JPH10186863A - Method for magnetic brush developing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent from the fall of a solid image trailing end, the fall of the half tone trailing end on a boundary part between the solid image and the half tone, and a brush mark over a long period. SOLUTION: With respect to this method, by applying this method to a developing device provided with a photoreceptor 10 for forming an electrostatic latent image, a developing sleeve 14 capable of rotating, and driving means for letting the photoreceptor 10 rotated in order to force the developing sleeve 14 relatively shifted along the photoreceptor surface, the magnetic brush development is performed by rotating the photoreceptor 10 and the developing sleeve 14, and allowing the photoreceptor 10 on which the electrostatic latent image is formed, and the magnetic brush developer formed on the developing sleeve 14 while consisting of the toner and carriers to be rubbed. In this case, resistance of the magnetic brush developer layer per unit length in the shaft direction of the developing sleeve 14 is set to, 5.0×10<4> to 7.0×10<8> Ω/cm, under the electric field strength of 0.4V/μm, and 5.0×10<4> to 8.0×10<6> Ω/cm, under the electric field strength of 2.0V/μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic brush developing method in electrophotography and electrostatic recording.

[0002]

2. Description of the Related Art Conventionally, as a method of developing an electrostatic latent image formed on a photoreceptor, a developer layer is formed on a developing sleeve facing the photoreceptor, and then the photoreceptor and the developing sleeve are rotated. The mainstream is a magnetic brush development method in which toner adheres to an electrostatic latent image by sliding between a developer layer and the electrostatic latent image. The developer used in this magnetic brush developing method includes:
There is a one-component developer without using a carrier and a two-component developer composed of a toner and a carrier. The one-component developing method using a one-component developer has the advantage that the apparatus can be simplified and downsized, compared to the two-component developing method using a two-component developer, but the amount of toner transported and charged amount Is difficult to control. For these reasons,
Two-component developing methods are often used in high-definition full-color copying machines, printers, and the like that require precise control of the development amount.

In the two-component developing method, in order to secure a sufficient image density, that is, to supply a sufficient developer to a developing area, the developing sleeve and the photosensitive member are rotated in the forward direction, and the developing sleeve is rotated. Is generally used to set the peripheral speed of the photoconductor higher than the peripheral speed of the photoconductor. However, in this method, a development defect caused by a relative speed difference between the development sleeve and the photoconductor, for example, a solid image trailing edge dropout, and a solid image leading edge and a halftone trailing edge when a halftone and a solid image are mixed. It is known that the trailing edge of the halftone image occurs at the boundary of the image. These image omissions are due to the fact that the amount of change in the potential of the developer layer due to the movement of the toner in the development nip region depends on the latent image structure, and that the peripheral speed of the developing sleeve and the peripheral speed of the photoconductor have a speed difference. Therefore, it is considered that the region where the development is performed is developed by the developer affected by the electric field in the region immediately before this region, so that the region where the latent image structure is discontinuous as described above becomes remarkable. .

In order to suppress these defects,
Japanese Patent Publication No. 7-31422 proposes to reduce the resistance of a carrier. However, if the resistance of the carrier is excessively lowered, a so-called brush mark is generated due to a reduction in toner supply capacity of the developer to the photoconductor and occurrence of a latent image leak due to an extreme effect of the developing effective electrode to the photoconductor. Occurs.

In order to prevent the occurrence of the above-mentioned defects and brush marks, the lower limit of the resistance of the carrier layer is specified in Japanese Patent Publication Nos. 5-40309, 6-29992, and 7-31422. Have been. However, at present, the inventions described in these publications have not sufficiently improved the above-mentioned defects.

[0006]

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a method for removing a trailing edge of a solid image, a trailing edge of a halftone image at a boundary between a leading edge of a solid image and a trailing edge of a halftone, and An object of the present invention is to provide a magnetic brush developing method capable of forming a high-quality black-and-white and full-color image by preventing a drop in toner supply capability and a brush mark caused by a latent image leak for a long period of time.

[0007]

As a result of intensive studies, the present inventors have found that in the two-component developing method, the above problem can be solved by setting the resistance of the magnetic brush developer layer to a specific range. The present invention has been completed.

That is, according to the present invention, a photosensitive member for forming an electrostatic latent image, a rotatable developing sleeve, and at least one of the photosensitive member and the developing sleeve are moved so that the developing sleeve is exposed to light. The developing device is provided with a moving means for relatively moving along the surface of the body, and the developing sleeve is relatively moved along the surface of the photoreceptor and rotated to form an electrostatic latent image. A magnetic brush developer layer formed on the developing sleeve and formed of a two-component developer containing a toner and a magnetic carrier on the developing sleeve, the magnetic brush developing method comprising: The resistance of the magnetic brush developer layer was 5.0 × 1 under an electric field strength of 0.4 V / μm.
0 ⁴ ~7.0 × 10 ⁸ Ω, which lies in the range under the electric field strength of ^{2.0V / μm 5.0 × 10 4 ~8.0} × 10 6 Ω.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

In a developing apparatus to which the magnetic brush developing method of the present invention is applied, a photosensitive member for forming an electrostatic latent image, a rotatable developing sleeve, and at least one of the photosensitive member and the developing sleeve are moved. Moving means for relatively moving the developing sleeve along the surface of the photoconductor.

FIG. 1 shows a specific example of a main part of such a developing device.
~ 3. 1 to 3, the same components are denoted by the same reference numerals, and description thereof will be omitted. The developing device shown in FIG. 1 has a cylindrical photoreceptor 10, a developing housing 12 arranged to face the photoreceptor 10, a rotatable counterclockwise direction (direction of arrow A), and a built-in magnet. And a driving unit (not shown) for rotating the photosensitive member 10 in the forward direction with respect to the developing sleeve 14, that is, in the same direction as the clockwise direction (the direction of arrow B).

