JPH11258877A - Recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a recorder low in cost and high in productivity by forming an image having stable density without being influenced by temperature and humidity as an electrophotographic recorder for forming an electrostatic latent image by radiating image light to an electrified photoreceptor. SOLUTION: By combining the photoreceptor whose potential attenuation factor by exposure has positive characteristic to the temperature and the humidity with a electrifying device whose initial electrification potential has the positive characteristic to the temperature and the humidity, an area where the light discharge characteristic curves of the photoreceptor at a high temperature and high humidity and low temperature and low humidity cross is given. The exposure at a quantization level 1 in a multilevel error diffusion method is set to this cross area. A developing device having the characteristic that developing weight is saturated in an area where developing contrast potential is comparatively low is used as the developing device, and the exposure at the quantization level 2 is set to the saturation area. Thus, the stable image having no density fluctuation to environmental change is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an indirect transfer type recording apparatus for forming a toner image using an electrostatic latent image or the like.
More specifically, the present invention relates to an electrophotographic indirect transfer recording apparatus including a step of forming an electrostatic latent image by irradiating image light onto a charged photoconductor.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, a charging step for uniformly charging the surface of a latent image carrier,
An exposure step of forming an electrostatic latent image by irradiating the charged latent image carrier surface with image light, a developing step of attaching toner to the electrostatic latent image to form a toner image, and transferring the toner image An image is formed by a transfer step of transferring to a material, a fixing step of fixing a toner image on the transfer material, and a cleaning step of removing toner remaining on the surface of the latent image carrier in the transfer step. Further, a charge elimination step for electrically initializing the surface of the latent image carrier is provided as necessary.

FIG. 11 shows a schematic configuration diagram of a conventional electrophotographic color image forming apparatus. In this apparatus, a function-separated type photoreceptor 101 having a charge generation layer and a charge transport layer is used as a latent image carrier, and this photoreceptor 101 is charged to a desired initial charging potential VH by a scorotron 102, and an exposure device 103 Irradiating exposure light corresponding to the image signal from the above, an electrostatic latent image is formed on the photoconductor 101. After a toner image is formed by a developing device 104a corresponding to a desired color of the developing unit 104, the recording paper transport drum 10 is transferred by a corotron 107 as a transfer unit.
The toner image is transferred to the recording paper 106 adsorbed on the recording paper 5. Then, the toner remaining on the photoconductor 101 without being transferred in the transfer process is removed by the cleaning unit 109, the photoconductor 101 is electrically initialized by the discharging lamp 110, and the recording cycle of the next recording color is started. Continue. In this conventional example, a color toner image is formed on the recording paper 106 by repeating the above-described recording in the order of black, yellow, magenta, and cyan. Finally, the recording paper 106 is peeled off from the recording paper transport drum 105 and fixed. The toner image is fixed on the recording paper 106 by passing through the container 108, and a final color image is formed.

Here, the above-mentioned photosensitive member 10 which is generally used
No. 1 is known that its photodischarge characteristics change depending on the environment where the photoconductor is placed. Specifically, as shown in FIG. 12, the photodischarge characteristics of the photoreceptor, that is, the photoreceptor surface potential VL after the exposure is the same as the temperature and humidity in the comparison with the same exposure amount in a normal use range of 10 mJ / m ² or less. Fluctuates by about 20 to 50 V due to the influence of. Therefore, in the case of multi-value recording such as a conventional color image, there is a problem that the surface potential of the photoconductor after exposure, that is, the potential VL of the electrostatic latent image fluctuates, and the density of the recorded image fluctuates.

Therefore, as shown in FIG. 11, a potential sensor 111 serving as a surface potential detecting means is provided in the space between the exposure section and the development section so as to approach / oppose the photoconductor 101, and the exposed surface of the photoconductor 101 is provided. A method for controlling the electric potential is employed in an actual machine. Specifically, at the time of non-printing, the exposure amounts P ₁ , P ₂ (P ₂ ) at two points before and after the exposure amount Pm in the standard environment according to the reference image signal, for example, the image signal Cm having a 50% area ratio.
₁ <Pm <P ₂ ), and the surface potential V ₁ , V ₂ at that time is measured by the potential sensor 111. Then, from the surface potentials V ₁ and V ₂ , the exposure amount Pm ′ in the environment where the photoconductor potential Vm corresponding to the image signal Cm of 50% area ratio is obtained from the surface potentials V ₁ and V ₂ is linearly interpolated between two points P ₁ and P _2. Thus, stable surface potential control can be performed with respect to environmental fluctuations.

[0006] However, such conventional control requires an expensive potential sensor, and it is difficult to reduce the cost of the apparatus. Also, in order to respond to environmental changes as faithfully as possible, it is necessary to perform a control cycle for setting the potential at a considerable frequency, for example, once several tens of minutes before recording, which lowers productivity. There is a problem.

On the other hand, it is considered to reduce the diameter of the photoconductor in order to reduce the size of the apparatus. However, as the diameter of the photoconductor is reduced, the photoconductor is worn by a contact member such as a cleaning blade, and the photoconductor is worn. There is a problem that the life is shortened.

In order to solve this problem, Japanese Patent Application Laid-Open Nos. 59-133573 and 59-157661 disclose a cleanerless recording apparatus which collects the transfer residual toner in a developing device simultaneously with development without providing a cleaning step. It is proposed in Japanese Patent Publication No.

