Developer and image forming device

Claim 2

A developer for developing electrostatic images, comprising a magnetic toner comprising a binder resin and magnetic powder, said developer containing 17 - 60 % by number of magnetic toner particles having a particle size of 5 microns or smaller, containing 1 - 23 % by number of magnetic toner particles having a particle size of 8 - 12.7 microns, and containing 2.0 % by volume or less of magnetic toner particles having a particle size of 16 microns or larger; wherein the magnetic toner has a volume-­average particle size of 4 - 9 microns, and the magnetic toner particles having a particle size of 5 microns or smaller has a particle size distribution satisfying the following formula: N/V = -0.04N + k, wherein N denotes the percentage by number of magnetic toner particles having a particle size of 5 micron or smaller, V denotes the percentage by volume of magnetic toner particles having a particle size of 5 microns or smaller, k denotes a positive number of 4.5 - 6.5, and N denotes a positive number of 17 - 60.

Claim 3

A developer according to Claim 1, wherein the magnetic toner has a true density of 1.45 - 1.70 g/cm³.

Claim 4

A developer according to Claim 1, wherein the magnetic toner has a true density of 1.50 - 1.65 g/cm³.

Claim 5

A developer according to Claim 1, wherein the magnetic toner contains 25 - 50 % by number of magnetic toner particles having a particle size of 5 microns or smaller.

Claim 6

A developer according to Claim 1, wherein the magnetic toner contains 30 - 50 % by number of magnetic toner particles having a particle size of 5 microns or smaller.

Claim 7

A developer according to Claim 1, wherein the magnetic toner contains 8 - 20 % by number of magnetic toner particles having a particle size of 8 - 12.7 microns.

Claim 8

A developer according to Claim 1, wherein the magnetic toner particles having a particle size of 5 microns or smaller satisfy the following formula: N/V = -0.04N + k, wherein k denotes a number of 4.5 - 6.0, and N denotes a number of 25 - 60.

Claim 9

A developer according to Claim 1, wherein the magnetic toner particles having a particle size of 5 microns or smaller satisfy the following formula: N/V = -0.04N + k, wherein k denotes a number of 4.5 - 5.5, and N denotes a number of 30 - 50.

Claim 10

A developer according to Claim 1, wherein the magnetic toner has a volume-average particle size of 4 - 8 microns.

Claim 11

A developer according to Claim 1, wherein the magnetic toner has a true density of 1.45 - 1.70 g/cm³, magnetic toner particles having a particle size of 8 - 12.7 microns are contained in an amount of 8 - 20 % by number, and the magnetic powder is contained in an amount of 60 - 110 wt. parts per 100 wt. parts of a resin component.

Claim 12

A developer according to Claim 10, wherein the magnetic powder is contained in an amount of 65 - 100 wt. parts per 100 wt. parts of the resin component.

Claim 13

A developer according to Claim 10, wherein the magnetic toner has a true density of 1.50 - 1.65 g/cm³.

Claim 14

A developer according to Claim 1, wherein the magnetic toner has a residual magnetization (σ r ) of 1 - 5 emu/g, a saturation magnetization (σ s ) of 20 - 40 emu/g and a coercive force (Hc) of 40 - 100 Öe.

Claim 15

A developer according to Claim 1, wherein the magnetic toner has been mixed with silica fine powder.

Claim 16

A developer according to Claim 14, wherein 0.01 - 8 wt. parts of the silica fine powder has been mixed with 100 wt. parts of the magnetic toner.

Claim 17

A developer according to Claim 14, wherein 0.1 - 5 wt. parts of the silica fine powder has been mixed with 100 wt. parts of the magnetic toner.

Claim 18

A developer according to Claim 14, wherein the magnetic toner has positive chargeability and the silica fine powder has positive chargeability.

Claim 19

A developer according to Claim 14, wherein the magnetic toner has negative chargeability and the silica fine powder has negative chargeability.

Claim 20

A developer according to Claim 1, wherein the magnetic toner has been mixed with powder of a fluorine-containing polymer.

Claim 21

A developer according to Claim 19, wherein the powder of the fluorine-containing polymer is contained in an amount of 0.01 - 2.0 wt. % based on the weight of the magnetic toner.

Claim 22

A developer according to Claim 19, wherein the powder of the fluorine-containing polymer is contained in an amount of 0.02 - 1.0 wt. % based on the weight of the magnetic toner.