The developing housing 12 has a substantially box shape, and a slit-shaped opening is formed in the wall 12 A on the photoconductor 10 side along the axial direction of the photoconductor 10. The developing sleeve 14
The photoconductor 10 and the developing sleeve 14 are arranged such that the axial direction thereof is substantially parallel to the axial direction of the developing sleeve 14 and that a part of the outer peripheral portion is exposed from an opening formed in the wall 12A. Further, inside the developing housing 12, a developer (not shown), a toner supply means (not shown), an agitator (not shown) for stirring the supplied toner and the developer, and the like are arranged.

In this developing device, the developer is supplied to the developing sleeve 14 to form a magnetic brush developer layer on the developing sleeve 14, and the magnetic brush developer layer is transported to the opening as the developing sleeve 14 rotates. Here, the toner image is formed by the friction between the magnetic brush developer layer and the electrostatic latent image formed on the photoconductor 10. In the developing device of FIG. 1, the photosensitive member 10 and the developing sleeve 14 are driven so that their peripheral speeds are different from each other, and a driving unit for rotating the photosensitive member 10 is the moving unit.

In the developing device shown in FIG. 2, the photosensitive member 10, the developing housing 12, the developing sleeve 14, and the developing housing 12 are moved along the outer periphery of the photosensitive member 10 in the direction opposite to the clockwise direction (the direction of arrow C). And driving means (not shown) for performing the operation. By this driving means, the developing housing 12 is moved so that the wall 12A is always arranged on the photoconductor 10 side, and the driving means of the developing housing 12 serves as the moving means.

The developing device shown in FIG. 3 includes a plate-shaped photosensitive member 16 and
The developing housing 12, the developing sleeve 14, and the photoconductor 1
And a driving means (not shown) for moving the upper and lower parts 6 in the vertical direction. In the developing device of FIG. 3, the driving unit of the photoconductor 16 is the moving unit. In the developing device of FIG. 3, the developing sleeve 14 may be rotatable in the direction of arrow A and in the opposite direction, and exposure means may be provided on each of the upper and lower parts of the developing housing 12. In this case, when the developing sleeve 14 is rotating in the direction of arrow A,
6 is moved downward, and the upper exposure means is driven,
When the developing sleeve 14 is rotating in the direction opposite to the direction of arrow A, it is preferable to move the photoconductor 16 upward and drive the lower exposure means.

In the developing device shown in FIG. 3, the photosensitive member 16 is moved, but instead of moving the photosensitive member 16, the developing housing 12 may be moved in the vertical direction. When the exposure unit is provided on each of the upper and lower portions of the development housing 12, the exposure unit is moved integrally with the development housing 12, and when the development sleeve 14 is rotating in the direction opposite to the arrow A direction, By moving the developing housing 12 downward and driving the lower exposure means, the developing sleeve 1
When 4 is rotating in the direction of arrow A, it is preferable to move the developing housing 12 upward and drive the upper exposing means.

According to the magnetic brush developing method of the present invention, which is carried out by the above-described developing apparatus, the developing sleeve is relatively moved and rotated along the surface of the photoreceptor.
The photoreceptor having the electrostatic latent image formed thereon is rubbed against the magnetic brush developer layer formed on the developing sleeve and composed of a two-component developer containing a toner and a magnetic carrier. here,
The developing sleeve 14 is relatively moved along the surface of the photoconductor so as to have a peripheral speed relative to the surface of the photoconductor.

The magnetic carrier usable in the present invention can be a coated carrier having a resin coating layer on the surface of core particles.

As the core particles used in the present invention, known materials exhibiting ferromagnetism can be used.
Examples include magnetic metals such as steel, nickel, and cobalt, and magnetic oxides such as ferrite and magnetite. Among these, ferrite particles having a low specific gravity, which can suppress peeling of the resin coating layer and toner contamination on the carrier surface due to stress received in the developing device, are preferable.

As ferrite, Li, Mg, Ca,
Mn, Ni, Cu, the oxides of one or more elements selected from Zn and Fe ₂ O ₃ as a main component, those formed by granulation and sintering are preferable from the viewpoint of magnetization, L
i, Mg, mainly composed of the oxide and Fe ₂ O ₃ of 1 or more elements selected from Mn is more preferable from the viewpoint of compatibility between the magnetization and electric resistance.

The ferrite particles can be produced by a known production method. For example, a pulverized ferrite composition was mixed with a binder, water, a dispersant, an organic solvent, and the like, and particles were formed using a spray drying method or a fluidized granulation method, and the particles were fired by a rotary kiln or a batch incinerator. Thereafter, there is a method of classifying the particles by sieving to obtain ferrite particles having a particle size in a desired range. In the firing step, it is also possible to control the oxygen partial pressure, or to control the electrical resistance of the ferrite particles by adding oxidation or reduction treatment to the particle surface after firing.

The average particle diameter of the core particles thus produced is preferably 30 to 50 μm. When the average particle diameter of the core particles exceeds 50 μm, the toner concentration (100
× toner weight / magnetic carrier weight), the resistance of the developer tends to increase remarkably. Particularly, when the resistance of the magnetic brush developer layer is high (2.0 V / μm), the resistance of the developer increases. When the halftone and the solid image are mixedly close to each other, the trailing edge of the halftone image at the boundary portion between the leading edge of the solid image and the trailing edge of the halftone is unpreferably generated. On the other hand, if the average particle diameter of the core particles is less than 30 μm, the ears of the developer become too soft, the increase in the resistance value of the developer becomes rather large, and carrier over occurs, which is not preferable.

