JP7528593B2 - Laminate and carbon nanotube resin composition - Google Patents

Description

The present invention relates to a laminate and a carbon nanotube resin composition that have excellent shading and design properties.

In fields where high design quality is required, such as automobile bodies, coatings using photoluminescent paints containing photoluminescent pigments are required, and there is a demand for a high-quality appearance with high shading properties, etc.

Shading is a type of phenomenon in which brightness changes depending on the viewing angle (angle dependency), and is a phenomenon in which a sense of depth is felt due to angle dependency. In general, a method of expressing angle dependency is, for example, a method of incorporating a luster pigment containing flat metal pieces into the coating film. The flat metal pieces incorporated in the coating film are arranged almost parallel to the surface of the coating film, and the metal pieces in the coating film reflect the light that enters the coating film. During the reflection, the phase of the light shifts depending on the angle of incidence, and the phase-shifted lights interfere with each other, so the amount of light that exits changes. Here, the angle of incidence and exit of light are determined by the angle at which the coating film is viewed, so the amount of light that reaches the eye changes depending on the angle at which the coating film is viewed. In this way, when the amount of light that reaches the eye changes, the color tone of the coating film is observed to change. In particular, when the coating film is colored, the hue may be observed to change depending on the amount of light, and depending on the hue, the shading may have a significant effect on the design.

In recent years, multi-layer coatings with excellent design qualities, including high saturation, high brightness and depth of color, have become known for use in automobile coatings. These coatings are made by laminating a transparent coating (color clear coating) containing color pigments onto a coating (metallic base coating) containing a lustrous material. The appearance of these design qualities is thought to be due to the synergistic effect of the light reflecting effect of the metallic base layer containing the lustrous material and the coloring effect of the color clear layer.

Patent Document 1 claims that by setting the lightness L* value of the metallic base layer containing the lustrous material and the transmittance of the color clear layer within a specific range, a multi-layer coating film with excellent vividness and depth can be obtained.

However, because this multi-layer coating uses the same color for both the metallic base coating and the color clear coating, although it is vivid, it lacks depth.

Patent Document 2 also claims that a highly jet-black laminate can be obtained by using a black pigment in the metallic base layer and carbon nanotubes in the color clear layer. In this case, the metallic base layer is a black coating, so the shading effect is not seen.

JP 2007-167720 A JP 2017-030322 A

The present invention has been made in consideration of the above problems, and an object of the present invention is to provide a laminate that exhibits excellent shading without impairing saturation, and a method for producing the same.

After extensive research, the inventors discovered that the above problems could be solved in the following manner, and thus completed the present invention.

That is, the present invention relates to a laminate having at least two layers, a first layer and a second layer, wherein one or both of the first layer and the second layer contain a luster pigment, the first layer contains a coloring pigment, and the second layer contains carbon nanotubes, and wherein the laminate is formed on the first layer and has an L ^* of 30.0 or more in the L ^* a ^* b ^* color system defined in JIS Z8729 at an offset angle of 15° from the specular reflected light of light incident at an angle of 45° to the perpendicular direction of the laminated surface.

The present invention also relates to the laminate, characterized in that the outer diameter of the short axis side of the carbon nanotubes contained in the second layer is 1 to 9 nm, and the length of the long axis side is 5 to 500 μm.

The present invention also relates to the laminate, characterized in that the second layer has a transmittance of 70 to 95%.

The present invention also relates to the laminate, wherein the second layer is a layer formed by wet coating.

The present invention also relates to the laminate, characterized in that the thickness of the second layer is 0.5 μm or more and 20 μm or less.

The present invention also relates to the laminate, wherein the first layer is a layer formed by wet coating.

The present invention also relates to a carbon nanotube resin composition for forming the second layer of the laminate.

The present invention makes it possible to obtain a laminate with excellent shading and a highly designable structure, as well as a method for producing the same.

FIG. 1 is a diagram showing the configuration of a laminate according to an embodiment.

The following describes in detail an embodiment of the present invention with reference to the drawings. The "resin composition" below refers to a coating material for forming the first layer and the second layer, and the resin composition for forming the first layer is referred to as the "resin composition for forming the first layer," and the resin composition for forming the second layer is referred to as the "resin composition for forming the second layer." The "layer" refers to a molded body or coating film formed from the resin composition.

