Core-shell type transition metal-doped colored silica sol, and method for producing the same

Abstract

To provide a core-shell type transition metal-doped colored silica sol obtained by coating a core particle comprising a silica particle doped with a transition metal with silica as a shell layer which is excellent in transparency, light resistance, and colorability.SOLUTION: A silica sol pertaining to the present invention includes a core-shell type silica particle satisfying the following conditions (1) to (4), where the core-shell type silica particle is a colored silica sol obtained by doping with a transition metal. (1) A mass ratio (T / silica) of a transition metal T to silica is 0.001 or higher and 0.05 or lower, (2) a number average particle diameter D1 by calculating by an image analysis method from an electron microscopy image is 5 nm or more and 50 nm or less, (3) a BET particle diameter D2 calculated by a nitrogen adsorption method is 5 nm or more and less than 50 nm, and (4) a number average particle diameter / BET particle diameter (D1 / D2) ratio is 1.5 or less. The present invention is related to a pigment composition, a paint, an ink, a glaze, a film, and a molding including the colored silica sol.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a colored silica sol containing core-shell type silica particles, wherein the core-shell type silica particles are doped with a transition metal, and a method for producing the same (hereinafter, also referred to as a core-shell type transition metal-doped colored silica sol).

Background Art

[0002] Conventionally, pigments have been widely used as colorants for applications such as inks, paints, plastics, rubbers, fibers, and toners. These pigments are broadly classified into two types: organic pigments and inorganic pigments. Generally, organic pigments are superior to inorganic pigments in terms of color vividness, coloring power, and chemical resistance, but tend to have low light resistance, heat resistance, and solvent resistance (see Non-Patent Document 1). In addition, for applications such as color filters and inkjet inks, high transparency of the pigment as a colorant is required, and by reducing the particle size of the organic pigment by various methods, light scattering is reduced and transparency is increased (see Non-Patent Documents 2 and 3).

[0003] By the way, as one of the methods for coloring glass mainly composed of silica, a method of doping the glass with a transition metal is known. Many of these colored glasses have high light resistance and are used, for example, in highly artistic handicrafts, ornaments, containers, furniture, and building materials such as stained glass and cut glass (see Non-Patent Document 4).

[0004] Similarly, various techniques for providing silica particles containing a transition metal have been proposed. For example, Patent Document 1 discloses a method of obtaining a silica sol having a mass ratio of Cu to silica (Cu / silica) of about 0.0007 by adding an aqueous solution of active silica and Cu(NO 3 ) 2 ·3H 2 O to a heel solution of silica / alkali (molar ratio) of 44.9 with an aqueous solution of active silica as a feed solution. Patent Document 2 discloses using a silica sol having an average particle size of 76 nm that does not contain a transition metal as a core and CuSO 4A method is disclosed for obtaining a silica sol with an average particle size of 89 nm and a mass ratio of Cu to silica (Cu / silica) of about 0.0005 by coating a mixed layer in which Cu is dispersed in silica using an aqueous solution containing active silicic acid. Patent Document 3 discloses a method for obtaining amorphous silica particles with a volume average particle size of 0.15 μm and a mass ratio of Fe to silica (Fe / silica) of about 0.009 by burning metallic silicon and an Fe source in an atmosphere in which oxygen is present. Patent Document 4 discloses a method for obtaining silica particles with a mass ratio of Cu to silica (Cu / silica) of about 0.04 by bringing silica particles with an average particle size of 0.75 μm prepared by the sol-gel method into contact with a CuSO 4 aqueous solution. Patent Document 5 discloses a method for obtaining porous silica powder with a specific surface area exceeding 1000 m 2 / g and a mass ratio of Co to silica (Co / silica) of about 0.01. Patent Document 6 discloses a method for obtaining silica particles with a mass ratio of Cu to silica (Cu / silica) of about 0.05 by bringing a hollow silica sol with an average particle size of 61 nm into contact with a CuSO 4 aqueous solution.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Non-Patent Documents

[0006]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Non-Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0007] Generally, it is known that the transparency of organic pigments increases by reducing the particle size. However, in that case, the light resistance is also likely to decrease, and it is difficult to achieve both transparency and light resistance. On the other hand, the silica particles containing transition metals proposed in Patent Documents 1 and 2 above have a small amount of transition metals and insufficient coloring power. In addition, the transition metals present near the particle surface are likely to be affected by external factors and the light resistance is also likely to decrease. The silica particles containing transition metals proposed in Patent Documents 3 and 4 above have a large particle size, so the light scattering is large and the transparency is insufficient. The silica particles containing transition metals proposed in Patent Documents 5 and 6 above are likely to have insufficient coloring power because transition metals serving as coloring components cannot exist in the pore portions of the porous structure or the hollow structure.

[0008] The present invention has been made to solve the above problems, and an object thereof is to provide a core-shell type transition metal-doped colored silica sol excellent in transparency, light resistance, and coloring property, a method for producing the same, and a pigment composition, paint, ink, glaze, film or molded body containing at least the core-shell type transition metal-doped colored silica sol.

Means for Solving the Problems

[0009] As a result of intensive studies to solve the above problems, the present inventors have completed the following present invention. That is, the present invention is as follows. In a first aspect, the present invention provides a colored silica sol containing core-shell type silica particles, wherein the core-shell type silica particles are doped with a transition metal, and the colored silica sol satisfies the following conditions (1) to (4): a colored silica sol; (1) The mass ratio of the transition metal T to silica (T / silica) is 0.0001 or more and 0.05 or less. (2) The number average particle diameter (D1) of the core-shell type silica particles in the colored silica sol calculated by an image analysis method from an electron microscope image is 5 nm or more and less than 50 nm. (3) The BET particle diameter (D2) of the core-shell type silica particles in the colored silica sol calculated by the nitrogen adsorption method is 5 nm or more and less than 50 nm. (4) The ratio of the number average particle diameter to the BET particle diameter (D1 / D2) is 1.5 or less. In a second aspect, the colored silica sol according to the first aspect, wherein the transition metal T is one or more selected from V, Cr, Mn, Fe, Co, Ni, and Cu. In a third aspect, the colored silica sol has a specific surface area SSA of the core-shell type silica particles in the colored silica sol obtained by the nitrogen adsorption method of 50 m 2 / g or more and 550 m 2 / g or less, the colored silica sol according to the first or second aspect. In a fourth aspect, the colored silica sol has a particle density PD of the core-shell type silica particles in the colored silica sol of at least 2.10 g / cm 3 or more, the colored silica sol according to any one of the first to third aspects. In a fifth aspect, the dried powder obtained by drying the colored silica sol at 100 °C in the air is amorphous, the colored silica sol according to any one of the first to fourth aspects. As a sixth aspect, the colored silica sol is characterized in that core-shell type silica particles in the colored silica sol are dispersed in an aqueous dispersion medium at a silica concentration of 1% by mass or more and 50% by mass or less. The colored silica sol according to any one of the first to fifth aspects. As a seventh aspect, the colored silica sol is such that the average particle diameter (D3) of the core-shell type silica particles in the colored silica sol by the dynamic light scattering method is 5 nm or more and less than 100 nm. The colored silica sol according to any one of the first to sixth aspects. As an eighth aspect, the colored silica sol is such that the existing concentration of transition metal T present in the dispersion medium of the colored silica sol is less than 0.002% by mass. The colored silica sol according to any one of the first to seventh aspects. As a ninth aspect, the colored silica sol is subjected to a UV irradiation test under the conditions of a UV irradiation intensity of 0.89 W / m 2 at a temperature of 50 °C and an irradiation time of 500 h using a UVA-340 type lamp. Before and after the test, The colored silica sol according to any one of the first to eighth aspects, wherein the absorbance change rate represented by the following formula (3) at the absorption wavelength causing the coloring of the colored silica sol by visible ultraviolet spectrum analysis is 50 to 100%: Absorbance change rate (%) = [Absorbance after UV irradiation / Absorbance before UV irradiation] × 100 (3), As a tenth aspect, a method for producing a colored silica sol containing core-shell type silica particles, wherein the core-shell type silica particles are doped with a transition metal, and the following steps (a), (b), (c), (d), (e) and (f); (a) A step of bringing an aqueous alkaline silicate solution into contact with a cation exchange resin to prepare an active aqueous silicate solution. (b) A step of mixing one or more selected from an aqueous alkaline silicate solution, an active aqueous silicate solution, an aqueous alkaline solution, and a transition metal salt compound to prepare a heel liquid having a silica / alkali (molar ratio) of less than 30. (c) A step of preparing a feed liquid composed of one or more selected from an active aqueous silicate solution, a transition metal salt compound, and an aqueous alkaline solution. (d) While maintaining the heel liquid in the container at 60°C or higher and 105°C or lower, adding the feed liquid to the heel liquid to synthesize silica sol containing silica particles doped with a transition metal, (e) After the step (d), while maintaining the heel liquid in the container at 60°C or higher and 105°C or lower, adding an aqueous solution of active silicic acid to the heel liquid to form the silica particles doped with the transition metal into core-shell type silica particles, and obtaining a colored silica sol containing the core-shell type silica particles, (f) After the step (e), maintaining at an arbitrary temperature of 60°C or higher and 105°C or lower for a certain period of time to obtain a sizing liquid, including, However, the transition metal salt compound is added during the preparation of the heel liquid, during the preparation of the feed liquid, or during the production of both, and / or the transition metal salt compound is contained in at least one of the aqueous alkali silicate solution, the aqueous solution of active silicic acid, and the aqueous alkali solution, The produced core-shell type silica particles have a mass ratio of transition metal T to silica (T / silica) of 0.0001 or more and 0.05 or less, and the number average particle diameter D1 calculated by the image analysis method from the electron microscope image is 5 nm or more and less than 50 nm, and the BET particle diameter D2 calculated by the nitrogen adsorption method is 5 nm or more and less than 50 nm, and the ratio of the number average particle diameter to the BET particle diameter (D1 / D2) is 1.5 or less, A method for producing a colored silica sol, As a 11th aspect, after the step (f), further having a step (g) of concentrating the colored silica sol containing the core-shell type silica particles to obtain a concentrated liquid, the method for producing a colored silica sol according to the 10th aspect, As a 13th aspect, the aqueous alkali silicate solution is one or more selected from an aqueous lithium silicate solution, an aqueous sodium silicate solution, and an aqueous potassium silicate solution, the method for producing a colored silica sol according to the 10th aspect or the 11th aspect, As a 13th aspect, the method for producing a colored silica sol according to any one of the 10th to 12th aspects, wherein the aqueous alkali solution is one or more selected from aqueous solutions of lithium hydroxide, sodium hydroxide, potassium hydroxide, and ammonia. As a 14th aspect, the method for producing a colored silica sol according to any one of the 10th to 13th aspects, wherein the metal of the transition metal salt compound is one or more selected from V, Cr, Mn, Fe, Co, Ni, and Cu. As a 15th aspect, the method for producing a colored silica sol according to any one of the 10th to 14th aspects, wherein the specific surface area of the core-shell type silica particles in the colored silica sol obtained by the nitrogen adsorption method is 50 m 2 / g or more and 550 m 2 / g or less. As a 16th aspect, the method for producing a core-shell type transition metal-doped colored silica sol according to any one of the 10th to 15th aspects, wherein the particle density of the core-shell type silica particles in the colored silica sol is at least 2.10 g / cm 3 or more. As a 17th aspect, the method for producing a colored silica sol according to any one of the 10th to 16th aspects, wherein the dried powder obtained by drying the colored silica sol at 100 °C in the air is amorphous. As a 18th aspect, the method for producing a colored silica sol according to any one of the 10th to 17th aspects, wherein the core-shell type silica particles in the colored silica sol are dispersed in an aqueous dispersion medium at a silica concentration of 1% by mass or more and 50% by mass or less. As a 19th aspect, the method for producing a colored silica sol according to any one of the 10th to 18th aspects, wherein the average particle diameter (D3) of the core-shell type silica particles in the colored silica sol by the dynamic light scattering method is 5 nm or more and less than 100 nm. As a 20th aspect, the method for producing a colored silica sol according to any one of the 10th to 19th aspects, wherein the existing concentration of the transition metal T dissolved in the dispersion medium of the colored silica sol is less than 0.002% by mass. As a 21st aspect, a pigment composition containing at least the colored silica sol according to any one of the 1st to 9th aspects, As a 22nd aspect, a paint, ink or glaze containing at least the pigment composition according to the 21st aspect, As a 23rd aspect, a printed matter, film or molded article containing at least the pigment composition according to the 21st aspect.

Advantages of the Invention

[0010] According to the present invention, it is possible to provide a core-shell type transition metal-doped colored silica sol excellent in transparency, light resistance and coloring property, and a method for producing the same.

[0011] Furthermore, this core-shell type transition metal-doped colored silica sol of the present invention can be used as a pigment composition as a colorant for various applications. By blending this pigment composition with a resin or the like, paints, inks, glazes, printed matters, films or molded articles can be produced. In addition, since the core-shell type transition metal-doped colored silica sol of the present invention has high light resistance, it is difficult to change color or fade, and long-term use can be expected in various applications.

Brief Description of the Drawings

[0012]

Figure 1

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Figure 7

Mode for Carrying Out the Invention

[0013] The present invention is directed to a colored silica sol containing core-shell type silica particles and a method for producing the same, as described below. The core-shell type silica particles are silica particles doped with a transition metal. Here, the "core-shell type (particles)" in the "core-shell type silica particles" targeted by the present invention means that it has a core region at the center of the particle and a shell region located outside the core region, and the component (type) constituting the core region is different from the component (type) constituting the shell region, or there is a mode in which the content of the common component contained in the core region and the shell region is different between the core region and the shell region. The former includes the mode of (1) below, and the latter includes the modes of (1) and (2) below: (1) A mode in which a clear boundary exists between the core region and the shell region (corresponding to a mode in which the core region (core particles) is covered with the shell region (shell layer)) (2) There is no distinct boundary between the core region and the shell region, and the content of the component changes (decreases) as it progresses from the core region at the center of the particle to the shell region.

[0014] The core-shell type silica particles according to the present invention are doped with a transition metal as described above, and the transition metal is necessarily doped in the aforementioned core region. In the mode of (1) above, the shell region is substantially not doped with a transition metal (the inclusion as inevitable impurities is recognized), or the amount of the transition metal doped in the shell region is less than that in the core region. In the case of this mode, for example, the mass ratio of the transition metal T to silica in the core region (T / silica) can be 0.001 or more and 0.05 or less. Also, the mode of (2) is a mode in which the doping amount of the transition metal decreases as it progresses from the core region at the center of the particle to the shell region. At this time, there is no distinct boundary between the core region and the shell region.

