Black composite oxide particles

Abstract

The black composite oxide particles according to the present invention contain Fe, Mg, and Al as metal components, and satisfy 42 < = W1 < = 60, 4 < = W2 < = 11, and 4 < = W3 < = 11, where W1 wt% is the Fe content, W2 wt% is the Mg content, and W3 wt% is the Al content, and the half-value width of a diffraction peak based on a (311) plane representing a spinel structure in X-ray crystal structure analysis is 0.100-0.190 DEG (inclusive). And further contains from 5 ppm to 100 ppm (inclusive) of C1.

Description

Technical Field

[0001] The present invention relates to black composite oxide particles mainly suitable as black pigments for paints, printing inks, toners, rubber / plastics, and ceramics. Background Art

[0002] Black pigments used in applications such as paints, printing inks, toners, rubber / plastics, and ceramics are required to have characteristics such as blackness, coloring power, and hiding power, and be inexpensive. As inorganic black pigments, carbon black, iron oxide-based pigments represented by magnetite, and other composite oxide pigments are widely used.

[0003] Among these inorganic black pigments, a particle size of nanometer to sub-micron is generally required. Especially for carbon black, various alternative pigments have been studied due to concerns about safety.

[0004] Patent Document 1 proposes black composite oxide particles containing a composite oxide, the composite oxide containing Fe, Mg, and Al as metal components, the amount of Fe being 30 to 55% by mass, and the atomic ratio of Fe

[0009] ,

[0008] ,

[0007] , , , , , ,

[0011] , ,

[0010] / Fe 2+ being 0.8 to 10, the amount of Mg being 1 to 10% by mass, and the amount of Al being 1 to 10% by mass. Patent Document 2 proposes Mg-containing black iron oxide particles containing a composition represented by MgxFeyO(Fe2O3) 1+z (where 0.3 < x < 1, 0 < y < 0.7, x + y = 1, 0 < z < 0.5), and having an average particle size of 0.01 to 0.5 μm. Patent Document 3 proposes a composite oxide black pigment which is a composite oxide containing main component metals of copper, manganese, and aluminum, and the content ratio of each metal relative to the total of metal elements is 25 to 45 mol% for copper, 25 to 70 mol% for manganese, and 2 to 40 mol% for aluminum, and substantially does not contain chromium, cobalt, and nickel.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2003-238164

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2003-286030

[0009] Patent Document 3: Japanese Patent Application Laid-Open No. 2015-98509 Summary of the Invention

[0010] Technical Problem to be Solved by the Invention

[0011] However, the blackness and the magneticity-induced cohesiveness of the inorganic oxide pigments described in Patent Documents 1 to 3 become problems in comparison with carbon black. On the other hand, inorganic oxide pigments are likely to become high resistance in comparison with carbon black, and when used in toner, have the feature that the resistance and the charging property are easily controlled to an appropriate level, but the charging property of toner needs to be reduced in variation under high-temperature high-humidity and low-temperature low-humidity. In particular, in black toner, the amount of pigment added as a colorant is large, and thus in order to reduce the influence on the charging amount environmental variation, it is required to suppress the environmental variation of volume resistivity.

[0012] Therefore, an object of the present application is to provide a black composite oxide particle which is high in safety, excellent in blackness, low in magnetization, and small in environmental variation of volume resistivity.

[0013] Technical means for solving the technical problem

[0014] The present inventors and others have intensively studied the above problem, and as a result, have found that by containing Fe, Mg, and Al as metal components at specific contents, and by containing Cl at a specific content, and by having a half-value width indicating crystallinity within a specific range, a black composite oxide particle which is high in safety, excellent in blackness, low in magnetization, and small in environmental variation of volume resistivity can be obtained.

[0015] That is, the present application provides a black composite oxide particle which contains Fe, Mg, and Al as metal components, and when the content of Fe is set as W1 wt%, the content of Mg is set as W2 wt%, and the content of Al is set as W3 wt%, satisfies the following formula:

[0016] 42≦W1≦60,

[0017] 4≦W2≦11,

[0018] 4≦W3≦11,

[0019] the half-value width of the diffraction peak indicating the (311) plane of the spinel structure in X-ray crystal structure analysis is 0.100° or more and 0.190° or less,

[0020] and further contains 5 ppm or more and 100 ppm or less of Cl.

[0021] In the black composite oxide particle of the present application, it is preferable to satisfy the following formula:

[0022] 0.07≦W2 / W1≦0.26,

[0023] 0.07≦W3 / W1≦0.26,

[0024] 0.4≦W3 / W2≦2.3.

[0025] In the black complex oxide particles of the present application, the volume cumulative 50% particle diameter D50 is 0.05 μm or more and 0.7 μm or less, and the volume cumulative 90% particle diameter D90 is 1.0 μm or less, based on a laser diffraction scattering method,

[0026] The volume cumulative 50% particle diameter D50 and the BET specific surface area S preferably satisfy the following formula:

[0027] 1.3935 x D50 -1.144 ≦ S ≦ 3.5303 x D50 -0.974 .

