JPH01126665A - Image forming method - Google Patents

Abstract

PURPOSE:To stably form distinct images many times without the fault of cleaning by making an oscillating electric field act on a developed area with the aid of a developer layer having the specified thickness of layer so that an electrostatic latent image on a latent image carrier is developed and making toner contain organic corpuscules having smaller diameter than that of binding resin particles. CONSTITUTION:The electrostatic latent image on the latent image carrier is developed in a state where the oscillating electric field is made to act on the developed area with the aid of the developer layer, which is a thin layer having the thickness smaller than a gap between the latent image carrier and a developer carrier on the developed area, formed on the developer carrier. In such a case, the toner constituting the developer is made to contain the binding resin particles, inorganic corpuscules and the organic corpuscules having smaller diameter than that of the binding resin particle. Therefore, the fluidity of the toner is improved with the inorganic corpuscules and excellent development is made manifest. And the physical and electrostatic sticking force of the toner to the latent image carrier can be weakened with what is called lubricant action by the organic corpuscules, so that residual toner can be easily cleaned. Thus, the distinct images can be stably formed many times.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming method applied to, for example, electrophotography, electrostatic recording, electrostatic printing, etc., and more specifically, an image forming method including a developing step. It is about the method.

[Technology background]

At present, as a method for forming a visible image from certain image information, methods using electrostatic latent images, such as electrophotography, electrostatic recording, and electrostatic printing, are widely used.

For example, in electrophotography, a latent image carrier having a photosensitive layer made of a photoconductive material is given an electrostatic charge, and then the original is exposed to light on the surface of the latent image carrier. An electrostatic latent image corresponding to the image is formed, and this electrostatic latent image is developed with a developer to form a toner image. This toner image is transferred to a transfer material such as paper and then fixed by heating, pressure, etc. to form a copy image. On the other hand, after the transfer process, the latent image carrier is neutralized, residual toner remaining on the latent image carrier without being transferred is cleaned, and then the next copy image is formed.

Conventionally, from the viewpoint of forming clear images without fog, a single-component developer consisting only of small-diameter magnetic toner or a two-component developer consisting of small-diameter toner and small-diameter carrier was used to develop a latent image carrier. A method in which a thin developer layer with a non-contact thickness is formed on a developer transport carrier, and an electrostatic latent image on the latent image carrier is developed with the thin developer layer while applying an oscillating electric field to the development area. is proposed.

On the other hand, in order to improve the toner transportability by the developer transport carrier, the toner needs to have high fluidity.

For this reason, toners have conventionally been prepared by adding and mixing fine silica powder to binder resin particles.

[Problem that the invention seeks to solve]

However, in order to form a thin developer layer, it is necessary to apply a large shearing force to the developer, resulting in the filming phenomenon in which toner substances adhere to the developer transport carrier or carrier and form a film. This tends to occur, and as a result, when images are formed many times, the toner transportability by the developer transporting carrier becomes unstable, resulting in problems such as a decrease in image density, toner scattering, and fogging.

In addition, especially in toner containing fine silica powder, since the fine silica powder is quite hard, cleaning the residual toner with a cleaning blade that is placed in contact with the latent image carrier with a large pressing force will remove the fine silica powder. The powder is caught between the cleaning blade and the latent image carrier, and the surface of the latent image carrier is rubbed, resulting in damage such as minute depressions and linear scratches on the surface of the latent image carrier. There is a problem. If the surface of the latent image carrier is damaged in this way, linear streaks may appear in the copied image, and fine silica powder etc. may become embedded in the minute recesses, making it difficult to clean. When forming a toner, there is a problem in that toner adheres to the embedded silica fine powder and is fixed, resulting in black spot-like stains (black spots) on the image.

In addition, toner containing fine silica powder has a large electrostatic adhesion force to the latent image carrier.
There is a problem in that the transfer rate of a toner image formed by development onto a transfer material is generally low, resulting in a decrease in image density.

Particularly, when the toner is used as a one-component developer, since the toner contains magnetic powder, the weight of the toner increases, resulting in a further reduction in the transfer rate.

The present invention has been made based on the above circumstances, and has good developability and cleanability, and can stably produce clear images with high image density and no fog over many times without cleaning defects. The present invention provides an image forming method that can form an image.