[0015] In the aforementioned mode (1), the mode of "the core region is covered with the shell region" includes both the mode in which the surface of the core region is covered by the shell region and the mode in which the components constituting the shell region are bonded to the surface of the core region. The former mode of "the surface of the core region is covered by the shell region" may be any mode in which the shell region covers at least a part of the surface of the core region. That is, it includes the mode in which the shell region covers a part of the surface of the core region (the mode in which the shell region exists on a part of the surface of the core region) and the mode in which the shell region covers the entire surface of the core region (the mode in which the shell region exists on the entire surface of the core region). In this mode, the presence or absence of the bond between the shell region and the surface of the core region is not questioned. Also, the latter mode of "the components constituting the shell region are bonded to the surface of the core region" may be any mode in which the components constituting the shell region are bonded to at least a part of the surface of the core region. That is, That is, it includes modes in which the components constituting the shell region are bonded to a part of the surface of the core region, modes in which the components constituting the shell region are bonded to a part of the surface of the core region and cover at least a part of the surface, and further modes in which the components constituting the shell region are bonded to the entire surface of the core region and cover the entire surface, etc.

[0016] As described above, hereinafter in this specification, a colored silica sol containing core-shell type silica particles in which the core-shell type silica particles are doped with a transition metal is referred to as a "core-shell type transition metal doped colored silica sol". Hereinafter, the present invention will be described in detail.

[0017] [Core-shell type transition metal doped colored silica sol] The present invention is directed to a core-shell type transition metal doped colored silica sol satisfying the following (1) to (4). (1) The mass ratio of the transition metal T to silica (T / silica) is 0.0001 or more and 0.05 or less. (2) The number average particle diameter (D1) of the core-shell type silica particles in the colored silica sol calculated by the image analysis method from the electron microscope image is 5 nm or more and less than 50 nm. (3) The BET particle diameter (D2) of the core-shell type silica particles in the colored silica sol calculated by the nitrogen adsorption method is 5 nm or more and less than 50 nm. (4) The ratio of the number average particle diameter to the BET particle diameter (D1 / D2) is 1.5 or less.

[0018] Regarding the above (1), the core-shell type transition metal-doped colored silica sol of the present invention contains core-shell type silica particles, and the core-shell type silica particles are colored silica sol doped with a transition metal T, and the mass ratio of the transition metal T to the silica (T / silica) is 0.0001 or more and 0.05 or less. Preferably, the mass ratio (T / silica) is 0.0005 or more and 0.02 or less. When the mass ratio (T / silica) is less than 0.0001, the coloring property becomes insufficient, and when it is greater than 0.05, it is difficult to be doped well into the silica particles, so it is not preferable. The doping amount of this transition metal T can be analyzed and quantified by inductively coupled plasma optical emission spectrometry (ICP-OES), inductively coupled plasma mass spectrometry (ICP-MS), atomic absorption spectrometry (AA), X-ray fluorescence analysis (XRF), etc. after performing known appropriate pretreatment on the colored silica sol. The transition metal T may be doped unevenly or uniformly distributed in the core region of the core-shell type silica particles described above. Also, in the shell region of the core-shell type silica particles, the transition metal T is not doped (excluding inevitable impurities), or even if it is doped, the doping amount of the transition metal T can be made less than that in the core region, and in a preferred embodiment, the transition metal T is intentionally not doped (excluding inevitable impurities) in the shell region.

[0019] Regarding the above (2), the particle diameter of the core-shell type silica particles in the core-shell type transition metal doped colored silica sol is such that the number average particle diameter (D1) calculated by the image analysis method from the electron microscope image is 5 nm or more and less than 50 nm. Preferably, the number average particle diameter (D1) is 7 nm or more and 30 nm or less. When the number average particle diameter (D1) is less than 5 nm, the particles tend to aggregate with each other, resulting in poor dispersibility when made into a dispersion. When it is more than 50 nm, the light scattering such as Rayleigh scattering and Mie scattering becomes strong, deteriorating the transparency, which is not preferable. The number average particle diameter (D1) of the core-shell type silica particles in the colored silica sol can be obtained by the following procedure. That is, after performing appropriate known pretreatment on the colored silica sol, it is observed with a transmission electron microscope (TEM), a scanning electron microscope (SEM), or a scanning transmission electron microscope (STEM), etc. From the electron microscope image of the obtained colored silica sol, the area of the core-shell type silica particles is determined by the image analysis method, and the equivalent circle diameter, which is the diameter of a perfect circle equal to the area, is obtained. The number average value of this equivalent circle diameter can be taken as the number average particle diameter (D1).

[0020] Regarding the above (3), the particle diameter of the core-shell type silica particles in the core-shell type transition metal doped colored silica sol is such that the BET particle diameter (D2) calculated from the nitrogen adsorption method (BET method) is 5 nm or more and less than 50 nm. Preferably, the BET particle diameter (D2) is 7 nm or more and 30 nm or less. When the BET particle diameter (D2) is less than 5 nm, the particles tend to aggregate with each other, resulting in poor dispersibility when made into a dispersion. When it is more than 50 nm, the light scattering such as Rayleigh scattering and Mie scattering becomes strong, deteriorating the transparency, which is not preferable. The BET particle diameter of the core-shell type silica particles in the colored silica sol is the particle diameter calculated by the following formula (1) from the specific surface area SSA (m 2 / g) and the particle density PD (g / cm 3 ) of the particles measured by the nitrogen adsorption method (BET method), and means the diameter in terms of spherical particles having the same specific surface area; BET particle diameter D2 (nm) = 6000 / [particle density PD (g / cm 3 ) × specific surface area SSA (m 2 / g)] (1)

[0021] Regarding the above (4), for the core-shell type transition metal-doped colored silica sol, the ratio of the number average particle diameter to the BET particle diameter (D1 / D2) is 1.5 or less. Preferably, D1 / D2 is 1.3 or less. Also, the lower limit value of D1 / D2 can be selected from the range of 0.1 or more, or 0.3 or more, or 0.5 or more, or 0.8 or more, or 1.0 or more. The core-shell type silica particles in the colored silica sol preferably have a non-porous structure and a non-hollow structure and are substantially solid particles. When D1 / D2 is greater than 1.5, the porosity or hollowness of the core-shell type silica particles increases, and transition metals serving as coloring components cannot exist in the pore portions of the porous structure or hollow structure, making the coloring power likely to be insufficient, which is not preferable. It is considered that the smaller the ratio of the number average particle diameter to the BET particle diameter (D1 / D2), the more solid the particles become.

[0022] In addition, regarding the distinction between solid particles and porous particles or hollow particles, when observed with a transmission electron microscope (TEM), it can also be discriminated by the difference in the contrast of the particles.

[0023] In the core-shell type transition metal-doped colored silica sol, in the case where the core-shell type silica particles have a clear boundary between the core region and the shell region (the mode in which the core region is covered by the shell region, in this case, the core region may be referred to as core particles), the thickness of the shell region (shell thickness) can be, for example, 0.3 nm or more and 5 nm or less, and also, for example, the shell thickness can be 0.4 nm or more and 4 nm or less. By setting the shell thickness to 0.3 nm or more, the core region doped with transition metals can be sufficiently covered, which can lead to the improvement of light resistance. Also, by setting the shell thickness to 5 nm or less, it becomes possible to ensure the coloring power of the transition metals doped in the core region, which can lead to the realization of a sol with excellent coloring properties. As described above, the shell region of the core-shell type silica particles may be partially covered or completely covered by the shell region on the surface of the core region, but it is preferably completely covered and has a non-porous structure. The shell thickness of the core-shell type silica particles in the colored silica sol can be obtained by calculating according to the following formula (2); Shell thickness = (number average particle diameter (D1) of the core-shell type silica particles - number average particle diameter (D1) of the core particles (silica particles in the core region) used for the production of the core-shell type silica particles) ÷ 2 (2) The shell thickness may be calculated using the BET particle diameter (D2) instead of the number average particle diameter (D1).

[0024] Note that the particle shape of the core-shell type silica particles in the colored silica sol is not particularly limited. For example, spherical, ellipsoidal (rugby ball) shape, cocoon shape, confetti shape, chain shape, dice shape, etc. may be mentioned. Among them, spherical particles are preferable because of their high dispersibility and small light scattering.

[0025] Note that the particle size distribution of the core-shell type silica particles in the colored silica sol is not particularly limited. For example, a single peak particle size distribution, or a particle size distribution with two or more peaks, a particle size distribution with a narrow half-value width, and a particle size distribution with a wide half-value width may be mentioned. Among them, a single peak particle size distribution with a narrow half-value width is preferable because of its small light scattering.

[0026] The transition metal T is preferably one or more selected from the elements existing between the Group 3 elements and the Group 11 elements of the periodic table, and can be appropriately selected according to the absorption wavelength band. The transition metal T may be doped alone in the core-shell type silica particles, or a plurality of transition metals T of multiple elements may be doped simultaneously in the core-shell type silica particles. Alternatively, after producing a colored silica sol doped with a single type of transition metal T in the core-shell type silica particles, a colored silica sol doped with another type of transition metal T may be produced, and these colored silica sols may be mixed in plurality. The transition metal T is preferably one or more selected from the transition metals of the first transition series, and more preferably one or more selected from V, Cr, Mn, Fe, Co, Ni, and Cu.

[0027] The core-shell type transition metal-doped colored silica sol is such that the specific surface area SSA of the core-shell type particles in the colored silica sol obtained by the nitrogen adsorption method is 50 m 2 / g or more and 550 m 2 / g or less. The specific surface area SSA is preferably 90 m 2 / g or more and 400 m 2 / g or less. If the specific surface area is less than 50 m 2 / g, transparency is likely to be lost when the colored silica sol is used in a resin composite material or the like. On the other hand, if the specific surface area is greater than 550 m 2 / g, there is a concern that the dispersibility in the dispersion medium or resin may decrease, making it difficult to add at a high concentration. In addition, there is also a possibility that the silica particles may have a porous structure.

[0028] The core-shell type transition metal-doped colored silica sol is such that the particle density PD of the core-shell type silica particles in the colored silica sol is desirably at least 2.10 g / cm 3 or more. The upper limit value of the particle density PD is 3.0 g / cm 3 , or 2.80 g / cm 3 , or 2.70 g / cm 3 , or 2.60 g / cm 3 , or 2.50 g / cm 3 , or 2.40 g / cm 3 , or 2.30 g / cm 3 , or 2.25 g / cm 3 , and it is possible to select from the range. Since the true density of bulk silica is generally 2.2 - 2.3 g / cm 3 , when it is less than 2.10 g / cm 3 , there are closed pores derived from a porous structure or a hollow structure, and the transition metal serving as the coloring component cannot exist, and the coloring power is likely to be insufficient, which is not preferable. This particle density PD can be obtained, for example, by measuring a sample obtained by heat-treating (drying) the colored silica sol at 100°C in the atmosphere using a dry-type automatic densitometer (AccuPycII 1340TEC manufactured by Micromeritics) with He gas.

[0029] It is preferable that the dry powder obtained by heat-treating (drying) the core-shell type transition metal-doped colored silica sol at 100 °C in the air is amorphous. The crystallinity of the dry powder can be confirmed by X-ray diffraction method. When no crystal phase derived from the transition metal T can be confirmed by X-ray diffraction, it is considered that the transition metal T is doped in the core-shell type silica particles. Also, cristobalite, tridymite, quartz, etc. are known as crystal phases derived from silica, but crystalline silica raises concerns about toxicity, and from the viewpoint of safety, it is preferable that these crystal phases cannot be confirmed (amorphous).

[0030] It is desirable that the core-shell type transition metal-doped colored silica sol is a silica sol in which the core-shell type silica particles in the colored silica sol are dispersed in an aqueous dispersion medium at a silica concentration of 1 mass% or more and 50 mass% or less. The silica concentration is preferably 2 mass% or more and 40 mass% or less. When it is lower than 1 mass%, the economic efficiency may be low in terms of low productivity and transportation costs. When it is larger than 50 mass%, the dispersibility may easily deteriorate due to an increase in the number of particles. The silica concentration can be calculated, for example, by removing metal elements such as the transition metal T in terms of oxide from the solid residue obtained by heat-treating (drying) the core-shell type transition metal-doped colored silica sol at a predetermined temperature and time. As the water, pure water such as ion-exchanged water, ultrafiltration water, reverse osmosis permeated water, distilled water, or ultrapure water can be used, and it can be appropriately selected according to the application, etc.

[0031] The core-shell type transition metal-doped colored silica sol preferably has an average particle diameter (D3) of the core-shell type silica particles in the colored silica sol of 5 nm or more and less than 100 nm as measured by the dynamic light scattering method. The average particle diameter (D3) is preferably 10 nm or more and less than 80 nm. The measurement of the average particle diameter (D3) by the dynamic light scattering method is based on the measurement principle of the dynamic light scattering method. For example, after the colored silica sol has been subjected to a known appropriate pretreatment, it can be measured with a dynamic light scattering particle size measuring device (Zetasizer Nano manufactured by Spectris). When it is less than 5 nm, the dispersibility in the dispersion medium and the resin tends to decrease. On the other hand, when it is more than 100 nm, the transparency deteriorates because the light scattering such as Rayleigh scattering and Mie scattering becomes strong, which is not preferable.

[0032] The core-shell type transition metal-doped colored silica sol desirably has a pH of 2 or more and 12 or less. Preferably, the pH is 2 or more and 4 or less, and 8 or more and 11 or less. When the pH of the colored silica sol is less than 2, the dispersibility may easily deteriorate, and in addition, there is a risk that the transition metal T may easily elute into the dispersion medium. When the pH is higher than 12, the silica may easily dissolve and gelate, and in addition, there is a risk that the transition metal T may easily elute into the dispersion medium due to the dissolution of the silica.