[0028] In the black complex oxide particles of the present application, the blackness L value measured by a color difference meter according to JIS K5101-1991 is preferably 20 or less, the color hue a value is preferably 2.0 or less, and the color hue b value is preferably 2.0 or less.

[0029] In the black complex oxide particles of the present application, the saturation magnetization Ms under a magnetic field of 79.6 kA / m is preferably 30 Am 2 / kg or less.

[0030] In the black complex oxide particles of the present application, the common logarithm value of the volume resistivity RvH (Ωcm) under high temperature and high humidity (30°C, relative humidity 80%) is preferably 7.0 or more.

[0031] In the black complex oxide particles of the present application, the ratio of the common logarithm value of the volume resistivity RvL under low temperature and low humidity (10°C, relative humidity 20%) to the common logarithm value of the volume resistivity RvH under high temperature and high humidity (30°C, relative humidity 80%), that is, the environmental change ratio of the volume resistivity (log 10 RvL / log 10 RvH) is preferably 1.00 or more and 1.25 or less.

[0032] Effects of the Invention

[0033] The black complex oxide particles of the present application can provide a black complex oxide particle having high safety, excellent blackness, low magnetization, and less change in volume resistivity caused by the environment. DETAILED DESCRIPTION

[0034] In the present application, a combination of two or more of the preferable modes is more preferable.

[0035] The black complex oxide particles of the present application contain Fe, Mg, and Al as metal components, and when the content of Fe is set as W1 wt%, the content of Mg is set as W2 wt%, and the content of Al is set as W3 wt%, the following formula is satisfied:

[0036] 42 ≦ W1 ≦ 60,

[0037] 4≦W2≦11,

[0038] 4≦W3≦11,

[0039] The half-value width of the diffraction peak representing the (311) plane of the spinel structure in the X-ray crystal structure analysis is 0.100° or more and 0.190° or less,

[0040] Further, C1 is contained in an amount of 5 ppm or more and 100 ppm or less.

[0041] In the black complex oxide particles of the present application, the metal components as the main components are composed of Fe, Mg, and Al. Further, it is known that as oxides of each element, in the case of Fe alone, magnetite (Fe3O4) known as a black pigment is produced, but if Mg is present therein, it reacts with Fe to produce brownish magnesium ferrite (MgFe2O4) and the like, and if Al is present, it produces hercynite (FeAl2O4) and the like as an oxide having blackness. However, in the case of using three elements of Fe, Mg, and Al, since these elements exist by being solid-solved in the spinel structure, it is important to adjust to a specific ratio in the control of blackness and magnetization.

[0042] Therefore, in the black complex oxide particles of the present application, it is important that Fe, Mg, and Al are contained as metal components, and when the content of Fe is set as W1 wt%, the content of Mg is set as W2 wt%, and the content of Al is set as W3 wt%, the following formula is satisfied:

[0043] 42≦W1≦60,

[0044] 4≦W2≦11,

[0045] 4≦W3≦11.

[0046] The contents of the above Fe, Mg, and Al each represent the content with respect to the entire black complex oxide particles.

[0047] In the black complex oxide particles of the present application, if the content of Fe is less than 42 wt%, although the magnetization is low, there is a tendency that the blackness becomes low. Further, if the content of Fe exceeds 60 mass%, although the blackness is high, there is a tendency that the magnetization becomes high. Therefore, from the viewpoint of achieving a balance between the blackness and the magnetization, it is important to satisfy 42≦W1≦60. W1 is preferably 45 or more, and more preferably 47 or more. Further, W1 is preferably 57 or less, and more preferably 55 or less.

[0048] As a preferable one mode, it is preferable to satisfy 42≦W1≦57, and more preferably to satisfy 42≦W1≦55.

[0049] As a preferable one mode, it is preferable to satisfy 45≦W1≦60, more preferably to satisfy 45≦W1≦57, further preferably to satisfy 45≦W1≦55.

[0050] As a preferable one mode, it is preferable to satisfy 47≦W1≦60, more preferably to satisfy 47≦W1≦57, further preferably to satisfy 47≦W1≦55.

[0051] In the black complex oxide particles of the present application, if the content of Mg is less than 4% by weight, although the blackness is high, there is a tendency that the magnetization becomes high. In addition, if the content of Mg exceeds 11% by mass, although the magnetization is low, there is a tendency that the blackness becomes low. Therefore, from the viewpoint of achieving a balance between the blackness and the magnetization, it is important to satisfy 4≦W2≦11. W2 is preferably 5 or more, more preferably 6 or more. In addition, W2 is preferably 10 or less, more preferably 9 or less.

[0052] As a preferable one mode, it is preferable to satisfy 4≦W2≦10, more preferably to satisfy 4≦W2≦9.

