JPH0297968A - Magnetic toner - Google Patents

Abstract

PURPOSE:To improve the dispersion and the adhesive strength of magnetic powders and to stabilize the amount of electrification of the subject toner, and to improve the fixation of the toner by incorporating the magnetic powders which are made to hydrophobicity on the surface thereof, and needle-like nonmagnetic metal oxides which are not made to the hydrophobicity in the magnetic toner. CONSTITUTION:The magnetic powders which are made to the hydrophobicity on the surface thereof in the needle-like nonmagnetic metal oxides which are not made to the hydrophobicity are incorporated in the toner. The needle nonmagnetic oxide is composed of a water contg. iron oxide (FeOOH) and hematite (alpha-Fe2O3), etc. The needle particle has a ratio of the major axis to the minor axis of a particle of >=3, preferably >=5. The magnetic powder is composed of a ferromagnetic element and an alloy contg. the element or a compd. contg. the element, etc. and a compd. such as magnetite, hematite, and ferrite and a metal or an alloy such as Fe, Co, Ni and Mn. A hydrophobic treating agent is composed of a surfactant such as a metal salt of fatty acid, etc. or a titanium coupling agent, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic toner used for image formation in electrophotography.

[Prior Art] 'Electrophotography is described in US Pat. No. 2,297. Many studies have been conducted since it was disclosed in Specification H1.

Among them, an improved method of so-called jumping development disclosed in Japanese Patent Application Laid-Open No. 54-42141 is attracting attention as a novel process that overcomes many of the difficulties of electrophotography.

A magnetic toner is used in this developing method, and the dispersibility and adhesion of the magnetic material to the binder resin are important points in determining the performance of the magnetic toner. On the other hand, in order to improve the dispersibility and adhesion of magnetic powder, it has been proposed to hydrophobize the surface of magnetic particles using various surfactants, coupling agents, etc. Publications No. 54-122129, No. 54-127329, No. 5B-84348, etc.).

This generally involves hydrophobicizing the magnetic powder on its hydrophilic surface to improve leakage with the binder resin and improve dispersibility and adhesion.

However, in recent years, electrophotographic processes have been used.

In fields such as copiers and printers, even higher speeds and higher environmental stability are required. Under these circumstances, magnetic toner using magnetic powder subjected to hydrophobization treatment does improve the dispersibility and adhesion of the magnetic powder, but due to the hydrophobization treatment of the magnetic powder, the resistance of the toner itself increases. When this magnetic toner is used in high-speed machines or in low-temperature, low-humidity environments, it becomes difficult to maintain the amount of charge at an appropriate value.At this time, the amount of charge of the magnetic toner increases from the appropriate value. It fluctuates in the direction of If the amount of charge increases abnormally from a proper value, the thickness of the toner coating layer on the sleeve becomes uneven, the image density decreases, and the quality of the image deteriorates.

To address the problem of the amount of charge increasing beyond the appropriate value, a method for controlling the electrical resistance of the toner and stabilizing the amount of charge is to include a magnetic material with a wood-philic surface (Japanese Patent Laid-Open No. 58-88857). (No. Publication) or electrical resistance 108Ω
Containing non-magnetic powder below C layer (Japanese Patent Application Laid-Open No. 60-49
49) has been proposed.

However, when containing magnetic powder with a wood-philic surface, the amount of hydrophobicized magnetic powder must be reduced in order to maintain appropriate magnetic properties as a toner. The amount of magnetic material between toner particles (
Differences in magnetic properties (magnetic properties) are likely to occur.

That is, the method of containing magnetic powder having a hydrophilic surface reduces the advantage of using magnetic powder having a hydrophobic surface to improve magnetic powder dispersibility.

On this point, the method of containing non-magnetic powder with relatively low electrical resistance is to increase the amount of magnetic material between toner particles (as described above).
It can be said that this is an excellent method that does not reduce the advantages of using magnetic powder that has a hydrophobic surface because it hardly causes a difference in magnetic properties.