[0033] It is desirable that the core-shell type transition metal-doped colored silica sol has a real concentration of transition metal T dissolved in its dispersion medium of less than 0.002 mass% (less than 20 mass ppm). The real concentration is preferably less than 0.001 mass% (less than 10 mass ppm), more preferably less than 0.0002 mass% (less than 2 mass ppm), and still more preferably less than 0.0001 mass% (less than 1 mass ppm). When the real concentration is higher than 0.002 mass%, there are concerns about safety to the body and environmental impact. The real concentration of transition metal T dissolved in the dispersion medium of the colored silica sol can be analyzed and quantified by inductively coupled plasma optical emission spectrometry (ICP-OES), inductively coupled plasma mass spectrometry (ICP-MS), atomic absorption spectrometry (AA), etc. after performing appropriate pretreatment on the filtrate obtained by treating the silica sol with an ultrafiltration (UF) membrane or reverse osmosis (RO) membrane having an appropriate fractional molecular weight.

[0034] The core-shell type transition metal-doped colored silica sol has an absorbance change rate represented by the following formula (3) of 50 to 100% at the absorption wavelength that causes the coloring of the colored silica sol by visible ultraviolet spectrum analysis before and after a UV irradiation test under the conditions of a UV irradiation intensity of 0.89 W / m 2 , a temperature of 50°C, and an irradiation time of 500 h (equivalent to 3.6 months of sunlight) using a UVA-340 type lamp. Absorbance change rate (%) = [Absorbance after UV irradiation / Absorbance before UV irradiation] × 100 (3) The absorbance change rate before and after the UV irradiation test is preferably 60 to 100%, 70 to 100%, 75 to 100%, 80 to 100%, 85 to 100%, 90 to 100%. The UV irradiation test can be carried out, for example, by putting the core-shell type transition metal-doped colored silica sol into a quartz cell with a lid having an optical path length of 10 mm, installing it in a QUV accelerated weathering tester (manufactured by Q-Lab Corporation, trade name QUV / se), and using a UVA-340 type lamp. In addition, the absorption wavelength for measuring the absorbance to compare the rate of change varies depending on the color exhibited by the colored silica sol, that is, it varies depending on the type of transition metal T doped into the silica particles. When there are multiple absorption wavelengths derived from the transition metal T, the absorption wavelength to be compared may be appropriately selected in consideration of factors such as little influence of absorption by other factors and the magnitude of absorption. For example, but not limited to this, if it is Co, it is around 640 nm, if it is Cr, it is around 590 nm, M if it is n, it is around 455 nm, if it is Cu, it is around 640 nm, if it is Ni, it is around 670 nm, if it is V, it is around 425 nm and 625 nm, and if it is Fe, the absorbance can be compared at an absorption wavelength of around 400 nm. The closer the value of the absorbance change rate (%) is to 100%, the more it means that the absorbance has not changed due to UV irradiation, and it can be determined that the silica sol has high light resistance. In the present invention, since the absorbance change rate of the core-shell type transition metal-doped colored silica sol is 50 to 100%, it becomes a suitable silica sol that can maintain coloring even when used in an environment exposed to sunlight.

[0035] [Method for producing core-shell type transition metal-doped silica sol] The core-shell type transition metal-doped silica sol of the present invention can be produced based on a method for producing silica sol generally called the water glass method. Specifically, it can be produced in a process including the following steps (a), (b), (c), (d), (e), and (f). (a) A step of bringing an aqueous alkaline silicate solution into contact with a cation exchange resin to prepare an active aqueous silicate solution. (b) A step of mixing one or more selected from an aqueous alkaline silicate solution, an active aqueous silicate solution, an aqueous alkaline solution, and a transition metal salt compound to prepare a heel solution having a silica / alkali (molar ratio) of less than 30. (c) A step of preparing a feed solution composed of one or more selected from an active aqueous silicate solution, a transition metal salt compound, and an aqueous alkaline solution. (d) While maintaining the heel liquid in the container at 60°C or higher and 105°C or lower, adding the feed liquid to the heel liquid to synthesize silica sol containing silica particles doped with a transition metal in a particle synthesis step. (e) After the step (d), while maintaining the heel liquid in the container at 60°C or higher and 105°C or lower, adding an aqueous solution of active silicic acid to the heel liquid to form the silica particles doped with the transition metal into core-shell type silica particles, and obtaining a colored silica sol containing the core-shell type silica particles. (f) After the step (e), maintaining at an arbitrary temperature of 60°C or higher and 105°C or lower for a certain period of time to obtain a sizing liquid. In this production method, the transition metal salt compound is added during the preparation of the heel liquid, during the preparation of the feed liquid, or during the preparation of both, and / or the transition metal salt compound is contained in at least one of the aqueous alkali silicate solution, the aqueous solution of active silicic acid, and the aqueous alkali solution. The produced core-shell type silica particles have a mass ratio of transition metal T to silica (T / silica) of 0.0001 or more and 0.05 or less, and a number average particle diameter D1 calculated by an image analysis method from an electron microscope image of 5 nm or more and less than 50 nm, and a BET particle diameter D2 calculated by a nitrogen adsorption method of 5 nm or more and less than 50 nm, and a ratio of number average particle diameter / BET particle diameter (D1 / D2) of 1.5 or less.

[0036] (a) The aqueous alkali silicate solution used in the step is preferably one or more selected from an aqueous lithium silicate solution, an aqueous sodium silicate solution, and an aqueous potassium silicate solution. The aqueous alkali silicate solution may be used alone or in combination of two or more. From the viewpoint of economy, an aqueous sodium silicate solution called water glass is preferred. These aqueous alkali silicate solutions can be diluted with water and used as needed.

[0037] (a) The cation exchange resin used in the process can be appropriately selected from known ones and is not particularly limited. Preferably, it is a strongly acidic cation exchange resin. For example, in the step of contacting an alkaline silicate aqueous solution with a cation exchange resin, the alkaline silicate aqueous solution is diluted with water to obtain an aqueous solution with a silica concentration of 1% by mass or more and less than 10% by mass, and this aqueous solution is contacted with a strongly acidic cation exchange resin for deionization (deaeration). If necessary, it can also be deionized by contacting with a strongly basic anion exchange resin before and after contacting with the cation exchange resin. Details of the contact conditions have already been variously proposed in the past, and in the present invention, any of these known conditions can be adopted. It can also be deionized by contacting with a strongly basic anion exchange resin before and after contacting with the cation exchange resin. Details of the contact conditions have already been variously proposed in the past, and in the present invention, any of these known conditions can be adopted.

[0038] Specific examples of the strongly acidic cation exchange resin include Amberlite IR-120B, Amberjet 1020 (manufactured by Organo Corporation), DOWEX MARATHON GH (manufactured by Dow Chemical Company), Diaion SK104, Diaion PK208 (manufactured by Mitsubishi Chemical Group Corporation), Duolite C20J (manufactured by Sumika Chemtex Corporation), etc.

[0039] Specific examples of the strongly basic anion exchange resin include Amberlite IRA400J, Amberlite IRA410J, Amberjet 4400 (manufactured by Organo Corporation), Diaion SA10A, Diaion SA20A (manufactured by Mitsubishi Chemical Group Corporation), Duolite UBA120 (manufactured by Sumika Chemtex Corporation), etc.

[0040] The concentration of the active silicic acid aqueous solution obtained in step (a) is preferably 1% by mass or more and 6% by mass or less as silica, and more preferably 3% by mass or more and 4% by mass or less. When the silica content is less than 1% by mass, the productivity deteriorates, and when it is higher than 6% by mass, the active silicic acid aqueous solution becomes unstable and easily gels. The pH of the active silicic acid aqueous solution is preferably 1 or more and 5 or less, or preferably pH 7 or more and 12 or less, and more preferably 2 or more and 4 or less or pH 8 or more and 11 or less. Outside this pH range, the active silicic acid aqueous solution becomes unstable and easily gels.

[0041] (b) The heel liquid obtained in the process is prepared by mixing one or more selected from an alkaline silicate aqueous solution, an active silicic acid aqueous solution, an alkaline aqueous solution, and a transition metal salt compound so that the silica / alkali (molar ratio) is less than 30. If the silica / alkali (molar ratio) is greater than 30, the silica sol is likely to cause particles to fuse with each other during particle synthesis and the dispersibility is likely to decrease, which is not preferable. When preparing the heel liquid, the mixing and addition order of these aqueous solutions, etc. is not particularly limited as long as it does not adversely affect the effects of the present invention. Note that the alkaline silicate aqueous solution and the active silicic acid aqueous solution in the step (b) may be the same as or different from those used and prepared in the step (a).

[0042] (b) The alkaline aqueous solution used in the process is preferably one or more selected from aqueous solutions of lithium hydroxide, sodium hydroxide, potassium hydroxide, and ammonia. The alkaline aqueous solution may be used alone or in combination of two or more. Alkaline aqueous solutions are commercially available at various concentrations, and these commercial products can also be used and diluted with water as needed.

[0043] (b) In the transition metal salt compound used in the process, there is no particular limitation such as organic salts and inorganic salts, but it is preferably at least one selected from chloride salts, nitrate salts, sulfate salts, borate salts, and phosphate salts. The transition metal salt compound may be used alone or in combination of two or more. The transition metal salt compound is preferably used after being dissolved in water.

[0044] (b) The metal of the transition metal salt compound used in the process is preferably one or more selected from V, Cr, Mn, Fe, Co, Ni, and Cu. These metals of the transition metal salt compound may be used alone or in combination of two or more.

[0045] (c) The feed liquid obtained in the process consists of one or more selected from an aqueous solution of active silicic acid, a transition metal salt compound, and an aqueous alkali solution. It may be used alone or in combination of two or more. When preparing the feed liquid, the order of mixing these aqueous solutions, etc. is not particularly limited as long as it does not adversely affect the effects of the present invention. If necessary, an aqueous acid solution such as hydrochloric acid, nitric acid, and sulfuric acid, or the above-mentioned aqueous alkali solution may be added to adjust the pH to a value at which the aqueous solution of active silicic acid is likely to be stable. Note that the aqueous solution of active silicic acid in step (c) may be the same as or different from that used and prepared in step (a) and / or step (b). Also, the aqueous alkali solution and the transition metal salt compound in step (c) may be the same as or different from those used in step (b). Note that the transition metal salt compound may be added during the preparation of the heel liquid or the feed liquid, or may originally be contained in the alkali silicate aqueous solution, the aqueous solution of active silicic acid, or the aqueous alkali solution, or both. That is, the transition metal salt compound is added during the preparation of the heel liquid in step (b), during the preparation of the feed liquid in step (c), or both, and / or the transition metal salt compound is contained in at least one of the alkali silicate aqueous solution, the aqueous solution of active silicic acid, and the aqueous alkali solution.

[0046] (d) The liquid temperature of the heel liquid in the process is 60°C or higher and 105°C or lower. Preferably, it is 70°C or higher and 100°C or lower. If it is less than 60°C, the reactivity of particle synthesis is low, which is not preferable. In this process, when using multiple types of feed liquids, each type may be added individually, or two or more types may be added simultaneously. The rate of adding the feed liquid to the heel liquid can be appropriately set for each. The silica particles doped with a transition metal obtained by this process may be referred to as "core particles" when compared with the core-shell type silica particles described later. Also, the "silica sol containing silica particles doped with a transition metal (core particles)" obtained in this process is a sol colored by the silica particles doped with a transition metal (colored silica sol). However, to avoid confusion with the "colored silica sol (including core-shell type silica particles)" obtained in the subsequent step (e), for convenience, the "(colored) silica sol containing core particles" may simply be referred to as "silica sol".

[0047] (e) The liquid temperature of the heel liquid in the process is 60°C or higher and 105°C or lower. Preferably, it is 70°C or higher and 100°C or lower. If it is less than 60°C, the reactivity of the active silicic acid is low, and it becomes difficult to form a shell region (shell layer) on the surface of the particles (core region), which is not preferable. The rate of adding the active silicic acid aqueous solution to the heel liquid can be appropriately set for each. After the completion of step (d), it may be cooled to room temperature once and then heated again to proceed to step (e). If necessary, the acid aqueous solution and the alkaline aqueous solution may be further added to adjust the pH to a value at which it is easy to form a shell region (shell layer) on the surface of the particles (core region), and then proceed to step (e).

[0048] (f) In the process, after the process (e), it is maintained at any temperature from 60°C to 105°C for a certain period of time to obtain a sizing liquid. The maintenance time is preferably between 0.5 hours and 24 hours. If it is shorter than 0.5 hours, unreacted active silica remains in the system and the dispersibility is likely to deteriorate, which is not preferable. If it is longer than 24 hours, it is not preferable from the perspective of productivity. Before performing the process (f), if necessary, an aqueous acid solution such as hydrochloric acid, nitric acid, and sulfuric acid, or the aqueous alkali solution may be further added to adjust the pH.

[0049] Furthermore, after the process (f), a process (g) of concentrating the colored silica sol to obtain a concentrated liquid can be included. In this concentration process (g), for example, the silica concentration can be adjusted to 1% by mass or more and 50% by mass or less by concentration using an ultrafiltration (UF) membrane, or by evaporation concentration under reduced pressure or normal pressure.

[0050] [Pigment Composition] The pigment composition of the present invention is not particularly limited as long as it contains at least the core-shell type transition metal-doped colored silica sol of the present invention. In this pigment composition, the core-shell type silica particles doped with transition metal in the core-shell type transition metal-doped colored silica sol can be used as a pigment as it is, to form a dispersion liquid pigment composition, or a solid residue obtained by heat-treating (drying) the core-shell type transition metal-doped colored silica sol at an appropriate treatment temperature and an appropriate treatment time can be used to form a powdery pigment composition. This powder may be pulverized by a known technique and further classified for use. Also, the pigment composition may be color-matched by mixing a plurality of types of core-shell type transition metal-doped colored silica sols with different elements in an arbitrary mixing ratio, or may be color-matched by adding another type of pigment.