[0053] As a preferable one mode, it is preferable to satisfy 5≦W2≦11, more preferably to satisfy 5≦W2≦10, further preferably to satisfy 5≦W2≦9.

[0054] As a preferable one mode, it is preferable to satisfy 6≦W2≦11, more preferably to satisfy 6≦W2≦10, further preferably to satisfy 6≦W2≦9.

[0055] In the black complex oxide particles of the present application, if the content of Al is less than 4% by weight, although the blackness is high, there is a tendency that the magnetization becomes high. In addition, if the content of Al exceeds 11% by mass, although the magnetization is low, there is a tendency that the blackness becomes low. Therefore, from the viewpoint of achieving a balance between the blackness and the magnetization, it is important to satisfy 4≦W3≦11. W3 is preferably 5 or more, more preferably 6 or more. In addition, W3 is preferably 10 or less, more preferably 9 or less.

[0056] As a preferable one mode, it is preferable to satisfy 4≦W3≦10, more preferably to satisfy 4≦W3≦9.

[0057] As a preferable one mode, it is preferable to satisfy 5≦W3≦11, more preferably to satisfy 5≦W3≦10, further preferably to satisfy 5≦W3≦9.

[0058] As a preferable one mode, it is preferable to satisfy 6≦W3≦11, more preferably to satisfy 6≦W3≦10, further preferably to satisfy 6≦W3≦9.

[0059] In the black complex oxide particles of the present application, it is further preferable to more evenly balance blackness and magnetization by adjusting the weight ratio of Mg and Al with respect to Fe and the weight ratio of Al with respect to Mg. Specifically, it is preferable to satisfy the following formulae:

[0060] 0.07≦W2 / W1≦0.26,

[0061] 0.07≦W3 / W1≦0.26,

[0062] 0.4≦W3 / W2≦2.3.

[0063] As long as it is within this range, blackness and magnetization can be more evenly balanced. W2 / W1 is more preferably 0.10 or greater and more preferably 0.20 or less. W3 / W1 is more preferably 0.10 or greater and more preferably 0.20 or less. W3 / W2 is more preferably 0.6 or greater and more preferably 2.0 or less.

[0064] As one preferable mode, it is preferable to satisfy 0.07≦W2 / W1≦0.20.

[0065] As one preferable mode, it is preferable to satisfy 0.10≦W2 / W1≦0.26 and more preferably 0.10≦W2 / W1≦0.20.

[0066] As one preferable mode, it is preferable to satisfy 0.07≦W3 / W1≦0.20.

[0067] As one preferable mode, it is preferable to satisfy 0.10≦W3 / W1≦0.26 and more preferably 0.10≦W3 / W1≦0.20.

[0068] As one preferable mode, it is preferable to satisfy 0.4≦W3 / W2≦2.0.

[0069] As one preferable mode, it is preferable to satisfy 0.6≦W3 / W2≦2.3 and more preferably 0.6≦W3 / W2≦2.0.

[0070] It is important for the black complex oxide particles of the present application to contain Cl in addition to Fe, Mg, and Al. If the content of Cl is less than 5 ppm, the environmental variation in volume resistivity under low temperature and low humidity tends to relatively increase. In addition, if the content of Cl exceeds 100 ppm, the environmental variation in volume resistivity under high temperature and high humidity tends to relatively increase. Therefore, from the viewpoint of making the environmental variation in volume resistivity more stable, it is important for the content of Cl to be 5 ppm or greater and 100 ppm or less. The content of Cl is preferably 10 ppm or greater and more preferably 20 ppm or greater. In addition, the content of Cl is preferably 80 ppm or less and more preferably 50 ppm or less.

[0071] As a preferable one, the Cl content ratio in the black complex oxide particles is preferably 5 ppm or more and 80 ppm or less, more preferably 5 ppm or more and 50 ppm or less.

[0072] As a preferable one, the Cl content ratio in the black complex oxide particles is preferably 10 ppm or more and 100 ppm or less, more preferably 10 ppm or more and 80 ppm or less, further preferably 10 ppm or more and 50 ppm or less.

[0073] As a preferable one, the Cl content ratio in the black complex oxide particles is preferably 20 ppm or more and 100 ppm or less, more preferably 20 ppm or more and 80 ppm or less, further preferably 20 ppm or more and 50 ppm or less.

[0074] In the black complex oxide particles of the present application, it is important that the half value width of the diffraction peak based on the (311) plane indicating the spinel structure in the X-ray crystal structure analysis is 0.100° or more and 0.190° or less. When the half value width is less than 0.100°, the lattice defects in the spinel structure are few, and the single spinel crystal structure is close, and thus there is a tendency to have high magnetization and low resistance. In the case where the half value width is more than 0.190°, there is a tendency to have low blackness. The half value width is more preferably 0.120° or more and 0.170° or less. Furthermore, the half value width of the diffraction peak based on the (311) plane indicating the spinel structure can be appropriately adjusted depending on the manufacturing method such as wet or dry, the composition ratio of the metal components, the firing temperature, the firing atmosphere, and the like.

