Light pigment and resin composition

Abstract

The brilliant pigment contains flake-like particles and a metal oxide layer formed on at least a portion of the surface of the flake-like particles. The brilliant pigment has an average particle diameter of 90 [mu] m or more, an average thickness of more than 5 [mu] m and 15 [mu] m or less, and a ratio of the average particle diameter to the average thickness of 10-30. The brilliant pigment is suitable for use as a filler for imparting a brilliant sensation to a resin composition, and can improve the appearance of a resin molded article containing the brilliant pigment. The resin composition includes a brilliant pigment and a matrix resin.

Description

Technical Field

[0001] This invention relates to glossy pigments and resin compositions. Background Technology

[0002] Generally, glossy pigments contain flake-like particles. Examples of these flake-like particles include mica, synthetic mica, talc, flake glass, flake silica, and flake bismuth oxychloride. Glossy pigments sometimes also contain a coating on the surface of these flake-like particles. This coating can be a single layer or a multilayer film. The layers constituting the coating can be, for example, metal oxide layers containing titanium dioxide, iron oxide, or metal layers such as silver, copper, or aluminum. Glossy pigments can be used alone, for example, as cosmetics or coating compositions, or as fillers to impart a glossy finish to resin compositions.

[0003] Patent Document 1 describes a method to suppress weld lines on the surface of molded articles by using metal-coated flake glass 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 added to the resin. Weld lines are linear marks that can form inside the injection molding die when molten resin flows, leading to poor appearance of the molded resin article. Particularly during the mixing or molding of the resin composition, fine particles generated by the destruction of flake-like particles easily form a low-particle-concentration layer near the leading edge of the molten resin flow inside the injection molding die. This low-particle-concentration layer forms an uneven layer at the confluence point of the molten resin flow. This uneven layer remains in the molded resin article as surface weld lines. Furthermore, weld lines can also contribute to a decrease in the strength of the molded resin article.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 3456252 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] The metallic pigment of Patent Document 1 is not easily destroyed when it is mixed into synthetic resin and molded, and can suppress the degradation of appearance caused by weld lines on the surface of the resulting resin molded article. However, according to the inventors' research, 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 flake-shaped glass, are applied to a glossy pigment in which a metal oxide layer is formed on the surface of flake-shaped particles, the desired effect cannot be obtained.

[0009] One object of the present invention is to improve glossy pigments suitable for use as fillers for imparting a glossy finish to resin compositions. Another object of the present invention is to improve the appearance of resin molded articles containing glossy pigments.

[0010] Methods for solving problems

[0011] This invention provides a glossy pigment from one aspect.

[0012] It comprises sheet-like particles and a metal oxide layer formed on at least a portion of the surface of the sheet-like particles.

[0013] The average particle size is greater than 90 μm, and the average thickness is greater than 5 μm and less than 15 μm.

[0014] The ratio of the average particle size to the average thickness is 10 or more and 30 or less.

[0015] The present invention provides a resin composition from another aspect thereof,

[0016] It contains glossy pigments and matrix resins.

[0017] The aforementioned glossy pigment comprises flake-like particles and at least a portion of a metal oxide layer formed on the surface of the flake-like particles.

[0018] The above-mentioned glossy pigments have an average particle size of 90 μm or more and an average thickness of 5 μm or less than 15 μm.

[0019] The ratio of the average particle size to the average thickness of the aforementioned glossy pigment is 10 or more and 30 or less.

[0020] Invention Effects

[0021] According to the present invention, a glossy pigment suitable for use as a filler for imparting a glossy feel to a resin composition is provided, which can further enhance the appearance of resin molded articles containing the glossy pigment. Attached Figure Description

[0022] Figure 1 This is a schematic diagram illustrating an example of an apparatus for manufacturing flake glass.

[0023] Figure 2 This is a schematic diagram illustrating another example of an apparatus for manufacturing flake glass. Detailed Implementation

[0024] Hereinafter, specific embodiments of the glossy pigment and resin composition of the present invention will be described. However, the following description is not intended to limit the present invention to the specific embodiments.

