Photoluminescent pigment and resin composition

Abstract

This photoluminescent pigment contains a flaky particle and a metal oxide layer formed on at least a part of the surface of the flaky particle. The average particle diameter of the photoluminescent pigment is 90 µm or more. The average thickness of the photoluminescent pigment is more than 5 µm and not more than 15 µm. The ratio of the average particle diameter relative to the average thickness is 10-30. The photoluminescent pigment is suitable for use as a filler for imparting photoluminescence to a resin composition, and can improve the appearance of a resin molded article that contains the photoluminescent pigment. The resin composition contains the photoluminescent pigment and a matrix resin.

Description

Luster pigment and resin composition

[0001] The present invention relates to a bright pigment and a resin composition.

[0002] Generally, bright pigments contain flaky particles. Examples of flaky particles include mica, synthetic mica, talc, flaky glass, flaky silica, and flaky bismuth oxychloride. Bright pigments may also contain a coating on the surface of the flaky particles. The coating may be either a single-layer film or a multi-layer film. The layer constituting the coating may be, for example, a metal oxide layer containing titanium oxide, iron oxide, or the like, or a metal layer of silver, copper, aluminum, or the like. Bright pigments may be used alone in, for example, cosmetics, coating compositions, etc., or as a filler to impart a lustrous appearance to resin compositions.

[0003] Patent Document 1 describes that the use of metal-coated glass flakes with an average shape ratio (thickness / particle size) of 1 / 9 to 1 and an average particle size of 25 to 500 μm as a metallic pigment for resin kneading can suppress the formation of weld lines on the surface of molded products. Weld lines are linear marks that can occur when molten resin flows meet inside an injection molding die, resulting in poor appearance of the molded resin product. In particular, fine particles generated by the destruction of flaky particles during kneading or molding of a resin composition tend to form a layer with a low particle concentration near the leading edge of the molten resin flow inside the injection molding die. This layer with a low particle concentration generates an uneven layer at the meeting point of the molten resin flow. This uneven layer remains as a weld line on the surface of the molded resin product. Weld lines can also cause a decrease in the strength of the molded resin product.

[0004] Patent No. 3456252

[0005] The metallic pigment of Patent Document 1 is resistant to fracture when mixed with a synthetic resin and molded, and can suppress deterioration in appearance due to the formation of weld lines on the surface of the resulting resin molded product. However, according to the inventors' studies, if the average shape ratio and average particle size of the metallic pigment of Patent Document 1, which has a structure in which a metal layer is formed on the surface of glass flakes, are applied to a bright pigment in which a metal oxide layer is formed on the surface of flaky particles, the desired effect may not be obtained.

[0006] An object of the present invention is to improve a bright pigment suitable for use as a filler for imparting a bright appearance to a resin composition. Another object of the present invention is to improve the deterioration of the appearance of a resin molded article containing the bright pigment.

[0007] In one aspect, the present invention provides a bright pigment comprising flaky particles and a metal oxide layer formed on at least a portion of the surface of the flaky particles, wherein the average particle size is 90 μm or more, the average thickness is more than 5 μm and 15 μm or less, and the ratio of the average particle size to the average thickness is 10 or more and 30 or less.

[0008] In another aspect, the present invention provides a resin composition comprising a luster pigment and a matrix resin, wherein the luster pigment comprises flaky particles and a metal oxide layer formed on at least a portion of the surface of the flaky particles, the luster pigment having an average particle size of 90 μm or more and an average thickness of more than 5 μm and not more than 15 μm, and the ratio of the average particle size to the average thickness of the luster pigment is 10 or more and 30 or less.

[0009] According to the present invention, a bright pigment suitable for use as a filler for imparting a bright appearance to a resin composition is provided, and further, the appearance of a resin molded article containing the bright pigment can be improved.

[0010] 1 is a schematic diagram illustrating an example of a glass flake manufacturing apparatus, and FIG. 2 is a schematic diagram illustrating another example of a glass flake manufacturing apparatus.

[0011] Hereinafter, embodiments of the bright pigment and resin composition of the present invention will be specifically described, but the following description is not intended to limit the present invention to any particular embodiment.