The applicant of the present invention has disclosed in Japanese Patent Application Laid-Open No. 9-221001.
As described in Japanese Patent Publication No. 0, a recording apparatus has been proposed in which a fine particle applying means for applying fine particles on a photoreceptor is provided, and after the fine particles are adhered, a toner image is formed by a developing means. FIG. 13 shows a schematic configuration diagram of a recording apparatus of this type. In this method, the photosensitive member 12 is provided upstream of the developing unit 124 for forming a toner image in the process direction.
1 is provided with fine particle applying means 131 for applying fine particles to the photosensitive member 121 before forming a toner image. As a result, the adhesive force between the toner and the photoreceptor can be reduced, and the transfer efficiency can be remarkably improved, and the problems of the positive ghost and the negative ghost, which are the drawbacks of the conventional cleanerless system, are solved, and stable over time. A recording device can be provided. As a result, there is no need to provide a cleaning unit as shown in FIG.
Is smaller than conventional (diameter 15m)
m or less) can be achieved. However, the size of the potential sensor used in the aforementioned potential control means is currently 5
The limit is about mm square, and it is difficult to install the photoconductor close to a photoconductor having a diameter of 30 mm or less. Therefore, when the diameter of the photoconductor is reduced, the conventional potential control method cannot be used, and there is a problem that the image density fluctuates due to a change in environment.

Further, for example, 256-color image information
In a printing apparatus having gradation, 8-bit information is required for one pixel. In the case of color printing, 32 bits are required for four colors.
Since the amount of information is a bit, an image processing speed and a memory capacity are required to be larger than those of a single color. Therefore, in recent years, a recording method using a multi-level error diffusion method has been proposed as a pseudo-halftone reproduction method intermediate between multi-level multi-level recording and binary recording. This method is a method that can express halftones in a pseudo manner with a small amount of information. However, in order to stabilize all the multi-valued levels, the latent image potential range to be used is the same as in the above-described multi-valued recording. It is still necessary to control the potential over a wide range. For example, even in a method of performing non-linear quantization without using an unstable region as proposed in Japanese Patent Application Laid-Open No. 5-336373, it is necessary to keep the stable region stable against error factors such as the environment. Measures are necessary.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to obtain a stable image in any environment without being affected by the temperature and humidity of the environment. It is an object of the present invention to provide a low-cost and high-productivity recording apparatus. Another object of the present invention is to provide a compact recording apparatus capable of obtaining a high-quality image even in a cleanerless recording apparatus that hardly wears the photosensitive member.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a photoconductor having a surface on which a latent image is formed due to a difference in electrostatic potential, and to uniformly apply a charge to the photoconductor. An electrophotographic recording apparatus comprising: a charging unit that performs exposure, an exposure unit that exposes the photoconductor in accordance with an image signal, and a developing unit that develops an exposed area of the photoconductor by attaching toner. The body has a photodischarge characteristic, that is, a potential decay rate due to exposure has a positive characteristic with respect to temperature and humidity, and the charging unit has a charging characteristic, that is, an initial charge potential with a positive characteristic with respect to temperature and humidity. By combining the photoconductor and the charging unit, a region where a photodischarge characteristic curve of the photoconductor crosses when a temperature and humidity environment changes is provided, and a halftone density of the exposure unit is output. Exposure of the at least one light intensity level for that, it is achieved by a recording apparatus according to claim set in the exposure amount in the intersection region.

According to another aspect of the present invention, in addition to the above-described feature, the developing unit is configured to determine a potential difference between a DC component of a developing bias potential and a potential of an exposure unit of the electrostatic latent image. This is achieved by a recording apparatus characterized by having a developing characteristic having a saturation region in which a developing toner amount hardly increases with an increase in the developing potential contrast in a certain high developing potential contrast portion.

Further, the above object is achieved by a recording apparatus as described in claim 3, wherein fine particles having an average particle diameter smaller than that of the toner are provided on the surface of the photoreceptor.

[0015] Further, in addition to the above-mentioned feature, the object is that the charging means is arranged so as to approach or contact the photoconductor, and to charge the photoconductor. This is achieved by a recording apparatus characterized in that the voltage applied to the charging means is controlled at a constant voltage.

That is, the present invention provides a photoconductor having a photodischarge characteristic, that is, a potential decay rate upon exposure having a positive characteristic with respect to temperature and humidity, and a charging characteristic, that is, an initial charge potential having a positive characteristic with respect to temperature and humidity. Combination with the charging device having the above, by providing a region where the photodischarge characteristic curve of the photoconductor when the temperature and humidity environment changes, to reduce the fluctuation of the initial charging potential and photoconductor photodischarge characteristics due to temperature and humidity fluctuation. It becomes possible to cancel by the combination of the photoconductor and the charging device having the above characteristics, and further, by performing image exposure of at least one light amount level of the multi-level error diffusion method by the exposure amount in the intersection area which is the cancellation point, It is possible to suppress the fluctuation of the latent image potential due to the environmental fluctuation. In addition, since the developing means has a developing characteristic in which a developing toner amount is in a saturation region in a high developing potential contrast portion, it is possible to suppress a density fluctuation of a recorded image by a multi-level error diffusion method when an environment changes. Becomes As a result, a recording apparatus having excellent environmental stability can be realized without using a complicated and expensive potential control means.

Hereinafter, the phenomenon of the present invention will be described in detail. As shown in FIG. 12, the photodischarge characteristics of the function-separated type photoconductor usually used in electrophotography show that the charge mobility increases at high temperature and high humidity, and the photoconductor surface potential after exposure is low at low temperature and low humidity. It will be lower than that. Accordingly, when the photosensitive member is charged by a charging method based on a constant current control such as a scorotron conventionally used, the initial charging potential becomes substantially constant, and the characteristics shown in FIG. 12 are obtained.

Therefore, in the present invention, as a charging method in which the charging voltage has a positive characteristic with respect to temperature and humidity, a contact-type charging means represented by a BCR, a film or the like is used. This charging means controls the applied voltage for charging the photoconductor at a constant voltage. This charging method, at high temperature and high humidity,
Due to the change in the resistivity of the charging means approaching or in contact with the photoconductor, a phenomenon of charge injection into the photoconductor occurs,
The initial charging potential of the photoconductor increases. On the other hand, when the temperature is low and the humidity is low, the initial charging potential of the photoconductor decreases. It has been found that this phenomenon is not so remarkable in the discharge at the superimposed voltage of DC and AC used in the conventional contact-type charging means, but is remarkable in the discharge at DC voltage.