[0025] The glossy pigment of the first aspect of the present invention comprises flake-like particles and a metal oxide layer formed on at least a portion of the surface of the flake-like particles.

[0026] The average particle size is greater than 90 μm, and the average thickness is greater than 5 μm and less than 15 μm.

[0027] The ratio of the average particle size to the average thickness is 10 or more and 30 or less.

[0028] In a second aspect of the invention, for example in the glossy pigment of the first aspect, the aforementioned flake-like particles are formed from glass.

[0029] In the third aspect of the present invention, for example in the glossy pigment of the first or second aspect, the average particle size is 220 μm or less.

[0030] The resin composition of the fourth aspect of the present invention comprises a glossy pigment and a matrix resin.

[0031] The aforementioned glossy pigment comprises flake-like particles and at least a portion of a metal oxide layer formed on the surface of the flake-like particles.

[0032] The above-mentioned glossy pigments have an average particle size of 90 μm or more and an average thickness of 5 μm or less than 15 μm.

[0033] The ratio of the average particle size to the average thickness of the aforementioned glossy pigment is 10 or more and 30 or less.

[0034] In a fifth aspect of the invention, for example in the resin composition of the fourth aspect, the aforementioned sheet-like particles are formed from glass.

[0035] In the sixth aspect of the present invention, for example in the resin composition of the fourth or fifth aspect, the average particle size of the above-mentioned glossy pigment is 220 μm or less.

[0036] In the seventh aspect of the present invention, for example in the resin composition of any one of the fourth to sixth aspects, the matrix resin is a thermoplastic resin.

[0037] In the eighth aspect of the present invention, for example in the resin composition of the seventh aspect, the thermoplastic resin is selected from at least one 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, polyamide-imide, liquid crystal polymer, polyetheretherketone, and polyetherimide.

[0038] [The process of arriving at the present invention]

[0039] It was found that even when controlling the average shape ratio and average particle size of metallic pigments according to the teachings of Patent Document 1, the desired effect could not be obtained for glossy pigments with a metal oxide layer formed on the surface of flake-like particles. An investigation into the cause confirmed that the reflectivity of the metal oxide layer affects the visibility of weld lines on the surface of the resin molded article. Metal oxide layers containing titanium oxide, iron oxide, etc., have lower reflectivity compared to metal layers such as silver, copper, and aluminum. Therefore, when used in resin compositions, glossy pigments with a metal oxide layer formed on the surface of flake-like particles tend to produce more noticeable weld lines on the surface of the resulting resin molded article compared to glossy pigments with a metal layer formed on the surface of flake-like particles. The present invention was made considering the above circumstances, and its embodiments are described below.

[0040] [Glossy Pigments]

[0041] The glossy pigment of this embodiment comprises flake-like particles and a metal oxide layer formed on at least a portion of the surface of the flake-like particles. The glossy pigment has an average particle size of 90 μm or more, an average thickness of 5 μm or more and 15 μm or less, and an aspect ratio (average size to average thickness) of 10 or more and 30 or less.

[0042] In this specification, the term "flake-like particles" refers to, for example, scaly particles with an average particle size of 90 μm or more and an average thickness of 5 μm or less than 15 μm.

[0043] The average particle size of the glossy pigment in this embodiment refers to the volume accumulation (D50) of 50% of the particle size from the side with the smallest particle size in the particle size distribution of the glossy pigment determined by laser diffraction and scattering method.

[0044] The average thickness of the glossy pigment in this embodiment refers to the average value obtained by measuring the difference in the light path between direct light (light unaffected by phase objects) and light transmitted through the glossy pigment using an interference microscope on 100 pieces of glass coated with flakes, and then dividing the total thickness by the number of pieces measured.

[0045] The inventors have discovered that, in order to achieve excellent gloss in a glossy pigment comprising a metal oxide layer containing flake-like particles and at least a portion thereof formed on the surface of the flake-like particles, it is preferable to control the average particle size of the glossy pigment to be 90 μm or more, the average thickness to be greater than 5 μm and less than 15 μm, and the aspect ratio to be 10 or more and less than 30.

