Infrared-reflective black effect pigment

Abstract

To provide an infrared-reflective black effect pigment that achieves high infrared reflectance independent of the influence of the substrate.SOLUTION: An infrared-reflective black effect pigment comprises metallic pigment particles and a black pigment layer covering the metallic pigment particles, the black pigment layer comprising perylene black pigment.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates generally to pigments, and specifically to black effect pigments. [Background technology]

[0002] In recent years, research into autonomous driving technology has been progressing. One of the sensing technologies used in autonomous driving is LiDAR (Light Detection And Ranging), which uses infrared rays. LiDAR senses by detecting infrared rays with a wavelength of 905 nm reflected from the target object.

[0003] Black objects painted with carbon black are difficult to detect with LiDAR because carbon black absorbs infrared light with a wavelength of 905 nm.

[0004] Conventionally, JP 2022-540645 A (Patent Document 1) describes the use of black effect pigments in which a flake-like Al2O3 or SiO2 support is coated with Fe2O3 or FeTiO3 for the purpose of enhancing infrared reflection. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2022-540645 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the black effect pigment described in Patent Document 1 is less likely to absorb infrared rays, but is infrared-transparent, and is therefore affected by the undercoat. In other words, if the substrate or undercoat coated with the black effect pigment described in Patent Document 1 is infrared-absorbing, there is a risk of a decrease in infrared reflectance.

[0007] Therefore, an object of the present invention is to provide an infrared reflective black effect pigment which is capable of obtaining high infrared reflectance without being affected by the undercoat. [Means for solving the problem]

[0008] As a result of extensive research conducted in light of the problems in the prior art, the inventors discovered that the above object can be achieved by coating metal pigment particles with a specified black pigment, thereby completing the present invention.

[0009] That is, the infrared reflective black effect pigment according to the present invention comprises metal pigment particles and a black pigment layer coating the metal pigment particles, the black pigment layer comprising perylene black pigment.

[0010] In this way, it is possible to provide an infrared reflective black effect pigment that is capable of achieving high infrared reflectance without being affected by the base. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The infrared reflective black effect pigment of the present invention will be described in detail below with reference to specific examples. Note that the present invention is not limited to the embodiments shown below, and various modifications are possible within the scope of the technical concept of the present invention.

[0012] (Infrared reflective black effect pigments) The infrared reflective black effect pigment of the present invention comprises a metal pigment particle as a substrate and a black pigment layer covering the metal pigment particle. The black pigment layer contains a perylene black pigment as a black pigment. In the black pigment layer, the black pigment is fixed by any method, but is not limited thereto, and is preferably fixed by a resin or metal oxide described below.

[0013] (Metal Pigment Particles) The metal pigment particles that are the base material of the infrared reflective black effect pigment of the present invention are not particularly limited and known metal pigment particles can be used. Materials for the metal pigment particles include aluminum, gold, silver, copper, zinc, nickel, platinum, iron, and alloys containing these metals. Among them, silver, aluminum, gold, and alloys containing these metals as main components are preferably used because they have high infrared reflectance. In addition, aluminum and aluminum alloys are particularly preferably used because they are inexpensive.

[0014] The particle size of the metal pigment particles is not particularly limited, but in general, any particle with a volume-based median diameter D50 measured by a laser diffraction / scattering method of 1 μm to 200 μm can be suitably used. The shape of the metal pigment particles is not particularly limited, but flake-shaped particles are suitably used. The average thickness of the flake-shaped metal pigment particles is preferably 10 nm to 5 μm.

[0015] The metal pigment particles may be previously surface-treated as necessary, for example, by water-resistant treatment using a compound such as a phosphoric acid compound, molybdenum oxide, tungsten oxide, or vanadium oxide.

[0016] (Black pigment layer) The black pigment layer of the present invention is preferably a layer in which the black pigment covering the metal pigment particles is fixed with a resin, a metal oxide or a composite of both.