[0012] A bright pigment according to a first aspect of the present invention comprises flaky particles and a metal oxide layer formed on at least a portion of the surface of the flaky particles, the bright pigment having an average particle size of 90 μm or more and an average thickness of more than 5 μm and not more than 15 μm, and the ratio of the average particle size to the average thickness being 10 or more and 30 or less.

[0013] In a second aspect of the present invention, for example, in the bright pigment according to the first aspect, the flaky particles are made of glass.

[0014] In a third aspect of the present invention, for example, in the bright pigment according to the first or second aspect, the average particle size is 220 μm or less.

[0015] A resin composition according to a fourth aspect of the present invention is a resin composition comprising a luster pigment and a matrix resin, wherein the luster pigment comprises flaky particles and a metal oxide layer formed on at least a portion of the surface of the flaky particles, the luster pigment having an average particle size of 90 μm or more and an average thickness of more than 5 μm and not more than 15 μm, and the ratio of the average particle size to the average thickness of the luster pigment being 10 or more and 30 or less.

[0016] In a fifth aspect of the present invention, for example, in the resin composition according to the fourth aspect, the flaky particles are made of glass.

[0017] In a sixth aspect of the present invention, for example, in the resin composition according to the fourth or fifth aspect, the average particle size of the bright pigment is 220 μm or less.

[0018] In a seventh aspect of the present invention, for example, in the resin composition according to any one of the fourth to sixth aspects, the matrix resin is a thermoplastic resin.

[0019] In an eighth aspect of the present invention, for example, in the resin composition according to the seventh aspect, the thermoplastic resin is at least one selected from the group consisting of polypropylene, polyethylene, polybutylene terephthalate, polyethylene terephthalate, polycarbonate, polystyrene-based resin, styrene-acrylonitrile copolymer resin, polyacrylate, styrene-butadiene-acrylonitrile copolymer resin, polyarylene sulfide, polyphenylene sulfide, polyacetal, polyamide, polyamideimide, liquid crystal polymer, polyether ether ketone, and polyetherimide.

[0020] [Background to the Invention] It was discovered that even when the average shape ratio and average particle size of a metallic pigment were controlled according to the teachings of Patent Document 1, the desired effect could not be achieved with a bright pigment having a metal oxide layer formed on the surface of flaky particles. Further investigation into this factor revealed that the reflectivity of the metal oxide layer affects the visibility of weld lines on the surface of a resin molded product. Metal oxide layers containing titanium oxide, iron oxide, etc. have lower reflectivity than metal layers such as silver, copper, and aluminum. Therefore, when a bright pigment having a metal oxide layer formed on the surface of flaky particles is used in a resin composition, the weld lines on the surface of the resulting resin molded product tend to be more visible than a bright pigment having a metal layer formed on the surface of flaky particles. In consideration of the above, the present invention was completed, and embodiments thereof are described below.

[0021] [Brilliant Pigment] The brilliant pigment of this embodiment comprises flaky particles and a metal oxide layer formed on at least a portion of the surface of the flaky particles. The brilliant pigment has an average particle size of 90 μm or more, an average thickness of more than 5 μm and not more than 15 μm, and a ratio of the average particle size to the average thickness (aspect ratio) of 10 to 30.

[0022] In this specification, the flaky particles refer to, for example, scale-like particles having an average particle size of 90 μm or more and an average thickness of more than 5 μm and 15 μm or less.

[0023] The average particle size of the bright pigment of this embodiment is the particle size (D50) at which the cumulative volume from the smaller particle size side accounts for 50% in the particle size distribution of the bright pigment measured based on a laser diffraction / scattering method.

[0024] The average thickness of the bright pigment of this embodiment is the average value obtained by measuring the optical path difference between direct light (light not affected by a phase object) and light transmitted through the bright pigment for 100 sheets of coated glass flakes using an interference microscope, and then dividing the total thickness by the number of sheets measured.

[0025] The present inventors have discovered that in order to achieve excellent brilliance in a luster pigment comprising flaky particles and a metal oxide layer formed on at least a portion of the surface of the flaky particles, it is desirable to control the average particle size of the luster pigment to 90 μm or more, the average thickness to more than 5 μm and 15 μm or less, and the aspect ratio to be 10 or more and 30 or less.