[0046] If the average particle size of the glossy pigment is 90 μm or more, the reflective area of ​​each glossy pigment increases, thus enhancing its glossiness. Furthermore, with a constant amount of glossy pigment, a smaller average thickness results in a greater number of glossy pigment particles. Therefore, by making the average thickness of the glossy pigment greater than 5 μm and less than 15 μm, the glossiness of the glossy pigment is further enhanced. Moreover, by controlling the average thickness of the glossy pigment to be greater than 5 μm and less than 15 μm, the increase in the mass of each glossy pigment is suppressed. As a result, the glossy pigment in the molten resin is less likely to settle during injection molding, reducing the force required for mixing. Consequently, breakage of the glossy pigment caused by mixing can be suppressed, and the accelerated wear and deterioration of molding equipment, including the screw, can be prevented.

[0047] In the metallic pigments described in Patent Document 1, the smaller the particle size of the metal-coated flake glass and the larger the aspect ratio (particle size / thickness), the more noticeable the weld lines become. To reduce the aspect ratio, the average thickness of the flake glass is increased to 15–31 μm (Table 1). Therefore, with a constant amount of glossy pigment, the reduced number of glossy pigment particles does not necessarily improve the gloss. Furthermore, in the metallic pigments described in Patent Document 1, when the average particle size of the metal-coated flake glass is increased to 90 μm or more, the increased mass of the flake glass leads to its tendency to settle in the molten resin. This increases the force required for mixing, potentially exacerbating wear on molding equipment, including the screw, and accelerating equipment deterioration.

[0048] On the other hand, the glossy pigment of this embodiment has 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 or more and less than 30, thereby maintaining excellent gloss while making the weld lines of the resin molded article inconspicuous.

[0049] In this embodiment, the average particle size of the glossy pigment is preferably 220 μm or less. By keeping the average particle size of the glossy pigment to 220 μm or less, it is easier to suppress the breakage of the glossy pigment caused by mixing. Therefore, the reduction in the glossiness of the glossy pigment is suppressed.

[0050] In this embodiment, the average particle size of the glossy pigment can be 100 μm or more, or even larger than 100 μm. If the average particle size of the glossy pigment is greater than 100 μm, the glossiness of the glossy pigment can be further increased.

[0051] In this embodiment, the average thickness of the glossy pigment is preferably greater than 5 μm and less than 10 μm. By making the average thickness of the glossy pigment greater than 5 μm and less than 10 μm, the increase in the mass of each glossy pigment is further suppressed. Therefore, the glossy pigment in the molten resin is less likely to settle during injection molding, and the glossy pigment can be dispersed with less force during mixing.

[0052] The aspect ratio of the glossy pigment in this embodiment is preferably 10 or more and 25 or less, more preferably 10 or more and less than 20, and even more preferably 10 or more and 15 or less. By controlling the aspect ratio within the above-mentioned range, weld lines in the resin molded article are less noticeable.

[0053] The average particle size and average thickness of the flake-like particles contained in the glossy pigment of this embodiment can satisfy the same numerical range as the average particle size and average thickness of the glossy pigment of this embodiment. However, the average particle size and average thickness of the flake-like particles are sometimes affected by the formation of the metal oxide layer. Therefore, the average particle size and average thickness of the flake-like particles contained in the glossy pigment are not necessarily the same as the average particle size and average thickness of the glossy pigment.

[0054] In the glossy pigment of this embodiment, examples of flake-shaped particles include mica, synthetic mica, talc, flake glass, flake silica, and flake bismuth oxychloride. Among these, flake glass is preferred because it can achieve higher transparency and further emphasizes high transparency when the amount of microparticles is low. That is, the flake-shaped particles can be formed from glass.

[0055] When the flake particles are flake-shaped glass, commonly known glass compositions can be used as the composition of the flake glass. However, from the viewpoint that at least a portion of the metal oxide layer is formed on the surface of the flake glass, a composition with excellent acid resistance is preferred as the composition of the flake glass; for example, C glass can be suitably used. A representative composition of C glass is shown below. The units of the following compositions are by mass%.