[0051] As another type of pigment, inorganic pigments and organic pigments can be used. As the above pigments, inorganic white pigments such as titanium oxide, zinc oxide, mica, etc.; inorganic black pigments such as carbon black, graphite, iron black, copper-chromium black, cobalt-chromium black, copper-manganese-iron black, etc.; inorganic red-orange pigments such as red iron oxide, etc.; inorganic yellow pigments such as yellow iron oxide, titanium yellow, titanium-antimony-chromium yellow, etc.; inorganic green pigments such as chromium green, dichromium trioxide, cobalt green, cobalt-titanium-nickel-zinc-based green, cobalt-aluminum-chromium-based blue-green, etc.; inorganic blue pigments such as ultramarine blue, Berlin blue, cobalt blue, etc.; organic red-orange pigments such as permanent red 4R, brilliant carmine FB, permanent red F5RK, pyrazolone orange, pyrazolone red, benzimidazolone orange, permanent red 2B, lake red R, Bordeaux 10B, bon maroon light, thioindigo Bordeaux, anthraquinone red, anthantrone red, perylene red, perylene scarlet, perylene maroon, quinacridone red, dichloroquinacridone magenta, quinacridone magenta, etc.; organic yellow pigments such as first yellow FGL, benzimidazolone yellow H3G, benzimidazolone yellow H4G, diarylide yellow HR, isoindoline yellow, anthrapyrimidine yellow, nickel azo yellow, quinophthalone yellow, etc.; organic green pigments such as chlorinated phthalocyanine green, brominated phthalocyanine green, etc.; organic blue pigments such as phthalocyanine blue α, metal-free phthalocyanine blue, threne blue, etc.; organic purple pigments such as dioxane violet, quinacridone violet, etc.; extender pigments such as calcium carbonate, kaolin, diatomaceous earth, silica, talc, barium sulfate, barium carbonate, etc. can be mentioned. From the viewpoint of light resistance, inorganic pigments are particularly preferred.

[0052] Furthermore, the pigment composition can be mixed with a dispersion medium such as water and / or a water-soluble organic solvent, a resin (plastic), a glass raw material, an additive, etc., as necessary. The mixing order can be added in any order as long as it does not affect the effects of the present invention. The pigment composition after mixing may be used in a state of maintaining the dispersion liquid (liquid state), or may be heat-treated (dried) at an appropriate treatment temperature and treatment time and used in a powder form. Alternatively, after the core-shell type transition metal-doped colored silica sol is first made into a powder form, the resin, additive, etc. can be mixed and used as it is in a powder form, or the dispersion medium, etc. can be added thereto and dispersion treatment can be performed to use it as a dispersion liquid. From the viewpoint of transparency, it is particularly preferable to use the pigment composition while maintaining the state of the dispersion liquid.

[0053] As the water-soluble organic solvent, alcohol, ether, ester or ketone can be used. Examples of the water-soluble organic solvent include monoalcohol solvents such as methanol, ethanol, 1-propanol, 2-propanol, tert-butanol, and diacetone alcohol; polyhydric alcohol solvents such as ethylene glycol and propylene glycol; aromatic alcohol solvents such as furfuryl alcohol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monotert-butyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, di Ether-ester solvents such as ethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, 3-methoxybutanol, 3-methyl-3-methoxybutanol, ethylene glycol monomethyl ether acetate, ethyl 2-hydroxypropionate, ethyl hydroxyacetate, γ-butyrolactone, tetrahydrofuran, 1,4-dioxane; ketone solvents such as acetone, 4-hydroxy-4-methyl-2-pentanone; and nitrogen-containing solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, etc. These may be used alone or in combination of two or more.

[0054] As the resin (plastic), known resins can be used. For example, thermoplastic resins, thermosetting resins, photocurable resins, etc. can be mentioned. Examples of thermoplastic resins include vinyl chloride (PVC) resin, polyethylene (PE) resin, polypropylene (PP) resin, polystyrene (PS) resin, acrylonitrile-butadiene-styrene (ABS) resin, acrylonitrile-styrene (AS) resin, thermoplastic acrylic (e.g., polymethyl methacrylate: PMMA) resin, polyvinyl alcohol (PVA) resin, vinyl acetate (PVAc) resin, polyvinylidene chloride (PVDC) resin, polyethylene terephthalate (PET) resin, polyamide (PA) resin, polyacetal (POM) resin, polycarbonate (PC) resin, modified polyphenylene ether (m-PPE) resin, polybutylene terephthalate (PBT) resin, ultra-high molecular weight polyethylene (U-PE) resin, polyvinylidene fluoride (PVDF) resin, polysulfone (PSU) resin, polyethersulfone (PESU) resin, polyphenylene sulfide (PPS) resin, polyarylate (PAR) resin, polyamideimide (PAI) resin, polyetherimide (PEI) resin, polyetheretherketone (PEEK) resin, thermoplastic polyimide (TPI) resin, liquid crystal polymer (LCP) resin, polytetrafluoroethylene (PTFE) resin, polymethyl terpene (PMP) resin, polyphenylene oxide (Noryl, PPO) resin, thermoplastic polyurethane (TPU) resin, coumarone resin, ionomer (ION) resin, polyester-based thermoplastic elastomer, rosin, cellulose acetate (CA) resin, polylactic acid (PLA) resin, polybutylene succinate (PBS) resin, polycaprolactone (PCL) resin, polyglycolic acid (PGA) resin, polyhydroxyalkanoic acid (PHA) resin, polyvinyl butyral resin (PVB), polyacrylonitrile (PAN) resin, etc.Examples of the thermosetting resin include phenol (PF) resin, urea (UF) resin, melamine (MF) resin, unsaturated polyester (UP) resin, epoxy (EP) resin, silicone (SI) resin, polyurethane (PU) resin, diallyl phthalate (PDAP) resin, polyimide (PI) resin, thermosetting acrylic (TPA) resin, liquid polybutadiene, silicone rubber, shellac, furan resin, casein resin, etc. Examples of the photocurable resin include vinyl-based photocurable resin, acrylic-based photocurable resin, epoxy-based photocurable resin, urethane-based photocurable resin, polyester-based photocurable resin, etc. These resins may be used alone, in combination of two or more, or as copolymers or modified products of two or more.

[0055] The resin is preferably a soluble resin dissolved in water and / or a water-soluble organic solvent, or a dispersed resin dispersed in a colloid or emulsion.

[0056] Known glass raw materials can be used as the glass raw materials. For example, silica sand, feldspar, calcite, sodium silicate, calcium carbonate, lithium carbonate, sodium carbonate, sodium sulfate, sodium nitrate, potassium carbonate, potassium nitrate, barium carbonate, barium nitrate, limestone, dolomite, magnesium oxide, borax, boric acid, phosphoric acid, aluminum hydroxide, lead oxide, sodium fluorosilicate, zinc oxide, titanium oxide, zirconium oxide, etc. These may be used alone or in combination of two or more. The glass raw materials can also be used as raw materials for glaze.

[0057] Known additives can be used as the additives. Examples of the additives include wetting agents, dispersants, penetrants, desiccants, drying inhibitors, defoamers, viscosity modifiers, pH adjusters, chelating agents, plasticizers, crosslinking agents, curing catalysts, radical generators, acid generators, sensitizers, polymerization inhibitors, antioxidants, ultraviolet absorbers, leveling agents, lubricants, flame retardants, antistatic agents, rust preventives, preservatives, algaecides, antibacterial agents, antifungal agents, antiviral agents, etc. These additives may be used alone or in combination of two or more kinds.

[0058] These mixing and dispersion processes can be carried out using a mixing and dispersing machine such as a stirring blade, a paint shaker, a bead mill, a ball mill, a dissolver, a kneader, etc. in a container. When the miscibility and dispersibility are poor at room temperature, heating may be carried out as necessary.

[0059] Furthermore, this pigment composition may be subjected to classification treatment by a sieve, centrifugation treatment, filtration treatment, etc. before and after mixing to remove unnecessary foreign matters.

[0060] When the pigment composition is used as a dispersion, the concentration of the pigment (core-shell type silica particles in the core-shell type transition metal-doped colored silica sol and, if desired, other pigments) in the pigment composition can be 1% by mass or more and 50% by mass or less in 100% by mass of the pigment composition. Preferably, it is 2% by mass or more and 40% by mass or less. When the pigment concentration in the pigment composition (dispersion) is less than 1% by mass, the coloring property is low due to the small amount of coloring components, and when it is more than 50% by mass, the dispersibility is likely to deteriorate due to the increase in the number of particles, which is not preferable. On the other hand, when the pigment composition is used as a powder, the concentration of the pigment can be 1% by mass or more and 100 or less in 100% by mass of the pigment composition. Preferably, it is 5% by mass or more and 90% by mass or less. When the pigment concentration in the pigment composition (powder) is less than 1% by mass, the coloring property is low due to the small amount of coloring components, which is not preferable.

[0061] Regarding the proportion of the dispersion medium such as water and water-soluble organic solvents in the pigment composition, when the pigment composition is used as a dispersion liquid, it can be 50% by mass or more and 99% by mass or less in 100% by mass of the pigment composition. On the other hand, when the pigment composition is used as a powder, it is preferably free of these dispersion media as much as possible.

[0062] The proportion of the resin in the pigment composition is not particularly limited, but it is 0% by mass or more and 50% by mass or less in 100% by mass of the pigment composition. Preferably, it is 1% by mass or more and 50% by mass or less. When the resin is blended in the pigment composition, it is preferably 1% by mass or more.

[0063] When the pigment composition contains a resin, the mass ratio of the pigment to the resin (pigment / resin) is 1 / 99 or more and 99 / 1 or less. Preferably, it is 5 / 95 or more and 95 / 5 or less.

[0064] The proportion of the additive in the pigment composition is the balance in 100% by mass of the pigment composition, specifically, 0% by mass or more and 10% by mass or less in 100% by mass of the pigment composition.

[0065] [Paint, Ink, Glaze] The pigment composition of the present invention can be used as a paint, ink or glaze. That is, the present invention also targets the paint, ink or glaze containing at least the pigment composition.

[0066] [Printed Matter, Film, Molded Body] The present invention also targets a printed matter, film or molded body containing at least the pigment composition.

[0067] The printed matter or film of the present invention has no particular limitation as long as it contains at least the pigment composition of the present invention. Here, the printed matter means an object on which characters, images such as pictures and photographs are printed on a substrate with ink. The film may be a coating film applied to a substrate or a self-supporting film. Here, the coating film means a film formed by applying a paint or the like on a substrate, and the self-supporting film means a film that does not require the support of a substrate.

[0068] There is no particular limitation on the thickness of the film, but it can be selected from the range of about 0.01 μm to 10 mm. For example, the thickness of the coating film is 0.05 μm or more and 20 μm or less, preferably 0.1 μm or more and 10 μm or less. Also, the thickness of the self-supporting film is 5 μm or more and 10 mm or less, preferably 50 μm or more and 1 mm or less.

[0069] The method of applying the pigment composition of the present invention to a substrate includes brush coating, roller coating, spatula coating, aerosol, air spray coating, airless spray coating, dip coating, electrocoating, electrostatic coating, powder coating, flow coating method, curtain coating method, shower coating method, spray coating method, roll coating method, bar coating method, gravure coating method, slit coater method, dipping method, spin coating method, casting method, screen printing method, inkjet method, etc. The number of times of applying the pigment composition may be once or may be applied two or more times. When applying, the pigment composition and / or the substrate may be applied while heating, or may be heated after application. After drying, the substrate coated with the pigment composition can also be subjected to heat treatment (post-bake). When a photocurable resin is used, a light source with an appropriate wavelength may be irradiated at a predetermined intensity for a predetermined time.

[0070] As the substrate, known substrates can be used. Examples of the substrate include metals, ceramics, glass, pottery, porcelain, refractories, concrete, mortar, slate, wood, paper, cotton, hemp, silk, wool, plastics, etc. Preferably, it is a substrate that is transparent in the visible range, such as glass, polyethylene terephthalate resin, acrylic resin, polycarbonate resin, cellulose acetate resin, vinyl chloride resin, polyethylene resin, polyolefin resin, fluororesin, polyimide resin, etc.

[0071] The shape of the substrate is not particularly limited and includes any shape. For example, shapes such as fibers, mesh fabrics, knitted fabrics, woven fabrics, non-woven fabrics, films, sheets, plates, rods, pipes, dishes, bowls, cups, boxes, etc. can be mentioned.

[0072] The molded article of the present invention is not particularly limited as long as it contains at least the pigment composition of the present invention. Here, the molded article means a substance obtained from a process of processing a raw material into a desired shape, surface or design. For example, it may be various molded articles including resins, metals, glasses, etc., and is not limited thereto.

[0073] Examples of the method for molding the pigment composition of the present invention include injection molding, blow molding, extrusion molding, casting molding, hand lay-up molding, press molding, compression molding, vacuum molding, pressure air molding, T-die method, inflation method, calendar molding, droplet molding method, direct dissolution method, marble melt method, overflow method, float method, etc.

[0074] The shape of the molded article is not particularly limited and includes any shape. For example, shapes such as fibers, mesh fabrics, knitted fabrics, woven fabrics, non-woven fabrics, films, sheets, plates, rods, pipes, dishes, bowls, cups, boxes, etc. can be mentioned.

Examples

[0075] Hereinafter, the present invention will be described in more detail based on examples. However, the present invention is not limited by these examples in any way. In addition, in explaining the procedures and the like of the following examples, regardless of the presence or absence of the core-shell pattern in the silica particles and the presence or absence of doping with transition metals, it may be simply described as "silica particles" or "silica sol".

[0076] The measurement procedures and measurement devices for physical properties and the like in the examples and comparative examples are as follows.

[0077] <ph> The pH of the sample was measured at room temperature (20 ± 5°C) using a pH meter (manufactured by Toa DKK Corporation).

[0078] <Silica concentration> The silica concentration of the sample was measured using the gravimetric method. Specifically, from the mass of the calcination residue when a predetermined mass of silica sol to be measured was calcined in an electric furnace at 1000°C, the mass of metal elements of 0.0001 mass% or more (1 mass ppm or more) excluding silica (measured as silicon in analysis and converted to oxide) among the inorganic elements measured by the following metal element analysis was converted to oxide and subtracted from the mass of the silica sol. The silica concentration (%) was calculated as [(silica mass / silica sol mass) × 100].

[0079] <Metal element analysis (inorganic element analysis)> Metal element analysis (including silica) was measured using an inductively coupled plasma optical emission spectrometer (ICP-OES, manufactured by Agilent Technologies, Inc., trade name Agilent 5110). Specifically, the sample was treated with a microwave decomposition device and then appropriately diluted and measured by ICP-OES. The calibration curve was created using calibration solutions prepared in the range of 0 - 1 mass ppm. From the measured amount of metal elements and the above silica mass, the mass ratio of transition metal T to silica (T / silica) was calculated.

