JP3352322B2 - Image forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic method, an electrostatic recording method, and the like. And an image forming method using the same.

[0002]

2. Description of the Related Art U.S. Pat.
7, 691, JP-B-42-23910 and JP-B-43-24748 describe various methods. All of these methods form an electrostatic latent image by irradiating a photoconductive layer with a light image corresponding to a document,
Next, a colored fine powder called a toner having the opposite polarity was attached to the electrostatic latent image to develop the electrostatic latent image, and a toner image was transferred to a transfer material such as paper as necessary. Thereafter, the image is fixed by heat, pressure, solvent vapor or the like to obtain a copy or printout.

The step of developing the electrostatic latent image is to form an image of the charged toner particles on the electrostatic latent image on the latent image carrier by utilizing the electrostatic interaction of the electrostatic latent image. is there. Generally, among methods of developing such an electrostatic latent image using toner,
A two-component developer in which a toner is dispersed in a medium called a carrier is suitably used for a full-color copying machine and a full-color printer that require particularly high image quality.

In recent years, with the development of multimedia, computer image processing, and the like, a means for outputting a higher definition full-color image has been demanded. For this purpose, full-color copy images and print-out images have higher quality,
Efforts are being made to achieve high definition and high quality even to the image level of silver halide photography. In response to these demands, studies are being made from a process and material perspective.

The two-component developing method described above also includes a contact two-component developing method in which the developer magnetic brush performs development while rubbing the surface of the latent image carrier, and a method in which the developer magnetic brush does not contact the latent image carrier. It is classified into a non-contact two-component developing method. Non-contact two-component development has the advantage that the so-called carrier adhesion phenomenon in which carriers adhere to the latent image carrier is unlikely to occur, but in order to obtain a high-definition full-color image as described above, excellent fine line reproducibility and sufficient Contact two-component development that provides a high image density is preferably used.

Further, in order to develop the toner on the electrostatic latent image, a developing bias is applied from the developer carrying member to the electrostatic latent image side.
A method of superimposing an AC bias on a bias is preferably used.

There is also a method of improving the image quality by reducing the particle size of the toner or the carrier or densifying the developer magnetic brush. JP-A-59-104663 describes a method of using a magnetic carrier having a small saturation magnetization to densify a developer magnetic brush and achieve high image quality.

However, the method for achieving high image quality as described above, that is, the reduction of the carrier particle diameter and the reduction of the magnetic force of the carrier using the contact two-component AC developing method are all used to carry a latent image. In order to easily cause a so-called carrier adhesion phenomenon in which a carrier adheres to a body, it has been difficult to put the carrier into practical use.

Before forming an electrostatic latent image on a latent image carrier, a process called so-called primary charging for uniformly charging the entire surface of the latent image carrier is performed. A so-called corona charger using corona discharge has been used.

However, in recent years, contact charging devices have been put to practical use instead. This is low ozone, low power,
In order to reduce the size of the apparatus, a conductive roller or a magnetic brush roller is used as a charging member. As a charging method, in order to perform contact charging smoothly and uniformly and without being affected by environmental changes, a voltage in which an AC component is superimposed is applied to a charging member as described in JP-A-63-149669. It is desirable to do.

Even in such a contact charging device, the essential charging mechanism uses a discharge phenomenon from the charging member to the latent image carrier, so that generation of ozone is inevitable. The voltage to be applied must be at least a value equal to or higher than the desired surface potential of the latent image carrier. When the charging using the AC component as described above is performed, vibration or abnormal noise due to an electric field is generated, and the latent image carrier is discharged. There were problems such as deterioration of the body surface.

In order to solve such a problem, charging by direct injection of charges into the latent image carrier has been desired. In order to inject electric charge directly to the surface of the latent image carrier, a charging member having a low resistance value is used, and a long charging time is applied to charge the electric charge to the trap level of the electric charge existing on the surface of the latent image carrier. There is a way. However, in such a charging method, it is premised that the specific resistance of the charging member is very low, that is, less than 1 × 10 ³ Ωcm, and a large charge leak is caused to a flaw or a pinhole generated on the surface of the latent image carrier. There were problems such as getting lost. Further, the time required for performing sufficient charging was not at a practical level.

Japanese Patent Application Laid-Open No. Hei 6-3921 discloses a method in which a charge injection layer is provided on the surface of a latent image carrier, and charges are injected into the charge injection layer by a contact charging member. This makes it possible to solve the above-mentioned various problems in the contact charging device.

As a charging member used in the contact charging device as described above, a large contact nip with a latent image carrier can be obtained.
A magnetic brush roller that can uniformly contact the surface of the latent image carrier is particularly preferably used.

In a contact charging device using a magnetic brush roller, it is necessary that the magnetic particles constituting the magnetic brush contact each other to form a conductive path, and the charge flowing through the conductive path causes the surface of the latent image carrier to be charged. Is charged and charged. However, when impurities are mixed in the magnetic brush, there is a problem that the charging characteristics are changed.
For example, when a relatively large amount of toner particles or the like is mixed into the magnetic brush for some reason, such a problem may be realized. Recently, a cleaner-less process has been proposed in which the waste toner recovery portion is omitted in order to realize a reduction in the size of the entire apparatus and simplification of maintenance. The toner remaining on the magnetic brush is mixed with a high probability without being cleaned.

Further, using the contact two-component developing process and the AC developing bias as described above for improving the image quality,
When a magnetic carrier obtained by applying a resin coat to a low-resistance core such as a conventional iron powder carrier or ferrite carrier having a core resistance of 1 × 10 ⁹ Ωcm or less is used as a developer, carrier adhesion and toner fog occur. However, when the toner and the developing magnetic carrier are mixed into the contact charging member, the contact charging ability may be insufficient.

JP-A-6-222676 discloses an image forming apparatus using a contact charging process of a charging magnetic brush.
Proposals have been made to increase the resistance of the magnetic carrier used for the developer to make the AC voltage power supply for charging and development common than the magnetic particles used for the charged magnetic brush, but in particular, a contact two-component type development process was used. In the case described in the specification, the resistance is controlled by changing the coating material of the ferrite particles, and when used as a magnetic particle for a charged magnetic brush and a magnetic carrier for a two-component developer, a full-color image is used. Could not achieve high image quality.

For the reasons described above, an image forming method which can achieve low ozone generation using a contact two-component type AC developing process which is excellent in reproducibility of fine lines and obtains a full-color image with high image density has been practically used. Not converted.

[0019]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming method which solves the above-mentioned problems, and in particular, provides an image forming method using a two-component developer and a contact charging process.

An object of the present invention is to provide an image forming method in which generation of ozone is suppressed, no carrier adhesion occurs, and a high quality toner image excellent in fine line reproducibility can be obtained.

An object of the present invention is to provide an image forming method using a contact AC charging process using a contact charging magnetic brush, in which the toner has a high transfer efficiency, has no toner fog, and is compatible with a cleanerless process. It is to provide a forming method.

[0022]

SUMMARY OF THE INVENTION The present invention provides a two-component latent image carrier having a charge injection layer having a surface resistance of 1 × 10 ¹⁰ to 1 × 10 ¹⁶ Ω, and a magnetic carrier and a toner. In an image forming method in which a developer carrying member for carrying a system developer is disposed to face and developed, the magnetic carrier is a coated carrier, and a specific resistance of a carrier core of the magnetic carrier is 1 × 10 ¹⁰ Ωcm or more. Wherein the specific resistance of the magnetic carrier is 1 × 10 ¹² Ωcm or more, the number average particle diameter of the magnetic carrier is 5 to 100 μm, and the developer magnetic brush formed on the developer carrier is The present invention relates to an image forming method in which development is carried out while being brought into contact with an image carrier and applying an alternating electric field.

In the developing system of the present invention, a two-component developer is used as a developer, and a developer magnetic brush is developed while applying an alternating electric field while rubbing and contacting the latent image carrier. Two-component AC development is optimal. This is to obtain a high quality toner image having excellent fine line reproducibility as described above.