<Resin composition for forming first layer>
The resin composition for forming the first layer contains a color pigment and a resin that plays a role in forming the layer as essential components, and may contain a glittering pigment, a wax, and a solvent as necessary. However, the glittering pigment is The resin composition for forming the first layer and/or the resin composition for forming the second layer must contain the above-mentioned additive. Furthermore, additives such as a dispersant may be added as necessary. The method for producing the resin composition is not particularly limited, and may be performed using a paint shaker (manufactured by Red Devil Co., Ltd.), a ball mill, a sand mill (such as "Dyno Mill" manufactured by Shinmaru Enterprises Co., Ltd.), an attritor, a pearl mill (such as "DCP Mill" manufactured by Eirich Co., Ltd., etc. ), Coball mill, basket mill, homomixer, homogenizer (M Technique's "Clearmix", etc.), wet jet mill (Genus's "Genus PY", Nanomizer's "Nanomizer", etc.), Huber Muller, 3 units It is preferable to carry out the dispersion treatment using a roll mill, an extruder (twin-screw extruder), a Henschel mixer, or the like.

A high-speed mixer can also be used to obtain the resin composition for forming the first layer. Examples of high-speed mixers include Homo Disper (manufactured by PRIMIX), Filmix (manufactured by PRIMIX), Dissolver (manufactured by Inoue Seisakusho), and Hyper HS (manufactured by Ashizawa Finetech).

Color pigments are pigments used to color paints, rust-preventive paints, plastics, synthetic fibers, rubber products, etc. Examples of color pigments include inorganic color pigments such as titanium dioxide, iron oxide, and yellow iron oxide, and organic color pigments such as phthalocyanine blue, phthalocyanine green, carbazole violet, anthrapyridine, azo orange, flavanthrone yellow, isoindoline yellow, azo yellow, industhrone blue, perylene red, azo red, anthraquinone red, quinacridone red, and diketopyrrolopyrrole. These color pigments can be used alone or in combination of two or more.

The resin, which is an essential component used in the resin composition for forming the first layer, is not particularly limited as long as it is normally used as a binder resin for paints, and can be appropriately selected according to the purpose. Examples of the resin include condensation synthetic resins, addition synthetic resins, and natural polymer compounds. Examples of the condensation synthetic resins include polyester resins, polyurethane resins, polyepoxy resins, polyamide resins, polyether resins, and silicon resins. Examples of the addition synthetic resins include polyolefin resins, polystyrene resins, polyvinyl alcohol resins, polyvinyl ester resins, polyacrylic acid resins, and unsaturated carboxylic acid resins. Examples of the natural polymer compounds include celluloses, rosins, and natural rubber. The resins may be used as homopolymers or as copolymers to be used as composite resins. Any of single-phase structure type, core-shell type, and power feed type emulsions can be used.

Specific examples of such resins include acrylic resins from DIC Corporation (trade name "Acrydic" (registered trademark) series, etc.), Taisei Fine Chemical Co., Ltd. (trade name "Acryt" (registered trademark) series, etc.), Nippon Shokubai Co., Ltd. (trade name "Acryset" (registered trademark) series, etc.), and Mitsui Chemicals, Inc. (trade name "Takelac" (registered trademark) UA series). Polyester resins include DIC Corporation (trade name "Polylite" (registered trademark) series, etc.), Kuraray Co., Ltd. (trade name "Kuraray Polyol" (registered trademark) series, etc.), and Takeda Pharmaceutical Co., Ltd. (trade name "Takelac" (registered trademark) U series). Polyolefin resins include Nippon Soda Co., Ltd. (trade name "NISSO-PB" (registered trademark) G series, etc.), and Idemitsu Kosan Co., Ltd. (trade name "Poly bd" (registered trademark) series, "Epol" (registered trademark) series, etc.), and these products can be used.

The resin composition for forming the first layer of the present invention can use melamine resin, urea resin, polyisocyanate compound, blocked polyisocyanate compound, epoxy compound or resin, carboxyl group-containing compound or resin, acid anhydride, alkoxysilane group-containing compound or resin, etc., which act as a crosslinking agent capable of reacting with the functional group of the resin. It is desirable to use a resin containing a crosslinkable functional group in combination with a resin which acts as a crosslinking agent, and among these, it is preferable to use one selected from acrylic resin, polyester resin, alkyd resin, melamine resin, epoxy resin, and urea resin, it is more preferable to use one selected from acrylic resin, polyester resin, alkyd resin, and melamine resin, and it is more preferable to use a combination of acrylic resin and melamine resin.