[0075] As a preferable one, the half value width is preferably 0.100° or more and 0.170° or less.

[0076] As a preferable one, the half value width is preferably 0.120° or more and 0.190° or less, more preferably 0.120° or more and 0.170° or less.

[0077] In the black complex oxide particles of the present application, the volume cumulative 50% particle diameter D50 based on the laser diffraction scattering method is 0.05 μm or more and 0.7 μm or less, and the volume cumulative 90% particle diameter D90 is 1.0 μm or less,

[0078] The volume cumulative 50% particle diameter D50 and the BET specific surface area S preferably satisfy the following formula:

[0079] 1.3935 x D50 -1.144 ≦ S ≦ 3.5303 x D50 -0.974 .

[0080] In the black composite oxide particles of the present application, the particle size distribution is preferably adjusted. Specifically, the volume cumulative 50% particle diameter D50 is preferably 0.05 μm or more and 0.7 μm or less, more preferably 0.10 μm or more and 0.5 μm or less. If D50 is set to 0.05 μm or more, it is easy to obtain the desired blackness. In addition, if D50 is set to 0.7 μm or less, it is easy to disperse with respect to toner having a particle diameter of several μm, and it is easy to obtain the desired color tone and characteristics of the toner.

[0081] As a preferable mode, D50 is more preferably 0.05 μm or more and 0.5 μm or less.

[0082] As a preferable mode, D50 is more preferably 0.10 μm or more and 0.7 μm or less, more preferably 0.10 μm or more and 0.5 μm or less.

[0083] In addition, the volume cumulative 90% particle diameter D90 is preferably 1.0 μm or less, more preferably 0.7 μm or less. If D90 is set to 1.0 μm or less, it is easy to disperse with respect to toner having a particle diameter of several μm, and it is easy to obtain the desired color tone and characteristics of the toner. As to the lower limit of D90, it can be set to 0.3 μm or more, for example.

[0084] As a preferable mode, D90 is preferably 0.3 μm or more and 1.0 μm or less, more preferably 0.3 μm or more and 0.7 μm or less.

[0085] Further, the particle size distribution for calculating the above D50 and D90 can be measured by a laser diffraction scattering method.

[0086] In the black composite oxide particles of the present application, the volume cumulative 50% particle diameter D50 and the BET specific surface area S preferably satisfy the following formula:

[0087] 1.3935 x D50 -1.144 ≦ S ≦ 3.5303 x D50 -0.974 .

[0088] Generally, particles have a particle size distribution, and it is technically difficult to make the BET specific surface area smaller than the above lower limit value because the surface unevenness cannot be completely eliminated. By setting the BET specific surface area to be the above upper limit value or less, the pores are not too much with respect to the particle diameter, and it is difficult to be affected by changes in humidity and the like. In addition, in the case of use for surface treatment and the like for hydrophilization and hydrophobization, the strength is sufficient, and thus the particles are difficult to be damaged, and the non-treated portions are not easily exposed, and thus the characteristics are easily stable.

[0089] In the black composite oxide particles of the present application, when the blackness and the hue are measured by a color difference meter according to JIS K5101-1991, the L value is preferably 20 or less, the a value is preferably 2.0 or less, and the b value is preferably 2.0 or less. By satisfying the above conditions with respect to the L value, the a value, and the b value, the blackness becomes high, and the redness and the yellowness of the hue are reduced, and thus the particles are suitable as a black pigment. The L value is more preferably 19 or less, and further preferably 17 or less.

[0090] In the black composite oxide particles of the present application, in consideration of the use in a field that does not require magnetism, represented by a non-magnetic toner use, the saturation magnetization Ms under a magnetic field of 79.6 kA / m is preferably 30 Am 2 / kg or less, and more preferably 25 Am 2 / kg or less.

[0091] In the black composite oxide particles of the present application, from the viewpoint of maintaining the charging property at the time of addition to a toner, particularly, suppressing the decrease in charging at high temperature and high humidity (30°C, relative humidity 80%), the common logarithm value of the volume resistivity RvH (Ωcm) at high temperature and high humidity (30°C, relative humidity 80%) is preferably 7.0 or more, and more preferably 7.5 or more. In addition, the ratio of the common logarithm value of the volume resistivity RvL (Ωcm) at low temperature and low humidity (10°C, relative humidity 20%) to the common logarithm value of the volume resistivity RvH (Ωcm) at high temperature and high humidity (30°C, relative humidity 80%), that is, the environmental change ratio (log 10 RvL / log 10 RvH) is preferably 1.00 or more and 1.25 or less, and more preferably 1.00 or more and 1.20 or less.

[0092] The black composite oxide particles of the present application are generally produced by a dry method. For example, the particles can be produced by weighing a prescribed amount of raw material, granulating a slurry obtained by pulverizing and mixing, and then firing at 1000°C or more and 1300°C or less under an inert atmosphere or a weakly oxidizing atmosphere.

