Brilliant pigment

Abstract

Provided is a brilliant pigment comprising a flake-like non-metallic base and a metal oxide film on the base, wherein: metal particles are adhered to the surface of the metal oxide film; the metal particles include at least one metal selected from the group consisting of silver and nickel; and in a 2.5 μm × 1.9 μm region of said surface, there are not more than 1,400 silver particles.

Description

Glossy pigment

[0001] The present invention relates to a glossy pigment, and more particularly to a glossy pigment containing a flaky non-metallic substrate and a metal oxide film.

[0002] Glossy pigments are added to various products to give the products particulate light reflection. Paints used in vehicles such as automobiles are one example. As a glossy pigment for vehicles, flaky aluminum (aluminum flakes) is often used. Aluminum flakes are suitable for imparting a metallic appearance to the vehicle's paint film.

[0003] However, a paint film containing aluminum flakes inhibits the transmission of millimeter waves and causes diffuse reflection of millimeter waves depending on the application site. With the spread of vehicle autonomous driving technology, there is a need to solve problems caused by aluminum flakes.

[0004] A glossy pigment using a flaky non-metallic substrate is superior to aluminum flakes in terms of millimeter wave permeability. Patent Document 1 discloses a glossy pigment including flaky glass, a titanium oxide layer and a silver layer formed in this order on the flaky glass. In the glossy pigment of Patent Document 1, the product of the optical thickness of the flaky glass and the optical thickness of the titanium oxide layer is adjusted to be 61000 or more and 66000 or less in nm display, and the physical thickness of the silver layer is adjusted to be 35 nm or more and 55 nm or less. In Patent Document 1, in the direction along the thickness of the flaky glass, the silver layer / titanium oxide layer / flaky glass / titanium oxide layer / silver layer constitutes one optical interference system, thereby achieving a desired reflectance and color tone. <A

[0005] Japanese Patent No. 6227850

[0006] Although a high reflectance can be obtained from the glossy pigment of Patent Document 1, there is room for improvement in terms of metallic feeling. Therefore, an object of the present invention is to provide a new glossy pigment suitable for expressing a metallic appearance while using a non-metallic substrate.

[0007] The present invention provides a lustrous pigment comprising a flake-shaped nonmetallic substrate and a metal oxide film on the substrate, wherein metal particles are attached to the surface of the metal oxide film, the metal particles include at least one selected from the group consisting of silver and nickel, and the number of silver particles is 1400 or less in a 2.5 μm × 1.9 μm area on the surface.

[0008] According to the present invention, a lustrous pigment suitable for producing a metallic appearance is provided, even when using a non-metallic substrate.

[0009] This figure shows the results of observing the surface of the lustrous pigment according to Example 1 using a scanning electron microscope (SEM). This figure shows the results of observing the surface of the lustrous pigment according to Comparative Example 1 using an SEM.

[0010] The details of the present invention will be described below, but this description is not intended to limit the present invention to any particular embodiment. In the following, "main component" means the component that is present in the highest amount by mass, and "substantially absent" means that the content is less than 0.1% by mass, and even less than 0.01%. In addition, the upper and lower limits indicating numerical ranges in the following can be combined arbitrarily.

[0011] As a result of diligent research, the inventors have found that the metallic feel of a lustrous pigment can be improved by arranging metals such as silver and nickel on the surface of the metal oxide film of the lustrous pigment as an appropriate number of particles rather than as layers. That is, one embodiment of the present invention is a lustrous pigment comprising a flake-shaped nonmetallic substrate and a metal oxide film on the substrate, wherein metal particles are attached to the surface of the metal oxide film, the metal particles include at least one selected from the group consisting of silver and nickel, and the number of silver particles is in the range of 1400 or less in a 2.5 μm × 1.9 μm area on the surface.