The magnetization (effective magnetization) at 1 kOe of the magnetic carrier is preferably 55 to 65 emu / g. The resistance of the developer layer depends on the state of ears of the magnetic brush, and tends to decrease as the magnetic flux density of the magnet incorporated in the developing sleeve and the effective magnetization of the magnetic carrier increase, and when the effective magnetization exceeds 65 emu / g. In addition, the brush of the developer becomes hard and a brush mark is generated, and if it is less than 55 emu / g, a carrier over or the like occurs, which is not preferable.

Further, in order to keep the resistance of the developer described later in a desired range, when a magnetic brush layer composed of core particles is formed on the developing sleeve, the unit length in the longitudinal direction (axial direction) of the developing sleeve is reduced. The resistance of the magnetic brush layer per
5.0 × 10 ^{3 to} 1.0 under an electric field strength of 0.4 V / μm
× 10 ⁶ Ω / cm, 5 in an electric field strength of 2.0 V / [mu] m.
It is preferably in the range of 0 × 10 ^{3 to} 6.0 × 10 ⁵ Ω / cm.

The matrix resin which can be used for the resin coating layer of the carrier can be selected from any resins which can be used in the art as the resin coating layer of the carrier. Two or more kinds may be used in combination.

Specifically, polyolefin resins such as polyethylene and polypropylene; polyvinyl and polyvinylidene resins such as polystyrene, acrylic resin, polyacrylonitrile and polyvinyl acetate;
Polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether, and polyvinyl ketone; vinyl chloride-vinyl acetate copolymer; styrene-acrylic acid copolymer; straight silicone resin comprising an organosiloxane bond or a modified product thereof; Resins, for example, polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polychlorotrifluoroethylene; polyester; polyurethane; polycarbonate;
For example, urea-formaldehyde resin, melamine resin,
Benzoguanamine resin, urea resin, polyamide resin;
Epoxy resin; a resin containing a urea bond and / or a urethane bond obtained by polymerizing at least one isocyanate compound and at least one compound selected from the group consisting of water, an amine compound and a polyol compound. Among these, a critical surface tension (γc) of 30 d is applied to a part or the whole of the matrix resin in order to minimize a change in resistance of the carrier surface due to toner contamination.
It is preferable to use a resin of yne / cm or less.

Resins having a critical surface tension of 30 dyne / cm or less include polyvinyl fluoride (γc = 28 dyne).
/ Cm), polyvinylidene fluoride (γc = 25 dyne)
/ Cm), polytrifluoroethylene (γc = 22 dy)
ne / cm), polytetrafluoroethylene (γc = 1)
8 dyne / cm), polyhexafluoropropylene (γc = 16 dyne / cm), etc., as well as vinylidene fluoride-acrylic copolymer, vinylidene fluoride-vinyl fluoride copolymer, tetrafluoroethylene and vinylidene fluoride, Critical surface tension of 35 dyn with fluoroterpolymer such as terpolymer with fluorinated monomer
e / cm or less, especially when the critical surface tension is 3
Resins, polymers and silicone resins containing 0 dyne / cm or less of fluorine are preferred.

The matrix resin has a critical surface tension of 30 dyn
When a resin of e / cm or less is contained, the content of the resin contained in the matrix resin is preferably 10% by weight or more.

From the viewpoint of obtaining a strong thin film which is difficult to peel off, at least one type of isocyanate compound is used.
A resin obtained by polymerization from at least one compound selected from the group consisting of water, an amine compound and a polyol compound is preferable.

As the isocyanate compound used for synthesizing such a resin, it is necessary to crosslink the resin and increase the strength of the resin. Therefore, a bifunctional or higher polyfunctional isocyanate compound is preferably used. Specifically, examples of the bifunctional isocyanate compound include hexamethylene diisocyanate such as trade name: “Sumidur H” (manufactured by Sumitomo Bayer Urethane Co., Ltd.) and trade name: “nafconate” (manufactured by National Aniline Co., Ltd.) Such as metaphenylene diisocyanate, trade name: "Suminate 80"
Toluylene diisocyanate (mixture of toluylene-2,4-diisocyanate and tolylene-2,6-diisocyanate) such as (Sumitomo Chemical Co., Ltd.) or "Hyrene TM" (Dupont), trade name: "Sumidur T""(Manufactured by Sumitomo Bayer Urethane Co., Ltd.), trade names: 3,3 'such as" Hilen H "(manufactured by DuPont) and" Suminate BT "(manufactured by Sumitomo Chemical Co., Ltd.) -Dimethyl-diphenyl-4,
4'-diisocyanate, trade name: "Millionate M
T "(manufactured by Nippon Polyurethane Industry Co., Ltd.) and" Isonate
Diphenylmethane diisocyanate, such as "125M" (manufactured by Kasei Upjohn) and "Sumidur 44S" (manufactured by Sumitomo Bayer Urethane), trade name: "Hylen D"
3,3'-Dimethyl-diphenylmethane-4,4'-diisocyanate, such as "M" (manufactured by DuPont), trade name: naphthalene diisocyanate, such as "Sumidur 15" (manufactured by Sumitomo Bayer Urethane Co.), trade name:
Examples include dicyclohexylmethane diisocyanate such as "Desmodur W" (manufactured by Sumitomo Bayer Urethane Co., Ltd.) and diphenyl ether diisocyanate such as "Suminate E" (manufactured by Sumitomo Chemical Co., Ltd.).

As the modified bifunctional isocyanate compound, for example, trade name: “Sumidur 44p
-90 "," Sumidule 3062 "," Sumidule PF "," Sumidule CD "," Sumidule 063 "
2, "Sumijur PC" (above, manufactured by Sumitomo Bayer Urethane Co., Ltd.), "Coronate 2014", "Coronate A"
P "," Coronate 2501 "," Millionate MS-
50, "Coronate 3041" (all manufactured by Nippon Polyurethane Industry Co., Ltd.), "Duranate 24A-90CX",
"Duranate EXPD-101" (all manufactured by Asahi Kasei Corporation), "Takenate M-402", "Takenate F-
513 "," Takenate D-102 "," Takenate L
-1150 "(all manufactured by Takeda Pharmaceutical Co., Ltd.).