Here, considering the combination of the photosensitive member and the charging means, the initial charging potential V at high temperature and high humidity is considered.
H increases and the surface potential VL after exposure decreases, but at low temperature and low humidity, the initial charging potential VH decreases and the surface potential VL after exposure increases. FIG. 5 shows this phenomenon in terms of the relationship between the photoconductor surface potential and the exposure energy while varying the environmental conditions.
The curves A and C of the photodischarge characteristics at high temperature and high humidity and at low temperature and low humidity intersect in the exposure region of ^{3 to 4} mJ / m ² . In the present invention, it is possible to obtain a stable post-exposure potential with respect to environmental fluctuations by performing image exposure using the crossed exposure area as an exposure amount of at least one light amount level of the multi-level error diffusion method. I paid attention.

Further, in the present invention, as shown in the development characteristics of FIG. 6, the development contrast obtained by the image exposure of the maximum value of the multi-level error diffusion method (around 150 to 200 V in FIG. 6).
It was noted that by combining a developing means having a development saturated region in (2), an image density more stable against environmental fluctuations can be obtained.

Based on the above results, the multi-valued error diffusion method
FIG. 7 is an explanatory diagram showing the flow from the exposure shape to the developed image shape, taking the value case as an example. In FIG. 7, the exposure amount at the quantization level 1 is set to be the intersection region of the above-described photodischarge characteristics, and the quantization level 2 (maximum value) is set to the exposure amount at the development saturation region. I have. This allows
In the exposure at the quantization level 1, the fluctuation of the latent image potential due to the environmental fluctuation can be suppressed, and in the exposure at the quantization level 2, the fluctuation of the image density due to the development can be suppressed.

Further, as a recording apparatus in which a photoreceptor is reduced in diameter in order to reduce the size of the apparatus, a toner image is formed after fine particles are deposited on the photoreceptor, and an image recording process is performed without abrasion of the photoreceptor. Repeated, cleanerless recording devices can be used.

In this recording apparatus, the fine particles to be deposited on the photoreceptor before forming the toner image include titanium oxide, alumina, silica, barium titanate, and the like.
Inorganic fine powders such as calcium titanate, strontium titanate, zinc oxide, magnesium oxide, zirconium oxide, barium sulfate, barium carbonate, calcium carbonate, silicon carbide, silicon nitride, chromium oxide, red iron oxide, polyacrylate, polymethacrylate, poly Organic fine powders such as methyl methacrylate, polyethylene, polypropylene, polyvinylidene fluoride, and polytetrafluoroethylene can be used. In consideration of environmental stability, it is desirable that these fine particles have low hygroscopicity. In particular, in the case of inorganic fine powders having hygroscopicity such as titanium oxide, alumina and silica, it is preferable to use those subjected to a hydrophobic treatment. . Hydrophobization treatment of these inorganic fine powders, for example, dialkyl dihalogenated silane, trialkyl halogenated silane, silane coupling agent such as alkyl trihalogenated silane or hydrophobic treatment agent such as dimethyl silicone oil and the fine powder and The reaction can be performed at a high temperature.

The method for attaching the fine particles to the photoreceptor can be any method, such as a method of mechanically attaching the particles, a method of electrically attaching the particles, a method using both of them, and the like, as long as the particles can be attached to the photosensitive member. Method is also acceptable. As a method of mechanically attaching, there is a method by rubbing,
Examples of such a method include a method of rubbing with a roll, brush, felt, web, or brush. As a roll, metal or
A rigid roll formed of a rigid body such as hard plastic and an elastic roll using a material having elasticity such as rubber can be cited.However, the elasticity is difficult because of the pressure at the sliding nip and the ease of adjusting the nip width. Rolls are easier to use. Specific examples of the brush include a magnetic brush using magnetism and a fur brush. By applying an electric field in addition to such a mechanical attachment method, the attached state of the fine particles can be further stabilized.

In addition, such fine particles may adhere to the photoreceptor in the form of a film during use.
For example, a material that easily causes filming, such as zinc stearate and magnesium stearate, naturally easily causes filming also with respect to the toner, and has a strong adhesive force to the toner. Therefore, when fine powder of a material that easily causes filming is adhered to the photoreceptor, the effect of stably increasing the transfer efficiency of the toner over a long period of time cannot be obtained.

The state of adhesion of the fine particles on the photoreceptor may be one type of fine particles or a plurality of types of fine particles at the same time. It suffices if fine particles are interposed between the toner and the photoconductor so that the adhesive force between the toner and the photoconductor can be reduced.

As a method of electrically attaching the fine particles, there is a method of dispersing the fine particles in a cloud shape and attaching the fine particles to the photosensitive member by the electric field. Means for dispersing and adhering the fine particles in the form of a cloud include, for example, a method using mechanical vibration, air, ultrasonic waves, and an alternating electric field, and adhering the fine particles to, for example, a roll, brush, web, or brush. In this case, a method of rotating, vibrating, or moving them may be used. Furthermore, an adhesive layer is provided on the photoconductor,
Fine particles dispersed in the form of a cloud by the above-described means may be attached thereon by a method such as sprinkling. As such an adhesive layer, a substance exhibiting stable adhesive properties over time is desirable. For example, silicone oil exhibiting low volatility and chemically stable properties is suitable.

By these means, the transfer rate can be remarkably improved, and a cleaning means such as a blade cleaner which has conventionally caused wear of the photoreceptor can be removed, so that the diameter of the photoreceptor can be reduced. it can.

