Fine particle composite oxide yellow pigment and method for producing the same

Abstract

To provide a method for producing a fine particle composite oxide yellow pigment excellent in heat resistance, transparency and durability.SOLUTION: A method for producing a pseudobrookite-type fine particle composite oxide yellow pigment composed of Fe, Al and Ti comprises: producing a precipitate of Al in water by using a metal salt of Al and an alkali to obtain a first reaction liquid; producing a pigment precursor in water by using the first reaction liquid, a metal salt of Fe and Ti, and an alkali to obtain a second reaction liquid; and filtering the pigment precursor, washing with water, drying, and then firing the resultant at a temperature from 600°C to 900°C inclusive to obtain a fine particle composite oxide yellow pigment, where the average primary particle diameter of the fine particle composite oxide yellow pigment is 80 nm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a fine particle composite oxide yellow pigment having excellent transparency, heat resistance, and durability, and a method for producing the same. [Background technology]

[0002] Pigments have a wide range of uses, including as colorants in paints, inks, and building materials. Therefore, depending on the application, not only color but also heat resistance, weather resistance, and chemical resistance may be required. Inorganic yellow pigments generally have excellent heat and weather resistance, but in recent years, environmental concerns have led to a strong movement to avoid pigments containing Cd, Cr, or Pb, leading to their use being restricted. In the past, yellow pigments such as cadmium yellow and lead yellow were available, but they are now rarely used. Titanium yellow, a complex oxide-based pigment, contains metals such as Cr, Sb, or Ni, and pigments that do not contain these metals are in demand. On the other hand, organic yellow pigments exhibit vivid hues, but many of them have poor heat and weather resistance, limiting their use in certain applications. Additionally, goethite (α-FeOOH) is a yellow pigment that does not contain harmful metals and is in use, but this pigment has poor heat resistance, and when heated above 200°C, it dehydrates and turns into hematite (α-Fe2O3), turning it brown. For this reason, it may not be usable for some applications. This pigment is also available in fine particle form, but because it has the same chemical structure, it also has poor heat resistance. In this context, Fe2TiO5 (pseudobrookite) pigments have been proposed as heat-resistant pigments that do not contain harmful metals. However, even the finest of these pigments are submicron in size, and no nano-sized pigments with excellent transparency have been found.

[0003] Various attempts have been made to develop yellow pigments made of composite oxides of Fe and Ti. For example, Patent Document 1 discloses a yellow pigment made of a mixture of pseudobrookite with Al as a solid solution and rutile titanium oxide. This pigment is obtained by adding iron salt and aluminum salt to hydrous titanium oxide, neutralizing with an alkali, and then calcining the mixture, and the particle size of this pigment is in the submicron range. Patent Document 2 discloses a pigment with a pseudobrookite structure that contains various metals other than Fe and Ti. However, the method for producing this pigment involves mixing submicron raw material powders and firing them at high temperatures of 1000°C or higher, and it is therefore expected that the resulting pigment is a submicron pigment, not a fine particle pigment with excellent transparency. Patent Document 3 discloses a pigment made of Fe, Ti, and Al, or a pigment incorporating other metals. This pigment manufacturing method involves mechanochemically treating raw material powder to produce a pigment with excellent color development and tinting power, but the pigment obtained here is a submicron pigment, and no pigment with fine particles smaller than submicron has been obtained. In Non-Patent Document 1, fine particles are synthesized using a gas phase method. Here, TiCl4-FeCl3 is used, and fine powder with an average particle size of 0.03 μm to 0.1 μm is obtained in a TiO2-Fe2O3 system by a gas phase reaction at 800°C to 1250°C. However, these fine particles are composed of TiO2, Fe2TiO5, and αFe2O3, and the pigment has a strong reddish color due to the inclusion of Fe2O3, so it cannot be used as a yellow pigment. As described above, the prior art has not provided a yellow pigment having excellent heat resistance, transparency, and durability as a fine particle pigment. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 8-73224 [Patent Document 2] Japanese Patent Application Publication No. 9-221323 [Patent Document 3] International Publication No. 2001 / 070632 [Non-patent literature]

[0005] [Non-Patent Document 1] Yoko Suyama and Akio Kato, Color Materials, 53, 1035-1043 (1980) Summary of the Invention [Problem to be solved by the invention]

