Developing method and apparatus

Claim 2

A developing method, comprising: carrying magnetic particles and toner particles on a developer carrying member which is closely opposed to an electrostatic latent image bearing member; forming an electric field at a developing position where the electrostatic latent image bearing member and the developer carrying member are closely opposed to transfer the toner particles from the developer carrying member to the electrostatic latent image bearing member; wherein the following is satisfied: g₂ - g₁ < 0.25 where g₁ (mm) is a clearance between the latent image bearing member and the developer carrying member measured along a line G1 connecting a closest points therebetween, g₂ (mm) is a clearance between the latent image bearing member and the developer carrying member measured along a line G2 which is parallel with, and spaced by 2 mm from, the line G1.

Claim 3

A method according to claim 1, wherein g₂ - g₁ > 0.34.

Claim 4

A method according to claim 1, a peripheral speed of movement of the surface of the electrostatic latent image bearing member is 150 - 400 mm/sec.

Claim 5

A method according to claim 1, wherein the magnetic particles are contacted to the electrostatic latent image bearing member at the developing position, and wherein a volumetric ratio Vd of the total volume of the magnetic particles existing at the developing position to a volume of space defined by the surface of the electrostatic latent image bearing member and the developer carrying member at the developing position, is 1.5 - 30%.

Claim 6

A method according to claim 1, wherein said magnetic particles are each ferrite particle coated with resin.

Claim 7

A developing method, comprising: forming a layer of electrically charged toner particles on a surface of a developer carrying member and dispersing magnetic particles retaining on their surfaces electrically charged toner particles on the surface of the developer carrying member; carrying said particles on the developer carrying member to a developing position where a surface of an electrostatic latent image bearing member for bearing an electrostatic latent image is opposed with a clearance to the surface of the developer carrying member; applying an alternating electric field across the clearance and forming the magnetic particles into chains of the magnetic particles by magnetic field generating means disposed behind the developer carrying member; and developing the electrostatic latent image by the charged toner particles on the surface of the developer carrying member and on the surfaces of the magnetic particles.

Claim 8

A developing method, comprising: forming a layer of electrically charged toner particles on a surface of a developer carrying member and dispersing magnetic particles retaining on their surfaces electrically charged toner particles on the surface of the developer carrying member; carrying said particles on the developer carrying member to a developing position where a surface of an electrostatic latent image bearing member for bearing an electrostatic latent image is opposed with a clearance to the surface of the developer carrying member; applying an alternating electric field across the clearance and forming the magnetic particles into chains of the magnetic particles by magnetic field generating means disposed behind the developer carrying member; and developing the electrostatic latent image by the charged toner particles on the surface of the developer carrying member and on the surfaces of the magnetic particles.

Claim 9

A method according to claim 6, wherein the chains of the magnetic particles are contacted to the electrostatic latent image bearing member at the developing position, and wherein a volumetric ratio Vd of the total volume of the magnetic particles existing at the developing position to a volume of space defined by the surface of the electrostatic latent image bearing member and the developer carrying member at the developing position, is 1.5 - 30%.

Claim 10

A method according to claim 7, wherein the volumetric ratio Vd is 2.6 - 26%.

Claim 11

A method according to claim 7, wherein a total weight of the toner particles in the toner particle layer on the surface of the developer carrying member and the toner particles on the surfaces of the magnetic particles at the developing station is 4 -­40% of a weight of the magnetic particles in the developing position.

Claim 12

A method according to claim 7, wherein an amount of the developer carried on the developer carrying member including the toner particle layer, the toner particles on the surfaces of the magnetic particles and the magnetic particles is 0.5x10⁻²- 5x10⁻² g/cm².

Claim 13

A method according to claim 9, wherein an amount of the developer carried on the developer carrying member including the toner particle layer, the toner particles on the surfaces of the magnetic particles and the magnetic particles is 0.5x10⁻² - 5x10⁻² g/cm².

Claim 14

A method according to claim 6, wherein the toner particle layer, the toner particles on the surfaces of the magnetic particles and the magnetic particles carried to the developing position is applied onto the surface of the developer carrying member from a developer container containing mixed toner particles and magnetic particles, with a regulation by a developer regulating member disposed opposed to the surface of the developer carrying member, and wherein said volumetric ratio Vd and a volumetric ratio V of the magnetic particles in a region immediately before the developer goes out of the container, satisfy: 0.1 ≦ Vd/V ≦ 1.0.