[0029]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a recording apparatus according to an embodiment of the present invention. This recording device,
A photoreceptor 1 on which an electrostatic latent image is formed by irradiating image light after uniform charging, a charging device 2 around the photoreceptor 1 for uniformly charging the surface of the photoreceptor 1, An image writing device 3 for irradiating the photosensitive member 1 with image light based on image data to form a latent image, a developing device 4 for selectively transferring toner to the latent image and visualizing the latent image, and a conveying unit (not shown) sequentially. The transfer device 5 includes a transfer device 5 that transfers a toner image on the surface of the photoconductor to the recording paper 6 that is conveyed, and a charge removal device 7 that neutralizes the surface of the photoconductor 1 after the transfer of the toner image. This recording apparatus is of a cleanerless type, and does not have a cleaning device. Further, fine particles having a smaller particle diameter than the toner are almost uniformly attached to the surface of the photoreceptor 1 in advance.

The photoreceptor 1 is a function-separated type photoreceptor as shown in FIG. 2, in which an undercoat layer 22 is formed on a conductive support 21 as necessary, a charge generation layer 23, and a charge transport layer. The structure is such that the layers 24 are sequentially laminated. The photoreceptor 1 has a photodischarge characteristic, that is, a potential decay rate due to exposure has a positive characteristic with respect to temperature and humidity. At high temperature and high humidity, the charge mobility increases, and the It has the property that the surface potential is lower than at low temperature and low humidity.

The following materials are used for the photosensitive member 1. The conductive support 71 is made of aluminum,
Copper or stainless steel metal drums and sheets, plastic film and paper laminated with aluminum or other metal foil, or aluminum or metal deposited, and conductive on metal or resin drums What applied the resin layer which dispersed the particle | grain etc. can be used. If necessary, the surface of the conductive support may be subjected to a surface roughening treatment for preventing interference fringes.

The undercoat layer 72 is provided as necessary to improve the adhesion between the conductive support and the photosensitive layer and to prevent coating defects of the photosensitive layer. Examples of the material for forming the undercoat layer include thermoplastic resins such as polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl methyl ether, polyamide, thermoplastic polyester, phenoxy resin, casein gelatin, nitrocellulose, polyimide, and polyethylene imine. And thermosetting resins such as epoxy resins, melamine resins, phenol resins, and polyurethane resins; and organic metal compounds such as titanium coupling agents, zirconium coupling agents, and silane coupling agents. These materials can be used alone or in combination of two or more. The formation of the undercoat layer
After dissolving and mixing the above materials with a solvent as needed, dilute, apply on a conductive support by spray coating, dip coating or the like, and then dry in a temperature range of 100 to 200 ° C. This is done by: The thickness of the undercoat layer is
The thickness is arbitrarily set in the range of 0.1 μm to 10 μm, but particularly preferably in the range of 0.5 μm to 2 μm from the viewpoint of ease of production.

The charge generation layer 73 is formed by dissolving a binder resin in a solvent, dispersing a charge generation material therein, and applying a spray coating method.
After being applied by a dip coating method or the like, a dried product or a product obtained by directly depositing a charge generation material by a vacuum deposition method or the like is used. Examples of the charge generation material include azo dyes such as chlorodian blue, quinone pigments such as anthrone, pyrenequinone, quinocyanine pigments, perylene pigments, indigo pigments, bisbenzimidazole pigments, metal-free phthalocyanines, copper phthalocyanines, vanadyl phthalocyanines, and titanyl phthalocyanines. And phthalocyanine pigments such as gallium phthalocyanine, azulhenium salts, squarylium pigments, quinacridone pigments and the like.

Examples of the binder resin include polyvinyl butyral, polyarylate (a polymer of bisphenol A and phthalic acid), polycarbonate resin, polyester resin, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, acrylic resin, and poly (vinyl acetate). Acrylamide, polyamide resin, polyvinyl pyridine, cellulosic resin,
Insulating resins such as urethane resin, epoxy resin casein, polyvinyl alcohol, and polyvinylpyrrolidone are exemplified. The thickness of the charge generation layer is arbitrarily set in the range of 0.01 μm to 5 μm, but preferably in the range of 0.1 μm to 0.5 μm from the viewpoint of ease of production.

The charge transport layer 74 is formed by dissolving a binder resin in a solvent, applying a solution obtained by adding a charge transport agent to the solution by a spray coating method, a dip coating method or the like, and then drying. You. The charge transport agent is a polycyclic aromatic compound such as anthracene, pyrene, phenanthrene, or
Compounds having a nitrogen-containing heterocycle such as indole, carbazole, imidazole, and the like, pyrazoline compounds, hydrazone compounds, triphenylmethane compounds, triarylamine compounds, enamine compounds, stilbene compounds, and the like can be used. Examples of the binder resin used for the charge transport layer include polycarbonate resin, polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl acetate resin, styrene-butadiene copolymer, and vinylidene chloride. -Acrylonitrile copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicon-alkyd resin, phenol-formaldehyde resin, styrene-alkyd resin, poly-N- Known resins such as vinyl carbazole and polysilane can be used, but are not limited thereto. The thickness of the charge transport layer is 1 μm
The thickness is arbitrarily set within a range of from 40 to 40 μm, but is preferably from 5 to 30 μm from the viewpoints of uneven coating and generation of pinholes at the time of preparation and photodischarge characteristics, that is, charge transfer speed.

As the fine particles adhered to the photoreceptor 1, polymethyl methacrylate (polymethyl methacrylate) having an average particle diameter of 10 nm to 40 nm is used. These fine particles are previously attached to the surface of the photoconductor 1 at the time of shipment of the apparatus.

On the other hand, the charging device 2 used in the present embodiment
Is a film-type charging device that utilizes discharge in a minute gap with a photoconductor. This charging device 2
As shown in FIG. 3, the charging electrode 3 made of a cylindrical film
2 and the charging electrode 3 while maintaining the shape of the charging electrode 32.
2, an electrode support member 31 for supplying power to the
The main part is constituted by a pressing member 33 which presses against the electrode support member 31 to assist power supply and shape retention, and a power supply 34 for applying a charging voltage to the charging electrode 32.

