Black composite oxide particles

Abstract

To provide a black complex oxide particle which has high safety, is excellent in blackness, and is slightly magnetized, and in which variation in volume resistivity due to environment is slight.SOLUTION: A black complex oxide particle according to the present invention contains as metal components Fe, Mg, and Al. The black complex oxide particle satisfies 42≤W1≤60, 4≤W2≤11, and 4≤W3≤11 where an Fe content is W1 wt.%, a Mg content is W2 wt.%, and an Al content is W3 wt.%. The black complex oxide particle exhibits a half-value width of a diffraction peak based on a (311) plane representing spinel structure in X-ray crystal structure analysis of 0.100° or more and 0.190° or less. The black complex oxide particle contains 5 ppm or more and 100 ppm or less of Cl.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention mainly relates to black composite oxide particles 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 properties such as blackness, coloring power, hiding power, etc. 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] In these inorganic black pigments, it is generally required to have a particle size in the nano level to submicron range. In particular, for carbon black, various alternative pigments are being studied due to concerns about safety.

[0004] Patent Document 1 proposes black composite oxide particles containing a composite oxide containing Fe, Mg, and Al as metal components, where the amount of Fe is 30 to 55% by mass and the atomic ratio of Fe 1+z , , , / Fe 2+ is 0.8 to 10, the amount of Mg is 1 to 10% by mass, and the amount of Al is 1 to 10% by mass. Patent Document 2 proposes Mg x Fe y O(Fe2O3) 1+z (however, 0.3 < x < 1, 0 < y < 0.7, x + y = 1, 0 < z < 0.5) and Mg-containing black iron oxide particles with an average particle size of 0.01 to 0.5 μm. Patent Document 3 proposes a composite oxide black pigment that is a composite oxide of main component metals containing copper, manganese, and aluminum, and the content ratio of each metal to the total of the 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.

Prior Art Documents

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-238164 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-286030 [Patent Document 3] Japanese Patent Application Laid-Open No. 2015-98509 Summary of the Invention [Problem to be solved by the invention]

[0006] However, inorganic oxide pigments such as those described in Patent Documents 1 to 3 have issues with blackness and coagulation due to magnetic force compared to carbon black. On the other hand, inorganic oxide pigments are easier to make highly resistive than carbon black, and when used in toners, they have the advantage of being easy to control the resistance and chargeability to appropriate levels. However, it is necessary to minimize the fluctuations in the chargeability of the toner under high temperature and high humidity conditions and low temperature and low humidity conditions. In particular, since black toners contain a large amount of pigment as a colorant, it is necessary to suppress environmental fluctuations in volume resistivity in order to reduce the impact of environmental fluctuations in charge amount.

[0007] Therefore, an object of the present invention is to provide black complex oxide particles that are highly safe, have excellent blackness, low magnetization, and exhibit little environmental variation in volume resistivity. [Means for solving the problem]

[0008] As a result of extensive research into the above-mentioned problems, the present inventors have found that black complex oxide particles that are highly safe, have excellent blackness, low magnetization, and have little environmental variation in volume resistivity can be obtained by containing Fe, Mg, and Al as metal components in specific content ratios, having a half-width indicating crystallinity within a specific range, and containing Cl in a specific content ratio.

[0009] That is, the present invention provides a method for producing a ceramic alloy containing Fe, Mg, and Al as metal components, When the content of Fe is W1 weight %, the content of Mg is W2 weight %, and the content of Al is W3 weight %, the following formula is obtained: 42≦W1≦60 4≦W2≦11 4≦W3≦11 Fulfilling The half-width of the diffraction peak based on the (311) plane, which represents a spinel structure in X-ray crystal structure analysis, is 0.100° or more and 0.220° or less, Furthermore, the present invention provides black complex oxide particles containing Cl in an amount of 5 ppm or more and 100 ppm or less.

[0010] The black complex oxide particles according to the present invention are formed by the reaction of a compound represented by the following formula: 0.07≦W2 / W1≦0.26 0.07≦W3 / W1≦0.26 0.4≦W3 / W2≦2.3 It is preferable that the following is satisfied.

[0011] The black complex oxide particles according to the present invention have a volume cumulative 50% particle diameter D50 of 0.05 μm or more and 0.7 μm or less, and a volume cumulative 90% particle diameter D90 of 1.0 μm or less, as measured by a laser diffraction scattering method; The volume cumulative 50% particle diameter D50 and the BET specific surface area S are calculated by the following formula: 1.3935×D50 -1.144 ≦S≦3.5303×D50 -0.974 It is preferable that the following is satisfied.