Examples of the trifunctional isocyanate compound include hexamethylene diisocyanate adducts such as trade name “Sumidur N” (manufactured by Sumitomo Bayer Urethane Co.) and trade name: “Sumidur L” (Sumitomo Bayer Urethane) Reaction products of toluylene isocyanate and trimethylolpropane, such as "Coronate L" (manufactured by Nippon Polyurethane Industry Co., Ltd.), and trimethylolpropane (trade name) such as "Sumidur R" (manufactured by Sumitomo Bayer Urethane Co., Ltd.) Reaction product of hexamethylene diisocyanate and trimethylolpropane such as phenylmethane-triisocyanate, trade name: "Coronate HL" (manufactured by Nippon Polyurethane Industry Co., Ltd.), trade name: "Desmodur EH"
Hexamethylene diisocyanate adduct such as (manufactured by Sumitomo Bayer Urethane Co., Ltd.), trade name: “Isonate1
43L "(manufactured by Kasei UpJohn Co., Ltd.), diphenylmethine diisocyanate cycloadduct, trade name:" T-
2-isocyanatoethyl-2,6-diisocyanate hexanoate such as "100" (manufactured by Toray Industries, Inc.). As the modified trifunctional isocyanate compound, trade name: “Takenate D-110N”
(Manufactured by Takeda Pharmaceutical Co., Ltd.).

Examples of the polyfunctional isocyanate compound having more than three functionalities include a compound represented by the following formula.

[0034]

Embedded image

Further, adducts of diphenylmethane diisocyanate with a polyhydric polyol, adducts of toluylene diisocyanate with a polyhydric polyol and the like can also be mentioned.

Although these do not exist as pure products, commercially available products containing difunctional and trifunctional or higher functional isocyanate compounds include, for example, “Sumidur 4
4V-10 "," Sumidule 44V-20 "," SB
U-Isocyanate0389 "(manufactured by Sumitomo Bayer Urethane Co., Ltd.)," Millionate MR "(manufactured by Nippon Polyurethane Industry Co., Ltd.)," PAPI135 "," PAP2 "
0 "(all manufactured by Kasei Upjohn Co., Ltd.) and the like.

As the isocyanate compound, a polyfunctional isocyanate having three or more functional groups is preferable from the viewpoint of improving the strength of the coating film.

As the water that reacts with the isocyanate compound, water having a low impurity content is preferable, and examples thereof include distilled water, ion-exchanged water, and ultrapure water.

The amine compound which reacts with the isocyanate compound is preferably one having two or more functionalities, and examples thereof include the following.

Examples of the bifunctional amine compound include ethylenediamine, hexamethylenediamine, phenylenediamine, xylylenediamine, diaminocyclohexane, piperazine, 4,4'-diaminodiphenylmethane,
4'-diaminodiphenyl ether, 4,4'-diaminostilbene-2,2'-sulfonic acid and its sodium salt. Examples of the amine compound having three or more functionalities include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, iminobispropylamine, triaminobenzene, and a melamine monomer. Of these, amine compounds having three or more functionalities are preferred, and diethylene triamine and melamine monomers are particularly preferred.

Further, when the surface of the carrier has a low surface energy, an amine compound containing a fluorine component or a silicone component can be preferably used.

Examples of the amine compound containing a fluorine component include:
The following compounds can be exemplified.

[0043]

Embedded image

Examples of the amine compound containing a silicone component include the following compounds.

[0045]

Embedded image

An amine compound containing a fluorine component or a silicone component can be used even if it is monofunctional.

Examples of the polyol compound which reacts with the isocyanate compound include diol compounds such as ethylene glycol, propylene glycol, butylene glycol, hexamethylene glycol, neopentyl glycol, glycerin, trimethylolpropane, trimethylolethane, 1,2,6- Triol compounds such as hexanetriol and the like, pentaerythritol and the like can be mentioned, and diol compounds are particularly preferably used.

Further, a polyol compound containing a fluorine or silicone component can be preferably used.

Examples of the polyol compound containing a fluorine component include the following.

[0050]

Embedded image

Examples of the polyol compound containing a silicone component include the following.

[0052]

Embedded image

The polyol compound containing a fluorine component or a silicone component can be used even if it is monofunctional.

The compound selected from water, an amine compound and a polyol compound may be used alone, but two or more amine compounds, two or more polyol compounds, water and an amine compound, water and a polyol compound, and an amine compound And two or more kinds such as polyol compounds. Among these, a combination of an isocyanate compound and water is preferred.

The ratio of the isocyanate compound to the compound selected from water, an amine compound and a polyol compound is selected according to the required properties of the resin.
Since it is preferable from the viewpoint of maintaining storage stability that no unreacted compound remains, the isocyanate functional group generally reacts stoichiometrically with a functional group of a compound selected from water, an amine compound and a polyol compound. It is used in a small amount.

The weight ratio between the core particles and the matrix resin is 10
It can be in the range of 0: 0.01 to 100: 5.0. When the resin is obtained by polymerizing at least one isocyanate compound and at least one compound selected from the group consisting of water, an amine compound and a polyol compound, a uniform coating state is obtained even as a thin resin coating layer. And the crosslinked structure can provide sufficient strength, and therefore, can maintain the initial resistance for a long period of time, so that the thickness of the resin coating layer can be 0.5 μm or less, And the weight ratio of matrix resin to 10
It can be set in the range of 0: 0.01 to 100: 0.5.

