JPH07319174A - Electrostatic latent image holding body, image forming method and device therefor - Google Patents

Abstract

PURPOSE:To provide a high-performance and compact electrostatic latent image holding body capable of obtaining high image, quality by an inexpensive developing method, and to provide an image forming method and a device using the holding body. CONSTITUTION:The electrostatic latent image holding body 1 whose capacitance per unit area is within a range from 90pF/cm<2> to 200pF/cm<2> is used as the electrostatic latent image holding body 1 used in the image forming method at least provided with the movable electrostatic latent image holding body 1 including a fixed magnet, a toner reservoir 6 having an opening part opposed to the surface of the holding body 1 and supplying magnetic toner so that it may be carried on the surface of the holding body 1, and an electrode roller 9 set at a position being a specified distance from the surface of the holding body 1 and having a magnet inside; and provided with a developing stage constituted so that a toner layer carried on the holding body 1 is brought into contact with the roller 9 and unnecessary toner at a part other than the image part of an electrostatic latent image formed on the holding body 1 is removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic latent image carrier used in an electrophotographic apparatus such as a copying machine, a printer and a facsimile, an image forming method and an image forming apparatus, and more particularly to a laminate containing an organic photoconductive substance. The present invention relates to an electrostatic latent image carrier that is a photoelectrophotographic photoreceptor, an improved image forming method, and an image forming apparatus.

[0002]

2. Description of the Related Art In recent years, electrophotographic apparatuses have been remarkably developed due to their high speed, low noise, high image quality and ability to record on plain paper, and they are rapidly becoming popular not only in copying machines but also in printers and facsimiles. Further, especially in the fields of printers and facsimiles, there is a shift from office use to personal use, and there is a demand for a technology that realizes further downsizing, cost reduction, maintenance-free, and the like.

Generally, the electrophotographic image forming method is
First, an electrophotographic photosensitive member, which is an electrostatic latent image holding member, is uniformly charged, and then an image signal is written on the photosensitive member by an exposure unit to form an electrostatic latent image. Further, the electrostatic latent image formed on the photoconductor is visualized by toner, which is colored powder, in the developing process, and the toner is transferred and fixed on a copy sheet to obtain a copy image. On the other hand, the residual toner after transfer is removed from the photoconductor in a cleaning step, and then the charge is removed as necessary, and the photoconductor is repeatedly used in the image forming process. That is, at least the charging, exposure, development, transfer, and cleaning steps constitute an electrophotographic process, and the electrostatic characteristics of the electrophotographic photosensitive member as the electrostatic latent image carrier used in the process are important and It is necessary that the photographic photoreceptor be a photoreceptor suitable for the electrophotographic process and electrophotographic apparatus used.

As an electrophotographic photosensitive member, an organic photosensitive member containing an organic photoconductive substance has been developed and put into practical use in recent years because of its advantages such as easy film formation, inexpensiveness and no pollution. In particular, the development of an organic photoconductor having a high sensitivity in a long wavelength region, which is suitable for an optical printer such as a laser beam printer using a semiconductor laser as an exposure light source and a facsimile, is remarkable. Most of the practically used organic photoconductors are laminated organic photoconductors in which a charge generation layer containing a charge generation substance and a charge transport layer containing a charge transport substance are laminated, and a functional separation structure is provided. Has significantly improved the characteristics.

In the electrophotographic image forming method, a cascade developing method, a touch-down developing method, a jumping developing method and the like are known as developing methods for visualizing an electrostatic latent image. For example, in U.S. Pat. No. 3,105,770, cascade development is disclosed as a developing method used for the first practical copying machine as a developing method in which a developer is directly sprinkled on a photoreceptor. Further, U.S. Pat. No. 3,866,574 discloses a method of applying an AC bias to a developing roller to fly a single-component toner and develop the toner. In this developing method, the AC bias applied to the developing roller is used for the purpose of activating the movement of the toner, and the toner is described as flying to the image portion and returning to the middle in the non-image portion.

In Japanese Patent Publication No. 63-42256,
Jumping development is disclosed as an improvement of the technique of applying the AC bias. In this jumping developing method, toner is carried on a toner carrier, and a rigid or elastic regulating blade is installed on the toner carrier with a minute gap from the carrier. Then, the regulation blade regulates the toner in a thin layer, conveys the toner to a developing portion, and the toner is attached to the image portion of the photoconductor by an AC bias there. The technical idea of Japanese Patent Publication No. 63-42256 differs from the above-mentioned US Pat. No. 3,866,574 in that the toner reciprocates in the image portion and the non-image portion.

