JPH04170323A - Superfine particle yellow pigment and its production - Google Patents

Abstract

PURPOSE:To obtain a superfine yellow pigment excellent in design ability, durability and dispersibility by mixing superfine particles of water-contg. tita nium oxide, antimony source, and chromium or nickel source, calcining the mixture at specified temp. and then pulverizing. CONSTITUTION:The superfine particle yellow pigment essentially consists of oxides of titanium, antimony, and chromium or nickel, and has 0.01-0.1mum average single particle size determined by electron microscopy. The compsn. of this yellow pigment is, by wt.%, 6-30% Sb2O3, 3-15% Cr2O3 or NiO, and the balance substantially titaminum oxide. The pigment is produced by mixing superfine particles of water-contg. titanium oxide, antimony source, and chromium or nickel source, calcining the mixture at 700-1000 deg.C, and then pulverizing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an ultrafine yellow pigment having excellent design properties, durability and dispersibility, and a method for producing the same.

The ultrafine yellow pigment of the present invention is used as a coloring pigment for paints, inks, plastics, etc., and is particularly useful for high-grade industrial paints such as automotive paints.

[Conventional technology]

Recently, ultrafine titanium dioxide particles with an average particle size of 0.01 to 0.1 μm have been blended into resin media with metal flake pigments such as aluminum flakes or metallic luster pigments such as titanium mica to achieve excellent down-flop properties. It has been proposed to provide a coating composition with excellent design properties.

[Problem that the invention seeks to solve]

In the coating composition, by blending a colored fine powder instead of a white powder such as ultrafine titanium dioxide,
It is expected that the unique color of the downflow and knob characteristics will be obtained. The present inventors investigated the use of fine organic pigments as colored fine powders, and found that some organic pigments have the durability to be used in high-grade industrial paints such as automotive paints. , very expensive;
In addition, the down-flop effect was small, so we changed to using inorganic colored pigments. Among inorganic colored pigments, we focused on titanium-based yellow pigments, which have a particularly high refractive index, and investigated how to make them into fine particles.
It is necessary to sinter raw materials such as titanium, antimony, chromium, nickel, cobalt, and tungsten at high temperatures of 900 to 1200'C, and even if the grinding is strengthened, coarse particles of 0.2 to 1.0 μm will result. , average particle size or hook 0
It was difficult to obtain ultrafine particles with a size of 1 to 0.1 μm.

[Means for solving problems]

In order to make the titanium-based yellow pigment into fine particles, the present inventors extensively studied its composition, the blending ratio of each component, the type of titanium source, firing conditions, etc.

As a result, (1) whether it is preferable to use titanium as the main component and antimony and chromium or nickel as the remaining components from the viewpoint of color, and even if the blended amounts of these components are varied, the difference is 0.01 to 0.1 μm. (2) Ultrafine hydrous titanium oxide obtained by neutralizing and hydrolyzing an aqueous titanium tetrachloride solution can be obtained by selecting neutralizing hydrolysis conditions. Even when fired at low temperatures, it easily forms rutile crystals, and when this hydrous titanium oxide is used as a titanium source, mixed with other component raw materials, and fired, a deep yellow color of 0.01 to 0.0
．． Obtaining a yellow pigment with ultrafine particles of 1 μm (3)
) The present invention was completed based on the knowledge that if the surface of the hydrous titanium oxide is coated with an oxide of silicon or aluminum or a hydrous oxide before firing, it becomes easier to form fine particles. It is Sase Tachino.

That is, the present invention is as follows.

1. An ultrafine yellow pigment containing titanium, antimony, and chromium or nickel oxides as main components and having an average single particle diameter of 0.01 to 0.1 μm as measured by electron microscopy.

2. 6 to 3 using antimony oxide as 5b203
0 parts by weight, chromium or nickel oxide as Cr2O*
Or each contains 3 to 15 parts by weight as NiO,
2. The ultrafine yellow pigment according to claim 1, wherein the remainder is substantially a titanium oxide.

3. Aluminum, silicon, titanium on the particle surface,
2. The ultrafine yellow pigment according to claim 1, which is coated with a hydrous oxide or oxide of at least one element selected from the group of zirconium, tin, and antimony.

4. The ultrafine yellow pigment according to claim 1 or 3, wherein the particle surface is coated with at least one organic compound selected from the group of polyhydric alcohols, alkanolamines, and organosilicon.