[0026] When the average particle size of the luster pigment is 90 μm or more, the reflective area of ​​each luster pigment increases, thereby enhancing the luster of the luster pigment. Furthermore, for a given amount of luster pigment, the smaller the average thickness of the luster pigment, the greater the number of luster pigment particles contained. Therefore, by having the average thickness of the luster pigment be greater than 5 μm and less than 15 μm, the luster of the luster pigment is further enhanced. Furthermore, by controlling the average thickness of the luster pigment to be greater than 5 μm and less than 15 μm, the increase in mass of each luster pigment is suppressed. This makes it difficult for the luster pigment to settle in the molten resin during injection molding, thereby reducing the force required for kneading. As a result, crushing of the luster pigment due to kneading can be suppressed, and wear on the molding equipment, including the screw, and accelerated equipment deterioration can be suppressed.

[0027] In the metallic pigment described in Patent Document 1, the smaller the particle size of the metal-coated glass flakes and the larger the aspect ratio (particle size / thickness), the more noticeable the weld lines. Therefore, to reduce the aspect ratio, the average thickness of the glass flakes is increased to 15 to 31 μm (Table 1). Therefore, when the amount of luster pigment is constant, the number of luster pigment particles contained decreases, and an increase in luster is not expected. Furthermore, in the metallic pigment described in Patent Document 1, if the average particle size of the metal-coated glass flakes is increased to 90 μm or more, the mass of the glass flakes further increases, making them more likely to settle in the molten resin. This increases the force required for kneading, which can accelerate wear on molding equipment, including screws, and accelerate equipment deterioration.

[0028] On the other hand, the bright pigment of this embodiment has an average particle size of 90 μm or more, an average thickness of more than 5 μm and 15 μm or less, and an aspect ratio of 10 or more and 30 or less, thereby making weld lines in resin molded products less noticeable while maintaining excellent brightness.

[0029] The average particle size of the bright pigment of this embodiment is preferably 220 μm or less. By setting the average particle size of the bright pigment to 220 μm or less, crushing of the bright pigment due to kneading is easily suppressed. Therefore, a decrease in the brightness of the bright pigment is suppressed.

[0030] The average particle size of the bright pigment of this embodiment may be 100 μm or more, or may exceed 100 μm. If the average particle size of the bright pigment exceeds 100 μm, the brightness of the bright pigment may be further increased.

[0031] The average thickness of the bright pigment of this embodiment is preferably more than 5 μm and not more than 10 μm. By having the average thickness of the bright pigment be more than 5 μm and not more than 10 μm, an increase in the mass of each bright pigment is further suppressed. As a result, the bright pigment is less likely to settle in the molten resin during injection molding, and the bright pigment can be dispersed with less force during kneading.

[0032] The aspect ratio of the bright pigment of this embodiment is preferably from 10 to 25, more preferably from 10 to less than 20, and even more preferably from 10 to 15. By controlling the aspect ratio within the above numerical range, weld lines in resin molded articles can be made less noticeable.

[0033] The average particle size and average thickness of the flaky particles contained in the bright pigment of this embodiment may satisfy the same numerical ranges as the average particle size and average thickness of the bright pigment of this embodiment. However, the average particle size and average thickness of the flaky particles may be affected by the formation of a metal oxide layer. Therefore, the average particle size and average thickness of the flaky particles contained in the bright pigment are not necessarily the same as the average particle size and average thickness of the bright pigment.

[0034] In the bright pigment of this embodiment, examples of flaky particles include mica, synthetic mica, talc, flaky glass, flaky silica, and flaky bismuth oxychloride. Among these, flaky glass is preferred because it can achieve a higher transparency and the high transparency is further emphasized when the amount of fine powder contained is small. In other words, the flaky particles may be made of glass.

[0035] When the flaky particles are glass flakes, the composition of the glass flakes can be a commonly known glass composition. However, from the viewpoint of forming a metal oxide layer on at least a portion of the surface of the glass flakes, the composition of the glass flakes is preferably one with excellent acid resistance, and for example, C-glass can be suitably used. A typical composition of C-glass is shown below. The units of the following compositions are in mass%.