[0012] The black complex oxide particles according to the present invention preferably have a blackness L value of 20 or less, a hue a value of 2.0 or less, and a hue b value of 2.0 or less, as measured by a color difference meter in accordance with JIS K5101-1991.

[0013] The black complex oxide particles according to the present invention have a saturation magnetization Ms of 30 Am in an applied magnetic field of 79.6 kA / m. 2 / kg or less is preferable.

[0014] The black complex oxide particles according to the present invention preferably have a common logarithm of volume resistivity RvH (Ωcm) at high temperature and high humidity (30° C., relative humidity 80%) of 7.0 or more.

[0015] In the black complex oxide particles according to the present invention, the environmental variation ratio of volume resistivity (log 10 RvL / log 10 It is preferable that RvH is 1.00 or more and 1.25 or less. [Effects of the Invention]

[0016] The black complex oxide particles according to the present invention are highly safe, have excellent blackness, low magnetization, and exhibit little fluctuation in volume resistivity due to environmental factors. DETAILED DESCRIPTION OF THE INVENTION

[0017] The black complex oxide particles according to the present invention are composed of Fe, Mg, and Al as the main metal components. Regarding the oxides of each element, when only Fe is present, magnetite (Fe3O4), known as a black pigment, is produced. However, when Mg is present, it reacts with Fe to produce magnesium ferrite (MgFe2O4), a brownish color, and when Al is present, hercynite (FeAl2O4), a black oxide, is produced. However, when the three elements Fe, Mg, and Al are used, these elements exist as a solid solution in a spinel structure, and therefore, it is important to adjust the ratio to a specific ratio in order to control the blackness and magnetization.

[0018] Therefore, the black complex oxide particles according to the present invention contain Fe, Mg, and Al as metal components, and when the content of Fe is W1% by weight, the content of Mg is W2% by weight, and the content of Al is W3% by weight, the black complex oxide particles according to the present invention have a composition that satisfies the following formula: 42≦W1≦60 4≦W2≦11 4≦W3≦11 It is important to satisfy the following.

[0019] In the black complex oxide particles according to the present invention, when the Fe content is less than 42% by weight, the magnetization is low but the blackness tends to be low. On the other hand, when the Fe content exceeds 60% by mass, the blackness is high but the magnetization tends to be high. Therefore, from the viewpoint of achieving both blackness and magnetization, it is important to satisfy the relationship 42≦W1≦60. W1 is preferably 45 or more, more preferably 47 or more. W1 is preferably 57 or less, more preferably 55 or less.

[0020] In the black complex oxide particles according to the present invention, if the Mg content is less than 4% by weight, the blackness tends to be high but the magnetization tends to be high. Furthermore, if the Mg content exceeds 11% by mass, the magnetization tends to be low but the blackness tends to be low. Therefore, from the viewpoint of achieving both blackness and magnetization, it is important to satisfy the relationship 4≦W2≦11. W2 is preferably 5 or more, and more preferably 6 or more. Furthermore, W2 is preferably 10 or less, and more preferably 9 or less.

[0021] In the black complex oxide particles according to the present invention, when the Al content is less than 4% by weight, the blackness tends to be high but the magnetization tends to be high. On the other hand, when the Al content exceeds 11% by mass, the magnetization tends to be low but the blackness tends to be low. Therefore, from the viewpoint of achieving both blackness and magnetization, it is important to satisfy the relationship 4≦W3≦11. W3 is preferably 5 or more, and more preferably 6 or more. Furthermore, W3 is preferably 10 or less, and more preferably 9 or less.

[0022] In the black complex oxide particles according to the present invention, it is preferable to further adjust the weight ratio of Mg and Al to Fe, and the weight ratio of Al to Mg, to achieve a better balance between blackness and magnetization. 0.07≦W2 / W1≦0.26 0.07≦W3 / W1≦0.26 0.4≦W3 / W2≦2.3 It is preferable to satisfy the above. Within this range, blackness and magnetization can be more balanced. W2 / W1 is more preferably 0.10 or more, and more preferably 0.20 or less. W3 / W1 is more preferably 0.10 or more, and more preferably 0.20 or less. W3 / W2 is more preferably 0.6 or more, and more preferably 2.0 or less.