Claim 15

A method according to claim 12, wherein Vd/V satisfies 0.2 ≦ Vd/V ≦ 0.8.

Claim 16

A method according to claim 12, wherein volumetric ratio V is not less than 20%.

Claim 17

A method according to claim 14, wherein the volumetric ratio Vd is 1.5 - 30%, wherein chains of the magnetic particles are contacted to the surface of the electrostatic latent image bearing member at the developing position.

Claim 18

A method according to claim 6, wherein an amount of the charged toner particles in the toner particle layer is not less than 0.05x10⁻³ g/cm² and not more than 1.0x10⁻³ g/cm².

Claim 19

A method according to claim 16, wherein an amount of the toner particles in the toner particle layer is not less than 0.1x10⁻³g/cm² and not more than 0.6x10⁻³ g/cm².

Claim 20

A method according to claim 16, wherein a thickness of the toner particle layer is 1/50 - 1/5 of the clearance between the surface of the electrostatic latent image bearing member and the surface of the developer carrying member at the developing position.

Claim 21

A method according to claim 16, wherein the chains of the magnetic particles are contacted to the electrostatic latent image bearing member at the developing position, and wherein a volumetric ratio Vd of the total volume of the magnetic particles existing at the developing position to a volume of space defined by the surface of the electrostatic latent image bearing member and the developer carrying member at the developing position, is 1.5 - 30%.

Claim 22

A method according to claim 6, wherein a weight ratio between the toner particles in the toner particle layer and the toner particles on the surfaces of the magnetic particles is 2:1 - 1:10.

Claim 23

A method according to claim 20, wherein the weight ratio is 1:1 - 1:5.

Claim 24

A method according to claim 20, wherein the chains of the magnetic particles are contacted to the electrostatic latent image bearing member at the developing position, and wherein a volumetric ratio Vd of the total volume of the magnetic particles existing at the developing position to a volume of space defined by the surface of the electrostatic latent image bearing member and the developer carrying member at the developing position, is 1.5 - 30%.

Claim 25

A method according to claim 16, wherein a weight ratio between the toner particles in the toner particle layer and the toner particles on the surfaces of the magnetic particles is 2:1 - 1:10.

Claim 26

A method according to claim 6, wherein a peripheral speed of movement of the developer carrying member is 0.8 - 1.5 times a peripheral speed of movement of the electrostatic latent image bearing member.

Claim 27

A method according to claim 24, wherein the chains of the magnetic particles are contacted to the electrostatic latent image bearing member at the developing position, and wherein a volumetric ratio Vd of the total volume of the magnetic particles existing at the developing position to a volume of space defined by the surface of the electrostatic latent image bearing member and the developer carrying member at the developing station, is 1.5 - 30%.

Claim 28

A method according to claim 13, wherein said magnetic particles are each ferrite particle coated with resin.

Claim 29

A method according to claim 1, wherein said magnetic particles are each ferrite particle coated with resin.

Claim 30

A developing apparatus for developing an electrostatic latent image on an electrostatic latent image bearing member, comprising: a container for containing a developer which contains toner particles and magnetic particles; a developer carrying member, opposed to the electrostatic latent image bearing member, for forming a developing position for supplying the toner particles to the latent image bearing member and for carrying the developer from said container to the developing position; first magnetic field generating means disposed across said developer carrying member from the latent image bearing member for generating a magnetic field to contact the magnetic particles to the latent image bearing member at the developing position; developer regulating means, disposed upstream of the developing position with respect to movement of a surface of said developer carrying member and spaced apart from the surface of said developer carrying member, for regulating the developer carried to the developing position; second magnetic field generating means, disposed across said developer carrying member from said regulating member and disposed upstream of said developer regulating member with respect to the movement; and alternating electric field generating means for forming an alternating electric field at the developing position to transfer at least the toner particles carried on said developer carrying member to the latent image bearing member; wherein a volumetric ratio Vd of the total volume of the magnetic particles existing at the developing position to a volume of space defined by the surface of the electrostatic latent image bearing member and the developer carrying member at the developing position, is 1.5 - 30%.