[0080] <Number average particle diameter (D1) calculated by image analysis method from electron microscope image> Using a multifunctional electron microscope (manufactured by JEOL Ltd., trade name JEM-F200), an electron microscope image of the particles was obtained. The observation conditions were in TEM mode and an acceleration voltage of 200 kV. Next, using a small general-purpose image processing and analysis system (manufactured by Nireco Corporation, trade name Lucerex AP), the area of the particles was determined by image analysis from the obtained electron microscope image, and the equivalent circle diameter, which is the diameter of a perfect circle equal to the area, was calculated. The number average particle diameter (D1) was taken as the number average value of the equivalent circle diameters of at least 500 or more arbitrary particles. The standard deviation was 1σ, and the number average particle diameter (D1) was determined as the average value ± standard deviation.

[0081] <BET particle diameter (D2) calculated by nitrogen adsorption method> Using a nitrogen adsorption method specific surface area measuring device (manufactured by Yuasa Ionics Co., Ltd., trade name Monosorb MS-22), the specific surface area SSA (m 2 / g) by the nitrogen adsorption method (BET method) was measured. As the sample, after contacting the silica sol to be measured with a hydrogen-type strongly acidic cation exchange resin, it was dried at 300 °C for 1 hour under the atmosphere, and then a powder pulverized in a mortar was used. Next, the BET particle diameter D2 (nm) was calculated from Equation (1) using the value of the specific surface area SSA (m 2 / g) measured by the nitrogen adsorption method (BET method) and the following particle density PD (g / cm 3 ). BET particle diameter D2 (nm) = 6000 / [particle density PD (g / cm 3 ) × specific surface area SSA (m 2 / g)] (1)

[0082] <Number average particle diameter / BET particle diameter (D1 / D2) ratio> The number average particle diameter / BET particle diameter (D1 / D2) ratio was calculated by taking the ratio of the above-mentioned number average particle diameter (D1) and BET particle diameter (D2).

[0083] <Shell thickness> The shell thickness was calculated from the following Equation (2) using the values of the number average particle diameter (D1) of the silica sol containing silica particles doped with a transition metal as the core particles and the number average particle diameter (D1) of the colored silica sol containing core-shell type silica particles. Shell thickness = (number average particle diameter (D1) of core-shell type silica particles - number average particle diameter (D1) of core particles) ÷ 2 (2) Note that the shell thickness may also be calculated using the BET particle diameter (D2) instead of the number average particle diameter (D1).

[0084] <Average particle diameter (D3) by dynamic light scattering method> The average particle diameter (D3) by the dynamic light scattering method was measured using a dynamic light scattering method particle diameter measuring device (manufactured by Spectris Co., Ltd., trade name Zetasizer Nano S).

[0085] <Dispersion> The silica sol to be evaluated was irradiated with a green laser pointer with a wavelength of 532 nm, and it was visually confirmed whether the Tyndall phenomenon occurred to evaluate the dispersion of silica particles. When the Tyndall phenomenon was observed and no sediment was formed, the dispersion was evaluated as ○, and when the Tyndall phenomenon was not observed or sediment was formed, the dispersion was evaluated as ×.

[0086] <Particle density PD> The particle density (g / cm 3 ) was measured using a dry-type automatic densitometer (manufactured by Micromeritics, trade name AccuPyc 1340 TEC). The measurement conditions were the average value of 10 measurements with He gas, an introduction pressure of 134 kPaG. The sample used was the powder obtained by drying the target silica sol at 100 °C in the air and then grinding it in a mortar.

[0087] <Identification of crystal phase> The crystal phase was identified using a desktop X-ray diffractometer (XRD, manufactured by Rigaku Corporation, trade name MiniFlex600). The measurement conditions were CuKα ray (=0.15418 nm), θ-2θ method, and a measurement range of 3° - 80°. The sample used was the powder obtained by drying the target silica sol at 100 °C in the air and then grinding it in a mortar.

[0088] <Visible ultraviolet spectrum analysis> The visible ultraviolet spectrum of the silica sol to be measured was measured using a visible ultraviolet near-infrared spectrophotometer (manufactured by Shimadzu Corporation, trade name UV-3600). Specifically, a quartz cell with a lid and an optical path length of 10 mm was used, and water or propylene glycol monomethyl ether (PGME) was used as the control. The visible ultraviolet transmission spectrum and the visible ultraviolet absorption spectrum were measured in the range of a measurement wavelength of 250 - 800 nm.

[0089] <Light resistance evaluation> The light resistance of the core-shell type transition metal-doped colored silica sol was evaluated using a QUV accelerated weathering tester (manufactured by Q-Lab Corporation, trade name QUV / se). Specifically, the target silica sol as the sample was placed in a quartz cell with a lid and an optical path length of 10 mm, and installed in the QUV accelerated weathering tester. The UV irradiation conditions were set as follows: UVA-340 type lamp, UV irradiation intensity 0.89 W / m 2 , temperature 50 °C, and irradiation time 500 hours (500 h) (equivalent to 3.6 months of sunlight). The mass reduction rate of the sample after 500 h of UV irradiation was less than 1%, and the airtightness of the quartz cell with a lid was not a problem. In addition, UV irradiation of the target silica sol was similarly carried out under the condition that the UV irradiation time was only 100 hours or 250 hours. Regarding the silica sol after UV irradiation for a predetermined time (100 hours, 250 hours, 500 hours), the absorption spectrum was measured by visible ultraviolet spectral analysis, and the absorbance change rate before and after UV irradiation at an arbitrary absorption wavelength was calculated from the following formula (3). Absorbance change rate (%) = [Absorbance after UV irradiation / Absorbance before UV irradiation] × 100 (3) It was judged that the higher the light resistance, the closer the value of the absorbance change rate (%) was to 100%, which means that the absorbance did not change under UV irradiation.

[0090] <Preparation of active silicic acid aqueous solution> To 2196 g of pure water, 304 g of a commercially available sodium silicate aqueous solution of JIS No. 3 (silica concentration 28.8 mass%, Na 2 O concentration 9.5 mass%, silica / Na 2 O molar ratio 3.1) was added and mixed uniformly to prepare 2500 g of a sodium silicate aqueous solution diluted to a silica concentration of 3.5 mass%. This diluted sodium silicate aqueous solution was passed through a column filled with 1 L of a hydrogen-type strongly acidic cation exchange resin (manufactured by Organo Corporation, trade name Amberlite IR-120B) at a rate of 250 mL / min to bring it into contact with the cation exchange resin, and 1684 g of an active silicic acid aqueous solution with a silica concentration of 3.5 mass% and a pH of 2.9 was prepared. The concentrations of V, Cr, Mn, Fe, Co, Ni, and Cu in this active silicic acid aqueous solution were all below the detection lower limit value (less than 0.0001 mass%). The obtained aqueous solution of activated silicic acid was appropriately used in the preparation of the feed liquid and the heel liquid, and also in the coating of the core particles (shell layer) in the production process of each silica sol shown below.

[0091] [Comparative Example 1] <Production of Co-Doped Colored Silica Sol> A silica sol (Co-doped colored silica sol) of silica particles doped with Co, a transition metal (only core particles) without shell coating, was prepared. To 780 g of pure water, 28 g of a commercially available aqueous sodium silicate solution of JIS No. 3 (silica concentration 28.8% by mass, Na 2 O concentration 9.5% by mass, silica / Na 2 O molar ratio 3.1) was added and mixed uniformly to prepare 808 g of a heel liquid with a silica concentration of 1.0% by mass, Na 2 O concentration of 0.33% by mass, silica / Na 2 O molar ratio of 3.1, and pH 11.0. Next, 7.9 g of a 10% by mass CoSO 4 ·7H 2 O aqueous solution prepared by mixing and dissolving CoSO 4 powder in pure water in advance was added to 1684 g of the above-mentioned aqueous solution of activated silicic acid and mixed uniformly to prepare 1692 g of a feed liquid. 808 g of the prepared heel liquid was charged into a 3 L glass reaction vessel equipped with a stirrer and a condenser, and the liquid temperature in the vessel was maintained at 80 °C with an oil bath. Then, 1692 g of the feed liquid was continuously supplied into this vessel at a constant rate over 100 minutes with stirring to perform particle synthesis. After the supply of this feed liquid was completed, the liquid temperature in the vessel was maintained at 80 °C for 1 hour with stirring to obtain 2500 g of a sizing liquid of Co-doped colored silica sol.

[0092] The obtained sizing solution of Co-doped colored silica sol was highly transparent and blue-violet, and no sediment was generated. Furthermore, when irradiated with a green laser pointer with a wavelength of 532 nm, the Tyndall phenomenon was observed and the dispersibility was good. This obtained sizing solution of Co-doped colored silica sol had a pH of 10.5, a silica concentration of 2.7% by mass, an average particle diameter (D3) of 13 nm by the dynamic light scattering method, a Co concentration of 0.012% by mass (120 ppm by mass), and a mass ratio of Co to silica (Co / silica) of 0.0045. When the particles were observed with an electron microscope in TEM mode, they were solid spherical particles. This electron microscope image is shown in Fig. 1. The number average particle diameter (D1) calculated by the image analysis method from this electron microscope image of the particles was 9.5 ± 2.6 nm.

[0093] Next, 2300 g of the obtained sizing solution of Co-doped colored silica sol was concentrated by pressure filtration with compressed air at room temperature under stirring using an ultrafiltration (UF) membrane with a molecular weight cut-off of 200,000, and 220 g of a highly transparent and blue-violet UF concentrate of Co-doped colored silica sol and 2080 g of a colorless and transparent UF filtrate were recovered. The appearance of this UF concentrate of Co-doped colored silica sol is shown in Fig. 2. The obtained UF concentrate of Co-doped colored silica sol had a pH of 9.9, a silica concentration of 28.2% by mass, a Co concentration of 0.13% by mass (1300 ppm by mass), and a mass ratio of Co to silica (Co / silica) of 0.0046. The UF filtrate obtained during UF concentration had a pH of 10.4 and a Co concentration of 0.0003% by mass (3 ppm by mass). Since Co was almost absent on the UF filtrate side and was present on the UF concentrate side, it was confirmed that Co was doped into the silica particles and colored. The obtained UF concentrate of Co-doped colored silica sol was dried at 100 °C in the air to obtain a transparent blue-violet powder of Co-doped colored silica sol. The appearance of this powder of Co-doped colored silica sol is shown in Fig. 3. After that, the powder further pulverized in a mortar was measured for the particle density PD with a dry density meter, and the result was 2.13 g / cm 3 It was thus. Similarly, when this pulverized powder was measured by X-ray diffraction method, the XRD pattern was broad, so the crystallinity of the powder was amorphous. This XRD pattern is shown in Fig. 4.

[0094] Next, the UF concentrate of the Co-doped colored silica sol obtained was contacted with a hydrogen-type strongly acidic cation exchange resin to obtain an acidic Co-doped colored silica sol having a pH of 2.4 and a silica concentration of 22.1% by mass. This acidic Co-doped colored silica sol was dried at 300 °C for 1 hour under the atmosphere to obtain a transparent blue-violet powder of the acidic Co-doped colored silica sol. Furthermore, the powder pulverized in a mortar was measured by the nitrogen adsorption method. As a result, the specific surface area SSA was 372 m 2 / g. The BET particle diameter (D2) calculated from the nitrogen adsorption method using Equation (1) was 7.6 nm, and the ratio of the number average particle diameter to the BET particle diameter (D1 / D2) was 1.26.

[0095] After filtering the UF concentrate of the obtained Co-doped colored silica sol with a nylon membrane filter having a pore diameter of 0.45 μm, the visible ultraviolet spectrum of the UF concentrate of the Co-doped colored silica sol was measured using pure water as a control. As a result, Co-derived absorption was confirmed at wavelengths of 540 nm, 590 nm, and 640 nm. This visible ultraviolet transmission spectrum and visible ultraviolet absorption spectrum are shown in FIG. 5.

[0096] <Lightfastness evaluation> The obtained Co-doped colored silica sol was placed in a quartz cell with a lid having an optical path length of 10 mm and installed in a QUV accelerated weathering tester to evaluate the lightfastness. When the state before UV irradiation was set to 100%, the absorbance change rates after 100 h, 250 h, and 500 h of UV irradiation at an absorption wavelength of 640 nm were 96%, 88%, and 83%, respectively. The results are shown in Table 2 and FIG. 6.

[0097] [Example 1] <Production of core-shell type Co-doped colored silica sol> As shown below, silica particles doped with Co were prepared under the same conditions as in Comparative Example 1, and these were used as the core particles of the core-shell type silica particles. To 284 g of pure water, a commercially available aqueous sodium silicate solution of JIS No. 3 (silica concentration: 28.8% by mass, Na 2 O concentration: 9.5% by mass, silica / Na 2 Add 10 g of O molar ratio 3.1) and mix uniformly to obtain a heel solution of 294 g with a silica concentration of 1.0 mass%, a Na 2 O concentration of 0.32 mass%, a silica / Na 2 O molar ratio of 3.1, and a pH of 11.0. Next, 2.9 g of a 10 mass% CoSO 4 ·7H 2 O powder was mixed and dissolved in pure water in advance, and added to 613 g of the above-mentioned active silicic acid aqueous solution and mixed uniformly to prepare 616 g of a feed solution. 4 2.9 g of an aqueous solution was added to 613 g of the active silicic acid aqueous solution and mixed uniformly to prepare 616 g of a feed solution. Charge 294 g of the prepared heel solution into a 3 L glass reaction vessel equipped with a stirrer and a condenser, and keep the liquid temperature in the vessel at 80 °C with an oil bath. Then, 616 g of the feed solution was continuously supplied into this vessel under stirring at a constant rate over 100 minutes to synthesize core particles. Thereafter, 1593 g of the active silicic acid aqueous solution was continuously supplied at a constant rate over 260 minutes to coat the core particles with a shell layer. After the supply of this active silicic acid aqueous solution was completed, the liquid temperature in the vessel was maintained at 80 °C for 6 hours under stirring to obtain 2503 g of a sizing solution of core-shell type Co-doped colored silica sol.

[0098] The obtained sizing solution of core-shell type Co-doped colored silica sol was highly transparent and bluish-violet, and no sediment was generated. Further, when irradiated with a green laser pointer having a wavelength of 532 nm, the Tyndall phenomenon was observed and the dispersibility was good. The obtained sizing solution of core-shell type Co-doped colored silica sol had a pH of 9.7, a silica concentration of 3.1 mass%, an average particle diameter (D3) of 14 nm by the dynamic light scattering method, a Co concentration of 0.0043 mass% (43 mass ppm), and a mass ratio of Co to silica (Co / silica) of 0.0014. When the particles were observed with an electron microscope in TEM mode, they were solid spherical particles. The electron micrograph of this particle is shown in Fig. 1. The number average particle diameter (D1) calculated by the image analysis method from the electron micrograph of this particle was 12.9 ± 3.8 nm.

