MAGNETIC SUBSTANCE, MAGNETIC TONER, AND MAGNETIC POWDER

Abstract

There is provided a magnetic substance containing substituted -iron oxide particles applicable as a magnetic toner of one-component development system, and a technique related thereto, which is the magnetic substance containing substituted -iron oxide particles in which a part of -iron oxide is substituted with a metal element other than iron, and satisfying at least one of the following conditions: (Condition 1) A molar extinction coefficient of a magnetic substance dispersion liquid at a wavelength of 450 nm is less than 770 dm.sup.3 mol.sup.1 cm.sup.1. (Condition 2) A molar extinction coefficient of the magnetic substance dispersion liquid at a wavelength of 500 nm is less than 430 dm.sup.3 mol.sup.1 cm.sup.1.

Claims

1. A magnetic substance containing substituted -iron oxide particles in which a part of iron oxide is substituted with a metal element other than iron, and satisfying at least one of the following conditions: (Condition 1) A molar extinction coefficient of a magnetic substance dispersion liquid at a wavelength of 450 nm is less than 770 dm.sup.3mol.sup.1 cm.sup.1; (Condition 2) A molar extinction coefficient of the magnetic substance dispersion liquid at a wavelength of 500 nm is less than 430 dm.sup.3 mol.sup.1 cm.sup.1.

2. The magnetic substance according to claim 1, wherein the molar extinction coefficient of the dispersion liquid at a wavelength of 450 nm is 400 dm.sup.3 mol.sup.1 cm.sup.1 or less.

3. The magnetic substance according to claim 1, wherein the molar extinction coefficient of the dispersion liquid at a wavelength of 500 nm is 250 dm.sup.3 mol.sup.1 cm.sup.1 or less.

4. The magnetic substance according to claim 1, wherein the metal element is at least one of aluminum, gallium and indium.

5. The magnetic substance according to claim 1, which is provided for magnetic toner application of one-component development system.

6. A magnetic toner, containing the substituted -iron oxide particles in the magnetic substance of claim 1, and a binder resin.

7. A magnetic powder composed of the substituted -iron oxide particles in the magnetic substance of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1 is a diagram showing ultraviolet-visible absorption spectra obtained in Examples 1-1 to 1-3 and a Comparative example.

[0020] FIG. 2 is a diagram showing ultraviolet-visible absorption spectra obtained in Examples 2-1 to 2-3 and a Comparative example.

DETAILED DESCRIPTION OF THE INVENTION

[0021] Embodiments of the present invention will be described in an order of (1) Substituted -iron oxide particles, (2) Mixed solvent and vehicle, and (3) Colloid of substituted -iron oxide particles.

(1) Substituted -Iron Oxide Particles

[0022] The substituted -iron oxide particles used in the present invention are not particularly limited as long as they are particles in which a part (iron element) of -iron oxide is substituted with a metal element other than iron. However, as indicated by the items of the embodiments described later, it is preferable that the metal element used for substitution is at least one of aluminum (Al), gallium (Ga) and indium (In). In the case of -M.sub.xFe.sub.2-xO.sub.3 (M is any one of aluminum (Al), gallium (Ga) and indium (In)), a substitution amount is in a range of 0<x<2, preferably 0.25<x<2, and more preferably 0.5<x<2. It is preferable to set the substitution amount in this range, because transparency can be increased.

(2) Mixed Solvent and Vehicle

[0023] In the present invention, a mixed solvent and a vehicle will be described.

[0024] The mixed solvent used in the present invention is a mixed solution of toluene and methyl ethyl ketone as shown in examples described later.

[0025] Then, as a vehicle used in the present invention, as also shown in examples described later, a vehicle in which urethane resin and vinyl chloride resin are dissolved in a mixed solution of acetylacetone, n-butyl stearate, and cyclohexane, can be used.

[0026] In this embodiment, the substituted -iron oxide particles are dispersed in the mixed solution of the mixed solvent and the vehicle to form a colloid (dispersion liquid, dispersion body).

