Two-component type developer, developing method and image forming method

Claim 2

A two-component type developer for developing an electrostatic image, comprising: at least a toner and a magnetic carrier; wherein the toner has a weight-average particle size D4 of at most 10 µm and a number-average particle size D1 satisfying D4/D1 ≦ 1.5; and the magnetic carrier comprises composite particles comprising magnetic iron compound particles, non-magnetic metal oxide particles, and a binder comprising a phenolic resin; the composite particles containing the magnetic iron compound and the non-magnetic metal oxide in a total proportion of 80 - 99 wt. %; the magnetic iron compound particles having a number-average particle size ra, the non-magnetic metal oxide particles having a number-average particle size r b satisfying r b /r a > 1.0.

Claim 3

The developer according to Claim 1, wherein the magnetic iron compound particles have a number-average particle size r a of 0.02 - 5 µm, and the non-magnetic metal oxide particles have a number-average particle size r b of 0.05 - 10 µm.

Claim 4

The developer according to Claim 1 or 2, wherein the non-magnetic metal oxide particles are contained in an amount of 5 - 70 wt. % of the total of the magnetic iron compound particles and the non-magnetic metal oxide particles, and the magnetic carrier has a bulk density of 1.0 - 2.0 g/cm³.

Claim 5

The developer according to Claim 1 wherein the magnetic carrier is surface-coated with a resin containing the non-magnetic metal oxide particles.

Claim 6

The developer according to Claim 1 or 4, wherein the magnetic carrier is surface-coated with 0.1 - 10 wt. % of a resin.

Claim 7

The developer according to Claim 1, wherein the magnetic carrier has a saturation magnetization σ s of 10 - 80 emu/g.

Claim 8

The developer according to Claim 1, wherein the magnetic iron compound comprises magnetite and the non-magnetic metal oxide comprises hematite.

Claim 9

The developer according to Claim 1, wherein the toner is a non-magnetic toner.

Claim 10

The developer according to Claim 1, wherein the magnetic carrier contains the magnetic iron compound particles and the non-magnetic metal oxide particles in such a distribution that a total volume Pa1 of magnetic iron compound particles and a total volume Pb1 of non-magnetic metal oxide particles respectively appearing in an inside part of a carrier (core) particle section, and a total volume Pa2 of magnetic iron compound particles and a total volume Pb2 of non-magnetic metal oxide particles respectively appearing at a surface part of the carrier (core) particle section are set to satisfy Pb1/Pa1 < 1 and Pb2/Pa2 > 1, so as to provide a higher resistivity.

Claim 11

The developer according to Claim 1, wherein the magnetic carrier comprises a carrier core coated with 0.5 - 10 wt. % of a coating material.

Claim 12

The developer according to Claim 10, wherein the magnetic carrier comprises a carrier core coated with 0.6 - 5 wt. % of a coating material.

Claim 13

The developer according to Claim 1, wherein the magnetic carrier has a sphericity of at most 2.

Claim 14

A developing method for developing an electrostatic image, comprising: carrying a two-component type developer by a developer-carrying member enclosing therein a magnetic field generating means, said two-component type developer comprising a toner and a magnetic carrier; wherein the toner has a weight-average particle size D4 of at most 10 µm and a number-average particle size D1 satisfying D4/D1 ≦ 1.5; and the magnetic carrier comprises composite particles comprising magnetic iron compound particles, non-magnetic metal oxide particles, and a binder comprising a phenolic resin; the composite particles containing the magnetic iron compound and the non-magnetic metal oxide in a total proportion of 80 - 99 wt. %; the magnetic iron compound particles having a number-average particle size ra, the non-magnetic metal oxide particles having a number-average particle size r b satisfying r b /r a > 1.0. forming a magnetic brush of the two-component type developer on the developer-carrying member, causing the magnetic brush to contact a latent image-bearing member, and developing an electrostatic image on the latent image-bearing member to form a toner image while applying an alternating electric field to the developer-carrying member.