However, if the binder resin contains a large amount of fine particles such as metal oxides, the viscosity of the resin increases and the fixing properties tend to decrease. The method of adding substances still needs improvement in terms of this deterioration of fixing properties.

The inventors of the present invention have made extensive studies to solve this problem of poor fixing performance, and have found that this problem can be solved by making the nonmagnetic metal oxide particles acicular in shape.

[Problems to be Solved by the Invention] The object of the present invention is to provide a magnetic powder which solves the above problems, has extremely good dispersion and adhesion, and has a stable charge amount, and which also has good fixing properties. Our purpose is to provide magnetic toner.

[Means and Effects for Solving the Problems] According to the present invention, a toner contains magnetic powder whose surface has been subjected to a hydrophobization treatment and an acicular nonmagnetic metal oxide whose surface has not been subjected to a hydrophobization treatment. As a result, the above objectives were achieved.

Non-magnetic metal oxide particles added to adjust the electrical resistance of the toner to an appropriate value and stabilize the weight of the toner have an isotropic shape when the shape is acicular. Compared to the above, it is possible to stabilize the amount of charge of the toner with a small amount added, and it is possible to suppress the deterioration of fixing performance to a smaller extent.

This is because when the particles are acicular, they are exposed to a larger proportion on the toner surface than when they are isotropic, and it is thought that a small amount of added acid lowers the resistance on the toner surface and stabilizes the amount of charge. It is.

Examples of the acicular nonmagnetic metal oxides of the present invention that are not subjected to hydrophobization treatment include hydrated iron oxide (Fe00H) and hematite (α-Fe2
03) etc. can be used.

In addition, being acicular here means that the ratio of the length of the long sleeve to the length of the short axis, the length of the long sleeve/length of the short axis (hereinafter referred to as "long/short axis ratio"), is 3 or more. , more preferably 5 or more. If the long/minor axis ratio is 3 or less, it will have an isotropic shape, and a sufficient effect will not be obtained even with a small amount.

The magnetic powder used in the present invention includes ferromagnetic elements, alloys and compounds containing these elements, and compounds such as magnetite, magnetite, ferrite, and metals and alloys such as iron, cobalt, nickel, and manganese. , known magnetic materials can be used.

In addition, as a treatment agent for hydrophobicizing the surface of magnetic powder,
Surfactants such as fatty acid metal salts, titanium coupling agents,
Coupling agents such as silane coupling agents can be used.

The amount of hydrophobized magnetic powder to be contained in the magnetic toner is 20 to 140 parts by weight based on the binder resin, and 40 parts by weight.
~100 parts are preferred.

As the acicular non-magnetic metal oxide, 0
．． It is preferably 5 to 40 parts by weight, more preferably 1 to 30 parts by weight. If the metal hardener is less than 0.5 parts by weight M8B, there is no effect of stabilizing the toner charge, and if it is more than 40 parts by weight, the fixing performance may be reduced. It happens.

To measure the shape and major/minor axis ratio of the acicular nonmagnetic metal oxide, the acicular nonmagnetic metal oxide is photographed using a transmission electron microscope at a magnification of approximately 20,000 times. At this time, take several pictures of different fields of view with the particles separated one by one.

The diameter in the longest direction of the particle shown in the photograph of the acicular non-magnetic metal oxide is the long diameter, the diameter in the shortest direction is the short axis diameter, and the long@diameter/short axis diameter is the diameter of the particle. Long/short axis ratio. This measurement should be carried out at least 50 times per sample.
The average value of zero or more particles is taken as the length/j12 axis ratio of the acicular nonmagnetic metal oxide.