[0093] The black composite oxide particles of the present application can also be produced by a wet method. However, in comparison with the dry method, while a large number of crystal nuclei for generating spinel crystals are present, the crystals are difficult to grow and the crystallinity is low because of the reaction at a low temperature, and thus the half-value width of the diffraction peak of the (311) plane indicative of the spinel structure has a tendency to increase. Therefore, the blackness easily becomes insufficient and is also easily changed over time. In addition, because the crystals are difficult to grow, a large number of voids are present within the particles, and the BET specific surface area relative to the particle diameter easily increases. Therefore, the particles become susceptible to changes in humidity and the like, and become a cause of changes over time. While there is a method in which the particles are produced by a wet method and then subjected to calcination, because a large number of crystal nuclei are present, control of the spinelization reaction is difficult, and excessive magnetization or excessive sintering occurs, thereby increasing the hardness excessively, and it is difficult to reduce the particle diameter. Furthermore, the grains of the particles produced by the wet method are uniform, and thus in the case where a magnetic field is applied, the magnetic moments easily coincide, and thus there is a tendency to easily become highly magnetized.

[0094] As the raw material of Fe, Fe2O3is preferably used. As the raw material of Mg, one or two or more kinds of compounds selected from Mg(OH)2, MgO, and MgCO3are preferably used. As the raw material of Al, Al2O3is preferably used. As the raw material of Cl, a chlorine source such as magnesium chloride or sodium chloride can be used, but because the amount is small in comparison with Fe, Mg, and Al, it is preferable to adjust the Cl content by Cl contained as a trace component in each of the above raw materials (particularly Fe2O3). Furthermore, with respect to Fe2O3, iron sulfate or Fe2O3produced using iron sulfate as a raw material contains almost no Cl, and it is difficult to adjust the Cl content to the desired value, and thus it is preferable to use Fe2O3produced using iron chloride as a raw material. Furthermore, the Cl content can also be adjusted by the calcination temperature and the calcination time.

[0095] After these raw materials are weighed in an appropriate amount so as to become the desired elemental composition, pulverization and mixing are performed for 0.5 hours or more (preferably 1 hour or more and 20 hours or less) using a ball mill or a vibration mill or the like, water is added to the pulverized mixture, and micro-pulverization is performed using a bead mill or the like, and a slurry can be obtained. By adjusting the diameter, the composition, and the pulverization time of the beads used as a medium, the degree of pulverization can be controlled. From the viewpoint of uniformly dispersing the raw materials, it is preferable to use beads having a particle diameter of 1 mm or less as a medium. In addition, on the basis of uniformly dispersing the raw materials, it is preferable to pulverize so that the volume average particle diameter (volume cumulative 50% particle diameter D50) of the pulverized product becomes 2.5 μm or less, and more preferably so as to become 2.0 μm.

[0096] Next, a dispersant, a binder, or the like is added to the obtained slurry as necessary, and the viscosity is preferably adjusted to 2 poise or more and 4 poise or less. As the binder, polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP) can be used. Then, by spraying the slurry whose viscosity is adjusted to the above range using a spray dryer and drying it, a granulated product can be obtained.

[0097] The calcination is preferably performed by holding the obtained granulated product at a temperature of 1000°C or more and 1300°C or less for 2 hours or more and 6 hours or less in an inert atmosphere or a weakly oxidizing atmosphere. The content of Cl can also be controlled by the calcination temperature and the calcination time. Here, the inert atmosphere or the weakly oxidizing atmosphere means an atmosphere in which the oxygen concentration is 0.0 vol% or more and 0.1 vol% (1000 ppm) or less. By setting the calcination temperature to 1000°C or more, the spinelization reaction easily occurs, and thus the blackness becomes high. By setting the calcination temperature to 1300°C or less, the spinelization grain growth does not excessively proceed in a state in which the blackness is high, the hardness becomes low, and the particle size can be easily reduced by pulverization or the like. From the viewpoints of the blackness and the hardness, the calcination temperature is preferably 1100°C or more and 1250°C or less.

[0098] The obtained calcined product can be pulverized to a desired particle size using a dry-type pulverizer such as a pin mill, a hammer mill, a bead mill, or a jet mill, or a wet-type bead mill. In the case where wet-type pulverization is performed, the product is dried to obtain a granulated product. At this time, in order to prevent drying agglomeration, an agglomeration preventive agent such as a surfactant can also be used. Then, classification is performed as necessary using an air classifier or the like, and a granulated product having a desired particle size distribution can be obtained.

