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

Claim 2

The developer according to Claim 1, wherein the magnetic carrier is a resin-coated magnetic carrier which comprises core particles comprising a binder resin and a metal oxide, and a resin coating the core particles.

Claim 3

The developer according to Claim 2, wherein the core particles of the resin-coated magnetic carrier contain 50 - 99 wt. % of the metal oxide.

Claim 4

The developer according to Claim 2 or 3, wherein the resin-coated magnetic carrier contains averagely at most 5 magnetic carrier particles/µm exposed to the surface thereof.

Claim 5

The developer according to Claim 2, wherein the binder resin comprises a thermosetting resin.

Claim 6

The developer according to Claim 2 or 5, wherein the core particles have been prepared by polymerizing a polymerizable monomer in the presence of a metal oxide.

Claim 7

The developer according to Claim 1, wherein (a) the magnetic carrier comprises resinous magnetic carrier core particles comprising at least two metal oxides and a binder resin, (b) the core particles contain 50 - 99 wt. % of the metal oxides in total, (c) the metal oxides include at least one ferromagnetic and at least one metal oxide having a higher resistivity than the ferromagnetic, (d) the ferromagnetic has a number-average particle size ra, and the higher-resistivity metal oxide has a number-average particle size rb satisfying rb/ra > 1.0, and (e) the ferromagnetic occupies 30 - 95 wt. % of the total metal oxides.

Claim 8

The developer according to Claim 1, wherein the toner has a weight-average particle size of 1 - 6 µm, and the magnetic carrier has a number-average particle size of 5 - 35 µm.

Claim 9

The developer according to Claim 8, wherein the magnetic carrier comprises core particles containing 50 - 95 wt. % of a ferromagnetic metal oxide, and the magnetic carrier has a magnetization at 1 kilo-oersted of 100 - 150 emu/cm³.

Claim 10

The developer according to Claim 1, wherein the toner has a weight-average particle size of 3 - 8 µm, and the magnetic carrier has a number-average particle size of 35 - 80 µm.

Claim 11

The developer according to Claim 10, wherein the magnetic carrier comprises core particles containing 30 - 60 wt. % of a ferromagnetic metal oxide, and the magnetic carrier has a magnetization at 1 kilo-oersted of 30 - 100 emu/cm³.

Claim 12

The developer according to Claim 7, wherein the ferromagnetic comprises magnetite.

Claim 13

The developer according to Claim 7, wherein the higher-resistivity metal oxide comprises hematite.

Claim 14

The developer according to Claim 7, wherein the ferromagnetic comprises magnetite, and the higher-resistivity metal oxide comprises hematite.

Claim 15

The developer according to Claim 1, further comprising inorganic fine powder having an average particle size of at most 0.2 µm as an external additive to the toner.

Claim 16

The developer according to Claim 1, further comprising organic fine powder having an average particle size of at most 0.2 µm as an external additive to the toner.

Claim 17

The developer according to Claim 1, further comprising inorganic fine powder having an average particle size of at most 0.2 µm and organic fine powder having an average particle size of at most 0.2 µm as external additives to the toner.

Claim 18

The developer according to Claim 16 to 17, wherein the organic fine powder comprises fine particles of a resin.

Claim 19

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

Claim 20

A developing method for developing an electrostatic image, comprising: (A) 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 1 - 10 µm, a number-average particle size D1 and such a particle size distribution that particles having size of at most D1/2 occupy at most 20 % by number and particles having sizes of at least D4x2 occupy at most 10 % by volume, and the magnetic carrier has a number-average particle size of 1 - 100 µm and contains at most 20 % by number of particles having sizes in the range of at most a half of the number-average particle size, the magnetic carrier has a resistivity of at least 1x10¹ ohm.cm and has a core having a resistivity of at least 1x10¹⁰ ohm.cm, and the magnetic carrier has a magnetization at 1 kilo-oersted of 30 - 150 emu/g, (B) forming a magnetic brush of the two-component type developer on the developer-carrying member, (C) causing the magnetic brush to contact a latent image-bearing member, and (D) 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 21

The developing method according to Claim 20, wherein the electrostatic image comprises a digital image.

Claim 22

The developing method according to Claim 20 or 21, wherein the electrostatic image is developed by a reversal development mode.

Claim 23

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 24

The developing method according to Claim 23, wherein the magnetic carrier is a resin-coated magnetic carrier which comprises core particles comprising a binder resin and a metal oxide, and a resin coating the core particles.

Claim 25

The developing method according to Claim 24, wherein the core particles of the resin-coated magnetic carrier contain 50 - 99 wt. % of the metal oxide.