(3) Colloid of Substituted -Iron Oxide Particles

[0027] In the present invention, as a method for preparing a colloid of substituted -iron oxide particles, substituted -iron oxide particles are dispersed in a predetermined solvent using a shaking type stirring device to obtain a colloid. As an example, the substituted -iron oxide particles, the mixed solvent, the vehicle, and a mixing ball (for example, zirconia ball of 0.3 mm) are charged into a container such as a centrifuge tube. Then, by shaking the container at a shaking number of 100 to 3000 times/min, with an amplitude of 1 to 10 mm, and for 0.5 to 10 hours, the abovementioned colloid is obtained.

[0028] Further, in the items of the embodiments described later, the ultraviolet-visible absorption spectrum of the colloid was also measured (FIGS. 1 and 2). As a result, it was confirmed that the molar extinction coefficient indicating the turbidity of the liquid was greatly reduced as compared with a Comparative example described later.

[0029] More specifically, it can be said that transparency is higher when the molar extinction coefficient is as low as possible in the ultraviolet-visible absorption spectrum, and therefore it is preferable that the molar extinction coefficient shows a value as low as possible. Specifically, it is preferable that the molar extinction coefficient of the magnetic substance dispersion liquid containing substituted -iron oxide particles at a wavelength of 450 nm is less than 770 dm.sup.3 mol.sup.1 cm.sup.1, and more preferably 400 dm.sup.3 mol.sup.1 cm.sup.1 or less, and still more preferably 360 dm.sup.3 mol.sup.1 cm.sup.1 or less.

[0030] Further similarly, it is preferable that the molar extinction coefficient of the magnetic substance dispersion liquid containing substituted -iron oxide particles at a wavelength of 500 nm is less than 430 dm.sup.3 mol.sup.1 cm.sup.1, and more preferably 250 dm.sup.3 mol.sup.1 cm.sup.1 or less, and even more preferably 210 dm.sup.3 mol.sup.1 cm.sup.1 or less.

[0031] Generally, it is known that when the measurement wavelength is shifted to the low wavelength (short wavelength) side, the increase of absorbance rapidly occurs, and in the case of particles having lower absorbance at the lower wavelength side, the measurement sample indicates that the turbidity is lower, that is, the transparency of the liquid is higher. Accordingly, at 400 nm which is the lower wavelength side, the absorbance is preferably less than 1500 dm.sup.3 mol.sup.1 cm.sup.1, preferably less than 1250 dm.sup.3 mol.sup.1 cm.sup.1, and more preferably less than 1000 dm.sup.3 mol.sup.1 cm.sup.1. By using the particles having such properties, a toner in which coloration is suppressed over a so-called visible light range (wavelength: 380 to 780 nm) can be obtained, which is preferable.

[0032] Although the present inventors are intensively studying on a mechanism that brings out these effects, mainly, as shown in this embodiment or the examples described later, by element substitution for -iron oxide, an action of shifting the absorption wavelength of light to the ultraviolet region is generated. As a result, it is considered that the coloration is greatly reduced.

[0033] A magnetic toner can be obtained by mixing the substituted -iron oxide particles and a binder resin. As a specific method for obtaining the magnetic toner, known ones may be adopted. For example, the kind of the binder resin may be a polystyrene resin, a styrene-acrylic resin, a polyester resin, an epoxy resin, a polyamide resin, or the like.

[0034] As described above, the magnetic substance with reduced coloration is realized, with the one-component development system as a cue. However, of course, application of the magnetic substance to other applications is not hindered.

EXAMPLES

[0035] The present invention will be more specifically described hereafter, with reference to examples.

Example 1-1

(1) Preparation of Al-Substituted -Iron Oxide Particles

[0036] Al substituted -Fe.sub.2O.sub.3 crystal particles (-Al.sub.0.66Fe.sub.1.34O.sub.3) were prepared as follows.