However, in the developing method having these constitutions,
Each of them had its drawbacks. In the cascade development method, the reproducibility of a solid image is poor and the apparatus becomes large and complicated. The developing method described in U.S. Pat. No. 3,866,574 has the drawback that the apparatus requires high precision, is complicated, and is expensive. Further, in the jumping development method, it is essential to form a very uniform thin layer on the toner carrier carrying the toner layer, and the developing property is influenced by the thickness of the toner layer. It has a drawback that so-called sleeve ghost development occurs, in which a history of the previous image remains in the thin layer and an afterimage appears in the image. Further, it has a drawback that the device is complicated and the cost is high.

Therefore, we have proposed, as a developing method, an electrophotographic method and apparatus which can realize miniaturization, cost reduction and high performance. (For example, Japanese Patent Application No. 3-345990) FIG. 1 shows a schematic view of an example of the apparatus. In FIG.
Reference numeral 1 is a photosensitive drum which is an electrostatic latent image holding member, and 2 is a photosensitive member 1.
A non-rotating magnet fixed coaxially with 3 is a corona charger for charging the photoconductor, 4 is a grid electrode for controlling the charging potential of the photoconductor, and 5 is signal light. Reference numeral 6 is a toner reservoir, 7 is a magnetic toner, 8 is a damper for smoothing the flow of toner in the toner reservoir, and a damper for preventing the toner from being crushed by its own weight and clogged between the photoconductor and the electrode roller, 9 Is a non-rotating magnet 10 coaxially fixed inside
An electrode roller having 11; an AC high-voltage power supply for applying a voltage to the electrode roller; a scraper 12 for scraping off the toner on the electrode roller;
It is a transfer corona charger that transfers to.

The operation of this developing method will be described below with reference to FIG. The photoconductor 1 is -50 with the corona charger 3.
The photoreceptor 1 was charged to 0 V and the laser beam 5 was irradiated to form an electrostatic latent image according to an image signal. The magnetic toner 7 was adhered and carried by the magnetic force of the fixed magnet 2 in the toner reservoir 6 on the surface of the photoconductor 1. Next, the photoconductor 1 and the electrode roller 9 were rotated in the direction of the arrow to pass the photoconductor 1 in front of the electrode roller 9. At this time, a DC voltage of -350V was superposed on the electrode roller 9 by the AC high voltage power source 11 at 750.
An AC voltage of V0-p (frequency 1 kHz) was applied. As a result, the toner was collected from the photoconductor 1 toward the electrode roller 9, and a negative-positive inverted toner image remained only on the image portion on the photoconductor 1. Electrode roller 9 rotating in the direction of the arrow
The toner adhered to was scraped off by the scraper 12, returned to the toner reservoir 6 and used for the next image formation.
The toner image thus obtained on the photoreceptor 1 is transferred to the image receiving paper 14
After being transferred by the transfer corona charger 13, the image was fixed and a printed image was obtained.

As described above, in the developing method in this image forming method, the photoconductor containing the fixed magnet, the toner reservoir facing the surface of the photoconductor, and the inside of the photoconductor which faces the photoconductor with a predetermined gap. An electrode roller having a magnet is provided, magnetic toner is supplied from a toner reservoir to a photoconductor by a magnetic force of the fixed magnet to carry the toner, and thereafter an unnecessary toner in a non-image portion is collected by the electrode roller to form a toner image. . Therefore, this developing method faithfully reproduces a solid image, does not cause a sleeve ghost, and enables downsizing, simplification, and cost reduction of the apparatus.

[0011]

When such a developing system is used, the magnetic flux densities of the fixed magnet inside the photosensitive member and the fixed magnet inside the electrode roller, the magnetic pole angles of the two fixed magnets facing each other, the photosensitive member and the electrode. The image quality depends on the configuration of the developing device such as the gap with the roller, the developing conditions such as the charging potential of the photoconductor and the applied voltage of the electrode roller, and the fluidity of the magnetic toner to be used, the amount of charged electric charge, the particle size and the like. Although it is optimized, the electrostatic capacity of the photoconductor, which is an electrostatic latent image holder, also affects the image quality such as a decrease in solid image density and an increase in so-called background fog that is toner adhesion in non-image areas. The problem of affecting has arisen.

In view of the above problems, the present invention provides an electrostatic latent image holding member having a specific electrostatic capacity in order to realize high image density and high image quality with low background fog in the above-mentioned image forming method. It is in. Further, by using the electrostatic latent image holding member having the specific capacitance, the image quality is higher, the device is downsized,
An object of the present invention is to provide an image forming method and an image forming apparatus which can be simplified and reduced in cost.