Claim 26

The developing method according to Claim 24 or 25, wherein the resin-coated magnetic carrier contains averagely at most magnetic carrier particles 1 µm exposed to the surface thereof.

Claim 27

The developing method according to Claim 24, wherein the binder resincomprises a thermosetting resin.

Claim 28

The developing method according to Claim 24 or 27, wherein the core particles have been prepared by polymerizing a polymerizable monomer in the presence of a metal oxide.

Claim 29

The developing method according to Claim 20, wherein (a) the magnetic carrier comprises resinous magnetic carrier core particles comprising at least two metal oxides and a binder resin, (b) the core particles contain 50 - 99 wt. % of the metal oxides in total, (c) the metal oxides include at least one ferromagnetic and at least one metal oxide having a higher resistivity than the ferromagnetic, (d) the ferromagnetic has a number-average particle size ra, and the higher-resistivity metal oxide has a number-average particle size rb satisfying rb/ra > 1.0, and (e) the ferromagnetic occupies 30 - 95 wt. % of the total metal oxides.

Claim 30

The developing method according to Claim 20, wherein the toner has a weight-average particle size of 1 - 6 µm, and the magnetic carrier has a number-average particle size of 5 - 35 µm.

Claim 31

The developing method according to Claim 30, wherein the magnetic carrier comprises core particles containing 50 - 95 wt. % of a ferromagnetic metal oxide, and the magnetic carrier has a magnetization at 1 kilo-oersted of 100 - 150 emu/cm³.

Claim 32

The developing method according to Claim 20, wherein the toner has a weight-average particle size of 3 - 8 µm, and the magnetic carrier has a number-average particle size of 35 - 80 µm.

Claim 33

The developing method according to Claim 32, wherein the magnetic carrier comprises core particles containing 30 - 60 wt. % of a ferromagnetic metal oxide, and the magnetic carrier has a magnetization at 1 kilo-oersted of 30 - 100 emu/cm³.

Claim 34

The developing method according to Claim 29, wherein the ferromagnetic comprises magnetite.

Claim 35

The developing method according to Claim 29, wherein the higher-resistivity metal oxide comprises hematite.

Claim 36

The developing method according to Claim 29, wherein the ferromagnetic comprises magnetite, and the higher-resistivity metal oxide comprises hematite.

Claim 37

The developing method according to Claim 20, wherein the developer further comprises inorganic fine powder having an average particle size of at most 0.2 µm as an external additive to the toner.

Claim 38

The developing method according to Claim 20, wherein the developer further comprises organic fine powder having an average particle size of at most 0.2 µm as an external additive to the toner.

Claim 39

The developing method according to Claim 20, wherein the developer further comprises inorganic fine powder having an average particle size of at most 0.2 µm and organic fine powder having an average particle size of at most 0.2 µm as external additives to the toner.

Claim 40

The developing method according to Claim 38 to 39, wherein the organic fine powder comprises fine particles of a resin.

Claim 41

The developing method according to Claim 20, wherein the toner comprises a non-magnetic toner.

Claim 42

An image forming method, comprising: (A1) 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 1 - 10 µm, a number-average particle size D1 and such a particle size distribution that particles having size of at most D1/2 occupy at most 20 % by number and particles having sizes of at least D4x2 occupy at most 10 % by volume, and the magnetic carrier has a number-average particle size of 1 - 100 µm and contains at most 20 % by number of particles having sizes in the range of at most a half of the number-average particle size, the magnetic carrier has a resistivity of at least 1x10¹ ohm.cm and has a core having a resistivity of at least 1x10¹⁰ ohm.cm, and the magnetic carrier has a magnetization at 1 kilo-oersted of 30 - 150 emu/g, (B1) forming a magnetic brush of the two-component type developer on the developer-carrying member, (C1) causing the magnetic brush to contact a latent image-bearing member, and (D1) 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; (A2) 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 1 - 10 µm, a number-average particle size D1 and such a particle size distribution that particles having size of at most D1/2 occupy at most 20 % by number and particles having sizes of at least D4x2 occupy at most 10 % by volume, and the magnetic carrier has a number-average particle size of 1 - 100 µm and contains at most 20 % by number of particles having sizes in the range of at most a half of the number-average particle size, the magnetic carrier has a resistivity of at least 1x10¹ ohm.cm and has a core having a resistivity of at least 1x10¹⁰ ohm.cm, and the magnetic carrier has a magnetization at 1 kilo-oersted of 30 - 150 emu/g, (B2) forming a magnetic brush of the two-component type developer on the developer-carrying member, (C2) causing the magnetic brush to contact a latent image-bearing member, and (D2) 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; (A3) 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 1 - 10 µm, a number-average particle size D1 and such a particle size distribution that particles having size of at most D1/2 occupy at most 20 % by number and particles having sizes of at least D4x2 occupy at most 10 % by volume, and the magnetic carrier has a number-average particle size of 1 - 100 µm and contains at most 20 % by number of particles having sizes in the range of at most a half of the number-average particle size, the magnetic carrier has a resistivity of at least 1x10¹ ohm.cm and has a core having a resistivity of at least 1x10¹⁰ ohm.cm, and the magnetic carrier has a magnetization at 1 kilo-oersted of 30 - 150 emu/g, (B3) forming a magnetic brush of the two-component type developer on the developer-carrying member, (C3) causing the magnetic brush to contact a latent image-bearing member, and (D3) 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; (E) forming a full color image with at least the above-formed magenta toner image, cyan toner image and yellow toner image.