[0017] The thickness of the black pigment layer is not particularly limited, but the average thickness on one side is preferably 1 nm or more and 5 μm or less, and more preferably 20 nm or more and 3 μm or less. The average thickness on one side of the black pigment layer can be measured by observing the cross section of the effect pigment using an electron microscope. If it is within this range, it is possible to appropriately balance the blackness and metallic feeling.

[0018] The black pigment layer can be formed by any known method without any particular restrictions. For example, a method is available in which a composite of a carboxylic acid compound and an amine compound is used to adsorb a black pigment onto the surface of metal pigment particles, which is then dispersed in a solvent to form a slurry, and a monomer serving as a raw material for the resin is polymerized in the slurry. When a metal oxide is used, instead of polymerizing a monomer, an organometallic compound serving as a raw material for the metal oxide may be hydrolyzed and condensed. In this way, the resin or metal oxide is formed so as to fill the gaps between the black pigment particles, and can be fixed on the metal pigment particles as a black pigment layer.

[0019] The black pigment layer may contain, in addition to the black pigment, resin, and metal oxide, a compound used for adsorbing the black pigment.

[0020] (Black pigment) The black pigment used in the infrared reflective black effect pigment of the present invention is a perylene black pigment. Perylene black pigments reflect less visible light and absorb less in the infrared wavelength region. In particular, they absorb less in the near infrared wavelength region adjacent to visible light, so they do not interfere with detection by sensors such as LiDAR that use near infrared light.

[0021] (resin) When a resin is used to fix the black pigment in the black pigment layer, the resin is not particularly limited and known resins can be used. In particular, a three-dimensionally crosslinked resin using a monomer having multiple polymerizable functional groups in a part or all of the monomer is preferably used because it has excellent durability and solvent resistance. Examples of such monomers having multiple functional groups include 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol diacrylate, 1,9-nonanediol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, dipentaerythritol hexaacrylate, dipentaerythritol hexamethacrylate, and divinylbenzene. In addition, it is desirable to use a monomer having a polar functional group as an anchor to the metal pigment particles and the black pigment. Such monomers include acrylic acid, fumaric acid, maleic acid, vinylphosphonic acid, 2-methacryloyloxyethyl acid phosphate, 2-(dimethylamino)ethyl acrylate, and the like.

[0022] The amount of the resin is preferably 5 parts by mass or more and 100 parts by mass or less, and more preferably 10 parts by mass or more and 70 parts by mass or less, relative to 100 parts by mass of the black pigment. If it is 5 parts by mass or more, the black pigment layer can be sufficiently fixed, and if it is 100 parts by mass or less, a black color with a metallic feel will be obtained.

[0023] (Metal oxides) When a metal oxide is used to fix the black pigment in the black pigment layer, any known metal oxide can be used without any particular limitation. Examples include oxides of aluminum, silicon, titanium, zirconium, cerium, etc. These oxides may be partially hydroxides or hydrates as long as they do not impair the effects of the present invention. Furthermore, the metal oxide may be partially modified with an organic group. When used in water-based paints or inks, it is desirable to use a metal oxide because it improves water resistance. Among them, silicon oxide and polysiloxane having an organic group on silicon, as well as composites thereof, are preferably used because of their high water resistance, low cost, and easy availability.

[0024] The amount of the metal oxide is preferably from 10 to 60 parts by mass, more preferably from 15 to 50 parts by mass, relative to 100 parts by mass of the black pigment. If it is 10 parts by mass or more, the black pigment layer can be sufficiently fixed, and if it is 60 parts by mass or less, a black color with a metallic feel is obtained.

[0025] As long as the effect of the present invention is not adversely affected, other coating layers may be provided on the inside or outside of the black pigment layer, if necessary.

[0026] In this way, it is possible to provide the infrared reflective black effect pigment of the present invention, which has high reflectance of near infrared rays and low reflectance of visible light. Specifically, the infrared reflective black effect pigment of the present invention preferably has an average reflectance of 25% or less for visible light (wavelength 380 nm to 780 nm) and an average reflectance of 50% or more for near infrared rays (wavelength 781 nm to 1400 nm). In addition, in order to enable detection by LiDAR, it is preferable that the average reflectance of near infrared rays in the wavelength range of 900 nm to 910 nm is 50% or more.

