JPH1165263A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of accomplishing good gradation in a wide region from a graphic image region to a solid image region, and making the density compatible with the high resolution. SOLUTION: Photoconductive grains are used as toner used in a developing means. The supporting substrate 22 of a developer carrier is made light- transmissive, besides, a light source is installed inside the substrate 22. An image carrier 1 is constituted of a substrate 19, a charge generating layer 20 and a charge transport layer 21. The laminated toner quantity on the image carrier 1 is controlled by controlling the conductivity of the toner 25 by an irradiation light 23 emitted from the light source in accordance with an image pattern E formed on the charge transport layer 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine or a printer.

[0002]

2. Description of the Related Art As a general electrophotographic technique, an image bearing member having a cylindrical substrate surface is charged by applying either positive or negative electric charge by a charger. Thereafter, the desired pattern was image-exposed, and the charge generated from the charge generating layer of the image carrier was used to cancel the surface charge, thereby forming an electrostatic charge image on the image carrier surface and charged to either positive or negative. Using toner particles,
By performing the developing process, a toner image is formed in accordance with the electrostatic charge pattern of either the exposed portion or the unexposed portion,
This is transferred to a final support member such as plain paper to obtain an output image.

As one of the developing systems at that time, there is a method described in JP-A-54-43036. In this method, a thin layer of toner is coated on a developer carrier, and a charge is applied to the thin layer by triboelectric charging.They are brought close to an electrostatic charge image under the action of a magnetic field, and are opposed to each other without contact. , To be developed.

In addition, one-component non-contact development using non-magnetic toner, and one-component non-contact development using non-magnetic or magnetic toner
Component contact development, using non-magnetic toner and magnetic carrier 2
Various development methods such as component development have been proposed and put to practical use.

In the above-described developing method, a charge is applied to toner particles having a relatively high resistance, and the charged toner particles are transferred to the image carrier by utilizing the force of an electric field generated by an electrostatic charge pattern on the image carrier. It is characterized by being constrained to the surface.

[0006] In addition to the above-described developing method in which development is performed by the action of an electric field, development is performed using toner particles having a relatively low resistance value, injecting charges into the toner particles, and restraining the toner particles on the image carrier by Coulomb force. There is a method.

Among them, a one-component developing system using a magnetic conductive toner, as described in US Pat. No. 2,846,333 to Wilson, has long been known. In addition, the Shelly method described in U.S. Pat. No. 3,563,734 as being put into practical use, and U.S. Pat.
No. 9258, Kotz
The method is well known.

[0008] A developing method using a non-magnetic conductive toner is described in US Pat.
No. 76144, as well as Gundrush
Lach) in U.S. Pat. No. 3,166,432.

As a method of locally developing the toner by conducting the toner conductivity, a developing method using a photoconductive toner has been proposed.

A typical example is US Pat. No. 2,758,893.
No. 9, Sugarman (Sugarman)
man) system. This was done by uniformly applying photoconductive toner on a transparent conductive support member such as Nesa glass, and performing image exposure from the transparent conductive support member side while applying a voltage between the photoconductive toner and the counter electrode. The toner particles
In this method, an electric charge is injected from the counter electrode to become conductive, electrostatically restrained by the counter electrode, and an image is formed directly on the recording sheet.

Further, a magnetic carrier for carrying and transporting the photoconductive toner is coated on a developer carrying member by a developer regulating means, and these are uniformly charged by corona charging, and then irradiated with light. The conductive toner is formed with a pattern of change in the amount of change in charge according to the brightness of light, and the photoconductive developer is transferred to the transfer unit by the magnetic transport force of a permanent magnet contained in the developer carrier, There is a method in which a bias is applied to a counter electrode to which a bias is applied via a transfer material, and the toner having the remaining charge distribution is directly transferred to the transfer material, leading to image formation.