The latent image carrier has a surface resistance of 1 × 10
There is a charge injection layer of ¹⁰ to 1 × 10 ¹⁶ Ω, and the generation of ozone can be suppressed by performing primary charging with a member that is in contact with the charge injection layer. In particular, by using a charging brush using magnetic particles, more uniform charging is possible.

Further, by reducing the magnetic force of the magnetic carrier constituting the two-component developer and substantially increasing the resistance, it is possible to prevent toner fog and the carrier from adhering, and at the same time, provide a fine line reproducibility. High quality images can be obtained.

Further, by using a toner produced by a polymerization method in the image forming apparatus having the above-described structure, a cleaner-less image forming method can be achieved with toner having high transfer efficiency and no fog. be able to.

Further, by using the developing resin carrier having substantially high resistance and small magnetic force as described above, the direction of rotation of the developer carrier and the direction of rotation of the latent image carrier are opposed to each other. By preferably using developing methods in which the directions are counter directions, it is possible to obtain a high quality image with high image density and no dot omission while preventing scavenging.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present inventors have conducted detailed studies and found that the surface resistance of the charge injection layer of the latent image carrier in the present invention is from 1 × 10 ¹⁰ to 1 × 10 ¹⁶ Ω. It was found necessary, and more preferably in the range of 1 × 10 ¹² to 1 × 10 ¹⁵ Ω. When the surface resistance of the charge injection layer is less than 1 × 10 ¹⁰ Ω, charges injected from the contact charging member are not held on the surface of the charge injection layer,
In the electrophotographic process of the reversal development system, as a result, a phenomenon called image deletion may be caused. This was particularly common under high humidity. Resistance on the surface of the charge injection layer is 1
If it exceeds × 10 ¹⁶ Ω, the charge is not sufficiently injected,
A so-called charged positive ghost in which the toner unnecessarily rides on the charging failure area of the latent image carrier may occur.

As described above, even if the surface resistance of the charge injection layer of the latent image carrier is in the range of 1 × 10 ¹⁰ Ω to 1 × 10 ¹⁶ Ω, the specific resistance of the injection charging member is in an appropriate range. Otherwise, charging is not performed properly. This needs to be adjusted by the configuration of the injection charging member. For example, when a charging brush roller made of magnetic particles is used, 1 × 10 ⁵
A charging brush roller made of a magnetic material having a specific resistance of about 1 × 10 ⁸ Ωcm shows good charging properties.

As the magnetic material constituting the charged magnetic brush roller, for example, a magnetic metal such as iron, cobalt and nickel or a compound thereof can be used. It is necessary to coat these with an appropriate coat resin or to perform an oxidation treatment, a reduction treatment, or the like to adjust the specific resistance to the above. For example, hydrogen-reduced Zn-Cu ferrite, oxidized magnetite, or the like can be used. Binder-type magnetic particles in which a magnetic metal oxide and conductive fine particles are dispersed in a binder resin, or particles obtained by coating the binder-type magnetic particles with an appropriate coat resin can also be used.

As the charge injection layer of the latent image carrier, a layer in which conductive fine particles are dispersed in an insulating and translucent binder resin is preferably used. This charge injection layer is
When the charged magnetic brush to which voltage is applied comes into contact, conductive particles exist as if they were countless independent floating electrodes on the conductive substrate of the latent image carrier, and the capacitors formed by these floating electrodes are charged. Can be expected. Accordingly, it was also confirmed that the voltage applied to the contact charging member and the surface potential of the latent image carrier converged to the same value, and that the applied voltage was minimal.

As described above, when the contact two-component developing process and the AC developing bias are used to achieve high image quality, the surface resistance of the charge injection layer is 1 × 10
^When a latent image carrier in the range of 10 Ω to 1 × 10 ¹⁶ Ω is used, if a conventional iron powder carrier or a magnetic carrier obtained by applying a resin coating to ferrite is used as a developer, carrier adhesion and toner fog may occur. Significant occurrence was observed.

It has been found that this phenomenon is more likely to appear as the specific resistance of the surface of the charge injection layer becomes lower, and also becomes more pronounced as the specific resistance of the magnetic carrier of the developer becomes lower.

The present inventors have searched for the cause of this phenomenon, and have reached the following conclusion.

That is, when a latent image carrier having a charge injection layer having a relatively low specific resistance and a developing magnetic carrier having a low specific resistance are used together, the potential of the latent image on the latent image carrier becomes
Leakage occurs through the developing magnetic carrier particles that come into contact with and rub, and the potential is changed so as to approach the developing bias potential. As a result, the fog removing potential decreases, and toner fogging occurs.

Therefore, in order to prevent this phenomenon, it has been found that it is effective to use a developing magnetic carrier having a high resistance. Specifically, when the surface resistance of the charge injection layer of the latent image carrier as in the present invention is in the range of 1 × 10 ¹⁰ Ω to 1 × 10 ¹⁶ Ω, the specific resistance of the developed magnetic carrier is 1 × 10 ¹² Ω.
Ωcm or more, and the specific resistance of the carrier core constituting the developing magnetic carrier is 1 × 10 ¹⁰ Ωc
It has been found that it is essential to use a carrier of m or more.

The measurement of the specific resistance of the magnetic carrier or the core particles of the present invention is performed using a measuring device shown in FIG. Cell E
Is filled with carrier or core particles, electrodes 21 and 22 are arranged so as to be in contact with the filled carrier or core particles, a voltage is applied between the electrodes, and a current flowing at that time is measured to obtain a specific resistance. Method. The conditions for measuring the specific resistance in the present invention are as follows: the contact area S between the filled carrier or the core particles and the electrode is about 2.3 cm ² , and the thickness d is about 2 m
m, the load of the upper electrode 22 is 180 g, and the measured electric field strength is 5 ×
It was set to 10 ⁴ V / m.

[0038] As the metal oxide constituting the developing magnetic carrier of the present invention, MO · Fe ₂ O ₃ or MFe ₂ shows the magnetic
Magnetite, ferrite and the like represented by the general formula of O ₄ can be preferably used. Here, M is a divalent or monovalent metal ion Mn, Fe, Ni, Co, Cu, M
g, Zn, Cd, Li, etc., correspond to M, and M can be used alone or as a plurality of metals. For example, iron oxides such as magnetite, γ iron oxide, Mn-Zn ferrite, Ni-Zn ferrite, Mn-Mg ferrite, Ca-Mg ferrite, Li ferrite, and Cu-Zn ferrite can be given. .

The above-mentioned metal oxides can be used alone as the carrier core. In this case, as described above, the core surface is subjected to a treatment such as intense oxidation to reduce the core specific resistance to 1 × 10 ^10. It is necessary to use Ωcm or more.

When a high-resistance carrier core is used as a developing magnetic carrier, a particularly preferable carrier form is
The above-mentioned metal oxides may be dispersed in a resin and used as a carrier core. In this case, one kind of metal oxide can be used by dispersing it in a resin, but it is particularly preferable to use a mixture of at least two kinds of metal oxides.

In this case, in addition to the above magnetic metal oxide,
Mg, Al, Si, Ca, Sc, Ti, V, Cr, M
n, Fe, Co, Ni, Cu, Zn, Sr, Y, Zr,
Non-magnetic metal oxides using a single metal or a plurality of metals such as Nb, Mo, Cd, Sn, Ba, Pb and the like and metal oxides exhibiting the above magnetism can be used. For example, non-magnetic metal oxides such as Al ₂ O ₃ , SiO ₂ , CaO, TiO ₂ , V ₂ O ₅ ,
CrO ₂ , MnO ₂ , Fe ₂ O ₃ , CoO, NiO, Cu
O, ZnO, SrO, Y ₂ O ₃ , ZrO _{2 and the} like can be used.