The charging device 2 has a charging characteristic, that is, an initial charging potential having a positive characteristic with respect to temperature and humidity. At a time of high temperature and high humidity, a charge injection phenomenon to the photoconductor 1 occurs, and The initial charging potential of No. 1 increases.
Also, at low temperature and low humidity, the initial charging potential of the photoconductor 1 decreases.

By combining such a charging device 2 with the photoreceptor 1 whose potential decay rate due to exposure has a positive characteristic with respect to temperature and humidity, as shown in FIG. The curve A of the discharge characteristics and the curve C of the photodischarge characteristics at low temperature and low humidity intersect in the exposure region of ^{3 to 4} mJ / m ² . In the present embodiment, as shown in FIG.
The value error diffusion method is used, and the exposure amount at the quantization level 1 is set so as to be the intersection area shown in FIG. Thereby, even if the environment fluctuates, the surface potential of the photoconductor 1 with respect to the above exposure amount can be stabilized.

The following members are used as members constituting the charging device 2. As the charging electrode 32, any material may be used as long as it has semiconductivity. For example, polyester, polyamide, polyethylene, polycarbonate, polyolefin, polyurethane, polyvinylidene fluoride, polyimide, PEN, PEK, PES,
PPS, PFA, PVdF, ETFE, CTFE and other resins, or synthetic rubber such as silicone rubber, ethylene propylene rubber, butyl rubber, acrylic rubber, urethane rubber and nitrile rubber mixed with conductive powder such as carbon black and metal powder Things can be used.
Also, epichlorohydrin rubber, chloroprene rubber, E
A polar rubber such as PDM rubber or a semiconductive inorganic material such as amorphous silicon may be formed by depositing a thin film or a thick film on an insulating substrate. However, since a polar rubber or the like has a high adhesive force, it is necessary to devise a method of coating the surface with a low-adhesion material or the like. Further, when a thin film or a thick film is deposited, the hardness is high.

[0041] At this time, it is necessary to adjust the mixing amount of the conductive particles such that the preferred volume resistivity, 10 ² Omega
· Spark discharge easily occurs in cm or less, 10 ¹¹ Ω · c
m or more tends to cause dot-like charging failure,
It is desirable to use in the range of 0 ³ Ω · cm to ^{10 10} Ω · cm. In particular, at 10 ³ Ω · cm to 10 ⁶ Ω · cm,
The charging voltage applied to the charger can be set relatively low, and the process speed can be set to 150 mm / sec.
When used in a high-speed machine of c or higher, it is most preferable because potential fluctuation can be suppressed.

As the charging voltage applied to the charging electrode 32, any of a DC voltage and a voltage obtained by superimposing an AC voltage that is twice or more the charging start voltage on the DC voltage can be used. Since the applied voltage increases the surface energy of the surface of the photoconductor and the charging device, and further adversely affects the photoconductor, it is desirable to use a DC voltage. Further, as described above, it is desirable to use a DC constant voltage for the purpose of using the temperature and humidity characteristics of the charging potential and canceling the potential fluctuation in combination with the photodischarge characteristics of the photoconductor.

The surface of the charging electrode 32 is coated with fine powder having high water repellency such as fluorine powder by using polyester, polyamide,
Polyethylene, polycarbonate, polyolefin, polyurethane, polyvinylidene fluoride, polyimide, PE
N, PEK, PES, PPS, PFA, PVdF, ET
Dispersed into resin such as FE or CTFE or synthetic rubber such as silicone rubber, ethylene propylene rubber, butyl rubber, acrylic rubber, urethane rubber, nitrile rubber mixed with conductive powder such as carbon black or metal powder and molded Polymer material to be used. Also, without using the material in which the fine powder is dispersed, on the surface of the charging device formed using the above-described polymer material, a dried solid water-repellent powder, for example, a polymer material such as polyvinylidene fluoride, polymethacrylate, or Zinc stearate, barium stearate, lead stearate, nickel stearate, cobalt stearate, copper stearate, zinc oleate, magnesium oleate, zinc palmitate,
Cobalt palmitate, lead caprylate, lead caproate,
It is also possible to apply a metal salt of a fatty acid such as lead linolenate. In this case, if the particle size of the fine powder exceeds 10 μm, the fine powder is buried in the conductive electrode.
μm or less is desirable, and especially 1 μm or less in consideration of the adhesive force between the charging electrode and the fine powder.

As a method for applying the fine powder, any method can be used as long as the fine powder can be attached to the surface of the charged electrode. For example, sponge, fiber, felt, rubber, nonwoven fabric, foam A mechanical method such as rubbing using a rotating body such as a roll made of a brush, a web, a blade, a paddle, a gel, a resin, or a metal, or a brush-like member that reciprocates, Any method may be used, such as a method of applying and electrically attaching the fine powder, or a combination of both methods. However, depending on the shape of the charging device, it is desirable that the pressure at the contact portion is small, and a brush, felt,
Nonwoven fabric, sponge, etc. are preferably used.

As the shape of the charging electrode 32, a tube made of a flexible film is used. In addition, rubber, a brush, a semiconductive electrode deposited on an insulating roll, a roll using metal or the like, a blade, etc., as long as the shape can contact or approach the photoconductor, A thing may be used. However, since the effect of removing foreign matter increases as the pressing force on the photoreceptor decreases, a film tube having a light contact is particularly preferable.

The electrode support member 31 includes a charging electrode 32
The peripheral surface is formed of a conductive material in order to also supply power to the electrode, for example, a metal such as aluminum or SUS, or a conductive material formed so that the volume resistivity is equal to or less than the volume resistivity of the charging electrode 32. A molecular material or the like is used. Further, in the present embodiment, the electrode support member 31 is fixed and supported, and the charging electrode 32 is driven by the photoconductor 1 by sliding. However, the electrode support member 31 may be rotated in synchronization with the photoconductor 1. The pressing member 33 is pressed by a spring material such as phosphor bronze or a spring to the extent that the charging electrode 32 does not float from the electrode supporting member 31.