Melamine resins are particularly preferred because they are thermosetting and act as a curing agent. The acrylic resin is preferably one obtained by polymerizing a monomer having a polymerizable unsaturated double bond by a conventional method, which is well known to those skilled in the art. Examples of the monomer having a polymerizable unsaturated double bond include carboxylic acid group-containing monomers such as acrylic acid, methacrylic acid, crotonic acid, isocrotonic acid, ethacrylic acid, propylacrylic acid, isopropylacrylic acid, itaconic acid, maleic anhydride, and fumaric acid, hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and ε-caprolactone-modified acrylic monomers, methyl (meth)acrylate, ethyl (meth)acrylate, and (meth) Examples of the monomers include (meth)acrylic acid ester monomers such as propyl acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, and stearyl (meth)acrylate; and styrene monomers such as styrene, α-methylstyrene, α-methylstyrene dimer, vinyltoluene, and divinylbenzene. In addition, it is preferable to use a radical polymerization initiator well known to those skilled in the art for the polymerization.

Specific examples of melamine resins include methyl etherified melamine resins such as Cymel 300, 303, 325, 327, 350, and 370 (manufactured by Mitsui Cytec Co., Ltd.), Nikalac MS15, MS17, MX430, and MX650 (manufactured by Sanwa Chemical Co., Ltd.), Sumimal M-55 (manufactured by Sumitomo Chemical Co., Ltd.), and Resimin 740 and 741 (manufactured by Monsanto Co., Ltd.); and methyl ether-butyl ether mixed etherified melamine resins such as Cymel 202, 235, 238, 254, 272, and 1130 (manufactured by Mitsui Cytec Co., Ltd.), Nikalac MX485 and MX487 (manufactured by Sanwa Chemical Co., Ltd.), and Resimin 755 (manufactured by Monsanto Co., Ltd.). These melamine resins can be used alone or as a mixture of two or more kinds.

Examples of polyisocyanate compounds include phenylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, bisphenylene diisocyanate, naphthylene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, cyclopentylene diisocyanate, cyclohexylene diisocyanate, methylcyclohexylene diisocyanate, dicyclohexylmethane diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, propylene diisocyanate, ethylethylene diisocyanate, and trimethylhexane diisocyanate.

In addition, a UV-curable resin can be used to obtain the resin composition for forming the first layer. Representative examples include unsaturated acrylic compounds, polyvinyl cinnamates, azide resins, and the like. Examples of unsaturated acrylic compounds include monomers, oligomers, or mixtures thereof having one or several acrylic or methacrylic unsaturated groups, such as propylene (or butylene, ethylene) glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, and other monomers or oligoesters with a molecular weight of 10,000 or less. Specific examples include special acrylates (bifunctional) Aronix M-210, Aronix M-215, Aronix M-220, Aronix M-233, Aronix M-240, and Aronix M-245; (trifunctional) Aronix M-305, Aronix M-309, Aronix M-310, Aronix M-315, Aronix M-320, and Aronix M-325; and (multifunctional) Aronix M-400 (manufactured by Toagosei Co., Ltd.).

The luster pigment used in the resin composition for forming the first layer is a general term for pigments that impart a pearl-like or metallic luster, and examples include aluminum flakes, metal oxide-coated alumina flakes, metal oxide-coated silica flakes, graphite pigments, metal oxide-coated mica, titanium flakes, stainless steel flakes, plate-like iron oxide pigments, metal-plated glass flakes, metal oxide-coated glass flakes, holographic pigments, phthalocyanine flakes, and pearls.

The average particle size of the flake-shaped photoluminescent pigment is usually preferably about 5 to 50 μm, more preferably about 5 to 30 μm. The average thickness is usually preferably about 0.1 to 2 μm, more preferably about 0.05 to 1.5 μm. The ratio of the average particle size to the average thickness (average particle size/average thickness) is usually preferably about 5 to 500, more preferably about 20 to 300.

As the dispersant, a surfactant or a resin-type dispersant can be used. Surfactants are mainly classified into anionic, cationic, nonionic, and amphoteric, and the appropriate type and amount can be selected and used depending on the required characteristics. A resin-type dispersant is preferable. These dispersants are not particularly limited, but the following compounds can be given as suitable examples.

Examples of anionic surfactants include fatty acid salts, polysulfonates, polycarboxylates, alkyl sulfates, alkylaryl sulfonates, alkylnaphthalenesulfonates, dialkylsulfonates, dialkylsulfosuccinates, alkyl phosphates, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkylaryl ether sulfates, naphthalenesulfonate formalin condensates, polyoxyethylene alkyl phosphate sulfonates, glycerol borate fatty acid esters, polyoxyethylene glycerol fatty acid esters, etc. Specific examples include sodium dodecylbenzenesulfonate, sodium laurate sulfate, sodium polyoxyethylene lauryl ether sulfate, polyoxyethylene nonylphenyl ether sulfate, sodium salt of β-naphthalenesulfonate formalin condensates, etc.