[0013]

In order to solve the above-mentioned problems, an electrostatic latent image holding member of the present invention includes at least an electrostatic latent image holding member which moves by containing a fixed magnet, and the electrostatic latent image holding member. A toner reservoir having an opening facing the surface of the image holding member and supplying and carrying magnetic toner on the surface of the electrostatic latent image holding member, and a predetermined gap with the surface of the electrostatic latent image holding member. A toner layer carried on the electrostatic latent image holding member is brought into contact with the electrode roller, and is formed on the electrostatic latent image holding member. An electrostatic latent image carrier used in an image forming method having a developing step configured to remove unnecessary toner other than the image portion of the electrostatic latent image formed by static electricity per unit area of the electrostatic latent image carrier. Characterized by having a capacitance in the range of 90 pF / cm ² to 200 pF / cm ² . It is an electrostatic latent image holder.

Further, the image forming method of the present invention has at least an electrostatic latent image holding member which contains a fixed magnet and moves, and an opening facing the surface of the electrostatic latent image holding member. A toner reservoir for supplying and carrying magnetic toner on the surface of the latent image holding member, and an electrode roller having a magnet inside which is installed at a position having a predetermined gap from the surface of the electrostatic latent image holding member are provided. Then, the toner layer carried on the electrostatic latent image holder is brought into contact with the electrode roller to remove unnecessary toner other than the image portion of the electrostatic latent image formed on the electrostatic latent image holder. An image forming method including the developing step according to claim 1, wherein an electrostatic capacity per unit area of the electrostatic latent image holding member is 90 pF.
/ Cm ² to 200 pF / cm ² is an image forming method characterized by using an electrostatic latent image carrier.

Further, the image forming apparatus of the present invention has at least an electrostatic latent image holding member which contains a fixed magnet and moves, and an opening facing the surface of the electrostatic latent image holding member. A toner reservoir for supplying and carrying magnetic toner on the surface of the latent image holding member, and an electrode roller having a magnet inside which is installed at a position having a predetermined gap from the surface of the electrostatic latent image holding member are provided. Then, the toner layer carried on the electrostatic latent image holder is brought into contact with the electrode roller to remove unnecessary toner other than the image portion of the electrostatic latent image formed on the electrostatic latent image holder. And an electrostatic latent image holding member having a capacitance of 90 pF per unit area.
An image forming apparatus characterized by being an electrostatic latent image holding member in the range of / cm ² to 200 pF / cm ² .

[0016]

In the image forming method of the present invention, the electrostatic latent image holding member containing the fixed magnet is used, and the magnetic toner is sprinkled from the opposing toner reservoir to the electrostatic latent image holding member on which the electrostatic latent image is formed. The electrostatic latent image holding member is magnetically attached by the fixed magnet, carried and conveyed to a gap space between the electrostatic latent image holding member and the electrode roller, and AC bias is applied to the electrode roller to reciprocate the toner. The toner in the upper non-image portion is removed by electrostatic force and magnetic force. That is, it is the electrostatic latent image holder that carries and conveys toner from the toner reservoir to the electrode roller portion, and the electrode roller has a bare surface that does not carry the toner layer facing the electrostatic latent image holder. Here, the electrode roller serves to circulate the toner in the toner reservoir and at the same time to collect the toner in the non-image portion on the electrostatic latent image holding member.

In such an image forming method, the magnetic toner is sprinkled on the electrostatic latent image holding member on which the electrostatic latent image is formed, magnetically adhered by the fixed magnet, and then the toner is carried to the electrode roller portion. It is considered that the above development is completed, and the electrode roller only collects the unnecessary toner in the non-image portion. Therefore, the condition of the voltage applied to the electrode roller affects the toner collecting ability, and the adhesive force of the magnetic toner on the electrostatic latent image holding member, which is in the actual developing state, does not affect the image portion of the electrostatic latent image holding member. It varies depending on the amount of charge with the non-image part, that is, the electrostatic capacity of the electrostatic latent image holder, and therefore the amount of toner carried to the electrode roller part or the adhesion force of the toner differs, resulting in a decrease in solid image density. And the image quality is deteriorated, such as increased fog in the non-image area. If the amount of toner to be carried and conveyed or the adhesive force of toner is larger than the toner collecting ability of the electrode roller, the background fog increases, and conversely, if the amount of toner carried and conveyed or the adhesive force of toner is small, the solid image density becomes large. It is expected to decrease.

Therefore, the electrostatic latent image carrier of the present invention has a capacitance per unit area of 90 pF / cm ² to 200 pF.
By setting the range of / cm ² , it is possible to optimize the amount of toner carried on the electrostatic latent image holding member or the adhesive force of the toner, and as a result, it is possible to obtain a high level under various developing conditions of the image forming method described above. The image density and the low ground fog can be compatible with each other.

Further, in the image forming method and the image forming apparatus of the present invention, the electrostatic capacity per unit area is 90 pF / cm ^2.
To 200 pF / cm ² by using the electrostatic latent image carrier, high image density and high image quality with low background fog can be realized, and further downsizing, simplification and cost reduction of the device can be realized. Is.

[0020]

EXAMPLES The electrostatic latent image carrier, the image forming method and the image forming apparatus of the present invention will be described in detail below.