Claim 23

A developer according to Claim 1, wherein the magnetic toner has been mixed with silica fine powder and powder of a fluorine-containing polymer.

Claim 24

An image forming device for developing electrostatic images held on an electrostatic image-­holding member, comprising: a developer chamber containing a developer for developing the electrostatic images, comprising a magnetic toner comprising a binder resin and magnetic powder, said developer containing 17 - 60 % by number of magnetic toner particles having a particle size of 5 microns or smaller, containing 1 - 23 % by number of magnetic toner particles having a particle size of 8 - 12.7 microns, and containing 2.0 % by volume or less of magnetic toner particles having a particle size of 16 microns or larger; wherein the magnetic toner has a volume-average particle size of 4 - 9 microns, and the magnetic toner particles having a particle size of 5 microns or smaller has a particle size distribution satisfying the following formula: N/V = -0.04N + k, wherein N denotes the percentage by number of magnetic toner particles having a particle size of 5 micron or smaller, V denotes the percentage by volume of magnetic toner particles having a particle size of 5 microns or smaller, k denotes a positive number of 4.5 - 6.5, and N denotes a positive number of 17 - 60; toner-carrying means having a surface to hold a toner layer thereon and to carry the toner layer to a developing zone; the toner layer being formed of the magnetic toner particles supplied from the developer chamber, said toner-carrying means being made of a non-­magnetic material; magnetic means for generating a stationary magnetic field at the developing zone through the non-­magnetic toner-carrying means toward the surface of the electrostatic image-holding member; means for forming the layer of the magnetic toner particles of substantially uniform thickness on the surface of the toner-carrying means; and means for maintaining a space between the toner-carrying means and the electrostatic image-­holding member at the developing zone within a predetermined range to form a space gap between the electostatic image-holding member and the surface of the layer of the magnetic toner particles on said toner-carrying means.

Claim 25

An image forming device for developing electrostatic images held on an electrostatic image-­holding member, comprising: a developer chamber containing a developer for developing the electrostatic images, comprising a magnetic toner comprising a binder resin and magnetic powder, said developer containing 17 - 60 % by number of magnetic toner particles having a particle size of 5 microns or smaller, containing 1 - 23 % by number of magnetic toner particles having a particle size of 8 - 12.7 microns, and containing 2.0 % by volume or less of magnetic toner particles having a particle size of 16 microns or larger; wherein the magnetic toner has a volume-average particle size of 4 - 9 microns, and the magnetic toner particles having a particle size of 5 microns or smaller has a particle size distribution satisfying the following formula: N/V = -0.04N + k, wherein N denotes the percentage by number of magnetic toner particles having a particle size of 5 micron or smaller, V denotes the percentage by volume of magnetic toner particles having a particle size of 5 microns or smaller, k denotes a positive number of 4.5 - 6.5, and N denotes a positive number of 17 - 60; toner-carrying means having a surface to hold a toner layer thereon and to carry the toner layer to a developing zone; the toner layer being formed of the magnetic toner particles supplied from the developer chamber, said toner-carrying means being made of a non-­magnetic material; magnetic means for generating a stationary magnetic field at the developing zone through the non-­magnetic toner-carrying means toward the surface of the electrostatic image-holding member; means for forming the layer of the magnetic toner particles of substantially uniform thickness on the surface of the toner-carrying means; and means for maintaining a space between the toner-carrying means and the electrostatic image-­holding member at the developing zone within a predetermined range to form a space gap between the electostatic image-holding member and the surface of the layer of the magnetic toner particles on said toner-carrying means.

Claim 26

An image forming device according to Claim 23, which further comprises means for applying an alternating electric field to the developing zone.

Claim 27

An image forming device according to Claim 23, wherein the developer comprises a mixture of the magnetic toner and silica fine powder.

Claim 28

A developer for developing electrostatic images comprising 17-60% by number of particles of size 5 microns or below, and 1-23% by number of toner particles of size 8-12.7 microns and 2% by volume or less of toner particles of size 16 microns or above.

Claim 29

A developer for developing electrostatic images comprising 17-60% by number of particles of size 5 microns or below, and 1-23% by number of toner particles of size 8-12.7 microns and 2% by volume or less of toner particles of size 16 microns or above.