The electrophotographic technique using the conductive toner as described above is a developing method in which a toner image is formed on the surface of an image carrier by utilizing an electrostatic restraining force.

[0013]

However, due to the recent high resolution of output images, it has become difficult to achieve both high density and high resolution mainly in image formation using digital machines.

For example, in a developing system in which development is mainly performed by the force of an electric field using the above-described non-conductive toner, when an image is exposed by an optical system having a spot diameter of about 40 to 80 μm, one pixel is exposed. The dots are sized according to the resolution of the device (42.3 μm at 1200 dpi, 1200 dpi
i, the contrast Vcont-D between the photoconductor and the developing sleeve for developing to 21.2 μm) and the contrast Vcont between the photoconductor and the developing sleeve for uniformly and sufficiently forming a solid image. There is a relationship such as Vcont-D <Vcont.

This is because, when an isolated dot is exposed to an image due to an increase in resolution, a potential pattern formed by adjacent charges overlaps due to a small distance between adjacent pixels, and a broad and overall high potential distribution is formed. It is thought that it is because. Since the average potential is relatively high, and there are fine undulations, toner particles adhere more than necessary due to a relatively strong electric field near the edge of an image pattern formed by accumulation of dots such as halftones. As a result, an excessive development phenomenon occurs.

Therefore, when giving priority to forming a solid image having a uniform density, and when outputting a graphical image such as a photograph, the size of one dot forming the image becomes unnecessarily large. The density of the output graphic image is too high. Conversely, when a graphic image is prioritized, the density of a solid portion in the image becomes low, and it is difficult to realize good gradation properties for all image patterns.

Accordingly, it is an object of the present invention to provide an image forming apparatus capable of realizing good gradation in a wide range from a graphic image to a solid image area, and achieving both high density and high resolution.

[0018]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
A photoconductive image carrier, a charging unit for uniformly charging the image carrier, an exposure unit for exposing an image of the charged image carrier surface to form an electrostatic latent image, and Developing means for forming a toner image by attaching a toner to the electrostatic latent image by the developer carrying member, the developing device including a developer carrying member for conveying the toner to the image carrying member; In the image forming apparatus provided with a transfer means for transferring to, using photoconductive particles for the toner used in the developing means,
An image forming apparatus, wherein the amount of toner stacked on the image carrier is controlled by controlling the conductivity of the toner according to an image pattern.

It is preferable that the developer carrying member includes a translucent supporting base, and a light source for irradiating the photoconductive toner with light is provided therein. It is preferable that the image bearing member has a charge generation layer, and the charge generation layer has no sensitivity to a light source wavelength used when irradiating the conductive toner. It is preferable that the conductive toner has sensitivity to a light source wavelength used when irradiating the conductive toner. According to another aspect, it is preferable that the image carrier has a light-transmissive substrate, and the exposure device is provided inside the image carrier, and image exposure is performed from the back side of the substrate.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

First Embodiment FIG. 3 shows an electrophotographic image forming apparatus according to a first embodiment. The image forming apparatus includes an image carrier 1, a charger 2, an image exposing unit 7, a developing unit 9, a transfer charger 4,
A fixing device 5 and a cleaning device 6 are provided.

In the above image forming apparatus, the photosensitive drum 1
Is uniformly charged by the charger 2, and an electrostatic latent image is formed on the surface of the photosensitive drum 1 by exposure of the image exposing unit 7. The electrostatic latent image is developed by a developer carried on the developer carrier 3 of the developing device 9 to be a visible image, and the visible image is transferred to the transfer material 10 by the operation of the transfer charger 4.
The transfer material 10 is conveyed to the fixing device 5, where the visible image is fixed to obtain a permanent image.

1 and 2, the structure of this embodiment will be described in more detail.

The image carrier 1 may be of a function-separated type having a two-layer structure of a charge generation layer and a charge transport layer on the lowermost layer of a conductive support base, or a single layer type. . The image carrier 1 of the present embodiment has a function-separated type two-layer structure. As shown in FIG. 2, the image carrier 1 includes a base 19, a charge generation layer 20, and a charge transport layer 21 thereon.

