Silicate blue pigment and method for producing same

Abstract

Provided are: a silicate-based blue pigment which is inexpensive, has low toxicity, shows a bright blue color, and has high-temperature durability; and a method for producing the silicate-based blue pigment. The silicate blue pigment is characterized in that Mn is doped in the Si site of silicate represented by the following formula (A), and the doping amount of Mn in the Si site is 0.01-50% in 100% of the total number of atoms including Si and Mn. Na2M6Si4O15 (A) (In formula (A), M represents at least one element selected from the group consisting of Ca, Sr, and Ba. )

Description

Technical Field

[0001] This invention relates to silicate-based blue pigments and their manufacturing methods.

[0002] This application claims priority based on Japanese Patent Application No. 2023-187572, filed in Japan on November 1, 2023, the contents of which are incorporated herein by reference. Background Technology

[0003] Inorganic pigments are used as coloring materials in ceramics, glass, plastics, coatings, etc. However, most existing inorganic pigments contain metals that exhibit strong toxicity, necessitating the development of new, environmentally friendly pigments to replace them. For example, the earliest known bright blue pigment is cobalt blue (CI Pigment Blue 28: CoAl2O4 spinel), but its future use is likely to be restricted due to the carcinogenicity of cobalt compounds. A similar concept for blue pigments is YInMn blue (yttrium indium manganese blue, where Y represents yttrium, In represents indium, and Mn represents manganese). For example, Non-Patent Literature 1 reports a YIn blue pigment with an optimal composition. 0.8 Mn 0.2 O3 represents the blue pigment in the CIE color system (L). (~34) and b The value was (~-39). Additionally, the use of the inexpensive transition metal manganese, Ba3(P), as a blue pigment, was reported, despite its lack of known carcinogenicity. 1-x Mn x O4)2(x≤0.25)(Non-patent literature 2).

[0004] On the other hand, Non-Patent Literature 3 reports the formation of Na2Ca6Si4O by a solid-state reaction at 1300°C. 15 Its single-crystal structure.

[0005] Existing technical documents

[0006] Non-patent literature

[0007] Non-patent literature 1: Andrew E. Smith, Matthew C. Comstock, MA Subramanian: Spectral properties of the UV absorbing and near-IR reflecting blue pigment, YIn1-xMnxO3, DYES AND PIGMENTS, Volume 133, 2016, Pages 214-221.

[0008] Non-patent literature 2: LAHA, S., SHARMA, R., BHAT, SV et al.: Ba3(P1-xMnxO4)2: Blue / green inorganic materials based on tetrahedral Mn(V), Bull. Mater. Sci., Volume 34, 2011, Pages 1257-1262.

[0009] Non-patent document 3: Volker Kahlenberg, Matthias Maier: MINERALOGY ANDPETROLOGY, On the existence of a high-temperature polymorph of Na2Ca6Si4O15-implications for the phase equilibria in the system Na2O-CaO-SiO2, Volume110, 2016, pages 905-915. Summary of the Invention

[0010] The problem the invention aims to solve

[0011] However, the YInMn blue disclosed in Non-Patent Document 1, besides being extremely expensive due to indium, also raises concerns about its carcinogenicity, and therefore has been almost entirely unused. On the other hand, there is a demand for blue pigments with better hue compared to the blue pigments disclosed in Non-Patent Document 2. That is, a blue pigment that is inexpensive, low in toxicity, has good hue, and is durable at high temperatures is required.

[0012] The purpose of this invention is to provide a silicate-based blue pigment that is inexpensive, has low toxicity, displays a bright blue color, and has high-temperature durability, as well as a method for manufacturing the same.

[0013] Solution for solving the problem

[0014] To address these issues, the inventors developed a method using Na2Ba6Si4O... 15 Na2Sr6Si4O 15 Na2Ca6Si4O 15 By doping the silicon (Si) sites of isosilicate systems with inexpensive and low-toxicity manganese as a coloring ion, a novel blue pigment exhibiting a bright blue color and high-temperature durability was successfully synthesized.

[0015] The following illustrates embodiments of the present invention.

[0016] [1] A silicate-based blue pigment, wherein Mn is doped at the Si sites of the silicate shown in the following formula (A),

[0017] At the Si site, the doping amount of Mn in the total number of Si and Mn atoms is 0.01~50%.

[0018] Na2M6Si4O 15 (A)

[0019] (In formula (A), M represents at least one of the following groups: Ca, Sr, and Ba.)

[0020] [2] The silicate-based blue pigment described in [1] is represented by the following general formula (1).

[0021] Na2M6(Si 1-x Mn x )4O 15 (1)

[0022] (In equation (1), M represents at least one element selected from the group consisting of Ca, Sr, and Ba. x is 0.001 to 0.5.)

[0023] [3] The silicate-based blue pigment according to [1] or [2] has the crystal structure of silicate shown in formula (A).

[0024] [4] The silicate-based blue pigment according to any one of [1] to [3] is represented by the following formula (1a).

[0025] Na2Ba6(Si 1-x Mn x )4O 15 (1a)

[0026] (In equation (1a), x ranges from 0.001 to 0.5.)

[0027] [5] The silicate-based blue pigment according to any one of [1] to [3] is represented by the following formula (1b).

[0028] Na2Ca6(Si 1-x Mn x )4O 15 (1b)

[0029] (In equation (1a), x ranges from 0.001 to 0.3.)

