal compounds, and [C] (C-1) as a solvent were mixed in a ratio such that the mass concentration of metal atoms in [A] metal compounds was 4% by mass. Next, [B] (B-6) (molar ratio 2.0) as a nitrogen-containing organic compound was mixed in, and the resulting solution was filtered through a nylon syringe filter with a pore size of 0.2 μm to prepare composition (J-1).

[0104] [Examples 1-2 to 1-18, Comparative Example 1-1] Preparation of compositions (J-2) to (J-18) and composition (j-1) Compositions (J-2) to (J-18) of Examples 1-2 to 1-18 and composition (j-1) of Comparative Example 1-1 were prepared in the same manner as in Example 1-1, except that the types and amounts of each component shown in Table 1 below were used. In the table, "-" indicates that the component was not used.

[0105] [Table 1]

[0106] <Formation of a metal film> [Examples 2-1 to 2-18 and Comparative Example 2-2] Copper film formation by coating The prepared compositions (J-1) to (J-18) and (j-1) were coated onto a silicon substrate using a spin coater (MS-B200 from Mikasa Corporation) at 1,500 rpm for 30 seconds by rotary coating. The resulting coated film was heated in a nitrogen atmosphere at 300°C for 10 minutes and cooled at 23°C for 60 seconds in an RTA furnace (QHC-P610CP from ULVAC, Inc.) to obtain a silicon substrate with a metal film (copper film) having an average thickness of 400 nm.

[0107] [Comparative Example 2-1] Copper film deposition by sputtering A silicon substrate was obtained by sputtering copper onto it using a sputtering apparatus (L-440S-FHL type, manufactured by Canon Anelva Corporation) to form a metal film (copper film) with an average thickness of 400 nm.

[0108] [Reference example] A gold-coated substrate (manufactured by Waki ​​Research Institute Co., Ltd.) was prepared, in which gold was deposited onto a silicon substrate with an average thickness of 100 nm.

[0109] <Rating 1> The copper films formed in Examples 2-1 to 2-18 and Comparative Examples 2-1 to 2-2 were evaluated by the following method. The evaluation results are shown in Table 2 below.

[0110] [Reflectance in the terahertz band] The reflectivity in the terahertz wave region was measured for each substrate coated with either a copper or gold film. A terahertz light sampling and analysis system (Advantest "TAS7400TS") was used for the measurements. The total number of cumulative measurements was 1024, and the measurements were performed in a sample chamber with a continuous supply of dry air to mitigate the effects of atmospheric moisture. When the sample chamber was opened, measurements were performed after at least 4 minutes had elapsed. For each substrate with a copper film in the examples and comparative examples, the reflectance at a specific wavelength was calculated relative to the reflectance of the substrate with a gold film in the reference example (100%). If the reflectance (relative value) was greater than 95% and 100% or less, it was classified as A; if it was greater than 90% and 95% or less, it was classified as B; and if it was 90% or less, it was classified as C.

[0111] [Table 2]

[0112] The results in Table 2 show that the copper films formed from each composition in the examples exhibited a similarly high reflectivity compared to the copper film formed by sputtering in Comparative Example 2-1.

[0113] <Formation of a metal film> [Examples 2-19 to 2-20] Copper film formation by coating Using the prepared compositions (J-3) and (J-13), a silicon substrate with a metal film (copper film) was obtained in the same manner as in Example 2-1, except that the heating temperature was set to 200°C.

[0114] <Rating 2> The copper films formed in Examples 2-19 and 2-20 were evaluated using the method described in "Reflectance in the Terahertz Band" above. The evaluation results are shown in Table 3 below. The results for Examples 2-3 and 2-20 are also shown in Table 3.

[0115] [Table 3]

[0116] The results in Table 3 show that, depending on the type of nitrogen-containing organic compound (B), a copper film with higher reflectivity was obtained by increasing the heating temperature. However, when using nitrogen-containing organic compound (B-5), a copper film with high reflectivity was obtained even at a relatively low heating temperature. It is thought that when the interaction between the nitrogen-containing organic compound (B) and the metal ions (copper ions) of the metal compound (A) is small, or when the nitrogen-containing organic compound (B) has a low molecular weight and a low boiling point, a copper film with high reflectivity can be obtained even at a relatively low heating temperature, as the nitrogen-containing organic compound (B) is less likely to remain.

[0117] <Formation of a metal film> [Example 2-21] Copper film formation by coating A silicon substrate with a metal film (copper film) was obtained in the same manner as in Example 2-1, except that the coating conditions were changed to obtain a metal film (copper film) with an average thickness of 200 nm using the prepared composition (J-3).

[0118] <Rating 3> [Reflectance in the near-infrared region] The reflectance in the near-infrared region was measured on a substrate provided with the copper film obtained in Example 2-21. A JASCO "V-7200" was used for the measurement. The average reflectance in the near-infrared region (wavelength 800-1200 nm) was 84%. The inventors have found that the reflectance in the near-infrared region of pure copper films formed by sputtering, etc., is 90% or more. The copper film formed by the composition of the example tended to have lower reflectance in the near-infrared region compared to the pure copper film formed by sputtering. The effect that the copper film formed by the composition of the example has a reflectance as high as that of a copper film formed by sputtering is a particularly noticeable effect in the case of electromagnetic waves with frequencies in the terahertz region. [Explanation of symbols]

[0119] 10, 20 Metasurface reflectors 11 circuit boards 11a Main board 11b Pattern 12 Coating 21 circuit boards 22 patterns

Claims

1. Used for forming patterns on metasurface reflectors or coatings of the above patterns, It contains metal compounds, nitrogen-containing organic compounds, and solvents. A composition for manufacturing a metasurface reflector, wherein the above-mentioned metal compound is at least one selected from the group consisting of metal salts and metal complexes.

2. The composition for manufacturing a metasurface reflector according to claim 1, wherein the above-mentioned metal compound is a copper compound.

3. The composition for manufacturing a metasurface reflector according to claim 1 or claim 2, wherein the nitrogen-containing organic compound has at least one group selected from the group consisting of a hydroxyl group and an amino group.

4. The composition for manufacturing a metasurface reflector according to claim 1 or claim 2, wherein the molecular weight of the nitrogen-containing organic compound is 200 or less.

5. The composition for manufacturing a metasurface reflector according to claim 1 or claim 2, wherein the solvent is at least one selected from the group consisting of monoalcohol-based solvents, polyhydric alcohol-based solvents, and polyhydric alcohol partial ether-based solvents.

6. The composition for manufacturing a metasurface reflector according to claim 1 or claim 2, wherein the content of the nitrogen-containing organic compound is 0.5 moles or more and 5.0 moles or less per 1.0 mole of the metal compound.

7. A composition for manufacturing a metasurface reflector according to claim 1 or claim 2, used in the manufacture of a metasurface reflector for electromagnetic waves having frequencies in the terahertz region.

8. A step of directly or indirectly coating a substrate having a pattern or not having a pattern with a composition for manufacturing a metasurface reflector, A step of heating the coating film formed by the above coating process and Equipped with, The above-mentioned composition for manufacturing a metasurface reflector contains a metal compound, a nitrogen-containing organic compound, and a solvent. A method for producing a metasurface reflector, wherein the above-mentioned metal compound is at least one selected from the group consisting of metal salts and metal complexes.

9. The method for manufacturing a metasurface reflector according to claim 8, wherein the heating temperature in the above heating step is 150°C or more and 500°C or less.

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