[0036] 65≦SiO2≦72 1≦Al2O3≦7 4≦CaO≦11 0≦MgO≦5 9≦(Na2O+K2O)≦17 0≦B2O3≦8 0≦ZnO≦6

[0037] Furthermore, when combined with a resin that is sensitive to alkali components, a glass composition with excellent acid resistance and low alkali content is preferred. In this case, a glass composition containing the following components, expressed in mass %, can be used: 59≦SiO2≦65, 8≦Al2O3≦15, 47≦(SiO2−Al2O3)≦57, 1≦MgO≦5, 20≦CaO≦30, 0<(Li2O+Na2O+KO)<2, 0≦TiO2≦5, and substantially free of B2O3, F, ZnO, BaO, SrO, and ZrO2. This glass composition was disclosed by the present applicant in International Publication WO 2006 / 068255. Hereinafter, glass having this glass composition will be referred to as "TA glass." Note that "substantially free of" means that these components are not intentionally included, except in cases where they are inevitably mixed in, for example, with industrial raw materials. Specifically, this means that the content of each of B2O3, F, ZnO, BaO, SrO, and ZrO2 is less than 0.1 mass % (preferably less than 0.05 mass %, more preferably less than 0.03 mass %).

[0038] The composition of the flake glass is not limited to the glass compositions of C glass and TA glass shown above. For example, glass compositions of A glass, E glass, ECR glass, and S glass can also be used. The glass compositions of low dielectric glass disclosed by the present applicant (see, for example, Japanese Patent Publication No. 6505950, Japanese Patent Publication No. 6775159, International Publication No. 2020 / 255396, International Publication No. 2020 / 256142, International Publication No. 2020 / 256143, and International Publication No. 2021 / 049581) can also be used.

[0039] Glass flakes can be produced by, for example, the so-called blowing method disclosed in Japanese Patent Publication Nos. 41-17148 and 45-3541, or the so-called rotary method disclosed in Japanese Patent Laid-Open Nos. 59-21533 and 2-503669.

[0040] In the blowing method, a glass manufacturing apparatus shown in Fig. 1 can be used. This glass manufacturing apparatus is equipped with a refractory kiln tank 12, a blow nozzle 15, and a pressure roll 17. A glass base 11 molten in the refractory kiln tank (melting tank) 12 is inflated into a balloon shape by gas sent into the blow nozzle 15, forming a hollow glass film 16. The hollow glass film 16 is crushed by the pressure roll 17, thereby obtaining glass flakes 1. The thickness of the glass flakes 1 can be controlled by adjusting the pulling speed of the hollow glass film 16, the flow rate of the gas sent from the blow nozzle 15, etc.

[0041] In the rotary method, a glass manufacturing apparatus shown in FIG. 2 can be used. This glass manufacturing apparatus includes a pipe 21, a rotating cup 22, a set of annular plates 23, and an annular cyclone collector 24. The molten glass base 11 is poured from the pipe 21 into the rotating cup 22, flows out radially from the upper edge of the rotating cup 22 due to centrifugal force, passes between the annular plates 23, is sucked by the airflow, and is introduced into the annular cyclone collector 24. While passing through the annular plates 23, the glass is cooled and solidified in the form of a thin film and is further crushed into minute pieces. In this way, glass flakes 1 are obtained. The thickness of the glass flakes 1 can be controlled by adjusting the spacing between the annular plates 23, the speed of the airflow, etc.

[0042] In the bright pigment of this embodiment, the metal oxide layer covers at least a portion of the surface of the flaky particle, and preferably the metal oxide layer covers the entire surface of the flaky particle.

[0043] The metal oxide layer can be formed of, for example, a metal oxide such as titanium oxide or iron oxide, etc. By coating the flaky particles with such a metal oxide layer, a pearlescent pigment can be obtained.

[0044] The average thickness of the metal oxide layer is not particularly limited. In consideration of achieving a brilliance and cost, the average thickness of the metal oxide layer is, for example, preferably 0.01 μm or more and 0.3 μm or less, and more preferably 0.01 μm or more and 0.2 μm or less.

