Fine particle composite oxide yellow pigment and method for producing same

Abstract

Provided is a method for producing a pseudobrookite-type fine particle composite oxide yellow pigment composed of Fe, Al, and Ti, the method comprising: a step for producing a precipitate of Al in water by using a metal salt of Al and an alkali to obtain a first reaction liquid; a step for 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 a step for filtering the pigment precursor, washing with water, drying, and then firing the resultant at a temperature of 600 °C to 900 °C to obtain a fine particle composite oxide yellow pigment, wherein the average primary particle diameter of the fine particle composite oxide yellow pigment is 80 nm or less.

Description

Fine particle composite oxide yellow pigment and its manufacturing method

[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.

[0002] Pigments are used in a wide variety of applications, including as colorants for 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 resistance and weather resistance, but in recent years, there has been a strong movement to avoid pigments containing Cd, Cr, or Pb due to environmental concerns, and their use is 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 composite oxide-based pigment, contains metals such as Cr, Sb, or Ni, and pigments that do not contain these elements are desired. On the other hand, organic yellow pigments exhibit vivid hues, but many of them have low heat resistance and poor weather resistance, limiting their use depending on the application. Goethite (α-FeOOH) is a yellow pigment that does not contain harmful metals and is actually used. However, this pigment has low heat resistance, and when the temperature exceeds 200°C, it is dehydrated by heating and becomes hematite (α-FeOOH). ２ O ３ ) and discolor to a dark brown. For this reason, it may not be usable depending on the application. There are also fine particle types of this pigment, but because they have the same chemical structure, they also have low heat resistance. In this situation, Fe is one of the heat-resistant pigments that does not contain harmful metals. ２ TiO ５ Pseudobrookite pigments have been proposed, but 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 consisting of a mixture of pseudobrookite with Al dissolved therein and rutile titanium oxide. This pigment is obtained by adding iron salt and aluminum salt to hydrous titanium oxide, neutralizing with alkali, and then calcining the mixture, but the particle size of this pigment is in the submicron range. Patent Document 2 discloses a pigment having a pseudobrookite structure containing various metals other than Fe and Ti. However, since this pigment manufacturing method involves mixing submicron raw material powders and calcining them at high temperatures of 1000°C or higher, the resulting pigment is a submicron pigment, not a fine-particle pigment with excellent transparency. Patent Document 3 discloses a pigment consisting of Fe, Ti, and Al, or a pigment incorporating other metals. This method of producing pigments involves mechanochemically treating raw material powders to produce pigments with excellent color development and tinting power, but the pigments obtained are submicron pigments, and pigments with particles smaller than submicron have not been obtained. In Non-Patent Document 1, particles are synthesized using a gas phase method. Here, TiCl ４ -FeCl ３ was used, and TiO was produced by a gas phase reaction at 800 to 1250°C. ２ -Fe ２ O ３ However, the fine particles obtained in this system have an average particle size of 0.03 μm to 0.1 μm. ２ and Fe ２ TiO ５ and αFe ２ O ３ The color is Fe ２ O ３ However, due to the presence of fluorine, the pigment has a strong reddish tint and is therefore not suitable for use as a yellow pigment. Thus, the prior art has not provided a fine particle yellow pigment that is excellent in heat resistance, transparency, and durability.

[0004] JP-A-8-73224 JP-A-9-221323 International Publication No. 2001 / 070632

[0005] Yoko Suyama and Akio Kato, Color Materials, 53, 1035-1043 (1980)

[0006] Due to growing environmental concerns, there is a demand for the development of pigments that do not contain harmful metals. ２ TiO ５ Pseudobrookite-type pigments based on FeTi have been proposed. Because of their excellent heat resistance and durability, they have been applied to coloring paints or plastics. However, when attempting to broaden the range of applications by taking advantage of the advantages of not containing harmful metals, heat resistance, and durability 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 paints, they have problems such as high hiding power and poor transparency, failing to achieve a metallic appearance. Furthermore, when coloring glass or film, where a transparent color is desired, even submicron particles, which are considered to have a small particle size, have high hiding power and fail to achieve a transparent appearance. FeTi pseudobrookite-type pigments have excellent heat resistance and durability as yellow pigments, but the above-mentioned problems arise when attempting to broaden their range of applications. Conventional techniques have not been able to produce pigments with particle sizes smaller than submicron, and even when attempts have been made, they have only resulted in pigments with a strong reddish hue. Therefore, there is a strong demand for yellow pigments with particle sizes that have good color development and that can 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.