[0037] 3524 mL of pure water was placed in a 5 L beaker, and 346.7 g of iron (III) nitrate nonahydrate and 185.4 g of aluminum (III) nitrate nonahydrate were added and dissolved by stirring. While stirring the solution, 363.6 mL of a 25% aqueous ammonia solution was added and the mixture was stirred for 30 minutes. While stirring was continued, 395.4 mL of tetraethoxysilane (TEOS) was added dropwise to the mixed solution, and the mixture was stirred for 20 hours.

[0038] The obtained mixed solution was filtered, the precipitate was washed with pure water, dried, and pulverized in a mortar to obtain pulverized powder. The obtained pulverized powder was subjected to heat treatment in a furnace at 1100 C. for 4 hours in an air atmosphere to obtain a heat treated powder.

[0039] The obtained heat-treated powder was disintegrated in a mortar and thereafter added to a 0.8 mol/L sodium hydroxide (NaOH) aqueous solution. Then, silicon oxide was removed from the heat-treated powder by stirring at a liquid temperature of 65 C. for 24 hours. Next, the heat-treated powder from which silicon oxide was removed was centrifuged to precipitate, and the supernatant liquid was discarded, and thereafter pure water was added, washed, and centrifuged again.

[0040] The washed precipitate was filtered and recovered, and thereafter dried to obtain Al-substituted -iron oxide particles.

[0041] Magnetic properties of the obtained Al substituted -iron oxide particle sample were measured, and specifically they were measured at maximum applied magnetic field of 50 kOe, and at temperature 300 K, using SQUID (superconducting quantum interferometer) of MPMS 7 manufactured by Quantum Design Corporation.

[0042] As a result, it was confirmed that the saturation magnetization of the Al substituted -iron oxide particle sample was 17.3 emu/g, and the obtained Al substituted -iron oxide particle sample was a magnetic substance.

[0043] Composition analysis was performed for the obtained Al substituted -iron oxide particles, and it was found that a nanomagnetic particle powder sample having a composition of -Al.sub.0.66 Fe.sub.1.34O.sub.3 was obtained. When crystal analysis by Rietveld analysis was performed, particles satisfying a=5.039 , b=8.662 , c=9.343 , crystal volume=424.2 .sup.3 were obtained. At this time, calculation was performed and it was found that 27% of A site, 8% of B site, 31% of C site, and 67% of D site in the crystal structure of -Fe.sub.2O.sub.3 were substituted with aluminum.

(2) Preparation of Colloid of Al Substituted -Iron Oxide Particles

[0044] 10 mg of -Al.sub.0.66Fe.sub.1.34O.sub.3 nanoparticle powder, 1.4 ml of a mixed solvent (toluene:methyl ethyl ketone=1:1), 0.5 mL of vehicle (34.9 g of a urethane resin (UR-8200 manufactured by Toyobo Co., Ltd.) and 15.8 g of a vinyl chloride resin (MR-555 manufactured by Zeon Corporation) were dissolved in a mixed solvent of 0.25 g of acetylacetone, 0.25 g of n-butyl stearate, and 97.9 mL of cyclohexane), and 20 g of zirconia ball of 0.3 mm, were charged into a 50 mL centrifuge tube.

[0045] Then, the centrifuge tube was set on a shaker, and the Al substituted -iron oxide particles were dispersed in the mixed solvent by shaking and stirring 2000 times/min, with an amplitude of 3 mm, and for 4 hours, to obtain an Al substituted -iron oxide particle dispersion liquid (colloid).

[0046] Finally, the concentration was adjusted by adding a mixed solvent (toluene:methyl ethyl ketone=1:1), and spectroscopic measurement was performed to obtain ultraviolet-visible absorption spectrum of -iron oxide particle dispersion liquid (colloid) of 0.02 mol/L. In the spectroscopic measurement, the colloid was loaded into a quartz cell and measurement was performed using JASCO V-670 manufactured by JASCO Corporation.