[0099] The black composite oxide granulated product of the present application described above is a black composite oxide granulated product which is high in safety, excellent in blackness, low in magnetization, and less in variation in volume resistivity due to the environment. Since it is high in safety and excellent in blackness, it is suitable as a black pigment for paints, printing inks, toners, rubbers, plastics, and ceramics. In addition, since the black composite oxide granulated product of the present application is low in magnetization and less in variation in volume resistivity due to the environment, it is particularly suitable as a non-magnetic toner black pigment which replaces a carbon black which is low in safety or an oxide pigment which contains an environmentally burdensome substance. A toner using the black composite oxide granulated product of the present application can reduce the influence on the natural environment and the human body, and a high-quality printed matter can be obtained.

[0100] Example

[0101] <Example 1>

[0102] Fe2O3(chlorinated iron-based raw material, Cl content: 1500 ppm) 16.09 kg, Mg(OH)2 4.64 kg, Al2O3 4.15 kg were weighed, and pulverized for 6 hours using a dry-type medium mill (vibrating mill, 1 / 8 inch diameter stainless steel beads) (until D50 became about 5 μm). After that, water was added, and further pulverized for 6 hours using a wet-type medium mill (horizontal bead mill, 1 mm diameter zirconia beads). The particle size of the slurry (primary particle size after pulverization) was measured with a Microtrack, and the result was that D50 was about 2 μm. To the obtained slurry, a dispersant was added in an appropriate amount as a binder, and PVA (10% solution) was added in an amount of 0.4% by weight with respect to the solid content, and then granulated by a spray drier.

[0103] After that, calcination was performed in a tunnel-type electric furnace at a calcination temperature of 1200°C and an oxygen concentration of 0.0% by volume for 3 hours. At this time, the temperature increase rate was set to 200°C / hour, and the cooling rate was set to 150°C / hour. The obtained calcination product was pulverized using a hammer mill (manufactured by Maekawa Sangyo), a pin mill (manufactured by Maki Sangyo), and a dynamic mill (manufactured by Nippon Seika Kogyo), and the particles of the target particle size were classified using a super micro powder classifier CNI (manufactured by Nippon Kikai Kogyo), thereby obtaining black composite oxide particles.

[0104] <Example 2>

[0105] Black composite oxide particles were obtained by the same method as in Example 1, except that Fe2O3(chlorinated iron-based raw material, Cl content: 900 ppm) was used instead of Fe2O3as the raw material in Example 1.

[0106] <Example 3>

[0107] Black composite oxide particles were obtained by the same method as in Example 1, except that Fe2O3(chlorinated iron-based raw material, Cl content: 2900 ppm) was used instead of Fe2O3as the raw material in Example 1, and the calcination temperature was changed to 1150°C.

[0108] <Examples 4 to 8>

[0109] Black composite oxide particles were obtained by the same method as in Example 1, except that the compounding ratio of Fe2O3, Mg(OH)2, and Al2O3 used as the raw material in Example 1 was appropriately changed.

[0110] <Comparative Example 1>

[0111] A black complex oxide particle was obtained by the same method as in Example 1 except that Fe203(chlorinated iron-based material, Cl content: 3600 ppm) was used instead of Fe203used as a raw material in Example 1, and the firing temperature was changed to 1150°C.

[0112] <Comparative Example 2>

[0113] A black complex oxide particle was obtained by the same method as in Example 1 except that Fe203(chlorinated iron-based material, Cl content: 900 ppm) was used instead of Fe203used as a raw material in Example 1, and the firing temperature was changed to 1300°C.

[0114] <Comparative Examples 3 to 9>

[0115] A black complex oxide particle was obtained by the same method as in Example 1 except that the compounding ratio of Fe203, Mg(OH)2, and Al203used as raw materials in Example 1 was changed appropriately. In addition, in Comparative Example 9, the oxygen concentration at the time of firing was set to 0.5 vol%.

[0116] <Comparative Example 10>

[0117] A black complex oxide particle was obtained by a wet method. Specifically, 12.5 mol / L of an aqueous sodium hydroxide solution was added to 5 L of an aqueous sodium carbonate solution of 0.15 mol / L, adjusted to have a pH of 11, and the liquid temperature was raised to 80°C and maintained at this temperature. On the other hand, a mixed sulfate aqueous solution of 2 L containing ferrous sulfate 0.75 mol / L, ferric sulfate 0.10 mol / L, magnesium sulfate 0.5 mol / L, and aluminum sulfate 0.25 mol / L was prepared, and the above-mentioned alkaline aqueous solution containing sodium carbonate was mixed and stirred while being fed over a period of 30 minutes.

[0118] After the end of the feeding, the mixing and stirring were continued for 4 hours. During the feeding and the continuation of the mixing and stirring, the initial temperature and pH of the reaction liquid were adjusted to be maintained. After the slurry containing the black complex oxide particle thus obtained was naturally cooled, it was neutralized to pH 6 using dilute sulfuric acid, and then, after a conventional washing, dehydration, and drying, the final black complex oxide particle was obtained.