[0006] In response to growing environmental concerns, the development of pigments free of hazardous metals is desired, and Fe2TiO5-based pseudobrookite-type inorganic yellow pigments have been proposed. These pigments have been applied to paints and plastics due to their excellent heat resistance and durability. However, when attempting to expand their application range by taking advantage of their lack of hazardous metals, heat resistance, and durability, which are not found in conventional pigments, for example, when applying them to inkjet printers, their high specific gravity and large particle size make it difficult to maintain ink stability. When applying them to paints for metallic or clear coatings, they have issues such as high hiding power and poor transparency, which prevent the metallic appearance from being achieved. Furthermore, when coloring glass or film, where a transparent color is desired, even submicron particles, which are considered to have small particle sizes, have high hiding power and a lack of transparency. As a yellow pigment, FeTi-based pseudobrookite pigments have excellent heat resistance and durability, but when trying to expand their range of applications, they face the above-mentioned problems. Conventional technology has not been able to obtain pigments with particle sizes smaller than submicron, and even when attempts have been made, they have only resulted in products with a strong reddish hue. There is a strong demand for yellow pigments with particle sizes that have good color development and that solve the above-mentioned problems.

[0007] An object of the present invention is to provide a fine particle composite oxide yellow pigment that is excellent in heat resistance, transparency, and durability, and a method for producing the same. [Means for solving the problem]

[0008] According to the present invention, there are provided the following fine particle composite oxide yellow pigment and a method for producing the same. [1] A method for producing a pseudobrookite-type fine particle composite oxide yellow pigment composed of Fe, Al, and Ti, comprising: a step of forming an Al precipitate in water using an Al metal salt and an alkali to obtain a first reaction solution; a step of producing a pigment precursor in water using the first reaction liquid, metal salts of Fe and Ti, and an alkali to obtain a second reaction liquid; and a step of filtering, washing with water, drying, and then calcining the pigment precursor at a temperature of 600°C or higher and 900°C or lower to obtain a fine particle composite oxide yellow pigment, The fine particle composite oxide yellow pigment has an average primary particle diameter of 80 nm or less. Method for producing fine particle composite oxide yellow pigment. [2] The method for producing a fine particle composite oxide yellow pigment according to claim 1, wherein the fine particle composite oxide yellow pigment is prepared by converting and dividing each constituent metal into its respective oxide constituent units, Fe2O3, Al2O3, and TiO2, and the proportion of Fe2O3 is 30% by mass or more and 40% by mass or less, the proportion of Al2O3 is 20% by mass or more and 30% by mass or less, and the proportion of TiO2 is 35% by mass or more and 45% by mass or less. [3] A pseudobrookite-type fine particle composite oxide yellow pigment composed of Fe, Al, and Ti, When each constituent metal is converted into its respective oxide constituent unit and divided into Fe2O3, Al2O3, and TiO2, the proportion of Fe2O3 is 30% by mass or more and 40% by mass or less, the proportion of Al2O3 is 20% by mass or more and 30% by mass or less, and the proportion of TiO2 is 35% by mass or more and 45% by mass or less, The fine particle composite oxide yellow pigment has an average primary particle diameter of 80 nm or less. Fine particle composite oxide yellow pigment. [Effects of the Invention]

[0009] According to one aspect of the present invention, it is possible to provide a fine particle composite oxide yellow pigment having excellent heat resistance, transparency, and durability, and a method for producing the same. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a photograph showing TEM images of the yellow pigments of Example 2 and Comparative Example 5. DETAILED DESCRIPTION OF THE INVENTION

[0011] <Method of manufacturing fine particle composite oxide yellow pigment> Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments. The method for producing a fine particle composite oxide yellow pigment according to this embodiment (hereinafter also referred to as the production method according to this embodiment) is a method for producing a pseudobrookite-type fine particle composite oxide yellow pigment composed of Fe, Al, and Ti. The production method according to this embodiment includes the steps of: forming an Al precipitate in water using an Al metal salt and an alkali to obtain a first reaction liquid (hereinafter also referred to as the first step); forming a pigment precursor in water using the first reaction liquid, Fe and Ti metal salts and an alkali to obtain a second reaction liquid (hereinafter also referred to as the second step); and filtering, washing with water, drying, and then calcining the pigment precursor at a temperature of 600° C. to 900° C. to obtain a fine particle composite oxide yellow pigment (hereinafter also referred to as the third step). The obtained fine particle composite oxide yellow pigment must have an average primary particle diameter of 80 nm or less.