[0056] 65≤SiO2≤72

[0057] 1≤Al2O3≤7

[0058] 4≤CaO≤11

[0059] 0≤MgO≤5

[0060] 9≤(Na₂O+K₂O)≤17

[0061] 0≤B2O3≤8

[0062] 0≤ZnO≤6

[0063] Furthermore, when combined with a resin that has poor resistance to alkali components, a glass composition with excellent acid resistance and low alkali content is preferred. In this case, the composition, expressed as a percentage by mass, contains the following components:

[0064] 59≤SiO2≤65

[0065] 8≤Al2O3≤15

[0066] 47≤(SiO2-Al2O3)≤57

[0067] 1≤MgO≤5

[0068] 20≤CaO≤30

[0069] 0<(Li2O+Na2O+K2O)<2

[0070] 0≤TiO2≤5

[0071] A glass composition substantially free of B2O3, F, ZnO, BaO, SrO, and ZrO2 can be used. This glass composition is disclosed by the applicant in International Publication No. 2006 / 068255. Hereinafter, glass having this composition will be referred to as "TA glass." It should be noted that "substantially free of," does not include cases where it is unavoidably mixed in due to industrial raw materials; that is, it means unintentional inclusion. Specifically, it means that the content of each of B2O3, F, ZnO, BaO, SrO, and ZrO2 is less than 0.1% by mass (preferably less than 0.05% by mass, more preferably less than 0.03% by mass).

[0072] The composition of the flake-like 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 composition of low-dielectric glass disclosed by the applicant (for example, see Japanese Patent No. 6505950, Japanese Patent 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.

[0073] Flake-shaped glass can be produced, for example, using the so-called blowing method disclosed in Japanese Patent Publication No. 41-17148 and Japanese Patent Publication No. 45-3541, and the so-called rotation method disclosed in Japanese Patent Application Publication No. 59-21533 and Japanese Patent Application Publication No. 2-503669.

[0074] In the blown glass method, the following can be used: Figure 1The glass manufacturing apparatus shown includes a refractory furnace 12, a blowing nozzle 15, and a pressing roller 17. Molten glass preform 11 in the refractory furnace 12 is inflated into a balloon shape by gas fed into the blowing nozzle 15, forming a hollow glass membrane 16. The hollow glass membrane 16 is then crushed by the pressing roller 17, thereby obtaining flake glass 1. The thickness of the flake glass 1 can be controlled by adjusting the stretching speed of the hollow glass membrane 16 and the flow rate of the gas fed from the blowing nozzle 15.

[0075] In the rotation method, the following can be used: Figure 2 The glass manufacturing apparatus shown includes a pipe 21, a rotating cup 22, a set of annular plates 23, and an annular cyclone trap 24. Molten glass preform 11 is poured into the rotating cup 22 through the pipe 21, flows radially from the upper edge of the rotating cup 22 by centrifugal force, is drawn through the space between the annular plates 23 by airflow, and is guided into the annular cyclone trap 24. During its passage through the annular plates 23, the glass is cooled and solidified in the form of a thin film, and then broken into tiny flakes, thereby obtaining flake-shaped glass 1. The thickness of the flake-shaped glass 1 can be controlled by adjusting the spacing of the annular plates 23, the speed of the airflow, etc.

[0076] In the glossy pigment of this embodiment, a metal oxide layer covers at least a portion of the surface of the flake-like particles. Preferably, the metal oxide layer covers the entire surface of the flake-like particles.

[0077] The metal oxide layer can be formed using metal oxides such as titanium oxide or iron oxide. By coating thin flake particles with such a metal oxide layer, pearlescent pigments can be obtained.

[0078] The average thickness of the metal oxide layer is not particularly limited. Considering the achievement of a glossy finish and cost, the average thickness of the metal oxide layer is preferably set to 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.

