JPH09222779A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide, in the case, a photoreceptor having a High-γ characteristic is used in an electrophotographic process, the stability of the characteristic of the repeated electrification and the stability of residual potential by providing a preprocessing means which, before image formation, simultaneously emits light to the photoreceptor under the action of an electric field having the same polarity as the photoreceptor. SOLUTION: This device uses the photoreceptor 1 having a potential attenuation characteristic in which the potential VP of the uniformly electrified surface is suddenly attenuated having a certain amount of exposure, A0, as its boundary and is provided with the preprocessing means 2 which, before the image formation, emits light simultaneously to the photoreceptor 1 under the action of the electric field having the same polarity as the photoreceptor 1. Because the preprocessing means 2 cause the electric field having the same polarity as the photoreceptor 1 to act before the image formation, the electric field acts on the photoreceptor 1, as an external electric field, so that the photoreceptor 1 is brought into a state equivalent to an electrified state. In this state, the preprocessing means 2 emits light simultaneously, therefore a large number of ion pairs by light excitation are generated and trap in the photoreceptor 1 is opened. As a result, the movement of charges which offsets the electrification potential occurs, and the residual potential of the photoreceptor 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 image forming apparatus such as a copying machine, an electrostatic recording apparatus, a facsimile, a transmission apparatus and a laser printer, which forms an image on a photosensitive member by using an electrophotographic method, and more particularly, The present invention relates to improvement of an image forming apparatus of a type using a photoconductor having a so-called High-γ characteristic.

[0002]

2. Description of the Related Art Electrophotographic technology is currently used as an image forming apparatus for plain paper copying machines, laser printers, facsimiles, etc., because of its features such as rapid image forming speed, dry development, and high recording density. It has been put to practical use. The electrophotographic process is composed of the basic processes of charging, exposing, developing, transferring, fixing and cleaning, and the photoconductor is an important part responsible for latent image formation by charging and exposing.

The characteristics required of the electrophotographic photoreceptor are chargeability, photoconductivity, and the like, which are the dominant factors for latent image formation in the electrophotographic process. Image formation in electrophotography is achieved by uniformly charging and selectively eliminating the charge on the photoreceptor surface by light irradiation.

Typical electrophotographic photoreceptors which have been put into practical use until now are roughly classified into amorphous chalcogenide materials containing amorphous selenium and its alloys, II-IV group inorganic compound materials such as zinc oxide and cadmium sulfide, and Organic photoconductor (OPC) such as resin dispersion system of molecules and low molecular weight organic compounds,
Amorphous silicon materials can be used. 1970
Until the 1960s, photoconductors were monopolized by inorganic materials, but in 197
With the advent of OPC from the first half of the year, electrophotographic photoconductors have reached a major turning point, and most of the conventional inorganic photoconductors are OP.
It started to move in the direction of replacing C. Since the characteristic of this OPC is that it is easy to design the spectral sensitivity, it has attracted more attention with the advent of laser printers. That is, since the mainstream of the recording light source is a semiconductor laser, the photoconductor has excellent monochromatic light sensitivity of 780 mm.

Explain why this factor is important.
Conventionally, electrophotographic technology has been put into practical use only as a plain paper copying machine using an analog optical system as a light source. But 19
In the 1980s, this technology began to be actively applied as a computer output device. In addition to this, the digitization and colorization of plain paper has come to the forefront. Since these systems use digital optics,
The photoreceptor is required to have sufficient sensitivity corresponding to the light source used in this system. That is, it is important to have sufficient sensitivity to monochromatic light of a specific wavelength. In particular, a semiconductor laser is often used as a light source for digital use, and most of them are 700 to 9 that are inexpensive and excellent in mass productivity.
Photoconductors having a large sensitivity to monochromatic light having a peak in the range of 00 nm have been developed. As a result, OPC has come to be widely used as a photoconductor for an electrophotographic system using a digital optical system.

The OPC currently in the mainstream is a laminated OPC comprising a charge transport layer in which a charge transport material is dissolved in a resin in a high concentration and a charge generation layer in which a charge generating pigment is dispersed in a resin in a high concentration. is there. In this type of OPC, the photoconductive basic function of the photoreceptor is divided and independent, and the selection of materials is expanded, and as a result, the performance of the photoreceptor is dramatically improved. In particular, organic photoreceptors using phthalocyanine pigments such as metal-free phthalocyanine, copper phthalocyanine, titanyl phthalocyanine, magnesium phthalocyanine, and vanadyl phthalocyanine are known to be suitable for digital applications.

However, a major problem with this laminated OPC is that the charging characteristic is negative charging. Negatively charged OP
C has a problem that a large amount of ozone is generated from the system used. For this reason, positively charged OPCs are also described in, for example, “T. NakagaWa et al, Japan Hardcopy′88 l. Ozawa.
et al, Japan Hardcopy '88 etc. "
It was put to practical use as an OPC for ordinary copying machines in the latter half of the 1980s.

Further, studies on positively charged single layer type OPC have been made, and those having new characteristics are described in, for example, "S. Johnson et a.
l., IS & T ′s Seventh International congress on Adva
nces in Non-impact Printing Technologies, '91 S.
Tsuchiya et al., Ibit, '91 ”.
These are both photoconductors in which a pigment is dispersed in a resin without a charge transporting agent in the photosensitive layer. Therefore, the price is lower than that of the conventional laminated type in terms of layer formation. Further, the most characteristic of these is that they are positively charged. Furthermore,
Another major feature of these photoconductors is High-γ
The characteristics can be mentioned. The High-γ characteristic means that the slope of the linear potential decay portion in the potential decay curve of the photoconductor is large, and it is proposed that this characteristic is particularly advantageous for digital image formation.