[0012] The reason why the production method according to this embodiment can produce a fine particle composite oxide yellow pigment having excellent heat resistance, transparency, and durability is not entirely clear, but the present inventors speculate as follows. That is, since pseudobrookite Fe2TiO5 has a slightly reddish hue, in this embodiment, it is presumed that a solid solution of Al in this has a yellowish hue and is a good yellow pigment. Furthermore, in this embodiment, since the solid solution of Al does not cause any problems with physical properties such as heat resistance, a fine particle pigment is produced using a three-component system of Fe, Al, and Ti. Pigment synthesis generally involves mixing raw material powders and firing them to produce a pigment, which is called a dry method. However, even if fine particle materials are used as raw materials, particle growth occurs during firing, making this method unsuitable for producing fine particles with excellent transparency. For this reason, in this embodiment, the pigment is produced using a wet method, in which alkali is applied to metal salts in water to produce a precipitate, which is then filtered, washed with water, dried, and then fired.

[0013] In this embodiment, a wet synthesis method is used, in which alkali is applied to metal salts to form precipitates. However, it has been found that simply applying alkali to a mixed solution of three metal salts to form a precipitate only results in a pigment with a strong reddish hue under these conditions, and the desired yellow fine particle pigment with good color development cannot be obtained. Furthermore, similar results were obtained when an Fe precipitate was prepared after an Al and Ti precipitate, and when an Al and Fe precipitate was prepared after an Al and Fe precipitate. After extensive research, the inventors have found that a precipitate in which Fe and Ti are mixed in a nanometer-scale and highly reactive state is required, and that the crystallization of Fe and Ti, along with the solid solution of Al, is the condition for obtaining a fine particle pigment with good yellow color development. Therefore, it is necessary to prepare the Al precipitate and the Fe and Ti precipitates separately. It should be noted that, with this type of pigment, pigments with a strong reddish hue tend to be obtained, but fine particle pigments with good yellow color development can only be obtained under specific synthesis conditions, and the inventors speculate that this may be the reason why fine particle yellow pigments have not been proposed until now. From the above, the present inventors presume that the fine particle composite oxide yellow pigment obtained by the production method according to this embodiment has excellent heat resistance, transparency, and durability.

[0014] (first step) In the first step, a metal salt of Al and an alkali are used to form a precipitate of Al in water to obtain a first reaction solution. As the metal salt of Al used in this embodiment, sulfate, chloride, and nitrate can be used. Among these, at least one of chloride and sulfate is preferred due to ease of availability. The alkali used in this embodiment may be caustic soda or soda ash. Among these, soda ash is preferred from the viewpoint of dispersibility.

[0015] As an example of the first step, a solution of aluminum chloride and a solution of soda ash are added to water while adjusting the pH to 4, forming a precipitate of Al and obtaining a first reaction liquid. The temperature at this time is preferably 25°C or higher and 50°C or lower, and more preferably 35°C or higher and 45°C or lower.

[0016] (Second process) In the second step, a pigment precursor is produced in water using the first reaction liquid obtained in the first step, metal salts of Fe and Ti, and an alkali to obtain a second reaction liquid. The metal salts of Fe and Ti used in this embodiment are the same as the metal salt of Al described above. The alkali used in this embodiment is also the same as the alkali described above.

[0017] As an example of the second step, first, an alkali is added to the first reaction solution obtained in the first step, and the temperature is raised to adjust the pH. The temperature at this time is preferably 45° C. to 75° C., and more preferably 55° C. to 65° C. The pH after adjustment is preferably 5 to 7, and more preferably 5.5 to 6.5. Next, a solution of titanium tetrachloride and iron sulfate mixed with a soda ash solution is added to this reaction liquid while maintaining the pH at 6, producing a precipitate of Fe and Ti, producing a pigment precursor, and obtaining a second reaction liquid.

[0018] One of the features of the present invention is the two-stage precipitation process, the first and second steps described above. Even if two-stage precipitation is performed, if a titanium solution is mixed with an aluminum solution to form a mixed solution, and the first precipitation is formed, followed by an iron precipitation in the second stage, the resulting pigment will have a reddish hue and will not have a fine particle size with good yellow color development. However, if the reaction is accelerated by increasing the calcination temperature, the hue will become yellow, but the particle size will increase. Pigments of submicron or larger sizes can be produced without the two-stage precipitation process, but it is difficult to produce a transparent pigment. Patent Document 1 also describes a method of producing a pigment by precipitating some components with alkali and then calcining the precipitate. However, this method uses a Ti hydrolyzate and then precipitates other components, and the Ti hydrolyzate has a certain size. Therefore, even if the pigment is calcined and a good color development is achieved, the particles will be submicron at best. In order to obtain a fine particle pigment with good yellow color development, it is not sufficient to simply use a precipitation reaction, and this is the significance of the present invention.