[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 the steps of: forming an Al precipitate in water using a metal salt of Al and an alkali to obtain a first reaction liquid; forming 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; 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 the fine particle composite oxide yellow pigment; wherein the fine particle composite oxide yellow pigment has an average primary particle size of 80 nm or less; and the fine particle composite oxide yellow pigment is obtained by converting and dividing each constituent metal into its respective oxide constituent unit, and calcining 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] A method for producing a fine particle composite oxide yellow pigment, wherein the proportion of Fe, Al, and Ti is 35% by mass or more and 45% by mass or less. 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 % or more by mass and 45% or less by mass, and the average primary particle diameter of the fine particle composite oxide yellow pigment is 80 nm or less.

[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.

[0010] 1 is a photograph showing TEM images of the yellow pigments of Example 2 and Comparative Example 5.

[0011] <Method for Producing a Fine-Particle Composite Oxide Yellow Pigment> Hereinafter, an embodiment of the present invention will be described, but the present invention is not limited to the following embodiment. 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: generating 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); generating 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, and drying the pigment precursor, followed by calcining 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 average primary particle diameter of the resulting fine-particle composite oxide yellow pigment must be 80 nm or less.

[0012] Although the reason why the production method according to the present embodiment can produce a fine particle composite oxide yellow pigment having excellent heat resistance, transparency, and durability is not entirely clear, the present inventors speculate as follows. ２ TiO ５Since pseudobrookite (1) is slightly reddish, it is presumed that in this embodiment, a solid solution of Al in this pseudobrookite will have a yellowish hue and be 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 from a three-component system of Fe, Al, and Ti. Pigment synthesis generally involves a method called a dry method, in which raw material powders are mixed and fired to produce a pigment. 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 an alkali is applied to a metal salt in water to produce a precipitate, which is then filtered, washed with water, dried, and fired.

[0013] In this embodiment, a wet synthesis method is used, in which alkali is applied to a metal salt to form a precipitate. However, it has been found that simply applying alkali to a mixed solution of three metal salt components 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, the same tendency was observed when an Fe precipitate was prepared after an Al and Ti precipitate, and when a Ti precipitate was prepared after an Al and Fe precipitate. As a result of extensive research by the inventors, it was 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 and the subsequent solid solution of Al are necessary to produce 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. Furthermore, 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 believe that this is the reason why fine particle yellow pigments have not been proposed until now. From the above, the inventors believe 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 first reaction solution is obtained by forming an Al precipitate in water using an Al metal salt and an alkali. As the Al metal salt 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. As the alkali used in this embodiment, caustic soda and soda ash can be used. 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, thereby forming a precipitate of Al and obtaining a first reaction solution. 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 Step) In the second step, a pigment precursor is produced in water using the first reaction solution obtained in the first step, metal salts of Fe and Ti, and an alkali to obtain a second reaction solution. 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, while adding an alkali to the first reaction liquid obtained in the first step, the temperature is raised and the pH is adjusted. The temperature at this time is preferably 45°C or higher and 75°C or lower, and more preferably 55°C or higher and 65°C or lower. The pH after adjustment is preferably 5 or higher and 7 or lower, and more preferably 5.5 or higher and 6.5 or lower. Next, to this reaction liquid, a solution of titanium tetrachloride and iron sulfate mixed together with a soda ash solution is added while maintaining the pH at 6, forming precipitates 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 advanced by increasing the calcination temperature, the hue will become yellow, but the particle size will increase. To produce pigments of submicron or larger sizes, it is possible to produce pigments without the two-stage precipitation process, but it is difficult to produce a pigment with transparency. 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 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 in size 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, and dried, and then calcined at a temperature of 600°C to 900°C to obtain a fine particle composite oxide yellow pigment. Calcination can be performed in air, which is an oxidizing atmosphere, and no special atmospheric adjustment is required. The calcination temperature is sufficient as long as it is a temperature at which pseudobrookite crystals are obtained; in this embodiment, the calcination temperature is 600°C to 900°C. In this embodiment, since the mixed state of each metal component is uniform in the nano-range, pseudobrookite crystals are obtained at a calcination temperature lower than the 800°C to 1200°C temperatures typically used in submicron scales. In this embodiment, from the viewpoints of hue, transparency, etc., the calcination temperature is preferably 700°C to 850°C. This calcination temperature is more than 100°C lower than the calcination temperature of conventional pigments of this type, which also suggests high uniformity of each metal in the precipitate.