[0079] When the glossy pigment of this embodiment is used as a filler to impart a glossy finish to the resin composition as described above, the appearance of the resulting resin molded article can be improved. That is, the glossy pigment of this embodiment can be used as a filler to impart a glossy finish to the resin composition. The resin composition may comprise a glossy pigment and a matrix resin.

[0080] [Resin Composition]

[0081] Next, the resin composition of this embodiment will be described. The resin composition of this embodiment includes a matrix resin and the glossy pigment of this embodiment described above. By including the glossy pigment of this embodiment having the above-described characteristics as a filler in the resin composition of this embodiment, the appearance of the obtained resin molded article can be improved.

[0082] The average particle size and average thickness of the glossy pigment contained in the resin composition of this embodiment meet the same numerical range as those of the glossy pigment in this embodiment described above. However, the average particle size and average thickness of the glossy pigment are sometimes affected by the dispersion into the resin composition, specifically by extrusion molding for obtaining a resin composition containing glossy pigment and / or injection molding for molding the resin composition to obtain a resin molded article. Therefore, the average particle size and average thickness of the glossy pigment in the resin composition are not necessarily the same as the average particle size and average thickness of the glossy pigment before dispersion into the resin composition.

[0083] The average particle size (D50) of the glossy pigment contained in the resin composition of this embodiment is obtained by heating the resin composition in an atmosphere of 625°C to remove components other than the glossy pigment, dispersing the resulting glossy pigment in water, and then measuring the value.

[0084] The average thickness of the glossy pigment contained in the resin composition of this embodiment is obtained as follows: the resin composition is heated in an atmosphere of 625°C to remove components other than the glossy pigment, and the thickness of more than 100 pieces of glossy pigment thus taken out is calculated using an interference microscope, and the average value is obtained by dividing the total thickness by the number of pieces measured.

[0085] The matrix resin may be, for example, a thermoplastic resin. The thermoplastic resin may be selected from at least one of polypropylene, polyethylene, polybutylene terephthalate, polyethylene terephthalate, polycarbonate, polystyrene-based resins, styrene-acrylonitrile copolymer resins, polyacrylates, styrene-butadiene-acrylonitrile copolymer resins, polyarylene sulfides, polyphenylene sulfides, polyacetals, polyamides, polyamide-imides, liquid crystal polymers, polyetheretherketones, and polyetherimides.

[0086] Polycarbonate is known to have poor tolerance to alkali components. If the carbonate bonds in polycarbonate come into contact with an alkali component, the decomposition of the resin is accelerated. Therefore, in the case of flake glass being TA glass with a low alkali content, polycarbonate can be used as the thermoplastic resin.

[0087] The content of glossy pigment in the resin composition is preferably 0.01% by mass or more and 3% by mass or less. By setting the content of glossy pigment to 3% by mass or less, the glossy pigment can be uniformly dispersed in the resin composition. In order to further suppress molding shrinkage, it is more preferable to set the content of glossy pigment to 0.1% by mass or more and 2% by mass or less.

[0088] The resin composition may also contain components other than the matrix resin and glossy pigments. 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), etc.) and ethylene-α-olefin-diene terpolymer elastomers (ethylene-propylene-ethylidene norbornene copolymer, ethylene-propylene-butadiene copolymer, ethylene-propylene-isoprene copolymer, etc.). Two or more thermoplastic elastomers may also be used in combination.

[0089] Resin molded articles made using the resin composition of this embodiment, by containing glossy pigments, can maintain an excellent gloss while making weld lines less noticeable, resulting in an excellent appearance.

[0090] Example

[0091] The present invention will be further described in detail below using examples. However, the present invention is not limited to the following examples. It should be noted that the examples shown below are examples of using flake glass as sheet particles; however, the present invention is not limited thereto, and mica, synthetic mica, flake bismuth oxychloride, etc., can also be used as sheet particles.

[0092] [Example 1]

[0093] <Forming process of flake glass>

[0094] Using TA glass with the composition shown in Table 1, and utilizing the reference... Figure 1 The blown glass method described herein produces flake-like glass. Specifically, TA glass is added to a melting bath heated to 1500°C and melted. Thin sheets of glass are formed while air is blown in through a nozzle, and these thin sheets are continuously drawn out using rollers. By adjusting the air flow rate and roller speed, flake-like glass with an average thickness of 10 μm is obtained.

