Inorganic pigment

Abstract

To provide a blue-green inorganic pigment having low toxicity and excellent color development and stability.SOLUTION: The inorganic pigment of the present invention is represented by the following formula (1): Na2(1-x)A12xCu3(1-y)A23yGe4(1-z)A34zO12 (1) (In formula (1), A1 is at least one selected from the group consisting of Li and K, A2 is at least one selected from the group consisting of Ni, Zn, Mg, Mn, and Fe, A3 is at least one selected from the group consisting of Ni, Mn, Fe, Sn, Si, P, Al, and Ga, and the conditions 0.00≤x≤0.30, 0.00≤y≤0.30, and 0.00≤z≤0.30 are satisfied.)SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to inorganic pigments. [Background technology]

[0002] Pigments are used as colorants in paints, inks, and the like.

[0003] Phthalocyanine pigments are well known as blue-green pigments. Phthalocyanine pigments are vivid and have very strong coloring power, and because of the high fastness derived from the phthalocyanine structure, they exhibit high light resistance and weather resistance (see, for example, Patent Document 1). Therefore, they are used as colorants in a wide range of applications, such as inks, plastics, paints, toners, and color filters.

[0004] However, because phthalocyanine pigments are organic substances (organic pigments), they have problems with heat resistance and are not suitable for use at high temperatures of several hundred degrees Celsius or higher. For example, when used to color pottery such as ceramics and earthenware, the color is likely to deteriorate due to the high temperatures during baking.

[0005] Inorganic pigments have higher heat resistance and higher color clarity than organic pigments, and are therefore widely used as colorants in resin compounds, glass pastes, paints, traffic paints, ceramics, building materials, cosmetics, and the like.

[0006] Turquoise (CuAl6(PO4)4(OH)8·2H2O) has long been known as a blue-green inorganic pigment.

[0007] Turquoise is a low-toxicity material that does not contain heavy metals that have a high environmental impact, such as cobalt and chromium (hereinafter referred to as "specific heavy metals"). However, it has a pale color, poor chemical resistance, and poor high-temperature stability, making it difficult to use stably as a material.

[0008] Cobalt chrome blue (Co(Cr,Al)2O4) has also been used as a blue-green inorganic pigment. Furthermore, studies have been conducted to achieve even more vivid and diverse colors, and blue-green pigments composed of alkali metals, cobalt, and titanium oxides are known. While these pigments have the advantage of being vivid in color, they contain heavy metals such as cobalt and chromium that have a high environmental impact (hereinafter referred to as "specific heavy metals"), and in recent years, their production, import, export, and use have been restricted or prohibited under directives on hazardous substances such as RoHS and PRTR.

[0009] Cobalt is widely used in pigments such as cobalt chrome blue (Co(Cr,Al)2O4) and cobalt blue (CoAl2O4) because of its vivid color tones. However, in addition to its toxicity, it also has the problem of unstable supply because the main producing countries are located in politically unstable regions.

[0010] Because chromium produces vivid colors, it is widely used in chemically stable inorganic pigments such as chromium oxide green (Cr2O3), chrome green ((AlCr)2O3), and cobalt chrome blue / cobalt green (Co(Cr,Al)2O4). However, because hexavalent chromium is extremely toxic, there is a trend toward restricting the use of chromium itself.

[0011] Therefore, in this field, blue-green inorganic pigments that do not contain specific heavy metals have been investigated, but so far there have been no pigments that have excellent color development and stability. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Japanese Patent Publication No. 2020-117560 Summary of the Invention [Problem to be solved by the invention]

[0013] An object of the present invention is to provide a bluish-green inorganic pigment which is low in toxicity and has excellent color development and stability. [Means for solving the problem]

[0014] Such an object can be achieved by the present invention described below. The inorganic pigment of the present invention is characterized by being represented by the following formula (1): Na 2(1-x) A 1 2x Cu 3(1-y) A 2 3y Ge 4(1-z) A 3 4z O 12 (1) (In formula (1), A 1 is at least one selected from the group consisting of Li and K, and A 2 is at least one selected from the group consisting of Ni, Zn, Mg, Mn and Fe, and A 3 is at least one selected from the group consisting of Ni, Mn, Fe, Sn, Si, P, Al, and Ga, and satisfies the conditions 0.00≦x≦0.30, 0.00≦y≦0.30, and 0.00≦z≦0.30.

[0015] The inorganic pigment of the present invention preferably has a copper trimer unit [Cu3O8] in its crystal structure.