Example 1-2

[0047] Example 1-1 was repeated except that addition amount of aluminum and iron was adjusted to obtain -Al.sub.0.48Fe.sub.1.52O.sub.3 instead of -Al.sub.0.66Fe.sub.1.34O.sub.3 as Al substituted -iron oxide particles. A spectral diagram obtained by subjecting the obtained colloidal solution to spectroscopic measurement is also shown in FIG. 1.

Example 1-3

[0048] Example 1-1 was repeated except that addition amount of aluminum and iron was adjusted to obtain -Al.sub.0.75Fe.sub.1.25O.sub.3 instead of -Al.sub.0.66Fe.sub.1.34O.sub.3 as Al substituted -iron oxide particles. A spectral diagram obtained by subjecting the obtained colloidal solution to spectroscopic measurement is also shown in FIG. 1.

[0049] As shown in FIG. 1, it was confirmed that the molar extinction coefficient became smaller as the amount of aluminum substitution was increased.

Example 2-1

[0050] (1) Preparation of Ga Substituted -Iron Oxide Particles

[0051] Ga substituted -Fe.sub.2O.sub.3 crystal particles (-Ga.sub.0.67Fe.sub.1.33O.sub.3) were prepared as follows.

[0052] 1988 mL of pure water was placed in a 5 L beaker, and 174.5 g of iron (III) nitrate nonahydrate and 102.6 g of gallium nitrate (III) octahydrate were added and dissolved by stirring. While stirring the solution, 199.1 mL of a 25% aqueous ammonia solution was added and the mixture was stirred for 30 minutes. While stirring was continued, 225.5 mL of tetraethoxysilane (TEOS) was added dropwise to the mixed solution, and the mixture was stirred for 20 hours.

[0053] The obtained mixed solution was filtered, the precipitate was washed with pure water, dried, and pulverized in a mortar to obtain pulverized powder. The obtained pulverized powder was subjected to heat treatment in a furnace at 1150 C. for 6 hours in an air atmosphere to obtain a heat treated powder.

[0054] The obtained heat-treated powder was disintegrated in a mortar and thereafter added to a 0.4 mol/L sodium hydroxide (NaOH) aqueous solution. Then, silicon oxide was removed from the heat-treated powder by stirring at a liquid temperature of 65 C. for 24 hours. Next, the heat-treated powder from which silicon oxide was removed was centrifuged to precipitate, and the supernatant liquid was discarded, and thereafter pure water was added, washed, and centrifuged again.

[0055] The washed precipitate was filtered and recovered, and thereafter dried to obtain Ga substituted -iron oxide particles.

[0056] Magnetic properties of the obtained Ga substituted -iron oxide particle sample were measured, and specifically they were measured at maximum applied magnetic field of 90 kOe, and at temperature of 300 K, using SQUID (superconducting quantum interferometer) of MPMS 7 manufactured by Quantum Design Corporation.

[0057] As a result, it was confirmed that the saturation magnetization of the Ga substituted -iron oxide particle sample was 17.0 emu/g, and the obtained Ga substituted -iron oxide particle sample was a magnetic substance.

[0058] Further, composition analysis was performed for the obtained Ga substituted -iron oxide particles, and it was found that a nanomagnetic particle powder sample having a composition of -Ga.sub.0.67 Fe.sub.1.33O.sub.3 was obtained. In addition, when crystal analysis by Rietveld analysis was performed, particles satisfying a=5.085 , b=8.755 , c=9.410 , crystal volume=418.4 .sup.3 were obtained. At this time, calculation was performed and it was found that Fe at the A site was not substituted, and 9% of B site, 28% of C site, and 98% of D site in the crystal structure of -Fe.sub.2O.sub.3 were substituted with gallium.

(2) Preparation of Colloid of Ga Substituted -Iron Oxide Particles

[0059] A colloid of Ga substituted -iron oxide particles was prepared in the same manner as in Example 1 and subjected to spectroscopic measurement to obtain an ultraviolet-visible absorption spectrum.