As the charging device used in the present invention, in addition to the film type charging device of the present embodiment, any device utilizing discharge in a minute gap with the photoreceptor, such as a BCR, a brush or a magnetic brush, may be used. You can change it.

Next, the developing device 4 used in this embodiment
Will be described. FIG. 4A is a schematic diagram showing the structure of the developing device 4, which is disclosed in Japanese Patent Application No. 8-40380.
The developing device of the present invention is applied. FIG.
FIG. 2B is a partial configuration diagram illustrating a developing roll 41 used in the developing device. The developing device 4 is provided with an opening for development at a portion of the developing housing 42 in which the developer is accommodated and facing the photoreceptor 1.
, And two screw augers 44 and 45 are provided at the rear thereof. Further, a scraper 43 for removing the developer adhered to the developing roll 41 is provided so as to come into contact with the developing roll 41.

The screw augers 44 and 45 are provided inside two developer stirring and transporting chambers 47 and 48 partitioned by a partition wall 96 in the developing housing, and rotate so as to transport the developer in opposite directions. It is driven. The two developer stirring / transporting chambers 47 and 48 communicate with each other at both ends, and the developer conveyed by the screw augers 44 and 45 is circulated and moved in the two developer stirring / transporting chambers while being stirred. Has become

As shown in FIG. 4B, the developing roll 41 has a cylindrical conductive base 41a supported so as to be rotatable around an axis, and a magnetic roller formed on the peripheral surface thereof. The main part is constituted by the recording layer 41b. The developing roll 41 has a certain gap with the photoconductor 1, and is held so that the developer layer is not in contact with the photoconductor 1.

The magnetic recording layer 41b is formed by dispersing a ferromagnetic material in a binder resin. As a magnetic material,
Any known material such as a magnet material or a magnetic recording material can be used. For example, γ-Fe ₂ O ₃ or CrO ₂ can be used. As the binder resin, any resin known as a resin constituting a magnetic recording material such as a tape, a disk or a card can be used, and for example, polycarbonate, polyester, polyurethane and the like can be used. Further, conductive fine particles and the like can be added to the magnetic recording layer 41b as needed.

In the magnetic recording layer 41b, as shown in FIG. 4B, S poles and N poles are alternately arranged at minute intervals in the circumferential direction. The distance between adjacent north and south poles is 25 μm
As described above, the thickness is set to 250 μm or less, and the two-component developer containing the toner and the magnetic carrier is almost uniformly adsorbed on the peripheral surface. Then, the two-component developer is transported by the rotation of the developing roll 41, a developing bias voltage is applied to the developing roll, and the electrostatic latent image on the photoconductor 1 is developed with toner.

On the other hand, as an improvement, a configuration in which a plurality of magnetic poles are arranged in a substantially constant pattern on the magnetic recording layer may be used.
For example, a pattern composed of a pair of adjacent north and south poles and a low magnetic force region or a non-magnetized region provided outside the pair of magnetic poles is preferable. At this time, a pair of adjacent N poles and S
The distance between the magnetic poles is set to 25 μm or more and 250 μm or less, and the distance between adjacent magnetic poles across the low magnetic force region or the non-magnetized region is set to 300 μm or less. For example, magnetic poles adjacent to each other across the low magnetic force region or the non-magnetized region may be magnetic poles having different polarities or magnetic poles having the same polarity.

The developing device 4 includes a developing roll 41
However, a small amount of the developer is held on the peripheral surface in a thin layer by the above-described minute gap magnetization and the low magnetic force effect, and the developing roller itself having the magnetic force rotates to convey the developer. Accordingly, since the magnetic tumbling which is observed in the developer transport including the magnetic roll and the developing sleeve is not used as in the related art, the transport amount of the developer is substantially constant, and the toner amount to be developed is saturated. . This allows
As shown in FIG. 6, the development gamma (gradient of the curve representing the relationship between the development potential and the development weight) tends to be higher than that of the conventional development device, and the development toner weight is relatively low in the region where the development contrast potential is relatively low. Saturates. In the present embodiment, a three-valued error diffusion method is used as shown in FIG. 7, and the exposure amount at the quantization level 2 (maximum value) is set to an exposure amount such that it becomes a saturated region of the developing toner weight. Is set.

In the recording apparatus as described above, in the combination of the photoconductor 1 and the charging device 2, a ternary error diffusion method is used near the intersection of the photodischarge characteristic curves of the photoconductor 1 when the temperature and humidity environment fluctuates. In FIG. 7, the exposure amount of one quantization level is selected, and as shown in FIG. 7 described above, a recording device having no environment dependency is realized by the offset effect of the environmental characteristics of the photoconductor 1 and the charging device 2. can do. Further, by using this combination in a cleaner-less system, the size of the apparatus can be reduced. Also, the developing device 4
By performing the image formation in combination with the above, it is possible to realize a recording apparatus in which the fluctuation of the image density is further reduced by utilizing the saturation characteristic of the developing device 4.

Although the developing device 4 is an example of a two-component developer, it is known that the same characteristics as in FIG. 6 can be obtained even with a non-magnetic one-component developing device. By the combination of the photoreceptor 1 and the charging device 2 according to the present invention, stable image formation can be performed.

In this embodiment, the case where both the temperature and the humidity are changed has been described. However, even when only the temperature or the humidity alone is changed, the offset effect of the environmental characteristics intended by the present invention can be realized. Thus, an image recording apparatus that does not depend on the environment can be realized.

[0058]

Embodiments of the present invention will be described below with reference to the drawings. <First Embodiment> FIG. 8 is a schematic diagram showing an embodiment of a recording apparatus according to the present invention. This recording device, like the recording device shown in FIG.
Image writing device 53, developing device 54, transfer roll 55,
It has a static eliminator 57 and the like.