[0119] The black complex oxide particles obtained in Examples 1 to 8 and Comparative Examples 1 to 10 were evaluated with respect to the following aspects. The results are shown in Table 1 (Examples 1 to 8) and Table 2 (Comparative Examples 1 to 10).

[0120] <Content of metal components in black complex oxide particle>

[0121] The content of the metal components in the black complex oxide particles was determined by chemical analysis (ICP). Specifically, first, 0.2 g of the black complex oxide particles was weighed, and a mixture in which pure water 60 ml and 1 N hydrochloric acid 20 ml and 1 N nitric acid 20 ml were added was heated to prepare an aqueous solution in which the black complex oxide particles were completely dissolved. The obtained aqueous solution was set in an ICP analysis device (ICPS-1000 IV, manufactured by Shimadzu Corporation), and the content of Fe, Mg, and Al as metal components was determined.

[0122] <Content of Cl in the raw material or the black complex oxide particles>

[0123] The content of Cl in the raw material or the black complex oxide particles was determined by combustion ion chromatography under the following conditions.

[0124] Combustion device: AQF-2100H manufactured by Mitsubishi Chemical Analytech

[0125] Sample amount: 50 mg

[0126] Combustion temperature: 1100°C

[0127] Combustion time: 10 minutes

[0128] Ar flow rate: 400 ml / min

[0129] O2 flow rate: 200 ml / min

[0130] Humidified Air flow rate: 100 ml / min

[0131] Absorption solution: eluent containing 1% hydrogen peroxide

[0132] Analysis device: IC-2010 manufactured by Tosoh Corporation

[0133] Chromatography column: TSKgel Super IC-Anion HS

[0134] (4.6 mm I.D. x 1 cm + 4.6 mm I.D. x 10 cm)

[0135] Eluent: NaHCO3 (3.8 mmol / L) + Na2CO3 (3.0 mmol / L)

[0136] Flow rate: 1.5 mL / min

[0137] Chromatography column temperature: 40°C

[0138] Injection amount: 30 μL

[0139] Measurement mode: suppression mode

[0140] Detector: CM detector

[0141] Standard sample: Kanto Chemical Co., Inc. Anion Mixed Standard Solution

[0142] <Half width of diffraction peak based on (311) plane representing spinel structure>

[0143] The half width of diffraction peak based on (311) plane as a main peak of spinel phase (°, 2Θ) was measured by powder X-ray diffraction method. The measurement conditions are shown below.

[0144] X-ray diffractometer: X'pert MPD (including high-speed detector) manufactured by PANalytical

[0145] X-ray source: Co-Kα

[0146] Tube voltage: 45 kV

[0147] Tube current: 40 mA

[0148] Scan mode: General batch

[0149] Divergence slit (°): 1 / 2

[0150] Receiving slit (mm): 5.5

[0151] Measurement interval: 0.010° / sec

[0152] Counting time (sec): 10.16 / step

[0153] Scan range (2Θ): 15-90°

[0154] <Particle size distribution>

[0155] The particle size distribution of the black composite oxide particles was measured by laser diffraction scattering method. First, 10 g of the black composite oxide particles and 80 ml of water were put in a 100-ml beaker, and 2 drops of sodium hexametaphosphate were added as a dispersant. Next, the black composite oxide particles were dispersed using an ultrasonic homogenizer (UH-150 type, manufactured by SMT). At this time, the output level of the ultrasonic homogenizer was set to 4, and dispersion was performed for 20 seconds. After that, the foam formed on the surface of the beaker was removed, and the obtained slurry was introduced into a laser diffraction type particle size distribution measuring device (SALD-7500nano, manufactured by Shimadzu Corporation) to measure it. By this measurement, the 50% diameter (volume cumulative 50% particle size D50) and the 90% diameter (volume cumulative 90% particle size D90) in the volume particle size distribution were calculated. The measurement conditions were set to pump speed 7, built-in ultrasonic irradiation time 30, and refractive index 1.70-050i.

[0156] <BET specific surface area>

[0157] The BET specific surface area of the black complex oxide particles was measured using a specific surface area measuring device (Macsorb HM model-1208, manufactured by MOUNTECH). First, about 10 g of the black complex oxide particles were placed in a wrapping paper, degassed using a vacuum drier, and the vacuum degree was confirmed to be -0.1 MPa or less. Thereafter, the black complex oxide particles were heated at 200°C for 2 hours to remove moisture adhered to the surface of the black complex oxide particles. About 0.5 to 4 g of the black complex oxide particles from which the moisture had been removed were placed in a standard sample cell for the measuring device, and accurately weighed using a precision balance. Next, the weighed black complex oxide particles were set in a measuring port of the measuring device to perform the measurement. The measurement was performed by a single point method. The measurement atmosphere was set to a temperature of 20°C and a relative humidity of 55%.