Example 2-2

[0060] Example 2-1 was repeated except that addition amount of gallium and iron was adjusted to obtain -Ga.sub.0.29Fe.sub.1.71O.sub.3 instead of -Ga.sub.0.67Fe.sub.1.33O.sub.3 as Ga substituted -iron oxide particles. A spectral diagram obtained by subjecting the obtained colloidal solution to spectroscopic measurement is also shown in FIG. 2.

Example 2-3

[0061] Example 2-1 was repeated except that addition amount of gallium and iron was adjusted to obtain -Ga.sub.0.94Fe.sub.1.06O.sub.3 instead of -Ga.sub.0.67Fe.sub.1.33O.sub.3 as Ga substituted -iron oxide particles. A spectral diagram obtained by subjecting the obtained colloidal solution to spectroscopic measurement is also shown in FIG. 2.

[0062] As shown in FIG. 2, it was confirmed that the molar extinction coefficient became smaller as the amount of gallium substitution was increased.

Comparative Example

[0063] In this Comparative example, the method described in Japanese Patent Application Laid-open No. 2014-224027 relating to the method for producing -iron oxide particles (unsubstituted) disclosed by the present inventors was adopted.

(1) Preparation of -Iron Oxide Particles (Unsubstituted)

[0064] 420 mL of pure water and 8.0 g of an oxide hydroxide (III) (-FeO (OH)) nanoparticle sol having an average particle size of 6 nm were placed in a 1 L Erlenmeyer flask, and the mixture was stirred until it became a homogeneous solution. 19.2 mL of a 25% ammonia (NH.sub.3) aqueous solution was added to the above solution dropwise at 1 to 2 drops/sec, followed by stirring in an oil bath (or a water bath) at 50 C. for 30 minutes. Further, 24 mL of tetraethoxysilane (Si(OC.sub.2H.sub.5).sub.4) was added dropwise to this solution at 2 to 3 drops/sec. After stirring at 50 C. for 20 hours, the mixture was allowed to cool to room temperature and 20 g of ammonium sulfate ((NH.sub.4).sub.2SO.sub.4) was added to obtain a precipitate.

[0065] The precipitate was separated by centrifugation, washed with pure water, transferred to a petri dish, dried at 60 C. overnight, and thereafter pulverized in an agate mortar. Then, heat treatment was performed at 1020 C. for 4 hours in a furnace in the atmosphere. Thereafter, etching treatment was performed with a 5 M aqueous solution of sodium hydroxide (NaOH) for 24 hours to obtain -Fe.sub.2O.sub.3 particles from which silica was removed.

(2) Preparation of Colloid of -Iron Oxide Particles (Unsubstituted)

[0066] A colloid of -iron oxide particles (unsubstituted) was prepared in the same manner as in Example 1 and subjected to spectroscopic measurement to obtain an ultraviolet-visible absorption spectrum.

[Verification]

[0067] Each Example and Comparative example was verified below.

(Result of Ultraviolet and Visible Absorption Spectrum)

[0068] The ultraviolet-visible absorption spectra (vertical axis: molar absorption coefficient, horizontal axis: wavelength) obtained in Examples 1-1 to 1-3 and Comparative example are shown in FIG. 1, and the UV-visible absorption spectra (vertical axis: molar extinction coefficient, horizontal axis: wavelength) obtained in Examples 2-1 to 2-3 and Comparative example are shown in FIG. 2. As shown in FIG. 1 and FIG. 2, when the colloid of substituted -iron oxide particles is used, absorption of light is considerably suppressed as shown in each example, compared with the Comparative example (-Fe.sub.2O.sub.3), and therefore the coloration was extremely suppressed and it was very close to transparent.

[0069] The following Table 1 summarizes the measurement results of molar extinction coefficients of Examples and Comparative example.