In this case, it is more preferable to use particles having similar specific gravities and shapes in order to increase the adhesion to the binder and the carrier strength. For example, magnetite and hematite, magnetite and SiO ₂ , magnetite and Al ₂ O ₃ , magnetite and TiO ₂ , magnetite and Ca—Mn ferrite, magnetite and Ca—M
g-based ferrite or the like can be preferably used. Above all, the combination of magnetite and hematite is
It can be preferably used from the viewpoint of carrier strength.

When the above metal oxide is dispersed in a resin to form a core, the number average particle diameter of the metal oxide exhibiting magnetism varies depending on the particle diameter of the carrier. be able to. When two or more metal oxides are dispersed and used, a metal oxide having a number average particle size of 0.02 to 2 μm can be used, and the other nonmagnetic metal oxide can be used. Those having a number average particle size of 0.05 to 5 μm can be used. in this case,
The other non-magnetic metal oxide on the magnetic particles (particle diameter r _a) is the particle size ratio r _b / r _a of (particle size r _b) preferably more than 1 times, below 5 times greater than the 1-fold More preferably, there is. When the ratio is 1.0 or less, magnetic metal oxide particles having a low specific resistance are likely to appear on the surface, and the resistance of the carrier core cannot be sufficiently increased, so that the effect of preventing carrier adhesion of the present invention is hardly obtained. Become. On the other hand, when the ratio exceeds 5.0 times, the incorporation of the metal oxide particles into the resin may not be successful, and the strength of the carrier may be reduced and the carrier may be easily broken.

The specific resistance of the metal oxide dispersed and used in the resin may be such that the magnetic particles are in the range of 1 × 10 ³ Ωcm or more, and in particular, a mixture of two or more metal oxides is used. In such a case, it is necessary to use particles having a specific resistance higher than that of the magnetic particles in which the particles exhibiting magnetism are in the range of 1 × 10 ³ Ωcm or more, and the other nonmagnetic metal oxide particles. Preferably, the other nonmagnetic metal oxide used in the present invention has a specific resistance of 1 × 10 ⁸ Ωcm or more. The specific resistance of the magnetic particles is 1 × 10 ³ Ωc
If it is less than m, a desired carrier specific resistance cannot be obtained even if the content of the dispersed metal oxide is reduced. When two or more metal oxides are dispersed, the nonmagnetic metal oxide having a large particle diameter has a specific resistance of less than 1 × 10 ⁸ Ωcm,
The specific resistance of the carrier core cannot be sufficiently increased, and the effect of the present invention is hardly obtained.

The total content of the metal oxide in the metal oxide-dispersed resin core of the present invention is from 50% by weight to 99% by weight. If the amount of the metal oxide is less than 50% by weight, the chargeability becomes unstable, and the carrier is charged under a low-temperature and low-humidity environment, and the residual charge tends to remain. Easily adhere to the carrier surface. Also,
If the content exceeds 99% by weight, the strength of the carrier is reduced, and problems such as cracking of the carrier due to durability are likely to occur.

Further, as a preferable embodiment of the present invention, 2
In the metal oxide-dispersed resin core in which at least one kind of metal oxide is dispersed, the content of the metal oxide having magnetism in the whole metal oxide is 30% by weight to 95% by weight. When the content is less than 30% by weight, the resistance of the core is improved, but the magnetic force as a carrier is reduced, which may cause the carrier to adhere. On the other hand, if it exceeds 95% by weight, depending on the specific resistance of the metal oxide having magnetism, it is not possible to attain a more preferable high resistance of the core.

The metal oxide contained in the metal oxide-dispersed resin core used in the present invention is preferably subjected to a lipophilic treatment. When the lipophilic metal oxide is dispersed in a binder resin to form core particles, the metal oxide can be uniformly and densely incorporated into the binder resin. In particular, when the core particles are formed by a polymerization method, it is important to obtain spherical particles having a smooth surface and to sharpen the particle size distribution.

The lipophilic treatment is performed by treating the metal oxide with a coupling agent such as a silane coupling agent or a titanate coupling agent, or by dispersing the metal oxide in an aqueous solvent containing a surfactant. There are methods such as making the surface lipophilic.

As the silane coupling agent used herein, those having a hydrophobic group, an amino group or an epoxy group can be used. Examples of the silane coupling agent having a hydrophobic group include vinyltrichlorosilane, vinyltriethoxysilane, and vinyltris (β-methoxy) silane. Examples of the silane coupling agent having an amino group include γ-aminopropylethoxysilane, N-β (aminoethyl) -γ-aminopropyltrimethoxysilane, and N-β (aminoethyl)-
γ-aminopropylmethyldimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane and the like. Examples of silane coupling agents having an epoxy group include γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltriethoxysilane, β
-(3,4-epoxycyclohexyl) trimethoxysilane and the like.

As the titanate coupling agent, for example, isopropyl triisostearoyl titanate,
Examples thereof include isopropyl tridodecylbenzenesulfonyl titanate and isopropyl tris (dioctyl pyrophosphate) titanate.

As the surfactant, a commercially available surfactant can be used as it is.

Examples of the binder resin used in the metal oxide dispersed core of the present invention include all resins obtained by polymerizing vinyl monomers. Examples of the vinyl monomer here include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, and pn-butylstyrene. , P-tert-
Butylstyrene, pn-hexylstyrene, pn-
Octylstyrene, pn-nonylstyrene, pn-
Decylstyrene, pn-dodecylstyrene, p-methoxystyrene, p-chlorostyrene, 3,4-dichlorostyrene, m-nitrostyrene, o-nitrostyrene,
styrene derivatives such as p-nitrostyrene; ethylene and unsaturated monoolefins such as ethylene, propylene, butylene and isobutylene; unsaturated diolefins such as butadiene and isoprene; vinyl chloride, vinylidene chloride, vinyl bromide, and vinyl fluoride Vinyl esters such as vinyl acetate, vinyl propionate and vinyl benzoate; methacrylic acid and methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, methacrylic acid α-methylene aliphatic monocarboxylic esters such as n-octyl, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate and phenyl methacrylate; acrylic acid and methyl acrylate, ethyl acrylate Acrylates such as n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, and phenyl acrylate Maleic acid, maleic acid half ester;
Vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and methyl isopropenyl ketone; N-vinyl pyrrole;
N-vinyl compounds such as vinyl carbazole, N-vinyl indole and N-vinyl pyrrolidone; vinyl naphthalenes; acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile and acrylamide;
Acrolein and the like can be mentioned, and those obtained by polymerizing one or more of them are used.

In addition to resins obtained by polymerization from vinyl monomers, non-vinyl condensation resins such as polyester resins, epoxy resins, phenol resins, urea resins, polyurethane resins, polyimide resins, cellulose resins, polyether resins, and the like, And a mixture of the above-mentioned vinyl resin.

The method for producing the metal oxide-dispersed core of the present invention is as follows: a vinyl-based or non-vinyl-based thermoplastic resin, a metal oxide, and other additives such as a curing agent are sufficiently mixed by a mixer. Melting and kneading using a kneader such as a heating roll, kneader, extruder, etc., and after cooling this,
A carrier core can be obtained by performing pulverization and classification.
At this time, it is preferable that the obtained metal oxide-containing resin particles are thermally or mechanically spherical and used as a core.

As a more preferred method for producing the metal oxide dispersed core of the present invention, there is a method of directly mixing and polymerizing a monomer and a metal oxide to obtain a carrier core. At this time, as the monomers used for the polymerization, bisphenols and epichlorohydrin, which are the starting materials for the epoxy resin, phenols and aldehydes of the phenol resin, urea and aldehydes of the urea resin, melamine and Aldehydes and the like are used. For example, as a method for producing a carrier core using a curable phenolic resin, the metal oxide described above, preferably a lipophilic metal oxide, of phenols and aldehydes in an aqueous medium in the presence of a basic catalyst And polymerize to obtain a core. In such a method for producing a carrier core, a carrier core obtained by further adding a phenol and an aldehyde in an aqueous medium in the presence of a basic catalyst and further coating the phenolic resin on the surface is used. Can be further improved. At this time, the surface of the carrier core can be made more robust by incorporating the metal oxide particles into the resin to be coated.