[0016] The inorganic pigment of the present invention preferably has a triclinic unit cell. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a bluish-green inorganic pigment that is low in toxicity and has excellent color development and stability. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a diagram showing a schematic diagram of the crystal structure of Na2Cu3A3zGe4O12. [Figure 2] FIG. 2 is a flow chart showing an example of the steps of the method for producing an inorganic pigment of the present invention. [Figure 3] FIG. 3 is a view showing an SEM photograph of the inorganic pigment of Example 1. [Figure 4] FIG. 4 shows SEM photographs of the inorganic pigments of Examples 62 to 64. [Figure 5] FIG. 5 shows SEM photographs of the inorganic pigments of Examples 65 to 67. [Figure 6] FIG. 6 shows SEM photographs of the inorganic pigments of Examples 68 to 70. [Figure 7] FIG. 7 shows the X-ray diffraction patterns of the inorganic pigments of Examples 1 to 10. [Figure 8] FIG. 8 shows the X-ray diffraction patterns of the inorganic pigments of Examples 11 to 14. [Figure 9] FIG. 9 is a diagram showing the X-ray diffraction patterns of the inorganic pigments of Examples 1 and 14 to 17. [Figure 10] FIG. 10 shows the X-ray diffraction patterns of the inorganic pigments of Examples 18 to 21. [Figure 11] FIG. 11 is a diagram showing the X-ray diffraction patterns of the inorganic pigments of Example 22 and Comparative Example 1. [Figure 12] FIG. 12 is a diagram showing the X-ray diffraction patterns of the inorganic pigments of Examples 23 to 25 and Comparative Examples 2 and 3. [Figure 13] FIG. 13 is a diagram showing the X-ray diffraction patterns of the inorganic pigments of Examples 26 to 28 and Comparative Example 4. [Figure 14] FIG. 14 shows the X-ray diffraction patterns of the inorganic pigments of Examples 29 to 32. [Figure 15] FIG. 15 is a diagram showing the X-ray diffraction pattern for the inorganic pigment of Example 33. [Figure 16] FIG. 16 is a diagram showing the X-ray diffraction patterns of the inorganic pigments of Examples 1 and 33 to 42. [Figure 17] FIG. 17 shows the X-ray diffraction patterns of the inorganic pigments of Examples 43 to 46. [Figure 18] FIG. 18 is a diagram showing the X-ray diffraction patterns of the inorganic pigments of Examples 47 to 52, 56, and 60. [Figure 19] FIG. 19 is a diagram showing the X-ray diffraction patterns of the inorganic pigments of Examples 53 to 55 and 57. [Figure 20] FIG. 20 is a diagram showing the X-ray diffraction patterns of the inorganic pigments of Examples 1 and 58 to 61. [Figure 21] FIG. 21 is a diagram showing the X-ray diffraction patterns of the inorganic pigments of Examples 1, 60, and 62 to 70. [Figure 22] FIG. 22 is a diagram showing the diffuse reflectance spectra of the inorganic pigments of Examples 1 to 10, measured by ultraviolet-visible spectroscopy. [Figure 23] FIG. 23 is a diagram showing the diffuse reflectance spectra of the inorganic pigments of Examples 14 to 17, measured by ultraviolet-visible spectroscopy. [Figure 24] FIG. 24 is a diagram showing the diffuse reflectance spectra of the inorganic pigments of Examples 33 to 42, measured by ultraviolet-visible spectroscopy. [Figure 25] FIG. 25 is a diagram showing the diffuse reflectance spectra of the inorganic pigments of Examples 60 and 62 to 70, measured by ultraviolet-visible spectroscopy. [Figure 26] FIG. 26 is a diagram showing X-ray diffraction patterns of the inorganic pigment of Example 1 after the heat resistance test, moisture resistance test, acid resistance test, and base resistance test. [Figure 27] FIG. 27 is a diagram showing the X-ray diffraction patterns of the inorganic pigment of Example 14 after the heat resistance test, moisture resistance test, and base resistance test. [Figure 28] FIG. 28 is a diagram showing the X-ray diffraction patterns of the inorganic pigment of Example 21 after the heat resistance test, moisture resistance test, acid resistance test, and base resistance test. [Figure 29] FIG. 29 is a diagram showing the X-ray diffraction patterns of the inorganic pigment of Example 23 after the heat resistance test, moisture resistance test, and base resistance test. [Figure 30]FIG. 30 shows X-ray diffraction patterns of the inorganic pigment of Example 26 after heat resistance test, moisture resistance test, acid resistance test, and base resistance test. [Figure 31] FIG. 31 shows the X-ray diffraction patterns of the inorganic pigment of Example 29 after the heat resistance test, moisture resistance test, acid resistance test, and base resistance test. [Figure 32] FIG. 32 is a diagram showing the X-ray diffraction patterns of the inorganic pigment of Example 33 after the heat resistance test, moisture resistance test, acid resistance test, and base resistance test. [Figure 33] FIG. 33 shows X-ray diffraction patterns of the inorganic pigment of Example 47 after the heat resistance test, moisture resistance test, acid resistance test, and base resistance test. [Figure 34] FIG. 34 is a diagram showing the X-ray diffraction patterns of the inorganic pigment of Example 48 after the heat resistance test, moisture resistance test, acid resistance test, and base resistance test. [Figure 35] FIG. 35 is a diagram showing the X-ray diffraction patterns of the inorganic pigment of Example 49 after the heat resistance test, moisture resistance test, acid resistance test, and base resistance test. [Figure 36] FIG. 36 shows X-ray diffraction patterns of the inorganic pigment of Example 50 after heat resistance test, moisture resistance test, acid resistance test, and base resistance test. [Figure 37] FIG. 37 shows X-ray diffraction patterns of the inorganic pigment of Example 51 after heat resistance test, moisture resistance test, acid resistance test, and base resistance test. [Figure 38] FIG. 38 shows X-ray diffraction patterns of the inorganic pigment of Example 52 after the heat resistance test, moisture resistance test, acid resistance test, and base resistance test. [Figure 39] FIG. 39 is a diagram showing the X-ray diffraction patterns of the inorganic pigment of Example 53 after the heat resistance test, moisture resistance test, acid resistance test, and base resistance test. [Figure 40]FIG. 40 shows X-ray diffraction patterns of the inorganic pigment of Example 60 after heat resistance test, moisture resistance test, acid resistance test, and base resistance test. DETAILED DESCRIPTION OF THE INVENTION

[0019] Preferred embodiments of the present invention will be described in detail below. [1] Inorganic pigments First, the inorganic pigment of the present invention will be described.

[0020] However, until now, there has been no blue-green inorganic pigment that is low in toxicity and has excellent color development and stability. Therefore, the present inventors have conducted extensive research with the aim of obtaining a blue-green inorganic pigment that combines these excellent properties. As a result, they have succeeded in obtaining a novel inorganic pigment that achieves the above-mentioned objectives. That is, the inorganic pigment of the present invention is represented by the following formula (1).

[0021] Na 2(1-x) A 1 2x Cu 3(1-y) A 2 3y Ge 4(1-z) A 3 4z O 12 (1) (In formula (1), A 1 is at least one selected from the group consisting of Li and K, and A 2 is at least one selected from the group consisting of Ni, Zn, Mg, Mn and Fe, and A 3 is at least one selected from the group consisting of Ni, Mn, Fe, Sn, Si, P, Al, and Ga, and satisfies the conditions 0.00≦x≦0.30, 0.00≦y≦0.30, and 0.00≦z≦0.30.

[0022] Such inorganic pigments exhibit a blue-green color, are low in toxicity, and have excellent color development and stability. They are particularly excellent in heat resistance, water resistance, moisture resistance, acid resistance, and base resistance. In particular, the constituent elements of the inorganic pigment of the present invention are particularly less toxic than cobalt (Co) and chromium (Cr), which have been used in conventional inorganic pigments. Furthermore, copper is relatively inexpensive (for example, about 1 / 4 of the cost of cobalt), has a stable supply, and is easily available, making it suitable as a material for inorganic pigments. Furthermore, the additive element A 1 , A 2 , A 3 By adjusting the type and substitution ratio of the inorganic pigment, the color tone and the like of the inorganic pigment can be suitably adjusted.

[0023] On the other hand, if the above conditions are not met, satisfactory results will not be obtained. For example, if the above formula does not contain Na or if the value of x is too large, the overall color will be a dark blue-green color, and a vivid blue-green color will not be obtained.

[0024] Furthermore, if the above formula does not contain Cu or if the value of y is too large, problems arise such as difficulty in expressing a vivid blue-green color or an overall whitish color.

[0025] Furthermore, if the above formula does not contain Ge or if the value of z is too large, problems arise such as difficulty in expressing a vivid blue-green color or an overall blackish color.

[0026] As described above, the inorganic pigment of the present invention contains Na, Cu, Ge and O as constituent elements. 1 , A 2 and A 3 It may contain at least one of the following.

[0027] This makes it possible to, for example, suitably control the color tone of the inorganic pigment, further improve the color development and heat resistance, and further reduce the production cost of the inorganic pigment.

[0028] A 1 is sufficient as long as it is at least one selected from the group consisting of Li and K, but preferably contains at least Li, and more preferably is Li. This results in a more greenish color tone and a deeper color tone.

[0029] A 2 is sufficient as long as it is at least one selected from the group consisting of Ni, Zn, Mg, Mn and Fe, but preferably contains at least Zn, and more preferably is Zn. This results in a more greenish color tone and a deeper color tone.

[0030] A 3 is at least one selected from the group consisting of Ni, Mn, Fe, Sn, Si, P, Al and Ga, but preferably contains at least Si, and more preferably is Si.