[0012] (Flake-like nonmetallic substrate) Flake-like refers to a minute, plate-like shape, also called flaky. The nonmetallic substrate mainly consists of inorganic or organic substances other than metals, especially inorganic substances other than metals. The nonmetallic substrate may contain metals, but may also be substantially metal-free. Examples of flake-like nonmetallic substrates are flake-like glass, flake-like alumina, mica, talc, or sericite. The mica may be natural mica or synthetic mica. Preferred flake-like substrates are flake-like glass, flake-like alumina, or mica.

[0013] The main surface of flake glass exhibits superior smoothness compared to crystalline granules such as mica, making it particularly suitable for achieving a metallic appearance. Suitable glass compositions for flake glass include, for example, those primarily composed of silicon oxide, further containing other oxide components such as aluminum oxide, calcium oxide, and sodium oxide. Examples of glass compositions include soda-lime glass, A-glass, C-glass, E-glass, ECR glass, borosilicate glass, and aluminosilicate glass. Flake glass can be obtained by known methods such as the blown glass method and the rotary glass method.

[0014] The average thickness of the flake-like substrate is, for example, 0.05 μm or more, 0.1 μm or more, 0.2 μm or more, 0.3 μm or more, 0.6 μm or more, and even 0.8 μm or more, and may be 1 μm or more in some cases. The average thickness of the flake-like substrate is, for example, 10 μm or less, 8 μm or less, and even 6 μm or less, and may be 3 μm or less in some cases. The average thickness of the flake-like substrate is, for example, 0.05 μm or more and 10 μm or less, and even 0.1 μm or more and 6 μm or less. The average thickness of the flake-like substrate is determined by the average value of the thicknesses of at least 50 flake-like substrates. The thickness of individual flake-like substrates can be measured by observation using SEM.

[0015] In Patent Document 1, the flake-like glass, together with the layer covering it, constitutes part of the optical interference system. In order to satisfy the above-mentioned conditions defined by the optical thickness, its physical thickness is limited to a range that is neither too small nor too large. In fact, the thickness of the flake-like glass in the embodiment of Patent Document 1 is 0.288 μm or more and 0.535 μm or less. In this embodiment, it is not necessary for the flake-like glass to constitute part of the optical interference system. Therefore, the average thickness of the flake-like glass in this embodiment may be 0.05 μm or more and 0.25 μm or less, or 0.6 μm or more and 10 μm or less. However, the average thickness of the flake-like glass is not limited to these ranges and may be greater than 0.25 μm and less than 0.6 μm.

[0016] The average particle size of the flake-like substrate is, for example, 200 μm or less, 100 μm or less, 70 μm or less, and even 60 μm or less. The average particle size of the flake-like substrate is, for example, 3 μm or more, and in some cases 5 μm or more. The average particle size of the flake-like substrate can be determined by the particle size (D50) at which the cumulative volume from the smaller particle size side corresponds to 50% in the particle size distribution of the light scattering equivalent diameter measured by laser diffraction.

[0017] The aspect ratio of the flake-like substrate is, for example, 10 or more, 15 or more, and even 20 or more. The aspect ratio of the flake-like substrate may also be, for example, 300 or less. The aspect ratio of the flake-like substrate can be determined by dividing the average particle size by the average thickness.

[0018] (Metal Oxide Film) A metal oxide film is a film whose main component is a metal oxide. The metal oxide may be at least one selected from the group consisting of titanium oxide, zinc oxide, tin oxide, zirconium oxide, aluminum oxide, silicon oxide, niobium oxide, tantalum oxide, and iron oxide. The metal oxide film may also be a film whose main component is titanium oxide, particularly rutile-type titanium oxide. A metal oxide film whose main component is titanium oxide is suitable for producing a vivid appearance.

[0019] The metal oxide film may be a single layer or may consist of multiple layers. The multiple-layer metal oxide film may consist of layers adjacent to layers that are primarily composed of different metal oxides.

[0020] The preferred thickness of each layer constituting a metal oxide film varies depending on the type of metal oxide that makes up the layer, but for example, it is between 30 nm and 500 nm, and more specifically between 40 nm and 300 nm. As an example, the preferred thickness of a metal oxide film that is a single layer mainly composed of titanium oxide is between 40 nm and 250 nm, and more specifically between 50 nm and 200 nm.