In a particularly preferred method for producing the carrier core of the present invention, it is preferable to use a crosslinked binder in order to increase the strength of the carrier core or to coat the coating resin more favorably. For example, a crosslinking component is added during melt-kneading and crosslinking is performed during kneading. Alternatively, a method of selecting a curable resin at the time of direct polymerization and directly polymerizing to obtain a core, or a method of using a monomer containing a cross-linking component can be used.

The carrier used in the present invention needs to be coated with an appropriate coat resin in accordance with the charge amount of the toner used in the present invention. The coating amount of the coating material used in the present invention is in the range of 0.1% by weight to 10% by weight, and most preferably in the range of 0.3% by weight to 5% by weight.

If the coating amount is less than 0.1% by weight, it becomes difficult to sufficiently coat the carrier core material, and in particular, it is not possible to sufficiently control charging of the toner after running.
On the other hand, if it exceeds 10% by weight, the specific resistance can be kept in a desired range because the amount of the resin coating is too large. Not preferred.

The coating resin that can be used in the present invention includes:
Insulating resin can be suitably used. Here, as the insulating resin used, either a thermoplastic resin or a thermosetting resin can be used. Specifically, for example, as the thermoplastic resin, polystyrene, polymethyl methacrylate, styrene-acrylic Acrylic resin such as acid copolymer, styrene-butadiene copolymer, ethylene-vinyl acetate copolymer, vinyl chloride, vinyl acetate, polyvinylidene fluoride resin, fluorocarbon resin, perfluorocarbon resin, solvent-soluble perfluorocarbon resin, polyvinyl alcohol , Polyvinyl acetal, polyvinyl pyrrolidone, petroleum resin, cellulose, cellulose acetate,
Cellulose derivatives such as cellulose nitrate, methylcellulose, hydroxymethylcellulose, hydroxyethylcellulose and hydroxypropylcellulose, novolak resins, low molecular weight polyethylene, saturated alkyl polyester resins, aromatic polyester resins such as polyethylene terephthalate, polybutylene terephthalate and polyacrylate, polyamide resins, polyacetal Resins, polycarbonate resins, polyether sulfone resins, polysulfone resins, polyphenylene sulfide resins, and polyether ketone resins can be mentioned.

Specific examples of such curable resins include, for example, phenolic resins, modified phenolic resins, maleic resins, alkyd resins, epoxy resins, acrylic resins, and specifically, for example, maleic anhydride-terephthalic acid-
Unsaturated polyester, urea resin, melamine resin, urea-melamine resin, xylene resin, toluene resin, guanamine resin, melamine-guanamine resin, acetoguanamine resin, gliptal resin, furan resin, silicone resin obtained by polycondensation of polyhydric alcohol , A polyimide resin, a polyamide imide resin, a polyether imide resin, a polyurethane resin and the like. The above-mentioned resins can be used alone or in combination. Further, a thermoplastic resin may be mixed with a curing agent or the like and cured to be used.

As a method for preferably producing the coated carrier of the present invention, there are a method in which a resin solution is sprayed while the carrier core material is floated and flown to form a coat film on the surface of the core material, and a spray drying method. The above-mentioned coating method is particularly necessary when it is necessary to almost completely coat the coating resin on a relatively low-resistance carrier core as described above, or when coating a metal oxide-dispersed resin core using a thermoplastic resin. It is suitable.

Further, as another coating method, the resin-coated carrier of the present invention can be produced by another coating method in which a solvent is gradually evaporated while applying a shearing stress. Specific examples of such a method include a method in which a carrier fixed after volatilization of a solvent at a temperature equal to or higher than the glass transition point of a coat resin is crushed, and a method in which a coating film is cured and crushed while applying shear stress. .

Further, when such a development carrier having substantially high resistance is used, there is an advantage that the carrier is less likely to adhere to the latent image carrier, that is, a so-called carrier adhesion phenomenon, than the development carrier having low resistance. . This is because, in the driving force of carrier adhesion, in particular, in the contact development method in which an alternating electric field is applied, injection of charge from the developer carrier to the development magnetic carrier is a dominant factor. By using a carrier having substantially high resistance as described above, in which charge injection does not easily occur, the carrier adhesion phenomenon is remarkably improved.

As the charging member of the latent image carrier, there are a fur brush, a magnetic brush, a resin roller and the like, but it is preferable to use a magnetic brush in order to achieve more uniform charging and high durability.

When a magnetic brush composed of magnetic particles is used for the charging member of the latent image carrier, the specific resistance of the magnetic particles must be 1 × 10 ⁵ to 1 × 10 ⁸ Ωcm as described above. However, this is considerably lower than the specific resistance of the developed magnetic carrier of the present invention, and when the magnetization strength of the magnetic particles at a magnetic field of 1 kOe is not sufficiently high, the above principle is used. The magnetic particles adhere to the carrier. For this reason, the magnetic particles used for the charged magnetic brush need to be at least higher than the developing magnetic carrier.
Magnetization intensity in kilo-oersted is 200 emu /
cm ³ or more.

The particle size of the developed magnetic carrier of the present invention is preferably 5 to 100 μm in number average particle size. When the number average particle size is less than 5 μm, particularly in the case of a contact two-component developing process and a developing system using an AC developing bias as in the image forming method of the present invention, a development magnetic carrier having a substantially high resistance as described above. Even in this case, there were cases where the carrier adhesion could not be avoided. Further, the number average particle size is 10
If it exceeds 0 μm, a high-quality toner image excellent in thin line reproducibility, which is the object of the present invention, may not be obtained.

The method for measuring the particle size of the carrier used in the present invention will be described. The particle size of the carrier of the present invention is randomly determined by a scanning electron microscope (100 to 5,000 times).
300 or more carrier particles having a size of μm or more are extracted and measured as a carrier particle size with a Feret diameter in the horizontal direction by an image processing analyzer Luzex3 manufactured by NIRECO CORPORATION to calculate a number average particle size.

The magnetic strength of the developed magnetic carrier of the present invention is preferably such that the magnetic strength of the magnetic carrier at a magnetic field of 1 kOe (σ ₁₀₀₀ ) is in the range of 40 to 250 emu / cm ³ . Magnetization strength (σ ₁₀₀₀ ) is 4
If it is less than 0 emu / cm ³ , the magnetic carrier particles may not be sufficiently held by the developer carrier, and the carrier may adhere. Magnetization strength (σ ₁₀₀₀ ) of 250
When it exceeds emu / cm ³ , the density of the developer magnetic brush becomes coarse, the dot reproducibility is deteriorated, and the magnetic share between the carriers is increased. The image may be adversely affected.

The magnetic properties of the carrier used in the present invention are as follows.
The measurement is performed using an oscillating magnetic field type automatic magnetic property recording device BHV-30 manufactured by Riken Denshi Co., Ltd. The magnetic characteristic value of the carrier powder creates an external magnetic field of 1 kOe, and determines the magnetization intensity at that time. The carrier is manufactured in a state of being packed in a cylindrical plastic container so as to be sufficiently dense. In this state, the magnetization moment was measured, and the actual weight when the sample was put was measured to determine the magnetization strength (emu /
g). Next, the true specific gravity of the carrier particles is obtained by a dry automatic densimeter Acupic 1330 (manufactured by Shimadzu Corporation), and the magnetization intensity (emu / g) is multiplied by the true specific gravity to obtain the magnetization per unit volume of the present invention. Strength (e
mu / cm ³ ).