[0027] By using the infrared reflective black effect pigment of the present invention and a thermoplastic resin, it is possible to provide a thermoplastic resin composition which is expected to sufficiently reflect infrared rays without transmitting them even in a thin molded article.

[0028] The infrared reflective black effect pigment of the present invention may be included in a paint or ink, thereby providing a paint or ink capable of producing a coated article with an infrared reflective black effect that is not affected by infrared absorption by the substrate.

[0029] The coated article of the present invention is coated with the infrared reflective black effect pigment of the present invention. In this way, it is possible to provide a coated article that is not affected by infrared absorption by the base (the object to be coated).

[0030] The present invention can be summarized as follows.

[0031] (1) An infrared reflective black effect pigment comprising metal pigment particles and a black pigment layer coating the metal pigment particles, the black pigment layer comprising a perylene black pigment.

[0032] (2) The infrared reflective black effect pigment according to (1) above, wherein the black pigment layer contains at least one selected from a resin and a metal oxide.

[0033] (3) The infrared reflective black effect pigment according to the above (2), wherein the metal oxide comprises at least one selected from the group consisting of silicon oxide, polysiloxane, and a composite thereof.

[0034] (4) An infrared reflective black effect pigment according to any one of (1) to (3) above, which has a visible light reflectance of 25% or less.

[0035] (5) An infrared reflective black effect pigment according to any one of (1) to (4) above, having an average reflectance of near-infrared light of 900 nm or more and 910 nm or less of 50% or more.

[0036] (6) A thermoplastic resin composition comprising the infrared reflective black effect pigment according to any one of (1) to (5) above and a thermoplastic resin.

[0037] (7) A paint comprising the infrared reflective black effect pigment according to any one of (1) to (6) above.

[0038] (8) An ink comprising the infrared reflective black effect pigment according to any one of (1) to (6) above.

[0039] (9) A coated article coated with the paint described in (7) above or the ink described in (8) above. EXAMPLES

[0040] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these.

[0041] Example 1 [Preparation of aluminum pigment particles] A three-neck flask was charged with 600 mL of mineral spirits, to which 286.0 g of aluminum flake pigment (product name: "CS460", metal content 70 mass%, average particle size 16 μm, manufactured by Toyo Aluminum K.K.) and 40.0 g of Diacid 1550 (manufactured by Harima Chemicals Co., Ltd.) were added, heated and stirred at 100°C, cooled to room temperature, and filtered for degreasing. In this way, degreased aluminum flakes (solid content 70 mass%) were obtained as metal pigment particles. The volume-based median diameter D50 of these metal pigment particles was 16 μm, and the average thickness was 0.3 μm.

[0042] [Pigment attachment process] Next, the following materials were charged into a kneader and stirred at 80° C. for 1 hour. Degreased aluminum flakes (metal pigment particles): 200.0g (as solid content) Mineral spirits (non-polar solvent): 400mL Perylene black pigment (Spectrasense Black EH8082, manufactured by Sun Chemical): 160.0g Aliphatic dicarboxylic acid (Diacid 1550, manufactured by Harima Chemicals Co., Ltd.): 10.0 g Hindered amine (ADEKA STAB LA-67, manufactured by ADEKA Corporation): 10.0 g This resulted in a slurry containing aluminum flakes (pigment-coated particles) in which a black pigment layer was attached to the surface of metal pigment particles.

[0043] [Black pigment layer formation process] Next, the entire amount of the slurry containing the pigment-coated particles obtained was added to 1000 mL of mineral spirits in a three-neck flask, and 1.0 g of acrylic acid was further added and stirred. Furthermore, a solution of 40.0 g of trimethylolpropane trimethacrylate, 10.0 g of divinylbenzene (31.3 g of resin (total of trimethylolpropane trimethacrylate and divinylbenzene) per 100.0 g of perylene black pigment) and 5.0 g of azobisisobutyronitrile dissolved in 150 mL of mineral spirits was added to the three-neck flask, and the mixture was stirred at 100° C. for 6 hours while blowing in nitrogen. After that, the slurry cooled to room temperature was filtered to obtain the effect pigment of Example 1 in which the surface of the base particle was coated with the pigment and the resin having a crosslinked structure of trimethylolpropane trimethacrylate and divinylbenzene. In the effect pigment of Example 1, the average thickness of one side of the black pigment layer was 0.3 μm.