In other resins, the weight ratio between the core particles and the matrix resin is preferably from 100: 1.5 to 100: 5.0. If the total weight of the matrix resin is less than 1.5 parts by weight with respect to 100 parts by weight of the core particles, the electric field dependency of the magnetic brush developer layer resistance becomes strong, and the high electric field (2.
(0 V / μm), the resistance becomes too low, and the brush mark is remarkably generated. On the other hand, when the total weight of the matrix resin exceeds 5.0 parts by weight with respect to 100 parts by weight of the core particles, the resistance of the magnetic brush developer layer under a high electric field (2.0 V / μm) becomes too high and the halftone In addition, when the solid image and the solid image are mixedly close to each other, the trailing edge of the halftone image at the boundary between the leading edge of the solid image and the trailing edge of the halftone image is notably generated.

Conductive fine particles may be dispersed in the resin coating layer. Specific examples of the conductive fine particles include metals such as gold, silver and copper; carbon black; semiconductive oxides such as titanium oxide and zinc oxide; titanium oxide, zinc oxide, barium sulfate, aluminum borate, and titanium. Potassium oxide powder or the like whose surface is covered with tin oxide, carbon black, metal or the like can be used. Among them, carbon black is preferable from the viewpoint of manufacturing stability, cost, and conductivity.
Known carbon black can be used,
Carbon black having a DBP (dibutyl phthalate) oil absorption of 50 to 300 ml / 100 g having good production stability is preferable. By adding conductive fine particles to the resin coating layer, the resistance of this resin coating layer can be reduced, so that the strength is not so strong, and therefore a resin that requires a thick resin coating layer is used as the matrix resin. It becomes possible. In addition, by enabling a thick resin coating layer, a cushioning effect is obtained, and even if stress is applied in the developing device, carrier surface contamination and wear of the resin coating layer are less likely to occur, and even if some wear occurs. It is possible to provide a developer in which the influence of the magnetic carrier on the resistance is small and the change in the resistance is extremely small even in long-term use.

The average particle size of the conductive fine particles is preferably 0.1 μm or less, and the primary particle size is preferably 50 nm or less for dispersion.

The volume occupancy of the conductive fine particles in the resin coating layer is preferably 7 to 15%. The following equation (1) is used to calculate the volume occupancy of the conductive fine particles in the resin coating layer.

[0061]

(Equation 1)

When the volume occupancy of the conductive fine particles in the resin coating layer is less than 7%, the resistance of the magnetic brush developer layer in a low electric field (0.4 V / μm) becomes too high, and the solid image and the non-image area have a high resistance. The trailing edge of the solid image at the boundary is remarkably undesired. If the volume occupancy exceeds 15%, the resistance of the magnetic brush developer layer in a high electric field (2.0 V / μm) becomes too low, and brush marks are remarkably generated.

The resin coating layer may further contain crosslinkable organic particles, magnetic fine particles, and the like for controlling charging and strengthening the coating.

As a method for producing a magnetic carrier, typically, a solution for forming a resin coating layer (including a matrix resin and, if necessary, resin fine particles and conductive fine particles in a solvent) is used. Specifically, for example, an immersion method in which the core particles are immersed in a solution for forming the resin coating layer, a spray method in which the solution for forming the resin coating layer is sprayed on the surface of the core particles, and the floating of the core particles by flowing air A fluidized-bed method of spraying a solution for forming a resin coating layer in such a state, and a kneader-coater method of mixing nucleus particles and a solution for forming a resin coating layer in a kneader coater and removing the solvent are exemplified.

The solvent used for the resin coating layer forming solution is
There is no particular limitation as long as it dissolves the matrix resin. For example, aromatic hydrocarbons such as toluene and xylene, ketones such as acetone and methyl ethyl ketone, and ethers such as tetrahydrofuran and dioxane can be used.

When a resin obtained by polymerizing an isocyanate compound and a compound selected from water, an amine compound and a polyol compound is used as the matrix resin, the isocyanate compound may be diluted with a solvent if necessary.
This and the core particles are mixed and stirred, and the solvent is removed if necessary. Next, a method in which a predetermined amount of a compound selected from water, an amine compound and a polyol compound is added, and the reaction is carried out by heating and stirring or standing as required, can also be used. When producing a magnetic carrier in which a low surface energy substance is unevenly distributed on the surface, a low surface energy compound such as a fluorine-containing amine compound or a fluorine-containing polyol compound can be added at the end of the above reaction. When obtaining a resin coating layer having a uniform composition in the depth direction, the isocyanate compound is diluted with a solvent as necessary,
To this, water, a compound selected from an amine compound and a polyol compound are added, and the mixture is stirred and the solvent is removed and reacted as needed, or the mixture is left standing and the solvent is removed and reacted as needed. Methods can also be used. Further, a method of preparing a magnetic carrier by mixing and stirring the core particles and the isocyanate compound in advance in a solution containing at least one of water, an amine compound and a polyol compound and reacting in a liquid can also be used.

The toner used in the present invention contains a colorant and a binder resin. As a colorant used in the toner,
Carbon black, nigrosine dye, aniline blue,
Calcoil Blue, Chrome Yellow, Ultramarine Blue, Dupont Oil Red, Quinoline Yellow, Methylene Blue Chloride, Phthalocyanine Blue, Malachite Green Oxalate, Lamp Black, Rose Bengal, C.I. I. Pigment Red 48: 1, C.I.
I. Pigment Red 122, C.I. I. Pigment
Red 57: 1, C.I. I. Pigment Yellow 97,
C. I. Pigment Yellow 12, C.I. I. Pigment Blue 15: 1, C.I. I. Pigment Blue 1
5: 3, and mixtures thereof.