Claim 43

The image forming method according to Claim 42, wherein the electrostatic image comprises a digital image.

Claim 44

The image forming method according to Claim 42 or 43, wherein the electrostatic image is developed by a reversal development mode.

Claim 45

The image forming method according to Claim 42, wherein the magnetic brush contacts the latent image-bearing member with a developing nip of 3 - 8 mm.

Claim 46

The image forming method according to Claim 42, wherein the magnetic carrier is a resin-coated magnetic carrier which comprises core particles comprising a binder resin and a metal oxide, and a resin coating the core particles.

Claim 47

The image forming method according to Claim 46, wherein the core particles of the resin-coated magnetic carrier contain 50 - 99 wt. % of the metal oxide.

Claim 48

The image forming method according to Claim 46 or 47, wherein the resin-coated magnetic carrier contains averagely at most 5 magnetic carrier particles/µm exposed to the surface thereof.

Claim 49

The image forming method according to Claim 46, wherein the binder comprises a thermosetting resin.

Claim 50

The image forming method according to Claim 46 or 47, wherein the core particles have been prepared by polymerizing a polymerizable monomer in the presence of a metal oxide.

Claim 51

The image forming method according to Claim 42, wherein (a) the magnetic carrier comprises resinous magnetic carrier core particles comprising at least two metal oxides and a binder resin, (b) the core particles contain 50 - 99 wt. % of the metal oxides in total, (c) the metal oxides include at least one ferromagnetic and at least one metal oxide having a higher resistivity than the ferromagnetic, (d) the ferromagnetic has a number-average particle size ra, and the higher-resistivity metal oxide has a number-average particle size rb satisfying rb/ra > 1.0, and (e) the ferromagnetic occupies 30 - 95 wt. % of the total metal oxides.

Claim 52

The image forming method according to Claim 42, wherein the toner has a weight-average particle size of 1 - 6 µm, and the magnetic carrier has a number-average particle size of 5 - 35 µm.

Claim 53

The image forming method according to Claim 52, wherein the magnetic carrier comprises core particles containing 50 - 95 wt. % of a ferromagnetic metal oxide, and the magnetic carrier has a magnetization at 1 kilo-oersted of 100 - 150 emu/cm³.

Claim 54

The image forming method according to Claim 42, wherein the toner has a weight-average particle size of 3 - 8 µm, and the magnetic carrier has a number-average particle size of 35 - 80 µm.

Claim 55

The image forming method according to Claim 54, wherein the magnetic carrier comprises core particles containing 30 - 60 wt. % of a ferromagnetic metal oxide, and the magnetic carrier has a magnetization at 1 kilo-oersted of 30 - 100 emu/cm³.

Claim 56

The image forming method according to Claim 51, wherein the ferromagnetic comprises magnetite.

Claim 57

The image forming method according to Claim 51, wherein the higher-resistivity metal oxide comprises hematite.

Claim 58

The image forming method according to Claim 51, wherein the ferromagnetic comprises magnetite, and the higher-resistivity metal oxide comprises hematite.

Claim 59

The image forming method according to Claim 42, wherein the developer further comprises inorganic fine powder having an average particle size of at most 0.2 µm as an external additive to the toner.

Claim 60

The image forming method according to Claim 42, wherein the developer further comprises organic fine powder having an average particle size of at most 0.2 µm as an external additive to the toner.

Claim 61

The image forming method according to Claim 42, wherein the developer further comprises inorganic fine powder having an average particle size of at most 0.2 µm and organic fine powder having an average particle size of at most 0.2 µm as external additives to the toner.

Claim 62

The image forming method according to Claim 60 to 61, wherein the organic fine powder comprises fine particles of a resin.

Claim 63

The image forming method according to Claim 42, wherein the toner comprises a non-magnetic toner.