[0158] <Saturation magnetization>

[0159] The black complex oxide particles were filled into a cell having an inner diameter of 5 mm and a height of 2 mm, and set in a vibrating sample type magnetic measuring device (VSM-C7-10A, manufactured by Toei Industry), to measure the saturation magnetization of the black complex oxide particles at a load magnetic field of 79.6 kA / m.

[0160] <Volume resistivity>

[0161] First, the black complex oxide particles were filled in a fluorine resin-made cylinder having a cross-sectional area of 4 cm 2 , so as to have a height of 4 mm. Thereafter, electrodes were attached to both ends, and further, a 1-kg weight was placed thereon to measure the resistance. The measurement of the resistance was performed using a nanovoltmeter (model 2182A, manufactured by Kyushu Riken Industry), and the resistance after 60 seconds was measured at a measurement voltage of 1000 V, and the volume resistivity was calculated. In addition, the measurement environment was set to normal temperature and humidity (temperature 20°C, relative humidity 55%), high temperature and humidity (temperature 30°C, relative humidity 80%), and low temperature and humidity (temperature 10°C, relative humidity 20%), and the commonly used logarithmic values of each volume resistivity (normal temperature and humidity: RvN, high temperature and humidity: RvH, low temperature and humidity: RvL) were calculated. In addition, these values were used to calculate the environmental change ratio (log 10 RvL / log 10 RvH)

[0162] <Blackness and hue>

[0163] The measurement of the blackness and the hue of the black composite oxide particles was performed in accordance with JIS K5101-1991. Specifically, first, castor oil 1.4 cc was added to 2.0 g of the black composite oxide particles, and mixed with a Hoover mixer. To 2.0 g of the mixed sample, varnish 7.5 g was added, and further mixed, and then coated on mirror-coated paper using a 4 mil applicator and dried. Thereafter, the blackness (L value) and the hue (a value, b value) were measured using a color difference meter (color analyzer TC-1800 type, Tokyo Denshoku Manufacturing).

[0164] [Table 1]

[0165] Table 1

[0166]

[0167] [Table 2]

[0168] Table 2

[0169]

[0170] From the above results, it was found that the black composite oxide particles obtained in Examples 1 to 8 were high in safety, excellent in blackness, low in magnetization, and less in variation in volume resistivity caused by the environment.

[0171] Industrial applicability

[0172] According to the present application, it is possible to provide a black composite oxide particle which is high in safety, excellent in blackness, low in magnetization, and less in variation in volume resistivity caused by the environment.

[0173] The present application has been described in detail with reference to specific embodiments, but various changes and modifications can be made without departing from the spirit and scope of the present application, which will be apparent to those skilled in the art.

[0174] Further, the present application is based on Japanese Patent Application (Patent Application No. 2023-045378) filed on March 22, 2023, and the content thereof is incorporated herein by reference.

Claims

1. A black complex oxide particle, containing Fe, Mg, and Al as metal components, when the content of Fe is set as Wl wt%, the content of Mg is set as W2 wt%, and the content of Al is set as W3 wt%, the following formula is satisfied: 42≦W1≦60， 4≦W2≦11， 4≦W3≦11， the half-value width of a diffraction peak based on a (311) plane indicating a spinel structure in X-ray crystal structure analysis is 0.100° or more and 0.190° or less, further containing 5 ppm or more and 100 ppm or less of Cl.

2. The black complex oxide particle according to claim 1, satisfying the following formula: 0.07 ≦ W2 / W1 ≦ 0.26, 0.07 ≦ W3 / W1 ≦ 0.26, 0.4 ≦ W3 / W2 ≦ 2.

3.

3. The black complex oxide particle according to claim 1, the volume cumulative 50% particle diameter D50 based on a laser diffraction scattering method is 0.05 μm or more and 0.7 μm or less, and the volume cumulative 90% particle diameter D90 is 1.0 μm or less, the volume cumulative 50% particle diameter D50 and the BET specific surface area S satisfy the following formula: 1.3935 x D50 -1.144 ≦S≦3.5303 x D50 -0.974 .

4. The black complex oxide particle according to claim 1, when the blackness and the hue are measured by a color difference meter in accordance with JIS K5101-1991, the L value is 20 or less, the a value is 2.0 or less, and the b value is 2.0 or less.

5. The black complex oxide particle according to claim 1, The saturation magnetization Ms at a load magnetic field of 79.6 kA / m is 30 Am 2 below 0.1 g / kg.

6. The black complex oxide particle according to claim 1, the common logarithmic value of the volume resistivity RvH (Ωcm) under high temperature and high humidity at 30°C and a relative humidity of 80% is 7.0 or more.

7. The black complex oxide particle according to claim 1, The ratio of the common logarithm value of the volume resistivity RvL(Ωcm) at a low temperature and low humidity of 10°C and 20% relative humidity to the common logarithm value of the volume resistivity RvH(Ωcm) at a high temperature and high humidity of 30°C and 80% relative humidity, that is, the environmental change ratio log 10 RvL / log 10 RvH is 1.00 or greater but 1.25 or less.

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