[0030] [6] A method for manufacturing a silicate-based blue pigment as described in any one of [1] to [5], comprising:

[0031] The mixing process involves mixing Na compound, M compound, Si oxide, and Mn compound; and

[0032] The firing process involves firing the mixture obtained in the mixing process.

[0033] [7] The method for manufacturing silicate-based blue pigment according to [6], wherein the Na compound is at least one selected from the group consisting of NaCl and NaOH.

[0034] [8] The method for manufacturing silicate-based blue pigments according to [6] or [7], wherein the Mn compound is an oxide of Mn.

[0035] [9] A method for manufacturing a silicate-based blue pigment according to any one of [6] to [8], wherein the amount of the Na compound mixed is 5 to 30% by mass excess over the stoichiometry shown in the general formula (A).

[0036]

[10] The method for manufacturing silicate-based blue pigments according to [6] to [9] further includes a washing step using water after the firing step.

[0037] The effects of the invention

[0038] This invention provides a silicate-based blue pigment that is inexpensive, has low toxicity, displays a bright blue color, and is durable at high temperatures, as well as a method for manufacturing the same. Attached Figure Description

[0039] Figure 1 This is a diagram showing the X-ray diffraction patterns of the silicate-based blue pigment (PA) of Examples 1-4 and Comparative Example 1.

[0040] Figure 2 This is a graph showing the ultraviolet-visible reflectance spectra of the silicate-based blue pigment (PA) of Examples 1-4 and Comparative Example 1.

[0041] Figure 3 L represents the blue pigment of Example 1, Comparative Example 2, and Comparative Example 3. a b A diagram of the color space spectrum.

[0042] Figure 4 This is a diagram showing the X-ray diffraction patterns of the silicate-based blue pigments (PA) of Examples 5-8.

[0043] Figure 5 This is a graph showing the heat resistance test results of the silicate-based blue pigment (PA) obtained in Example 1 in Example 9.

[0044] Figure 6 This is a diagram showing the X-ray diffraction patterns of the silicate-based blue pigment (PA) of Examples 10-12 and Comparative Example 4.

[0045] Figure 7 This is a graph showing the ultraviolet-visible reflectance spectra of the silicate-based blue pigments (PA) of Examples 11-12 and Comparative Example 4.

[0046] Figure 8 This is a diagram showing the X-ray diffraction patterns of the silicate-based blue pigment (PA) of Examples 13-19 and Comparative Example 5.

[0047] Figure 9 This is a diagram showing the X-ray diffraction patterns of the silicate-based blue pigments (PA) of Examples 18, 20-22, and Comparative Example 5.

[0048] Figure 10 This is a graph showing the X-ray fluorescence analysis (XRF) results of the silicate-based blue pigment (PA) of Example 18 in Example 23.

[0049] Figure 11 This is a graph showing the ultraviolet-visible reflectance spectra of the silicate-based blue pigments (PA) of Examples 18, 20-22, and Comparative Example 5. Detailed Implementation

[0050] The preferred embodiments of the present invention will now be described in detail.

[0051] (Silicate-based blue pigment (PA))

[0052] The silicate-based blue pigment (PA) of one embodiment of the present invention (sometimes referred to as the silicate-based blue pigment of this embodiment) is obtained by doping Mn at the Si sites of a silicate (sometimes referred to as "silicate (A)") shown in the following formula (A). In the aforementioned Si sites, the doping amount of Mn is 0.01% to 50% of the total number of atoms comprising Si and Mn.

[0053] Na2M6Si4O 15 (A)

[0054] (In formula (A), M represents at least one of the following groups: Ca, Sr, and Ba.)

[0055] The presence of Mn doping at the Si sites of the aforementioned silicate (A) can be confirmed, for example, by X-ray diffraction (XRD). XRD is described in detail in the examples.

[0056] The amount of Mn doping in the silicate-based blue pigment (PA) of this embodiment can be determined using known analytical methods. In this invention, it is calculated by the mixing ratio of the Si-derived raw material Si compound and the Mn-derived raw material Mn compound in the manufacturing method described later. Furthermore, the Si and Mn contents in the silicate-based blue pigment (PA) of this embodiment can also be determined by XRF analysis. Relative to 100% by mass of the aforementioned silicate-based blue pigment (PA), the Si content (converted to SiO2) is preferably 88.4% by mass or more and 99.998% by mass or less, and the Mn content (converted to MnO) is preferably 0.002% by mass or more and 11.6% by mass or less.

[0057] When the determination is performed by XRF analysis, a fluorescence X-ray analysis device (e.g., PrimusIV manufactured by Rigaku Corporation) can be used as the measuring device.

[0058] In the above-mentioned silicate (A), M can be selected from at least one of the group consisting of Ca, Sr and Ba, preferably from at least one of the group consisting of Ca and Ba, and particularly preferably Ba.

[0059] That is, the silicate (A) mentioned above is particularly preferably Na2Ba6Si4O 15 As will be described later, in Na2Ba6Si4O 15 When the Si sites are doped with Mn at a preferred concentration of 0.01 to 30%, more preferably 0.01 to 20%, and even more preferably 0.05 to 20%, a good hue can be obtained as a blue pigment.