[0031] This allows a bluish color tone to be obtained, and also makes it possible to increase the brightness of the inorganic pigment, resulting in a more vivid color tone.

[0032] In particular, A 1 is Li and A 2 is Zn and A 3 More preferably, is Si.

[0033] This results in a particularly well-balanced color tone, allowing for the expression of a bright blue-green color tone.

[0034] In the above formula (1), x may satisfy the condition 0.00≦x≦0.30, preferably 0.00≦x≦0.10, more preferably 0.01≦x≦0.05, and even more preferably 0.02≦x≦0.03. This makes the above-mentioned effects more pronounced.

[0035] In the above formula (1), y may satisfy the condition 0.00≦y≦0.30, preferably 0.05≦y≦0.15, more preferably 0.06≦y≦0.13, and even more preferably 0.07≦y≦0.09. This makes the above-mentioned effects more pronounced.

[0036] In the above formula (1), z may satisfy the condition 0.00≦z≦0.30, preferably 0.00≦z≦0.29, more preferably 0.01≦z≦0.25, and even more preferably 0.01≦z≦0.24. This makes the above-mentioned effects more pronounced.

[0037] The parent crystal of the inorganic pigment of the present invention is Na2Cu3Ge4O 12 Its crystal structure is typically composed of a Na ion, a trimeric unit [Cu3O8] consisting of three square planar tetrahedral copper (Cu) and oxygen atoms, and a unit [GeO4] consisting of tetrahedral germanium (Ge) and oxygen atoms, as shown in Figure 1. The trimeric unit [Cu3O8] consists of three square planar tetrahedral copper and oxygen atoms.

[0038] In addition, the parent crystal of the inorganic pigment of the present invention, Na2Cu3Ge4O 12 has a crystal structure with a triclinic unit cell.

[0039] The inorganic pigment of the present invention has a copper trimer unit [Cu3O8] in its crystal structure, which makes it possible to improve the color development properties of the inorganic pigment.

[0040] When the inorganic pigment of the present invention has a triclinic unit lattice, the color development properties of the inorganic pigment can be made even more excellent.

[0041] In the inorganic pigment of the present invention, Cu can exist in several acid value states such as monovalent and divalent. 2+ ) is preferably present. This allows the inorganic pigment to have better color development properties.

[0042] The inorganic pigment of the present invention contains the above-mentioned constituent elements (Na, Cu, Ge, O, A 1 , A 2 , A 3 ), other elements may be contained as constituent elements. In the following description, such elements will be referred to as "other constituent elements."

[0043] Examples of other constituent elements include Rb, Cs, Ti, V, F, Cl, Br, I, N, Nb, Ta, Sc, Y, La, Gd, Lu, and Bi, and one or more selected from these may be contained.

[0044] However, the content of other constituent elements in the inorganic pigment of the present invention (when two or more kinds of other constituent elements are contained, the sum of the contents of these elements) is preferably 3% by mass or less, more preferably 1% by mass or less, and even more preferably 0.5% by mass or less.

[0045] In particular, it is preferable that the inorganic pigment of the present invention does not contain cobalt or chromium as other constituent elements.

[0046] The inorganic pigment of the present invention preferably satisfies the following conditions regarding chromaticity. That is, the inorganic pigment of the present invention has a color value of L of the color scale CIE1976 specified in JIS Z8518. * a * b *In the chromaticity coordinates specified in the color system, L * The brightness is preferably 45.0 or more and 90.0 or less, more preferably 48.0 or more and 85.0 or less, and even more preferably 50.0 or more and 80.0 or less.

[0047] Furthermore, the inorganic pigment of the present invention has a color value of L of the color scale CIE1976 specified in JIS Z8518. * a * b * In the chromaticity coordinates specified in the color system, a * is preferably −25.0 or more and −10.0 or less, more preferably −24.0 or more and −15.0 or less, and even more preferably −23.5 or more and −20.0 or less.

[0048] Furthermore, the inorganic pigment of the present invention has a color value of L of the color scale CIE1976 specified in JIS Z8518. * a * b * In the chromaticity coordinates specified in the color system, b * is preferably −30.0 or more and −5.0 or less, more preferably −20.0 or more and −10.0 or less, and even more preferably −15.00 or more and −12.0 or less.

[0049] Furthermore, the inorganic pigment of the present invention has a color value of L of the color scale CIE1976 specified in JIS Z8518. * a * b * In the chromaticity coordinates specified in the color system, C * (Saturation, (a *2 +b *2 ) 1 / 2 ) is preferably 15.0 or more, more preferably 20.0 or more, and even more preferably 23.0 or more.

[0050] By satisfying the above conditions, a more suitable color tone, more specifically, a vivid, deep green color, can be exhibited.

[0051] The inorganic pigment of the present invention has excellent thermal stability, and specifically, it is preferable that the following conditions are satisfied.

[0052] That is, when the inorganic pigment of the present invention is heated at 600° C. for 1 hour, the color difference (ΔE) is preferably 10.00 or less, and more preferably 7.00 or less.

[0053] As a result, the inorganic pigment of the present invention can more suitably maintain its excellent color tone even after heat treatment, particularly at high temperatures, such as when coloring pottery.

[0054] Here, the color difference (ΔE) is the difference between the L chromaticity coordinates of the inorganic pigment before and after the heat treatment under the above conditions. * , a * and b * The difference between the values ​​of ΔL * , Δa * and Δb * When ΔE={(ΔL * ) 2 +(Δb * ) 2 +(Δa * ) 2} 1 / 2

[0055] The inorganic pigment of the present invention has excellent moisture resistance, and specifically, it is preferable that the pigment satisfies the following conditions.

[0056] That is, when the inorganic pigment of the present invention is left for 24 hours in an environment at a temperature of 25° C. and a relative humidity of 80%, the color difference (ΔE) is preferably 7.00 or less, and more preferably 5.00 or less.

[0057] This allows the inorganic pigment of the present invention to more suitably maintain excellent color tone even in a high humidity environment.

[0058] The inorganic pigment of the present invention has excellent acid resistance, and specifically, it is preferable that the pigment satisfies the following conditions.

[0059] That is, when the inorganic pigment of the present invention is stirred for 30 minutes in a solution of pH 3 at a temperature of 25° C., the color difference (ΔE) is preferably 10.00 or less, and more preferably 7.00 or less.

[0060] This allows the inorganic pigment of the present invention to more suitably maintain excellent color tone even in an acidic environment. As the solution of pH 3, for example, an aqueous solution of acetic acid can be used.

[0061] The inorganic pigment of the present invention has excellent resistance to bases, and specifically, it is preferable that the pigment satisfies the following conditions.

[0062] That is, when the inorganic pigment of the present invention is stirred for 30 minutes in a solution of pH 11 at a temperature of 25° C., the color difference (ΔE) is preferably 10.00 or less, and more preferably 7.00 or less.

[0063] This allows the inorganic pigment of the present invention to more suitably maintain excellent color tone even in a basic environment. As the solution having a pH of 11, for example, an aqueous ammonia solution can be used.

[0064] The inorganic pigment of the present invention may be in any form, but is preferably in the form of a powder containing a plurality of particles.