[0021] The relationship between the thickness of a single-layer film primarily composed of titanium dioxide and the resulting color is generally as follows (thickness:color): 50nm–70nm: silver, 70nm–120nm: yellow, 120nm–140nm: red, 150nm–165nm: blue, 165nm–185nm: green

[0022] Silver metallic finishes are in high demand for vehicle paint finishes. Therefore, for single-layer films primarily composed of titanium dioxide, one suitable thickness range is 50 nm to 70 nm. However, the luminous pigments in this embodiment are not limited to this range and can have metallic appearances based on the above color systems. Flake-shaped glass with titanium dioxide films in the above color systems is sold by Nippon Sheet Glass Co., Ltd. as part of the MetaShine (registered trademark) series.

[0023] (Metal particles) The metal particles include at least one selected from the group consisting of silver and nickel. The metal particles may include at least one selected from the group consisting of silver and nickel. The metal particles may also be silver particles.

[0024] By attaching an appropriate number of metal particles to the surface of the metal oxide film, it is possible to improve the metallic appearance. It is desirable that the metal particles be present in a range of 1400 or less, 1300 or less, and even 1200 or less within a 2.5 μm x 1.9 μm area on the surface of the metal oxide film. It is also desirable that the metal particles be present in the range of 3 or more, 5 or more, 10 or more, 20 or more, 30 or more, 40 or more, and even 50 or more within the above area. The number of metal particles can be measured by observation using a scanning electron microscope (SEM). A magnification of 50,000x is appropriate for SEM observation. The desirable number of metal particles for achieving a strong metallic appearance is 10 to 1400, 30 to 1400, 40 to 1400, and especially 50 to 1300.

[0025] The number of metal particles suitable for achieving a dark metallic appearance is 200 to 1400, particularly 300 to 1300. The number of metal particles suitable for achieving a light metallic appearance is 3 to less than 200, 10 to less than 200, 30 to less than 200, particularly 50 to less than 180. * a * b * Color system L * As shown, dark metallic tones correspond to less than 60, and light metallic tones correspond to 60 or more.

[0026] The particle size of the metal particles is, for example, between 1 nm and 90 nm, and more specifically between 5 nm and 70 nm, and in some cases between 10 nm and 50 nm. The particle size of the metal particles can be measured using a scanning electron microscope (SEM). The particle size of the metal particles can be determined by the average value of the longest diameter and the diameter along the direction perpendicular to the midpoint of the longest diameter.

[0027] The metal content of the metal particles in the overall lustrous pigment may be 18% or less, 15% or less, 12% or less, or in some cases 10% or less, by mass. The metal content in the overall lustrous pigment may be 2% or more, 3% or more, 4% or more, 5% or more, in some cases 6% or more, and even 8% or more, by mass. The appropriate metal content varies slightly depending on the type and thickness of the flake substrate. For example, for a flake substrate with a thickness of 0.05 μm or more and 0.25 μm or less, the metal content may be 8% or more and 18% or less, or even 8% or more and 15% or less, by mass. For a flake substrate with a thickness exceeding 0.25 μm and less than 0.6 μm, the metal content may be 5% or more and 12% or less, by mass. For flake-shaped substrates with a thickness of 0.6 μm or more and 10 μm or less, the metal content may be 2% or more and 10% or less by mass, and may also be 2% or more and 8% or less.

[0028] If the metal particle content is too high, the particles will form layers; therefore, it is desirable to appropriately control the supply amount of metal raw materials in the manufacturing process of lustrous pigments. Aside from this point, the deposition of metal onto the surface of the metal oxide film is not particularly limited and can be carried out using known methods such as plating.

[0029] Trace amounts of metal tend to aggregate on metal oxide films upon heat treatment. This property can be utilized in the manufacturing process of lustrous pigments. By heating the metal at an appropriate temperature after application, the thin metal film can be aggregated and dispersed as particles, or the number of metal particles can be reduced to an appropriate level. The heating temperature should ideally be 500°C or higher, and even better, between 550°C and 650°C.