[0019] (Third step) In the third step, the pigment precursor obtained in the second step is filtered, washed with water, dried, and then calcined at a temperature of 600° C. to 900° C. to obtain a fine particle composite oxide yellow pigment. The firing may be performed in air, which is an oxidizing atmosphere, and no special atmospheric adjustment is required. The firing temperature may be any temperature at which pseudobrookite crystals are obtained, and in this embodiment, the firing temperature is 600°C or higher and 900°C or lower. In this embodiment, because the mixed state of each metal component is uniform in the nano-range, pseudobrookite crystals can be obtained at a firing temperature lower than the 800°C to 1200°C temperatures typically used in submicron applications. In this embodiment, from the standpoint of hue, transparency, and the like, the firing temperature is preferably 700°C or higher and 850°C or lower. This firing temperature is more than 100°C lower than the firing temperatures of conventional pigments of this type, which also suggests that the uniformity of each metal in the precipitate is high.

[0020] The average primary particle diameter of the fine particle composite oxide yellow pigment obtained by the production method according to this embodiment must be 80 nm or less, preferably 60 nm or less, and more preferably 50 nm or less. If the primary particle diameter exceeds 80 nm, satisfactory transparency cannot be obtained. There is no particular lower limit, but if it is less than 10 nm, the pigment will tend to aggregate, requiring a large amount of dispersion energy when dispersed in a resin composition or solvent, which is not practical.

[0021] In the fine particle composite oxide yellow pigment obtained by the production method according to this embodiment, when each constituent metal is converted and divided into its respective oxide constituent units, and these are expressed as Fe2O3, Al2O3, and TiO2, it is preferable that the proportion of Fe2O3 is 30% to 40% by mass, the proportion of Al2O3 is 20% to 30% by mass, and the proportion of TiO2 is 35% to 45% by mass. When the proportions of Fe2O3, Al2O3, and TiO2 are each within the above ranges, a yellow color with good color development tends to be easily obtained.

[0022] <Fine particle composite oxide yellow pigment> The fine particle composite oxide yellow pigment according to this embodiment is a pseudobrookite-type fine particle composite oxide yellow pigment composed of Fe, Al, and Ti. This fine particle composite oxide yellow pigment is prepared by converting each constituent metal into its respective oxide constituent unit, dividing them into Fe2O3, Al2O3, and TiO2, and the proportion of Fe2O3 is 30% to 40% by mass, the proportion of Al2O3 is 20% to 30% by mass, and the proportion of TiO2 is 35% to 45% by mass. The fine particle composite oxide yellow pigment must also have an average primary particle diameter of 80 nm or less.

[0023] The reasons why the fine particle composite oxide yellow pigment according to this embodiment is a yellow pigment with a desirable hue and is excellent in heat resistance, transparency, and durability are not entirely clear, but the present inventors speculate as follows. That is, the oxide composition in this embodiment is basically (Fe,Al)2TiO5, in which Al is solid-solved in the pseudobrookite type of Fe2TiO5. If the Fe content is high and the Al content is low, the hue becomes reddish and the transparency decreases. If the Fe content is low and the Al content is high, the hue becomes yellowish and the transparency increases, but the color strength (color intensity) decreases. Furthermore, compositions with a high titanium oxide content tend to decrease transparency. In particular, if hematite (Fe2O3) is formed, the hue becomes reddish and a good yellow color cannot be obtained. In this embodiment, it has been found that excellent hue and transparency are achieved when the proportions of Fe2O3, Al2O3, and TiO2 are each within the above-mentioned ranges. The reasons for the excellent heat resistance and durability are as described above. From the above, the present inventors presume that the fine particle composite oxide yellow pigment according to this embodiment is a yellow pigment with a desirable hue, and is excellent in heat resistance, transparency, and durability.