Cationic surfactants include alkylamine salts and quaternary ammonium salts, such as stearylamine acetate, trimethyl coconut ammonium chloride, trimethyl beef tallow ammonium chloride, dimethyldioleyl ammonium chloride, methyl oleyl diethanol chloride, tetramethyl ammonium chloride, lauryl pyridinium chloride, lauryl pyridinium bromide, lauryl pyridinium disulfate, cetyl pyridinium bromide, 4-alkyl mercaptopyridine, poly(vinylpyridine)-dodecyl bromide, and dodecylbenzyl triethyl ammonium chloride. Amphoteric surfactants include amino carboxylates.

Nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyalkylene derivatives, polyoxyethylene phenyl ethers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, alkyl allyl ethers, etc., and more specifically, polyoxyethylene lauryl ethers, sorbitan fatty acid esters, polyoxyethylene octylphenyl ethers, etc.

The surfactant is not limited to one type, and it is possible to use two or more types of surfactants in combination, such as an anionic surfactant and a nonionic surfactant, or a cationic surfactant and a nonionic surfactant. In this case, the amount of each active agent component is preferably the amount described above. It is preferable to use an anionic surfactant and a nonionic surfactant in combination. The anionic surfactant is preferably a polycarboxylate, and the nonionic surfactant is preferably polyoxyethylene phenyl ether.

Resin-type dispersants include polyurethanes; polycarboxylates such as polyacrylates; unsaturated polyamides, polycarboxylic acids, polycarboxylate (partial) amine salts, polycarboxylate ammonium salts, polycarboxylate alkylamine salts, polysiloxanes, long-chain polyaminoamide phosphates, hydroxyl-containing polycarboxylates, and modified products thereof; oil-based dispersants such as amides formed by the reaction of poly(lower alkylene imines) with polyesters having free carboxyl groups, and salts thereof; water-soluble resins and water-soluble polymeric compounds such as (meth)acrylic acid-styrene copolymers, (meth)acrylic acid-(meth)acrylic acid ester copolymers, styrene-maleic acid copolymers, polyvinyl alcohol, and polyvinylpyrrolidone; polyester resins, modified polyacrylate resins, ethylene oxide/propylene oxide adducts, and phosphate resins. Resin-type dispersants can be used alone or in combination of two or more. (Meth)acrylic acid means acrylic acid and methacrylic acid.

Among the above dispersants, resin-type dispersants having an acidic functional group such as polycarboxylic acid are preferred because even a small amount added reduces the viscosity of the dispersion composition and shows high spectral transmittance. Resin-type dispersants play an auxiliary role in dispersing the pigment, and are preferably used in an amount of about 3 to 300% by mass relative to the carbon nanotubes, and more preferably about 5 to 100% by mass from the viewpoint of film-forming properties.

Commercially available resin-type dispersants include Disperbyk-101, 103, 107, 108, 110, 111, 116, 130, 140, 154, 161, 162, 163, 164, 165, 166, 170, 171, 174, 180, 181, 182, 183, 184, 185, 190, 2000, 2001, 2020, 2025, 2050, 2070, 2095, 2150, 2155, or Ant i-Terra-U, 203, 204, or BYK-P104, P104S, 220S, 6919, or Lactimon, Lactimon-WS, or Bykumen, etc.; SOLSPERSE-3000, 9000, 13000, 13240, 13650, 13940, 16000, 17000, 18000, 20000, 21000, 24000, 26000, 27000, 280 manufactured by Lubrizol Japan Co., Ltd. EFKA-46, 47, 48, 452, 4008, 4009, 4010, 4015, 4020, 4047, 4050, 4055, 4060, 4080, 4400, 4401, 4402, etc., manufactured by BASF Japan Ltd. , 4403, 4406, 4408, 4300, 4310, 4320, 4330, 4340, 450, 451, 453, 4540, 4550, 4560, 4800, 5010, 5065, 5066, 5070, 7500, 7554, 1101, 120, 150, 1501, 1502, 1503, etc.; Ajisper PA111, PB711, PB821, PB822, PB824, etc. manufactured by Ajinomoto Fine-Techno Co., Ltd.

The wax used in the resin composition for forming the first layer is not particularly limited, but examples include polyethylene wax, polypropylene wax, sazol wax, montan wax, paraffin wax, microcrystalline wax, carnauba wax, and shellac wax. One or more types of wax may be used. Among these, polyethylene wax or polypropylene wax is more preferred.