(Photoreceptor) In FIG. 8, the photoreceptor 51 has the above-described laminated structure shown in FIG. 2, and is specifically produced by the following method. 20 parts by weight of acetylacetone zirconium butoxide (Orgatics ZC540, manufactured by Matsumoto Kosho) 2 parts by weight of γ-aminopropyltriethoxysilane (A1100 manufactured by Nippon Unica Ltd.) 1.5 parts by weight of polyvinyl butyral resin (ESLEC BM-S Sekisui Chemical 70 parts by weight of n-butyl alcohol A solution composed of the above components was dip-coated on a SUS pipe having a diameter of 15 mm, and then dried at 150 ° C. for 10 minutes.
An undercoat layer having a thickness of 0.9 μm was formed.

X-type metal-free phthalocyanine 5 parts by weight Vinyl chloride-vinyl acetate copolymer 5 parts by weight (VMCH, manufactured by Union Carbide Co., Ltd.) 200 parts by weight of n-butyl acetate Next, a sand mill using the above components with 1 mmφ glass beads The dispersion obtained by dispersion for 2 hours was dip-coated on the undercoat layer and dried at 100 ° C. for 10 minutes to form a 0.2 μm-thick charge generation layer.

The compound represented by the structural formula (1) 1 part by weight The binder resin represented by the structural formula (2) 1 part by weight Monochlorobenzene 6 parts by weight

[0062]

Embedded image

[0063]

Embedded image

Next, a solution comprising the above components was applied onto the charge generation layer by dip coating, and then dried at 135 ° C. for 1 hour to form a charge transport layer having a thickness of 24 μm. 51 were produced.

(Charging Device) As the charging device 52, a film charging device having the following configuration was prepared. In the embodiment shown in FIG. 8, conductive carbon black is dispersed as the charging electrode 62, and the volume efficiency is 10 ³ Ω · cm to 10 ³ Ω · cm.
⁶ Ω · cm, diameter 12.5mm, thickness 100μm
Was used. Then, 100 parts of polytetrafluoroethylene and 5 parts of conductive carbon added thereto were mixed and dispersed with 100 parts of an appropriate mixed solvent to prepare a coating material for forming a surface layer. It was applied to the surface of the charging electrode 62 so as to have a dry film thickness of 10 μm by using Bark Industry Co., Ltd.). The electrode support member 63 is made of SU having a diameter of 10 mm.
An S-roll was used, and a setting was made so that a DC voltage of 1 kV required for charging was applied to the electrode support member 63 using a power supply (not shown). On the other hand, as the pressing member 64, a polyacetal resin roll having a diameter of 5 mm was used, and phosphor bronze having a plate thickness of 1 mm was used as a spring material.

(Developing Apparatus) The developing apparatus 54 has a structure shown in FIG.
Using the developing roll shown in FIG.
b using γ-Fe ₂ O ₃ as a magnetic material and polyurethane as a binder resin, and forming a 50 μm layer on the conductive substrate 41a.
m of the magnetic recording layer 41b was formed. A magnetic recording head was used to magnetize the magnetic recording layer 41b. The direction of magnetization is
As shown in FIG. 4 (b), it was set horizontally on the surface of the cylindrical carrier 41, and the magnetic pole interval was set to about 100 μm. The outer diameter of the developing roll 71 is set to 8 mm, the peripheral speed during driving is set to 320 mm / s, and the gap between the photoconductor 51 and the developing roll 71 is set to 300 μm. And is held in a non-contact state.
A developer supply roller 73 is provided behind the development roller 71.
Are arranged to stir the developer, and the developing roll 7
1 is supplied with the developer.

(Toner) The toner contained in the developing device 54 is prepared as follows. Polyester (number average molecular weight: 4,300, weight average molecular weight: 9.8
(00, Tg = 58 ° C.) 94 wt% and carbon black 6 wt% were kneaded and pulverized to obtain colored particles having an average particle diameter of 7 μm. Average particle size is Coulter counter (Coulter)
It is the value measured in. An average particle size of 4
Titanium oxide fine particles of 0 nm were externally added at a ratio of 30% of the toner surface area to obtain a black toner. The charging polarity is negative.

(Carrier) The carrier housed in the developing device 54 is prepared as follows. Styrene-
Acrylic copolymer (number average molecular weight: 23,000, weight average molecular weight: 98,000, Tg = 78 ° C) 30 wt
%, Carbon black (basic carbon black: pH
= 8.5) 3 wt%, granular magnetite (maximum magnetization 80
(emu / g, particle size: 0.5 μm) 67% by weight was kneaded, pulverized, and classified to produce a carrier having an average particle size of 45 μm.
The specific gravity of the carrier was 2.2. The average particle size is a value measured by Microtrac (manufactured by Nikkiso Co., Ltd.). The charging polarity is positive. The electric resistance was 10 ¹² Ω · cm.

(Developer) The toner and the carrier were mixed to obtain a developer. The toner concentration in the developer at this time (TC: Toner Concentration)
Is 15 wt%, and the value of the toner charge amount in the developer is 20 μC
/ G. TC was determined as follows. This developer was loaded into the developing device 54. Below margin

(Equation 1)

(Addition of Fine Particles) As the fine particles adhered to the photoreceptor 51, polymethyl methacrylate (polymethyl methacrylate) fine particles were used. Then, fine particles are applied to the surface of the photoconductor 51 in advance at the time of shipping the apparatus, and are further mixed into the developer as an external additive. This makes it possible to replenish the shortage of fine particles over time. The average particle size of the polymethyl methacrylate fine particles used was 10 nm to 40 nm.