5. A method for producing an ultrafine yellow pigment, which comprises mixing ultrafine hydrous titanium oxide, an antimony source, and a chromium or nickel source, firing at a temperature of 700 to 1000°C, and then pulverizing.

6. An aqueous solution of antimony chloride, a water-soluble salt solution of chromium or nickel is added to an aqueous dispersion of ultrafine particles of hydrous titanium oxide, and the mixture is neutralized with an alkali and precipitated on the surface of the hydrous titanium oxide, followed by heating at a temperature of 700 to 1000°C. 6. The method for producing an ultrafine yellow pigment according to claim 5, wherein the ultrafine yellow pigment is calcined and pulverized.

7. The method for producing an ultrafine yellow pigment according to claim 5, wherein the antimony source is antimony oxide and the chromium or nickel source is a sulfate thereof.

8. Add aluminum to the aqueous dispersion of ultrafine yellow pigment,
After adding a water-soluble salt of at least one element selected from the group of silicon, titanium, zirconium, tin and antimony, it is neutralized by adding an acid or an alkali, and is precipitated on the surface of the yellow pigment, followed by fractionation. 6. The method for producing an ultrafine yellow pigment according to claim 5, which comprises the steps of: , drying, and pulverizing.

9. Metallic or pearl paint containing 1 to 20% by weight of ultrafine yellow pigment.

The ultrafine yellow pigment of the present invention has titanium, antimony, and each oxide of chromium or nickel as its main components, and has an average single particle diameter of 0.01 to 0.1μ by electronic button microscopy.
It belongs to m. Usually, antimony oxide is 5b2
6 to 30 parts by weight, preferably 8 to 25 parts by weight as 0s, chromium or nickel oxide is added to Cr2O3 or N
3 to 15 parts by weight each as iO, preferably 4 to 12
Part by weight, the remainder consists essentially of titanium oxide, and if necessary, very small amounts of lithium, sodium,
It may also contain oxides such as phosphorus and calcium. These ultrafine yellow pigments exhibit a deep yellow color, and can be blended into a resin medium with metal flake pigments such as aluminum flakes or metallic luster pigments such as titanium mica to achieve unique color down-flop properties. It is possible to produce a paint composition such as a metallic paint or a pearl paint that exhibits excellent design properties.

The ultrafine yellow pigment of the present invention may be further coated with a hydrous oxide or oxide of at least one element selected from the group of aluminum, silicon, titanium, zirconium, tin, and antimony, polyhydric alcohol, or alkanolamine. and organosilicon.

The ultrafine yellow pigment having such a coating has excellent dispersibility and durability in a resin medium, and can exhibit more preferable down-flop properties in the above-mentioned coating composition. The coating amount is 1 to 30% by weight of aluminum as Al2O, 1 to 20% by weight of silicon as 5in2, and oxides (TiO□, Zr02, SnO□, 5b202
) is suitably 0.3 to 15% by weight. In the case of coating with an organic compound, the appropriate solid content is 0.3 to 5% by weight based on the yellow pigment of the core.

In the production method of the present invention, a titanium source, an antimony source, and a chromium source or nickel source are mixed and
A yellow pigment can be obtained by firing at a temperature of 0°C. The present invention is particularly characterized in that ultrafine particles of hydrated titanium oxide are used as the titanium source. This is a micro titania sol with a rutile crystal structure, and it is a micro hydrous titanium oxide sol that exhibits a rutile crystal peak when measured by X-ray diffraction, and its average crystallite size is normally 50 to 120. belongs to. For example, a titanium tetrachloride aqueous solution is mixed with ammonia water to pH 7~
After aging the colloidal amorphous hydrous titanium oxide obtained by neutralization in step 8, or heat-treating the amorphous hydrous titanium oxide with metatitanic acid or orthotitanic acid in an aqueous sodium hydroxide solution, hydrochloric acid is added. It can be obtained by heat treatment in a solution or by heating and hydrolyzing an aqueous titanium tetrachloride solution. In the present invention, such a fine titania sol having a rutile crystal structure can be used as it is or after drying and pulverizing it as finely as possible.