The electrostatic latent image carrier of the present invention has a capacitance per unit area of 90 pF / cm ² to 200 pF / cm ^2.
Any known electrophotographic photosensitive member may be used as long as it is within the range of 1. However, since the electrophotographic characteristics are good and stable, in particular, at least the charge generating substance is contained on the cylindrical conductive support. It is desirable to use a multi-layer electrophotographic photoreceptor in which a charge generation layer for forming a charge transport layer and a charge transport layer containing a charge transport material are sequentially stacked. Further, at least the organic photoconductive substance is used because it has low cost, is easy to form a film, is non-polluting, and has high sensitivity in the semiconductor laser light region of the exposure light source in the case of a laser beam printer or a laser facsimile. Organic photoreceptors containing it are desirable.

As the charge generating substance used in the charge generating layer of the electrostatic latent image carrier of the present invention, organic pigments such as phthalocyanine type, azo type, squarylium type, perylene type and cyanine type can be used. In particular, many phthalocyanine-based pigments have sensitivity up to long wavelengths in the near infrared region, and as described above, are suitable for laser beam printers and laser facsimiles using semiconductor lasers,
Metal-free phthalocyanine and various metal phthalocyanines, specifically α-type copper phthalocyanine, β-type copper phthalocyanine, ε-type copper phthalocyanine, τ-type metal phthalocyanine, X-type metal-free phthalocyanine, α-type titanyl phthalocyanine, β-type titanyl phthalocyanine, etc. Phthalocyanine pigments containing metal-free or metal compounds having various crystal forms of The charge generation layer is formed to have a film thickness of several μm by applying a coating solution prepared by adding and dispersing these charge generating substances and a suitable binder resin in a solvent by a usual coating method and drying the coating solution. However, in view of electrophotographic characteristics such as sensitivity and repeatability, the film thickness after drying is preferably 1 μm or less, preferably 0.5 μm or less.

Examples of the charge transport material used in the charge transport layer of the electrostatic latent image carrier of the present invention include compounds having an electron donating group such as an alkyl group, an alkoxy group, an amino group and an imide group, anthracene, pyrene and phenanthrene. And polycyclic aromatic compounds such as and derivatives containing them, heterocyclic compounds such as oxazole, carbazole, pyrazoline and indole, and derivatives containing them, hydrazone compounds, stilbene compounds and the like. The charge-transporting layer is formed by dissolving at least these charge-transporting substance and binder resin in a suitable solvent, applying the solution by a usual coating method, and drying. The thickness of the charge transport layer after drying is several μm
It is several tens of μm, but preferably 5 to 25 μm.

The binder resin used in the charge generation layer and the charge transport layer is used for the purpose of improving the adhesiveness with other layers, improving the uniformity of the coating film, adjusting the fluidity during coating, and the like. , Polyvinyl chloride resin, polyvinyl butyral resin, polyvinyl acetate resin, polycarbonate resin, polyarylate resin, polyester resin, acrylic resin,
Known thermoplastic resins such as silicone resins or thermosetting resins can be used. The solvent may be any solvent that can dissolve the charge transporting substance or the binder resin, but is usually ketones such as methyl ethyl ketone, ethers such as tetrahydrofuran, halogenated hydrocarbons such as methylene chloride and carbon tetrachloride, and benzene. , And aromatic hydrocarbons such as toluene can be used.

The conductive support used in the electrostatic latent image carrier of the present invention may be any conventionally known conductive material, such as a metal plate made of aluminum or aluminum alloy, or a metal drum. A plate or a drum made of a metal oxide such as tin oxide or indium oxide, or various plastic films or drums to which the metal and the metal oxide are attached by vapor deposition, sputtering, laminating, coating, etc., and are electrically conductive. .

Further, in the electrostatic latent image carrier of the present invention, an adhesive layer, a barrier layer or a conductive layer can be provided between the conductive support and the photosensitive layer as in the case of a usual electrophotographic photosensitive member.

The electrostatic capacity per unit area of the electrostatic latent image holding member of the present invention is a LCR meter or the like for a sample in which an electrode having a constant area is formed on the surface of a cut piece of the electrostatic latent image holding member by a vapor deposition method or the like. Is a value obtained by measuring the electrostatic capacity by the usual measuring method of and dividing by the electrode area. FIG. 2 shows a schematic diagram of the measurement sample. When the area of the electrode is S and the capacitance of the sample is C, the capacitance per unit area is C / S.
Can be calculated at.