[Means for solving problems]

In the image forming method of the present invention, a thin developer layer having a thickness smaller than the gap between the latent image carrier and the developer transport carrier in the development area is formed on the developer transport carrier. It includes a developing step of developing an electrostatic latent image on a latent image carrier while applying an oscillating electric field, and the toner constituting the developer is composed of binder resin particles, inorganic fine particles, and the binder resin particles. is characterized by comprising small-diameter organic fine particles.

[Function and effect of the invention]

According to the present invention, since the toner constituting the developer includes binder resin particles, inorganic fine particles, and organic fine particles smaller in diameter than the binder resin particles, the fluidity of the toner is improved by the inorganic fine particles. The improving effect exhibits good developing performance, and the so-called lubricating effect of the organic particles weakens the physical and electrostatic adhesion of the toner to the latent image carrier, making it easy to clean residual toner. can. Therefore, when using a cleaning blade, good leaning can be achieved with a small pressure contact force of the cleaning blade against the latent image carrier, and as a result, damage to the surface of the latent image carrier due to inorganic fine particles can be prevented. This allows images without black spots to be stably formed many times.

The physical and electrostatic adhesion of the toner to the developer transport carrier is also weakened by the so-called lubricating action of the organic particles, so a relatively large shearing force is applied to the toner in order to make the developer layer thin. Even if the toner substance is applied, adhesion of the toner substance to the developer transport carrier or carrier is suppressed, and even if the toner substance adheres to the developer transport carrier or carrier, the toner substance is removed by the appropriate polishing performance of the organic fine particles. As a result, the thin developer layer can be stably conveyed to the development area, and clear images with high image density and no capri can be stably formed over many times.

The physical and electrostatic adhesion of the toner to the latent image carrier is weakened by the so-called lubricating action of the organic fine particles, so in the transfer process, the transfer rate of the toner image to the transfer material increases, resulting in an image density. It is possible to form a high quality image.

Furthermore, as a result of the high transfer rate, the amount of residual toner remaining on the latent image carrier without being transferred is reduced, making it easier to clean the residual toner.

[Specific structure of the invention]

In the image forming method of the present invention, a developer made of a specific toner is used. That is, the toner constituting the developer includes binder resin particles, inorganic fine particles, and organic fine particles having a smaller diameter than the binder resin particles. In the present invention, any type of developer can be used, such as a one-component developer that does not contain a carrier or a two-component developer that contains a carrier.

The organic fine particles constituting the toner have a smaller diameter than the binder resin particles, for example, the average diameter of -order particles (particles separated into individual unit particles) is preferably 0°O1 to 5μ, particularly 0.1-3. OJrm is preferred. When the average diameter of the organic fine particles is too large, toner transportability deteriorates, which tends to cause a decrease in image density. On the other hand, if the average diameter of the organic fine particles is too small, sufficient leaning properties cannot be obtained.

The proportion of the organic fine particles is preferably 0.01 to 3.0% by weight, particularly preferably 0.1 to 2.0% by weight, based on the total toner. If the proportion of organic fine particles is too small, the toner transportability will be reduced, leading to a decrease in image density (and sufficient leaning properties will not be obtained.On the other hand, if the proportion of organic fine particles is too large, the toner's triboelectric charging properties will be reduced). easily inhibited.

The organic substance for forming the organic fine particles is not particularly limited, but vinyl polymers are preferred because they are relatively hard and provide appropriate polishing performance.

Such vinyl polymers can be produced by various polymerization methods such as emulsion polymerization and suspension polymerization, but the emulsion polymerization method is preferred because small-diameter, spherical organic fine particles can be efficiently obtained. In particular, in systems where the monomer itself for obtaining the vinyl polymer has an emulsifying effect, it is preferable to obtain the vinyl polymer by emulsion polymerization without using an emulsifier.

Examples of the vinyl polymer include acrylic polymers, styrene polymers, vinyl group-containing fluororesins, and among them, acrylic polymers are preferred.