[0023] It is important that the black complex oxide particles according to the present invention further contain Cl in addition to Fe, Mg, and Al. However, if the Cl content is less than 5 ppm, the environmental variation of volume resistivity under low temperature and low humidity conditions tends to be relatively large. Furthermore, if the Cl content exceeds 100 ppm, the environmental variation of volume resistivity under high temperature and high humidity conditions tends to be relatively large. Therefore, from the viewpoint of further stabilizing the environmental variation of volume resistivity, it is important that the Cl content is 5 ppm or more and 100 ppm or less. The Cl content is preferably 10 ppm or more, and more preferably 20 ppm or more. Furthermore, the Cl content is preferably 80 ppm or less, and more preferably 50 ppm or less.

[0024] It is important that the black complex oxide particles according to the present invention have a half-width of the diffraction peak based on the (311) plane, which represents a spinel structure in X-ray crystal structure analysis, of 0.100° or more and 0.190° or less. When the half-width is less than 0.100, there are few lattice defects in the spinel structure, and the structure is close to a single spinel crystal structure, which tends to result in high magnetization and low resistance. When the half-width is greater than 0.190, the blackness tends to be reduced. The half-width is more preferably 0.120° or more and 0.170° or less. The half-width of the diffraction peak based on the (311) plane, which represents a spinel structure, can be appropriately adjusted by the production method (wet or dry), the composition ratio of the metal components, the firing temperature, the firing atmosphere, etc.

[0025] It is preferable to adjust the particle size distribution of the black complex oxide particles according to the present invention. Specifically, the volume cumulative 50% particle diameter D50 is preferably 0.05 μm or more and 0.7 μm or less, and more preferably 0.10 μm or more and 0.5 μm or less. By setting D50 to 0.05 μm or more, the desired blackness is easily obtained. Furthermore, by setting D50 to 0.7 μm or less, the particles are easily dispersed in toner particles having a particle size of several μm, and the desired color tone and characteristics of the toner are easily obtained. Furthermore, the volume cumulative 90% particle diameter D90 is preferably 1.0 μm or less and more preferably 0.7 μm or less. By setting D90 to 1.0 μm or less, the particles are easily dispersed in toner particles having a particle size of several μm, and the desired color tone and characteristics of the toner are easily obtained. The lower limit of D90 can be, for example, 0.3 μm or more. The particle size distribution for calculating the above D50 and D90 can be measured by a laser diffraction scattering method.

[0026] In the black complex oxide particles according to the present invention, the volume cumulative 50% particle diameter D50 and the BET specific surface area S are expressed by the following formula: 1.3935×D50 -1.144 ≦S≦3.5303×D50 -0.974 It is preferable to satisfy the above. Since particles usually have a particle size distribution and it is impossible to completely eliminate surface irregularities, it is technically difficult to reduce the BET specific surface area below the above lower limit. By making the BET specific surface area equal to or less than the above upper limit, the particles do not have too many pores relative to the particle size and are less susceptible to changes such as humidity. Furthermore, when used after surface treatment to make them hydrophilic or hydrophobic, the particles are not easily broken due to their sufficient strength, and the untreated portions are less likely to be exposed, making the properties more stable.

[0027] In the black complex oxide particles according to the present invention, when the blackness and hue are measured using a color difference meter in accordance with JIS K5101-1991, the L value is preferably 20 or less, the a value is 2.0 or less, and the b value is 2.0 or less. When these L value, a value, and b value satisfy the above conditions, the blackness is high and the hue has a weak reddish or yellowish tinge, making the particles suitable as a black pigment. The L value is more preferably 19 or less, and even more preferably 17 or less.

[0028] The black complex oxide particles according to the present invention have a saturation magnetization of 30 Am in a load magnetic field of 79.6 kA / m, taking into consideration applications in fields where magnetism is not required, such as non-magnetic toner applications. 2 / kg or less, and 25Am 2 / kg or less is more preferable.

[0029] In the black complex oxide particles according to the present invention, from the viewpoint of maintaining the chargeability when added to a toner and suppressing a decrease in chargeability particularly under high temperature and high humidity conditions (30°C, 80% relative humidity), the common logarithm of the volume resistivity RvH (Ωcm) under high temperature and high humidity conditions (30°C, 80% relative humidity) is preferably 7.0 or more, more preferably 7.5 or more. In addition, the environmental variation ratio of volume resistivity (log 10 RvL / log 10 RvH) is preferably 1.00 or more and 1.25 or less, and more preferably 1.20 or less.