[0045] When the bright pigment of this embodiment is used as a filler for imparting a glittering feel to a resin composition as described above, it can improve the appearance of the resulting resin molded article. That is, the bright pigment of this embodiment may be used as a filler for imparting a glittering feel to a resin composition. The resin composition may contain the bright pigment and a matrix resin.

[0046] [Resin Composition] Next, the resin composition of this embodiment will be described. The resin composition of this embodiment contains a matrix resin and the above-described bright pigment of this embodiment. By including the bright pigment of this embodiment having the above-described characteristics as a filler, the resin composition of this embodiment can improve the appearance of the resulting resin molded article.

[0047] The average particle size and average thickness of the bright pigment contained in the resin composition of this embodiment satisfy the same numerical ranges as those of the above-described average particle size and average thickness of the bright pigment of this embodiment. However, the average particle size and average thickness of the bright pigment may be affected by dispersion in the resin composition, specifically, by extrusion molding to obtain a resin composition containing the bright pigment and / or injection molding to mold the resin composition to obtain a resin molded product. Therefore, the average particle size and average thickness of the bright pigment in the resin composition are not necessarily the same as those of the bright pigment before dispersion in the resin composition.

[0048] The average particle size of the luster pigment contained in the resin composition of this embodiment, i.e., the particle size value (D50) in the particle size distribution, is a value measured by heating the resin composition in an atmosphere of 625°C, removing components other than the luster pigment, extracting the luster pigment, and dispersing the extracted luster pigment in water.

[0049] The average thickness of the luster pigment contained in the resin composition of this embodiment is the average value obtained by heating the resin composition in an atmosphere at 625°C, removing components other than the luster pigment, and extracting 100 or more sheets of luster pigment, calculating the thickness using an interference microscope, and dividing the total thickness by the number of sheets measured.

[0050] The matrix resin may be, for example, a thermoplastic resin, which may be at least one selected from the group consisting of polypropylene, polyethylene, polybutylene terephthalate, polyethylene terephthalate, polycarbonate, polystyrene-based resin, styrene-acrylonitrile copolymer resin, polyacrylate, styrene-butadiene-acrylonitrile copolymer resin, polyarylene sulfide, polyphenylene sulfide, polyacetal, polyamide, polyamideimide, liquid crystal polymer, polyether ether ketone, and polyetherimide.

[0051] Polycarbonate is known to be vulnerable to alkaline components. When the carbonate bonds contained in polycarbonate come into contact with alkaline components, the resin decomposes. Therefore, when the glass flakes are TA glass with a low alkali content, the thermoplastic resin may be polycarbonate.

[0052] The content of the luster pigment in the resin composition is preferably 0.01% by mass or more and 3% by mass or less. By setting the content of the luster pigment to 3% by mass or less, the luster pigment can be uniformly dispersed in the resin composition. In order to further reduce molding shrinkage, the content of the luster pigment is more preferably 0.1% by mass or more and 2% by mass or less.

[0053] The resin composition may contain components other than the matrix resin and the luster pigment. Examples of such components include fillers such as carbon black and thermoplastic elastomers. Thermoplastic elastomers include olefin-based elastomers, styrene-based elastomers, and hydrogenated polymer-based elastomers. Examples of olefin-based elastomers include ethylene-α-olefin copolymer elastomers (ethylene-propylene copolymer elastomer (EPR), ethylene-butene copolymer elastomer (EBR), ethylene-hexene copolymer elastomer (EHR), ethylene-octene copolymer elastomer (EOR)), and ethylene-α-olefin-diene terpolymer elastomers (ethylene-propylene-ethylidenenorbornene copolymer, ethylene-propylene-butadiene copolymer, ethylene-propylene-isoprene copolymer, and the like). Two or more types of thermoplastic elastomers can also be used in combination.

[0054] A resin molded article produced using the resin composition of this embodiment contains a luster pigment, and thus has excellent appearance with less noticeable weld lines while maintaining excellent luster.

[0055] The present invention will be described in more detail below using examples. However, the present invention is not limited to the following examples. Note that the following examples are examples in which glass flakes are used as flaky particles, but the present invention is not limited thereto. Mica, synthetic mica, flaky bismuth oxychloride, etc. may also be used as flaky particles.