Acrylic polymers are homopolymers or copolymers obtained by polymerizing monomers selected from acrylic acid, acrylic esters, methacrylic acid, and methacrylic esters. Acrylic monomers used to obtain such acrylic polymers include acrylic acid,
Methyl acrylate, ethyl acrylate, n-acrylate
Butyl, isobutyl acrylate, propyl acrylate,
n-octyl acrylate, dodecyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethynobyl acrylate, phenyl acrylate, methyl α-chloroacrylate, methacrylic acid, methyl methacrylate, methacrylic acid Ethyl, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, lauryl methacrylate, methacrylic acid 2
-Ethylhexyl, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate,
Diethylaminoethyl methacrylate and the like can be mentioned.

Among the acrylic polymers, polymethyl methacrylate is particularly preferred. Polymethyl methacrylate makes it possible to easily obtain uniform, small-diameter organic fine particles, and also provides suitable polishing performance, as well as the physical adhesion of toner to latent image carriers or developer transport carriers. Since it is possible to suitably weaken the - layer, excellent effects can be exhibited.

Furthermore, since there is no risk of inhibiting the triboelectric charging properties of the toner, stable developing performance can be obtained.

The acrylic polymer may be copolymerized with other monomers, if necessary.

In this case, it is preferable to use the acrylic monomer in a proportion of 50% by weight or more in the monomer composition. Such other monomers include styrene, O-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-n-butylstyrene. , p-tert-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene, p-n-dodecylstyrene, p-methoxystyrene, p -Styrenic monomers such as 7-enylstyrene, p-chlorostyrene, 3,4-dichlorostyrene,
Acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide; Vinyl esters such as vinyl acetate, vinyl butyrate, and vinyl benzoate; Vinyl ethers such as vinyl methyl ether and vinyl ethyl ether; Vinyl ketones such as vinyl methyl ketone ; dienes such as butadiene and isoprene; unsaturated carboxylic acids such as maleic acid and fumaric acid; and others.

The inorganic fine particles constituting the toner are, for example, -order particles/particles (particles separated into individual unit particles) with an average diameter of 2
It is preferably less than μ, particularly preferably less than 1p. When the average diameter of the inorganic fine particles is too large, the surface of the latent image carrier is likely to be damaged.

The proportion of the inorganic fine particles is preferably 0.05 to 2.0% by weight, particularly preferably 0.1 to 1.0% by weight, based on the total toner. When the proportion of inorganic fine particles is too small, the fluidity of the toner decreases, while when the proportion is too large, the surface of the latent image carrier is likely to be damaged.

The constituent materials of the inorganic fine particles are not particularly limited, but include, for example, oxides such as silica, titanium oxide, aluminum oxide, zirconium oxide, barium titanate, lead titanate, and barium carbonate; nitrides such as silicon nitride and boron nitride; and carbide. Carbides such as silicon, aluminum carbide, titanium carbide;
Others can be mentioned. These inorganic fine particles may be surface-treated.

Particularly preferred are silica fine particles or surface-treated silica fine particles. As the surface treatment agent, for example, a silane coupling agent, a titanium coupling agent, etc. can be used. The surface-treated silica fine particles are highly stable against environmental changes such as temperature and humidity, so that the environmental dependence of the triboelectric charging property of the toner can be suppressed to a small level.

Two or more types of inorganic fine particles may be used in combination. In this case, it is preferable to always use silica fine particles or surface-treated silica fine particles.

- The above organic fine particles and inorganic fine particles are preferably used by being added to and mixed with the binder resin particle powder from the outside. Specifically, by mixing binder resin particles, organic fine particles, and inorganic fine particles using a mixing device such as a V-type blender, organic fine particles and inorganic fine particles are present on the surface of the binder resin particles. It is preferable to let

The binder resin particles constituting the toner are particles in which, for example, a magnetic substance, a colorant, an offset inhibitor, a charge control agent, etc. are contained in the binder resin.

The binder resin is not particularly limited, and various resins can be used. Specifically, styrene resins, acrylic resins, styrene-acrylic copolymer resins, epoxy resins, polyester resins, etc. can be mentioned.

These resins may be used in combination.

The styrene/acrylic copolymer resin used as the binder resin is a resin made of a copolymer of a styrene monomer and an acrylic monomer. Styrene monomers include styrene, 0-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-n-butylstyrene, p-methylstyrene, -tert-butylstyrene, p-n-
hexylstyrene, p-n-octylstyrene, p-n
-nonylstyrene, 1p-n-decylstyrene, p-n
-dodecylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, 3°4-dichlorostyrene and the like.