[0030] The black complex oxide particles according to the present invention are usually produced by a dry method, for example, by measuring predetermined amounts of raw materials, pulverizing and mixing them to obtain a slurry, granulating the slurry, and then firing the slurry at 1000°C or higher and 1300°C or lower in an inert atmosphere or a weakly oxidizing atmosphere.

[0031] The black complex oxide particles of the present invention can also be produced by a wet process. However, while more crystal nuclei are present for generating spinel crystals than by a dry process, the low-temperature reaction makes crystal growth more difficult. Furthermore, the low crystallinity tends to result in a larger half-width of the diffraction peak based on the (311) plane, which represents the spinel structure. As a result, the black color tends to be insufficient and the particles are prone to change over time. Furthermore, the difficulty in crystal growth leads to many voids within the particles, which tends to increase the BET specific surface area relative to the particle size. This makes the particles more susceptible to changes in humidity and causes changes over time. Although a method of firing particles after production by a wet process is also possible, the presence of many crystal nuclei makes it difficult to control the spinelization reaction. This can lead to excessive magnetization or excessive sintering, resulting in extremely high hardness and making it difficult to reduce the particle size. Furthermore, particles produced by a wet process tend to have uniform crystal grains, which easily align the magnetic moment when a magnetic field is applied, resulting in high magnetization.

[0032] As the Fe raw material, it is preferable to use Fe2O3. As the Mg raw material, it is preferable to use one or more compounds selected from Mg(OH)2, MgO, and MgCO3. As the Al raw material, it is preferable to use Al2O3. As the Cl raw material, chlorine sources such as magnesium chloride and sodium chloride can also be used, but because they are present in trace amounts compared to Fe, Mg, and Al, it is preferable to adjust the Cl content using Cl, a trace component contained in each of the above raw materials (especially Fe2O3). Note that Fe2O3 produced from iron sulfate or iron sulfate as a raw material contains almost no Cl and it is difficult to adjust the Cl content to the desired level, so it is preferable to use Fe2O3 produced from iron chloride as a raw material. In addition, the Cl content can also be adjusted by changing the firing temperature and firing time.

[0033] These raw materials are weighed in appropriate amounts to achieve the desired elemental composition, then pulverized and mixed in a ball mill or vibration mill for 0.5 hours or more (preferably 1 hour to 20 hours). Water is then added to the pulverized mixture, which is then finely pulverized using a bead mill or the like to obtain a slurry. The degree of pulverization can be controlled by adjusting the diameter, composition, and pulverization time of the beads used as media. From the perspective of uniformly dispersing the raw materials, it is preferable to use fine beads with a particle size of 1 mm or less as media. Furthermore, to uniformly disperse the raw materials, it is preferable to pulverize the pulverized material so that the volume average particle size (particle size at 50% volume cumulative D50) is 2.5 μm or less, and more preferably 2.0 μm or less.

[0034] Next, it is preferable to add a dispersant, a binder, etc. to the obtained slurry as needed to adjust the viscosity to 2 poise or more and 4 poise or less. Polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP) can be used as the binder. Then, the slurry with the viscosity adjusted to the above range is sprayed using a spray dryer and dried to obtain granules.

[0035] The resulting granules are preferably fired in an inert atmosphere or a weakly oxidizing atmosphere at a temperature of 1000 to 1300°C for 2 to 6 hours. The Cl content can also be controlled by the firing temperature and firing time. Here, "in an inert atmosphere or a weakly oxidizing atmosphere" refers to an oxygen concentration of 0.0 to 0.1% by volume (1000 ppm). By setting the firing temperature to 1000°C or higher, the spinelization reaction is more likely to occur, resulting in a high degree of blackness. By setting the firing temperature to 1300°C or lower, the degree of blackness remains high without excessive grain growth during spinelization, and the hardness is reduced, making it easier to reduce the particle size by pulverization or the like. From the viewpoint of blackness and hardness, the firing temperature is preferably 1100 to 1250°C.

[0036] The obtained fired product can be pulverized to the desired particle size using a dry pulverizer such as a pin mill, hammer mill, bead mill, or jet mill, or a wet bead mill. If wet pulverization is performed, the product is dried to obtain particles. In this case, an anti-aggregation agent such as a surfactant can be used to prevent aggregation during drying. If necessary, the product can be classified using an air classifier or the like to obtain particles with the desired particle size distribution.