[0030] The lustrous pigment may comprise a nonmetallic substrate, a metal oxide film, and metal particles, as well as other films and particles. Examples of other films include protective films that coat the metal particles. The protective film is preferably composed primarily of non-metallic substances and may be substantially free of metal. Other particles include particles other than metal particles.

[0031] The lustrous pigment of this embodiment is particularly useful in vehicle coatings, but can be used in coatings based on other materials as well. Similarly, the lustrous pigment of this embodiment is particularly useful as a vehicle paint, but can also be used in paints based on other materials as well. The lustrous pigment of this embodiment can be used not only in paints, but also in cosmetics, inks, resin compositions, and other pigment-containing compositions. Examples of cosmetics include facial cosmetics, makeup cosmetics, and hair cosmetics.

[0032] As described above, this specification discloses the following technologies: (Technology 1) A luminous pigment comprising a flake-like nonmetallic substrate and a metal oxide film on the substrate, wherein metal particles are attached to the surface of the metal oxide film, the metal particles include at least one selected from the group consisting of silver and nickel, and the number of silver particles in a 2.5 μm × 1.9 μm area on the surface is in the range of 1400 or less.

[0033] (Technology 2) The luminous pigment of Technology 1, wherein the metal particles are present in the region in a range of 3 to 1400.

[0034] (Technology 3) The luminous pigment of Technology 2, wherein the metal particles are present in the region in a range of 10 to 1400.

[0035] (Technology 4) The luminous pigment of Technology 3, wherein the metal particles are present in the region in a range of 200 to 1400.

[0036] (Technology 5) The luminous pigment of Technology 2, wherein the metal particles are present in the region in a range of 3 or more but less than 200.

[0037] (Technology 6) A lustrous pigment according to any one of Technologies 1 to 5, wherein the ratio of the metal constituting the metal particles to the total lustrous pigment by mass is 18% by mass or less.

[0038] (Technology 7) A luminous pigment according to any one of Technologies 1 to 6, wherein the substrate is flake-shaped glass.

[0039] (Technology 8) A luminous pigment according to any one of Technologies 1 to 7, wherein the metal oxide film contains titanium oxide.

[0040] (Technology 9) A luminescent pigment according to any one of Technologies 1 to 8, wherein the metal particles are silver particles.

[0041] (Technology 10) A coating film containing a luminescent pigment according to any one of Technologies 1 to 9.

[0042] (Technology 11) A pigment-containing composition containing a luminescent pigment according to any one of Technologies 1 to 9.

[0043] Hereinafter, the present embodiment will be described more specifically by way of examples. [Examples 1 to 5 and Comparative Examples 1 to 2] <Production of Luminescent Pigment> (Example 1) Titanium oxide-coated flaky glass (Meta Shine GT1030RS manufactured by Nippon Sheet Glass Co., Ltd.; substrate thickness 1.3 μm, average particle size 33 μm) coated with a rutile-type titanium oxide film having a thickness that exhibits the interference color of silver was prepared as a flaky substrate. 0.2 g of stannous chloride was added to 500 ml of pure water and dissolved, and further dilute hydrochloric acid was added to prepare a pretreatment solution for electroless plating having a pH of 2.0 to 2.2. 100 g of titanium oxide-coated flaky glass was put into this pretreatment solution, then taken out and washed with water. By repeating this treatment several times, the titanium oxide-coated flaky glass was pretreated.

[0044] Next, a silver film was formed on the pretreated titanium oxide-coated flaky glass by the electroless plating method. First, 8.5 ml of 25% by mass aqueous ammonia as a complexing agent, 0.75 g of sodium hydroxide as a pH adjuster, and 4.5 g of silver nitrate as a silver raw material were added to 1 L of pure water, and these were stirred while heating to 30°C to obtain plating solution A. On the other hand, 2.5 g of glucose as a reducing agent was added to 1 L of pure water to prepare a glucose solution, and the titanium oxide-coated flaky glass subjected to the pretreatment was added to this solution and stirred to prepare plating solution B.