In addition, the crystal resin used in the present invention includes polystyrene,
Homopolymers of styrene and its substituted products, such as poly-p-chlorostyrene, polyvinyltoluene, styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer, and copolymers thereof; styrene-methyl acrylate copolymer Copolymers of styrene and acrylic acid esters such as , styrene-acrylic, ethyl phosphate copolymer, styrene-n-butyl acrylate copolymer: styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer Polymers, copolymers of styrene and methacrylic esters such as styrene-n-butyl methacrylate copolymers; multi-component copolymers of styrene and acrylic esters and methacrylic esters; other styrene-acrylonitrile copolymers, Styrene and other vinyl-based materials such as styrene-vinyl methyl ether copolymer, styrene-butadiene copolymer, styrene-vinyl methyl ketone copolymer, styrene-acrylonitrile-indene copolymer, and styrene-maleate ester copolymer. Styrenic copolymers with monomers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyester, polyamide, epoxy resin, polyvinyl butyral, polyacrylic acid, phenolic resin, aliphatic or alicyclic hydrocarbon resin, petroleum resin , chlorinated paraffin, etc. can be used alone or in combination.

If necessary, a charge control agent, a colorant, and a fluidity modifier may be added to the toner, and the charge control agent and fluidity modifier are mixed (externally added) with the toner particles and used. As the charge control agent, there are metal-containing dyes, nigrosine, etc. As the coloring agent, conventionally known dyes and pigments can be used.As the fluidity modifier, niroidal silicate fatty acids and the like can be used. metal salts, etc. In addition, for the purpose of increasing the amount, fillers such as calcium carbonate and finely divided silica can be incorporated into the 1-ner in an amount of 0.5 to 20% by weight. Furthermore, in order to prevent mutual aggregation of toner particles and improve their fluidity, a fluidity improver such as fine Teflon powder may be added, and this is for the purpose of improving mold releasability during hot roll fixing. It is also possible to add about 0.5 to 5% by weight of waxy substances such as low molecular weight polyethylene, low molecular weight polypropylene, microblisterine wax, carnauba wax, and Sasol wax.

Note that the present invention is not limited to the examples listed here.

[Example] Hereinafter, one example of the present invention will be specifically described. still,
All parts in the examples are parts by weight.

Example 1 After cooling, it was coarsely pulverized using a speed mill, then finely pulverized using a jet mill, and further classified using a zigzag classifier to obtain a toner having a volume average diameter of 11 μι. To this, 0.4% by weight of colloidal silica was externally added and mixed to obtain a toner.

Comparative Example 1 A toner was obtained in the same manner as in Example 1 except that only the acicular nonmagnetic metal oxide that was not subjected to hydrophobization treatment was removed.

The toners obtained in Example 1 and Comparative Example 1 were used in a Canon copier MP-5540 (copy speed A4:40).
Images were continuously printed at a rate of 2,000 images (images per minute) in a low-temperature, low-humidity environment. As a result, Table 1: O...No problem at all.

○Δ: Sleeve coat unevenness does not occur, but tripo increases slightly.

Δ: Sleeve coat unevenness occurs.

Examples 2-4. Comparative Example 2 A toner was obtained in the same manner as in Example 1, except that the amount of the acicular non-magnetic metal oxide that was not subjected to hydrophobization treatment in Example 1 was changed as shown in Table 2, and the same test as in Example 1 was carried out. The tests were carried out under low temperature and low humidity, and high temperature and high humidity.

Table 2 Examples 5 to 6, Comparative Example 3 Example except that the acicular non-magnetic metal oxide of Example 1 which was not subjected to hydrophobization treatment was used with α-Fe2031O portion having a long/short axis ratio as shown in the table below. A toner was obtained in the same manner as in Example 1.
I conducted a similar test.

Table 3 [Effects of the Invention] As described above, according to the magnetic toner of the present invention, high quality images can be obtained for a long period of time even under low temperature and low humidity conditions and high temperature and high humidity conditions.

Claims (1)

[Claims] (1) A magnetic toner characterized by containing at least magnetic powder whose surface has been hydrophobized and acicular nonmagnetic metal oxide whose surface has not been hydrophobized.