The solvent used as necessary in the resin composition for forming the first layer is not particularly limited, and either water or an organic solvent can be used.
From the viewpoint of workability during coating and drying before and after curing, an organic solvent having a boiling point of 50 to 250° C. is preferred. Specific examples of the solvent include alcohol-based solvents such as methanol, ethanol, and isopropyl alcohol; ketone-based solvents such as acetone, butyl diglycol acetate, and MEK; ester-based solvents such as ethyl acetate, butyl acetate, and ethyl 3-ethoxypropionate (EEP); ether-based solvents such as dibutyl ether, ethylene glycol, and monobutyl ether; aromatic solvents such as toluene, xylene, and Solvesso 150 (manufactured by Tonen General Sekiyu KK); and aprotic polar solvents such as N-methyl-2-pyrrolidone. These solvents can be used alone or in combination of two or more.

Additionally, the resin composition for forming the first layer may contain additives such as pigments, wetting and penetrating agents, antiskinning agents, UV absorbers, antioxidants, crosslinking agents, preservatives, antifungal agents, viscosity adjusters, pH adjusters, leveling agents, and defoamers, as necessary, within the scope of not impairing the object of the present invention.

<First Layer>
The first layer is a layer formed from a resin composition for forming the first layer, and contains a color pigment and a resin. The first layer may be called a color base layer. A substrate layer may be provided below the first layer.

The content of the color pigment is preferably 50% by mass or less, and more preferably 30% by mass or less. Within this range, excellent shading properties can be obtained.

The material of the substrate is not particularly limited, and examples thereof include metals such as iron, aluminum, copper, or alloys thereof; inorganic materials such as glass, cement, and concrete; resins such as polyethylene resin, polypropylene resin, ethylene-vinyl acetate copolymer resin, polyamide resin, acrylic resin, vinylidene chloride resin, polycarbonate resin, polyurethane resin, polyester resin, and epoxy resin; plastic materials such as FRP, and natural or synthetic materials such as wood and fiber materials (paper, cloth, etc.). The substrate may be in the form of, for example, a film or sheet.

The method for forming the first layer can be selected optimally depending on the properties of the resin composition used and the substrate on which the layer is formed, and examples of such methods include dry methods such as heat curing, vacuum deposition, EB deposition, and sputter deposition; wet coating methods such as casting, spin coating, dip coating, bar coating, spraying, blade coating, slit die coating, gravure coating, reverse coating, screen printing, mold coating, print transfer, and inkjet; and general methods such as injection molding, injection compression molding, extrusion molding, and blow molding.

The thickness of the first layer is preferably 0.5 μm or more, and more preferably 1 μm or more. Furthermore, it is preferably 50 μm or less. If it is 0.5 μm or more, sufficient hiding power is obtained. If it is 50 μm or less, it has excellent practical properties such as curing speed.

<Resin composition for forming second layer>
To obtain the resin composition for forming the second layer, at least carbon nanotubes and a resin are used. If necessary, a luster pigment and a solvent may be added. Furthermore, if necessary, additives such as a dispersant may be added. The method for producing the resin composition for forming the second layer is not particularly limited. Suitable production methods include the same methods as those for the resin composition for forming the first layer described above.

The carbon nanotubes used in the resin composition for forming the second layer have a cylindrical shape made of planar graphite. The carbon nanotubes may be single-walled carbon nanotubes (SWCNT) having a structure in which one graphite layer is wound, multi-walled carbon nanotubes (MWCNT) having two or more layers of wound carbon nanotubes, or a mixture of these. Multi-walled carbon nanotubes (MWCNT) are preferred in terms of cost and coloring effect. Also, the carbon nanotubes may have an amorphous structure rather than a graphite structure on the sidewall.

The shape of the carbon nanotube is not particularly limited, but examples include needle-like, cylindrical tube-like, fishbone-like (fishbone or cup-stacked type), playing card-like (platelet), and coil-like shapes. Examples of carbon nanotubes include graphite whiskers, filamentous carbon, graphite fibers, ultrafine carbon tubes, carbon tubes, carbon fibrils, carbon microtubes, and carbon nanofibers. Carbon nanotubes can be used in the form of one type or a combination of two or more types.

In the present invention, it is preferable to use carbon nanotubes other than those shaped like fishbone (fishbone, cup stacked type), playing card (platelet), or coil. In the case of the fishbone or playing card shape, the shear stress generated during the production of the resin composition and molded product causes the carbon nanotubes to break on the stacking plane (x-y plane) of the cup/playing card shaped graphite sheet. This prevents the carbon nanotubes from forming a sufficient network structure in the resin, which may reduce the light trapping effect and lead to a decrease in blackness. Similarly, in the case of the coil shape, the three-dimensional structure is easily destroyed during production, which may reduce the coloring effect.