[0045] Further, plating solution B was added to plating solution A, and stirred for 20 minutes to advance the electroless plating reaction and deposit silver on the surface of the titanium oxide-coated flaky glass. Then, filtration and washing with water were repeated several times, and drying was carried out. After drying, heat treatment was carried out at 500°C for 1 hour to obtain a luminescent pigment.

[0046] (Example 2) A luminescent pigment was obtained in the same manner as in Example 1 except that the heat treatment temperature was 550°C.

[0047] (Example 3) A lustrous pigment was obtained in the same manner as in Example 1, except that the heat treatment temperature was 600°C.

[0048] (Example 4) A lustrous pigment was obtained in the same manner as in Example 1, except that the heat treatment temperature was 670°C.

[0049] (Example 5) A titanium oxide coated flake glass (MetaShine GTB018RS, manufactured by Nippon Sheet Glass Co., Ltd.; substrate thickness 0.2 μm, average particle size 18 μm) coated with a rutile-type titanium oxide film to a thickness that exhibits silver interference color was prepared as a flake substrate. 1.3 g of stannous chloride was added to 1 L of pure water and dissolved, and then dilute hydrochloric acid was added to prepare a pretreatment solution for electroless plating with a pH of 2.0 to 2.2. 100 g of titanium oxide coated flake glass was added to this pretreatment solution, and then removed and washed with water. This process was repeated several times to pretreat the titanium oxide coated flake glass.

[0050] Next, a silver coating was formed on the pre-treated titanium oxide coated flake glass by electroless plating. First, 30 ml of 25% by mass aqueous ammonia as a complexing agent, 2.6 g of sodium hydroxide as a pH adjuster, and 13 g of silver nitrate as a silver raw material were added to 4.5 L of pure water, and these were stirred while being heated to 30°C to obtain plating solution A. On the other hand, 8 g of glucose was added to 1 L of pure water as a reducing agent to prepare a glucose solution, and the pre-treated titanium oxide coated flake glass was added to this solution and stirred to prepare plating solution B.

[0051] Furthermore, plating solution B was added to plating solution A and stirred for 20 minutes to allow the electroless plating reaction to proceed, depositing silver onto the surface of the titanium oxide coated flake-shaped glass. After that, filtration and washing with water were repeated several times, and drying was performed. After drying, heat treatment was carried out at 550°C for 1 hour to obtain a lustrous pigment.

[0052] (Comparative Example 1) A lustrous pigment was obtained in the same manner as in Example 1, except that heat treatment was not performed.

[0053] (Comparative Example 2) A luminous pigment was obtained in the same manner as in Example 1, except that flake-shaped glass not coated with a rutile-type titanium oxide film was used.

[0054] <Evaluation of Luminous Pigments> The luminous pigments obtained in each example and comparative example were used as measurement samples for the following evaluation. (Number of Silver Particles) Using a field emission scanning electron microscope "S-4700" (manufactured by Hitachi High-Tech Corporation), the backscattered electron image of the measurement sample was observed under the conditions of observation magnification of 50,000x, acceleration voltage of 50kV, and sample tilt of 0°, and the number of silver particles was measured. The measurement sample was fixed to conductive double-sided tape and coated with Pt-Pd for conductive treatment. A rectangular field of view defined by 2.5 μm × 1.9 μm was observed, and the number of silver particles was counted, with white objects in this area being considered silver particles. Five field of view areas were observed for one measurement sample, and the average number of silver particles was taken as the number of silver particles in the measurement sample.