As the substrate 19 used for the image carrier, a substrate having conductivity itself, for example, aluminum,
Aluminum alloy, copper, zinc, stainless steel, chromium, titanium, nickel, magnesium, indium, gold, platinum, silver, iron, and the like can be used. In addition, it is possible to use a material such as aluminum, indium oxide, tin oxide, gold, or the like formed on a dielectric substrate such as plastic by vapor deposition or the like to form a conductive layer, or a material obtained by mixing conductive fine particles with plastic or paper. it can.

As a material of the charge generation layer 20, for example,
Selenium-tellurium, pyrylium dye, thiopyrylium pigment, phthalocyanine pigment, anthantrone pigment, dibenzopyrenequinone pigment, pyranthrone pigment, trisazo pigment, disazo pigment, azo pigment,
Indigo pigments, quinacridone pigments, cyanine pigments and the like can be used.

The material of the charge transport layer 21 is poly-N
-A polymer compound having a heterocyclic ring or a condensed polycyclic aromatic compound such as vinyl carbazole or polystylanthracene, a heterocyclic compound such as pyrazoline, imidazole, oxazole, oxadiazole, triazole or carbazole, or a tricyclic compound such as triphenylmethane. A low molecular compound such as a triarylamine derivative such as a reel alkane derivative or triphenylamine, a phenylenediamine derivative, an N-phenylcarbazole derivative, a stilbene derivative, or a hydrazone derivative can be used.

As the charge generation material and the charge transport material, a binder polymer is used as necessary. Examples of the binder polymer include polymers and copolymers of vinyl compounds such as styrene, vinyl acetate, vinyl chloride, acrylate, methacrylate, vinylidene fluoride, trifluoroethylene, polyvinyl alcohol, polyvinyl acetal, and polycarbonate. ,polyester,
Polysulfone, polyphenylene oxide, polyurethane, cellulose resin, phenolic resin, melamine resin,
Silicon resin, epoxy resin and the like can be mentioned.

In the photoconductive layer, which is the charge generation layer 20, additives other than the above compounds can be used for improving mechanical properties and improving durability. As such additives, an antioxidant, an ultraviolet absorber, a stabilizer, a crosslinking agent, a lubricant, a conductivity controlling agent, and the like are used.

Examples of the charging means 2 used for the primary charging include a non-contact type using a corona charger and a contact type using a roller charger.

The optical system 7 as an exposure means includes a scanner type using a semiconductor laser,
Other optical systems such as L elements and plasma light emitting elements can also be used.

As is well known, a photoconductive toner which is a developer used in the developing process can be made of a material containing zinc oxide, a binder resin, and a sensitizing dye. As the binder resin at this time, styrene-acryl-based, polyester-based, polyvinyl chloride-based, polyacryl-based, polyurethane-based, or epoxy-based resin can be used. It is also possible to use a photoconductive resin such as polyvinyl carbazole alone or with an insulating resin.

The developing device 9 includes a light source 17 for irradiating conductive toner light therein, and a developer carrier 3 having a light-transmissive support base 22 and a toner layer abutting on the developer carrier 3. An elastic blade 16 which is a layer thickness regulating member for regulating the thickness.

Particle size 5-1 produced using the above materials
Photoconductive toner particles 24, 25, 26 of about 0 μm
Is coated thinly and uniformly with a resilient blade 16 on a developer carrier 3 disposed in contact with the image carrier 1, and charged to a desired negative polarity when passing through the resilient blade 16. I do.

By applying an electric field to the developer carrier 3, the toner particles 24 and 25 are attracted and restrained to the portion of the image carrier 1 where the potential E has decreased due to the image exposure, and the laminated toner image is formed. It is formed on the image carrier 1. At this time, the toner particles 26 on the region outside the region where the potential E has dropped are not restrained on the image carrier 1.