When a developing magnetic carrier having a relatively low magnetic force is used as in the present invention, a developing method in which the rotation of the developer carrier and the rotation of the latent image carrier are in counter directions to each other can be preferably used. In this method, compared to the developing method in which the rotation of the developer carrier and the rotation of the latent image carrier are in the forward direction, at the same process speed, the developer magnetic brush that contacts a part of the latent image carrier is used. Since the amount, that is, the absolute amount of toner increases, a high-quality image with high image density and no dot omission can be expected.

When a developing magnetic carrier having a high magnetic force is used to perform contact two-component AC development as in the present invention by using a developing method in which rotation of the developer carrier and rotation of the latent image carrier are in counter directions to each other. In comparison with the developing method in which the rotation of the developer carrier and the rotation of the latent image carrier are in the forward directions,
So-called scavenging, in which streaks appear on an image due to a rigid developer magnetic brush, is likely to occur. This is because the developer magnetic brush comes into stronger contact with the latent image and the toner on the latent image. However, in the case of a developing magnetic carrier having a relatively low magnetic force as in the present invention, scavenging hardly occurs because the developer magnetic brush contacts the latent image carrier and the toner image relatively softly.

In the contact two-component AC developing system in the image forming method of the present invention, the alternating electric field applied to the developer magnetic brush is preferably from 500 Hz to 5000 Hz. When the alternating electric field to be applied is less than 500 Hz, no matter how the developing magnetic carrier of the present invention has a substantially high resistance, the charge is injected into the latent image carrier through the developing magnetic carrier, and the carrier adheres. There was a case. Further, when the applied alternating electric field exceeds 5000 Hz, the toner cannot follow the electric field and the image quality is likely to be deteriorated.

As the alternating electric field to be applied, a conventional sine wave, triangular wave or rectangular wave can be used, but an alternating electric field whose waveform is appropriately controlled can also be used. For example, a first voltage that directs toner from the latent image carrier to the developer carrier, a second voltage that directs toner from the developer carrier to the latent image carrier, and a voltage between the first voltage and the second voltage Third
An alternating electric field that forms a waveform pattern with a voltage can be used. In such a case, the frequency is in the range of the frequency of the alternating electric field in the present invention, that is, 500 Hz to 1 cycle of the repetition pattern of the waveform. 500
Preferably, it is 0 Hz.

The toner used in the image forming method of the present invention preferably has a weight average particle diameter in the range of 1 to 10 μm. If the toner particle size exceeds 10 μm, one particle for developing the latent image becomes large, so that a high-definition toner image, which is the object of the present invention, cannot be obtained.

By the way, it is possible to combine the image forming method of the present invention with a cleaner-less process. However, as described above, when a magnetic brush roller is used as the contact charging member and the cleaner-less process is combined therewith. In addition, there is a problem that when toner is mixed into the magnetic brush, the charging characteristics thereof change.

In order to avoid such a problem, when a cleanerless process is combined with the image forming method of the present invention, a toner having a transfer efficiency of 95% or more is essential, and more preferably a toner having a transfer efficiency of 98% or more. It is better to use

The transfer efficiency is determined by calculating the weight (T1) of the transferred toner per unit area after the solid black image is developed and then transferring it to paper, and the weight of the toner remaining on the latent image carrier without being transferred (T1). T2) was measured and calculated by the following equation: transfer efficiency (%) = 100 × T1 / (T1 + T2).

Therefore, when the image forming method of the present invention is combined with a cleanerless process, it is preferable that a part or all of the toner is manufactured by a polymerization method. Further, it is preferable that an appropriate external additive is present around the toner. The toner produced by the polymerization method generally has a high sphericity, and is therefore placed on the latent image carrier with a small contact area, so that the transfer efficiency is high. Also, the external additive serves as a spacer between the latent image carrier and the toner particles,
The transferability of the toner can be improved. In addition, since the sphericity is high, the frictional charging of the toner becomes good, and the toner fog due to poor charging is also eliminated. Therefore, it is possible to prevent the fog toner from being transferred to the contact charging magnetic brush without being transferred.

As the external additive, conventionally used external additives can be used, and inorganic fine particles or organic fine particles,
Alternatively, a mixture thereof can be used. The external additives preferably have a specific surface area of at least 100 m ² / g by the BET method. When the specific surface area is less than 100 m ² / g, the fluidity of the toner is lost, and the transferability of the toner cannot be sufficiently improved.

In the image forming method of the present invention, the developer carrier has a surface shape of 0.2 μm ≦ center line average roughness (Ra) ≦ 5.0 μm 10 μm ≦ average interval of unevenness (Sm) ≦ 80 μm 0.05 ≦ Ra / Sm ≦ 0.5 It is preferable to satisfy the above conditions.

Ra and Sm are values defining the average roughness of the center line and the average interval of the irregularities described in JIS-B0601 and ISO468, and are obtained by the following equations.

[0082]

(Equation 1)

[0083]

(Equation 2)

If Ra is less than 0.2 μm, the developer is insufficiently transported, so that image unevenness and image density unevenness due to durability are likely to occur. When Ra exceeds 5 μm, although the developer transportability is excellent, the regulating force in the developer transporting amount regulating section such as a blade becomes too large, so that the external additive is deteriorated by the rubbing and the image quality at the endurance is deteriorated. Decrease.

When Sm is larger than 80 μm, it becomes difficult for the developer to be held on the developer carrying member, so that the image density becomes low. The details of the cause of this Sm are unknown, but since the sliding with the developer carrying member occurs at the transport amount regulating portion of the developer carrying member, etc., the developer becomes dense when the interval between the irregularities is too large. It is thought that the force acts as a mass packed into the developer, and the force exceeds the holding force between the developer carrier and the developer. When Sm is less than 10 μm, many of the irregularities on the surface of the carrier become smaller than the average particle size of the developer, so that the particle size selectivity of the developer entering the concave portion is generated, and fusion by the developer fine powder component is easily caused. . It is also difficult to manufacture.

Further, from the above viewpoint, the inclination of the convex / concave obtained from the height of the convex portion on the developer carrying member and the interval between the concave and convex portions (≒
f (Ra / Sm)) is an important cause in the present invention.
In the present invention, it is preferable that 0.05 ≦ Ra / Sm ≦ 0.5, and more preferably 0.07 or more and 0.3 or less.

If the ratio Ra / Sm is less than 0.05, the developer is not easily held on the developer carrier due to a weak holding force of the developer on the developer carrier. Is not controlled, resulting in image unevenness. Ra /
When Sm exceeds 0.5, the developer entering the concave portion on the surface of the developer carrying member becomes difficult to circulate with other developers, so that the developer is fused.

By further processing several grooves (so-called knurls) in the length direction of the developer carrying member, it becomes easy to uniformly coat the developer carrying member with even more excellent fluidity. Was.

The measurement of Ra and Sm in the present invention is performed by using a contact type surface roughness measuring instrument SE-3300 (manufactured by Kosaka Laboratories).
And in accordance with JIS-B0601.

The method for producing the developer bearing member having a predetermined surface roughness according to the present invention includes, for example, a sand blasting method using irregular and regular particles as abrasive grains, and a method for forming irregularities in a sleeve circumferential direction. A sandpaper method of rubbing the sleeve surface with sandpaper in the axial direction, a method of chemical treatment, a method of forming a resin convex after coating with an elastic resin, and the like can be used.

The method for measuring the triboelectric charge of the toner used in the present invention will be described below. The two-component developer sampled from the developer carrier is placed in a metal container equipped with a 635-mesh conductive screen at the bottom, sucked with a suction machine, and the weight difference before and after suction and the condenser connected to the container. The amount of triboelectrification is determined from the potential accumulated in. At this time, the suction pressure is set to 250 mmHg. With this method, the triboelectric charge amount is calculated using the following equation.

Q (μC / g) = (C × V) × (W ₁ −W ₂ ) ⁻¹ (where W ₁ is the weight before suction, W ₂ is the weight after suction, and C Is the capacity of the capacitor, and V is the potential stored in the capacitor.)