[0037] The black complex oxide particles according to the present invention as described above are highly safe, have excellent blackness, low magnetization, and little variation in volume resistivity due to environmental factors. Because of their high safety and excellent blackness, they are suitable as black pigments for paints, printing inks, toners, rubber and plastics, and ceramics. Furthermore, because the black complex oxide particles according to the present invention have low magnetization and little variation in volume resistivity due to environmental factors, they are particularly suitable as black pigments for non-magnetic toners to replace less safe carbon black and oxide pigments containing environmentally harmful substances. Toners using the black complex oxide particles according to the present invention can reduce the impact on the natural environment and human body, and can produce high-quality printed matter. [Example]

[0038] Example 1 16.09 kg of Fe2O3 (iron chloride-based raw material, Cl content: 1500 ppm), 4.64 kg of Mg(OH)2, and 4.15 kg of Al2O3 were weighed and milled using a dry media mill (vibration mill, 1 / 8-inch diameter stainless steel beads) for 6 hours (until the D50 reached approximately 5 μm). Water was then added, and the mixture was further milled using a wet media mill (horizontal bead mill, 1 mm diameter zirconia beads) for 6 hours. The particle size (primary particle size of the milled particles) of this slurry was measured using a Microtrac, and the D50 was approximately 2 μm. An appropriate amount of dispersant was added to the resulting slurry, and 0.4 wt% of PVA (10% solution) was added as a binder based on the solid content, and the mixture was then granulated using a spray dryer.

[0039] The mixture was then placed in a tunnel electric furnace, where it was maintained at a firing temperature of 1200°C and an oxygen concentration of 0.0% by volume for 3 hours. The heating rate was 200°C / hour, and the cooling rate was 150°C / hour. The resulting fired material was pulverized in stages using a hammer mill (Maekawa Industries), a pin mill (Makino Sangyo), and a dynamic mill (Nippon Coke & Co., Ltd.), and then classified into particles of the desired particle size using an ultrafine powder classifier CNI (Nippon Pneumatic Mfg. Co., Ltd.), to obtain black composite oxide particles.

[0040] <Example 2> Black complex oxide particles were obtained in the same manner as in Example 1, except that Fe2O3 (iron chloride-based raw material, Cl content: 900 ppm) was used instead of Fe2O3 used as the raw material in Example 1.

[0041] Example 3 Black composite oxide particles were obtained in the same manner as in Example 1, except that FeO (iron chloride-based raw material, Cl content: 2900 ppm) was used instead of FeO used as the raw material in Example 1, and the firing temperature was changed to 1150°C.

[0042] <Examples 4 to 8> Black complex oxide particles were obtained in the same manner as in Example 1, except that the compounding ratio of Fe2O3, Mg(OH)2, and Al2O3 used as raw materials in Example 1 was appropriately changed.

[0043] <Comparative Example 1> Black composite oxide particles were obtained in the same manner as in Example 1, except that FeO (iron chloride-based raw material, Cl content: 3600 ppm) was used instead of FeO used as the raw material in Example 1, and the firing temperature was changed to 1150°C.

[0044] <Comparative Example 2> Black composite oxide particles were obtained in the same manner as in Example 1, except that FeO (iron chloride-based raw material, Cl content: 900 ppm) was used instead of FeO used as the raw material in Example 1, and the firing temperature was changed to 1300°C. <Comparative Examples 3 to 9> Black complex oxide particles were obtained in the same manner as in Example 1, except that the compounding ratio of Fe2O3, Mg(OH)2, and Al2O3 used as raw materials in Example 1 was appropriately changed. In Comparative Example 9, the oxygen concentration during firing was set to 0.5% by volume.

[0045] <Comparative Example 10> Black composite oxide particles were obtained by a wet method. Specifically, a 12.5 mol / L aqueous sodium hydroxide solution was added to 5 L of a 0.15 mol / L aqueous sodium carbonate solution to adjust the pH to 11, and the liquid temperature was raised to 80°C and maintained at that temperature. Meanwhile, 2 L of a mixed sulfate aqueous solution containing 0.75 mol / L ferrous sulfate, 0.10 mol / L ferric sulfate, 0.5 mol / L magnesium sulfate, and 0.25 mol / L aluminum sulfate was prepared and added to the alkaline aqueous solution containing sodium carbonate over 30 minutes while mixing and stirring.