[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 great deal of dispersion energy when dispersed in a resin composition or solvent, which is not practical.

[0021] The fine particle composite oxide yellow pigment obtained by the production method according to this embodiment is obtained by converting each constituent metal into the constituent unit of each oxide, dividing it, and then dividing it 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 Fe is preferably 35 mass % or more and 45 mass % or less. ２ O ３ , Al ２ O ３ , and TiO ２ When the proportions are within the above ranges, a yellow color with good color development tends to be 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 structural unit, dividing it, and then dividing these into Fe, Al, and Ti. 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 required to be 80 nm or less.

[0023] The reason 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 is not entirely clear, but the present inventors speculate as follows. That is, the oxide composition according to this embodiment contains Fe ２ TiO ５ Al is dissolved in the pseudobrookite type (Fe, Al) ２ TiO ５ The basic principle is that if there is a lot of Fe and little Al, the hue will be reddish and the transparency will decrease. If there is little Fe and a lot of Al, the hue will be yellowish and the transparency will increase, but the coloring power (color intensity) will decrease. Also, if there is a lot of titanium oxide, the transparency will tend to decrease. In particular, in terms of hue, hematite (Fe ２ O ３ If Fe is formed, the color will have a reddish hue and a good yellow color cannot be obtained. ２ O ３ , Al ２ O ３ , and TiO ２ It has been found that when the proportions of are within the above ranges, the pigment has excellent hue and transparency. The reasons for the excellent heat resistance and durability are as described above. From the above, the inventors surmise that the fine particle composite oxide yellow pigment according to this embodiment is a yellow pigment with a preferable hue and excellent 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 appropriate adjustment of the composition, synthesis conditions, and calcination temperature is an important factor in obtaining the desired pigment. Pigments of this type tend to produce reddish pigments if the conditions are not right. While a wet method can be used to synthesize pigments with small particles, unless the two-stage synthesis method according to this embodiment is used, the resulting pigment will inevitably be reddish. Raising the calcination temperature to shift the pigment to a yellow hue will adjust the hue, but the resulting pigment will have poor transparency.

[0025] The composite oxide yellow pigment particles according to this embodiment are yellow fine particles with heat resistance suitable for use in coloring engineering plastics (heat resistance of 300°C or higher) or ceramics. Furthermore, this yellow pigment is suitable for applications requiring transparency, such as metallic or clear color 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.

[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 crystals (TiO ２ (33% content)

[0028] Example 1: 94.7 g of aluminum chloride was dissolved in 200 mL of water to prepare a metal salt aqueous solution for the first stage of synthesis. 230 g of soda ash was dissolved in 1000 mL of water to prepare an alkaline aqueous solution. 139.3 g of iron sulfate and 148.0 g of titanium tetrachloride solution were pre-dissolved in 400 mL of water in a container separate from the aluminum chloride solution. 1500 mL of water was added to a beaker and the temperature was raised to 40°C while stirring. An aluminum chloride aqueous solution and a soda ash solution were added dropwise to form a precipitate at pH 4 (first stage synthesis). After the aluminum solution was added dropwise, the temperature was raised to 60°C. At the same time, soda ash was added dropwise to raise the pH to 6. Once the temperature reached 60°C, a pre-dissolved mixed solution of iron sulfate and titanium tetrachloride and soda ash were added dropwise to form a precipitate at pH 6 (second stage synthesis). After the dropwise addition of the metal salt solution is complete, the pH is increased to 6.5, the temperature is raised to 70°C, and then the slurry is aged for 1 hour. After aging, the remaining salt is washed away from the slurry by decantation, and then the slurry is 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 1 hour. After firing, the pigment precursor is pulverized in a pulverizer to obtain a yellow pigment. <Examples 2 to 7> Yellow pigments were produced in the same manner as in Example 1, except that the types of raw materials shown in Table 1 were blended so as to obtain the metal composition ratios shown in Table 1.