[0065] This allows the composition to be suitably used in the preparation of compositions containing inorganic pigments, such as various paints and inks.

[0066] Examples of the shape of the particles include substantially spherical, polyhedral, spindle-shaped, irregular, plate-like, and needle-like shapes. However, from the viewpoints of the fluidity of the inorganic pigment itself, the fluidity when it is made into compositions such as various paints and inks, and the stability of the hue as an inorganic pigment, shapes other than plate-like and needle-like are preferred.

[0067] When the inorganic pigment of the present invention contains a plurality of particles, the average particle size is preferably from 0.03 μm to 100 μm, and more preferably from 0.05 μm to 50 μm.

[0068] This makes it possible to make the color of the inorganic pigment itself more suitable, and also to improve the dispersion stability of the inorganic pigment when the inorganic pigment is applied to compositions containing the inorganic pigment, such as various paints and inks.

[0069] In this specification, the average particle size refers to the average particle size on a volume basis unless otherwise specified. The average particle size can be determined, for example, by measurement using a Microtrac UPA (manufactured by Nikkiso Co., Ltd.).

[0070] The inorganic pigment of the present invention may contain the component represented by the above formula, and may also contain other components in addition to the component represented by the above formula, such as unreacted raw materials, decomposition products of the component represented by the above formula, and unavoidable impurities.

[0071] When other components are contained, the content of the other components is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less, based on the total amount of the inorganic pigment of the present invention.

[0072] The inorganic pigment of the present invention exhibits a vivid, deep green color and can therefore be used to color a variety of materials.

[0073] The inorganic pigment of the present invention can also be suitably used as a raw material for various paints and inks.

[0074] The inorganic pigment of the present invention may be mixed with various resins or glasses and used to produce molded articles.

[0075] The inorganic pigment of the present invention may be used in combination with other coloring materials. For example, a color image may be formed by applying the inorganic pigment of the present invention together with coloring materials of other colors in a predetermined pattern to a substrate, or the inorganic pigment of the present invention may be mixed with other coloring materials to express a color tone different from the color tone of the inorganic pigment of the present invention alone.

[0076] In particular, the inorganic pigment of the present invention has excellent heat resistance (high-temperature stability) and color durability, and can favorably maintain a predetermined color tone for a long period of time. Therefore, the inorganic pigment of the present invention is particularly suitable when used in a heated environment, for example, for coloring pottery, ceramics, and other pottery colorants.

[0077] Furthermore, the inorganic pigment of the present invention is resistant to fading and can maintain a vivid, deep color tone for a long period of time, and therefore can be suitably used as a colorant for various inks, for example, inkjet inks.

[0078] [2] Manufacturing method of inorganic pigments Next, the method for producing the inorganic pigment of the present invention will be described. FIG. 2 is a flow chart showing an example of the steps of the method for producing an inorganic pigment of the present invention.

[0079] The inorganic pigment of the present invention can be prepared by, for example, using a Na source material, a Cu source material, and a Ge source material as raw materials, and further, if necessary, A 1 Source substance, A 2 Source material and A 3 The material can be suitably produced by a method including a mixing step of mixing at least one of the source materials to obtain a mixture, and a heat treatment step of heat treating the mixture.

[0080] This allows for the suitable production of an inorganic pigment that exhibits a blue-green color, is low in toxicity, and has excellent color development and stability. In particular, the inorganic pigment produced can be made excellent in heat resistance, water resistance, moisture resistance, acid resistance, base resistance, etc. Furthermore, since the inorganic pigment described above is composed of elements that can be stably supplied, stable production is possible. In addition, the additive element A1 , A 2 , A 3 By adjusting the type and substitution ratio of the inorganic pigment, the color tone and the like of the inorganic pigment can be suitably adjusted.

[0081] Each step will be described below. [2-1]Mixing process In the mixing step, a Na source material, a Cu source material, a Ge source material, and, if necessary, A 1 Source substance, A 2 Source material and A 3 At least one of the source materials is mixed to obtain a feed mixture.

[0082] The timing of mixing each component in the mixing step is not particularly limited. For example, all raw materials may be mixed at once, or specific types of raw material components may be mixed and then other raw material components may be mixed. This step can be carried out using, for example, a mortar, a ball mill, etc. may be further mixed.

[0083] Na source, Cu source, Ge source, A 1 Source, A 2 Source and A 3 The sources are Na, Cu, Ge, and A, respectively. 1 , A 2 and A 3 Any compound containing these can be used, and for example, oxides, carbonates, hydroxides, etc. of these can be preferably used, with carbonates and oxides being particularly preferred. This allows the reaction in the subsequent heat treatment step to proceed favorably.

[0084] These compounds may be used in the form of hydrates. In the following description of preferred compounds, the water of hydration of the hydrates will be omitted.

[0085] Examples of the Na source include sodium oxide, sodium carbonate, sodium hydrogen carbonate, and sodium hydroxide, with sodium carbonate being particularly preferred.

[0086] Examples of Cu sources include copper oxide, copper carbonate, copper hydroxide, etc., with copper oxide (CuO) being particularly preferred.

[0087] Examples of Ge sources include germanium oxide, germanium carbonate, and germanium hydroxide, with germanium oxide (GeO2) being particularly preferred.

[0088] A 1 Sources include, for example, lithium oxide, potassium oxide, lithium carbonate, lithium bicarbonate, potassium carbonate, potassium bicarbonate, lithium hydroxide, potassium hydroxide, and the like.

[0089] A 2 Examples of sources include nickel oxide, zinc oxide, magnesium oxide, manganese oxide, iron oxide, nickel carbonate, zinc carbonate, magnesium carbonate, manganese carbonate, iron carbonate, nickel hydroxide, zinc hydroxide, magnesium hydroxide, manganese hydroxide, iron hydroxide, and the like.

[0090] A 3 Examples of the source include nickel oxide, manganese oxide, iron oxide, tin oxide, silicon oxide, phosphorus oxide, aluminum oxide, gallium oxide, nickel carbonate, manganese carbonate, iron carbonate, tin carbonate, aluminum carbonate, gallium carbonate, nickel hydroxide, manganese hydroxide, iron hydroxide, tin hydroxide, silicic acid, aluminum hydroxide, and gallium hydroxide.

[0091] The raw materials for the inorganic pigment of the present invention may be in any shape, but are preferably in particulate form, which allows multiple types of raw materials to be suitably mixed and more effectively prevents unintended compositional variations and unintended remaining unreacted raw materials in the produced inorganic pigment.

[0092] The average particle size of the raw material is preferably 0.1 μm or more and 50 μm or less. This makes it easier to handle the raw materials and more effectively prevents the problems described above from occurring. In addition, the solid-phase reaction in the heat treatment step can be more favorably promoted, thereby improving the productivity of the inorganic pigment.

[0093] In the mixing step, the Na source, Cu source, and Ge source as described above are mixed, and further, if necessary, A 1 Source, A 2 Source and A 3 At least one of the sources is mixed in a predetermined ratio, for example, a stoichiometric ratio, to form a raw material mixture.