The electrostatic latent image carrier of the present invention has an electrostatic capacity of 90 pF / unit area measured as described above.
cm ² to 200 pF / cm ² , preferably 100
pF / cm in the range of ² to 180 pF / cm ^2, the capacitance per unit area is 200 pF / cm ² or more can not be obtained a sufficient solid image density, also capacitance per unit area is 90pF If it is less than / cm ² , the background fog will increase. The relationship between the capacitance per unit area and the image is considered as follows. In the image forming method of the present invention, as described above, the toner magnetically attached to and carried on the electrostatic latent image holding member by the fixed magnet has a magnetic force, a mirror image force with the electrostatic latent image holding member, Since the adhesion force is determined by the electrostatic repulsion force in the charging polarity, the amount of toner conveyed or the adhesion force of the toner varies depending on the electrostatic capacity per unit area of the electrostatic latent image carrier, Of 200 pF / cm ² or more, the surface charge amount of the image portion of the electrostatic latent image formed on the electrostatic latent image holding member becomes large, and the toner of the same charging polarity and the electrostatic latent image holding member are It is considered that since the electrostatic repulsion force of (1) becomes too large, the amount of toner adhering to the electrostatic latent image holding member and conveyed or the adhering force of toner decreases, resulting in a decrease in solid image density. On the other hand, when the electrostatic capacity per unit area is 90 pF / cm ² or less, the amount of toner adhering to the electrostatic latent image holding member or the toner adhering force becomes excessive, and the toner collecting ability of the electrode roller is It is considered that the ground cover will increase as the amount of water increases. In any case, the amount of toner carried or conveyed to the electrode roller portion or the adhesive force of the toner is different, and if the amount of toner carried and carried is larger than the toner collection ability of the electrode roller, the background fog increases, and conversely. It is considered that when the amount of toner carried and conveyed is small, the solid image density decreases.

The image forming method and the image forming apparatus of the present invention form an electrostatic latent image by using the electrostatic latent image holder containing a fixed magnet proposed in the above-mentioned Japanese Patent Application No. 3-345990. The toner is sprinkled and magnetically adhered to the electrostatic latent image holder, carried and conveyed to the electrode roller portion, an AC bias is applied to the electrode roller, and the non-image portion toner of the electrostatic latent image holder is electrostatically and magnetically applied. It can be applied to a developing process and a developing device configured to be removed by.

The magnetic toner used in the image forming method and the image forming apparatus of the present invention includes at least a binder resin and a magnetic material, and if necessary, a colorant, a charge control agent, a release agent,
It is composed of a fluidizing agent and a second external additive. As the binder resin, a styrene acrylic resin, a polyester resin, or the like can be used, and if necessary, another known polymer or copolymer can be used. Examples of the magnetic substance to be blended include metal powder such as iron, manganese, nickel and cobalt, and ferrite such as iron, manganese, nickel, cobalt and zinc. 20-60 added amount
Weight percent is preferred. When the addition amount is 20% by weight or less, the toner scattering tends to increase, and when the addition amount is 60% by weight or more, the toner charge amount tends to decrease and the image quality tends to deteriorate.

Further, in the magnetic toner used in the present invention, carbon black, iron black, graphite, nigrosine, a metal complex of azo dye, phthalocyanine blue, cerco oil blue, and DuPont oil are used for the purpose of coloring and controlling charge as required. Appropriate pigments or dyes such as red, aniline blue, benzidine yellow, rose bengal and mixtures thereof may be blended. Further, if necessary, a release agent such as polyethylene or polypropylene, and an external additive of inorganic fine powder such as hydrophobic silica, titania, alumina or zirconia may be contained. In addition, if necessary, fine powder of organic material or other types of organic materials for the purpose of polishing agents such as tin oxide, strontium titanate, barium titanate, and tungsten carbide, fluidity assistants, charging assistants, cleaning assistants, etc. Additives can be mixed.

The image forming apparatus of the present invention is an apparatus having a developing means formed by an image forming method using an electrostatic latent image holding member having a specific electrostatic capacity per unit area as described above, which is a copying machine. Machine, optical printer such as laser beam printer, laser facsimile, etc.

The electrostatic latent image carrier, the image forming method and the image forming apparatus of the present invention will be described below with reference to the drawings, but the present invention is not limited thereto.

Example 1 Two parts by weight of 2 parts by weight of τ type metal-free phthalocyanine (manufactured by Toyo Ink Mfg. Co., Ltd.) and 2 parts by weight of polyvinyl butyral resin (trade name Slex BL-1 manufactured by Sekisui Chemical Co., Ltd.) were used. In addition to 96 parts by weight of butanol, the mixture was dispersed for 4 hours by a ball mill, the dispersion was dip-coated on an aluminum drum having an outer diameter of 30 mm, and air-dried to form a charge generation layer having a thickness of about 0.2 μm.