TABLE-US-00001 TABLE 1 -M.sub.xFe.sub.(2x)O.sub.3 Molar extinction coefficient M:Al, M:Ga, (dm.sup.3 mol.sup.1 cm.sup.1) x-value x-value 500 nm 450 nm 400 nm Example 1-2 0.48 224 417 984 Example 1-1 0.66 193 359 813 Example 1-3 0.75 142 259 665 Example 2-2 0.29 300 556 1282 Example 2-1 0.67 204 377 830 Example 2-3 0.94 138 236 558 Comparative 427 774 1531 example

[0070] As an Example of Table 1, compared with the molar extinction coefficient of 774 dm.sup.3 mol.sup.1 cm.sup.1 of the dispersion liquid of the Comparative example (-Fe.sub.2O.sub.3) at a wavelength of 450 nm, the molar extinction coefficient was 359 dm.sup.3 mol.sup.1 cm.sup.1 in Example 1-1 (-Al.sub.0.66 Fe.sub.1.34O.sub.3), and 377 dm.sup.3 mol.sup.1 cm.sup.1 in Example 2-1 (-Ga.sub.0.67Fe.sub.1.33O.sub.3) at the above wavelength.

[0071] In view of the above contents, it is preferable that the molar extinction coefficient of the dispersion liquid at a wavelength of 450 nm is less than 774 dm.sup.3 mol.sup.1 cm.sup.1, further preferably 770 dm.sup.3 mol.sup.1 cm.sup.1 or less, and more preferably 400 dm.sup.3 mol.sup.1 cm.sup.1 or less, and still more preferably 360 dm.sup.3 mol.sup.1 cm.sup.1 or less.

[0072] Further, compared with the molar extinction coefficient of 427 dm.sup.3 mol.sup.1 cm.sup.1 of the Comparative example (-Fe.sub.2O.sub.3) at a wavelength of 500 nm, the molar extinction coefficient was 193 dm.sup.3 mol.sup.1 cm.sup.1 in Example 1-1 (-Al.sub.0.66Fe.sub.1.34O.sub.3), and 204 dm.sup.3 mol.sup.1 cm.sup.1 in Example 2-1 (-Ga.sub.0.67Fe.sub.1.33O.sub.3) at the above wavelength.

[0073] In view of the above contents, it is preferable that the molar extinction coefficient of the dispersion liquid at a wavelength of 500 nm is preferably 430 dm.sup.3 mol.sup.1 cm.sup.1 or less (preferably less than), further preferably less than 427 dm.sup.3 mol.sup.1 cm.sup.1, and more preferably 250 dm.sup.3 mol to 1 cm.sup.1 or less, and sill more preferably 210 dm.sup.3 mol to 1 cm.sup.1 or less.

[0074] Further, compared with the molar extinction coefficient of 1531 dm.sup.3 mol.sup.1 cm.sup.1 of the Comparative example (-Fe.sub.2O.sub.3) at a wavelength of 400 nm, the molar extinction coefficient was 813 dm.sup.3 mol.sup.1 cm.sup.1 in Example 1-1 (-Al.sub.0.66Fe.sub.1.34O.sub.3), and 830 dm.sup.3 mol.sup.1 cm.sup.1 in Example 2-1 (-Ga.sub.0.67Fe.sub.1.33O.sub.3) at the above wavelength.

[0075] In view of the above contents, the molar extinction coefficient of the dispersion liquid at a wavelength of 400 nm is 1500 dm.sup.3 mo.sup.l-1 cm.sup.1 or less (preferably less than), more preferably 1250 dm.sup.3 mol.sup.1 cm.sup.1 or less (preferably less than), and still more preferably 1000 dm.sup.3 mol.sup.1 cm.sup.1 or less (preferably less than).

[Conclusion]

[0076] As a result, in each example, it was found that brown coloration was suppressed as compared with the comparative example, and as a result thereof, each example could be applied as a magnetic toner of a one-component developing system.