From the viewpoint of ease of dispersion and hue, the outer diameter of the short axis side of the carbon nanotube is preferably 1 to 30 nm, more preferably 1 to 10 nm, and more preferably 1 to 9 nm. Within this range, excellent shading can be obtained. The outer diameter of the carbon nanotube was determined by observing the shape of the carbon nanotube using a transmission electron microscope (manufactured by JEOL Ltd.), measuring the length of the short axis of 100 tubes, and taking the number average value as the outer diameter (nm) of the carbon nanotube.

From the viewpoint of ease of dispersion and color, the length of the long axis side of the carbon nanotube is preferably 0.1 μm or more, and more preferably 5 μm or more. Also, it is preferably 1000 μm or less, and more preferably 500 μm or less. The length of the carbon nanotube was measured by observing the shape of the carbon nanotube using a transmission electron microscope (manufactured by JEOL Ltd.), measuring the long axis length of 100 tubes, and taking the number average value as the length of the carbon nanotube (μm).

The carbon purity of the carbon nanotubes is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, based on 100% by mass of the carbon nanotubes.

Carbon nanotubes usually exist as secondary particles. The shape of these secondary particles may be, for example, a complex entanglement of carbon nanotubes, which are typical primary particles, or an aggregate of linear carbon nanotubes that are easy to disentangle. Secondary particles that are an aggregate of linear carbon nanotubes are preferred because they have better dispersibility than entangled particles.

The carbon nanotubes may be surface-treated or may be carbon nanotube derivatives to which functional groups such as carboxyl groups have been added. Carbon nanotubes that encapsulate organic compounds, metal atoms, fullerenes, etc. may also be used.

The luster pigment used in the resin composition for forming the second layer may be the same as the luster pigment used in the resin composition for forming the first layer.

The resin used in the resin composition for forming the second layer is not particularly limited as long as it does not deviate from the spirit of the present invention, but suitable examples include the resins exemplified in the resin composition for forming the first layer.

In particular, a two-component clear coating (e.g., a two-component curing urethane coating) using, for example, a polyol resin containing hydroxyl groups as the base material and an isocyanate as the curing agent is preferred. This is because the clear coating film obtained has a good appearance and excellent acid resistance. There are no particular limitations on the polyol resin used as the base material and the isocyanate used as the curing agent, but examples include the compounds described in the explanation of the resin of the resin composition for forming the first layer.

The dispersant used in the resin composition for forming the second layer is not particularly limited as long as it does not deviate from the spirit of the present invention, but suitable examples include the compounds exemplified in the resin composition for forming the first layer.

The solvent used in the resin composition for forming the second layer is not particularly limited, and either water or an organic solvent can be used. Examples of organic solvents include the same organic solvents as those used in the resin composition for forming the first layer.

The resin composition for forming the second layer may further contain UV absorbers, light stabilizers, surface conditioners, etc., as necessary, and may also contain color pigments, metallic pigments, and interference pigments such as mica, to the extent that the transparency of the coating film is not impaired.

<Second Layer>
The second layer is a layer obtained by using a resin composition for forming the second layer, and contains carbon nanotubes. The second layer is sometimes called a color clear layer. It is presumed that the effect of the present invention is that the carbon nanotubes contained in the second layer are oriented to improve shading.

The method for forming the second layer on the first layer can be selected from the most suitable methods depending on the material to be formed, and includes common methods such as dry methods such as heat curing, vacuum deposition, EB deposition, and sputter deposition, and wet coating methods such as casting, spin coating, dip coating, bar coating, spraying, blade coating, slit die coating, gravure coating, reverse coating, screen printing, mold coating, print transfer, and inkjet. The second layer may also be a laminate of a film that has already been formed, and these layers do not necessarily need to be in close contact with each other.

The thickness of the second layer is preferably 0.5 μm or more, and more preferably 1 μm or more. Furthermore, it is preferably 50 μm or less, and more preferably 20 μm or less. If it is 0.5 μm or more, the carbon nanotubes in the second layer are efficiently oriented, and excellent shading is obtained. If it is 50 μm or less, the second layer does not completely block the incident light, and the effect of the laminate is sufficiently obtained.

The carbon nanotube content of the second layer is preferably 0.01% to 1%, more preferably 0.01% to 0.5%, and even more preferably 0.01% to 0.1%. Within this range, a laminate with high shading can be obtained without impairing saturation.

The transmittance of the second layer is preferably 70% or more, and more preferably 80% or more. Also, it is preferably 98% or less, and more preferably 95% or less. If it is within this range, a laminate with high shading properties can be obtained without impairing color saturation.