Examples of the binder resin include styrenes such as styrene, chlorostyrene and α-methylstyrene, ethylene,
Unsaturated hydrocarbons such as propylene, butylene, isoprene and butadiene; halogenated unsaturated hydrocarbons such as chloroprene; vinyl esters such as vinyl acetate, vinyl propionate and vinyl benzoate; methyl acrylate, ethyl acrylate and acrylic acid n-propyl, butyl acrylate, dodecyl acrylate, octyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, butyl methacrylate,
Dodecyl methacrylate, lauryl methacrylate, α-methylene aliphatic monocarboxylic acid esters such as 2-ethylhexyl methacrylate, vinyl methyl ether, vinyl ethyl ether, vinyl butyl ether, vinyl ether such as vinyl isobutyl ether, vinyl methyl ketone,
Homopolymers and copolymers such as vinyl ketones such as vinyl ethyl ketone, vinyl hexyl ketone and vinyl isopropenyl ketone, vinyl nitriles such as acrylonitrile and methacrylonitrile, and vinyl pyridines such as 2-vinyl pyridine and 4-vinyl pyridine are exemplified. Can be.
In addition, polyester, polyurethane, epoxy resin,
Examples include silicone resin, polyamide, polyether, modified rosin, rosin-modified phenol-formalin resin, cellulose, paraffin, and waxes. These may be used alone or in combination of two or more. Particularly typical binder resins include polyester, polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, and styrene-maleic anhydride. Examples thereof include an acid copolymer, polyethylene and polypropylene, and a linear polyester resin comprising a polycondensate containing bisphenol A and a polyvalent aromatic carboxylic acid as main monomer components is particularly preferable.

Among the linear polyesters, a softening point of 90 to
150 ° C., glass transition point 50-70 ° C., number average molecular weight 2000-6000, weight average molecular weight 8000-15
Resins having a 0000, an acid value of 5 to 30, and a hydroxyl value of 5 to 40 can be particularly preferably used.

As toner components other than the colorant, there are a charge control agent, an anti-offset agent and the like, and if necessary, a magnetic fine powder may be contained. For example, components such as a charge control agent such as a salicylic acid metal salt, a metal-containing azo compound, nigrosine, and a quaternary ammonium salt, and an anti-offset agent such as low-molecular-weight polypropylene, low-molecular-weight polyethylene, and wax can be added.

A fluidizing agent such as silica, titania and alumina, a cleaning aid such as polystyrene fine particles, polymethyl methacrylate fine particles and polyvinylidene fluoride fine particles, or an external additive such as a transfer aid can also be used.

The average particle size of the toner is preferably 4.5 to 9.0 μm, since it is preferable that the specific surface area is large in order to increase the ratio of concealing the surface of the magnetic carrier.

In the present invention, when a magnetic brush developer layer composed of a two-component developer is formed on the developing sleeve, the resistance of the magnetic brush developer layer per unit length in the longitudinal direction (axial direction) of the developing sleeve is reduced. 5.0 × 10 ^{4 to} 7.0 × 10 ⁸ Ω / cm under an electric field strength of 0.4 V / μm, 2.0 V /
5.0 × 10 ^{4 to} 8.0 × 10 ⁶ Ω under electric field strength of μm
/ Cm range. The resistance of the magnetic brush developer layer under an electric field strength of 0.4 V / μm is 7.0 × 10
^If it exceeds ⁸ Ω / cm, solid image areas, especially low-density areas, will have a noticeable trailing edge, and if less than 5.0 × 10 ⁴ Ω / cm, brush marks will be generated. On the other hand, 2.0 V / μm
The resistance of the magnetic brush developer layer under electric field strength of 8.0 ×
If it exceeds 10 ⁶ Ω / cm, the trailing edge of the halftone is remarkably missing at the boundary where the halftone and the solid image are in contact with each other, and if it is less than 5.0 × 10 ⁴ Ω / cm, a brush mark is generated.

Further, in order to make the present invention more complete, it is necessary to optimize the packing density of the developer in the developing area.
in the range of mg / cm ^2, the opposing distance between the sleeve surface and the photosensitive member surface is preferably set in a range of 200 to 600 [mu] m.

In the present invention, the resistance of the core particles was determined as follows. Remove the photoconductor from the developing device,
After only the core particles are mounted on this developing device and a magnetic brush composed of the core particles is formed on the developing sleeve, an aluminum pipe having the same size as the photoconductor is loaded instead of the photoconductor. Next, a value obtained by dividing a DC voltage by (applied voltage) / (opposed distance between the aluminum pipe and the photoconductor) between the aluminum pipe and the photoconductor is applied so that a predetermined electric field intensity is obtained. Measure the value of the current flowing through. Next, a resistance is obtained from the applied voltage and the current value, and a value obtained by dividing the obtained resistance by the effective length of the developing sleeve is defined as a resistance at a predetermined electric field intensity. Here, the effective length refers to the width of the opening formed in the wall 12A of the developing housing 12 in the longitudinal direction (axial direction) of the developing sleeve in the developing device shown in FIGS. In this case, it is the width of the opening, and when the width of the opening is the same as the length of the developing sleeve or when the width of the opening is longer than the length of the developing sleeve, it is the length of the developing sleeve.

The resistance of the developer is determined in the same procedure as described above after mounting the developer in place of the core particles and adjusting the toner concentration. The toner density is 1.2 or more when the obtained image density is black toner, and
Adjust so that the gloss is 30 or more and 1.2 or more.

The present invention can provide a remarkable effect when applied to a color toner for a full-color image in which the above-mentioned defects are conspicuous because the various image levels are often continuously mixed. Black toner.