Here, the light source 17 for irradiating the conductive toner light, which is disposed inside the developer carrying member 3, irradiates the portion where the toner concentration becomes too high through the light transmitting support base 22 with light. Perform 23. As a result, only the toner particles 25 at that location become conductive, and charge is injected according to the potential difference generated between the image carrier 1 and the developer carrier 3 which is the counter electrode. Is formed in a single layer, and gradation control by density modulation becomes possible.

After that, the conductive toner particles 24 lose the conductivity in the transfer section 14 and can be well transferred to the final supporting substrate 10 such as plain paper by a conventional transfer technique.

At this time, if the charge generation layer 20 of the image carrier 1 has no sensitivity to the light source wavelength used for irradiating the conductive toner, or if the charge generation layer 20 has sensitivity,
It is preferable that the toner is almost completely absorbed by the conductive toner carried on the developer carrier 3.

Therefore, when light sources having different wavelengths are used for the light source for the image exposure light and the light source for irradiating the conductive toner, a light source having a short wavelength for the image exposure light and a light source 23 for irradiating the conductive toner are used. It is preferable to use a long wavelength light source. This is because image exposure on the image carrier requires higher resolution than light irradiation on the conductive toner.

For example, various semiconductor lasers (650n
m, 830 nm, etc.), various LED arrays (GaAsP
/ 650 nm, GsAlAs / 650-830 nm, G
aAsP / 580-650 nm, GsAs-based / 920-920 nm
1000 nm, others), various gas lasers (He-Ne /
632 nm, He-Cd / 442 nm), and various other optical systems such as an EL element and a plasma light emitting element can be used. From these optical systems, an appropriate combination is selected, and the spectral sensitivity of the photosensitive substance is adjusted. By doing so, a configuration that produces the above-described effects becomes possible. Further, by combining various optical filters such as a low-pass and a high-pass with the optical system at this time, the above-mentioned effect can be more efficiently produced.

Further, by increasing the absorption efficiency of the photoconductive toner, the photoconductive toner particles can be irradiated with light without changing the photoconductive layer of the image carrier. In reality, when irradiating the photoconductive toner with light,
Infrared region or red light is often used and has an absorption region in a long wavelength region, anthraquinone type, polymethine type, cyanine type, aminium type, diimonium type,
It is also possible to use a dye coated with various binder resins, as long as the coloring of the toner is not impaired.

As the binder resin used at that time, polymers and copolymers of vinyl compounds such as styrene, vinyl acetate, vinyl chloride, acrylates, methacrylates, vinylidene fluoride, trifluoroethylene, etc., polyvinyl alcohol, Polyvinyl acetal, polycarbonate, polyester, polysulfone,
Polyphenylene oxide, polyurethane, cellulose resin, phenol resin, melamine resin, silicon resin, epoxy resin, and the like can be used.

With the above-described configuration, by irradiating the toner particles 24 and 25 confined to the image carrier with light at desired portions according to the potential pattern on the surface of the image carrier, By imparting conductivity, it becomes possible to perform development processing in a single layer only on toner particles at a desired site.

As described above, by giving information to the toner itself in accordance with the image pattern, the toner particles can be controlled by the electrostatic charge pattern on the image carrier. By using two types of gradation control methods, mainly, gradation control in the form of density gradation by writing information into the image, it has been difficult with conventional developing systems.
It is possible to reproduce gradation in a wider range from a graphical image area to a solid image area, and it is possible to output an image with high resolution and excellent gradation.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIGS. In the present embodiment, in addition to the configuration of the first embodiment, the base of the image carrier 1 is a translucent substrate 31, and a light irradiator 18 for image exposure is provided therein, and the charge of the image carrier 1 is changed. A light-shielding layer 28 that absorbs light from a light source that emits light from the inside of the developer carrier 3 is provided on the transport layer 21,
It is characterized in that the configuration does not affect the charge generation layer 20 of the image carrier 1 when the conductive toner is irradiated with light.
(Of course, in the present embodiment, the image exposure device 7 of the first embodiment is unnecessary.) As the light shielding layer 28, for example, when the wavelength of the light source for irradiating the conductive toner with light is in the infrared or red region, A layer can be formed by dispersing an anthraquinone-based, polymethine-based, cyanine-based, aminium-based, or diimonium-based dye having absorption in a long wavelength region in the same binder resin as the charge transport layer 21.