Antimony sources include antimony trioxide, antimony pentoxide, antimony pentachloride, antimony trichloride, antimony soda, etc.; chromium sources include chromium oxide, dichromium chloride, basic dichromium sulfate,
Nichrome sulfate, etc. can be used, and as a nickel source, nickel sulfate, nickel carbonate, nickel nitrate, nickel chloride, etc. can be used.

When mixing the raw materials for each of the above-mentioned components, for example, when powder is used as the raw material, it is sufficient to simply mix them. In addition, when using a compound solution of each component as a raw material, for example, add the compound solution of each component to a slurry of ultrafine particles of hydrated titanium oxide, and neutralize with acid or alkali to coat the surface of the hydrated titanium oxide. This can be done by precipitating each component, filtering and washing.

The mixing ratio of each component is as follows: ultrafine particles of hydrated titanium oxide (Ti)
For 100 parts by weight of O□, the amount of antimony is 6 to 30 parts by weight as 5b203, preferably 8 to 25 parts by weight, and the amount of chromium or nickel is 3 to 15 parts by weight as Cr20z or NiO, preferably 4 to 12 parts by weight. In addition to these, for example, very small amounts of compounds such as lithium, sodium, phosphorus, and calcium may be mixed.

The raw material mixture obtained by mixing as above was mixed at 700 to 1
It is fired at a temperature of 000°C, preferably 800 to 950°C. Note that the raw material mixture may be in the form of a slurry, cake, or dry powder. Upon firing, each component undergoes a solid phase reaction and develops a color, yielding the yellow pigment of the present invention. In the present invention, ultrafine particles of hydrous titanium oxide are used as a titanium source, and the fired product is processed using a microniser, shet mill,
By pulverizing with a dry pulverizer such as a roller mill, knock-on mill, or sample mill, it is easy to reduce the average single particle size to 0. It can be made into an ultrafine yellow pigment having a diameter of 1 to 0.1 μm. Note that the ultrafine particles of hydrous titanium oxide used as a titanium source in the present invention tend to cause particle growth and sintering during firing, and in order to suppress this, silicon compounds and/or aluminum compounds are fired. It is desirable to have it present as a processing aid during firing. In this case, the auxiliary agent may be added to the component raw material, the hydrated titanium oxide and the auxiliary agent may be mixed in advance, or the surface of the hydrated titanium oxide may be coated with the auxiliary agent in advance. It is possible, but the most effective method is coating.

The amount of the auxiliary agent to be used varies depending on the mixing ratio of the component raw materials, firing treatment conditions, etc., and may not be further defined.
It is 1 to 10 parts by weight, preferably 3 to 8 parts by weight. Specifically, the calcination processing aid used is, for example, an inorganic silicon compound such as colloidal silica or a water-soluble silicate such as sodium silicate.
Examples of organosilicon compounds include silicone oil and Nran coupling agents; examples of aluminum compounds include aluminum sulfate, aluminum nitrate, aluminum chloride,
Examples include water-soluble aluminum salts such as sodium aluminate.

Firing can be carried out using an electric furnace, a stationary furnace such as a tunnel kiln, or an internal combustion or external combustion rotary kiln.

In the present invention, the surface of the ultrafine yellow pigment thus obtained is made of aluminum, silicon, titanium,
By coating with a hydrous oxide or oxide of at least one element selected from the group of zirconium, tin and antimony, and/or at least one organic compound selected from the group of polyhydric alcohols, alkanolamines and organosilicon. By coating with the resin, the dispersibility and durability in the resin medium can be further improved. The ultrafine yellow pigment obtained in this way is
More favorable down-flop properties can be exhibited in coating compositions such as metallic paints and pearlescent paints. The amount of aluminum covered is A compared to the yellow pigment of the core.
1 to 30% by weight as l2O3, 1 to 20% by weight as 5iOz for silicon, and oxide (T
102, ZrL, SnO□, 5b21L) as 0.
3 to 15% by weight is appropriate. In the case of coating with an organic compound, the solid content of each compound is suitably 0.3 to 5% by weight based on the yellow pigment of the core.

〔Example〕

Example 1 500 ml of an aqueous titanium tetrachloride solution with a concentration of 200 g/l as Ti0□ and an aqueous sodium hydroxide solution with a concentration of loOg/l as Na2O were added in parallel to water so as to maintain the pl of the system at 5-9. The obtained ultrafine hydrated titanium oxide precipitate was filtered and washed, and then dispersed again in water to form a titanium dioxide slurry having a concentration of 100 g/l as TiO2. Add 10% SiO□ to this slurry.
Add 30 ml of an aqueous sodium silicate solution with a concentration of 0 g/l, then adjust to p) 1.7 by adding sulfuric acid, filter,
After washing, hydrous titanium oxide coated with 3% by weight of a silicon compound was obtained as 5i02.