[0095] [Table 1]

[0096]

[0097] <Pulverizing and Grading Process>

[0098] After the flake glass is crushed using a feather mill, it is classified to obtain flake glass with an average particle size of 100 μm.

[0099] <Pre-processing steps>

[0100] 1.2 kg of flake glass after the crushing and grading process was added to 8.4 L of ion-exchanged water to obtain a mixture. While stirring the mixture, dilute hydrochloric acid was added to adjust the pH to 1.5, resulting in a slurry. 0.6 L of a 0.5% (w / w) aqueous solution of tin(IV) chloride at room temperature was added to the slurry, and then dilute hydrochloric acid was added to adjust the pH to 1.5, resulting in a mixed slurry. After stirring the mixed slurry for 5 minutes, the flake glass was recovered from the mixed slurry by vacuum filtration. The recovered flake glass was washed with ion-exchanged water. This process was repeated to obtain flake glass subjected to tin-based pretreatment.

[0101] <Coating process of metal oxide layer>

[0102] 1.2 kg of pre-treated flake glass was mixed with ion-exchanged water to obtain 12 L of mixture. Hydrochloric acid was added to the mixture to adjust the pH to 1.0, while heating to 75 °C. Then, while stirring the mixture, a quantitative amount of titanium tetrachloride aqueous solution (16.5% by mass as Ti) was added, while sodium hydroxide was added to maintain a constant pH. The quantitative addition of titanium tetrachloride aqueous solution and sodium hydroxide continued until the rutile titanium oxide coating formed on the surface of the flake glass achieved a bright, silvery hue. After forming the target hue coating, the product was collected by vacuum filtration. The collected material was washed with pure water, dried at 180 °C, and then fired at 600 °C. This process was repeated to obtain the coated flake glass of Example 1 with a rutile titanium oxide layer formed on its surface.

[0103] <Molding process of resin molded products>

[0104] 1.0 part by weight of coated flake glass was mixed with 99 parts by weight of bisphenol A type polycarbonate resin (IUPILON S3000F, manufactured by Mitsubishi Engineering Plastics Co., Ltd.), and then extruded using an extruder (VS-30 type, manufactured by TANABE PLASTICS Machinery Co., Ltd.) at a barrel temperature of 290°C to granulate the mixture. After drying the resulting granules at 120°C for 5 hours, test pieces (length 80 mm × width 10 mm × thickness 5 mm) of the resin molded article of Example 1 were formed using an injection molding machine (PROMAT HM7, manufactured by Nissei Resin Kogyo Co., Ltd.) under the molding conditions described below.

[0105] (Molding conditions)

[0106] • Barrel temperature

[0107] Area No. 1: 290℃

[0108] Area No. 2: 305℃

[0109] Area No. 3: 310℃

[0110] Area No. 4: 300℃

[0111] NH (temperature of the injection molding machine head): 300℃

[0112] • Mold temperature: 100℃

[0113] • Maximum filling pressure: 60 kg / cm² 3

[0114] Screw speed: 150 rpm

[0115] [Example 2]

[0116] In the flake glass forming process, flake glass with an average thickness of 7 μm was obtained. In addition, coated flake glass of Example 2, with a rutile titanium oxide layer formed on its surface, was obtained using the same method as in Example 1. The coated flake glass of Example 2 exhibited a silvery interference color. Using the coated flake glass of Example 2, a test piece of the resin-molded article of Example 2 was obtained using the same method as in Example 1.

[0117] [Example 3]

[0118] In the crushing and grading process, flake-like glass with an average particle size of 200 μm was obtained. In addition, coated flake-like glass of Example 3, with a rutile titanium oxide layer formed on its surface, was obtained using the same method as in Example 1. The coated flake-like glass of Example 3 exhibited a silvery interference color. Using the coated flake-like glass of Example 3, a test piece of the resin-molded article of Example 3 was obtained using the same method as in Example 1.