A method for measuring the surface resistance of the electrostatic latent image carrier used in the present invention will be described. On the latent image carrier surface,
A comb-shaped electrode having an effective electrode length of 2 cm and a distance between the electrodes of 120 μm is vapor-deposited with gold, and is measured by applying a voltage of 100 V with a resistance measuring device (4140BpAMATER manufactured by Hewlett-Packard).

[0094]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples.

<Manufacture Example of Carrier> (Carrier A) 9.0 parts by weight of phenol 13.5 parts by weight of formalin solution (about 40% formaldehyde, about 10% methanol, the rest being water) Magnetite subjected to lipophilic treatment 54. 0 parts by weight (particle diameter 0.24 μm, specific resistance 5 × 10 ⁵ Ωcm) Hematite treated with lipophilic treatment 30.0 parts by weight (particle diameter 0.60 μm, specific resistance 8 × 10 ⁹ Ωcm)

The lipophilicity of the magnetite and the hematite used here was set at 0.1 to the weight of each metal oxide.
This was carried out by mixing and stirring 5% by weight of a silane coupling agent (γ-aminopropyltrimethoxysilane) at 100 ° C. for 0.5 hour using a Henschel mixer.

The above materials and 2.0 parts by weight of 28% ammonia water as a basic catalyst and 12 parts by weight of water were put in a flask, and the temperature was raised to 85 ° C. in 40 minutes while stirring and mixing.
The mixture was kept, reacted and cured for 5 hours to perform polymerization. Thereafter, the mixture was cooled to 30 ° C., 100 parts by weight of water was added, the supernatant was removed, and the precipitate was washed with water and air-dried. Next, this was dried at 180 ° C. under reduced pressure (5 mmHg or less) to obtain a spherical carrier core in which magnetite and hematite were bound using a phenol resin as a binder.
The resistance of the obtained core was 2.5 × 10 ¹² Ωcm.

The surface of the obtained core particles was coated with a thermosetting silicone resin by the following method. A 10% by weight carrier coating solution was prepared using toluene as a solvent so that the amount of the coating resin was 0.5% by weight. The solvent was volatilized while continuously applying shear stress to the coating solution to coat the carrier. The coated carrier particles are
After curing at 80 ° C. for 2 hours, the coated carrier was classified using a multi-segment classification device. The number average particle size of the obtained carrier particles was 28.2 μm.

The specific resistance of the carrier particles was measured to be 3.9 × 10 ¹³ Ωcm. Also, as a result of measuring the saturation magnetization of the carrier particles, the intensity of magnetization at 1 kOe (σ ₁₀₀₀ ) = 129.0 emu / cm.
³ (the true specific gravity of the carrier was 3.50 g / cm ³ ).

(Carrier B) Phenol 10.0 parts by weight Formalin solution 15.0 parts by weight (formaldehyde about 40%, methanol about 10%, remainder water) 34.0 parts by weight of lipophilized magnetite (carrier A) 51.0 parts by weight of lipophilic hematite (used in carrier A)

Using the above materials, polymerization was carried out in the same manner as in Carrier A, except that the amount of water to be added was 20 parts by weight, to obtain a spherical carrier core in which magnetite and hematite were bound using a phenol resin as a binder. Was. The specific resistance of the obtained core was 2.0 × 10 ¹² Ωcm.

The obtained core particles were coated with the same coating resin as carrier A in exactly the same manner as carrier A, and classified. The number average particle size of the obtained carrier particles is
It was 50.0 μm.

The specific resistance of the carrier particles was measured and found to be 2.5 × 10 ¹³ Ωcm. Also, as a result of measuring the saturation magnetization of the carrier particles, the intensity of magnetization at 1 kOe (σ ₁₀₀₀ ) = 87.2 emu / cm ^3.
(The true specific gravity of the carrier was 3.44 g / cm ³ ).

(Carrier C) 9.0 parts by weight of phenol 13.5 parts by weight of formalin solution (about 40% formaldehyde, about 10% methanol, the remainder being water) 67.0 parts by weight of lipophilic magnetite (carrier A) 17.0 parts by weight of lipophilic hematite (used in carrier A)

Using the above materials, polymerization was carried out in the same manner as in Carrier A, except that the amount of water to be added was changed to 11 parts by weight, to obtain a carrier core in which magnetite and hematite were bound using a phenol resin as a binder. The specific resistance of the obtained core was 2.3 × 10 ¹⁰ Ωcm.

The obtained core particles were coated with the same coating resin as the carrier A in the same manner as the carrier A, and classified. The number average particle size of the obtained carrier particles is 2
It was 8.1 μm.

The specific resistance of the carrier particles was measured and found to be 2.1 × 10 ¹² Ωcm. Also, as a result of measuring the saturation magnetization of the carrier particles, the intensity of magnetization at 1 kOe (σ ₁₀₀₀ ) = 170.3 emu / cm.
³ (the true specific gravity of the carrier was 3.52 g / cm ³ ).

(Carrier D) Fe_TwoO_Three 26.4 parts by weight CuO  12.0 parts by weight ZnO  52.7 parts by weight and weighed using a ball mill.
Was.

After calcining, it was pulverized by a ball mill and further granulated by a spray drier. This was sintered and further classified to obtain carrier core particles. The specific resistance of the obtained carrier core is 3.2 × 10 ⁹
Ωcm. A styrene-2-ethylhexyl methacrylate copolymer (copolymerization ratio: 50) was added to the carrier core.
/ 50) using a fluidized bed type coating apparatus Spiracoater (manufactured by Okada Seiko Co., Ltd.) using toluene as a solvent so that the coating amount becomes 1.5% by weight, and dried in a fluidized bed at 150 ° C. for 1 hour. Got a career. The particle size of the obtained carrier particles was 29.0 μm.

The specific resistance of the carrier particles is 3.1 ×
It was 10 ¹¹ Ωcm. Also, as a result of measuring the saturation magnetization of the carrier particles, the magnetization intensity at 1 kOe (σ ₁₀₀₀ ) was 270.5 emu / cm ³ (the true specific gravity of the carrier was 4.88 g / cm ³ ).

Table 1 shows the physical properties of each carrier.
Shown in

[0112]

[Table 1]

<Production Example of Toner> (Toner 1) 0.1M-
After adding 450 parts by weight of an aqueous solution of Na ₃ PO ₄ and heating to 60 ° C., the mixture was stirred at 12000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo). 1.0M-
68 parts by weight of a CaCl ₂ aqueous solution is gradually added, and Ca ₃ (P
An aqueous medium containing O ₄ ) ₂ was obtained.

On the other hand, (monomer) styrene 165 parts by weight n-butyl acrylate 35 parts by weight (colorant) I. Pigment Blue 15: 3 15 parts by weight (Polar resin) saturated polyester 10 parts by weight (acid value 14, peak molecular weight 8000) (release agent) Ester wax (melting point 70 ° C) 50 parts by weight The above formulation is heated to 60 ° C. And TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) to uniformly dissolve and disperse at 12000 rpm. This was dissolved in 10 parts by weight of a polymerization initiator 2,2'-azobis (2,4-dimethylvaleronitrile) to prepare a polymerizable monomer composition.

The polymerizable monomer composition was charged into the aqueous medium, and the mixture was stirred at 9500 rpm for 10 minutes with a TK homomixer at 60 ° C. in an N ₂ atmosphere. Granulated. Thereafter, the temperature was raised to 80 ° C. while stirring with a paddle stirring blade, and the reaction was performed for 10 hours. After completion of the polymerization reaction, residual monomers were distilled off under reduced pressure. After cooling, hydrochloric acid was added to dissolve calcium phosphate, followed by filtration, washing with water and drying to obtain cyan colored suspension particles.

Thereafter, classification was performed by a multi-stage classifier. The obtained colored particles have a weight average particle size (D4) of about 6.
0 μm, and the number average particle diameter (D1) was 5.1 μm.