The hydrous titanium oxide is dispersed in water to form 2 as TiO□.
After making titanium dioxide slurry with a concentration of 00g/l, Cr
Chromium sulfate aqueous solution with a concentration of 100 g/l as 20i8
0ml and 20g of 5b20s powder were added, followed by the addition of ammonia aqueous solution to adjust the pH to 7. The obtained precipitate was calcined in an electric furnace at 900°C for 5 hours, allowed to cool, and dry-pulverized to have an average single particle diameter of 0 as determined by electron microscopy.
．． An ultrafine yellow pigment with a diameter of 0.03 μm was obtained.

Example 2 The ultrafine yellow pigment powder obtained in Example 1 was dispersed in water to form a slurry with a solid content concentration of 100 g/l, wet-pulverized, and then heated to 70°C. A 2% by weight aqueous stannous chloride solution was added as SnO□ based on the solid content of the slurry, then a 4% by weight zirconium sulfate aqueous solution was added as ZrO□, and then an aqueous sodium hydroxide solution was added to adjust the pH to 7. After adjusting, further set 10 as A1□03.
A system of 1% sodium aluminate aqueous solution and sulfuric acid
Hydrous oxides of tin, zirconium and aluminum were precipitated by parallel additions to maintain H between 7 and 10.

Thereafter, the mixture was filtered, washed, dried, and then dry-pulverized to obtain an ultrafine yellow pigment having an average single particle diameter of 0.03 μm as determined by electron microscopy.

Example 3 The same procedure as in Example 2 was performed except that the aqueous solution of stannous chloride and the aqueous solution of zirconium sulfate were not added, that is, the hydrous oxides of tin and zirconium were not precipitated, and the average single oxide was determined by electron microscopy. Particle size is 0.0
An ultrafine yellow pigment with a diameter of 3 μm was obtained.

Example 4 An ultrafine yellow pigment having an average single particle diameter of 0.05 μm as measured by electron microscopy was obtained by the same treatment as in Example 2, except that the ultrafine particles of hydrous titanium oxide were not coated with a silicon compound. .

Example 5 An ultrafine yellow pigment with an average single particle diameter of 0.05 μm as determined by electron microscopy was obtained by the same treatment as in Example 3 except that the ultrafine particles of hydrous titanium oxide were not coated with a silicon compound. .

Example 6 The ultrafine yellow pigment obtained in Example 1 was dispersed in water to form a slurry with a solid content concentration of 100 g/l.

This slurry was heated to 60°C, and an aqueous solution of sodium silicate containing 4% by weight of SiO□ based on the solid content was added over 30 minutes, then heated to 80°C, and
Stir for 60 minutes and add sulfuric acid to 4 pl.
A dense coating layer of hydrous oxide of silicon was formed on the surface of the fine powder particles. After subsequent aging for 30 hours, a 5% by weight aqueous sodium aluminate solution was added as Al2O3, and then sulfuric acid was added until the pH of the system reached 7 to precipitate the hydrous oxide of aluminum. Thereafter, the mixture was filtered, washed, dried, and then dry-pulverized to obtain an ultrafine yellow pigment having an average single particle diameter of 0.03 μm as determined by electron microscopy.

Example 7 In Example 1, 40ml of nickel sulfate aqueous solution (100g/l as NiO) was added instead of chromium sulfate aqueous solution, the amount of 5b20s powder added was changed to 15g, and the firing temperature in the electric furnace was set to 850°C. The average single particle diameter by electron microscopy was 0.
An ultrafine yellow pigment with a diameter of 0.04 μm was obtained.

Example 8 In Example 2, 40ml of nickel sulfate aqueous solution (100g/l as NiO) was added instead of chromium sulfate aqueous solution, the amount of 5bzO3 powder added was changed to 15g, and the firing temperature in the electric furnace was set to 850'C. The average single particle diameter by electron microscopy was 0 after the same treatment except that
．． An ultrafine yellow pigment having a particle diameter of 0.04 μm was obtained.