[0024] The fine particle composite oxide yellow pigment according to this embodiment is influenced not only by the metal composition but also by the pigment synthesis conditions, and therefore, appropriate adjustment of the composition, synthesis conditions, and firing temperature is an important factor in obtaining the desired pigment. This type of pigment tends to produce a reddish pigment if the conditions are not met. If a wet method is used as a pigment synthesis method, it is possible to produce a pigment with small particles, but unless a two-stage synthesis is performed as in the manufacturing method according to the present embodiment described above, the resulting pigment will inevitably be reddish, and if the firing temperature is increased in an attempt to make it yellowish, the hue will be adjusted, but the pigment will be inferior in terms of transparency.

[0025] The composite oxide yellow pigment particles according to this embodiment are yellow fine particles with heat resistance suitable for use in engineering plastics (heat resistance of 300°C or higher) or ceramic coloring. Furthermore, this yellow pigment is suitable for use in applications requiring transparency, such as metallic or color clear paints, and is a durable pigment with long-term weather resistance. Currently, such yellow pigments are almost nonexistent, both organic and inorganic. Another advantage is that this yellow pigment is composed of Fe, Ti, and Al and does not contain harmful metals. [Example]

[0026] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples. In the examples and comparative examples, "parts" and "%" are by mass unless otherwise specified.

[0027] The metal salts used were as follows: (iron salts) A1: Ferrous sulfate heptahydrate crystals A2: Ferric chloride hexahydrate crystals (aluminum salts) B1: Aluminum chloride hexahydrate crystals B2: Aluminum sulfate hexahydrate crystals (titanium salts) C1: Titanium tetrachloride aqueous solution (containing 16.2% Ti) C2: Titanyl sulfate crystal (33% TiO2 content)

[0028] Example 1 Dissolve 94.7g of aluminum chloride in 200mL of water to prepare a metal salt aqueous solution for the first stage of synthesis. Dissolve 230g of soda ash in 1000mL of water to prepare an alkaline aqueous solution. In a separate container from the aluminum chloride, dissolve 139.3g of iron sulfate and 148.0g of titanium tetrachloride solution in 400mL of water in advance. Add 1500mL of water to a beaker and heat to 40°C while stirring. Add the aluminum chloride aqueous solution and soda ash solution dropwise to form a precipitate at pH 4 (first stage synthesis). After the aluminum solution has been added dropwise, raise the temperature to 60°C. At the same time, add soda ash dropwise to raise the pH to 6. Once the temperature reaches 60°C, a pre-dissolved mixed solution of iron sulfate and titanium tetrachloride and soda ash are added dropwise, and a precipitate is formed at pH 6 (second-stage synthesis). After the metal salt solution has been added dropwise, the pH is raised to 6.5, the temperature is raised to 70°C, and the mixture is then aged for one hour. After aging, the slurry is decanted to wash away any remaining salt, then filtered and dried in a dryer. The dried pigment precursor is placed in a crucible and fired in an electric furnace at 800°C for one hour. After firing, it is pulverized in a grinder to obtain a yellow pigment. <Examples 2 to 7> A yellow pigment was produced in the same manner as in Example 1, except that the raw materials shown in Table 1 were blended so as to achieve the metal composition ratios shown in Table 1.

[0029] <Comparative Example 1> A yellow pigment was produced in the same manner as in Example 2, except that a metal salt of Ti was dissolved in a metal salt of Al to perform the first synthesis step, and then Fe was precipitated in the second synthesis step. <Comparative Example 2> A yellow pigment was produced in the same manner as in Example 2, except that the first stage of synthesis was carried out by dissolving a metal salt of Fe in a metal salt of Al, and then the second stage was synthesised by precipitating Ti. <Comparative Example 3> A yellow pigment was prepared in the same manner as in Example 2, except that metal salts of Al, Fe, and Ti were dissolved in the same solution and synthesis was carried out in the first step only. <Comparative Example 4> A yellow pigment was produced in the same manner as in Example 2, except that the synthesized pigment precursor was calcined at 950°C. <Comparative Example 5> A commercially available pseudobrookite-type yellow pigment containing the same Fe, Al, and Ti metals was used.