[0099] When the shell thickness was calculated from Equation (3) using the value of the number average particle diameter (D1) of 9.5 ± 2.6 nm of the core particles in Comparative Example 1, the shell thickness was 1.7 nm.

[0100] Next, 2300 g of the sizing solution of the obtained core-shell type Co-doped colored silica sol was concentrated by pressure filtration with compressed air at room temperature with stirring using an ultrafiltration (UF) membrane having a molecular weight cut-off of 200,000, and 217 g of a UF concentrate of a core-shell type Co-doped colored silica sol that was highly transparent and bluish-purple and 2082 g of a colorless and transparent UF filtrate were recovered. The appearance of the UF concentrate of this core-shell type Co-doped colored silica sol is shown in Fig. 2. The obtained UF concentrate of the core-shell type Co-doped colored silica sol had a pH of 8.9, a silica concentration of 32.8% by mass, a Co concentration of 0.046% by mass (460 ppm by mass), and a mass ratio of Co to silica (Co / silica) of 0.0014. The UF filtrate obtained during UF concentration had a pH of 9.7 and a Co concentration of 0.0001% by mass (1 ppm by mass). Since Co was almost absent on the UF filtrate side and was present on the UF concentrate side, it was confirmed that Co was doped and colored in the silica particles. The obtained UF concentrate of the core-shell type Co-doped colored silica sol was dried at 100 °C in the atmosphere to obtain a powder of a transparent bluish-purple core-shell type Co-doped colored silica sol. The appearance of the powder of this core-shell type Co-doped colored silica sol is shown in Fig. 3. Thereafter, the particle density PD of the powder further pulverized in a mortar was measured with a dry densitometer, and as a result, it was 2.21 g / cm 3 It was. Similarly, as a result of measuring this pulverized powder by X-ray diffraction method, since the XRD pattern was broad, the crystallinity of the powder was amorphous. This XRD pattern is shown in Fig. 4.

[0101] Next, the obtained UF concentrate of the core-shell type Co-doped colored silica sol was brought into contact with a hydrogen-type strongly acidic cation exchange resin to obtain an acidic core-shell type Co-doped colored silica sol having a pH of 2.2 and a silica concentration of 26.2% by mass. This acidic core-shell type Co-doped colored silica sol was dried at 300 °C for 1 hour in the atmosphere to obtain a powder of a transparent bluish-purple acidic core-shell type Co-doped colored silica sol. Furthermore, the powder further pulverized in a mortar was measured by the nitrogen adsorption method. As a result, the specific surface area SSA was 255 m 2 / g. The BET particle size (D2) calculated from the nitrogen adsorption method using Equation (1) was 10.6 nm, and the ratio of the number average particle size to the BET particle size (D1 / D2) was 1.21.

[0102] The UF concentrate of the obtained core-shell type Co-doped colored silica sol was filtered through a nylon membrane filter with a pore size of 0.45 μm, and then the visible ultraviolet spectrum of the UF concentrate of the core-shell type Co-doped colored silica sol was measured using pure water as a control. As a result, Co-derived absorption was confirmed at wavelengths of 540 nm, 590 nm, and 640 nm. This visible ultraviolet transmission spectrum and visible ultraviolet absorption spectrum are shown in FIG. 5.

[0103] [Lightfastness Evaluation] The obtained core-shell type Co-doped colored silica sol was placed in a quartz cell with a lid having an optical path length of 10 mm and installed in a QUV accelerated weathering tester to evaluate the lightfastness. When the state before UV irradiation was set as 100%, the absorbance change rates after 100 h, 250 h, and 500 h of UV irradiation at an absorption wavelength of 640 nm were 100%, 100%, and 100%, respectively. By coating the core particles with a silica shell layer, the lightfastness was improved. The results are shown in Table 2 and FIG. 6.

[0104] [Example 2] [Production of Core-Shell Type Co-Doped Colored Silica Sol] After synthesizing the core particles in Example 1, when continuously supplying the active silicic acid aqueous solution at a constant rate to coat the core particles, the liquid temperature in the container was changed from 80 °C to 100 °C, and further after the supply of the active silicic acid aqueous solution was completed, the liquid temperature in the container was also changed from 80 °C to 100 °C. Otherwise, the operation was the same as in Example 1, and 2503 g of the sizing liquid of the core-shell type Co-doped colored silica sol was obtained.

[0105] The sizing solution of the obtained core-shell type Co-doped colored silica sol was highly transparent and bluish purple, and no sediment was generated. Furthermore, when irradiated with a green laser pointer with a wavelength of 532 nm, the Tyndall phenomenon was observed and the dispersibility was good. The sizing solution of the obtained core-shell type Co-doped colored silica sol had a pH of 9.7, a silica concentration of 3.3 mass%, an average particle diameter (D3) of 12 nm by the dynamic light scattering method, a Co concentration of 0.0044 mass% (44 mass ppm), and a mass ratio of Co to silica (Co / silica) of 0.0013. When the particles were observed with an electron microscope in TEM mode, they were solid spherical particles. The number average particle diameter (D1) calculated by the image analysis method from the electron microscope image of these particles was 12.7 ± 2.9 nm.

[0106] When the shell thickness was calculated from Equation (3) using the value of the number average particle diameter (D1) of 9.5 ± 2.6 nm of the core particles in Comparative Example 1, the shell thickness was 1.6 nm.

[0107] Next, 2300 g of the sizing solution of the obtained core-shell type Co-doped colored silica sol was concentrated by pressure filtration with compressed air at room temperature under stirring using an ultrafiltration (UF) membrane with a molecular weight cut-off of 200,000, and 258 g of a highly transparent and bluish purple UF concentrate of the core-shell type Co-doped colored silica sol and 2042 g of a colorless and transparent UF filtrate were recovered. The UF concentrate of the obtained core-shell type Co-doped colored silica sol had a pH of 8.9, a silica concentration of 29.4 mass%, a Co concentration of 0.038 mass% (380 mass ppm), and a mass ratio of Co to silica (Co / silica) of 0.0013. The UF filtrate obtained during UF concentration had a pH of 9.5 and a Co concentration of 0.0001 mass% (1 mass ppm). Since Co was almost absent on the UF filtrate side and was present on the UF concentrate side, it was confirmed that Co was doped and colored on the silica particles. The UF concentrate of the obtained core-shell type Co-doped colored silica sol was dried at 100 °C in the atmosphere to obtain a transparent bluish purple powder of the core-shell type Co-doped colored silica sol. After that, the particle density PD of the powder further pulverized in a mortar was measured with a dry density meter, and the result was 2.22 g / cm 3 It was the same. As a result of measuring the pulverized powder by X-ray diffraction method, since the XRD pattern was broad, the crystallinity of the powder was amorphous.

[0108] Next, the UF concentrate of the obtained core-shell type Co-doped colored silica sol was brought into contact with a hydrogen-type strongly acidic cation exchange resin to obtain an acidic core-shell type Co-doped colored silica sol having a pH of 2.1 and a silica concentration of 27.9% by mass. This acidic core-shell type Co-doped colored silica sol was dried at 300 ° C for 1 hour in the atmosphere to obtain a transparent blue-violet powder of the acidic core-shell type Co-doped colored silica sol. Furthermore, as a result of measuring the powder pulverized in a mortar by the nitrogen adsorption method, the specific surface area SSA was 252 m 2 / g It was. The BET particle diameter (D2) calculated from the nitrogen adsorption method using formula (1) was 10.7 nm, and the ratio of the number average particle diameter / BET particle diameter (D1 / D2) was 1.19.

[0109] After filtering the UF concentrate of the obtained core-shell type Co-doped colored silica sol with a nylon membrane filter having a pore diameter of 0.45 μm, the visible ultraviolet spectrum of the UF concentrate of the core-shell type Co-doped colored silica sol was measured using pure water as a control. As a result, Co-derived absorption was confirmed at wavelengths of 540 nm, 590 nm, and 640 nm.

[0110] <Light resistance evaluation> The obtained core-shell type Co-doped colored silica sol was placed in a quartz cell with a lid having an optical path length of 10 mm and installed in a QUV accelerated weathering tester to evaluate the light resistance. When the state before UV irradiation was set to 100%, the absorbance change rates after 100 h, 250 h, and 500 h of UV irradiation at an absorption wavelength of 640 nm were 100%, 100%, and 100%, respectively. By coating the core particles with a silica shell layer, the light resistance was improved. The results are shown in Table 2 and FIG. 6.

[0111] [Example 3] <Production of core-shell type Co-doped colored silica sol> As the silica sol containing core particles, the sizing solution of the Co-doped colored silica sol prepared in Comparative Example 1 was used for shell coating. Into a 3 L glass reaction vessel equipped with a stirrer and a condenser, 343 g of the sizing solution of the Co-doped colored silica sol prepared in Comparative Example 1 and 9.2 g of a 10 mass% aqueous NaOH solution were charged, and the liquid temperature in the vessel was maintained at 80 °C with an oil bath. Next, 2029 g of the active silicic acid aqueous solution was continuously supplied at a constant rate over 900 minutes to the vessel under stirring to coat the core particles with a shell layer. After the supply of this active silicic acid aqueous solution was completed, the liquid temperature in the vessel was maintained at 80 °C for 6 hours under stirring to obtain 2381 g of a sizing solution of a core-shell type Co-doped colored silica sol.

[0112] The obtained sizing solution of the core-shell type Co-doped colored silica sol was highly transparent and blue-violet, and no sediment was generated. Further, when irradiated with a green laser pointer having a wavelength of 532 nm, the Tyndall phenomenon was observed and the dispersibility was good. The obtained sizing solution of the core-shell type Co-doped colored silica sol had a pH of 10.0, a silica concentration of 3.4 mass%, an average particle diameter (D3) of 17 nm by the dynamic light scattering method, a Co concentration of 0.0017 mass% (17 mass ppm), and a mass ratio of Co to silica (Co / silica) of 0.0005. When the particles were observed with an electron microscope in TEM mode, they were solid spherical particles. The number average particle diameter (D1) calculated by the image analysis method from the electron micrograph of these particles was 16.8 ± 3.7 nm.

[0113] When the shell thickness was calculated from Equation (3) using the value of the number average particle diameter (D1) of 9.5 ± 2.6 nm of the core particles in Comparative Example 1, the shell thickness was 3.7 nm.

[0114] Next, 2300 g of the obtained sizing solution of the core-shell type Co-doped colored silica sol was concentrated by pressure filtration with compressed air at room temperature under stirring using an ultrafiltration (UF) membrane with a molecular weight cut-off of 200,000 to recover 238 g of a UF concentrate of a core-shell type Co-doped colored silica sol that was highly transparent and blue-violet and 2062 g of a colorless and transparent UF filtrate. The UF concentrate of the obtained core-shell type Co-doped colored silica sol had a pH of 9.4, a silica concentration of 32.8% by mass, a Co concentration of 0.016% by mass (160 ppm by mass), and a mass ratio of Co to silica (Co / silica) of 0.0005. The UF filtrate obtained during UF concentration had a pH of 9.8 and a Co concentration of 0.0001% by mass (1 ppm by mass). Since Co was almost absent on the UF filtrate side and was present on the UF concentrate side, it was confirmed that Co was doped and colored on the silica particles. The UF concentrate of the obtained core-shell type Co-doped colored silica sol was dried at 100 °C in air to obtain a powder of the core-shell type Co-doped colored silica sol in a transparent blue-violet color. After that, the powder further pulverized in a mortar was measured for particle density PD with a dry densitometer, and as a result, it was 2.23 g / cm 3 . Similarly, when this pulverized powder was measured by X-ray diffraction method, since the XRD pattern was broad, the crystallinity of the powder was amorphous.

[0115] Next, the UF concentrate of the obtained core-shell type Co-doped colored silica sol was brought into contact with a hydrogen-type strongly acidic cation exchange resin to obtain an acidic core-shell type Co-doped colored silica sol having a pH of 2.2 and a silica concentration of 25.4% by mass. This acidic core-shell type Co-doped colored silica sol was dried at 300 °C for 1 hour in air to obtain a powder of the acidic core-shell type Co-doped colored silica sol in a transparent blue-violet color. Furthermore, the powder further pulverized in a mortar was measured by the nitrogen adsorption method, and as a result, the specific surface area SSA was 186 m 2 / g. The BET particle diameter (D2) calculated from the nitrogen adsorption method using formula (1) was 14.5 nm, and the ratio of the number average particle diameter to the BET particle diameter (D1 / D2) was 1.16.

[0116] After filtering the UF concentrate of the obtained core-shell type Co-doped colored silica sol with a nylon membrane filter having a pore size of 0.45 μm, the visible ultraviolet spectrum of the UF concentrate of the core-shell type Co-doped colored silica sol was measured using pure water as a control. As a result, absorption derived from Co was confirmed at wavelengths of 540 nm, 590 nm, and 640 nm.

[0117] <Light resistance evaluation> The obtained core-shell type Co-doped colored silica sol was placed in a quartz cell with a lid and an optical path length of 10 mm, and installed in a QUV accelerated weathering tester to evaluate the light resistance. When the state before UV irradiation was set to 100%, the absorbance change rates after 100 h, 250 h, and 500 h of UV irradiation at an absorption wavelength of 640 nm were 100%, 100%, and 100%, respectively. By coating the core particles with a silica shell layer, the light resistance was improved. The results are shown in Table 2 and Fig. 6.

[0118] [Example 4] <Production of core-shell type Co-doped colored silica sol> When continuously supplying the active silicic acid aqueous solution at a constant rate to coat the core particles in Example 3, the liquid temperature in the container was changed from 80 °C to 100 °C, and further, after the supply of the active silicic acid aqueous solution was completed, the liquid temperature in the container was also changed from 80 °C to 100 °C. Otherwise, the operation was the same as in Example 3, and 2381 g of a sizing liquid of the core-shell type Co-doped colored silica sol was obtained.