[0046] After the addition was completed, mixing and stirring was continued for 4 hours. During this addition and mixing and stirring, the initial temperature and pH of the reaction solution were adjusted to be maintained. The slurry containing the black composite oxide particles thus obtained was allowed to cool naturally, then neutralized to pH 6 using dilute sulfuric acid, and then washed, dehydrated, and dried by conventional methods to obtain the final black composite oxide particles.

[0047] The black complex oxide particles obtained in Examples 1 to 8 and Comparative Examples 1 to 10 were evaluated for the following points. The results are shown in Table 1 (Examples 1 to 8) and Table 2 (Comparative Examples 1 to 10).

[0048] <Concentration of metal components in black composite oxide particles> The metal content of the black complex oxide particles was determined by chemical analysis (ICP). Specifically, 0.2 g of black complex oxide particles was weighed, and 60 ml of pure water, 20 ml of 1N hydrochloric acid, and 20 ml of 1N nitric acid were added to the weighed black complex oxide particles. The mixture was heated to prepare an aqueous solution in which the black complex oxide particles were completely dissolved. The resulting aqueous solution was placed in an ICP analyzer (ICPS-1000IV, manufactured by Shimadzu Corporation), and the contents of the metal components Fe, Mg, and Al were measured.

[0049] <Cl content in raw material or black composite oxide particles> The Cl content in the raw material or the black composite oxide particles was measured by combustion ion chromatography under the following conditions. -Combustion equipment: Mitsubishi Chemical Analytech AQF-2100H -Sample amount: 50mg - Combustion temperature: 1100℃ - Burn time: 10 minutes -Ar flow rate: 400ml / min -O2 flow rate: 200ml / min -Humidifying Air flow rate: 100ml / min -Absorption solution: Elution solution containing 1% hydrogen peroxide -Analyzer: Tosoh IC-2010 -Column: TSKgel SuperIC-Anion HS (4.6mmI.D.×1cm+4.6mmI.D.×10cm) -Eluent: NaHCO3(3.8mmol / L)+Na2CO3(3.0mmol / L) -Flow rate: 1.5mL / min -Column temperature: 40℃ -Injection volume: 30μL - Measurement mode: Suppressor method -Detector: CM detector -Standard sample: Kanto Chemical Co., Ltd. Anion mixed standard solution

[0050] <FWHM of the diffraction peak based on the (311) plane, which represents the spinel structure> The half-width (°, 2θ) of the diffraction peak based on the (311) plane, which is the main peak of the spinel phase, was measured by powder X-ray diffraction under the following measurement conditions. -X-ray diffractometer: PANalytical X'pert MPD (including high-speed detector) - Source: Co-Kα -Tube voltage: 45kV -Tube current: 40mA -Scanning mode: General batch - Divergence slit (°): 1 / 2 - Light-receiving slit (mm): 5.5 - Measurement interval: 0.010° / second - Counting time (seconds): 10.16 / step - Scanning range (2θ): 15~90°

[0051] <Particle size distribution> The particle size distribution of the black composite oxide particles was measured by the laser diffraction scattering method. First, 10 g of black composite oxide particles and 80 ml of water were placed 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 carried out for 20 seconds. Then, the bubbles formed on the surface of the beaker were removed, and the obtained slurry was introduced into a laser diffraction type particle size distribution measuring device (SALD-7500nano, manufactured by Shimadzu Corporation) for measurement. By this measurement, the 50% diameter (volume cumulative 50% particle diameter D50) and 90% diameter (volume cumulative 90% particle diameter D90) in the volume particle size distribution were determined. The measurement conditions were a pump speed of 7, an internal ultrasonic irradiation time of 30, and a refractive index of 1.70 - 050i.

[0052] <BET specific surface area> The BET specific surface area of the black composite oxide particles was measured using a specific surface area measuring device (Macsorb HM model-1208, manufactured by Mountech). First, about 10 g of black composite oxide particles were placed on a filter paper and degassed with a vacuum dryer to confirm that the vacuum degree was -0.1 MPa or less. Then, the black composite oxide particles were heated at 200°C for 2 hours to remove the moisture adhering to the surface of the black composite oxide particles. About 0.5~4 g of the moisture-removed black composite oxide particles were placed in a standard sample cell dedicated to the measuring device and accurately weighed with a precision balance. Next, the weighed black composite oxide particles were set in the measuring port of the measuring device for measurement. The measurement was performed by the one-point method. The measurement atmosphere was a temperature of 20°C and a relative humidity of 55%.