As described above, by performing the image exposure from the inside of the image carrier 1 and providing the light shielding layer 28 having an absorption at the wavelength of the light source for irradiating the conductive toner on the uppermost layer of the image carrier 1, Light irradiation on the conductive toner can be performed without affecting the charge generation layer 20 of the image carrier 1.

According to the above-described structure, without affecting the charge generating layer of the image bearing member, the toner particles can be controlled mainly by the area latent tone by the electrostatic latent image pattern on the image bearing member. By using two types of gradation control methods, mainly, gradation control based on density gradation by writing information to the image, it is difficult to develop a graphical image area from a solid image, It is possible to reproduce the gradation in a wider range up to the region, and it is possible to output an image with high resolution and excellent gradation.

[0048]

As is apparent from the above description, the image forming apparatus according to the present invention uses photoconductive particles for the toner used in the developing means and controls the conductivity of the toner according to the image pattern. Thus, by controlling the amount of toner stacked on the image carrier, the electrostatic charge pattern on the image carrier, mainly, in addition to the area gradation gradation control, by writing to the toner particles, By using two types of tone control methods, mainly, tone control in the form of density tone, a wider range from the graphical image area to the solid image area, which was difficult with the conventional developing system, , And it is possible to output an image with high resolution and excellent gradation.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an electrophotographic apparatus according to a first embodiment.

FIG. 2 is a conceptual diagram for explaining a developing system of the apparatus of FIG.

FIG. 3 is a schematic diagram illustrating the entire configuration of the image forming apparatus according to the first exemplary embodiment.

FIG. 4 is a configuration diagram illustrating an electrophotographic apparatus according to a second embodiment.

5 is a conceptual diagram for explaining a developing system of the apparatus of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image carrier 2 Charging means 3 Developer carrier 4 Transfer means 7 Exposure means 9 Developing means 17 Light source for conductive toner 18 Light source for image exposure (exposure means) 19 Image carrier base 20 Charge generation layer 22 Developer carrier Substrate 31 for image carrier

Claims (5)

[Claims] 1. A photoconductive image carrier, a charging unit for uniformly charging the image carrier, an exposure unit for exposing the charged image carrier surface to form an electrostatic latent image, and a toner. Developing means for carrying a toner carrying the toner to the image carrier by carrying the toner, forming a toner image by attaching toner to the electrostatic latent image by the developer carrying body, and a toner obtained In an image forming apparatus having a transfer unit that transfers an image to a final support material, by using photoconductive particles for the toner used in the developing unit, by controlling the conductivity of the toner according to the image pattern, An image forming apparatus, wherein the amount of toner stacked on the image carrier is controlled. 2. The image forming apparatus according to claim 1, wherein said developer carrier includes a light-transmitting support base, and further includes a light source for irradiating photoconductive toner with light. 3. The image bearing member has a charge generation layer, and the charge generation layer has no sensitivity to a wavelength of a light source used when irradiating the conductive toner. Image forming apparatus. 4. The image forming apparatus according to claim 3, wherein the conductive toner has sensitivity to a light source wavelength used when irradiating the conductive toner. 5. The image bearing member according to claim 1, wherein the image carrier has a light-transmitting base, and the exposure means is provided inside the base, and image exposure is performed from the back side of the base. Any one of the image forming apparatuses.