Next, 1,1-bis (p-diethylaminophenyl) -4,4-diphenyl-1,3 butadiene 1
Parts by weight and 1 part by weight of polycarbonate resin (trade name Iupilon Z-300 manufactured by Mitsubishi Gas Chemical Industry Co., Ltd.) in 9 parts by weight of methylene chloride are dip-coated on the charge generation layer at 110 ° C. Film thickness of about 20μm after drying for 2 hours
The charge-transporting layer was formed to obtain a laminated electrophotographic photosensitive member.

A part of the electrophotographic photosensitive member produced in this manner was cut out, and the capacitance of a sample on which a 2 cm ² aluminum electrode was vapor-deposited was measured at a frequency of 1 kHz using an LCR meter, and the unit was measured. The capacitance per area was calculated. The electrostatic capacity per unit area at this time was 142 pF / cm ² .

FIG. 1 shows an embodiment of the image forming method and the image forming apparatus of the present invention. In FIG. 1, 1
Reference numeral 2 is a photoconductor as an electrostatic latent image holding member, 2 is a non-rotating magnet fixed coaxially with the photoconductor 1, 3 is a corona charger for negatively charging the photoconductor, and 4 is a charge potential of the photoconductor. Grid electrode 5 is signal light, 6 is a toner reservoir for supplying magnetic toner 7 to the surface of photoreceptor 1, and 7 is a negatively chargeable magnetic one-component toner using styrene-acrylic resin as a binder resin and having an average particle size of about 7 μm. is there. The composition of the magnetic one-component toner used is 70 parts by weight of styrene-acrylic resin,
0.4 parts by weight of colloidal silica having 25 parts by weight of ferrite, 3 parts by weight of carbon black and 2 parts by weight of metal complex of oxycarboxylic acid and having a particle size of 0.02 μm was externally added and used. Further, 9 is a non-magnetic electrode roller set with a gap from the photoconductor 1, 10 is a non-rotating magnet installed inside the electrode roller 9, 11 is an AC high voltage power supply for applying voltage to the electrode roller 9, and 12 is This is a scraper made of a polyester film that scrapes off the toner on the electrode roller, and has a configuration in which the electrode roller 9 collects excess toner in the non-image portion. Reference numeral 8 is a damper for smoothing the flow of toner in the toner reservoir and for preventing the toner from being crushed by its own weight and clogged between the photoconductor 1 and the electrode roller 9. The magnetic flux density on the surface of the photoreceptor 1 by the magnet 2 was set to 600 Gs, and the magnetic pole angle of both the magnet 2 and the magnet 10 was set to 15 degrees. Further, the photoconductor 1 is rotated at a peripheral speed of 65 mm / s in the direction of the arrow in the drawing, the electrode roller 9 has a diameter of 16 mm, and at a peripheral speed of 40 mm / s, the direction opposite to the direction of travel of the photoconductor (the arrow in the drawing). Direction) and used. The gap between the photoconductor 1 and the electrode roller 8 is 300 μm
Set to.

The operation of the image forming apparatus configured as described above will be described below. The photoconductor 1 is connected to the corona charger 3 (applied voltage -5.3 kV, grid 4 voltage -50
0 V) and charged to -500V. The photoconductor 1 was irradiated with laser light 5 to form an electrostatic latent image. At this time, the post-exposure potential of the photoconductor 1 was −70V. The magnetic one-component toner 7 was attached to the surface of the photoconductor 1 from the inside of the toner reservoir 6 by the magnetic force of the fixed magnet 2. At this time, the toner is about -3μ
It was charged to C / g. Next, the photoconductor 1 having the toner layer attached thereto was passed in front of the electrode roller 9 rotating in the direction of the arrow in the figure. At this time, the AC high voltage power source 1 is applied to the electrode roller 9.
800V 0-with DC voltage of -300V superimposed by
An alternating voltage (frequency 2 kHz) of p (peak-to-peak 1.6 kV) was applied. The toner layer on the photoconductor 1 moves between the photoconductor 1 and the electrode roller 9, and the toner adhering to the non-image portion gradually moves to the electrode roller 9 and is collected.
On the photoconductor 1, a negative-positive inverted toner image remained only in the image portion. The toner collected by the electrode roller 9 rotating in the direction of the arrow was scraped off by the scraper 12 and returned to the toner reservoir 6 again for the next image formation. The movement of the toner in the toner reservoir 6 is shown by the broken line in the figure. The toner image thus obtained on the photoconductor 1 was transferred onto the image receiving paper 14 by the transfer charger 13, and then thermally fixed by a fixing device (not shown) to obtain a print image.

As the electrostatic latent image carrier of the image forming method shown in FIG. 1, the copying test was conducted using the laminated electrophotographic photosensitive member of the above-mentioned Example 1. The image density was measured by a reflection densitometer (Macbeth) and evaluated. As a result, a solid black image was obtained and a high-density image having a density of 1.4 or more was obtained, and no background fog occurred in the non-image area.