[0078]

The present invention will be specifically described below with reference to examples. (Examples 1 to 3 and Comparative Examples 1 to 3) <Preparation of Magnetic Carrier > 10 g of trifunctional isocyanate per 3 kg of spherical Mn-Mg ferrite particles having an average particle diameter of 45 μm as magnetic carrier 1 to 5 nucleus particles (Trade name: Takenate D110N, manufactured by Takeda Pharmaceutical Co., Ltd.) and 150 g of ethyl acetate as a solvent were added, followed by stirring and mixing at 60 ° C. using a pressure kneader. Next, 200 g of water was added, and the mixture was stirred and mixed at 120 ° C., and the solvent was removed under reduced pressure. This was sieved with a 75 μm mesh to obtain Magnetic Carrier 1. Magnetic carriers 2 to 5 shown in Table 1 were produced by the same procedure as above, except that the amount of the matrix resin coated and the core particles were changed as necessary.

Magnetic Carrier 6 15 g of polymethyl methacrylate (Mn = 1000)
0, Mw = 50000) is dissolved in 250 g of toluene, 3 kg of spherical Mn—Mg ferrite particles having an average particle diameter of 45 μm are added thereto, and a pressure kneader is used. The mixture was stirred at ℃ and the solvent was removed under reduced pressure. This is 75
The mixture was sieved with a μm mesh to obtain a magnetic carrier 6.

[0080]

[Table 1]

In Table 1, the resistance of the nucleus particles at an electric field strength of 0.4 V / μm was measured using an A Color 630 copying machine (manufactured by Fuji Xerox Co., Ltd., facing distance 500 μm with an aluminum pipe, effective length of developing sleeve). 30c
m, using an aluminum pipe and a developing sleeve in the forward direction, with a peripheral speed difference of 330 mm / s), adjusting the amount of nucleus particles on the developing sleeve to 50 mg / cm ² , applying a DC voltage of 200 V, and Except for using the current value at the lapse of 10 seconds, it was determined by the above procedure. Further, the applied voltage was set to 1000 V, and the resistance determined by the same procedure as above was defined as the resistance at an electric field strength of 2.0 V / μm. <Preparation of Toner> 95 parts by weight of polyester resin (ethylene oxide adduct of bisphenol A-terephthalic acid: TG: 65 ° C, Mn: 3500, Mw: 10,000) I. Pigment Red 57: 15 parts by weight The above materials were kneaded with an extruder, pulverized with a jet mill, and then classified with an air classifier to obtain resin particles having an average particle diameter of 7 μm. 0.4 parts by weight of titania particles having an average particle diameter of 20 nm and an average particle diameter of 4 with respect to 100 parts by weight of the resin particles.
0.8 parts by weight of 0 nm silica particles were added and mixed with a Henschel mixer to prepare magenta toner A. <Adjustment of Developer> Developers 1 to 6 were prepared by mixing 40 g of magenta toner A with 600 g of the magnetic carrier. <Evaluation> Adjusted developers 1 to 6 were subjected to A Color 630
When copying was performed in a copying machine, the obtained image densities were 1.41, 1.45, 1.50, 1.47,
1.52 and 1.50. Next, the resistance of the developer was measured in the same procedure as the measurement of the resistance of the core particles. next,
After removing the aluminum pipe and loading the photoconductor,
A print test was performed. Table 2 shows the results.

[0082]

[Table 2]

In the developers 1, 2, and 6, the trailing edge of the image is missing,
In the halftone portion, the solid image portion boundary omission is almost inconspicuous, whereas in the developers 3 and 4, the image omission occurred remarkably. Further, with the developer 5, no image omission occurred,
The brush mark was remarkable.

Next, 25,000 using the developers 1 and 6
When a repeated print test was performed on both sheets, both of them maintained the initial image quality.

Further, using the developers 1 and 6,
When the print test was repeatedly performed on 0 sheets, the developer 1 maintained the initial image quality, but the developer 6 exhibited remarkable brush marks. Observation of the surface of the magnetic carrier in these developers revealed that the peeling of the resin coating layer of the magnetic carrier in developer 6 was remarkable,
In the developer 1, the resin coating layer of the magnetic carrier was not peeled at all. This indicates that the resin coating layer formed of the matrix resin obtained by polymerization of the isocyanate compound and water has a sufficient strength even in a thin film. (Examples 4 to 9 and Comparative Examples 4 to 8) <Preparation of Solution for Forming Resin Coating Layer> Each composition shown in Table 3 was stirred and dispersed by a sand mill for 20 minutes to prepare a solution for forming a resin coating layer.

[0086]

[Table 3]

<Preparation of Magnetic Carrier> 1000 parts by weight of the core particles shown in Tables 4 and 5 and the above solution for forming a resin coating layer were put into a vacuum degassing kneader (the inner wall was heated to 100 ° C.), and the solution was added. After stirring for a minute, the solvent was distilled off under reduced pressure to obtain a magnetic carrier having a resin coating layer formed on the core particles. The magnetic carrier 9 was baked at 200 ° C. for 60 minutes after drying.

[0088]

[Table 4]

[0089]

[Table 5]

<Adjustment of Toner> Linear polyester resin 100 parts by weight (Ethylene oxide adduct of terephthalic acid-bisphenol A / linear polyester obtained from cyclohexanedimethanol, Tg = 62 ° C., Mn = 4,000, Mw = 35,000, acid value = 12, hydroxyl value = 25) 3 parts by weight of magenta pigment (CI Pigment Red 57) The above components were kneaded with an extruder, pulverized by a jet mill, and then classified by a wind-type classifier. And d ₅₀ = 6.6 μm
Resin particles were obtained. 0.5 parts by weight of silica (trade name: R972, manufactured by Nippon Aerosil Co., Ltd.) was added to 100 parts by weight of the resin particles using a Henschel mixer to obtain magenta toner B. <Preparation of Developer> Developers 7 to 17 were prepared by mixing 100 parts by weight of each of the magnetic carriers 7 to 17 with 8 parts by weight of the magenta toner B. <Evaluation> Adjusted developers 7 to 17 were subjected to A Color 63
When copying was performed in a copying machine, the obtained image densities were 1.46, 1.50, 1.51, and 1.5, respectively.
3, 1.48, 1.47, 1.51, 1.50, 1.5
4, 1.45, 1.43. Next, the resistance of the developer was measured in the same procedure as the measurement of the resistance of the core particles. Next, after removing the aluminum pipe and loading the photoreceptor, a print test was performed. Table 6 shows the results.