[0060] The silicate-based blue pigment of the embodiment has Mn doped at the Si sites of silicate (A), and the amount of Mn doping is 0.01% to 50% relative to 100% of the total number of atoms containing Si and Mn. If the amount of Mn doping is within the aforementioned range, the resulting pigment exhibits a bright blue color. The amount of Mn doping is more preferably 0.01% to 50%, further preferably 0.025% to 40%, and particularly preferably 0.05% to 30%.

[0061] Furthermore, in this embodiment, the silicate (A) is Na2Ca6Si4O 15 In this case, the doping amount of Mn is preferably 0.01~30%, more preferably 0.05~20%.

[0062] In the above silicate (A) being Na2Ba6Si4O 15In this case, the doping amount of Mn is preferably 0.01~30%, more preferably 0.01~20%, and particularly preferably 0.05~20%.

[0063] [Silicate(A)]

[0064] Examples of the aforementioned silicates (A) include Na₂Ca₆Si₄O₂. 15 Na2Sr6Si4O 15 Na2Ba6Si4O 15 The synthesis method, crystal structure, etc. of the above-mentioned non-patent document 3 are described in detail and are cited herein.

[0065] Na2Ca6Si4O 15 Na2Ba6Si4O 15 The crystal structure is a monoclinic system with SiO4 tetrahedral sites. There is no information regarding Na2Sr6Si4O. 15 The report on the crystal structure.

[0066] [Silicate-based blue pigment (PA-1)]

[0067] The silicate-based blue pigment (PA) in this embodiment is preferably the silicate-based blue pigment (PA-1) shown in the following general formula (1).

[0068] Na2M6(Si 1-x Mn x )4O 15 (1)

[0069] (In equation (1), M represents at least one element selected from the group consisting of Ca, Sr, and Ba. x is 0.001 to 0.5.)

[0070] Specific examples of the silicate-based blue pigment (PA-1) of this embodiment include: the silicate-based blue pigment (PA-1a) with M of Ca in formula (1) as shown in formula (1a), the silicate-based blue pigment (PA-1b) with M of Sr in formula (1) as shown in formula (1b), the silicate-based blue pigment (PA-1c) with M of Ba in formula (1) as shown in formula (1c), and the silicate-based blue pigment (PA-1d) with M of both Ca and Ba in formula (1).

[0071] Na2Ca6(Si 1-x Mn x )4O 15 (1a)

[0072] Na2Sr6(Si 1-x Mn x )4O 15(1b)

[0073] Na2Ba6(Si 1-x Mn x )4O 15 (1c)

[0074] Na2(Ca 1-y Ba y )6(Si 1-x Mn x )4O 15 (1d)

[0075] (In equations (1a) to (1d), x has the same meaning as in equation (1). y ranges from 0.1 to 5.9.)

[0076] In this embodiment, the silicate-based blue pigment (PA-1) preferably has M in formula (1) as Ba, i.e., the silicate-based blue pigment (PA-1c) shown in formula (1c). In this case, x in formula (1c) is preferably 0.001 to 0.5, more preferably 0.002 to 0.3, and even more preferably 0.003 to 0.2. If x is within the aforementioned range, the resulting pigment exhibits a more vibrant blue color.

[0077] Specific examples of the silicate-based blue pigment (PA-1) of this embodiment include the following silicate-based blue pigments.

[0078] Na2Ca6(Si 0.99 Mn 0.01 )4O 15 Its color: a bright blue.

[0079] Na2Ca6(Si 0.97 Mn 0.03 )4O 15 Its color: turquoise

[0080] Na2Ca6(Si 0.05 Mn 0.05 )4O 15 Its color scheme: green tones and blue.

[0081] Na2Ba6(Si 0.99 Mn 0.01 )4O 15 Its color: a bright blue.

[0082] Na2Ba6(Si 0.95 Mn 0.05 )4O 15 Its color: sea blue

[0083] Na2Ba6(Si 0.90Mn 0.10 )4O 15 Its color: turquoise

[0084] [Structure of silicate-based blue pigments (PA)]

[0085] It is presumed that the silicate-based blue pigment (PA) of this embodiment has a crystal structure similar to that of the aforementioned silicate (A) which serves as the parent (sometimes referred to as the "parent crystal structure"). In the case where the amount of Mn doping in the Si sites of the silicate-based blue pigment (PA) of this embodiment is high, the crystal structure of the silicate-based blue pigment (PA) of this embodiment may be deformed from the parent crystal structure.

[0086] In the silicate-based blue pigment (PA) of this embodiment, the sodium (Na) sites, barium (Ba) sites, and oxygen (O) sites, other than the Si sites, can be the same elements as those at each site of the aforementioned silicate (A) which serves as the parent material, or they can be different; preferably, they are the same or substantially the same. When Mn is doped into the Si sites, certain adjustments can be made to the oxygen (O) sites, sodium (Na) sites, etc., in order to maintain the overall charge neutrality of the material.

[0087] Manganese (Mn) can exist in several oxidation states (2 to 7 valences). Furthermore, Mn ions can be doped into the Si sites of the aforementioned silicate (A). In this embodiment, the Mn ions doped into the Si sites are preferably 5-valent (Mn²⁺). 5+ ).

[0088] In the aforementioned silicate (A), manganese, particularly pentavalent manganese (Mn), is doped at the Si sites. 5+ This allows for the production of inorganic pigments that exhibit excellent color development and heat resistance.

