Canon Kabushiki Kaisha

Tadashi Dojo

Yusuke Hasegawa

Michihisa Magome

Tomohisa Sano

Nene Shibayama

Yuichi Mizoo

Takashi Matsui

Shuichi Hiroko

Eriko Yanase

Akira Sakakibara

Takashige Kasuya

Katsuhisa Yamazaki

Satoshi Matsunaga

Takeshi Naka

Tsuneo Nakanishi

Masami Azuma

Masaki Ojima

Yoshitaka Suzumura

Satoru Inami

Masahito Kato

Nobuyoshi Yoshida

Junko Yoshikawa

Ryota Kashiwabara

Nene Dojo

The magnetic toner includes magnetic toner particles comprising a binder resin and a magnetic body and inorganic fine particles present on the surface of the magnetic toner particles, wherein

Magnetic toner

A magnetic toner contains magnetic toner particles containing a binder resin and a magnetic body, and inorganic fine particles present on the surface of the magnetic toner particles, wherein the inorganic fine particles present on the surface of the magnetic toner particles contain metal oxide fine particles, the metal oxide fine particles containing silica fine particles, and optionally containing titania fine particles and alumina fine particles, and a content of the silica fine particles being at least 85 mass % with respect to a total mass of the silica fine particles, the titania fine particles and the alumina fine particles, when a coverage ratio A (%) is a coverage ratio of the magnetic toner particles' surface by the inorganic fine particles and a coverage ratio B (%) is a coverage ratio of the magnetic toner particles' surface by the inorganic fine particles that are fixed to the magnetic toner particles' surface, the magnetic toner has a coverage ratio A and a coverage ratio B/coverage ratio A in prescribed ranges, wherein the magnetic toner has a dielectric constant &#x2208;' and a dielectric loss tangent in prescribed ranges.

The magnetic toner includes magnetic toner particles comprising a binder resin and a magnetic body and inorganic fine particles present on the surface of the magnetic toner particles, wherein the inorganic fine particles present on the surface of the magnetic toner particles comprise metal oxide fine particles, the metal oxide fine particles containing silica fine particles, and optionally containing titania fine particles and alumina fine particles, and a content of the silica fine particles being at least 85 mass % with respect to a total mass of the silica fine particles, the titania fine particles and the alumina fine particles, wherein;when a coverage ratio A (%) is a coverage ratio of the magnetic toner particle's surface by the inorganic fine particles and a coverage ratio B (%) is a coverage ratio of the magnetic toner particle' surface by the inorganic fine particles that are fixed to the magnetic toner particle's surface, the magnetic toner has a coverage ratio A, a coefficient of variation on the coverage ratio A, a ratio of the coverage ratio B to the coverage ratio A, and a compression ratio in a specific range.

An image-forming method is provided which can provide stable image density irrespective of use environments and does not cause image defects such as fogging, tailing, or transfer voids, even when being applied to a developing sleeve with a reduced diameter. In the image-forming method, a latent image bearing member and a toner bearing member bearing a magnetic toner on its surface and having inside a unit for generating a magnetic field are placed with a predetermined interval, and an alternating field is applied between the latent image bearing member and the toner bearing member, and an electrostatic latent image borne by the latent image bearing member is developed with the magnetic toner. The toner bearing member has a specific diameter, and the magnetic toner has a specific circularity and a specific compressibility. The total energy of the toner measured with a powder flowability measuring apparatus satisfies a specific value.

Image-forming method, magnetic toner, and process unit

To provide a magnetic toner which: enables a stable image density to be obtained irrespective of a use environment; and exhibits excellent low-temperature fixability, little image deterioration upon fixation, high coloring power, and a reduced toner consumption. The present invention relates to a magnetic toner containing at least: a binder resin; and a magnetic body. The binder resin contains a polyester unit. The toner has a weight average particle size of 5.0 to 9.0 &#x3bc;m, a true specific gravity of 1.3 to 1.7 g/cm, and a saturated magnetization of 20 to 35 Am/kg in a magnetic field of 796 kA/m. The dielectric loss tangent (tan &#x3b4;) of the toner satisfies (tan &#x3b4;&#x2212;tan &#x3b4;)/tan &#x3b4;&#x2266;0.20 at 100 kHz.

To solve a thin image density and sweeping occurring when a toner carrying member having a small diameter is used, provided is an image-forming method including: a charging step; an electrostatic latent image-forming step; a developing step; a transferring step; and a fixing step, in which a magnetic toner to be used in the method has a specific weight average particle diameter (D4); the magnetic toner has a specific intensity of magnetization in a specific magnetic field; and a surface free energy of a surface of the magnetic toner and a surface free energy of a surface of a toner carrying member to be used in the method satisfy specific relationships.

Magnetic toner and image-forming method

In a magnetic toner which has magnetic toner base particles containing at least a binder resin and a magnetic material, and an inorganic fine powder, (i) the magnetic toner has an average circularity of from 0.950 or more to 1.000 or less, (ii) the magnetic toner has a compressibility of 30 or less, and (iii) the magnetic toner contains boron nitride particles having a median diameter (D50) of from 0.5 &#x3bc;m or more to 8.0 &#x3bc;m or less, as the inorganic fine powder in an amount of from 0.05 part by mass or more to 1.00 part by mass or less based on 100 parts by mass of the magnetic toner base particles. This provides a magnetic toner with which stable image density can be achieved without regard to service environment and which do not cause any image defects such as fog.