Claim 15

A developing method for developing an electrostatic image, comprising: carrying a two-component type developer by a developer-carrying member enclosing therein a magnetic field generating means, said two-component type developer comprising a toner and a magnetic carrier; wherein the toner has a weight-average particle size D4 of at most 10 µm and a number-average particle size D1 satisfying D4/D1 ≦ 1.5; and the magnetic carrier comprises composite particles comprising magnetic iron compound particles, non-magnetic metal oxide particles, and a binder comprising a phenolic resin; the composite particles containing the magnetic iron compound and the non-magnetic metal oxide in a total proportion of 80 - 99 wt. %; the magnetic iron compound particles having a number-average particle size ra, the non-magnetic metal oxide particles having a number-average particle size r b satisfying r b /r a > 1.0. forming a magnetic brush of the two-component type developer on the developer-carrying member, causing the magnetic brush to contact a latent image-bearing member, and developing an electrostatic image on the latent image-bearing member to form a toner image while applying an alternating electric field to the developer-carrying member.

Claim 16

The developing method according to Claim 13, wherein the electrostatic image comprises a digital image.

Claim 17

The developing method according to Claim 13 or 14, wherein the electrostatic image is developed by a reversal development mode.

Claim 18

The developing method according to Claim 20, wherein the magnetic brush contacts the latent image-bearing member with a developing nip of 3 - 8 mm.

Claim 19

The developing method according to Claim 13, wherein the magnetic iron compound particles have a number-average particle size r a of 0.02 - 5 µm, and the non-magnetic metal oxide particles have a number-average particle size r b of 0.05 - 10 µm.

Claim 20

The developing method according to Claim 13 or 16, wherein the non-magnetic metal oxide particles are contained in an amount of 5 - 70 wt. % of the total of the magnetic iron compound particles and the non-magnetic metal oxide particles, and the magnetic carrier has a bulk density of 1.0 - 2.0 g/cm³.

Claim 21

The developing method according to Claim 13, wherein the magnetic carrier is surface-coated with a resin containing the non-magnetic metal oxide particles.

Claim 22

The developing method according to Claim 13, wherein the magnetic carrier is surface-coated with 0.1 - 10 wt. % of a resin.

Claim 23

The developing method according to Claim 13, wherein the magnetic carrier has a saturation magnetization σ S of 10 - 80 emu/g.

Claim 24

The developing method according to Claim 13, wherein the magnetic iron compound comprises magnetite and the non-magnetic metal oxide comprises hematite.

Claim 25

The developing method according to Claim 13, wherein the toner is a non-magnetic toner.

Claim 26

The developing method according to Claim 13, wherein the magnetic carrier contains the magnetic iron compound particles and the non-magnetic metal oxide particles in such a distribution that a total volume Pa1 of magnetic iron compound particles and a total volume Pb1 of non-magnetic metal oxide particles respectively appearing in an inside part of a carrier (core) particle section, and a total volume Pa2 of magnetic iron compound particles and a total volume Pb2 of non-magnetic metal oxide particles respectively appearing at a surface part of the carrier (core) particle section are set to satisfy Pb1/Pa1 < 1 and Pb2/Pa2 > 1, so as to provide a higher resistivity.

Claim 27

The developing method according to Claim 13, wherein the magnetic carrier comprises a carrier core coated with 0.5 - 10 wt. % of a coating material.

Claim 28

The developing method according to Claim 24, wherein the magnetic carrier comprises a carrier core coated with 0.6 - 5 wt. % of a coating material.

Claim 29

The developing method according to Claim 13, wherein the magnetic carrier has a sphericity of at most 2.