[0089] [Color gradation of silicate-based blue pigments (PA)]

[0090] For the silicate-based blue pigment (PA) of this embodiment, the L color scale specified in JIS Z8518 and derived from CIE 1976 is... a b In the chromaticity coordinates specified by the color system, L The brightness is preferably 40 or higher, more preferably 45 or higher, and even more preferably 50 or higher. Additionally, L... It can be below 70.

[0091] Furthermore, for the silicate-based blue pigment (PA) of this embodiment, the L color scale specified in JIS Z8518 and derived from the CIE 1976 color scale is... a b In the chromaticity coordinates specified by the color system, a Preferably -5 or less, more preferably -10 or less, and even more preferably -15 or less. Additionally, a It can be above -50.

[0092] Furthermore, for the silicate-based blue pigment (PA) of this embodiment, the L color scale specified in JIS Z8518 and derived from the CIE 1976 color scale is... a b In the chromaticity coordinates specified by the color system, b Preferably below 0, more preferably below -10, and even more preferably below -20. Additionally, b It can be above -60.

[0093] By meeting the conditions mentioned above, a more suitable hue is presented; more specifically, a vibrant blue color scheme is presented.

[0094] Generally speaking, a The square of b The square root of the sum of squares is called chroma (C). This becomes an indicator of vibrancy. When falling into the above category a... b In the range of blue, C The larger it is, the more vibrant the blue becomes, but if it is in C... Based on L The larger the color, the more vibrant it becomes, resulting in a brighter blue.

[0095] By meeting the conditions mentioned above, a more suitable hue is presented; more specifically, a vibrant blue color scheme is presented.

[0096] For example, Na2Ba6(Si) in Example 1 described later. 0.995 Mn 0.005 )4O 15 Silicate-based blue pigments have L (Brightness) = 65.2, a (Red-Green Axis) = -17.8, b With a chromaticity coordinate of -27.1 (yellow-blue axis), it presents a pure and vivid deep blue color.

[0097] Na2Ba6(Si) in Example 2 described later 0.99 Mn 0.01 )4O 15 Silicate-based blue pigments have L (Brightness) = 60.6, a (Red-Green Axis) = -19.3, b With a chromaticity coordinate of -21.9 (yellow-blue axis), it presents a pure and vibrant blue color.

[0098] Thermal stability of silicate-based blue pigments (PA)

[0099] The silicate-based blue pigment (PA) of this embodiment exhibits excellent thermal stability, and specifically, preferably meets the following conditions.

[0100] That is, when the silicate-based blue pigment (PA) of this embodiment is heated at 300~600°C for 6 hours, the ultraviolet-visible reflectance spectrum at a wavelength of 450nm preferably decreases by 10% or less, more preferably by 5% or less.

[0101] Therefore, the silicate-based blue pigment (PA) of this embodiment can maintain its excellent hue even after heat treatment at particularly high temperatures, such as for coloring calcined objects.

[0102] Furthermore, the form of the silicate-based blue pigment (PA) in this embodiment is not particularly limited, but from the viewpoint of being suitable for preparing various coatings, inks, and other compositions containing inorganic pigments, it is preferably granular.

[0103] Examples of possible particle shapes include approximately spherical, polyhedral, spindle-shaped, amorphous, plate-shaped, and needle-shaped. Furthermore, from the perspectives of the fluidity of inorganic pigments themselves, their fluidity when used in the formulation of various coatings, inks, and other compositions, and the stability of the hue of inorganic pigments, the preferred particle shape is one other than plate-shaped or needle-shaped.

[0104] Furthermore, when the silicate-based blue pigment (PA) in this embodiment is in granular form, its average particle size is preferably 0.1 μm or more and 50 μm or less, more preferably 0.2 μm or more and 20 μm or less.

[0105] The silicate-based blue pigment (PA) of this embodiment can be surface-treated for easy dispersion using other inorganic / organic materials and known processing methods. When this surface-treated silicate-based blue pigment (PA) of this embodiment is applied to various coatings, inks, and other compositions containing inorganic pigments, the dispersion stability of the inorganic pigments can be improved.

[0106] Furthermore, in this invention, unless otherwise specified, the average particle size refers to the average particle size based on volume. The average particle size can be determined, for example, by measurement using a particle size analyzer.

[0107] The silicate-based blue pigment (PA) of this embodiment only needs to contain the components of the silicate-based blue pigment (PA) described above, and preferably contains the components of the silicate-based blue pigment (PA-1) shown in formula (1) above. In addition, it may contain other components. Examples of such components include unreacted raw materials, decomposition products of the silicate-based blue pigment (PA) described above, and unavoidable impurities.

[0108] When other components are included, the content of other components is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 2% by mass or less, relative to the silicate-based blue pigment (PA) of this embodiment as a whole.

[0109] The silicate-based blue pigment (PA) of this embodiment exhibits a bright blue color, and therefore can be used for coloring various components.

[0110] In addition, the silicate-based blue pigment (PA) of this embodiment can also be used as a raw material for various coatings and inks.

[0111] In addition, the silicate-based blue pigment (PA) of this embodiment can also be mixed with various resins and glass for use in the manufacture of molded articles.

[0112] Furthermore, the silicate-based blue pigment (PA) of this embodiment can also be used in combination with other coloring materials. For example, it can be applied to a substrate in a prescribed pattern together with other coloring materials to form a color image, or it can be mixed with other coloring materials to express a hue different from the individual hue of the silicate-based blue pigment (PA) of this embodiment.