[0029] Comparative Example 1: A yellow pigment was prepared in the same manner as in Example 2, except that a Ti metal salt was dissolved in an Al metal salt to perform the first synthesis step, and then Fe was precipitated in the second synthesis step. Comparative Example 2: A yellow pigment was prepared in the same manner as in Example 6, except that an Fe metal salt was dissolved in an Al metal salt to perform the first synthesis step, and then Ti was precipitated in the second synthesis step. Comparative Example 3: A yellow pigment was prepared in the same manner as in Example 7, except that Al, Fe, and Ti metal salts were dissolved in the same solution, and synthesis was performed only in the first synthesis step. Comparative Example 4: A yellow pigment was prepared 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 obtained pigments were evaluated using the following methods. <Average Primary Particle Diameter and TEM Images> Generally, a solution obtained by dispersing a pigment 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, here, the average primary particle diameter was calculated from transmission electron microscope images (TEM images). Specifically, the prepared pigment powder was photographed using a transmission electron microscope, and the average primary particle diameter was calculated from 50 randomly selected particles using image analysis software (Mac-View, manufactured by Mountech 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 Figure 1. <Hue and Transparency> The pigments for evaluation were made into paints, and their hue and transparency were evaluated. A melamine alkyd baking paint was prepared, with a pigment content of 20 PHR (ratio of additives to 100 parts by mass of resin). The dispersion medium used in this test was 1 mm diameter zirconia beads. The dispersion was performed using a paint shaker for 2 hours, and the resulting color was applied to art paper with a black band and baked at 120°C to prepare an evaluation sample. The hue and transparency were visually evaluated. The 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, a more transparent appearance is indicated when the black background is clearly visible in the black band of the art paper and there is no whitish tint. However, since it is difficult to evaluate the transparency numerically, the evaluation was performed visually. (Hue) AA: Excellent yellowish coloring. A: Yellowish, but with a slightly reddish hue. B: Reddish-yellow hue. C: Completely reddish hue. (Transparency) AA: Excellent transparency. A: Transparent, but slightly inferior. B: Slightly inferior transparency. C: Hiding ability is observed and transparency is poor. <Hue Measurement> Samples for evaluation similar to those for hue and transparency were prepared and subjected to color measurement using a spectrophotometer (CM-3600A, manufactured by Konica Minolta, Inc.). The color measurements were performed on the pigments obtained in Example 2, Comparative Example 1, Comparative Example 2, and Comparative Example 4. The results obtained are shown in Table 2.

[0031]

[0032]

[0033] The results shown in Table 1 demonstrate that the yellow pigments according to the present invention (Examples 1 to 7) exhibited favorable evaluation results for hue and transparency. Furthermore, the results shown in Table 2 demonstrate that the yellow pigment according to the present invention (Example 2) exhibits low lightness L* in the black band portions, providing a sense of transparency, and low chroma a* in the white band portions, resulting in a yellow color with a slight 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. These findings confirm that the yellow pigments according to the present invention (Examples 1 to 7) exhibit excellent heat resistance, transparency, and durability.

Claims

1. A method for producing a pseudobrookite-type fine particle composite oxide yellow pigment composed of Fe, Al, and Ti, comprising the steps of: generating an Al precipitate in water using a metal salt of Al and an alkali to obtain a first reaction liquid; generating 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; filtering, washing with water, drying, and then firing 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; wherein the fine particle composite oxide yellow pigment has an average primary particle size of 80 nm or less; and the fine particle composite oxide yellow pigment is obtained by converting and dividing each constituent metal into its respective oxide constituent unit, and dividing these into Fe, Al, and Ti. 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 wherein the proportion of the compound (I) is 35% by mass or more and 45% by mass or less.

2. A pseudobrookite-type fine particle composite oxide yellow pigment composed of Fe, Al, and Ti, in which each constituent metal is converted into its respective oxide structural unit, divided, and then 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 % or more by mass and 45% or less by mass, and the average primary particle diameter of the fine particle composite oxide yellow pigment is 80 nm or less.

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