[0119] The obtained sizing liquid of the core-shell type Co-doped colored silica sol was highly transparent and bluish-purple, and no sediment was generated. Further, when irradiated with a green laser pointer having a wavelength of 532 nm, the Tyndall phenomenon was observed, and the dispersibility was good. The obtained sizing liquid of the core-shell type Co-doped colored silica sol had a pH of 10.1, a silica concentration of 3.6% by mass, an average particle diameter (D3) of 25 nm by the dynamic light scattering method, a Co concentration of 0.0017% by mass (17 ppm by mass), and a mass ratio of Co to silica (Co / silica) of 0.0005. When the particles were observed with an electron microscope in TEM mode, they were solid spherical particles. The number average particle diameter (D1) calculated by the image analysis method from the electron microscope image of these particles was 17.3 ± 4.1 nm.

[0120] When the shell thickness was calculated from Equation (3) using the value of the number average particle diameter (D1) of 9.5 ± 2.6 nm of the core particles in Comparative Example 1, the shell thickness was 3.9 nm.

[0121] Next, 2300 g of the sizing solution of the core-shell type Co-doped colored silica sol obtained was concentrated by pressure filtration with compressed air at room temperature with stirring using an ultrafiltration (UF) membrane with a molecular weight cut-off of 200,000, and 268 g of a UF concentrate of the core-shell type Co-doped colored silica sol that was highly transparent and blue-violet and 2032 g of a colorless and transparent UF filtrate were recovered. The UF concentrate of the obtained core-shell type Co-doped colored silica sol had a pH of 9.6, a silica concentration of 30.9% by mass, a Co concentration of 0.014% by mass (140 ppm by mass), and a mass ratio of Co to silica (Co / silica) of 0.0005. The UF filtrate obtained during UF concentration had a pH of 10.0 and a Co concentration below the detection lower limit (less than 0.0001% by mass). Since Co was almost absent on the UF filtrate side and was present on the UF concentrate side, it was confirmed that Co was doped and colored on the silica particles. The UF concentrate of the obtained core-shell type Co-doped colored silica sol was dried at 100 °C in the air to obtain a powder of the core-shell type Co-doped colored silica sol that was transparent and blue-violet. After that, the powder further pulverized in a mortar was measured for particle density PD with a dry density meter, and as a result, it was 2.24 g / cm Similarly, when the pulverized powder was measured by X-ray diffraction method, since the XRD pattern was broad, the crystallinity of the powder was amorphous. 3 Next, the UF concentrate of the obtained core-shell type Co-doped colored silica sol was brought into contact with a hydrogen-type strongly acidic cation exchange resin to obtain an acidic core-shell type Co-doped colored silica sol with a pH of 2.1 and a silica concentration of 24.2% by mass. This acidic core-shell type Co-doped colored silica sol was dried at 300 °C in the air for 1 hour to obtain a powder of the acidic core-shell type Co-doped colored silica sol that was transparent and blue-violet.

[0122] Furthermore, when the powder further pulverized in a mortar was measured by the nitrogen adsorption method, the specific surface area SSA was 174 m / g. The BET particle diameter (D2) calculated from the nitrogen adsorption method using Equation (1) was 15.4 nm, and the ratio of the number average particle diameter to the BET particle diameter (D1 / D2) was 1.13. 2

[0123] ​The UF concentrate of the obtained core-shell type Co-doped colored silica sol was filtered through a nylon membrane filter with a pore size of 0.45 μm, and then the visible ultraviolet spectrum of the UF concentrate of the core-shell type Co-doped colored silica sol was measured using pure water as a control. As a result, Co-derived absorption was confirmed at wavelengths of 540 nm, 590 nm, and 640 nm.

[0124] <Lightfastness evaluation> The obtained core-shell type Co-doped colored silica sol was placed in a quartz cell with a lid and an optical path length of 10 mm, and installed in a QUV accelerated weathering tester to evaluate its lightfastness. When the absorbance before UV irradiation was set to 100%, the absorbance change rates after 100 h, 250 h, and 500 h of UV irradiation at an absorption wavelength of 640 nm were 100%, 100%, and 100%, respectively. By coating the core particles with a silica shell layer, the lightfastness was improved. The results are shown in Table 2 and Figure 6.

[0125] [Comparative Example 2] <Production of Co-doped colored silica sol> (Without shell coating) A silica sol (Co-doped colored silica sol) of silica particles doped with Co, a transition metal, (only core particles) was prepared. 745 g of pure water, 317 g of the above-mentioned active silicic acid aqueous solution (silica concentration 3.5% by mass, pH 2.9), and 46 g of aqueous ammonia (ammonia concentration 27% by mass) were added and uniformly mixed to prepare a heel solution (silica concentration 1.0% by mass, NH 3 concentration 1.1% by mass, silica / NH 3 molar ratio 0.26, pH 10.8) of 1108 g. Next, 29.0 g of a 10% by mass CoSO 4 ·7H 2 O powder was mixed and dissolved in pure water in advance to prepare a 10% by mass CoSO 4 aqueous solution, and 1384 g of the above-mentioned active silicic acid aqueous solution were uniformly mixed to prepare a feed solution of 1413 g. A 3 L glass reaction vessel equipped with a stirrer and a condenser was charged with 1108 g of the prepared heel liquid, and the liquid temperature in the vessel was maintained at 80 °C using an oil bath. Next, 1413 g of the feed liquid was continuously supplied at a constant rate over 60 minutes into this vessel under stirring to perform particle synthesis. After the completion of this feed liquid supply, the liquid temperature in the vessel was maintained at 80 °C for 6 hours under stirring to obtain 2521 g of a sizing liquid for Co-doped colored silica sol.

[0126] The obtained sizing liquid of Co-doped colored silica sol was highly transparent and blue-violet, and no sediment was generated. Furthermore, when irradiated with a green laser pointer with a wavelength of 532 nm, the Tyndall phenomenon was observed and the dispersibility was good. The obtained sizing liquid of Co-doped colored silica sol had a pH of 10.4, a silica concentration of 2.4 mass%, an average particle diameter (D3) of 27 nm by the dynamic light scattering method, a Co concentration of 0.045 mass% (450 mass ppm), and a mass ratio of Co to silica (Co / silica) of 0.019. When the particles were observed with an electron microscope in TEM mode, they were solid spherical particles. The number average particle diameter (D1) calculated by the image analysis method from the electron microscope image of these particles was 10.5 ± 3.3 nm.

[0127] Next, 2360 g of the obtained sizing liquid of Co-doped colored silica sol was concentrated by pressure filtration with compressed air at room temperature under stirring using an ultrafiltration (UF) membrane with a molecular weight cut-off of 200,000 to recover 193 g of a UF concentrate of Co-doped colored silica sol that was highly transparent and blue-violet and 2167 g of a colorless and transparent UF filtrate. The obtained UF concentrate of Co-doped colored silica sol had a pH of 9.7, a silica concentration of 29.4 mass%, a Co concentration of 0.57 mass% (5700 mass ppm), and a mass ratio of Co to silica (Co / silica) of 0.019. The UF filtrate obtained during UF concentration had a pH of 10.4 and a Co concentration below the detection limit (less than 0.0001 mass%). Since Co was almost absent on the UF filtrate side and was present on the UF concentrate side, it was confirmed that Co was doped and colored on the silica particles. The UF concentrate of the obtained Co-doped colored silica sol was dried at 100 °C under the atmosphere to obtain a transparent blue-violet powder of Co-doped colored silica sol. Then, the powder further pulverized in a mortar was measured for particle density PD with a dry densitometer, and as a result, it was 2.21 g / cm 3 It was. Similarly, as a result of measuring this pulverized powder by X-ray diffraction method, since the XRD pattern was broad, the crystallinity of the powder was amorphous.

[0128] Next, the UF concentrate of the obtained Co-doped colored silica sol was brought into contact with a hydrogen-type strongly acidic cation exchange resin to obtain an acidic Co-doped colored silica sol having a pH of 2.0 and a silica concentration of 20.5% by mass. This acidic Co-doped colored silica sol was dried at 300 °C for 1 hour under the atmosphere to obtain a transparent blue-violet powder of acidic Co-doped colored silica sol. Furthermore, as a result of measuring the powder further pulverized in a mortar by the nitrogen adsorption method, the specific surface area SSA was 296 m 2 / g. The BET particle size (D2) calculated from the nitrogen adsorption method using Equation (1) was 9.2 nm, and the ratio of the number average particle size to the BET particle size (D1 / D2) was 1.14.

[0129] After filtering the sizing solution of the obtained Co-doped colored silica sol with a nylon membrane filter having a pore size of 0.45 μm, the visible ultraviolet spectrum of the sizing solution of the Co-doped colored silica sol was measured using pure water as a control. As a result, Co-derived absorption was confirmed at wavelengths of 525 nm, 580 nm, and 640 nm.

[0130] <Lightfastness Evaluation> The obtained Co-doped colored silica sol was placed in a quartz cell with a lid having an optical path length of 10 mm and installed in a QUV accelerated weathering tester to evaluate the lightfastness. When the state before UV irradiation was set as 100%, the absorbance change rates after 100 h, 250 h, and 500 h of UV irradiation at an absorption wavelength of 640 nm were 89%, 80%, and 74%, respectively. The results are shown in Table 2 and Figure 6.

[0131] [Example 5] <Production of Core-Shell Type Co-Doped Colored Silica Sol> Silica particles doped with Co were prepared under the same conditions as in Comparative Example 2 as shown below, and these were used as the core particles of the core-shell type silica particles. 315 g of pure water, 134 g of the above-mentioned active silicic acid aqueous solution (silica concentration 3.5% by mass, pH 2.9), and 19 g of aqueous ammonia (ammonia concentration 27% by mass) were added and uniformly mixed to prepare a heel liquid (silica concentration 1.0% by mass, NH 3 concentration 1.1% by mass, silica / NH 3 molar ratio 0.25, pH 10.8) of 468 g. Next, 12.3 g of a 10% by mass CoSO 4 ·7H 2 O powder was mixed and dissolved in pure water in advance to prepare 12.3 g of a 10% by mass CoSO 4 aqueous solution, and 585 g of the above-mentioned active silicic acid aqueous solution were uniformly mixed to prepare 597 g of a feed liquid. 468 g of the prepared heel liquid was charged into a 3 L glass reaction vessel equipped with a stirrer and a condenser, and the liquid temperature in the vessel was maintained at 80 °C with an oil bath. Next, 597 g of the feed liquid was continuously supplied into this vessel under stirring at a constant rate over 60 minutes to synthesize core particles. Then, 1454 g of the above-mentioned active silicic acid aqueous solution was continuously supplied at a constant rate over 144 minutes to coat the core particles with a shell layer. After the supply of this active silicic acid aqueous solution was completed, the liquid temperature in the vessel was maintained at 80 °C for 6 hours under stirring to obtain 2519 g of a sizing liquid of the core-shell type Co-doped colored silica sol.

[0132] The sizing solution of the obtained core-shell type Co-doped colored silica sol was highly transparent and bluish-purple, and no sediment was generated. Furthermore, when irradiated with a green laser pointer with a wavelength of 532 nm, the Tyndall phenomenon was observed, and the dispersibility was good. The sizing solution of the obtained core-shell type Co-doped colored silica sol had a pH of 10.1, a silica concentration of 3.0 mass%, an average particle diameter (D3) of 24 nm by the dynamic light scattering method, a Co concentration of 0.019 mass% (190 mass ppm), and a mass ratio of Co to silica (Co / silica) of 0.0063. When the particles were observed with an electron microscope in TEM mode, they were solid spherical particles. The number average particle diameter (D1) calculated by the image analysis method from the electron microscope image of these particles was 11.1 ± 3.8 nm.

[0133] When the shell thickness was calculated from Equation (3) using the value of the number average particle diameter (D1) of 10.5 ± 3.3 nm of the core particles in Comparative Example 2, the shell thickness was 0.3 nm.

[0134] Next, 2340 g of the sizing solution of the obtained core-shell type Co-doped colored silica sol was concentrated by pressure filtration with compressed air at room temperature with stirring using an ultrafiltration (UF) membrane with a molecular weight cut-off of 200,000, and 232 g of a UF concentrate of the core-shell type Co-doped colored silica sol that was highly transparent and bluish-purple and 2108 g of a colorless and transparent UF filtrate were recovered. The UF concentrate of the obtained core-shell type Co-doped colored silica sol had a pH of 9.4, a silica concentration of 30.3 mass%, a Co concentration of 0.19 mass% (1900 mass ppm), and a mass ratio of Co to silica (Co / silica) of 0.0063. The UF filtrate obtained during UF concentration had a pH of 10.2 and a Co concentration below the detection lower limit (less than 0.0001 mass%). Since Co was almost absent on the UF filtrate side and was present on the UF concentrate side, it was confirmed that Co was doped and colored on the silica particles. The UF concentrate of the obtained core-shell type Co-doped colored silica sol was dried at 100 °C in the atmosphere to obtain a transparent bluish-purple powder of the core-shell type Co-doped colored silica sol. After that, the particle density PD of the powder further pulverized in a mortar was measured with a dry density meter, and as a result, 2.20 g / cm 3 It was the case. Similarly, as a result of measuring this pulverized powder by X-ray diffraction method, since the XRD pattern was broad, the crystallinity of the powder was amorphous.

[0135] Next, the UF concentrate of the obtained core-shell type Co-doped colored silica sol was brought into contact with a hydrogen-type strongly acidic cation exchange resin to obtain an acidic core-shell type Co-doped colored silica sol having a pH of 2.2 and a silica concentration of 21.5 mass%. This acidic core-shell type Co-doped colored silica sol was dried at 300 °C for 1 hour in the atmosphere to obtain a powder of a transparent blue-violet acidic core-shell type Co-doped colored silica sol. Furthermore, as a result of measuring the powder pulverized in a mortar by the nitrogen adsorption method, the specific surface area SSA was 275 m 2 / g. The BET particle diameter (D2) calculated from the nitrogen adsorption method using Equation (1) was 9.9 nm, and the ratio of the number average particle diameter to the BET particle diameter (D1 / D2) was 1.12.

[0136] After filtering the sizing solution of the obtained core-shell type Co-doped colored silica sol with a nylon membrane filter having a pore size of 0.45 μm, pure water was used as a control to measure the visible ultraviolet spectrum of the sizing solution of the core-shell type Co-doped colored silica sol. As a result, Co-derived absorption was confirmed at wavelengths of 525 nm, 580 nm, and 640 nm.