[0113] In particular, the silicate-based blue pigment (PA) of this embodiment exhibits excellent heat resistance (high-temperature stability) and color durability, enabling it to maintain the specified hue appropriately for an extended period. Therefore, it is especially suitable for use in heated environments, such as for coloring fired objects like pottery and ceramics, and as a colorant for other kiln applications.

[0114] In addition, the silicate-based blue pigment (PA) of this embodiment is not prone to fading, is bright and can maintain its hue appropriately for a long time, and is therefore suitable as a colorant for various inks, such as inkjet inks.

[0115] (Manufacturing method of silicate-based blue pigment (PA))

[0116] A method for manufacturing a silicate-based blue pigment (PA) according to one embodiment of the present invention (sometimes referred to as "the method for manufacturing a silicate-based blue pigment (PA) of this embodiment" or "the manufacturing method of this embodiment") is a method for manufacturing the silicate-based blue pigment (PA) of this embodiment, preferably the silicate-based blue pigment (PA-1) shown in the above general formula (1). The manufacturing method of this embodiment includes: a mixing step, in which a Na compound, an M compound, an oxide of Si, and a Mn compound are mixed to obtain a mixture; and a firing step, in which the mixture obtained in the above mixing step is fired. The aforementioned M has the same meaning as M in the above formula (A) and the above general formula (1).

[0117] The silicate-based blue pigment (PA) of this embodiment can be suitably manufactured by a method comprising the following steps: a mixing step, in which Na compound, M compound, Si oxide and Mn compound as raw materials are mixed to obtain a mixture; and a firing step, in which the mixture obtained in the aforementioned mixing step is reacted to synthesize the target compound. Alternatively, a method named microwave heating or water-assisted solid-state reaction, which is carried out at a lower temperature with a trace amount of water added, can also be used.

[0118] <Mixed Processes>

[0119] In the mixing process, Na compound, M compound, Si oxide and Mn compound, which are used as raw materials, are mixed to obtain a mixture.

[0120] As Na compounds, M compounds and Mn compounds, at least one of metal carbonate salts and metal oxides can be used, for example.

[0121] Examples of Na compounds include NaCl, Na₂CO₃, and NaOH. In this embodiment, from a reactivity point of view, it is preferable to use at least one compound selected from the group consisting of NaCl and NaOH, and more preferably NaCl.

[0122] Examples of M compounds include MCO3 and MO, with MCO3 being preferred. For example, examples of Ca compounds include CaCO3 and CaO, with CaCO3 being preferred. Examples of Sr compounds include SrCO3 and SrO, with SrCO3 being preferred. Examples of Ba compounds include BaCO3 and BaO, with BaCO3 being preferred.

[0123] Examples of Mn compounds include MnO2 and MnCO3. In this embodiment, an oxide of Mn, namely MnO2, is preferred.

[0124] Examples of oxides of Si include SiO2, with amorphous silicon dioxide being the most preferred.

[0125] The silicate-based blue pigment (PA) of this embodiment can be made from raw materials of any shape, preferably granular. This allows for the appropriate mixing of multiple raw materials, and more effectively prevents unintended compositional inconsistencies or unintentional residues of unreacted raw materials from forming in the manufactured inorganic pigment.

[0126] The average particle size of the raw material for the silicate-based blue pigment (PA) in this embodiment is preferably 0.1 μm or more and 50 μm or less.

[0127] As a result, raw material processing becomes easier, and the aforementioned problems can be prevented more effectively. Furthermore, the solid-phase reaction in the firing process can be carried out more appropriately, leading to an increase in the productivity of inorganic pigments.

[0128] In this process, the aforementioned raw materials are usually weighed and mixed according to the stoichiometric ratio.

[0129] For example, in the case of manufacturing the silicate-based blue pigment (PA) of this embodiment, the aforementioned stoichiometric ratio is the ratio of the mixing amounts of each raw material calculated based on the above formula (A) and the doping amount theory of Mn. On the other hand, for example, in the case of manufacturing the aforementioned silicate-based blue pigment (PA-1), the mixing amount ratio of each raw material is calculated based on the above general formula (1).

[0130] As a mixing method, conventional methods such as using a mortar and pestle or a ball mill can be employed. Alternatively, dry mixing or wet mixing (more specifically, wet mixing using highly volatile solvents such as alcohols or acetone) can be used, with wet mixing being preferred. In wet mixing, highly volatile solvents such as alcohols or acetone are more preferably used. According to wet mixing, the raw material powder tends to aggregate more easily, and powder dispersion can be more effectively prevented.

[0131] In the mixing step of the manufacturing method of this embodiment, the Na compound can be mixed in excess of the amount specified in the stoichiometric ratio, as needed. By adding an excess of the Na compound compared to the stoichiometric ratio, the remaining portion acts as a fluxing agent, promoting the growth of the target crystal and thereby improving the homogeneity of the target material.

[0132] Regarding the amount of Na compound in the blend, specifically, for example, when the amount of Na compound according to the above stoichiometric ratio is 100 parts by mass, the total amount of Na compound in the blend can be set within the range of 101 parts by mass to 150 parts by mass. That is, when the amount of Na compound according to the above stoichiometric ratio is 100 parts by mass, the total amount of Na compound in the blend can be 102 parts by mass (referred to as excess of 2% by mass) or more, 105 parts by mass (referred to as excess of 5% by mass) or more, 110 parts by mass (referred to as excess of 10% by mass) or more, 120 parts by mass (referred to as excess of 20% by mass) or more, 130 parts by mass (referred to as excess of 30% by mass) or more, and can be 150 parts by mass (referred to as excess of 50% by mass) or less, 140 parts by mass (referred to as excess of 40% by mass) or less, or 130 parts by mass (referred to as excess of 30% by mass) or less.