Example 2 A photoconductor was prepared in the same manner as in Example 1 except that the thickness of the charge transport layer in the laminated electrophotographic photoconductor of Example 1 was changed to 30 μm. When the electrostatic capacity per unit area of this photosensitive member was measured in the same manner as in Example 1, it was 93 pF / cm ² .

This electrophotographic photosensitive member was prepared in the same manner as in Example 1.
A copying test was conducted using the electrostatic latent image carrier of the image forming method shown in FIG. At this time, the photoconductor was charged to -500 V, and other conditions were set in the same manner as in Example 1. As a result, a solid black image was obtained and a high-density image having a density of 1.4 or more was obtained. Further, the background fog in the non-image area did not occur.

Example 3 A photoconductor was prepared in the same manner as in Example 1 except that the thickness of the charge transport layer in the laminated electrophotographic photoconductor of Example 1 was changed to 15 μm. When the electrostatic capacity per unit area of this photosensitive member was measured in the same manner as in Example 1, it was 190 pF / cm ² .

This electrophotographic photosensitive member was prepared in the same manner as in Example 1.
A copying test was conducted using the electrostatic latent image carrier of the image forming method shown in FIG. At this time, the photoconductor was charged to -500 V, and other conditions were set in the same manner as in Example 1. As a result, a solid black image was obtained and a high-density image having a density of 1.4 or more was obtained. Further, the background fog in the non-image area did not occur.

Example 4 A photoconductor was prepared in the same manner as in Example 1 except that the thickness of the charge transport layer in the laminated electrophotographic photoconductor of Example 1 was changed to 25 μm. When the electrostatic capacity per unit area of this photosensitive member was measured in the same manner as in Example 1, it was 110 pF / cm ² .

This electrophotographic photosensitive member was prepared in the same manner as in Example 1.
A copying test was conducted using the electrostatic latent image carrier of the image forming method shown in FIG. At this time, the photoconductor was charged to -500 V, and other conditions were set in the same manner as in Example 1. As a result, a solid black image was obtained and a high-density image having a density of 1.4 or more was obtained. Further, the background fog in the non-image area did not occur.

Comparative Example 1 A photoconductor was prepared in the same manner as in Example 1 except that the thickness of the charge transport layer in the laminated electrophotographic photoconductor of Example 1 was changed to 32 μm. When the electrostatic capacity per unit area of this photoreceptor was measured in the same manner as in Example 1, it was 87 pF / cm ² .

This electrophotographic photosensitive member was prepared in the same manner as in Example 1.
A copying test was conducted using the electrostatic latent image carrier of the image forming method shown in FIG. At this time, the photoconductor was charged to -500 V, and other conditions were set in the same manner as in Example 1. As a result, a solid black image was obtained and a high-density image with a density of 1.4 or more was obtained, but background fog occurred in the non-image area.

Comparative Example 2 A photoconductor was prepared in the same manner as in Example 1 except that the thickness of the charge transport layer in the laminated electrophotographic photoconductor of Example 1 was changed to 13 μm. When the electrostatic capacity per unit area of this photosensitive member was measured in the same manner as in Example 1, it was 218 pF / cm ² .

This electrophotographic photosensitive member was prepared in the same manner as in Example 1.
A copying test was conducted using the electrostatic latent image carrier of the image forming method shown in FIG. At this time, the photoconductor was charged to -500 V, and other conditions were set in the same manner as in Example 1. As a result, it was a low density image in which the density of the solid black image was only 1.2.

[0050]

As described above, the present invention has at least the electrostatic latent image holding member that moves by containing a fixed magnet, and the opening facing the surface of the electrostatic latent image holding member. A toner reservoir for supplying and carrying magnetic toner on the surface of the electrostatic latent image carrier, and an electrode roller having a magnet inside, which is installed at a position having a predetermined gap from the surface of the electrostatic latent image carrier. The toner layer carried by the electrostatic latent image carrier is brought into contact with the electrode roller to remove unnecessary toner other than the image portion of the electrostatic latent image formed on the electrostatic latent image carrier. As an electrostatic latent image carrier used in an image forming method having a developing step, the electrostatic capacity per unit area is 90 pF / cm.
^{By using} the electrostatic latent image holding member in the range of ² to 200 pF / cm ² , high density, low background fogging and high image quality can be realized in an image forming method and image forming apparatus having high performance, small size, and low cost.

[Brief description of drawings]

FIG. 1 is a sectional view showing a main part of an electrophotographic apparatus in which an image forming method according to an embodiment of the present invention is used.

FIG. 2 is a schematic diagram of a capacitance measurement sample.