[0094] The raw material mixture may be mixed by either dry mixing or wet mixing, but wet mixing is preferred from the viewpoint of more uniform mixing of the raw materials. Furthermore, wet mixing makes it easier for the raw material powder to clump together, and can more effectively prevent scattering as powder.

[0095] The solvent used in the wet mixing may be, for example, an organic solvent such as methanol, acetone, benzene, or carbon tetrachloride.

[0096] The mixing method may include, for example, a stationary mixer such as a stirrer, a spiral mixer, a ribbon mixer, or a fluidizing mixer; a rotary mixer such as a cylindrical mixer or a twin cylindrical mixer; a wet grinder such as a sand mill, a ball mill, a bead mill, a colloid mill, or a sand grinder mill; a shaker such as a paint shaker; or a disperser such as an ultrasonic disperser.

[0097] The raw material mixture obtained as described above may be formed into a predetermined shape prior to the heat treatment step described below. The raw material mixture can be molded, for example, by pressure molding.

[0098] When the raw material mixture is molded, the shape is not particularly limited, but it can be, for example, pelletized. This results in a dense fired product in the heat treatment step described below, and an inorganic pigment with excellent properties can be obtained. Furthermore, molding the mixture into pelletized form and firing it also increases raw material efficiency. The molding pressure during pressure molding is preferably 50 MPa or more and 200 MPa or less.

[0099] [2-2] Heat treatment process In the heat treatment step, the raw material mixture is subjected to heat treatment.

[0100] The heat treatment method in the heat treatment step is not particularly limited as long as it can heat the raw material mixture, and various devices and methods can be used.

[0101] The heat treatment step is preferably carried out at a temperature of 700° C. or higher and 1500° C. or lower for 5 hours or longer and 120 hours or shorter.

[0102] This allows the reaction in the heat treatment step to proceed more smoothly. In addition, the inorganic pigment can be synthesized by heat treatment at a relatively low temperature, which does not require special equipment or the like and also leads to a reduction in production costs.

[0103] As described above, the heating temperature in the heat treatment step is preferably 700° C. to 1500° C., more preferably 750° C. to 1300° C., and even more preferably 800° C. to 1000° C. In addition, the heating time in the heat treatment step is preferably 5 hours to 120 hours, as described above, more preferably 20 hours to 100 hours, and even more preferably 40 hours to 85 hours. This allows the reaction in the heat treatment step to proceed more favorably.

[0104] The atmosphere in the heat treatment step is not particularly limited, and the heat treatment step may be carried out, for example, in the air or in an inert gas atmosphere.

[0105] Examples of the inert gas include argon gas, helium gas, and nitrogen gas.

[0106] The heat treatment step as described above may be carried out in one stage, or in two or more stages under different conditions.

[0107] For example, when the heat treatment step is divided into a first stage and a second stage, the atmosphere may be different between the first stage and the second stage.

[0108] For example, when the heat treatment step is carried out in the first and second stages as described above, the first stage may be carried out in the air, and the second stage may be carried out in a mixed gas atmosphere of an inert gas and hydrogen gas.

[0109] This allows the reactions in the first and second stages of the heat treatment step to proceed more smoothly.

[0110] The solid reactants may also be milled between the first and second stages. This allows the reaction in the second stage of the heat treatment step to proceed more favorably, for example.

[0111] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these.

[0112] For example, the inorganic pigment of the present invention is not limited to those produced by the above-mentioned methods, and may be produced by any method. [Example]

[0113] The present invention will be described in detail below based on specific examples, but the present invention is not limited to these examples.

[0114] In the following description, treatments for which no particular atmospheric or temperature conditions are specified were carried out in the air at 25°C. Furthermore, for various measurement conditions for which no particular temperature conditions are specified, the values ​​are those measured in the air at 25°C.

[0115] [3] Manufacturing of inorganic pigments Example 1 As raw materials, Na2CO3 powder, CuO powder, and GeO2 powder were prepared, and these raw materials were weighed out so that the molar ratio of Na, Cu, and Ge was 2.00:3.00:4.00.

[0116] Next, the powder raw materials were mixed in an agate mortar using acetone as a solvent.

[0117] Thereafter, the mixture obtained by wet mixing was formed into pellets at a pressure of 180 MPa.

[0118] The pellet-like mixture was then placed on a Pt plate, placed in an alumina boat, and fired in air at 800°C for 100 hours to obtain a solid material.

[0119] The solid material was then allowed to cool to room temperature, crushed, and sieved to obtain Na2Cu3Ge4O 12 That is, a powdered inorganic pigment having the composition represented by the above formula (1) (where x, y, and z in formula (1) are all 0.00) was obtained.

[0120] Examples 2 to 10 Inorganic pigments were produced in the same manner as in Example 1, except that the heating time for the pellet-shaped mixture was changed as shown in Table 1.

[0121] (Examples 11 to 14) An inorganic pigment was produced in the same manner as in Example 1, except that, as raw materials, in addition to Na2CO3 powder, CuO powder, and GeO2 powder, Li2CO3 powder was further used, and the mixing ratio of these was adjusted so that the composition of the resulting inorganic pigment would be as shown in Table 1.

[0122] (Examples 15 to 17) Inorganic pigments were produced in the same manner as in Example 14, except that the heating time for the pellet-shaped mixture was changed as shown in Table 1.

[0123] (Examples 18 to 21) An inorganic pigment was produced in the same manner as in Example 1, except that, as raw materials, in addition to Na2CO3 powder, CuO powder, and GeO2 powder, K2CO3 powder was further used, and the mixing ratio of these was adjusted so that the composition of the resulting inorganic pigment would be as shown in Table 1.

[0124] Example 22 An inorganic pigment was produced in the same manner as in Example 1, except that MgO powder was used as raw materials in addition to Na2CO3 powder, CuO powder, and GeO2 powder, and the mixing ratio of these was adjusted so that the composition of the resulting inorganic pigment would be as shown in Table 2.

[0125] Examples 23 to 25 An inorganic pigment was produced in the same manner as in Example 1, except that, as raw materials, in addition to Na2CO3 powder, CuO powder, and GeO2 powder, NiO powder was further used, and the mixing ratio of these was adjusted so that the composition of the resulting inorganic pigment would be as shown in Table 2.

[0126] (Examples 26 to 28) An inorganic pigment was produced in the same manner as in Example 1, except that FeO powder was used as raw materials in addition to Na2CO3 powder, CuO powder, and GeO2 powder, and the mixing ratio of these was adjusted so that the composition of the resulting inorganic pigment would be as shown in Table 2.

[0127] Examples 29 to 32 An inorganic pigment was produced in the same manner as in Example 1, except that MnO powder was used as raw materials in addition to Na2CO3 powder, CuO powder, and GeO2 powder, and the mixing ratio of these was adjusted so that the composition of the resulting inorganic pigment would be as shown in Table 2.

[0128] Example 33 An inorganic pigment was produced in the same manner as in Example 1, except that ZnO powder was used as raw materials in addition to Na2CO3 powder, CuO powder, and GeO2 powder, and the mixing ratio of these was adjusted so that the composition of the resulting inorganic pigment would be as shown in Table 2.