[0133] In this embodiment, the amount of Na compound mixed is preferably 5 to 30% by mass excess over the stoichiometry shown in the aforementioned general formula (A), more preferably 6% by mass or more and 20% by mass or less excess, and particularly preferably 10% by mass or more and 20% by mass or less excess. By keeping the amount of Na compound mixed within the aforementioned range, the operability when removing the target material from the container after the firing process becomes good.

[0134] When the Na compound is mixed in excess of the amount specified in the above stoichiometric ratio, the Na compound is preferably NaCl or NaOH, and more preferably NaCl.

[0135] When Na compound is mixed in excess of the amount specified in the stoichiometric ratio, in subsequent examples (where the Na compound is NaCl), based on X-ray diffraction patterns or X-ray fluorescence (XRF) analysis results, since no residual Cl or the like was observed in the final product, it is presumed that the Na compound acts as a flux. Furthermore, in some examples, it was observed that samples with a 0% (by mass) excess of NaCl (samples in which Na compound was mixed according to the specified stoichiometric ratio) yielded almost no target material, suggesting that molten NaCl affects the diffusion rate.

[0136] <Firing Process>

[0137] In the firing process, the mixture obtained in the above mixing process is fired.

[0138] There are no particular restrictions on the atmosphere during the firing process. The firing process can be carried out, for example, in the atmosphere or in an inert gas atmosphere.

[0139] The preferred heating temperature in the firing process is above 800℃ and below 1500℃.

[0140] The heating time in the firing process is preferably more than 5 hours and less than 24 hours.

[0141] <Molding Process>

[0142] The manufacturing method of this embodiment may further include a molding step, which involves shaping the mixture of raw material powders into granules, after the mixing step and before the firing step. By shaping the mixture of raw material powders into granules, a dense fired product is obtained in the firing step, resulting in an inorganic pigment with excellent properties. Furthermore, by shaping into granules and firing, the raw material efficiency is also improved.

[0143] The molding pressure in the mixing process is preferably above 5 MPa and below 20 MPa.

[0144] <Cleaning Process>

[0145] The manufacturing method of this embodiment may further include a cleaning step using acid, alkali, water, or organic solvent after the above-described firing step. By performing the cleaning step, byproduct ionic components, salts, or aggregated particles can be removed, and the pigments can be appropriately used to improve the hiding power or dispersibility of the silicate-based blue pigment of this invention when used in coatings.

[0146] The preferred embodiments of the present invention have been described above, but the present invention is not limited thereto.

[0147] Example

[0148] The following examples further illustrate this embodiment. The present invention is not limited thereto.

[0149] (raw material)

[0150] NaCl powder: Trade name: Sodium chloride (I), 99.9%, manufactured by High Purity Chemical Co., Ltd.

[0151] Na2CO3 powder: Trade name: Sodium carbonate, 99.8%, manufactured by Kanto Chemical Co., Ltd.

[0152] BaCO3 powder: Trade names: Barium carbonate, 4N, manufactured by Kanto Chemical Co., Ltd.

[0153] SrCO3 powder: Trade name: Strontium carbonate, 4N, manufactured by Kanto Chemical Co., Ltd.

[0154] CaCO3 powder: Trade names: calcium carbonate, 4N, manufactured by Kanto Chemical Co., Ltd.

[0155] SiO2 powder: Trade name: Silica, 99.9%, manufactured by Fujifilm and Kojun Pharmaceutical Co., Ltd.

[0156] MnO2 powder: Trade name: Manganese oxide (IV), 99.5%, manufactured by Wako Pure Chemical Industries, Ltd.

[0157] (Evaluation Method)

[0158] [XRD]

[0159] Measurement apparatus: MX-Labo powder X-ray diffractometer (manufactured by Mac Science)

[0160] Measurement conditions: X-ray: Cu / 40kV / 25mA

[0161] Diverging slit: 1°

[0162] Scattering slit: 1°

[0163] Light-receiving slit: 0.15nm

[0164] Detector: Blink Counter

[0165] Scanning speed: 0.02° / second

[0166] Scanning range: 10~50°

[0167] [UV-Vis Reflectance Spectrum]

[0168] Measurement Apparatus: UV-Vis Spectrophotometer V-630DS (manufactured by Japan Spectrophotometer Co., Ltd.)

[0169] Measurement conditions: An integrating sphere unit (ISV-722, manufactured by Nippon Seiko Co., Ltd.) was installed in the measurement. The prepared barium sulfate was used in the baseline measurement. Based on this, the spectral reflectance of diffuse light, including specular reflection, was measured in the wavelength range of 300–800 nm when 30 mg of inorganic pigment was filled at a filling rate of 50% or higher into the window (φ5 mm) of a micro-powder cell (PSH-003, manufactured by Nippon Seiko Co., Ltd.).