With respect to 100 parts by weight of the obtained colored particles,
2.0 parts by weight of hydrophobic silica having a specific surface area of 200 m ² / g by the BET method was externally added to obtain Polymerized Toner 1.

(Toner 2) (Monomer) Styrene 77.0 parts by weight n-butyl acrylate 22.0 parts by weight (polymerization initiator) Benzoyl peroxide 1.4 parts by weight (crosslinking agent) divinylbenzene 2 parts by weight

In a four-necked flask, add 180 parts of water purged with nitrogen.
Weight part and 0.2 weight part aqueous solution of polyvinyl alcohol 2
After adding 0 parts by weight, the above formulation was added and stirred to form a suspension. Thereafter, after the inside of the flask was replaced with nitrogen, the temperature was raised to 80 ° C. and maintained at the same temperature for 10 hours to carry out a polymerization reaction.

After washing the polymer with water, the polymer was dried under reduced pressure while maintaining the temperature at 65 ° C. to obtain a resin. 88
Parts by weight, C.I. I. Pigment Blue 15:
7 parts by weight, 5 parts by weight of an acetylacetone metal compound as a charge control agent, and 3 parts by weight of a low-molecular-weight polypropylene were mixed by a fixed-tank-type dry mixer. Was subjected to melt kneading.

This melt-kneaded product was crushed by a hammer mill to obtain a crushed toner composition of 1 mm mesh pass.
Further, after crushing the coarsely crushed product by a mechanical crusher to a volume average diameter of 20 to 30 μm, crushing is performed by a jet mill utilizing collision between particles in a swirling flow, and then by a multi-stage classifier. Classification was performed to obtain cyan colored particles. The obtained colored particles had a weight average particle size of 5.9 μm and a number average particle size of 5.0 μm.

With respect to 100 parts by weight of the colored particles, BE
2.0 parts by weight of hydrophobic silica having a specific surface area of 200 m ² / g by the T method was added and mixed to obtain a pulverized toner 2.

<Magnetic Particles for Contact-Charged Magnetic Brush> (Core Particles) 200 parts by weight of hydrogen-reduced Zn—Cu ferrite (number average particle diameter 40.0 μm, specific resistance 5 × 10 ⁶ Ωcm) (coat resin solution) Polycarbonate 0 parts by weight Epoxy-modified silicone resin 1.0 parts by weight Conductive titanium oxide 4.0 parts by weight Tetrafluoroethylene resin particles (0.25 μm) 0.2 parts by weight Xylene solution 14.0 parts by weight

Each of the above prescriptions of the coating resin solution was dispersed for 2 hours using a paint shaker containing glass beads to prepare a coating resin solution. This was coated on the above-mentioned core particles using the above-mentioned spira coater, and dried at 150 ° C. for 1 hour. The specific resistance of the obtained magnetic particles for contact charging magnetic brush is 8.9 × 10 ⁶ Ωcm, and the number average particle diameter is 4
It was 0.1 μm. The magnetization intensity at 1 kOe (σ ₁₀₀₀ ) was 250.3 emu / cm ³ (the true specific gravity of the magnetic particles was 5.02 g / cm ³ ).

The specific resistance and the number average particle diameter of the magnetic particles for the contact charging magnetic brush and the core particles used here were determined by the above-mentioned method for measuring the characteristics of the magnetic carrier for development.

<Example 1> Carrier A and toner 1 described above
Was mixed at a toner concentration of 8% by weight to obtain a two-component developer. The toner has a triboelectric charge of −25.0 μC / g.
Met.

An image was formed from this developer using a modified full-color laser copying machine CLC-500 manufactured by Canon. FIG. 1 is a schematic view showing the periphery of the developing section, and the description will be made with reference to FIG. The distance A between the developer carrier (developing sleeve) 1 and the developer regulating member (magnetic blade) 8 of the full color laser copying machine made by Canon is 600 μm, the developing sleeve 1 and the electrostatic latent image carrier (photosensitive drum) 2 Was set to 400 μm. The developing nip C at this time was 5 mm.

The developing sleeve is a developing sleeve (material: SU) used in the developing unit of the CLC-500.
S, Hitachi Metals Co., Ltd., 25φ) was sandblasted using a pneumatic blaster (Fuji Manufacturing Co., Ltd.), and Ra =
A blast sleeve (Ra / Sm = 0.07) with 2.1 μm and Sm = 29.6 μm was used.

The peripheral speed ratio between the developing sleeve 1 and the photosensitive drum 2 is 2.2: 1, the traveling directions are counter directions to each other as shown in FIG.
The magnetic field is 1 kOe, and the developing condition is such that the alternating electric field is 1800 V having a waveform as shown in FIG. 2 and the frequency is 3000 Hz, and the developing bias is -480.
V was set. Further, the toner development contrast (V _cont ) is 350 V, and the fog removal voltage (V _back ) is 8.
0 V was applied.

The voltage applied to the contact charging member 3 is as follows.
A DC bias of -560V was used.

As a photosensitive drum, an OPC made up of an aluminum drum made of φ80 and having the following five functional layers
A photoreceptor was used.

The first layer is an undercoat layer in order from the aluminum base layer side,
The second layer is a positive charge injection prevention layer, the third layer is a charge generation layer,
The layer is a charge transport layer, and the fifth layer is a charge injection layer. This charge injection layer is made by dispersing SnO ₂ ultrafine particles in a photo-curable acrylic resin, and further dispersing ethylene tetrafluoride resin particles in order to increase the contact time between the contact charging member and the photoreceptor and to perform uniform charging. It is. Specifically, antimony-doped, low-resistance Sn having a particle size of about 0.03 μm is used.
70% by weight of O ₂ particles based on the resin, and a particle size of 0.2
It is a dispersion in which 20% by weight of 5 μm tetrafluoroethylene resin particles and 1.2% by weight of a dispersant are dispersed. The surface resistance of this photosensitive drum was 1 × 10 ¹² Ω.

An image was formed under the above-mentioned developing conditions. As a result, an excellent image having very fine line reproducibility and a high solid image density was obtained. Further, no image disturbance and toner fogging in the image area and the non-image area due to carrier adhesion were observed.

The toner transfer efficiency when the solid black image was transferred from the photosensitive drum to the paper was 99.5%
Therefore, it was at a level that could sufficiently cope with the cleanerless process.

In fact, when the cleaner was removed and 10,000 images were printed, the chargeability of the charged magnetic brush did not change at all, and no charged ghost or the like was observed.

Table 2 shows the results of this example. Table 2 also shows the results of the following Examples and Comparative Examples.

<Example 2> The same developer as that of Example 1 was used, and the developing conditions were changed to an alternating electric field of 2000 V.
(Peak-to-peak voltage), and an image was displayed in exactly the same manner as in Example 1 except that the frequency was changed to a rectangular wave of 1000 Hz.

As a result, a satisfactory image having no problem was obtained.

<Example 3> Carrier B and Toner 1 were mixed at a toner concentration of 5% by weight to obtain a two-component developer. The triboelectric charge of the toner was -22.1 μC / g.

An image output durability test for 10,000 images was performed in exactly the same manner as in Example 1. Fine line reproducibility, carrier adhesion, toner fog, and the like were as good as those of Example 1.

Example 4 A two-component developer was obtained by mixing the carrier C and the toner 1 so that the toner concentration was 8% by weight. The triboelectric charge of the toner was -24.9 μC / g.

An image was displayed in exactly the same manner as in Example 1, and good results were obtained as in Example 1.

Example 5 A two-component developer was obtained by mixing carrier A and toner 2 so that the toner concentration was 8% by weight. The triboelectric charge of the toner was −24.0 μC / g.

An image was displayed in exactly the same manner as in Example 1. The same good results as in Example 1 were obtained with respect to carrier adhesion and toner fog. However, when the transfer efficiency was measured in the same manner as in Example 1, it was 90%.