Claim 31

A developing apparatus for developing an electrostatic latent image on an electrostatic latent image bearing member, comprising: a container for containing a developer which contains toner particles and magnetic particles; a developer carrying member, opposed to the electrostatic latent image bearing member, for forming a developing position for supplying the toner particles to the latent image bearing member and for carrying the developer from said container to the developing position; first magnetic field generating means disposed across said developer carrying member from the latent image bearing member for generating a magnetic field to contact the magnetic particles to the latent image bearing member at the developing position; developer regulating means, disposed upstream of the developing position with respect to movement of a surface of said developer carrying member and spaced apart from the surface of said developer carrying member, for regulating the developer carried to the developing position; second magnetic field generating means, disposed across said developer carrying member from said regulating member and disposed upstream of said developer regulating member with respect to the movement; and alternating electric field generating means for forming an alternating electric field at the developing position to transfer at least the toner particles carried on said developer carrying member to the latent image bearing member; wherein a volumetric ratio Vd of the total volume of the magnetic particles existing at the developing position to a volume of space defined by the surface of the electrostatic latent image bearing member and the developer carrying member at the developing position, is 1.5 - 30%.

Claim 32

An apparatus according to claim 28, further comprising developer circulation limiting means disposed upstream of said regulating member with respect to the movement and cooperable with said developer carrying means to form a clearance therewith having a sectional area gradually decreasing toward said regulating member from an upstream side, wherein said second magnetic field means is opposed to said limiting member.

Claim 33

An apparatus according to claim 29, wherein an angle ϑ formed between a regulating portion of said developer regulating member and said second magnetic field generating means as seen from a center of rotation of said developer carrying member is not less than 2 degrees and not more than 15 degrees.

Claim 34

An apparatus according to claim 29, wherein in a region defined by said limiting member and said developer carrying member, an amount of the magnetic particles is larger than that in the other region in said developer container, and wherein a volumetric ratio V of the magnetic particles in the defined region satisfies: 0.1 ≦ Vd/V ≦ 1.0.

Claim 35

An apparatus according to claim 28, wherein an amount of the toner particles applied on said developer carrying member is not less than 0.05x10⁻³ g/cm² and not more than 1.0x10⁻³ g/cm².

Claim 36

An apparatus according to claim 29, wherein an amount of the toner particles applied on said developer carrying member is not less than 0.05x10⁻³ g/cm² and not more than 1.0x10⁻³ g/cm².

Claim 37

Apparatus according to claim 28, wherein a weight ratio between the toner particles in the toner particle layer and the toner particles on the surfaces of the magnetic particles is 2:1 - 1:10.

Claim 38

Apparatus according to claim 29, wherein a weight ratio between the toner particles in the toner particle layer and the toner particles on the surfaces of the magnetic particles is 2:1 - 1:10.

Claim 39

Apparatus according to claim 32, wherein a weight ratio between the toner particles in the toner particle layer and the toner particles on the surfaces of the magnetic particles is 2:1 - 1:10.

Claim 40

Apparatus according to claim 33, wherein a weight ratio between the toner particles in the toner particle layer and the toner particles on the surfaces of the magnetic particles is 2:1 - 1:10.

Claim 41

A developing apparatus for developing an electrostatic latent image on an electrostatic latent image bearing member, comprising: a container for containing a developer which contains toner particles and magnetic particles; a developer carrying member, opposed to the electrostatic latent image bearing member, for forming a developing position for supplying the toner particles to the latent image bearing member and for carrying the developer from said container to the developing position; first magnetic field generating means disposed across said developer carrying member from the latent image bearing member for generating a magnetic field to supply the magnetic particles to the developing position; developer regulating means, disposed upstream of the developing position with respect to movement of a surface of said developer carrying member, for regulating the developer carried to the developing position; second magnetic field generating means disposed across said developer carrying member from said regulating member and disposed upstream of said developer regulating member with respect to the movement; and a guiding member having a surface for guiding the developer, the guiding surface forming with said developer carrying member a clearance which gradually decreases from an upstream side of said developer regulating means with respect to the movement toward said developer regulating means, wherein said second magnetic field generating means has a maximum magnetic field generating portion which is opposed to the developer guiding surface.