[0119] [Example 4]

[0120] In the flake glass forming process, flake glass with an average thickness of 7 μm was obtained. Then, in the crushing and grading process, flake glass with an average particle size of 200 μm was obtained. In addition, coated flake glass of Example 4, with a rutile titanium oxide layer formed on its surface, was obtained using the same method as in Example 1. The coated flake glass of Example 4 exhibited a silvery interference color. Using the coated flake glass of Example 4, a test piece of the resin-molded article of Example 4 was obtained using the same method as in Example 1.

[0121] [Comparative Example 1]

[0122] As a comparative example 1, a pigment (GT5090RS, manufactured by Nippon Sheet Glass Co., Ltd.) was used to coat a flake-shaped glass substrate (average particle size: 100 μm, average thickness: 5 μm) with silver rutile titanium dioxide. Using the coated flake-shaped glass of comparative example 1, a test piece of the resin molded article of comparative example 1 was obtained using the same method as in example 1.

[0123] [Comparative Example 2]

[0124] In the flake glass forming process, flake glass with an average thickness of 5 μm was obtained. Then, in the crushing and grading process, flake glass with an average particle size of 200 μm was obtained. Otherwise, a coated flake glass of Comparative Example 2 with a rutile titanium oxide layer formed on its surface was obtained using the same method as in Example 1. The coated flake glass of Comparative Example 2 exhibited a silvery interference color. Using the coated flake glass of Comparative Example 2, a test piece of the resin molded article of Comparative Example 2 was obtained using the same method as in Example 1.

[0125] [Comparative Example 3]

[0126] As a comparative example 3, the coated flake glass used was a pigment (GT1080RS, manufactured by Nippon Sheet Glass Co., Ltd.) obtained by coating a flake glass substrate (average particle size: 90 μm, average thickness: 1.3 μm) with silver rutile titanium oxide. Using the coated flake glass of comparative example 3, a test piece of the resin molded article of comparative example 3 was obtained using the same method as in example 1.

[0127] [Comparative Example 4]

[0128] As a comparative example 4, the coated flake glass used was a pigment (GT1200RS, manufactured by Nippon Sheet Glass Co., Ltd.) obtained by coating a flake glass substrate (average particle size: 200 μm, average thickness: 1.3 μm) with silver rutile titanium oxide. Using the coated flake glass of comparative example 4, a test piece of the resin molded article of comparative example 4 was obtained using the same method as in example 1.

[0129] [Comparative Example 5]

[0130] In the flake glass forming process, flake glass with an average thickness of 20 μm was obtained. Then, in the crushing and grading process, flake glass with an average particle size of 100 μm was obtained. Otherwise, a coated flake glass of Comparative Example 5 with a rutile titanium oxide layer formed on its surface was obtained using the same method as in Example 1. The coated flake glass of Comparative Example 5 exhibited a silvery interference color. Using the coated flake glass of Comparative Example 5, a test piece of the resin molded article of Comparative Example 5 was obtained using the same method as in Example 1.

[0131] [Comparative Example 6]

[0132] In the flake glass forming process, flake glass with an average thickness of 12.5 μm was obtained. Then, in the crushing and grading process, flake glass with an average particle size of 100 μm was obtained. Otherwise, a coated flake glass of Comparative Example 6 with a rutile titanium oxide layer formed on its surface was obtained using the same method as in Example 1. The coated flake glass of Comparative Example 6 exhibited a silvery interference color. Using the coated flake glass of Comparative Example 6, a test piece of the resin molded article of Comparative Example 6 was obtained using the same method as in Example 1.

[0133] <Determination of average particle size>

[0134] The average particle size of the coated flake glass was determined using a laser diffractometer (Microtrac MT3300EXII, manufactured by Microtrac Bel). The particle size distribution of the coated flake glass was measured, and the value of the particle size (D50) corresponding to 50% of the volume was read based on the measurement results. The results are shown in Table 2.