(Image Recording Conditions) ROS: LED (600 dpi), Process Speed: 100 mm / s Charging Voltage: Approx.-400 V (Input Voltage to Film Electrode is Fixed at 1.0 kV) Developing Bias: DC Component = −350 V AC Component = 2kV _PP (2kHz) Transfer condition: BTR transfer

(Multi-Valued Error Diffusion Method) FIG. 9 shows a pixel tile of interest in error diffusion and an error diffusion coefficient. In the present embodiment, 256 gradations from 0 to 255 are set to 0, 128, 256 to 3
The value level was developed using the error diffusion method.

(Environmental conditions and experimental results) High temperature and high humidity conditions: 28 ° C, 85% RH, normal conditions: 22 ° C, 5%
The conditions were 5% RH, low temperature and low humidity conditions of 10 ° C. and 30% RH. When the installation environment of the apparatus was changed to three conditions of high temperature and high humidity, usually low temperature and low humidity for every 10,000 sheets, the photoreceptor hardly worn down to 100,000 sheets, and even in each environment, A good image could be obtained.

<Second Embodiment> FIG. 10 is a schematic structural view showing a second embodiment of the recording apparatus of the present invention. This recording apparatus is an apparatus in which the above-described recording units shown in FIG. 8 are arranged in quadruple tandem such that the center position of each photoconductor 81 is at an interval of 25 to 50 mm as shown in FIG.
In this device, from the upstream side in the process direction,
Developing devices 84K, 84Y, 84M, and 84C corresponding to each color of black, yellow, magenta, and cyan are arranged. The BTR 87 disposed below the photoconductor 81
Thereby, the toner images are sequentially transferred to the recording paper conveyed on the recording paper conveying belt 92, and a color image is formed. Finally, the toner on the recording paper is fixed by a fixing device (not shown).

In such a printing apparatus, the above-described printing unit shown in FIG. 8 is reduced in size, so that a small-sized color printer unprecedented in the related art can be realized.
Furthermore, when an environmental experiment similar to that of the first embodiment was performed, a good output image with almost no difference was obtained under each experimental condition.

[0076]

As described above, according to the present invention,
It is possible to obtain a stable image in any environment without being affected by the temperature and humidity of the environment without requiring expensive potential control means, and to realize a high-quality, low-cost, small-sized recording apparatus. Further, by adopting a cleaner-less system for applying fine particles to the surface of the photoreceptor, it is possible to realize a smaller recording apparatus. Further, since the potential control cycle becomes unnecessary, the productivity of the recorded image can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a recording apparatus according to an embodiment of the invention.

FIG. 2 is a schematic diagram illustrating a layer configuration of a photoconductor used in the recording apparatus.

FIG. 3 is a schematic configuration diagram showing a charging device used in the recording apparatus.

FIG. 4 is a schematic configuration diagram illustrating a developing device used in the recording apparatus, and a schematic cross-sectional view illustrating a developing roll of the developing device.

FIG. 5 is a diagram illustrating the temperature and humidity dependence of initial charging and photodischarge characteristics of a photoconductor in the recording apparatus of the present invention.

FIG. 6 is a diagram illustrating a relationship between a development contrast potential, which is a development characteristic of the development device of the present invention, and a development toner weight.

FIG. 7 is a diagram illustrating image reproducibility in the multi-level error diffusion method of the present invention.

FIG. 8 is a schematic configuration diagram showing a first embodiment of the recording apparatus of the present invention.

9 is a diagram illustrating a multi-level error diffusion method in the printing apparatus shown in FIG.

FIG. 10 is a schematic configuration diagram showing a second embodiment of the recording apparatus of the present invention.

FIG. 11 is a schematic configuration diagram illustrating an example of a conventional recording apparatus.

FIG. 12 is a diagram showing the temperature and humidity dependence of photodischarge characteristics of a photoconductor in a conventional recording apparatus.

FIG. 13 is a schematic configuration diagram showing another example of a conventional recording apparatus.

[Explanation of symbols]

 1, 51, 81... Photoreceptor, 2, 52, 82... Charging device, 3, 53... Image writing device, 4, 54. ..., transfer roll, 6, 56, 88 ... recording paper, 7, 67 ... static eliminator, 32, 62 ... charging electrode, 33, 63 ... ... Electrode support member, 34,64 ... Pressing member, 41,71 ... Developing roll, 42,72 ... Housing, 43 ... Scraper, 44,45 ····· Screw auger, 46 ··· Partition wall, 47, 48 ··· Developer agitation transport chamber, 73 ··· Developer supply roll, 87 ··· BTR

Claims (4)

[Claims] 1. A photoreceptor on which a latent image is formed on the surface due to a difference in electrostatic potential, a charging means for uniformly applying a charge to the photoreceptor, and an exposure for exposing the photoreceptor in accordance with an image signal Means, and a developing device for developing an exposed area of the photoconductor by toner adhesion, the electrophotographic recording apparatus, wherein the photoconductor has a photodischarge characteristic, that is, a potential decay rate due to exposure to temperature and humidity. The charging unit has a positive characteristic with respect to charging characteristics, that is, an initial charging potential with respect to temperature and humidity. An area where the photodischarge characteristic curve of the photoconductor crosses when the environment changes is provided, and the exposure amount of at least one light amount level at the time of outputting a halftone density is determined by the exposure area. Recording apparatus characterized by being set in the exposure amount in. 2. The developing means according to claim 1, wherein said developing means is a high developing potential contrast portion which is a potential difference between a DC component of a developing bias potential and a potential of an exposed portion of said electrostatic latent image. 2. The recording apparatus according to claim 1, wherein the recording apparatus has a developing characteristic having a saturation region where a developing toner amount hardly increases. 3. The recording apparatus according to claim 1, wherein fine particles having an average particle diameter smaller than that of the toner are provided on the surface of the photoconductor. 4. The charging device according to claim 1, wherein the charging unit is arranged so as to approach or contact the photoconductor, and a voltage applied to the charging unit for charging the photoconductor is controlled by a constant voltage. The recording device according to claim 1, wherein the recording device is a recording device.