Example 9 In Example 3, 40ml of nickel sulfate aqueous solution (100g/l as NiO) was added instead of the chromium sulfate aqueous solution, 5b2o, the amount of powder added was changed to 15g, and the firing temperature in the electric furnace was changed to 850°C. The average single particle diameter by electron microscopy was 0.
An ultrafine yellow pigment with a diameter of 0.04 μm was obtained.

Example 10 In Example 4, sulfuric acid-y was used instead of the chromium sulfate aqueous solution.
The average was determined by electron microscopy using the same process except that 40 ml of Kel aqueous solution (100 g/l as N10) was added, the amount of 5b2o added was changed to 15 g, and the firing temperature in the electric furnace was set to 850'C. Single particle size or 0
．． An ultrafine yellow pigment with a diameter of 0.04 μm was obtained.

Example 11 In Example 5, 40ml of nickel sulfate aqueous solution (100g/l as NiO) was added instead of chromium sulfate aqueous solution, the amount of 5b20j powder added was changed to 15g, and the firing temperature in the electric furnace was set to 850°C. The average single particle diameter was determined by electron microscopy using the same procedure except that
An ultrafine yellow pigment with a diameter of 7 μm was obtained.

Example 12 In Example 6, 40ml of nickel sulfate aqueous solution (log/l as NiO) was added instead of chromium sulfate aqueous solution, the amount of 5b203 powder added was changed to 15g, and the firing temperature in the electric furnace was set to 850°C. The average single particle diameter by electron microscopy was 0.
An ultrafine yellow pigment with a diameter of 0.07 μm was obtained.

Comparative Example 1 Metatitanic acid was produced by heating and hydrolyzing 500 ml of an aqueous titanyl sulfuric acid solution at a concentration of 200 g/l as TlO2 at the boiling point for 10 hours. This product was filtered and washed, and the resulting cake was dispersed in water to obtain 200%
The slurry had a concentration of g/l. Add Cr to this slurry.
80 ml of an aqueous chromium sulfate solution with a concentration of IOQ g/l including 2O+ and 20 g of 5b203 powder were added, followed by the addition of an ammonia aqueous solution to adjust the pH to 7. After filtering and washing the obtained precipitate, it was calcined in an electric furnace at 900''C for 5 hours, allowed to cool, and dry-pulverized to produce a yellow pigment with an average single particle diameter of 0.20 μm as determined by electron microscopy. I got it.

Comparative Example 2 A yellow pigment having an average single particle diameter of 0.35 μm as measured by electron microscopy was obtained by carrying out the same process as in Comparative Example 1 except that the firing temperature was changed to 1150°C.

Comparative Example 3 In Comparative Example 1, 40 ml of nickel sulfate aqueous solution (100 g/l as NiO) was added instead of the chromium sulfate aqueous solution, the amount of sb, o□ powder added was changed to 15 g, and the firing temperature in the electric furnace was set to 850 ml. The average single particle diameter by electron microscopy was 0.
A yellow pigment with a diameter of 17 μm was obtained.

Test Example The performance of the ultrafine yellow pigment of the above Example and the yellow pigment of Comparative Example was tested, and the results shown in Tables 1 and 2 were obtained.

Table 1 (Ti-3b-Cr system) Table 2 (Ti-3b-Ni system) The performance evaluations in Tables 1 and 2 were performed as follows.

(1) Knead 2 g of the color sample with 2 rnl of linseed oil, dilute 2 g of the resulting paste with 5 g of clear lacquer (nonvolatile content 27%), and apply it on a white board with a 10 mil applicator.
After air drying, the L value, a value, and b value were measured using a color difference meter.

(2) 7.5g of down-flop sample was mixed with acrylic resin/butylated melamine resin =
8/2 (weight ratio) mixed varnish56. After mixing it into Ig (non-volatile content 53%) and dispersing it with a paint shaker (manufactured by Red Devil Co., Ltd., #5110) to form a paint, aluminum paste was added (sample/Al2 = 1/1 in weight ratio).
Mix well to obtain metallic paint. This paint was applied to a steel plate to a dry film thickness of approximately 60μ, and heated to 130°C.
Bake for 30 minutes. This coated plate was visually observed at different angles and evaluated based on color change. ◎ indicates a large change in color, O indicates a medium change in color, △ indicates a small change in color, and × indicates no change in color.