Claim 30

An image forming method, comprising: (I) carrying a two-component type developer by a developer-carrying member enclosing therein a magnetic field generating means, said two-component type developer comprising a magenta toner and a magnetic carrier; wherein the magenta toner has a weight-average particle size D4 of at most 10 pm and a number-average particle size D1 satisfying D4/D1 ≦ 1.5; and the magnetic carrier comprises composite particles comprising magnetic iron compound particles, non-magnetic metal oxide particles, and a binder comprising a phenolic resin; the composite particles containing the magnetic iron compound and the non-magnetic metal oxide in a total proportion of 80 - 99 wt. %; the magnetic iron compound particles having a number-average particle size ra, the non-magnetic metal oxide particles having a number-average particle size r b satisfying r b /r a > 1.0. forming a magnetic brush of the two-component type developer on the developer-carrying member, causing the magnetic brush to contact a latent image-bearing member, and developing an electrostatic image on the latent image-bearing member to form a magenta toner image while applying an alternating electric field to the developer-carrying member; (II) carrying a two-component type developer by a developer-carrying member enclosing therein a magnetic field generating means, said two-component type developer comprising a cyan toner and a magnetic carrier; wherein the cyan toner has a weight-average particle size D4 of at most 10 µm and a number-average particle size D1 satisfying D4/D1 ≦ 1.5; and the magnetic carrier comprises composite particles comprising magnetic iron compound particles, non-magnetic metal oxide particles, and a binder comprising a phenolic resin; the composite particles containing the magnetic iron compound and the non-magnetic metal oxide in a total proportion of 80 - 99 wt. %; the magnetic iron compound particles having a number-average particle size ra, the non-magnetic metal oxide particles having a number-average particle size r b satisfying r b /r a > 1.0. forming a magnetic brush of the two-component type developer on the developer-carrying member, causing the magnetic brush to contact a latent image-bearing member, and developing an electrostatic image on the latent image-bearing member to form a cyan toner image while applying an alternating electric field to the developer-carrying member; (III) carrying a two-component type developer by a developer-carrying member enclosing therein a magnetic field generating means, said two-component type developer comprising a yellow toner and a magnetic carrier; wherein the yellow toner has a weight-average particle size D4 of at most 10 µm and a number-average particle size D1 satisfying D4/D1 ≦ 1.5; and the magnetic carrier comprises composite particles comprising magnetic iron compound particles, non-magnetic metal oxide particles, and a binder comprising a phenolic resin; the composite particles containing the magnetic iron compound and the non-magnetic metal oxide in a total proportion of 80 - 99 wt. %; the magnetic iron compound particles having a number-average particle size ra, the non-magnetic metal oxide particles having a number-average particle size r b satisfying r b /r a > 1.0. forming a magnetic brush of the two-component type developer on the developer-carrying member, causing the magnetic brush to contact a latent image-bearing member, and developing an electrostatic image on the latent image-bearing member to form a yellow toner image while applying an alternating electric field to the developer-carrying member; (IV) forming a full color image with at least the above-formed magenta toner image, cyan toner image and yellow toner image.