Acrylic monomers include acrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, and n-acrylate.
-octyl, dodecyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 112-90 ethyl acrylate, a')lylWI phenyl, methyl α-chloroacrylate, methacrylic acid,
Methyl methacrylate, ethyl methacrylate, propyl methacrylate, n,-butyl methacrylate, isobutyl meccrylate, n-octyl methacrylate, dodecyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate , dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide, and others.

Magnetic substances include substances that are strongly magnetized in the direction of a magnetic field, such as metals or alloys that exhibit ferromagnetism such as iron, ferrite, and magnetite, such as iron, nickel, and cobalt, compounds containing these elements, and ferromagnetic elements. Alloys that do not contain manganese but become ferromagnetic through appropriate heat treatment, such as manganese-copper-aluminum, manganese-copper-tin, etc. Alloys called Heusler alloys that contain manganese and a body, dioxide Chromium, and others can be mentioned. The average particle size of the magnetic material is 0.1
It is preferable that it is uniformly dispersed and contained in the form of a fine powder of ~1 μm. When the toner is used as a -component developer, the content of the magnetic material is preferably 20 to 80% by weight, particularly preferably 30 to 70% by weight, based on the total toner.

Examples of colorants include carbon black, nigrosine dye, aniline blue, calco oil blue, chrome yellow, ultramarine blue, Denipon oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green offsalate,
Mention may be made of lamp black, rose bengal, mixtures thereof, and others.

Examples of the charge control agent include metal complex dyes, nigrosine dyes, ammonium salt compounds, and the like.

Examples of anti-offset agents include low softening point polyolefins, high melting point paraffin waxes, silicone resins, fatty acid esters or partially saponified products thereof, fatty acid amide compounds, higher alcohols, and the like.

When a two-component developer is used, a carrier is mixed with the above toner to form the developer.

Such a carrier is not particularly limited, and conventionally known carriers can be used. Specifically, either a carrier composed of only magnetic particles or a resin-coated carrier in which the surface of magnetic particles is coated with resin can be used.

As the resin for coating the carrier, a styrene-acrylic copolymer can be preferably used.

Basically, such styrene/acrylic copolymer is
It is a copolymer obtained by copolymerizing a styrene monomer and an acrylic monomer, and in particular, a styrene monomer and an acrylic monomer.
Preference is given to copolymers obtained by polymerization with acrylic acid or its esters and/or methacrylic acid or its esters. Examples of styrenic monomers include styrene, 0-methylstyrene, methylstyrene, p-methylstyrene, α-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-n-butylstyrene, p-tert-butylstyrene, p-n-
hexylstyrene, p-n-octylstyrene, pn-
Examples include nonylstyrene, pn-decylstyrene, p-n-dodecylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, 3.4-') chlorostyrene, and the like. Examples of acrylic monomers include acrylic acid: methyl methacrylate, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate,
2-ethylhexyl acrylate, cyclohexyl acrylate, n-octyl acrylate, inoctyl acrylate, n-dodecyl acrylate, 2-hydroxyethyl acrylate, methoxyethyl acrylate, 2-acrylate
Acrylic acid esters such as chloroethyl, benzyl acrylate, n-methylaminoethyl acrylate, dimethylaminoethyl acrylate; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, methacrylate Isobutyl methacrylate, tert-butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, n-octyl methacrylate, inoctyl methacrylate, n-dodecyl methacrylate, 2- and droxyethyl methacrylate, benzyl methacrylate, n-methacrylate
-Methacrylic acid esters such as methylaminoethyl and dimethylaminoethyl methacrylate; and the like. Among these, methyl methacrylate is particularly preferably used from the viewpoint of durability.

The magnetic particles constituting the carrier include materials that are strongly magnetized in the direction of a magnetic field, such as iron, ferrite,
Metals or alloys that exhibit ferromagnetism, such as magnetite, iron, nickel, and cobalt, or compounds that contain these elements; alloys that do not contain ferromagnetic elements but become ferromagnetic through appropriate heat treatment, e.g. An alloy of a type called Heusler alloy such as manganese-copper-aluminum or manganese-copper-tin, or particles made of chromium dioxide or the like can be used.

The method for producing the resin-coated carrier is not particularly limited, but in a specific example, a coating liquid prepared by dissolving a coating resin component in a solvent is applied to the surface of the magnetic particles, and then usually heated. Dry to remove the solvent by volatilization. Then, a resin-coated carrier can be manufactured by drying as necessary.