[0056] [Example 1] <Forming process of glass flakes> Using TA glass having the composition shown in Table 1, glass flakes were produced by the blowing method described with reference to FIG. 1. Specifically, the TA glass was placed in a melting tank heated to 1500°C and melted. Thin glass was produced while blowing air into it from a nozzle, and this thin glass was continuously drawn out with a roller. The amount of air blown in and the number of rotations of the roller were adjusted to obtain glass flakes with an average thickness of 10 μm.

[0057]

[0058] <Crushing and Classification Step> The glass flakes were crushed using a feather mill and then classified to obtain glass flakes with an average particle size of 100 μm.

[0059] <Pretreatment Step> 1.2 kg of the glass flakes after the crushing and classification steps were added to 8.4 L of ion-exchanged water to obtain a mixed solution. While stirring the mixed solution with a stirrer, dilute hydrochloric acid was added to adjust the pH to 1.5 to obtain a slurry solution. 0.6 L of a 0.5 mass% aqueous solution of tin (IV) chloride at room temperature was added to the slurry solution, and then dilute hydrochloric acid was added to adjust the pH to 1.5 to obtain a mixed slurry solution. After stirring the mixed slurry solution for 5 minutes, the glass flakes were recovered from the mixed slurry solution by vacuum filtration. The recovered glass flakes were washed with ion-exchanged water. In this way, glass flakes pretreated with tin were obtained.

[0060] <Metal Oxide Layer Coating Step> Ion-exchanged water was added to 1.2 kg of the pretreated glass flakes to obtain 12 L of a mixture. Hydrochloric acid was added to the mixture to adjust the pH to 1.0, and the mixture was heated to 75°C. Next, while stirring the mixture, a fixed amount of titanium tetrachloride aqueous solution (16.5 mass% Ti content) was added, and caustic soda was added to maintain the pH constant. The fixed amount of titanium tetrachloride aqueous solution and the addition of caustic soda were continued until the rutile titanium oxide coating formed on the surface of the glass flakes attained a shiny silver color tone. After the coating of the desired color tone was formed, the product was collected by vacuum filtration. The collected product was washed with pure water, dried at 180°C, and then calcined at 600°C. In this way, the coated glass flakes of Example 1 having a rutile titanium oxide layer formed on the surface was obtained.

[0061] <Resin Molding Process> 1.0 part by weight of the coated glass flakes and 99 parts by weight of bisphenol A polycarbonate resin (Iupilon S3000F, manufactured by Mitsubishi Engineering Plastics Corporation) were mixed and then extruded at a cylinder temperature of 290°C using an extrusion molding machine (VS-30, manufactured by Tanabe Plastics Machinery Co., Ltd.) and pelletized. The resulting pellets were dried at 120°C for 5 hours and then molded into test pieces (80 mm long x 10 mm wide x 5 mm thick) of the resin molded product of Example 1 using an injection molding machine (Promat HM7, manufactured by Nissei Plastic Industrial Co., Ltd.) under the following molding conditions. (Molding Conditions) Cylinder Temperature Zone No. 1: 290°C Zone No. 2: 305°C Zone No. 3: 310°C Zone No. 4: 300°C NH (temperature of the injection molding machine head): 300°C Mold temperature: 100°C Maximum filling pressure: 60 kg / cm ３ Screw rotation speed: 150 rpm

[0062] [Example 2] In the glass flake molding process, glass flakes with an average thickness of 7 μm were obtained. Except for this, the same method as in Example 1 was used to obtain coated glass flakes of Example 2, in which a rutile-type titanium oxide layer was formed on the surface. The coated glass flakes of Example 2 exhibited a silver interference color. Using the coated glass flakes of Example 2, a test piece of a resin molded product of Example 2 was obtained using the same method as in Example 1.

[0063] [Example 3] In the crushing and classification process, glass flakes with an average particle size of 200 μm were obtained. Except for this, the same method as in Example 1 was used to obtain coated glass flakes of Example 3, in which a rutile-type titanium oxide layer was formed on the surface. The coated glass flakes of Example 3 exhibited a silver interference color. Using the coated glass flakes of Example 3, a test piece of a resin molded product of Example 3 was obtained using the same method as in Example 1.