<Laminate>
The laminate of the present invention is composed of at least two layers, a first layer and a second layer. Another layer may be provided between the first layer and the second layer without departing from the spirit of the present invention. In addition, it is preferable that a transparent protective layer or the like is provided on the second layer from the viewpoint of weather resistance and durability.

When applying the laminate to automobile bodies and automobile parts, it is preferable to apply a primer coat, intermediate coat, etc., using chemical conversion treatment, electrocoating, etc., to the area where the laminate is to be formed. This intermediate coat forms a coating film to conceal the base, impart chipping resistance, and ensure adhesion with the first layer, which is the top coat.

In the method for forming the laminate of the present invention, either a method in which a second layer is formed after the formation of a first layer but before heat curing, and then the coating film is heat cured all at once (wet-on-wet method), or a method in which a first layer is formed, heat cured, and then a second layer is formed and heat cured (wet-on-dry method) can be used.

The laminate of the present invention has an L* of 30.0 or more, and more preferably 45.0 or more, in the L ^* a ^* b ^* color system defined in JIS Z8729 at an offset angle of 15 ^° from the regular reflection of light incident at an angle of 45° to the normal direction of the laminated surface.

The present invention is not limited to the above-described embodiment, and it goes without saying that other embodiments may also fall within the scope of the present invention as long as they are consistent with the spirit of the present invention.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Note that in the examples, "%" refers to "% by mass."

<Example of preparation of resin composition for forming first layer>

(Preparation Example 1)
(First layer forming resin composition A-1)
10.0 g of red pigment (BASF, Paliogen Maroon L3920), 133.3 g of acrylic resin (DIC, Acrydic 57-773) as resin, and 74.0 g of a mixed solvent of toluene: xylene: butyl acetate: Solvesso 150 (Tonen General) in a mass ratio of 3: 3: 2: 2 were added as a solvent to disperse the pigment so that the coarse particles were 5 μm or less, and then 66.7 g of melamine resin (DIC, Amidia L-177-60) as a curing agent and 8.0 g of aluminum paste (Toyo Aluminum, Alpaste 5422NS, aluminum content 75%) as a glittering pigment were added and stirred with a tabletop stirrer until uniform. The viscosity of this was adjusted to a coating viscosity to obtain a first layer forming composition A-1.

(Preparation Examples 2 to 4)
First layer forming compositions A-2 to A-4 were obtained in the same manner as in Preparation Example 1, except that the pigment species shown in Table 1 were used instead.

<Preparation Example of Resin Composition for Forming Second Layer>
(Preparation Example 5)
0.1 g of carbon nanotubes (K-nanos 100T, Kumho Petrochemical Co., Ltd.), 133.3 g of acrylic resin (DIC Corporation, Acrydic 57-773) as resin, and 74.0 g of a mixed solvent of toluene: xylene: butyl acetate: Tonen General KK Solvesso 150 in a mass ratio of 3: 3: 2: 2 as solvent were added to disperse the pigment so that the coarse particles were 5 μm or less, and then 66.7 g of melamine resin (DIC Corporation, Amidia L-177-60) as a curing agent and 8.0 g of aluminum paste (Toyo Aluminum Co., Ltd., Alpaste 5422NS, aluminum content 75%) as a glittering pigment were added and stirred with a tabletop stirrer until uniform. The viscosity of this was adjusted to a coating viscosity to obtain a second layer forming composition B-1.

(Preparation Examples 6 to 13)
Compositions for forming second layers B-2 to B-13 were obtained in the same manner as in Preparation Example 5, except that the pigment types and amounts added were changed as shown in Table 2.

The abbreviations shown in Tables 1 and 2 have the following meanings.
Paliogen Maroon L3920: BASF, red pigment; LIONOL BLUE FG7351: Toyo Color, blue pigment; Hostaperm Violet RL-NF: Clariant, purple pigment; K-nanos 100T: Kumho Petrochemical, carbon nanotube, outer diameter 13 nm, length 30 μm
NC-7000: Nanosil, carbon nanotube, outer diameter 9.5 nm, length 1.5 μm
JENOTUBE 8S: Carbon nanotube manufactured by JEIO, outer diameter 8 nm, length 150 μm
JENOTUBE 6A: JEIO carbon nanotube: outer diameter 6 nm, length 150 μm
FW200: Degussa, carbon black, outer diameter 13 nm

(Making laminates)

Example 1
A polyethylene terephthalate (PET) film (Lumirror 100, T60, manufactured by Toray Industries, Inc.) was used as a substrate, and the first layer forming paint (A-1) was applied to one side so that the film thickness after drying would be 20 μm, and then dried in an electric oven at 140±5° C. for 20 minutes to prepare a first layer on the substrate. The first layer was wet-coated with the second layer forming resin composition (B-3) using a spray so that the film thickness after drying would be 10 μm, and the resulting coating surface was dried in an electric oven at 140±5° C. for 20 minutes to form a second layer on the first layer, thereby preparing a laminate (C-1).