[Explanation of symbols]

 1 Photoconductor drum 2 Fixed magnet contained in photoconductor 3 Corona charger 4 Grid electrode 5 Signal light 6 Toner reservoir 7 Magnetic toner 9 Electrode roller 10 Magnet installed inside electrode roller 11 AC high voltage power supply 12 Scraper 13 Transfer charging Vessel 14 image receiving paper

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masatoshi Maeda 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Tsumugi Kobayashi, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (15)

[Claims] 1. An electrostatic latent image holding member which contains at least a fixed magnet and moves, and an opening facing the surface of the electrostatic latent image holding member. The electrostatic latent image has a toner reservoir for supplying and carrying magnetic toner, and an electrode roller having a magnet inside, which is installed at a position having a predetermined gap from the surface of the electrostatic latent image holding member. Image formation including a developing step in which a toner layer carried on a holding body is brought into contact with the electrode roller to remove unnecessary toner other than the image portion of the electrostatic latent image formed on the electrostatic latent image holding body An electrostatic latent image carrier used in the method, wherein the electrostatic latent image carrier has a capacitance per unit area of 90.
electrostatic latent image holding member, characterized in that from pF / cm ² in the range of 200 pF / cm ^2. 2. A laminated body in which the electrostatic latent image carrier has a charge generating layer containing a charge generating substance and a charge transporting layer containing a charge transporting substance sequentially formed on at least a cylindrical conductive support. 2. The electrostatic latent image carrier according to claim 1, which is a photoelectrophotographic photoreceptor. 3. The electrostatic latent image holding member according to claim 1, wherein the electrostatic latent image holding member contains at least an organic photoconductive substance. 4. The electrostatic latent image carrier according to claim 2, wherein the charge generation layer of the electrostatic latent image carrier contains at least a phthalocyanine pigment. 5. The electrostatic latent image carrier according to claim 2, wherein the charge transport layer of the electrostatic latent image carrier is an organic resin layer containing at least a charge transport substance and a binder resin. . 6. An electrostatic latent image holding member which contains at least a fixed magnet and moves, and an opening facing the surface of the electrostatic latent image holding member. The electrostatic latent image has a toner reservoir for supplying and carrying magnetic toner, and an electrode roller having a magnet inside, which is installed at a position having a predetermined gap from the surface of the electrostatic latent image holding member. Image formation including a developing step in which a toner layer carried on a holding body is brought into contact with the electrode roller to remove unnecessary toner other than the image portion of the electrostatic latent image formed on the electrostatic latent image holding body And a capacitance per unit area of the electrostatic latent image carrier is 90.
image forming method which comprises using an electrostatic latent image holding member from pF / cm ² in the range of 200 pF / cm ^2. 7. A laminate in which the electrostatic latent image carrier has a charge generating layer containing a charge generating substance and a charge transporting layer containing a charge transporting substance sequentially formed on at least a cylindrical conductive support. 7. The image forming method according to claim 6, wherein an electrostatic latent image holding member which is a electrophotographic photosensitive member is used. 8. The image forming method according to claim 6, wherein the electrostatic latent image holder is an electrostatic latent image holder containing at least an organic photoconductive substance. 9. The image forming method according to claim 7, wherein the charge generation layer of the electrostatic latent image carrier is an electrostatic latent image carrier containing at least a phthalocyanine pigment. 10. The electrostatic latent image holding member, wherein the charge transporting layer of the electrostatic latent image holding member is an organic resin layer containing at least a charge transporting substance and a binder resin. The image forming method described. 11. An electrostatic latent image holding member that contains at least a fixed magnet and moves, and an opening facing the surface of the electrostatic latent image holding member. The electrostatic latent image has a toner reservoir for supplying and carrying magnetic toner, and an electrode roller having a magnet inside, which is installed at a position having a predetermined gap from the surface of the electrostatic latent image holding member. The toner layer carried on the holder is brought into contact with the electrode roller,
An image forming apparatus having a developing unit configured to remove unnecessary toner other than an image portion of an electrostatic latent image formed on the electrostatic latent image holding body, wherein Has a capacitance of 90
image forming apparatus, characterized in that the pF / cm ² an electrostatic latent image holding member in the range of 200 pF / cm ^2. 12. A laminate in which the electrostatic latent image carrier has a charge generating layer containing a charge generating substance and a charge transporting layer containing a charge transporting substance, which are sequentially formed on at least a cylindrical conductive support. The image forming apparatus according to claim 11, wherein the image forming apparatus is a type electrophotographic photosensitive member. 13. The image forming apparatus according to claim 11, wherein the electrostatic latent image carrier is an electrostatic latent image carrier containing at least an organic photoconductive substance. 14. The image forming apparatus according to claim 12, wherein the charge generation layer of the electrostatic latent image carrier is an electrostatic latent image carrier containing at least a phthalocyanine pigment. 15. The electrostatic latent image carrier, wherein the charge transport layer of the electrostatic latent image carrier is an organic resin layer containing at least a charge transport substance and a binder resin. The image forming apparatus described.