[0055] (Silver Content) 0.1 g of the sample was added to 20 ml of water, then 5 ml of nitric acid (1+1), and the mixture was heated to dissolve the sample. After cooling, the solution was filtered using filter paper, and the filtered sample was thoroughly washed with nitric acid. Water was added to the filtrate to make 100 ml, which was the measurement solution. The concentration of silver in the measurement solution was measured by ICP emission spectrometry, and the silver content in the sample was calculated using the following formula: Content (wt%) = Measured value (ppm) × 100 (ml) / 0.1 (g) × 10 -4

[0056] (Reflected light) 1 g of the measurement sample was mixed with 9 g of acrylic lacquer (Nippon Paint Co., Ltd., Acrylic Super Clear), thoroughly mixed, and applied to a 9 mil film thickness on opacity test paper (black and white), and allowed to air dry at room temperature. A colorimeter (Konica Minolta Corporation) was used to measure the CIE 1976 (L * a * b * The white side was measured based on the color system. In addition, the color tone and metallic feel were evaluated visually. The metallic feel was evaluated on a five-point scale, from most metallic to least metallic, based on the following criteria.

[0057] 5: Noticeably metallic 4: Sufficiently metallic 3: Slightly metallic 2: Slightly metallic 1: Not metallic

[0058] (Millimeter-wave transmission attenuation) 1 g of the sample to be measured was mixed with 9 g of acrylic lacquer (Nippon Paint Co., Ltd., Acrylic Super Clear), thoroughly mixed, and coated onto a PET film (thickness 0.1 mm) to a thickness of 152 μm (wet film thickness) using a bar coater. The sample was then air-dried at room temperature to prepare the measurement sample. In addition, to eliminate the influence of the film and lacquer, a control sample was prepared by coating the PET film with only acrylic lacquer.

[0059] Using a vector network analyzer (PNA-X N5247B, PNA N5222B: Keysight Technologies), a millimeter-wave module (WR12-VNAX: Virginia Diodes), and a high-frequency free-space type frequency variation method measurement jig, electromagnetic waves with frequencies of 22-33 GHz or 60-90 GHz were incident from an oscillator at an incidence angle of 0° at room temperature. Based on the measured values ​​at frequencies of 24 GHz and 78 GHz, the attenuation was determined using the following formula: Attenuation = (Attenuation of control sample) - (Attenuation of measured sample)

[0060] The results are shown in Tables 1 and 2. Note that in Reference Example 1, the Metashine® used in Examples 1-4 was used as is, while in Reference Example 2, commercially available aluminum flakes were used.

[0061]

[0062]

[0063] SEM images of the lustrous pigments of Example 1 and Comparative Example 1 are shown in Figures 1 and 2, respectively. In each example, it is thought that the metallic appearance was improved because the metal particles (silver particles) aggregated due to the heat treatment, and interference light originating from the metal oxide film (titanium oxide film) was observed along with the reflected light from the silver particles.

[0064] From these results, it can be understood that the metallic feel can also be improved by using nickel particles, which produce reflected light similar to that of silver particles.

[0065] The lustrous pigment according to the present invention can be used not only in vehicle coatings but also in coatings for other applications, resin molded products, inks, cosmetics, and the like.

Claims

1. A luminous pigment comprising a flake-shaped nonmetallic substrate and a metal oxide film on the substrate, wherein metal particles are attached to the surface of the metal oxide film, the metal particles include at least one selected from the group consisting of silver and nickel, and the number of metal particles in a 2.5 μm × 1.9 μm area on the surface is within the range of 1400 or less.

2. The luminous pigment according to claim 1, wherein the region contains 3 to 1400 metal particles.

3. The lustrous pigment according to claim 2, wherein the region contains between 10 and 1400 metal particles.

4. The lustrous pigment according to claim 3, wherein the region contains 200 to 1400 metal particles.

5. The lustrous pigment according to claim 2, wherein the region contains 3 or more but less than 200 metal particles.

6. The lustrous pigment according to claim 1, wherein the ratio of the metal constituting the metal particles to the total lustrous pigment by mass is 18% or less.

7. The luminous pigment according to claim 1, wherein the substrate is flake-shaped glass.

8. The lustrous pigment according to claim 1, wherein the metal oxide film contains titanium oxide.

9. The luminous pigment according to claim 1, wherein the metal particles are silver particles.

10. A coating film comprising the lustrous pigment described in any one of claims 1 to 9.

11. A pigment-containing composition comprising the lustrous pigment described in any one of claims 1 to 9.

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