[0135] <Determination of average thickness>

[0136] To determine the average thickness of the flake-coated glass, for 100 flake-coated glass pieces, an interference microscope (INTERPHAKO, Carl Zeiss Jena) was used to measure the optical path difference between direct light (light unaffected by phase objects) and light transmitted through the flake-coated glass. The thickness was calculated from this difference and then averaged by dividing the total thickness by the number of pieces measured. The results are shown in Table 2.

[0137] <Calculation of Aspect Ratio>

[0138] The aspect ratio was determined as the ratio of the average grain size to the average thickness of the coated flake glass. The results are shown in Table 2.

[0139] <Appearance Evaluation>

[0140] The appearance of the resin molded articles was evaluated by visually observing the weld lines on the surface of the test pieces. The results are shown in Table 2. A through D in Table 2 have the following meanings.

[0141] A: Weld lines are basically not visible.

[0142] B: Although no linear weld line can be observed, a portion of a weld line can be vaguely seen.

[0143] C: A faint linear weld line can be observed.

[0144] D: Dense and clearly visible linear weld lines

[0145] <Evaluation of glossiness>

[0146] The gloss of the resin molded products was evaluated by visually observing the surface of the test pieces. The results are shown in Table 2. The terms a to d in Table 2 have the following meanings.

[0147] a: It has a strong glossy feel

[0148] b: It has a glossy appearance

[0149] c: Glossiness is slightly low

[0150] d: Low glossiness

[0151] [Table 2]

[0152]

[0153] As shown in Table 1, the resin molded articles of Examples 1-4, which have a flake-like glass coating with an average particle size of 90 μm or more, an average thickness greater than 5 μm and less than 15 μm, and an aspect ratio of 10 or more and less than 30, exhibit both excellent appearance and excellent gloss. In the resin molded articles of Comparative Examples 1-4, it is presumed that because the average thickness of the flake-like glass coating is too small, breakage of the flake-like glass coating occurs during mixing, increasing the particle number and thus making weld lines more prominent, resulting in reduced gloss. In the resin molded articles of Comparative Examples 5-6, it is presumed that although breakage of the flake-like glass coating caused by mixing is suppressed, the average thickness of the flake-like glass coating is too large, thus reducing the particle number and decreasing the gloss.

[0154] A comparison of Examples 1-2 with Examples 3-4 shows that the glossiness is particularly excellent when the average particle size is greater than 100 μm.

[0155] A comparison of Examples 1-2 with Examples 3-4 shows that the appearance is particularly excellent when the aspect ratio is 10 or more and less than 20.

[0156] Industrial availability

[0157] When the flake-like particles of the present invention are used as fillers to impart a glossy finish to resin compositions, they can enhance the appearance of the resulting resin molded articles, and thus can be applied to a wide variety of uses.

Claims

1. A glossy pigment comprising flake-like particles and a metal oxide layer formed on at least a portion of the surface of the flake-like particles. The average particle size is greater than 90 μm, and the average thickness is greater than 5 μm and less than 15 μm. The ratio of the average particle size to the average thickness is 10 or more and 30 or less.

2. The glossy pigment according to claim 1, wherein, The sheet-like particles are formed from glass.

3. The glossy pigment according to claim 1, wherein, The average particle size is below 220 μm.

4. A resin composition comprising a glossy pigment and a matrix resin, The glossy pigment comprises flake-like particles and a metal oxide layer formed on at least a portion of the surface of the flake-like particles. The glossy pigment has an average particle size of 90 μm or more and an average thickness of 5 μm or less than 15 μm. The ratio of the average particle size to the average thickness of the glossy pigment is 10 or more and 30 or less.

5. The resin composition according to claim 4, wherein, The sheet-like particles are formed from glass.

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

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 selected from at least one of polypropylene, polyethylene, polybutylene terephthalate, polyethylene terephthalate, polycarbonate, polystyrene resin, styrene-acrylonitrile copolymer resin, polyacrylate, styrene-butadiene-acrylonitrile copolymer resin, polyarylene sulfide, polyphenylene sulfide, polyacetal, polyamide, polyamide-imide, liquid crystal polymer, polyetheretherketone, and polyetherimide.

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