[0030] The resulting pigments were evaluated by the following methods. <Average primary particle size and TEM image> Typically, a solution of a pigment dispersed in a solvent such as water is measured using a dynamic scattering particle size distribution analyzer. However, the pigment of the present invention is a fine particle, and dispersing it down to primary particles is difficult. Therefore, we decided to calculate the particle size from transmission electron microscope images (TEM images). Specifically, the prepared pigment powder was photographed with a transmission electron microscope, and the average primary particle size was calculated from 50 randomly selected particles using image analysis software (Mac-View, manufactured by Mountec Co., Ltd.). The results are shown in Table 1. TEM images of the yellow pigments of Example 2 and Comparative Example 5 are shown in FIG. <Color and transparency> The pigments for evaluation were made into paints, and their hue and transparency were evaluated. A melamine alkyd baked paint was prepared, with a pigment content of 20 PHR (ratio of additives to 100 parts by mass of resin). 1 mm diameter zirconia beads were used as the dispersion medium, and the dispersion was carried out using a paint shaker for 2 hours. The color was then spread on art paper with a black stripe and baked at 120°C to prepare evaluation samples, which were then visually evaluated for hue and transparency. Evaluation was based on the following criteria. The results are shown in Table 1. The hue appears different depending on the pigment content and film thickness. Regarding transparency, the black background is clearly visible in the black bands of the art paper, and there is no whitish tinge, which indicates a more transparent appearance. However, since it is difficult to judge numerically, the judgment was made by visual inspection. (hue) ◎: Excellent yellow coloring. ◯: Yellowish, but with a slightly reddish hue. △: Reddish yellow hue. ×: Completely reddish hue. (transparency) ◎: Excellent transparency. Good: Transparency is present but slightly inferior. △: Slightly poor transparency. ×: Hiding properties are observed and transparency is poor. <Hue measurement> Similar evaluation samples for hue and transparency were prepared and subjected to color measurement using a spectrophotometer (CM-3600A, manufactured by Konica Minolta, Inc.). Color measurement was performed on the pigments obtained in Example 2, Comparative Example 1, Comparative Example 2, and Comparative Example 4. The results are shown in Table 2.

[0031] [Table 1]

[0032] [Table 2]

[0033] The results shown in Table 1 indicate that the yellow pigments according to the present invention (Examples 1 to 7) were excellent in the evaluation of hue and transparency. Furthermore, the results shown in Table 2 indicate that the yellow pigment according to the present invention (Example 2) had a low lightness L* in the black band area, giving it a sense of transparency, and a low chroma a* in the white band area, giving it a yellow color with a weak reddish tinge. Furthermore, the yellow pigments according to the present invention (Examples 1 to 7) are fine particle composite oxides, and therefore have excellent heat resistance and durability. From these results, it was confirmed that the yellow pigments according to the present invention (Examples 1 to 7) are excellent in heat resistance, transparency, and durability.

Claims

1. A method for producing a pseudobrookite-type yellow composite oxide pigment comprising Fe, Al, and Ti, the method comprising the steps of: a step of generating a precipitate of Al in water using a metal salt of Al and an alkali to obtain a first reaction solution; a step of producing a pigment precursor in water using the first reaction liquid, metal salts of Fe and Ti, and an alkali to obtain a second reaction liquid; and a step of filtering, washing with water, drying, and then calcining the pigment precursor at a temperature of 600°C or higher and 900°C or lower to obtain a fine particle composite oxide yellow pigment, the average primary particle diameter of the fine particle composite oxide yellow pigment is 80 nm or less; Method for producing fine particle composite oxide yellow pigment.

2. The fine particle composite oxide yellow pigment converts and separates each constituent metal into its respective oxide constituent unit, and then separates these into Fe ２ O ３ , Al ２ O ３ , and TiO ２ When this is done, Fe ２ O ３ The proportion of Al is 30 mass % or more and 40 mass % or less, ２ O ３ The proportion of TiO is 20 mass % or more and 30 mass % or less, ２ 2. The method for producing a fine particle composite oxide yellow pigment according to claim 1, wherein the ratio of

3. A pseudobrookite-type fine particle composite oxide yellow pigment composed of Fe, Al, and Ti, Each constituent metal is converted into its respective oxide constituent unit, divided, and these are separated into Fe ２ O ３ , Al ２ O ３ , and TiO ２ When this is done, Fe ２ O ３ The proportion of Al is 30 mass % or more and 40 mass % or less, ２ O ３ The proportion of TiO is 20 mass % or more and 30 mass % or less, ２ The proportion of is 35% by mass or more and 45% by mass or less, the average primary particle diameter of the fine particle composite oxide yellow pigment is 80 nm or less; Fine particle composite oxide yellow pigment.

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