Example 6 A photosensitive drum identical to that of Example 1 except that the tetrafluoroethylene resin particles and the dispersant were not dispersed in the fifth charge injection layer of the surface functional layer of the photosensitive drum was used. An image was formed using the same developer and developing conditions as in Example 1. The surface resistance of the photosensitive drum was 3 × 10 ¹⁰ Ω.

As a result, good results were obtained as in Example 1.

<Comparative Example 1> Carrier D and Toner 1 were mixed at a toner concentration of 8% by weight to obtain a two-component developer. The triboelectric charge of the toner was -23.5 μC / g.

An image was formed in exactly the same manner as in Example 1. As a result, the solid image density was sufficient, but the reproducibility of fine lines was low.
Both carrier adhesion and toner fog resulted in poor results.

<Comparative Example 2> The low-resistance SnO ₂ particles added to the fifth charge injection layer of the surface functional layer of the photosensitive drum of Example 1 were added to the photo-curable acrylic resin in an amount of 1%.
An image was formed using exactly the same photosensitive drum except that the dispersion was performed by 25% by weight, and using the same developer and developing conditions as in Example 1. The surface resistance of the photosensitive drum is 5 × 1
It was ⁹ Ω.

As a result, it was found that the reproducibility of fine lines was poor, and when viewed microscopically, image deletion occurred.

Comparative Example 3 The same photosensitive drum was used except that the fifth functional layer of the surface functional layer of the photosensitive drum of Example 1 was used, and the other developer and developing conditions were completely the same. An image was displayed in the same manner as in Example 1. The surface resistance of the photosensitive drum was 3 × 10 ¹⁶ Ω.

As a result, the occurrence of charging ghost, the deterioration of fine line reproducibility and the occurrence of toner fog were observed.

[0153]

[Table 2]

The evaluation methods and criteria in Table 2 are as follows.

(1) Image density: The image density was measured as a relative density of an image formed on plain paper using Macbeth color checker RD-1255 manufactured by Macbeth equipped with an SPI filter.

(2) Line reproducibility: Evaluation was made visually with reference to the original image and the standard sample.

(3) Attachment of carrier: A solid white image is formed, and a portion on the photosensitive drum between the developing section and the cleaner section is sampled by bringing a transparent adhesive tape into close contact therewith.
counts the number of magnetic carrier particles having adhered to the photosensitive drum in the m × 5 cm, and calculates the number of adhering carrier per 1 cm ^2. Excellent: less than 10 pieces / cm ² Good: 10 pieces to less than 20 pieces / cm ² Acceptable: 20 pieces to less than 50 pieces / cm ² Somewhat bad: 50 pieces to less than 100 pieces / cm ² Bad: 100 pieces / cm ² or more

(4) Fog The average reflectance Dr (%) of plain paper before image formation was measured with a densitometer TC-6MC manufactured by Tokyo Denshoku Co., Ltd. On the other hand, a solid white image was formed on plain paper, and the reflectance Ds (%) of the solid white image was measured. Fog (%)
Is calculated from the following equation: fog (%) = Dr (%)-Ds (%). Excellent: less than 1.0 (%) Good: less than 1.0 to 1.5 (%) Acceptable: less than 1.5 to 2.0 (%) Somewhat poor: Less than 2.0 to 3.0 (%) Bad : 3.0 (%) or more

[0159]

According to the present invention, in an image forming method having a contact charging device for charging a latent image carrier by bringing a charging member into contact with the latent image carrier, a contact two-component using a developing magnetic carrier having substantially high resistance is used. By performing the system AC development, it is possible to achieve high image quality with excellent fine line reproducibility and no toner fog or carrier adhesion.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an image forming apparatus suitable for the present invention.

FIG. 2 shows a developing bias waveform used in an embodiment of the present invention.

FIG. 3 is a schematic view of an apparatus for measuring a specific resistance of a carrier, a carrier core, and a metal oxide according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 developing sleeve (developer carrier) 2 photosensitive drum (latent image carrier) 3 contact charging member 4 transfer drum 5 exposure means 6 cleaner 7 transfer material 21 lower electrode 22 upper electrode 23 insulator 24 ammeter 25 voltmeter 26 constant Voltage device 27 Carrier 28 Guide ring d Sample thickness E Resistance measurement cell

──────────────────────────────────────────────────続 き Continuing on the front page (72) Katsuaki Kobayashi, Inventor 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Koichi Hashimoto 3-30-2, Shimomaruko, Ota-ku, Tokyo Canon Inside (72) Inventor Masaru Hibino 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-5-249748 (JP, A) JP-A-7-271194 (JP) JP-A 8-69165 (JP, A) JP-A 5-237369 (JP, A) JP-A 8-6303 (JP, A) JP-A 5-150664 (JP, A) 7-295389 (JP, A) JP-A-8-95288 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/09

Claims (11)

(57) [Claims] An electrostatic latent image carrier having a charge injection layer having a surface resistance of 1 × 10 ¹⁰ to 1 × 10 ¹⁶ Ω, and a developer carrying a two-component developer containing a magnetic carrier and a toner An image forming method in which a carrier is disposed to face and developed, wherein the magnetic carrier is a coated carrier, and a specific resistance of a carrier core of the magnetic carrier is 1 × 10 ¹⁰ Ωcm or more;
The magnetic carrier has a specific resistance of 1 × 10 ¹² Ωcm or more, the magnetic carrier has a number average particle size of 5 to 100 μm, and the developer magnetic brush formed on the developer carrier is And developing while applying an alternating electric field. 2. A two-component carrier core of the magnetic carrier constituting the developer, an image according to claim 1, characterized that you have a binder resin and a surface magnetic metal oxide lipophilic treatment Forming method. 3. A carrier core of the magnetic carrier constituting a two-component type developer has a binder resin, magnetic metal oxide surface was lipophilic treatment and a non-magnetic metal oxide, said magnetic <br/> according to claim 1, sexual metal oxide ratio r _b / r _a between the number average particle diameter r _b of the number average particle diameter r _a and the non-magnetic metal oxide particles having a particle is equal to or greater than 1.0 Image forming method. 4. The image forming method according to claim 3, wherein the ratio of the magnetic metal oxide to the total amount of the metal oxide is 30 to 95% by weight. 5. The image forming method according to claim 2, wherein the binder resin of the carrier core particles is a curable resin, and is a resin carrier core particle obtained by a polymerization method. . 6. The magnetic force of a magnetic carrier constituting a two-component developer in a magnetic field of 1 kOe is 40 to 2
The image forming method according to claim 1, wherein the value is 50 emu / cm ³ . 7. A two- component system wherein the charging member of the electrostatic latent image carrier is a magnetic brush composed of magnetic particles, the magnetic particles having a specific resistance of 1 × 10 ⁵ to 1 × 10 ⁸ Ωcm. The image forming method according to claim 1, wherein the magnetic particles are magnetic particles having an intensity higher than that of a magnetic carrier constituting a developer in a magnetic field of 1 kOe. 8. The image forming method according to claim 1, wherein a part or all of the toner constituting the two-component developer is manufactured by a polymerization method. 9. The specific surface area by the BET method is 100 m ² /
The image forming method according to any one of claims 1 to 8, wherein the inorganic fine particles or the organic fine particles having a weight of at least g or a mixture thereof are contained in the two-component developer as an external additive. 10. The method according to claim 1, wherein the direction of rotation of the developer carrier and the direction of rotation of the latent image carrier are counter directions to each other at the facing portion. Image forming method. 11. The developer carrier has a surface shape of 0.2 μm ≦ center line average roughness (Ra) ≦ 5.0 μm 10 μm ≦ average interval of unevenness (Sm) ≦ 80 μm 0.05 ≦ Ra / Sm ≦ 0. .5, wherein the above condition is satisfied.
The image forming method according to any one of the above.