[0091]

[Table 6]

Next, using the developing agents 7 and 12, 2500
When the print test was repeatedly performed on 0 sheets, both of them maintained the initial image quality.

Further, using the developers 7 and 12
When the print test was repeatedly performed for 00 sheets, the initial image quality was maintained with the developer 7, but the remarkable brush mark was observed with the developer 12. Observation of the surface of the magnetic carrier in the developer revealed that the peeling of the resin coating layer of the magnetic carrier of the developer 12 was remarkable, whereas the peeling of the resin coating layer of the magnetic carrier of the developer 7 was completely observed. Did not. This indicates that the thicker the film, the more it can be used for a long time.

[0094]

According to the present invention, since the resistance of the magnetic brush developer layer per unit length in the longitudinal direction of the developing sleeve is set to a specific range, the solid image trailing edge is missing and the boundary between the solid image leading edge and the halftone trailing edge. It is possible to prevent a trailing edge of a halftone image in a portion, a decrease in toner supply capability of a developer to a photoconductor, and a brush mark caused by a latent image leak for a long time.

[Brief description of the drawings]

FIG. 1 is a diagram showing a main part of a developing device to which the present invention is applied.

FIG. 2 is a diagram illustrating a main part of another example of a developing device to which the present invention is applied.

3A and 3B show a main part of another example of a developing device to which the present invention is applied, wherein FIG. 3A is a perspective view and FIG. 3B is a cross-sectional view.

[Explanation of symbols]

 Reference Signs List 10 photoreceptor 12 developing housing 14 developing sleeve

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takashi Imai 1600 Takematsu, Minamiashigara, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (72) Inventor Masahiro Takagi 1600 Takematsu, Minamiashigara City, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (72) Inventor Akihiro Iizuka 1600 Takematsu, Minamiashigara-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (72) Inventor Masanori Ichimura 1600 Takematsu, Minamiashigara-shi, Kanagawa Prefecture Fuji Xerox Co., Ltd

Claims (13)

[Claims] 1. A photoconductor for forming an electrostatic latent image, a rotatable developing sleeve, and moving at least one of the photoconductor and the developing sleeve along the photoconductor surface by moving at least one of the photoconductor and the developing sleeve. The developing sleeve is relatively moved along the photosensitive member surface and rotated by rotating the developing sleeve along the surface of the photosensitive member. A magnetic brush developing method for sliding a magnetic brush developer layer formed on a sleeve and comprising a two-component developer containing a toner and a magnetic carrier, wherein the magnetic brush developing per unit length in a longitudinal direction of the developing sleeve The resistance of the agent layer is 5.0 × 10 ^{4 to} 7.0 × 10 ⁸ Ω / cm and 2.0 V / under an electric field strength of 0.4 V / μm.
5.0 × 10 ^{4 to} 8.0 × 10 ⁶ Ω under electric field strength of μm
/ Cm range. 2. The magnetic brush developing method according to claim 1, wherein the magnetic carrier has a resin coating layer on the surface of the core particles. 3. The resistance of the magnetic brush layer composed of the core particles per unit length in the longitudinal direction of the developing sleeve is:
5.0 × 10 ^{3 to} 1.0 under an electric field strength of 0.4 V / μm
× 10 ⁶ Ω / cm, 5 in an electric field strength of 2.0 V / [mu] m.
^3. The magnetic brush developing method according to claim 2, wherein the value is in a range of 0 * 10 < ³ > to 6.0 * 10 < ⁵ > [Omega] / cm. 4. An average particle size of the core particles is 30 to 50 μm.
4. The method according to claim 2, wherein m is m. 5. The resin coating layer is formed of a resin obtained by polymerization of at least one isocyanate compound and at least one compound selected from the group consisting of water, an amine compound and a polyol compound. The magnetic brush developing method according to any one of claims 2, 3, and 4. 6. The magnetic brush developing method according to claim 5, wherein a weight ratio of the core particles to the resin of the resin coating layer is 100: 0.01 to 100: 0.5. 7. The magnetic brush developing method according to claim 2, wherein the resin coating layer is a resin coating layer in which conductive fine particles are dispersed in a matrix resin. . 8. The magnetic brush developing method according to claim 7, wherein the volume occupancy of the conductive fine particles in the resin coating layer is 7 to 15%. 9. The magnetic brush developing method according to claim 7, wherein a weight ratio of the core particles to the resin of the resin coating layer is 100: 1.5 to 100: 5.0. 10. The magnetic brush developing method according to claim 7, wherein the matrix resin includes a resin having a critical surface tension of 30 dyne / cm or less. 11. The magnetic carrier according to claim 1, wherein the magnetization of the magnetic carrier at 1 kOe is 55 to 65 emu / g. Item 6. The magnetic brush developing method according to item 1. 12. The image forming apparatus according to claim 1, wherein a facing distance between the surface of the developing sleeve and the surface of the photosensitive member is in a range of 200 to 600 μm.
2. The magnetic brush developing method according to claim 1. 13. The developer amount on the developing sleeve is 20.
Claim 1, characterized in that the ~70mg / cm ^2,
2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12
The magnetic brush developing method according to any one of the above.