EP-4177316-B1 - COATING COMPOSITION AND METHOD FOR PRODUCING COATING COMPOSITION

Inventors

• YABUSHITA, Chisato
• KAMBAYASHI, Yuka
• UEHARA, Tamami
• SAKOYAMA, Kazuaki

Dates

Publication Date

20260506

Application Date

20210621

Claims (6)

1. A coating composition comprising a coating-film-forming resin, a phosphoric-acid-group-containing organic compound, and a pigment, wherein the pigment comprises a flake-shaped vapor-deposited metal pigment, the coating-film-forming resin comprises an acrylic resin emulsion, the flake-shaped vapor-deposited metal pigment has a first protective layer, a vapor-deposited metal layer, and a second protective layer in this order, the flake-shaped vapor-deposited metal pigment has an average particle diameter of 10 to 150 µm, an average thickness of 0.5 to 10 µm, and an aspect ratio of 5 to 50, the vapor-deposited metal layer comprises aluminum, copper, gold, silver, zinc, titanium, chromium, nickel, nickel chromium, stainless-steel, or a mixture thereof, and an amount of the flake-shaped vapor-deposited metal pigment comprised in the coating composition is in a range of 0.1 to 30 parts by mass based on 100 parts by mass of a resin solid content of the coating-film-forming resin; a cured coating film of the coating composition has a sparkle intensity (Si) of 20 or more at an incident angle of 45°, a sparkle area (Sa value) of 10 or more at an incident angle of 45°, and a graininess value (G value) of more than 10, wherein Si, the Sa value and the G value are determined as described herein.
2. The coating composition according to claim 1, wherein the first and second protective layers each have an average thickness of 0.5 to 3 µm, and the vapor-deposited metal layer has an average thickness of 5 to 100 nm.
3. The coating composition according to claim 1 or 2, wherein the first and second protective layers each comprise a silicone component.
4. The coating composition according to any one of claims 1 to 3, wherein the vapor-deposited metal layer comprises aluminum.
5. A method for producing a cured coating film, the method comprising applying the coating composition according to any one of claims 1 to 4 to an object to be coated, and subsequently heating and curing the coating composition, wherein the cured coating film has a sparkle intensity (Si) of 20 or more at an incident angle of 45°, a sparkle area (Sa value) of 10 or more at an incident angle of 45°, and a graininess value (G value) of more than 10.
6. An article comprising a cured coating film of the coating composition according to any one of claims 1 to 4.

Description

TECHNICAL FIELD The present invention relates to a coating composition and a method for producing a coating composition. BACKGROUND ART A plurality of coating films having respective distinct roles are sequentially formed on the surface of an object to be coated such as an automobile body, and the coating films protect the object and concurrently impart aesthetic appearance and excellent design to the object. A forming method of such a plurality of coating films generally includes forming an under-coating film such as an electrodeposition coating film on an object to be coated having excellent electric conductivity, and sequentially forming an optional intermediate coating film, and a top-coating film on the under-coating film. In these coating films, it is the top-coating film including a base coating film and a clear coating film that significantly affects, in particular, the appearance and design of the coating films. In automobiles, in particular, the appearance and design of the top-coating film, which includes the base coating film and the clear coating film and is formed on a body, are of great importance. Base coating films can be roughly classified into coating films which contain no flake-shaped pigment and are referred to as so-called "solid color", and coating films which contain a flake-shaped pigment with an impression of sparkling (glitter appearance or brilliance). A typical example of the flake-shaped pigment with an impression of sparkling is a flake-shaped aluminum pigment. A base coating film containing the flake-shaped aluminum pigment can exhibit metallic tone gloss (metallic impression). In recent years, coating films having a high degree of designability have been developed in the field of automobile coatings. This trend correlates to consumers' tendency to prefer, to the so-called solid color, a color of coating which gives an impression of sparkling leading to a high-quality appearance. Furthermore, there is a demand for a more distinctive design, e.g., a coating film not only giving an impression of sparkling but also having a higher luminance than conventional coating films that give an impression of sparkling, due to the consumers' diversified preferences and aspirations of uniqueness. WO 2019/131957 (Patent Document 1) discloses a coating composition comprising: a binder component (A); a flake-like aluminum pigment (B) having an average particle diameter (d50) within a range of 18 µm to 25 µm; and a flake-like pigment (C) being a flake-like pigment other than a flake-like aluminum pigment and having an average particle diameter (d50) within a range of 8 µm to 30 µm. Patent Document 1 discloses that this coating composition can be used to form a coating film giving the impression of being highly granular and reduced generation of metallic unevenness.US2004/018109 A1 discloses a similar coating composition. Patent Document 1: PCT International Publication No. WO 2019/131957, Specification DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The aforementioned Patent Document 1 discloses that a combination of the specific flake-like aluminum pigment (B) and the specific flake-like pigment (C) being a flake-like pigment other than a flake-like aluminum pigment, or the disclosed coating composition can be used to form a coating film giving the impression of being highly granular and reduced generation of metallic unevenness. In addition, Patent Document 1 discloses that a graininess value (G value) of 5.0 or more is preferred since such a graininess value (G value) results in the impression of being highly granular, and that a graininess value (G value) of 10.0 or less is preferred since such a graininess value (G value) results in the prevention of the generation of metallic unevenness, and excellent image quality. An object of the present invention is to provide a coating film containing a sparkling pigment, as described in, e.g., the aforementioned Patent Document 1, and having a higher luminance than conventional coating films. Means for Solving the Problems In order to solve the aforementioned problems, the present invention provides the following aspects. A first aspect of the present invention relates to a coating composition as claimed in claim 1. A second aspect of the present invention relates to the coating composition according to the first aspect, wherein the first and second protective layers each have an average thickness of 0.5 to 3 µm, and the vapor-deposited metal layer has an average thickness of 5 to 100 nm. A third aspect of the present invention relates to the coating composition according to the first or second aspect, wherein the first and second protective layers each comprise a silicone component. A fourth aspect of the present invention relates to the coating composition according to any one of the first to third aspects, wherein the vapor-deposited metal layer comprises aluminum. A fifth aspect of the present invention relates to a method fo