[0064] [Example 4] In the glass flake molding process, glass flakes with an average thickness of 7 μm were obtained. Next, in the crushing and classification process, glass flakes with an average particle size of 200 μm were obtained. Except for these, the same method as in Example 1 was used to obtain coated glass flakes of Example 4, in which a rutile-type titanium oxide layer was formed on the surface. The coated glass flakes of Example 4 exhibited a silver interference color. Using the coated glass flakes of Example 4, a test piece of a resin molded product of Example 4 was obtained using the same method as in Example 1.

[0065] [Comparative Example 1] A pigment (GT5090RS, manufactured by Nippon Sheet Glass Co., Ltd.) in which a flake glass substrate (average particle size: 100 μm, average thickness: 5 μm) was coated with silver-colored rutile-type titanium oxide was used as the coated glass flake of Comparative Example 1. Using the coated glass flake of Comparative Example 1, a test piece of a resin molded product of Comparative Example 1 was obtained in the same manner as in Example 1.

[0066] [Comparative Example 2] In the glass flake molding process, glass flakes with an average thickness of 5 μm were obtained. Next, in the crushing and classification process, glass flakes with an average particle size of 200 μm were obtained. Except for these, the same method as in Example 1 was used to obtain coated glass flakes of Comparative Example 2, in which a rutile-type titanium oxide layer was formed on the surface. The coated glass flakes of Comparative Example 2 exhibited a silver interference color. Using the coated glass flakes of Comparative Example 2, a test piece of a resin molded product of Comparative Example 2 was obtained using the same method as in Example 1.

[0067] [Comparative Example 3] A pigment (GT1080RS, manufactured by Nippon Sheet Glass Co., Ltd.) in which a flaky glass substrate (average particle size: 90 μm, average thickness: 1.3 μm) was coated with silver-colored rutile-type titanium oxide was used as the coated glass flake of Comparative Example 3. Using the coated glass flake of Comparative Example 3, a test piece of a resin molded product of Comparative Example 3 was obtained by the same method as in Example 1.

[0068] Comparative Example 4 A pigment (GT1200RS, manufactured by Nippon Sheet Glass Co., Ltd.) in which a flaky glass substrate (average particle size: 200 μm, average thickness: 1.3 μm) was coated with silver-colored rutile-type titanium oxide was used as the coated glass flake of Comparative Example 4. Using the coated glass flake of Comparative Example 4, a test piece of a resin molded product of Comparative Example 4 was obtained by the same method as in Example 1.

[0069] [Comparative Example 5] In the glass flake molding process, glass flakes with an average thickness of 20 μm were obtained. Next, in the crushing and classification process, glass flakes with an average particle size of 100 μm were obtained. Except for these, the same method as in Example 1 was used to obtain coated glass flakes of Comparative Example 5, in which a rutile-type titanium oxide layer was formed on the surface. The coated glass flakes of Comparative Example 5 exhibited a silver interference color. Using the coated glass flakes of Comparative Example 5, a test piece of a resin molded product of Comparative Example 5 was obtained using the same method as in Example 1.

[0070] [Comparative Example 6] In the glass flake molding process, glass flakes with an average thickness of 12.5 μm were obtained. Then, in the crushing and classification process, glass flakes with an average particle size of 100 μm were obtained. Except for these, the same method as in Example 1 was used to obtain coated glass flakes of Comparative Example 6, in which a rutile-type titanium oxide layer was formed on the surface. The coated glass flakes of Comparative Example 6 exhibited a silver interference color. Using the coated glass flakes of Comparative Example 6, a test piece of a resin molded product of Comparative Example 6 was obtained using the same method as in Example 1.

[0071] <Measurement of average particle size> The average particle size of the coated glass flakes was measured using a laser diffraction particle size meter (Microtrac MT3300EXII, manufactured by Microtrac Bell Co., Ltd.) to measure the particle size distribution of the coated glass flakes, and the particle size (D50) corresponding to 50% cumulative volume was read from the measurement results. The results are shown in Table 2.