[0170] [XRF]

[0171] Measurement apparatus: Fluorescence spectrophotometer (Japan Spectrophotometer Co., Ltd., FP-6500 model)

[0172] Measurement conditions: excitation bandwidth: 10 nm, emission bandwidth: 10 nm, fluorescence spectrum measured in vacuum mode.

[0173] [CIE L a b ]

[0174] Measuring apparatus: CR-300 colorimeter (manufactured by Konica Minolta, Inc.)

[0175] Test conditions: Samples were prepared by compressing and granulating the inorganic pigments. Each sample was heated at 300°C, 600°C, and 1000°C, respectively, to meet the requirements of the CIE L test. a b The same evaluation.

[0176] [Heat Resistance Test]

[0177] Measuring apparatus: CR-300 colorimeter (manufactured by Konica Minolta, Inc.)

[0178] Test conditions: Samples were prepared by compressing and granulating the inorganic pigments. Each sample was heated at 300°C, 600°C, and 1000°C, respectively, to meet the requirements of the CIE L test. a b The same evaluation.

[0179] (Example 1)

[0180] As raw materials, NaCl powder, BaCO3 powder, SiO2 powder, and MnO2 powder were prepared to achieve the composition ratio shown in Table 1 [Na2Ba6(Si 0.995 Mn 0.005 )4O 15 NaCl powder, BaCO3 powder, SiO2 powder, and MnO2 powder were weighed according to stoichiometric ratios.

[0181] Next, the powdered raw materials were mixed using an agate mortar. At this point, acetone was used as a solvent for wet mixing, and after drying, a mixture of raw materials was obtained.

[0182] The mixture of raw materials is calcined at 900°C for 6 hours in the atmosphere.

[0183] The above operations produced a product derived from the formula [Na2Ba6(Si]). 0.995 Mn 0.005 )4O 15 ] represents a silicate-based blue pigment.

[0184] The obtained silicate-based blue pigment was subjected to powder X-ray diffraction, diffuse reflectance spectroscopy, and colorimetric determination using the methods described above. Regarding colorimetric properties, L... a b The color scheme indicates the evaluation of L. (brightness), a (Positive direction: Red, Negative direction: Green), b (Positive direction: Yellow, Negative direction: Blue). Displays a vibrant blue.

[0185] These results are shown in Table 1. Figures 1-3 .

[0186] (Examples 2-4, Comparative Example 1)

[0187] The silicate-based blue pigment was manufactured using the same method as in Example 1, with the composition shown in Table 1.

[0188] The evaluation was conducted using the same method as in Example 1. These results are shown in Table 1. Figures 1-3 .

[0189] (Example 5)

[0190] CaCO3 powder was mixed in place of BaCO3 powder, and NaCl powder was weighed in excess by 20% by mass (i.e., 120 parts by mass of NaCl powder were weighed when the stoichiometric ratio was 100 parts by mass). Otherwise, a silicate-based blue pigment was produced by the same method as in Example 2.

[0191] Powder X-ray diffraction and colorimetric measurements were performed using the same method as in Example 1. These results are shown in Table 1. Figure 4 .

[0192] (Examples 6-8)

[0193] The silicate-based blue pigment was manufactured using the same method as in Example 5, with the composition shown in Table 1.

[0194] Powder X-ray diffraction and colorimetric measurements were performed using the same method as in Example 5.

[0195] These results are shown in Table 1. Figure 4 .

[0196] (Example 9)

[0197] Using the silicate-based blue pigment obtained in Example 1, diffuse reflectance spectra were measured under the following treatment conditions, and heat resistance tests were conducted.

[0198] Temperature conditions: 300℃ / 600℃ / 900℃

[0199] Firing time: 6 hours

[0200] The results are shown in Table 5. Figure 5 In the figure, “sample”, “300℃”, “600℃” and “900℃” are the diffuse reflectance spectra before heat treatment, after treatment at 300℃, after treatment at 600℃ and after treatment at 900℃, respectively.

[0201] [Table 1]

[0202]

[0203] (Comparative Example 2)

[0204] "L of inorganic pigment CoAl2O4" a b Measurement of color space

[0205] The L content of the inorganic pigment CoAl2O4 obtained using the method described in Non-Patent Literature A1 was determined by the same method as in Example 1. a b Color space. The results are shown in Table 1.

[0206] [Non-Patent Literature A1] Simeen Sattar, J. Chem. Educ. 96, 1124-1128, (2019).

[0207] (Comparative Example 3)

[0208] Inorganic pigments YIn 0.95 Mn 0.05 O3 of L a b Measurement of color space

[0209] The inorganic pigment YIn obtained using the method described in Non-Patent Document A2 below was measured using the same method as in Example 1. 0.95 Mn 0.05 O3 of L a b Color space. The results are shown in Table 1.

[0210] [Non-patent literature A2] Andrew E. Smith et al., DYES PIGMENT, 133, 214-221, (2016).

[0211] (Example 10)

[0212] Using the composition ratios shown in Table 2, SrCO3 powder was mixed in place of BaCO3 powder, and otherwise, a silicate-based blue pigment was produced by the same method as in Example 1.

[0213] Powder X-ray diffraction and colorimetric measurements were performed using the same method as in Example 1. These results are shown in Table 2. Figure 6 , 7 .

[0214] (Examples 11, 12, and Comparative Example 4)

[0215] Using the composition ratios shown in Table 2, SrCO3 powder was mixed in place of BaCO3 powder, and otherwise, a silicate-based blue pigment was produced by the same method as in Example 5.