[0129] Examples 34 to 42 Inorganic pigments were produced in the same manner as in Example 33, except that the heating time for the pellet-shaped mixture was changed as shown in Table 2.

[0130] (Examples 43 to 46) An inorganic pigment was produced in the same manner as in Example 33, except that the mixing ratio of Na2CO3 powder, CuO powder, GeO2 powder, and ZnO powder was changed so that the composition of the resulting inorganic pigment would be as shown in Table 3.

[0131] Example 47 An inorganic pigment was produced in the same manner as in Example 1, except that, as raw materials, in addition to Na2CO3 powder, CuO powder, and GeO2 powder, NiO powder was further used, and the mixing ratio of these was adjusted so that the composition of the resulting inorganic pigment would be as shown in Table 3.

[0132] Example 48 An inorganic pigment was produced in the same manner as in Example 1, except that MnO powder was used as raw materials in addition to Na2CO3 powder, CuO powder, and GeO2 powder, and the mixing ratio of these was adjusted so that the composition of the resulting inorganic pigment would be as shown in Table 3.

[0133] Example 49 An inorganic pigment was produced in the same manner as in Example 1, except that FeO powder was used as raw materials in addition to Na2CO3 powder, CuO powder, and GeO2 powder, and the mixing ratio of these was adjusted so that the composition of the resulting inorganic pigment would be as shown in Table 3.

[0134] Example 50 An inorganic pigment was produced in the same manner as in Example 1, except that NH4H2PO4 powder was used as raw materials in addition to Na2CO3 powder, CuO powder, and GeO2 powder, and the mixing ratio of these was adjusted so that the composition of the resulting inorganic pigment would be as shown in Table 3.

[0135] Example 51 An inorganic pigment was produced in the same manner as in Example 1, except that, as raw materials, in addition to Na2CO3 powder, CuO powder, and GeO2 powder, Al2O3 powder was further used, and the mixing ratio of these was adjusted so that the composition of the resulting inorganic pigment would be as shown in Table 3.

[0136] Example 52 An inorganic pigment was produced in the same manner as in Example 1, except that GaO powder was used as raw materials in addition to NaCO powder, CuO powder, and GeO powder, and the mixing ratio of these was adjusted so that the composition of the resulting inorganic pigment would be as shown in Table 3.

[0137] (Examples 53 to 57) An inorganic pigment was produced in the same manner as in Example 1, except that, as raw materials, in addition to Na2CO3 powder, CuO powder, and GeO2 powder, SnO2 powder was further used, and the mixing ratio of these was adjusted so that the composition of the resulting inorganic pigment would be as shown in Table 3.

[0138] (Examples 58 to 61) An inorganic pigment was produced in the same manner as in Example 1, except that SiO powder was used as raw materials in addition to NaCO powder, CuO powder, and GeO powder, and the mixing ratio of these was adjusted so that the composition of the resulting inorganic pigment would be as shown in Table 3.

[0139] (Examples 62 to 70) Inorganic pigments were produced in the same manner as in Example 60, except that the heating time for the pellet-shaped mixture was changed as shown in Tables 3 and 4.

[0140] (Comparative Example 1) An inorganic pigment was produced in the same manner as in Example 22, except that the mixing ratio of the raw materials was adjusted so that the composition of the resulting inorganic pigment would be as shown in Table 4.

[0141] (Comparative Examples 2 and 3) An inorganic pigment was produced in the same manner as in Example 23, except that the mixing ratio of the raw materials was adjusted so that the composition of the resulting inorganic pigment would be as shown in Table 4.

[0142] Comparative Example 4 An inorganic pigment was produced in the same manner as in Example 26, except that the mixing ratio of the raw materials was adjusted so that the composition of the resulting inorganic pigment would be as shown in Table 4.

[0143] The raw materials used in each of the examples and comparative examples were all powders with an average particle size of 0.1 μm or more and 50 μm or less.

[0144] FIG. 3 shows an SEM photograph of the inorganic pigment of Example 1, FIG. 4 shows SEM photographs of the inorganic pigments of Examples 62 to 64, FIG. 5 shows SEM photographs of the inorganic pigments of Examples 65 to 67, and FIG. 6 shows SEM photographs of the inorganic pigments of Examples 68 to 70.

[0145] [4] Evaluation The inorganic pigments of the Examples and Comparative Examples obtained as described above were subjected to the following measurements and tests.

[0146] [4-1] Powder X-ray diffraction measurement The X-ray diffraction patterns (XRD patterns) of the inorganic pigments of the above-mentioned Examples and Comparative Examples were measured using a powder X-ray diffractometer (XRD: X-ray diffraction).

[0147] Powder X-ray diffraction measurements were carried out using a powder X-ray diffractometer (D2 Phaser, manufactured by Bruker) under the conditions shown below.

[0148] X-ray:Cu / 40kV / 25mA Divergence slit: 1° Scattering slit: 1° Receiving slit: 0.15 nm Detector: Scintillation counter Scan speed: 0.02° / sec Scanning range: 10°~50°

[0149] The X-ray diffraction patterns for the inorganic pigments of Examples 1 to 10 are shown in FIG. 7 , the X-ray diffraction patterns for the inorganic pigments of Examples 11 to 14 are shown in FIG. 8 , the X-ray diffraction patterns for the inorganic pigments of Examples 1 and 14 to 17 are shown in FIG. 9 , the X-ray diffraction patterns for the inorganic pigments of Examples 18 to 21 are shown in FIG. 10 , the X-ray diffraction patterns for the inorganic pigments of Example 22 and Comparative Example 1 are shown in FIG. 11 , the X-ray diffraction patterns for the inorganic pigments of Examples 23 to 25 and Comparative Examples 2 and 3 are shown in FIG. 12 , the X-ray diffraction patterns for the inorganic pigments of Examples 26 to 28 and Comparative Example 4 are shown in FIG. 13 , and the X-ray diffraction patterns for the inorganic pigments of Examples 29 to 32 are shown in FIG. 14 is shown, the X-ray diffraction pattern for the inorganic pigment of Example 33 is shown in FIG. 15, the X-ray diffraction pattern for the inorganic pigments of Examples 1 and 33 to 42 is shown in FIG. 16, the X-ray diffraction pattern for the inorganic pigments of Examples 43 to 46 is shown in FIG. 17, the X-ray diffraction pattern for the inorganic pigments of Examples 47 to 52, 56, and 60 is shown in FIG. 18, the X-ray diffraction pattern for the inorganic pigments of Examples 53 to 55 and 57 is shown in FIG. 19, the X-ray diffraction pattern for the inorganic pigments of Examples 58 to 61 is shown in FIG. 20, and the X-ray diffraction pattern for the inorganic pigments of Examples 1, 60, and 62 to 70 is shown in FIG. 21.

[0150] From these figures, it can be seen that in each of the above examples, a peak exists between 2θ of 24.0 and 24.5°. This peak is due to Na2Cu3Ge4O 12 This corresponds to the phase.