[0044] Example 2 The effect pigment of Example 1 (100 g solids, 46.5 g metals) was dispersed in 1000 mL of isopropyl alcohol (IPA) in a three-neck flask to prepare a slurry, which was then heated to 50° C. 30 g of water was added to the heated slurry, and the pH of the slurry was adjusted to 8.5 by adding an appropriate amount of monoethanolamine.

[0045] Next, 30 g of tetraethoxysilane (hereinafter abbreviated as "TEOS") (solid content after reaction: 8.4 g, 16.0 mass % (as solid content) based on the total amount of pigment and binder) was added as a metal compound (raw material of metal oxide) to the slurry. The mixture was gradually added to the slurry and stirred and mixed at 70°C for 6 hours to allow the reaction of precipitating TEOS as silica on the surface of the resin matrix of the infrared reflective black effect pigment to proceed. During this time, the pH value of the slurry was checked every 2 hours, and an appropriate amount of monoethanolamine was added to adjust the pH of the slurry to 8.5. After the reaction was completed, the slurry was cooled to room temperature and filtered to obtain the effect pigment of Example 2 having a black pigment layer on the surface containing pigment, resin, and silica (metal oxide). In the effect pigment of Example 2, the resin (total of trimethylolpropane trimethacrylate and divinylbenzene) was 31.3g and the metal oxide (produced silica) was 22g per 100.0g of perylene black pigment. The average thickness of the black pigment layer on one side was 0.3μm.

[0046] Comparative Example 1 In the manufacturing method of the black effect pigment of Example 1, 160.0 g of perylene black pigment (Spectrasense Black EH8082, manufactured by Sun Chemical) was replaced with 160.0 g of carbon black pigment (#2650, manufactured by Mitsubishi Chemical Corporation), and the rest was the same as in Example 1 to obtain the effect pigment of Comparative Example 1.

[0047] Comparative Example 2 The aluminum flake pigment (product name: “CS460”) used in Example 1 was used as the effect pigment in Comparative Example 2.

[0048] Comparative Example 3 Plate-like alumina was prepared as metal oxide particles according to Example 1 of JP-A No. 2000-247634, and this plate-like alumina was used as the effect pigment of Comparative Example 3 in place of the metal pigment particles.

[0049] Comparative Example 4 [Preparation of alumina pigment] 600 mL of mineral spirits was placed in a three-neck flask, to which 200.0 g of plate-like alumina prepared according to Example 1 of JP 2000-247634 A and 40.0 g of Diacid 1550 (manufactured by Harima Chemicals Co., Ltd.) were added, and the mixture was heated and stirred at 100°C, cooled to room temperature, and filtered to perform degreasing.

[0050] [Pigment attachment process] Next, the following materials were charged into a kneader and stirred at 80° C. for 1 hour. Degreased plate alumina: 200.0g (as solids) Mineral spirits (non-polar solvent): 400mL Perylene black pigment (Spectrasense Black EH8082, manufactured by Sun Chemical): 160.0g Aliphatic dicarboxylic acid (Diacid 1550, manufactured by Harima Chemicals Co., Ltd.): 10.0 g Hindered amine (ADEKA STAB LA-67, manufactured by ADEKA Corporation): 10.0 g This resulted in a slurry containing plate alumina having black pigment attached to its surface (pigment-coated plate alumina).