(3) Durability Zinc phosphate treated steel plate (7CO] x 15cm) is coated with an epoxy/urethane resin paint, then a polyester/melamine resin paint as an intermediate coat, and then the metallic paint described in the previous item (2) is applied. was applied so that the dry film thickness was about 60μ, and then an acrylic resin-based clear paint was applied.

Subsequently, a test plate was prepared by baking at 130°C for 30 minutes. This test plate was exposed to accelerated exposure using an accelerated exposure tester (12 minutes of precipitation during 60 minutes of irradiation, black panel temperature 63±3°C)
L. After immersing in hot water at 50°C for 3 days every 400 hours, it was air-dried and the coating film was peeled off using cellophane tape for evaluation. ◎ indicates no peeling after 1200 hours, ○ indicates no peeling after 800 hours and peeling occurred after 1200 hours, and △ indicates no peeling after 400 hours and peeling occurred after 800 hours.

(4) Dispersibility The dispersibility was evaluated based on the paint shaker dispersion time of the paint before adding the aluminum paste in (2) and the degree of crushing of the coarse particles. ◎ indicates that there are no coarse particles in 5 minutes, ○ indicates that there are 1 to 3 coarse particles in 5 minutes, and △ indicates that there are 5 to 15 coarse particles in 5 minutes.

〔Effect of the invention〕

The ultrafine yellow pigment of the present invention is mainly composed of titanium, antimony, and chromium or nickel oxides, and has an average single particle diameter of 0.01 to 0.1 μm as measured by electron microscopy.
It has a deep yellow color and can be blended into a resin medium with a metal flake pigment such as aluminum flakes or a metallic luster pigment such as titanium mica to create a design that exhibits a unique color down-flop property. It can be used as an excellent coating composition. Further, the ultrafine yellow pigment of the present invention further has a coating of a hydrous oxide or oxide of at least one element selected from the group of aluminum, silicon, titanium, zirconium, tin, and antimony on its surface, and (or) It has a coating of at least one organic compound selected from the group of polyhydric alcohols, alkanolamines, and organosilicon, and has excellent dispersibility and durability in resin media.

Claims (1)

[Scope of Claims] 1. An ultrafine yellow pigment containing titanium, antimony, and chromium or nickel oxides as main components and having an average single particle diameter of 0.01 to 0.1 μm as measured by electron microscopy. 2. 6 to 3 using antimony oxide as Sb_2O_5
0 parts by weight, chromium or nickel oxide as Cr_2O
2. The ultrafine yellow pigment according to claim 1, which contains 3 to 15 parts by weight of _3 or NiO, and the remainder is substantially a titanium oxide. 3. The ultrafine yellow pigment according to claim 1, wherein the particle surface is coated with a hydrous oxide or oxide of at least one element selected from the group of aluminum, silicon, titanium, zirconium, tin, and antimony. 4. The ultrafine yellow pigment according to claim 1 or 3, wherein the particle surface is coated with at least one organic compound selected from the group of polyhydric alcohols, alkanolamines, and organosilicon. 5. A method for producing an ultrafine yellow pigment, which comprises mixing ultrafine hydrous titanium oxide, an antimony source, and a chromium or nickel source, firing at a temperature of 700 to 1000°C, and then pulverizing. 6. Add an aqueous antimony chloride solution and a water-soluble salt solution of chromium or nickel to an aqueous dispersion of ultrafine particles of hydrous titanium oxide, neutralize with alkali, precipitate on the surface of the hydrous titanium oxide, and heat at 700 to 1000°C. 6. The method for producing an ultrafine yellow pigment according to claim 5, wherein the ultrafine yellow pigment is calcined at a temperature of . 7. The method for producing an ultrafine yellow pigment according to claim 5, wherein the antimony source is antimony oxide and the chromium or nickel source is a sulfate thereof. 8. Add aluminum to the aqueous dispersion of ultrafine yellow pigment,
After adding a water-soluble salt of at least one element selected from the group of silicon, titanium, zirconium, tin and antimony, it is neutralized by adding an acid or an alkali, and is precipitated on the surface of the yellow pigment, followed by fractionation. 6. The method for producing an ultrafine yellow pigment according to claim 5, which comprises the steps of: , drying, and pulverizing. 9. Metallic or pearl paint containing 1 to 20% by weight of ultrafine yellow pigment.