[0151] Also, A 1 , A 2 , A 3 In the example inorganic pigment containing Na2Cu3Ge4O 12 A slight peak shift is observed compared to

[0152] These results indicate that A 1 by Na2Cu3Ge4O 12 Na in the host lattice + Partial site replacement, A 2 by Na2Cu3Ge4O 12 Cu in the host lattice 2+ Partial site replacement, A 3 by Na2Cu3Ge4O 12 Ge host lattice 4+ This indicates that some substitutions of the site have occurred.

[0153] [4-2] Diffuse reflectance spectrum measurement The inorganic pigments of the above-mentioned Examples and Comparative Examples were subjected to measurement of the diffuse reflectance spectrum using an ultraviolet-visible spectrophotometer (UV-vis spectrometer).

[0154] For the measurement, an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, V-700) equipped with an integrating sphere unit (manufactured by JASCO Corporation, ISV-922) was used.

[0155] For the baseline measurement, molded barium sulfate was used. 30 mg of inorganic pigment was then packed into the window (φ5 mm) of a trace powder cell (PSH-003, manufactured by JASCO Corporation) to achieve a filling rate of 50% or more. The spectral reflectance of diffuse reflected light, including specular reflected light, was measured in the wavelength range of 300 nm to 800 nm.

[0156] The diffuse reflectance spectra, measured by UV-visible spectroscopy, for the inorganic pigments of Examples 1 to 10 are shown in Figure 22, the diffuse reflectance spectra, measured by UV-visible spectroscopy, for the inorganic pigments of Examples 14 to 17 are shown in Figure 23, the diffuse reflectance spectra, measured by UV-visible spectroscopy, for the inorganic pigments of Examples 33 to 42 are shown in Figure 24, and the diffuse reflectance spectra, measured by UV-visible spectroscopy, for the inorganic pigments of Examples 60 and 62 to 70 are shown in Figure 25. Larger values ​​indicate stronger reflection, and smaller values ​​indicate stronger absorption.

[0157] Among these, the high-energy broad band with a peak around 370 nm is thought to be due to absorption due to charge transfer transition from the ligand oxygen to the central metal copper. In addition, the broad absorption band above 620 nm is due to Cu 2+ dd transition ( 2 B 1g → 2 B 2g , 2 B 1g → 2 E g ) is thought to be derived from

[0158] [4-3] Chromaticity evaluation The inorganic pigments of the above examples and comparative examples were measured using the L color scale of CIE1976 specified in JIS Z8518. * a * b * In the chromaticity coordinates specified in the color system, L * (lightness), a * (positive direction: red, negative direction: green), b * (positive direction: yellow, negative direction: blue)

[0159] The chromaticity coordinates were measured using a colorimeter (CR-300, manufactured by Konica Minolta) on samples prepared by compression molding and pelletizing each inorganic pigment.

[0160] The inorganic pigments produced in the above examples and comparative examples were * a * b *The values ​​of L and chroma C are shown in Tables 1 to 4. In addition, as Comparative Example 5, the L of V-ZrSiO4, which is a conventionally used inorganic pigment, was * a * b * The values ​​of color and chroma C are also shown.

[0161] [Table 1]

[0162] [Table 2]

[0163] [Table 3]

[0164] [Table 4]

[0165] As is clear from Tables 1 to 4, the chromaticity coordinates of the pigment depend on the composition, and excellent results were obtained in all of the above Examples. In contrast, a blue-green color tone could not be obtained in Comparative Examples 1 to 4.

[0166] The comparative example, V-ZrSiO4, a conventionally used inorganic pigment, also exhibited a vivid blue-green color, but because it is difficult to dissolve vanadium in the basic structure of ZrSiO4, this material requires the use of alkali metal and alkaline earth metal fluorides, as well as alkali silicofluorides, as mineralizers. Therefore, the synthesis process may generate toxic gases such as hydrogen fluoride, which has a significant impact on the environment.

[0167] [4-4] Heat resistance test The inorganic pigments produced in the above examples were subjected to heat treatment and heat resistance tests as follows.

[0168] First, a plurality of alumina boats were prepared, and 0.3 g of the inorganic pigment of each example was placed in each of the boats. Thereafter, the sample was subjected to a heat treatment in air at 600°C for 10 hours.

[0169] [4-4-1] Evaluation of X-ray diffraction patterns For the sample that had been subjected to the heat treatment as described above, the X-ray diffraction pattern (XRD pattern) was measured under the same conditions as above.

[0170] The XRD patterns are all triclinic Na2Cu3Ge4O 12 The results almost coincided with a single phase structure. This indicates that the inorganic pigments of the above examples did not undergo phase transition (change) or decomposition of the crystalline structure even when heated at high temperatures. In other words, it can be seen that the inorganic pigments of the above examples are stable even at high temperatures.

[0171] [4-4-2] Evaluation of color difference In addition, for the samples that had been subjected to the above heat treatment, the L * a * b * The change in value and the color difference (ΔE) were evaluated.

[0172] As a result, it was confirmed that the inorganic pigments of the above examples all had a sufficiently small color difference (ΔE) before and after heating, and had excellent thermal stability.

[0173] [4-5] Moisture resistance test The inorganic pigments produced in the above examples were treated in high humidity (high humidity treatment) and subjected to a humidity resistance test as follows.

[0174] First, a plurality of alumina boats were prepared, and 0.3 g of the inorganic pigment of each example was placed in each of the boats. Thereafter, the sample was left to stand for 24 hours in an environmental test chamber at a temperature of 25°C and a humidity of 80%.

[0175] [4-5-1] Evaluation of X-ray diffraction patterns The X-ray diffraction pattern (XRD pattern) of the sample subjected to the high humidity treatment was measured under the same conditions as above.

[0176] The XRD patterns are all triclinic Na2Cu3Ge4O 12 The results almost coincided with a single phase structure. This indicates that the inorganic pigments of the above examples did not undergo phase transition (change) or decomposition of the crystalline structure even when subjected to high-humidity treatment. In other words, it can be seen that the inorganic pigments of the above examples are stable even in a high-humidity atmosphere.

[0177] [4-5-2] Evaluation of color difference In addition, for the sample that had been subjected to high humidity processing, the L * a * b * The change in value and the color difference (ΔE) were evaluated.

[0178] As a result, it was confirmed that the inorganic pigments of the above examples all had a sufficiently small color difference (ΔE) before and after heating, and had excellent thermal stability.

[0179] [4-6] Acid resistance test The inorganic pigments produced in the above examples were subjected to an acid resistance test as follows.

[0180] First, a plurality of beakers were prepared, and 0.3 g of the inorganic pigment of each Example was placed in each of the beakers.

[0181] Next, 30 mL of an aqueous acetic acid solution of pH 3 was added to each of these beakers and stirred at 300 rpm for 30 minutes. The temperature of the aqueous acetic acid solution was 25°C.

[0182] Thereafter, the liquid in the beaker was suction filtered, and the recovered solid inorganic pigment was dried at 50°C for 24 hours.

[0183] [4-6-1] Evaluation of X-ray diffraction patterns The X-ray diffraction pattern (XRD pattern) of the sample subjected to the acid treatment as described above was measured under the same conditions as above.