Claim 42

A developing apparatus for developing an electrostatic latent image on an electrostatic latent image bearing member, comprising: a container for containing a developer which contains toner particles and magnetic particles; a developer carrying member, opposed to the electrostatic latent image bearing member, for forming a developing position for supplying the toner particles to the latent image bearing member and for carrying the developer from said container to the developing position; first magnetic field generating means disposed across said developer carrying member from the latent image bearing member for generating a magnetic field to supply the magnetic particles to the developing position; developer regulating means, disposed upstream of the developing position with respect to movement of a surface of said developer carrying member, for regulating the developer carried to the developing position; second magnetic field generating means disposed across said developer carrying member from said regulating member and disposed upstream of said developer regulating member with respect to the movement; and a guiding member having a surface for guiding the developer, the guiding surface forming with said developer carrying member a clearance which gradually decreases from an upstream side of said developer regulating means with respect to the movement toward said developer regulating means, wherein said second magnetic field generating means has a maximum magnetic field generating portion which is opposed to the developer guiding surface.

Claim 43

An apparatus according claim 38, wherein said developer regulating means and said guiding member are integrally formed, and wherein a length of the guiding surface measured along a direction of the movement is not less than 5 mm and not more than 15 mm.

Claim 44

An apparatus according to claim 38, wherein said guiding surface is disposed above a horizontal plane including a rotational axis of said developer carrying member, and extends across a vertical plane including the rotational axis.

Claim 45

An apparatus according to claim 40, wherein said developer regulating means is disposed in that quadrant in coordinates defined by the horizontal and vertical planes which is above the vertical plane and in which movement of the surface of said developer carrying member contains a downward component, and said developer regulating means has a regulating edge spaced from the surface of said developer carrying member, wherein an angle between the guiding surface and a tangential plane to the surface of said developer carrying member at a position where the regulating edge is opposed to the surface, measured from the tangential plane in a direction upwardly away therefrom, is more than 0 degree and not more than 45 degrees.

Claim 46

An apparatus according to claim 38, wherein said second magnetic field generating means is a magnetic pole providing a maximum magnetic flux density of not less than 600 Gausses, and wherein an angle formed between a position where the maximum magnetic flux density is formed and that end of the guiding surface which is upstream with respect to the movement as seen from a rotational axis of said developer carrying member is not less than 5 degrees.

Claim 47

An apparatus according to claim 41, wherein said second magnetic field generating means is a magnetic pole providing a maximum magnetic flux density of not less than 600 Gausses, and wherein an angle formed between a position where the maximum magnetic flux density is formed and that end of the guiding surface which is upstream with respect to the movement as seen from a rotational axis of said developer carrying member is not less than 5 degrees.

Claim 48

An apparatus according to claim 38, wherein the clearance formed between the guiding surface and the surface of said developer carrying member is larger than the clearance formed between the regulating edge of said developer regulating means and the surface of the developer carrying member, and wherein said guiding member and said developer regulating means are integral.

Claim 49

An apparatus according to claim 44, wherein said developer regulating means includes a non-magnetic blade, and wherein said guiding member includes a magnetic member adjacent said non-magnetic blade, and wherein said second magnetic field generating means is disposed upstream of said magnetic member with respect to the movement.

Claim 50

An apparatus according to claim 42, further comprising alternating electric field generating means for forming an alternating electric field at the developing position to transfer at least the toner particles carried on said developer carrying member to the latent image bearing member, wherein a volumetric ratio of the total volume of the magnetic particles existing at the developing position to a volume of space defined by the surface of the electrostatic latent image bearing member and the developer carrying member at the developing position, is 1.5 - 30%.

Claim 51

An apparatus according to claim 45, further comprising alternating electric field generating means for forming an alternating electric field at the developing position to transfer at least the toner particles carried on said developer carrying member to the latent image bearing member, wherein a volumetric ratio of the total volume of the magnetic particles existing at the developing position to a volume of space defined by the surface of the electrostatic latent image bearing member and the developer carrying member at the developing position, is 1.5 - 30%.