Claim 31

An image forming method, comprising: (I) carrying a two-component type developer by a developer-carrying member enclosing therein a magnetic field generating means, said two-component type developer comprising a magenta toner and a magnetic carrier; wherein the magenta toner has a weight-average particle size D4 of at most 10 pm and a number-average particle size D1 satisfying D4/D1 ≦ 1.5; and the magnetic carrier comprises composite particles comprising magnetic iron compound particles, non-magnetic metal oxide particles, and a binder comprising a phenolic resin; the composite particles containing the magnetic iron compound and the non-magnetic metal oxide in a total proportion of 80 - 99 wt. %; the magnetic iron compound particles having a number-average particle size ra, the non-magnetic metal oxide particles having a number-average particle size r b satisfying r b /r a > 1.0. forming a magnetic brush of the two-component type developer on the developer-carrying member, causing the magnetic brush to contact a latent image-bearing member, and developing an electrostatic image on the latent image-bearing member to form a magenta toner image while applying an alternating electric field to the developer-carrying member; (II) carrying a two-component type developer by a developer-carrying member enclosing therein a magnetic field generating means, said two-component type developer comprising a cyan toner and a magnetic carrier; wherein the cyan toner has a weight-average particle size D4 of at most 10 µm and a number-average particle size D1 satisfying D4/D1 ≦ 1.5; and the magnetic carrier comprises composite particles comprising magnetic iron compound particles, non-magnetic metal oxide particles, and a binder comprising a phenolic resin; the composite particles containing the magnetic iron compound and the non-magnetic metal oxide in a total proportion of 80 - 99 wt. %; the magnetic iron compound particles having a number-average particle size ra, the non-magnetic metal oxide particles having a number-average particle size r b satisfying r b /r a > 1.0. forming a magnetic brush of the two-component type developer on the developer-carrying member, causing the magnetic brush to contact a latent image-bearing member, and developing an electrostatic image on the latent image-bearing member to form a cyan toner image while applying an alternating electric field to the developer-carrying member; (III) carrying a two-component type developer by a developer-carrying member enclosing therein a magnetic field generating means, said two-component type developer comprising a yellow toner and a magnetic carrier; wherein the yellow toner has a weight-average particle size D4 of at most 10 µm and a number-average particle size D1 satisfying D4/D1 ≦ 1.5; and the magnetic carrier comprises composite particles comprising magnetic iron compound particles, non-magnetic metal oxide particles, and a binder comprising a phenolic resin; the composite particles containing the magnetic iron compound and the non-magnetic metal oxide in a total proportion of 80 - 99 wt. %; the magnetic iron compound particles having a number-average particle size ra, the non-magnetic metal oxide particles having a number-average particle size r b satisfying r b /r a > 1.0. forming a magnetic brush of the two-component type developer on the developer-carrying member, causing the magnetic brush to contact a latent image-bearing member, and developing an electrostatic image on the latent image-bearing member to form a yellow toner image while applying an alternating electric field to the developer-carrying member; (IV) forming a full color image with at least the above-formed magenta toner image, cyan toner image and yellow toner image.

Claim 32

The image forming method according to Claim 27, wherein the electrostatic image comprises a digital image.

Claim 33

The image forming method according to Claim 27 or 28, wherein the electrostatic image is developed by a reversal development mode.

Claim 34

The image forming method according to Claim 1, wherein the magnetic iron compound particles have a number-average particle size r a of 0.02 - 5 µm, and the non-magnetic metal oxide particles have a number-average particle size r b of 0.05 - 10 µm.

Claim 35

The image forming method according to Claim 27, wherein the non-magnetic metal oxide particles are contained in an amount of 5 - 70 wt. % of the total of the magnetic iron compound particles and the non-magnetic metal oxide particles, and the magnetic carrier has a bulk density of 1.0 - 2.0 g/cm³.

Claim 36

The image forming method according to Claim 27, wherein the magnetic carrier is surface-coated with a resin containing the non-magnetic metal oxide particles.

Claim 37

The image forming method according to Claim 27, wherein the magnetic carrier is surface-coated with 0.1 - 10 wt. % of a resin.

Claim 38

The image forming method according to Claim 27, wherein the magnetic carrier has a saturation magnetization σ S of 10 - 80 emu/g.

Claim 39

The image forming method according to Claim 27, wherein the magnetic iron compound comprises magnetite and the non-magnetic metal oxide comprises hematite.

Claim 40

The image forming method according to Claim 27, wherein the toner is a non-magnetic toner.

Claim 41

The image forming method according to Claim 27, wherein the magnetic carrier contains the magnetic iron compound particles and the non-magnetic metal oxide particles in such a distribution that a total volume Pa1 of magnetic iron compound particles and a total volume Pb1 of non-magnetic metal oxide particles respectively appearing in an inside part of a carrier (core) particle section, and a total volume Pa2 of magnetic iron compound particles and a total volume Pb2 of non-magnetic metal oxide particles respectively appearing at a surface part of the carrier (core) particle section are set to satisfy Pb1/Pa1 < 1 and Pb2/Pa2 > 1, so as to provide a higher resistivity.

Claim 42

The image forming method according to Claim 27, wherein the magnetic carrier comprises a carrier core coated with 0.5 - 10 wt. % of a coating material.

Claim 43

The image forming method according to Claim 38, wherein the magnetic carrier comprises a carrier core coated with 0.6 - 5 wt. % of a coating material.

Claim 44

The image forming method according to Claim 27, wherein the magnetic carrier has a sphericity of at most 2.