In a toner containing at least a binder resin, a colorant, an ester compound and a low-melting material, the ester compound is an ester of dipentaerythritol with a carboxylic acid having 18 or more to 25 or less carbon atoms, and, where the melting point of the ester compound is represented by Tm(&#xb0; C.) and the melting point of the low-melting material is represented by Tm(&#xb0; C.), the toner satisfies the relationship of:+5.

Toner

To provide a magnetic toner which has superior low-temperature fixing performance and pressure roller anti-staining properties even in various forms of use, has been kept from image defects such as image non-uniformity even during long-time image reproduction and can achieve high-level image quality. In a magnetic toner having toner particles containing at least a binder resin and a magnetic material, the activation energy Ea (kJ/mol) that is determined from a shift factor aTin a master curve of the toner, prepared when 120&#xb0; C. is set as reference temperature, and the activation energy Eb (kJ/mol) that is determined from a shift factor aTin a master curve of the toner, prepared when 150&#xb0; C. is set as reference temperature, satisfy Expression (1), and the Ea is 110 kJ/mol or less:1.00&#x2266;Ea/Eb&#x3c;1.20&#x2003;&#x2003;(1).

A developing apparatus, a process cartridge and an image forming apparatus which form an image whose image density can be maintained, which form a fogged image and which form an image of uneven density within an acceptable range, even when the diameter of a developer carrying member is not more than 12 mm. The apparatus includes a developer carrying member whose outer diameter is in the range of 8 mm to 12 mm, and a magnetic mono-component developerhaving a saturation magnetization of in a range of 20 Am/kg to 37 Am/kg when the magnetic field of 79.6 kA/m (1000 oersteds) is applied, the magnetization of not less than 70% and not more than 80% of the saturation magnetization when the magnetic field is lowered to 55.7 kA/m (700 oersteds), and the magnetization of not less than 50% and not more than 62% of the saturation magnetization when the magnetic field is lowered to 39.8 kA/m (500 oersteds).

Developing apparatus including a cylindrical developer carrying member conveying a magnetic mono-component developer

In a magnetic toner having toner particles containing at least a binder resin and a magnetic material, the binder resin is chiefly composed of a resin having a polyester unit synthesized using as a catalyst a tin compound represented by the following Formula (1), and the magnetic material has a number-average particle diameter of form 0.1 &#x3bc;m to 0.3 &#x3bc;m:(RCOO)Sn&#x2003;&#x2003;Formula (1)wherein R represents an alkyl group having 5 to 15 carbon atoms. This magnetic toner can attain a stable image density without dependence on environment and enables formation of high-grade images over a long period of time without causing scratches of latent image bearing members.

In an image forming apparatus having at least an amorphous silicon photosensitive member, a magnetic toner developing means and a color developer developing means, the magnetic toner has a weight-average particle diameter (D) of from 4.0 &#x3bc;m to 10.0 &#x3bc;m and a ratio thereof to number-average particle diameter (D), D/D, of from 1.0 to 2.0, and the number of magnetic particles not passing through a mesh with an opening of 34 &#x3bc;m which are contained in the unit volume of the magnetic toner is from 3.5 to 105. This image forming apparatus can not easily cause faulty cleaning performance even in using the magnetic toner and the non-magnetic color toners in combination and has superior environmental stability and running stability even where toners made to have small particle diameter are used or process speed is high.

Image forming apparatus

A magnetic black toner comprising magnetic black toner particles containing at least a binder resin and a magnetic material. The toner has a weight-average particle diameter of from 5 &mgr;m to 12 &mgr;m, and the toner has, in its particles of 3 &mgr;m or more in diameter, at least 90% by number of particles with a circularity of 0.900 or more and has an average circularity of from 0.940 to 0.970. The magnetic material comprises iron oxide particles which have an average particle diameter of from 0.10 &mgr;m to 0.30 &mgr;m, contain titanium or a titanium compound in an amount of from 0.3% by weight to 1.5% by weight in terms of titanium, based on the total weight of the iron oxide particles, and have the ratio of the proportion of FeO to the total Fe content in 10% by weight from the particle surface, A %, to the proportion of FeO to the total Fe content in the remainder 90% by weight, B %, which satisfies the expression: 0.7&lE;A/B&lE;1.0. Also, an inorganic fine powder is externally added to the toner particle surfaces.

Magnetic black toner

A toner contains at least a bonding resin and a coloring agent, and has a weight mean particle size from 5 &mgr;m to 12 &mgr;m; not less than 90% by number of particles not less than 3 &mgr;m have a circularity &ldquo;a&rdquo; not less than 0.900; a cut ratio Z and a weight mean size X of the toner are related as: cut ratio Z&lE;5.3&times;X; and a relationship of particles Y having a circularity of not less than 0.950 and a weight mean size X is Y&gE;e &times;X where X is 5 to 12 &mgr;m.

Toner, process for producing toner image forming method and apparatus unit

A toner containing toner particles and an inorganic fine powder; the toner particles containing at least a binder resin, a colorant, a sulfur-containing resin, and a wax; the binder resin containing a hybrid resin component containing a vinyl type polymer unit and a polyester unit, and the sulfur-containing resin being a resin selected from the group consisting of sulfur-containing polymers and sulfur-containing copolymers

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Numazu, Japan

Tadashi Dojo