The thickness of the coating layer in the resin-coated carrier is not particularly limited, but specifically, it is preferably about 0.01 to 5.0p, particularly preferably about 0.1 to 3p. Further, the quantitative ratio of the coating layer to the magnetic particles is 0.
It is preferably 0.01 to 10% by weight, especially 0.05% by weight.
It is preferably 5% by weight.

The average particle size of the carrier is preferably 40 to 200 iIM, particularly preferably 50 to 150 n. When the average particle size of the carrier is too small, a so-called carrier adhesion phenomenon occurs in which the carrier adheres to and is fixed on the electrostatic latent image, resulting in an unclear image; on the other hand, when the average particle size of the carrier is too large In this case, image distortion may occur.

Here, the average particle diameter (weight) of the carrier is a value measured using "Microtrack" (manufactured by Nikkiso Co., Ltd.).

Next, each step of the image forming method of the present invention will be specifically explained.

(Developing process) Using a one-component developer or a two-component developer composed of a toner comprising binder resin particles, inorganic fine particles, and organic fine particles smaller in diameter than the binder resin particles. , a thin developer layer having a thickness smaller than the gap between the latent image carrier and the developer transport carrier in the development region is formed on the developer transport carrier, and this developer layer generates an oscillating electric field in the development region. The electrostatic latent image on the latent image carrier is developed in a state where the electrostatic latent image is applied.

The oscillating electric field can be created by an alternating current bias voltage.

The gap (hereinafter also referred to as "development gap") Dsd between the latent image carrier and the developer transport carrier in the development area is 200
It is preferable that it is in the range of ~200 On.

From this point of view, the thickness of the thin developer layer is 2000 mm. i
It is preferably 11 or less, more preferably 1000n or less, and particularly preferably 10 to 500n.

The developer transport carrier for transporting the thin developer layer to the development area is not particularly limited, but for example, one having the same structure as the conventional one to which a bias voltage can be applied can be used. In particular, a structure in which a cylindrical developing sleeve carrying a developer layer and a magnetic roll having a plurality of magnetic poles is preferably used.

The means for forming a thin developer layer on the developer transport carrier is not particularly limited, but for example, the developer layer may be formed into a thin layer using a regulation blade whose tip is placed close to the surface of the developer transport carrier. For example, an elastic plate-like thin layer forming member is placed in elastic pressure contact with the surface of the developer transporting carrier, and the developer is passed between the thin layer forming member and the developer transporting carrier. Accordingly, means for making the developer layer thin can be used. When a thin layer forming member is used, it is preferably an elastic plate that is pressed against the developer transport carrier such that its tip faces upstream in the rotational direction of the developer transport carrier.

By making the developer layer supported on the developer transporting carrier thin, the development gap Dsd can be made sufficiently small, and therefore the bias voltage required to form the oscillating electric field can be lowered, so that the toner This has the advantage of reducing scattering and preventing the occurrence of leakage discharge or the like based on the bias voltage from the surface of the developing sleeve. In addition, by reducing the development gap Dsd, the electric field strength formed in the development area by the electrostatic latent image formed on the latent image carrier increases, resulting in subtle changes in gradation and fine patterns. can also be developed well.

However, if the developer layer on the developer transport carrier is thin, the amount of toner transported to the development area generally decreases, and as a result, the amount of toner that adheres to the electrostatic latent image on the latent image carrier is insufficient. Oh yeah, there it is. Therefore, it is preferable to rotate the developing sleeve at high speed to increase the amount of toner conveyed. Actually, it is preferable that the linear velocity of the developing sleeve in the developing area is within 10 times the linear velocity of the latent image carrier.

(Transfer Step) The toner image on the latent image carrier obtained by development is transferred to a transfer material such as paper.

In this transfer step, an electrostatic transfer method can be preferably used. Specifically, for example, a transfer device that generates DC corona discharge is arranged to face the latent image carrier through the transfer body, and the latent image is carried by applying DC corona discharge to the transfer body from the back side. The toner carried on the surface of the body is transferred to the surface of the transfer body.