(Examples 2 to 9, Comparative Examples 1 to 10)
Except for replacing the first layer forming composition and the second layer forming composition shown in Tables 3 and 4, the same preparation as in Example 1 was performed to obtain laminates C-2 to C-9 and comparative laminates C-1 to C-10.

(Method of measuring L ^* a ^* b ^* of first layer)
The composition for forming the first layer was wet-coated onto a PET film using a spray so that the film thickness after drying would be 20 μm, and the resulting coating surface was dried in an electric oven at 140°C ± 5°C for 20 minutes.The test coating film was then measured at offset angles of 15 ^{° and} 110 ^° from the direct reflection light of light incident at an angle of 45° to the perpendicular direction of the laminated surface using an X-Rite multi-angle spectrophotometer MA68II based on the measurement values of the L*a*b* color system specified in JIS Z8729, to obtain color measurement values.

(Transmittance evaluation of the second layer)
The composition for forming the second layer was wet-coated onto a PET film using a spray so that the film thickness after drying would be 10 μm, and the resulting coating surface was dried in an electric oven at 140° C.±5° C. for 20 minutes to form a test coating film. The transmittance of the test coating film was measured using a haze meter (300A) manufactured by Nippon Denshoku Industries Co., Ltd., with the PET film as a reference.

(Method of measuring L ^* a ^* b ^* of laminate)
The laminate was measured based on the measurements of the L ^* a ^* b ^* color system specified in JIS Z8729 using an X-Rite multi-angle spectrophotometer MA68II at offset angles of 15° and 110° from the direct reflection of light incident at an angle of 45° to the perpendicular direction of the laminated surface, to obtain colorimetric values.

(Shading evaluation)
For the first layer and the laminate prepared above, the FF value was determined based on formula (1).
FF value = (L ^* value at 15°) / (L ^* value at 110°) ... Formula (1)
In order to quantify the change in the FF value before and after forming the second layer from the obtained FF value, the FF increase rate was calculated based on formula (2), and shading evaluation was performed according to the following criteria.
FF increase rate (%)=((FF value of laminate)/(FF value of first layer)−1))×100 (2)
Judgment criteria: ◎: 50% or more; ○: 35% or more but less than 50%; △: 20% or more but less than 35%; ×: Less than 20%

The laminate of the present invention, in which the second layer contains carbon nanotubes, has been shown to have superior shading properties compared to laminates in which the second layer contains carbon black, such as Comparative Examples 1, 3, 4, 5, 8, and 10; laminates in which the second layer contains the same color pigment as the first layer, such as Comparative Examples 2, 6, and 9; and laminates in which a transparent clear is provided in the second layer, such as Comparative Example 7.

The laminate of the present invention has high shading and excellent design properties, so it can be used favorably in housing and building materials, automobile bodies, automobile parts, electrical and electronic parts, miscellaneous goods, films, etc. It is particularly suitable as an exterior part that requires high design properties, and is suitable for use in vehicle parts, home appliance parts, furniture parts, office equipment housings, films, etc.

1 First layer 2 Second layer 3 Substrate 10 Laminate

Claims (6)

A laminate having at least two layers, a first layer and a second layer,
a first layer and/or a second layer contains a luster pigment, the first layer contains a color pigment, and the second layer contains carbon nanotubes; the first layer is formed on the first layer, and the second layer has an L* ^of 30.0 or more in the L ^* a ^* b ^* color system defined in JIS Z8729 at an offset angle of 15° from the regular reflection of light incident at an angle of 45° with respect to the perpendicular direction of the laminated surface ;
A laminate comprising carbon nanotubes contained in the second layer, the outer diameter of the minor axis side being 1 to 9 nm and the length of the major axis side being 5 to 500 μm . 2. The laminate according to claim 1, wherein the second layer has a transmittance of 70 to 95%. 3. The laminate according to claim 1 , wherein the second layer has a thickness of 0.5 μm or more and 20 μm or less. A method for producing the laminate according to any one of claims 1 to 3,
A method for producing a laminate, comprising wet-coating a resin composition for forming a second layer onto a first layer to form a second layer. A method for producing the laminate according to any one of claims 1 to 3,
A method for producing a laminate, comprising wet-coating a base layer with a resin composition for forming a first layer to form a first layer. A carbon nanotube resin composition for forming the second layer of the laminate according to any one of claims 1 to 3 .

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