[0184] The XRD patterns are all triclinic Na2Cu3Ge4O 12 The results almost coincided with a single phase structure. This indicates that the inorganic pigments of the above examples did not undergo phase transition (change) or decomposition of the crystalline structure even when acid-treated. In other words, it can be seen that the inorganic pigments of the above examples are stable against acids.

[0185] [4-6-2] Evaluation of color difference In addition, for the sample that had been subjected to the acid treatment described above, the L * a * b * The change in value and the color difference (ΔE) were evaluated.

[0186] As a result, it was confirmed that the inorganic pigments of the above examples all had a sufficiently small color difference (ΔE) before and after the acid treatment, and had excellent acid resistance.

[0187] [4-7] Base resistance test The inorganic pigments produced in the above examples were subjected to a base resistance test as follows.

[0188] First, a plurality of beakers were prepared, and 0.3 g of the inorganic pigment of each Example was placed in each of the beakers.

[0189] Next, 30 mL of an aqueous ammonia solution with a pH of 11 was added to each of these beakers and stirred at 300 rpm for 30 minutes. The temperature of the aqueous ammonia solution was set to 25°C.

[0190] Thereafter, the liquid in the beaker was suction filtered, and the recovered solid inorganic pigment was dried at 50°C for 24 hours.

[0191] [4-7-1] Evaluation of X-ray diffraction patterns The X-ray diffraction pattern (XRD pattern) of the sample subjected to the above-mentioned base treatment was measured under the same conditions as above.

[0192] The XRD patterns are all triclinic Na2Cu3Ge4O 12 The results almost coincided with a single phase structure. This indicates that the inorganic pigments of the above examples did not undergo phase transition (change) or decomposition of the crystalline structure even when treated with a base. In other words, it can be seen that the inorganic pigments of the above examples are stable against bases.

[0193] [4-7-2] Evaluation of color difference In addition, for the sample subjected to the above-mentioned base treatment, the L * a * b * The change in value and the color difference (ΔE) were evaluated.

[0194] As a result, it was confirmed that the inorganic pigments of the above examples all had a sufficiently small color difference (ΔE) before and after the base treatment, and had excellent base resistance. The results of the above tests for Examples 1, 14, 21, 23, 26, 29, 33, 47 to 53, and 60 are summarized in Table 5.

[0195] [Table 5]

[0196] From the above results, it was confirmed that the inorganic pigment of the present invention exhibits a blue-green color tone with excellent color development and stability. Furthermore, the inorganic pigment of the present invention does not contain heavy metals such as cobalt and chromium, which have a high environmental impact, and is low in toxicity.

[0197] The X-ray diffraction patterns of the inorganic pigment of Example 1 after the heat resistance test, moisture resistance test, acid resistance test, and base resistance test are shown in FIG. 26 , the X-ray diffraction patterns of the inorganic pigment of Example 14 after the heat resistance test, moisture resistance test, and base resistance test are shown in FIG. 27 , the X-ray diffraction patterns of the inorganic pigment of Example 21 after the heat resistance test, moisture resistance test, acid resistance test, and base resistance test are shown in FIG. 28 , and the X-ray diffraction patterns of the inorganic pigment of Example 23 after the heat resistance test, moisture resistance test, and base resistance test are shown in FIG. 29, the X-ray diffraction pattern of the inorganic pigment of Example 26 after the heat resistance test, moisture resistance test, acid resistance test, and base resistance test is shown in FIG. 30, the X-ray diffraction pattern of the inorganic pigment of Example 29 after the heat resistance test, moisture resistance test, acid resistance test, and base resistance test is shown in FIG. 31, the X-ray diffraction pattern of the inorganic pigment of Example 33 after the heat resistance test, moisture resistance test, acid resistance test, and base resistance test is shown in FIG. 32, the X-ray diffraction pattern of the inorganic pigment of Example 47 after the heat resistance test, moisture resistance test, acid resistance test, and base resistance test is shown in FIG. FIG. 33 shows the X-ray diffraction pattern of the inorganic pigment of Example 48 after the heat resistance test, moisture resistance test, acid resistance test, and base resistance test. FIG. 34 shows the X-ray diffraction pattern of the inorganic pigment of Example 49 after the heat resistance test, moisture resistance test, acid resistance test, and base resistance test. FIG. 35 shows the X-ray diffraction pattern of the inorganic pigment of Example 50 after the heat resistance test, moisture resistance test, acid resistance test, and base resistance test. FIG. 36 shows the X-ray diffraction pattern of the inorganic pigment of Example 51 after the heat resistance test. FIG. 37 shows the X-ray diffraction patterns of the inorganic pigment of Example 52 after the heat resistance test, moisture resistance test, acid resistance test, and base resistance test. FIG. 38 shows the X-ray diffraction patterns of the inorganic pigment of Example 53 after the heat resistance test, moisture resistance test, acid resistance test, and base resistance test. FIG. 39 shows the X-ray diffraction patterns of the inorganic pigment of Example 60 after the heat resistance test, moisture resistance test, acid resistance test, and base resistance test.

[0198] In addition, inorganic pigments were produced in the same manner as in each of the above Examples, except that the molding pressure when the mixture obtained by wet mixing was press-molded was variously changed within a range of 50 MPa or more and 200 MPa or less, and the heating temperature in the heat treatment step was variously changed within a range of 700°C or more and 1500°C or less, and these were evaluated in the same manner as above, and the same results as above were obtained. [Industrial Applicability]

[0199] The inorganic pigment of the present invention is represented by the following formula (1). Na 2(1-x) A 1 2x Cu 3(1-y) A 2 3y Ge 4(1-z) A 3 4z O 12 (1) (In formula (1), A 1 is at least one selected from the group consisting of Li and K, and A 2 is at least one selected from the group consisting of Ni, Zn, Mg, Mn and Fe, and A 3 is at least one selected from the group consisting of Ni, Mn, Fe, Sn, Si, P, Al, and Ga, and satisfies the conditions 0.00≦x≦0.30, 0.00≦y≦0.30, and 0.00≦z≦0.30.

[0200] Such an inorganic pigment is a bluish-green inorganic pigment that is low in toxicity and has excellent color development and stability. Therefore, the inorganic pigment of the present invention has industrial applicability.

Claims

1. An inorganic pigment characterized by being represented by the following formula (1): Na ２（１－x） A １ ２x Cu ３(１-ｙ) A ２ ３ｙ Ge ４（１－ｚ） A ３ ４ｚ O １２ (1) (In formula (1), A １ is at least one selected from the group consisting of Li and K, and A ２ is at least one selected from the group consisting of Ni, Zn, Mg, Mn and Fe, and A ３ is at least one element selected from the group consisting of Ni, Mn, Fe, Sn, Si, P, Al, and Ga, and satisfies the conditions 0.00≦x≦0.30, 0.00≦y≦0.30, and 0.00≦z≦0.

30.

2. The inorganic pigment has a crystalline structure containing a trimeric copper unit [Cu ３ O ８ 2. The inorganic pigment according to claim 1, wherein

3. 3. The inorganic pigment according to claim 1, wherein the inorganic pigment has a triclinic unit lattice.

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