(Cleaning Step) The cleaning means is not particularly limited, but a cleaning device having a cleaning blade disposed in contact with the surface of the latent image carrier can be preferably used. According to this cleaning device, residual toner remaining on the latent image carrier without being transferred is scraped off by rubbing the surface of the latent image carrier with the cleaning blade.

In order to facilitate cleaning, it is preferable to add a static elimination process to neutralize the surface of the latent image carrier before the cleaning process. This static elimination step can be performed, for example, using a static eliminator that generates AC corona discharge.

(Fixing process) The transfer material onto which the toner image has been transferred in the transfer process is subjected to a fixing process using a heat fixing device, a pressure fixing device, etc.
A fixed image is thereby formed.

FIG. 1 is an explanatory diagram showing an example of an image forming apparatus that can be used to carry out the image forming method of the present invention. On the right side of the figure, IO is a latent image carrier, 21 is a charger, 22 is an exposure optical system, 23 is a developer, 25 is a static elimination lamp, 26 is a transfer electrode, 27 is a separation electrode, 28 is a static elimination electrode, 29 is a fixing device, 40 is a document table, and 50 is a cleaning device. This apparatus is of a type in which the exposure optical system 22 is fixedly arranged and the document table 30 is moved.

The surface of the latent image carrier 10 is uniformly charged by the charger 21, and the charged surface of the latent image carrier 10 is exposed to original light by the exposure optical system 22 to form an original onto the latent image carrier 20. A corresponding electrostatic latent image is formed. This electrostatic latent image is developed by a developing device 23 to form a toner image.

After the toner image thus obtained is neutralized by the static eliminating lamp 25 and is in a state where it can be easily transferred, the toner image is transferred to the transfer electrode 2.
6, the image is transferred onto the transfer paper P. Transfer paper P is separated electrode 2
It is separated from the latent image carrier lO by 7 and subjected to fixing processing in a fixing device 29, thereby forming a fixed image. On the other hand, the charge on the latent image carrier 10 is eliminated by the charge eliminating electrode 2B, and the latent image carrier 10 is not transferred by the cleaning device 50.
Any residual toner left on the surface is scraped off.

The details of the developing device 23 are shown in FIG. In the same figure, 61
1 is a developing sleeve, and 62 is a magnetic roll. These developing sleeve 61 and magnetic roll 62 constitute a developer transport carrier. The magnetic roll 62 has a structure in which north poles and south poles are alternately arranged along the circumference. 64 is a thin layer forming member, 65 is a first stirring member, 66 is a second stirring member, 67 is a toner supply container, 68 is a toner supply roller, 69 is a developer reservoir, 70 is a bias power source, and 71 is a developing area It is. The first stirring member 65 and the second stirring member 66 have a structure in which they are rotated in opposite directions so that their stirring regions overlap without colliding with each other, as shown by the arrows.

In this developing device 23, the developer in the developer reservoir 69 is sufficiently stirred and mixed by the stirring members 65 and 66.
The developer is adhered to the surface of the developing sleeve 61 by the conveying force of the developing sleeve 61 rotating in the direction of the arrow and the magnetic roll 62 rotating in the opposite direction.

A plate-shaped thin layer forming member 64 made of an elastic material is held in pressure contact with the surface of the developing sleeve 61 on one side near the tip thereof. The thickness of the developer layer conveyed to the development area 71 is regulated by the thin layer forming member 64 to form a thin layer.

The developer layer formed into a thin layer by the thin layer forming member 64 preferably faces the electrostatic latent image formed on the latent image carrier 20 rotating in the direction of the arrow with a slight gap therebetween. The electrostatic latent image on the latent image carrier 10 is transferred to the developing area 71 in a non-contact state, and is subjected to the action of an oscillating electric field from the bias power source 70, in which the electrostatic latent image on the latent image carrier 10 is formed by a thin developer layer. It is developed and a toner image is formed.

The thickness of the thin developer layer formed on the developing sleeve is
For example, using a "Nikon Profile Projector" (manufactured by Nippon Kogaku Co., Ltd.), the position of the projected image of the developing sleeve onto the screen and the projected image onto the screen with a thin developer layer formed on the developing sleeve can be determined. The thickness of the developer layer can be determined by comparison.