[0216] Powder X-ray diffraction and colorimetric measurements were performed using the same method as in Example 1. These results are shown in Table 2. Figure 6 , 7 .

[0217] [Table 2]

[0218]

[0219] (Example 13)

[0220] Using the composition ratios shown in Table 3, CaCO3 powder was mixed instead of BaCO3 powder, and otherwise, a silicate-based blue pigment was produced by the same method as in Example 1.

[0221] Powder X-ray diffraction and colorimetric measurements were performed using the same method as in Example 1. These results are shown in Table 3. Figure 8 .

[0222] (Examples 14-19)

[0223] The amount of NaCl powder mixed was the amount recorded in Table 3, and the silicate-based blue pigment was prepared by the same method as in Example 13.

[0224] Powder X-ray diffraction and colorimetric measurements were performed using the same method as in Example 1. These results are shown in Table 3. Figure 8 In Example 18, diffuse reflectance spectroscopy was performed using the same method as in Example 1. These results are shown below. Figure 11 .

[0225] (Examples 20-22)

[0226] The silicate-based blue pigment was manufactured using the same method as in Example 18, except that the composition ratios shown in Table 3 were used.

[0227] Powder X-ray diffraction, colorimetry, and diffuse reflectance spectroscopy were performed using the same methods as in Example 1. These results are shown in Table 3. Figure 9 , Figure 11 .

[0228] (Comparative Example 5)

[0229] The composition ratio is set to Na2Ca6Si4O15 In addition, silicate-based blue pigments are manufactured using the same method as in Example 18.

[0230] Powder X-ray diffraction and diffuse reflectance spectroscopy were performed using the same method as in Example 1. These results are presented below. Figure 9 , Figure 11 .

[0231] (Example 23)

[0232] Fluorescence X-ray spectroscopy (XRF) analysis was performed using the silicate-based blue pigment obtained in Example 18. The results are shown below. Figure 10 .

[0233] [Table 3]

[0234]

[0235] (Inspection)

[0236] According to Table 1, Figures 1-5 As a result, in the case of M=Ba, the target compound was obtained as the main phase in all samples with Mn content, Na2Ba6(Si 0.995 Mn 0.005 )4O 15 The most vibrant blue coloration was observed. Furthermore, no significant differences were identified compared to samples synthesized using excess NaCl.

[0237] According to Table 2, Figure 6 and 7 As a result, when M=Sr, Sr2SiO4 is obtained as the product.

[0238] According to Table 3, Figures 8-11 As a result, in the case of M=Ca, the target compound was obtained as a mixed phase in all samples with Mn content, Na2Ca6(Si 0.99 Mn 0.1 )4O 15 Displays the most vibrant blue hue.

[0239] according to Figure 3 L a b The color space results showed that the sample exhibited a blue tint. It was confirmed that the sample was a bright blue compared to Comparative Example 2, and a greenish blue compared to Comparative Example 3.

[0240] according to Figure 5 The results of the heat resistance test confirmed high heat resistance up to 600℃.

[0241] according to Figure 8Results of NaCl-flux amount (NaCl excess) and Figure 10 The XRF results confirmed that the NaCl-flux content (NaCl excess) was 20 wt%, with few impurities and a bright blue color. Furthermore, since no Cl peak was observed in the water-washed sample during the XRF measurements, it was concluded that the Cl from the NaCl-flux (excess NaCl) was not incorporated into the crystals.

Claims

1. A silicate-based blue pigment, wherein Mn is doped at the Si sites of the silicate represented by the following formula (A), At the Si site, the Mn doping amount in the total number of Si and Mn atoms is 0.01~50%. Na2M6Si4O 15 (A) In formula (A), M represents at least one of the following groups: Ca, Sr, and Ba.

2. The silicate-based blue pigment according to claim 1, which is represented by the following general formula (1), Na2M6(Si 1-x Mn x )4O 15 (1) In equation (1), M represents at least one of the groups consisting of Ca, Sr and Ba, and x is 0.001 to 0.

5.

3. The silicate-based blue pigment according to claim 1, having the crystal structure of the silicate shown in formula (A).

4. The silicate-based blue pigment according to claim 1, which is represented by the following formula (1a), Na2Ba6(Si 1-x Mn x )4O 15 (1a) In equation (1a), x is 0.001~0.

5.

5. The silicate-based blue pigment according to claim 1, which is represented by the following formula (1b), Na2Ca6(Si 1-x Mn x )4O 15 (1b) In equation (1a), x is 0.001~0.

3.

6. A method for manufacturing a silicate-based blue pigment according to any one of claims 1 to 5, comprising: The mixing process involves mixing Na compound, M compound, Si oxide and Mn compound; as well as The firing process involves firing the mixture obtained in the mixing process.

7. The method for manufacturing a silicate-based blue pigment according to claim 6, wherein, The Na compound is selected from at least one of the groups consisting of NaCl and NaOH.

8. The method for manufacturing a silicate-based blue pigment according to claim 6, wherein, The Mn compound is an oxide of Mn.

9. The method for manufacturing a silicate-based blue pigment according to claim 6, wherein, The amount of the Na compound mixed is 5 to 30% excess by mass compared to the stoichiometry shown in the general formula (A).

10. The method for manufacturing a silicate-based blue pigment according to claim 6, wherein, After the firing process, a cleaning process using water is also included.

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