[0072] <Measurement of average thickness> The average thickness of the coated glass flakes was measured by measuring the optical path difference between direct light (light not affected by a phase object) and light transmitted through the coated glass flakes using an interference microscope (INTERPHAKO, manufactured by CARLZEISSJENA) for 100 pieces of the coated glass flakes, and calculating the thickness. The total thickness was then divided by the number of pieces measured to obtain an average value. The results are shown in Table 2.

[0073] <Calculation of Aspect Ratio> The aspect ratio was calculated as the ratio of the average particle size to the average thickness of the coated glass flakes. The results are shown in Table 2.

[0074] <Evaluation of Appearance> The appearance of the resin molded product was evaluated by visually observing the appearance of weld lines on the surface of the resin molded product test pieces. The results are shown in Table 2. A to D in Table 2 mean the following: A: Almost no weld lines were observed B: No linear weld lines were observed, but some weld lines were faintly observed C: A faint linear weld line was observed D: A dark, clear linear weld line was observed

[0075] <Evaluation of brilliance> The brilliance of the resin molded article was evaluated by visually observing the surface of the test piece of the resin molded article. The results are shown in Table 2. In Table 2, a to d mean the following: a: There was a strong brilliance b: There was a brilliance c: The brilliance was somewhat low d: The brilliance was low

[0076]

[0077] As shown in Table 1, the resin molded products of Examples 1 to 4, in which the coated glass flakes had an average particle size of 90 μm or more, an average thickness of more than 5 μm and less than 15 μm, and an aspect ratio of 10 to 30, exhibited excellent appearance and excellent brilliance. In the resin molded products of Comparative Examples 1 to 4, the average thickness of the coated glass flakes was too small, which is presumably why the coated glass flakes broke during kneading and the number of particles increased, resulting in noticeable weld lines and a decrease in brilliance. In the resin molded products of Comparative Examples 5 and 6, the broken coated glass flakes were suppressed during kneading, but the average thickness of the coated glass flakes was too large, which is presumably why the number of particles decreased and the brilliance decreased.

[0078] As can be seen from a comparison between Examples 1 and 2 and Examples 3 and 4, when the average particle size was more than 100 μm, the glittering effect was particularly excellent.

[0079] As can be seen from a comparison between Examples 1 and 2 and Examples 3 and 4, when the aspect ratio was 10 or more and less than 20, the appearance was particularly excellent.

[0080] When the flaky particles of the present invention are used as a filler for imparting a lustrous appearance to a resin composition, they can improve the appearance of the resulting resin molded article, and are therefore applicable to a variety of uses.

Claims

1. A shiny pigment comprising flaky particles and a metal oxide layer formed on at least a portion of the surface of the flaky particles, the shiny pigment having an average particle size of 90 μm or more and an average thickness of more than 5 μm and not more than 15 μm, and the ratio of the average particle size to the average thickness being 10 or more and 30 or less.

2. The bright pigment according to claim 1, wherein the flaky particles are made of glass.

3. The bright pigment according to claim 1, wherein the average particle size is 220 μm or less.

4. A resin composition comprising a luster pigment and a matrix resin, wherein the luster pigment comprises flaky particles and a metal oxide layer formed on at least a portion of the surface of the flaky particles, the luster pigment has an average particle size of 90 μm or more and an average thickness of more than 5 μm and not more than 15 μm, and the ratio of the average particle size to the average thickness of the luster pigment is 10 or more and 30 or less.

5. The resin composition according to claim 4, wherein the flaky particles are made of glass.

6. The resin composition according to claim 4, wherein the average particle size of the bright pigment is 220 μm or less.

7. The resin composition according to claim 4, wherein the matrix resin is a thermoplastic resin.

8. The resin composition according to claim 7, wherein the thermoplastic resin is at least one selected from the group consisting of polypropylene, polyethylene, polybutylene terephthalate, polyethylene terephthalate, polycarbonate, polystyrene-based resin, styrene-acrylonitrile copolymer resin, polyacrylate, styrene-butadiene-acrylonitrile copolymer resin, polyarylene sulfide, polyphenylene sulfide, polyacetal, polyamide, polyamideimide, liquid crystal polymer, polyether ether ketone, and polyetherimide.

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