[0051] [Black pigment layer formation process] Next, the entire amount of the obtained slurry containing the black pigment-coated plate alumina was added to 1000mL of mineral spirits in a three-necked flask, and 1.0g of acrylic acid was added and stirred. Furthermore, a solution of 40.0g of trimethylolpropane trimethacrylate, 10.0g of divinylbenzene, and 5.0g of azobisisobutyronitrile dissolved in 150mL of mineral spirits was added to the three-necked flask, and the mixture was stirred at 100°C for 6 hours while blowing in nitrogen. After that, the slurry was cooled to room temperature and filtered to obtain a black plate alumina pigment as the effect pigment of Comparative Example 4, in which the surface of the plate alumina is coated with the black pigment and a resin having a crosslinked structure of trimethylolpropane trimethacrylate and divinylbenzene.

[0052] Test Example 1 The effect pigments of each Example and Comparative Example were made into paints according to the formulations in Table 1. The "amount of black pigment added" refers to the amount of perylene black pigment (Spectrasense Black EH8082, manufactured by Sun Chemical) added.

[0053] [Table 1]

[0054] Each of the paints obtained was applied to a black and white hiding power test paper using a 6 mils applicator and dried at room temperature for 2 hours. The average reflectance of each of the coating films obtained on the white and black backgrounds was measured using a spectrophotometer UV-2700 (Shimadzu Corporation) in integrating sphere reflectance mode in the wavelength range of 380 to 780 nm as the visible light wavelength band, 900 to 910 nm as the LiDAR sensing wavelength band, and 781 to 1400 nm as the near infrared wavelength band. The results are shown in Table 2.

[0055] [Table 2]

[0056] Test Example 2 The pigments of each Example and Comparative Example were made into paints according to the formulations shown in Table 3. The "amount of black pigment added" is the amount of perylene black pigment (Spectrasense Black EH8082, manufactured by Sun Chemical) added.

[0057] [Table 3]

[0058] The resulting paint was applied to a steel plate with a bell-type coating machine so that the dry thickness was 18±2 μm, and after applying a clear coat and drying, the color was measured with a spectrophotometer (CM-5, manufactured by Konica Minolta, Inc.) The results are shown in Table 4.

[0059] [Table 4]

[0060] The results of Test Examples 1 and 2, comparing Example 1 with Comparative Example 1, show that the near-infrared reflectance is low when carbon black is used. Furthermore, the results of Test Example 2 for Example 1 and Comparative Example 2 show that when actually painted, simply mixing metal pigment particles with black pigment results in low jet blackness due to a high L*. The results of Test Example 1 for Example 1 and Comparative Example 4 show that by using metal pigment particles instead of metal oxide particles as the base material, near-infrared can be reflected without being affected by the base. Furthermore, the near-infrared reflectance of each Example is high not only in the LiDER sensing wavelength band but also in a wider near-infrared wavelength band, so it can be expected that not only LiDER sensing is possible but also that the material will have heat insulation properties.

[0061] The above-disclosed embodiments and examples should be considered as illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims, not by the above description, and includes all modifications within the meaning and scope of the claims.

Claims

1. Metal pigment particles; a black pigment layer covering the metal pigment particles; The black pigment layer comprises a perylene black pigment, an infrared reflective black effect pigment.

2. 2. The infrared reflective black effect pigment of claim 1, wherein said black pigment layer comprises at least one selected from a resin and a metal oxide.

3. 3. The infrared reflective black effect pigment of claim 2, wherein said metal oxide comprises at least one selected from the group consisting of silicon oxides, polysiloxanes, and composites thereof.

4. 2. The infrared reflective black effect pigment of claim 1 having a visible light reflectance of 25% or less.

5. 2. The infrared reflective black effect pigment according to claim 1, having an average reflectance of near infrared light of 900 nm or more and 910 nm or less of 50% or more.

6. A thermoplastic resin composition comprising the infrared reflective black effect pigment according to any one of claims 1 to 5 and a thermoplastic resin.

7. A paint comprising the infrared reflective black effect pigment according to any one of claims 1 to 6.

8. 7. An ink comprising the infrared reflective black effect pigment of claim 1.

9. A coated article coated with the paint according to claim 7 or the ink according to claim 8.

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