[0137] <Lightfastness evaluation> The obtained core-shell type Co-doped colored silica sol was placed in a quartz cell with a lid having an optical path length of 10 mm and installed in a QUV accelerated weathering tester to evaluate the lightfastness. When the state before UV irradiation was set as 100%, the absorbance change rates after 100 h, 250 h, and 500 h of UV irradiation at an absorption wavelength of 640 nm were 95%, 92%, and 90%, respectively. The lightfastness was improved by coating the shell layer of silica. The results are shown in Table 2 and FIG. 6.

[0138] As shown in Table 2 and Figure 6, for the Co-doped silica sols of Comparative Example 1 and Comparative Example 2 (only core particles, without shell coating), the absorbance change rate decreased by about 20% to 74 - 83% after 500 h of UV irradiation. In contrast, for the core-shell type Co-doped silica sols of Examples 1 - 5, the absorbance change rate was 90 - 100% even after 500 h of UV irradiation, and the absorbance hardly decreased or, if it did decrease, it only decreased by about 10%. From these results, it became clear that the core-shell type transition metal-doped silica sol of the present invention suppresses the change (decrease) in absorbance even after long-term UV irradiation and has excellent light resistance.

[0139] [Comparative Example 3] A red organic pigment dispersion (manufactured by Tokushiki Co., Ltd., trade name MT-120 Red, pigment pigment violet 19, pigment concentration 15% by mass) was diluted with propylene glycol monomethyl ether (PGME) to a pigment concentration of 0.01% by mass to prepare a PGME-diluted red organic pigment dispersion. Note that the red organic pigment dispersion diluted with pure water was not suitable for light resistance evaluation because the particles aggregated and precipitates were generated. Using PGME as a control, the visible ultraviolet spectrum of this PGME-diluted red organic pigment dispersion was measured. As a result, absorption was confirmed at wavelengths of 490 nm, 525 nm, and 560 nm. <Light Resistance Evaluation> This PGME-diluted red organic pigment dispersion was placed in a quartz cell with a lid having an optical path length of 10 mm and installed in a QUV accelerated weathering tester to evaluate its light resistance. When the absorbance before UV irradiation was set to 100%, the absorbance change rates after 100 h, 250 h, and 500 h of UV irradiation at an absorption wavelength of 560 nm were 35%, 0.3%, and 0.2%, respectively. The results are shown in Table 3 and Figure 7.

[0140] [Comparative Example 4] A yellow organic pigment dispersion ((manufactured by Tokushiki Co., Ltd., trade name MT-150 Yellow, pigment Pigment Yellow 110, pigment concentration 15% by mass)) was diluted with propylene glycol monomethyl ether (PGME) to a pigment concentration of 0.01% by mass to prepare a PGME-diluted yellow organic pigment dispersion. Note that the yellow organic pigment dispersion diluted with pure water was not suitable for light resistance evaluation because the particles aggregated and precipitates occurred. For comparison, the visible ultraviolet spectrum of this PGME-diluted yellow organic pigment dispersion was measured using PGME. As a result, absorption was confirmed at wavelengths of 325 nm and 440 nm. <Light Resistance Evaluation> This PGME-diluted yellow organic pigment dispersion was placed in a quartz cell with a lid and an optical path length of 10 mm and installed in a QUV accelerated weathering tester to evaluate its light resistance. When the state before UV irradiation was set to 100%, the absorbance change rates after 100 h, 250 h, and 500 h of UV irradiation at an absorption wavelength of 440 nm were 35%, 0.4%, and 0.4%, respectively. The results are shown in Table 3 and Figure 7.

[0141] [Comparative Example 5] A green organic pigment dispersion ((manufactured by Tokushiki Co., Ltd., trade name MT-160 Green, pigment Pigment Green 7, pigment concentration 25% by mass)) was diluted with propylene glycol monomethyl ether (PGME) to a pigment concentration of 0.01% by mass to prepare a PGME-diluted green organic pigment dispersion. Note that the green organic pigment dispersion diluted with pure water was not suitable for light resistance evaluation because the particles aggregated and precipitates occurred. For comparison, the visible ultraviolet spectrum of this PGME-diluted green organic pigment dispersion was measured using PGME. As a result, absorption was confirmed at wavelengths of 320 nm, 365 nm, and 650 nm. <Light Resistance Evaluation> This PGME-diluted green organic pigment dispersion was placed in a quartz cell with a lid and an optical path length of 10 mm and installed in a QUV accelerated weathering tester to evaluate its light resistance. When the state before UV irradiation was set to 100%, the absorbance change rates after 100 h, 250 h, and 500 h of UV irradiation at an absorption wavelength of 650 nm were 74%, 33%, and 5%, respectively. The results are shown in Table 3 and Figure 7. The results are shown in Table 3 and Figure 7.

[0142] [Comparative Example 6] A cyan-based organic pigment dispersion (manufactured by Tokushiki Co., Ltd., trade name MT-170 Blue, pigment Pigment Blue 15, pigment concentration 15% by mass) was diluted with propylene glycol monomethyl ether (PGME) to a pigment concentration of 0.01% by mass to prepare a PGME-diluted cyan-based organic pigment dispersion. Note that the cyan-based organic pigment dispersion diluted with pure water was not suitable for light resistance evaluation because the particles aggregated and precipitates were generated. Using PGME as a control, the visible ultraviolet spectrum of this PGME-diluted cyan-based organic pigment dispersion was measured. As a result, absorption was confirmed at wavelengths of 345 nm, 630 nm, and 710 nm. [Light Resistance Evaluation] This PGME-diluted cyan-based organic pigment dispersion was placed in a quartz cell with a lid and an optical path length of 10 mm and installed in a QUV accelerated weathering tester to evaluate its light resistance. When the state before UV irradiation was set to 100%, the absorbance change rates after 100 h, 250 h, and 500 h of UV irradiation at an absorption wavelength of 630 nm were 77%, 31%, and 6%, respectively. The results are shown in Table 3 and Figure 7.

[0143] As shown in Table 3 and Figure 7, for the organic pigments of Comparative Examples 3 - 6, the absorbance change rate became 0.2 - 6% after 500 h of UV irradiation, and almost all absorption disappeared. On the other hand, as shown in Table 2 and Figure 6, for the core-shell type Co-doped silica sols of Examples 1 - 5, the absorbance change rate after 500 h of UV irradiation was 90 - 100%, and the absorbance was maintained at a high level. As described above, it became clear that the core-shell type transition metal-doped silica sol of the present invention has excellent light resistance even against conventional organic pigments.

[0144] [Table 1]

[0145] [Table 2]

[0146]

Table 3

Industrial Applicability

[0147] The pigment composition containing the core-shell type transition metal-doped colored silica sol of the present invention can be used in bicycles, motorcycles, automobiles, railway vehicles, ships, aircraft, rockets, buildings, building materials, roofing materials, exterior wall materials, wall materials, floor materials, ceiling materials, base materials, signboards, bulletin boards, signs, signals, utility poles, electric wires, streetlights, posts, roads, bridges, window glasses, glassware, industrial electrical products, household electrical products, furniture, kitchen appliances, sanitary equipment, cooking utensils, tableware, containers, stationery, clothes, ornaments, etc. In particular, it is preferably used in applications that require transparency and light resistance. Moreover, a colored glass can be produced by applying the pigment composition containing the core-shell type transition metal-doped colored silica sol of the present invention to glass and then heating and cooling it, or adding it to a glass raw material and melting, cooling, and vitrifying it. The pigment composition containing the core-shell type transition metal-doped colored silica sol of the present invention can also be applied to various products for the purpose of coloring.< / ph>

Claims

1. A colored silica sol containing core-shell type silica particles, wherein the core-shell type silica particles are doped with a transition metal, and the colored silica sol satisfies the following conditions (1) to (4): a colored silica sol; (1) The mass ratio of the transition metal T to silica (T / silica) is 0.0001 or more and 0.05 or less, (2) The number average particle diameter (D1) of the core-shell type silica particles in the colored silica sol calculated by an image analysis method from an electron microscope image is 5 nm or more and less than 50 nm, (3) The BET particle diameter (D2) of the core-shell type silica particles in the colored silica sol calculated by the nitrogen adsorption method is 5 nm or more and less than 50 nm, (4) The ratio of the number average particle diameter to the BET particle diameter (D1 / D2) is 1.5 or less.

2. The colored silica sol according to claim 1, wherein the transition metal T is one or more selected from V, Cr, Mn, Fe, Co, Ni, and Cu.

3. The specific surface area SSA of the core-shell type silica particles in the colored silica sol obtained from the nitrogen adsorption method is 50 m ２ / g or more and 550 m ２ / g or less, and the colored silica sol according to claim 1 or claim 2.

4. The colored silica sol has a particle density PD of core-shell type silica particles in the colored silica sol of at least 2.10 g / cm ３ The colored silica sol according to any one of claims 1 to 3, wherein the above is satisfied.

5. The colored silica sol according to any one of claims 1 to 4, wherein the dried powder obtained by drying the colored silica sol at 100 °C in air is amorphous.

6. The colored silica sol according to any one of claims 1 to 5, wherein the core-shell type silica particles in the colored silica sol are dispersed in an aqueous dispersion medium at a silica concentration of 1% by mass or more and 50% by mass or less.

7. The colored silica sol according to any one of claims 1 to 6, wherein the average particle diameter (D3) of the core-shell type silica particles in the colored silica sol by the dynamic light scattering method is 5 nm or more and less than 100 nm.

8. The colored silica sol according to any one of claims 1 to 7, wherein the existing concentration of the transition metal T present in the dispersion medium of the colored silica sol is less than 0.002% by mass.

9. The colored silica sol, With a UVA-340 lamp, before and after a UV irradiation test under the conditions of a UV irradiation intensity of 0.89 W / m ２ , a temperature of 50 °C, and an irradiation time of 500 h (equivalent to 3.6 months of sunlight), wherein the absorbance change rate represented by the following formula (3) at the absorption wavelength causing the coloring of the colored silica sol by visible ultraviolet spectrum analysis is 50 to 100%, The colored silica sol according to any one of claims 1 to 8. Absorbance change rate (%) = [Absorbance after UV irradiation / Absorbance before UV irradiation] × 100 (3)

10. A method for producing a colored silica sol containing core-shell type silica particles, wherein the core-shell type silica particles are doped with a transition metal, The following steps (a), (b), (c), (d), (e) and (f); Step (a) of contacting an alkaline silicate aqueous solution with a cation exchange resin to prepare an active silicic acid aqueous solution; Step (b) of mixing one or more selected from an alkaline silicate aqueous solution, an active silicic acid aqueous solution, an alkaline aqueous solution, and a transition metal salt compound to prepare a heel liquid having a silica / alkali (molar ratio) of less than 30; Step (c) of preparing a feed liquid composed of one or more selected from an active silicic acid aqueous solution, a transition metal salt compound, and an alkaline aqueous solution; Step (d) of synthesizing silica sol containing silica particles doped with a transition metal by adding the feed liquid to the heel liquid while maintaining the heel liquid in the container at 60°C or higher and 105°C or lower; Step (e) of adding an active silicic acid aqueous solution to the heel liquid while maintaining the heel liquid in the container at 60°C or higher and 105°C or lower after step (d) to form the silica particles doped with the transition metal into core-shell type silica particles and obtaining a colored silica sol containing the core-shell type silica particles; Step (f) of maintaining at an arbitrary temperature of 60°C or higher and 105°C or lower for a certain period of time after step (e) to obtain a sizing liquid; including; However, the transition metal salt compound is added during the preparation of the heel liquid, during the preparation of the feed liquid, or during both preparations, and / or the transition metal salt compound is contained in at least one of the alkaline silicate aqueous solution, the active silicic acid aqueous solution, and the alkaline aqueous solution, The produced core-shell type silica particles have a mass ratio of transition metal T to silica (T / silica) of 0.0001 or more and 0.05 or less, and the number average particle diameter D1 calculated by an image analysis method from an electron microscope image is 5 nm or more and less than 50 nm, and the BET particle diameter D2 calculated by the nitrogen adsorption method is 5 nm or more and less than 50 nm, and the number average particle diameter / BET particle diameter (D1 / D2) ratio is 1.5 or less, A method for producing a colored silica sol.

11. The method for producing a colored silica sol according to claim 10, further comprising step (g) of concentrating the colored silica sol containing the core-shell type silica particles after step (f) to obtain a concentrated liquid.

12. The method for producing a colored silica sol according to claim 10 or claim 11, wherein the alkaline silicate aqueous solution is one or more selected from a lithium silicate aqueous solution, a sodium silicate aqueous solution, and a potassium silicate aqueous solution.

13. The method for producing a colored silica sol according to any one of claims 10 to 12, wherein the aqueous alkali solution is one or more selected from aqueous solutions of lithium hydroxide, sodium hydroxide, potassium hydroxide, and ammonia.

14. The method for producing a colored silica sol according to any one of claims 10 to 13, wherein the metal of the transition metal salt compound is one or more selected from V, Cr, Mn, Fe, Co, Ni, and Cu.

15. The specific surface area of the core-shell type silica particles in the colored silica sol obtained from the nitrogen adsorption method is 50 m ２ / g or more and 550 m ２ / g or less, and the method for producing a colored silica sol according to any one of claims 10 to 14.

16. The colored silica sol has a particle density of core-shell type particles in the colored silica sol of at least 2.10 g / cm ３ The method for producing a colored silica sol according to any one of claims 10 to 15, wherein the above is satisfied.

17. The method for producing a colored silica sol according to any one of claims 10 to 16, wherein the dried powder obtained by drying the colored silica sol at 100 °C in the air is amorphous.

18. The method for producing a colored silica sol according to any one of claims 10 to 17, wherein in the colored silica sol, core-shell type particles in the colored silica sol are dispersed in an aqueous dispersion medium at a silica concentration of 1% by mass or more and 50% by mass or less.

19. The method for producing a colored silica sol according to any one of claims 10 to 18, wherein the average particle diameter (D3) of the core-shell type particles in the colored silica sol by the dynamic light scattering method is 5 nm or more and less than 100 nm.

20. The method for producing a colored silica sol according to any one of claims 10 to 19, wherein the existing concentration of transition metal T dissolved in the dispersion medium of the colored silica sol is less than 0.002% by mass.

21. A pigment composition comprising at least the colored silica sol according to any one of claims 1 to 9.

22. A paint, ink, or glaze comprising at least the pigment composition according to claim 21.

23. A printed matter, film, or molded article comprising at least the pigment composition according to claim 21.

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