[0053] <Saturation magnetization> The black complex oxide particles were packed into a cell with an inner diameter of 5 mm and a height of 2 mm, and the cell was set in a vibrating sample magnetometer (VSM-C7-10A, manufactured by Toei Kogyo Co., Ltd.), and the saturation magnetization of the black complex oxide particles was measured in an applied magnetic field of 79.6 kA / m.

[0054] <Volume resistivity> First, the cross-sectional area is 4cm 2 The black complex oxide particles were filled into a fluororesin cylinder to a height of 4 mm. Then, electrodes were attached to both ends, and a 1 kg weight was placed on top of them to measure the electrical resistance. The electrical resistance was measured using a Keithley 2182A nanovoltmeter. A measurement voltage of 1000 V was applied, and the resistance was measured 60 seconds later to calculate the volume resistivity. The measurement environments were room temperature and room humidity (temperature 20°C, relative humidity 55%), high temperature and high humidity (temperature 30°C, relative humidity 80%), and low temperature and low humidity (temperature 10°C, relative humidity 20%). The common logarithm of each volume resistivity (room temperature and room humidity: RvN, high temperature and high humidity: RvH, low temperature and low humidity: RvL) was calculated. These values ​​were also used to calculate the environmental variation ratio (log 10 RvL / log 10 RvH) was calculated.

[0055] <Blackness and hue> The blackness and hue of the black complex oxide particles were measured in accordance with JIS K5101-1991. Specifically, 1.4 cc of castor oil was added to 2.0 g of black complex oxide particles and kneaded using a Huber-type Marler. 7.5 g of lacquer was added to 2.0 g of this kneaded sample and further kneaded. The mixture was then applied to mirror-coated paper using a 4 mil applicator and dried. The blackness (L value) and hue (a value, b value) were then measured using a color difference meter (Color Analyzer TC-1800, manufactured by Tokyo Denshoku).

[0056] [Table 1]

[0057] [Table 2]

[0058] From the above results, it can be seen that the black complex oxide particles obtained in Examples 1 to 8 are highly safe, have excellent blackness, low magnetization, and exhibit little environmental variation in volume resistivity.

Claims

1. Contains Fe, Mg, and Al as metal components, When the content of Fe is W1 wt%, the content of Mg is W2 wt%, and the content of Al is W3 wt%, the following formula is obtained: 42≦W1≦60 4≦W2≦11 4≦W3≦11 Fulfilling the half-width of the diffraction peak based on the (311) plane, which represents a spinel structure in X-ray crystal structure analysis, is 0.100° or more and 0.190° or less; Further, it contains Cl in an amount of 5 ppm or more and 100 ppm or less. Black complex oxide particles.

2. The following formula: 0.07≦W2 / W1≦0.26 0.07≦W3 / W1≦0.26 0.4≦W3 / W2≦2.3 fulfill The black complex oxide particles according to claim 1.

3. a volume cumulative 50% particle diameter D50 measured by a laser diffraction scattering method of 0.05 μm or more and 0.7 μm or less, and a volume cumulative 90% particle diameter D90 measured by a laser diffraction scattering method of 1.0 μm or less; The volume cumulative 50% particle diameter D50 and the BET specific surface area S are calculated by the following formula: 1.3935×D50 －１．１４４ ≦S≦3.5303×D50 －０．９７４ fulfill The black complex oxide particles according to claim 1.

4. When the blackness and hue are measured using 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. The black complex oxide particles according to claim 1 .

5. Saturation magnetization Ms is 30 Amps in an applied magnetic field of 79.6 kA / m. ２ / kg or less The black complex oxide particles according to claim 1 .

6. The common logarithm of volume resistivity RvH (Ωcm) under high temperature and high humidity conditions (30°C, relative humidity 80%) is 7.0 or more. The black complex oxide particles according to claim 1 .

7. The environmental variation ratio of volume resistivity (log ) is the ratio of the common logarithm of the volume resistivity RvL (Ωcm) under low temperature and low humidity (10°C, relative humidity 20%) to the common logarithm of the volume resistivity RvH (Ωcm) under high temperature and high humidity (30°C, relative humidity 80%). １０ RvL / log １０ RvH) is 1.00 or more and 1.25 or less The black complex oxide particles according to claim 1 .

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