The thin layer forming member 64 can be made of magnetic or non-magnetic metal, metal compound, plastic, rubber, etc., with one end fixed by a fixing member and imparted with elasticity, and its thickness must be extremely thin. is preferable, and it is preferable that the thickness is uniform. Specifically, the thickness is preferably 50 to 500 trs.

The thin layer forming member 64 is elastically pressed against the developing sleeve 61 by wiping one side near its tip, and the developer is passed little by little between the thin layer forming member 64 and the developing sleeve 61. In this way, the amount of developer conveyed is regulated. Impurities, aggregates, etc. in the developer are prevented from entering the developing area 71 by the thin layer forming member 64.
The developer layer conveyed to No. 1 is a thin layer, and its thickness is uniform and stable. Furthermore, the amount of developer conveyed to the developing area 71 can be sufficiently controlled by changing the pressing force and contact angle of the thin layer forming member 64 against the developing sleeve 61.

In the present invention, since the developer layer formed on the developer transport carrier is a thin layer, the latent image carrier 10 and the developing sleeve 6
It is possible to considerably reduce the development gap Dsd between 1 and 1, and it is possible to sufficiently perform development by a so-called non-contact development method.

When reducing the development gap Dsd in this way,
Since the electric field strength in the developing region 71 is large, sufficient development can be performed even if the bias voltage applied to the developing sleeve 61 is reduced, and as a result, there is an advantage that bias voltage leakage, etc. is reduced. Furthermore, since the contrast of the electrostatic latent image is increased, the resolution or quality of the image obtained by development is generally improved.

The cleaning device 50 includes a cleaning blade 52. The cleaning blade 52 is made of an elastic material such as hard urethane rubber with a thickness of 1 to 3 cm, and is substantially spread over the width of the latent image carrier 10 (in the right direction in FIG. 1 and perpendicular to the plane of the paper). The cleaning blade 52 has a corresponding length and is held by a blade holder (not shown) so as to be switchable between a pressure contact position and a pressure release position. Accordingly, a cleaning roller may be arranged in contact with the latent image carrier 10.

〔Example〕

Examples of the present invention will be specifically described below, but the present invention is not limited to these Examples.

Example 1 (Production of developer) Styrene-acrylic copolymer resin (monomer composition: 65 parts by weight of styrene, 5 parts by weight of α-methylstyrene, 0 parts by weight of methyl methacrylate, 18 parts by weight of n-butyl acrylate)
parts by weight, 2 parts by weight of divinylbenzene) 100 parts by weight,
10 parts by weight of carbon black "Mogull LJ" (manufactured by Cabot Corporation) was mixed, kneaded, crushed and classified to obtain binder resin particle powder with an average particle size of 121IH.

Next, using Nauta and Terpinyu, 0.00% of inorganic fine particle powder rR-972J (hydrophobic silica fine particles, average diameter of fine particles = 0.016μ1, manufactured by Nippon Aerosil Co., Ltd.) was added to the above-mentioned binder resin particle powder. 4% by weight, organic fine particle powder (polymethyl methacrylate fine particles, - average diameter of fine particles = 0.5
n> was mixed and stirred at a ratio of 1.8% by weight to obtain toner T1 for the present invention.

A two-component developer was prepared by mixing 3 parts by weight of this toner T1 with 97 parts by weight of a carrier made of ferrite powder rF-100J (manufactured by Nippon Tetsuko Co., Ltd.) having an average diameter of 120 microns.

(Actual photo test) Using this two-component developer, a latent image carrier made of a selenium photoreceptor, a developing device for the two-component developer equipped with a thin layer forming member similar to that shown in FIG. 1, and a cleaning device equipped with a cleaning blade. The gap between the latent image carrier and the developer transport carrier, that is, the development gap D, is
sd to 0.50am.

An alternating electric field (peak-to-peak value = 1500
V1 frequency = 2kHz) and DC bias voltage (25
0V) was applied, the temperature was 30℃, and the relative humidity was 8.
50.0 under 0% environmental conditions (10 live-action tests have shown that the developability and cleaning properties are good, and the image density is high and clear images with no fog or black spots are maintained until the end) was able to form.

Comparative Example 1 For comparison, a comparative toner t1 was produced in the same manner as in Example 1 except that organic fine particles and inorganic fine particles were not used. When a two-component developer was prepared and a photo-taking test similar to that in Example 1 was conducted using this two-component developer, it was found that after 10,000 cycles, the toner transportability became quite unstable and the image density decreased. decreased. Furthermore, the fluidity of the toner was poor, and the occurrence of capri was observed from the early stage of image formation. Also, black spots started to appear in the copied images after 2,000 times.

Example 2 (Production of developer) Styrene-acrylic copolymer resin (monomer composition: 65 parts by weight of styrene, 5 parts by weight of α-methylstyrene, 10 parts by weight of methyl methacrylate, 1 part by weight of n-butyl acrylate)
8 parts by weight, 2 parts by weight of divinylbenzene) 46 parts by weight,
Magnetite rBL-100J (manufactured by Titan Kogyo Co., Ltd.) 5
0 parts by weight were mixed, kneaded, crushed, and classified to obtain binder resin particle powder with an average particle size of 12n.

Next, using Nauta and Turbiniller, 0.8 weight of inorganic fine particle powder rR-972J (hydrophobic silica fine particles, average diameter of -order particles = 0.016p1 manufactured by Nippon Aerosil Co., Ltd.) was added to the above binder resin particle powder. %, organic fine particle powder (polymethyl methacrylate fine particles, average diameter of -order particles = 0.5
m) was mixed and stirred at a ratio of 0.4% by weight to obtain toner T2 for the present invention.

Using this toner T2 as a one-component developer, an electrophotographic copying machine "U-Bix 1200J" is equipped with a latent image carrier made of a selenium photoreceptor, a developing device for a -component developer, and a cleaning device having a cleaning blade. (manufactured by Konishiroku Photo Industry Co., Ltd.) By using a modified machine, the gap between the latent image carrier and the developer transport carrier, that is, the development gap Dsd, was set to 0.3.
0 mm, the distance Hcut between the tip of the regulating blade that regulates the thickness of the developer layer and the developer transport carrier is set to 0.24 mm, and an alternating electric field (peak-peak value = 150
Under the development conditions of applying 0V, frequency = 1kHz),
50 under the environmental conditions of temperature 30℃ and relative humidity 80%.
．． 000 live-photographing tests were conducted, and it was found that the developing property and cleaning property were good, and clear images with high image density and no fogging or black spots could be stably formed to the end.

Comparative Example 2 Comparative toner t2 was produced in the same manner as in Example 2 except that organic fine particles were not used. When we conducted a live-action test in the same way, the result was 2.00.
Black spots begin to appear in the copied images after the 0th copy, and 10.
After 000 times, the toner conveyance became considerably unstable and the image density decreased.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of an image forming apparatus that can be used in the image forming method of the present invention, and FIG. 2 is an explanatory diagram showing details of a developing device. 10...Latent image carrier 21...Charger 22.
... Exposure optical system 23 ... Developing device 25 ... Static elimination lamp 26 ... Transfer electrode 27 ... Separation electrode 28 ... Static elimination electrode 29 ... Fixing device
30... Original table 40... Original table
50...Returning device 52...Cleaning blade 61...Developing sleeve 62...Magnetic roll 6
4... Thin layer forming member 65. 66... Stirring member 67... Toner supply container 68... Toner supply roller 69... Developer reservoir 70... Bias power supply 71... Development area 1 cause difference 2 diagram

Claims (1)

[Scope of Claims] 1) A thin developer layer formed on the developer transport carrier and having a thickness smaller than the gap between the latent image carrier and the developer transport carrier in the development area, It includes a developing step of developing an electrostatic latent image on a latent image carrier while applying an oscillating electric field, and the toner constituting the developer is composed of binder resin particles, inorganic fine particles, and the binder resin particles. An image forming method characterized in that the image forming method comprises small-diameter organic fine particles. 2) The toner for electrostatic image development according to claim 1, wherein the inorganic fine particles are made of silica or surface-treated silica. 3) The toner for electrostatic image development according to claim 1, wherein the toner contains two or more types of inorganic fine particles. 4) The toner for electrostatic image development according to claim 3, wherein one of the inorganic fine particles is made of silica or surface-treated silica. 5) The image forming method according to any one of claims 1 to 4, wherein the organic fine particles are made of a vinyl polymer. 6) The image forming method according to claim 5, wherein the vinyl polymer is an acrylic polymer. 7) The image forming method according to claim 6, wherein the acrylic polymer is polymethyl methacrylate.