Conventionally, the light energy distribution of spot light used for dot exposure is a Gaussian distribution with a skirt length. If dot exposure with this hem length energy distribution is applied to the photoconductor where the potential decay starts according to the amount of incident light to form an image, the hem length dot exposure will be reproduced as it is, and blurring will occur around the dots. Occurs, and a dot image with poor resolution is formed. Therefore,
For example, Japanese Patent Application Laid-Open No. 1-169454 proposes a so-called High-γ photoconductor that shows almost no potential attenuation during weak exposure and shows steep potential attenuation characteristics when the amount of light increases and reaches a certain amount of light. The above-mentioned publication describes that even if the dot exposure has a Gaussian distribution with a hem length, a sharp dot-shaped latent image is formed.

Further, the phenomenon that the High-γ characteristic appears in the single layer type OPC has been known as an induction effect from before. As shown in FIG. 19, the induction effect is a phenomenon in which there is a time delay until the potential decays after the photosensitive member is irradiated with light, and is a characteristic peculiar to the resin dispersion type photosensitive member. This phenomenon does not contribute much to potential decay because generated carriers are trapped in traps at the beginning of exposure, but traps are filled up as the number of generated carriers increases thereafter, and carrier transport rapidly occurs and large potential decay occurs. It is presumed that this occurs. As a result, a high gamma value is exhibited. In the past, the induction effect was considered unsuitable when trying to obtain a linear photosensitivity, so there was a development to reduce the induction effect, but recently, as mentioned above, Induction effect (the point that the decay process of the surface potential when the photoreceptor is charged and exposed is gradually attenuated with the increase of the exposure amount, but shows a rapid potential decrease as the exposure amount is gradually increased). There has been a movement to actively use and form images by digital methods (binarization).

[0011]

However, such a single-layer type photoconductor is inferior in stability of repetitive charging characteristics and stability of residual potential to the conventional multi-layer type photoconductor. Was found. It is believed that this factor is due to a large amount of traps existing in the photosensitive layer, which causes the behavior of the High-γ characteristic of the single-layer type photoreceptor. That is, this trap changes due to the influence of the transfer electric field depending on the presence / absence of an image / presence / absence of paper in the previous process, and
It is presumed that the history of previous image formation has an influence on the next image formation because it changes momentarily due to thermal excitation.

Therefore, a conventional image forming history eliminating technique (a technique of providing an auxiliary process of, for example, photo-erasing (erase) or pre-charging and a combination thereof before obtaining a desired charge in order to ensure stability in a photoconductor) is used. When I applied it, Hig
A sufficient effect of eliminating the image formation history could not be obtained for the single-layer type photoreceptor having the h-γ characteristic.

For example, as a photo-electrification method, in order to prevent the surface potential of the photosensitive member from sequentially increasing every time the image forming process is repeated, pre-exposure with light of 450 nm or less is performed to eliminate the charge on the surface of the photosensitive member. It is proposed that the hole traps in the photosensitive layer are recombined with each other to make the vicinity of the surface layer neutral or negative (see, for example, JP-A-57-129456). . However, this prior art is intended for an image forming apparatus using a laminated type photoreceptor, and even if it is directly applied to an image forming apparatus using a single layer type photoreceptor, the above-mentioned image forming history is eliminated. It was virtually impossible to do.

As a pre-charging method, before image formation,
A technique has also been proposed in which the photoconductor is once charged with a pre-charging corotron or the like, and then is neutralized with light to uniformly neutralize the surface potential of the photoconductor (for example, JP-A-62-150).
377, JP-A-62-240978, JP-A-2-2
97575, JP-A-7-28287). However, when this method is applied to a single-layer type photoconductor having a High-γ characteristic, the single-layer type photoconductor having a High-γ characteristic has a time delay until the potential is attenuated after exposure. However, it is not preferable in that the time from static elimination to main charging at the time of image formation must be sufficiently secured, and the apparatus becomes large by that amount.

The present invention has been made in order to solve the above technical problems, and it is possible to improve the stability of repetitive charging characteristics when a photoreceptor having a High-γ characteristic is applied to an electrophotographic process. An object of the present invention is to provide an image forming apparatus capable of ensuring stability of residual potential.

[0016]

That is, the present invention provides:
As shown in FIG. 1, in an image forming apparatus for forming an image by an electrophotographic method using a photoconductor 1 having a potential attenuation characteristic that abruptly attenuates with a certain exposure amount A0 having a uniformly charged surface potential VP. It is characterized in that a pretreatment means 2 is provided for simultaneously irradiating the photoconductor 1 with light under the action of an electric field of the same polarity as that of the photoconductor 1 before image formation.

In such a technical means, the photoreceptor 1
As for, as long as it has a potential attenuation characteristic that abruptly attenuates the potential at a certain exposure amount A0, it is applicable, for example, a single layer type organic photoconductor made of X-type metal-free phthalocyanine and a binder resin. Can be mentioned. Also, the form of the photoreceptor 1 may be a drum shape or a belt shape.
Further, the electrophotographic method may be one that includes at least each step of charging, exposure, development, transfer, fixing, and cleaning, and a dedicated device may be provided for each step. It may be performed by one device, or may be shared in part, such as a structure in which the cleaning unit is not provided and the residual toner is collected by the developing unit. Further, the toner image on the photoconductor 1 may be directly transferred to the recording medium, or the toner image on the photoconductor 1 may be primarily transferred to the intermediate transfer member and then secondarily transferred to the recording medium. Also includes things.

The pretreatment means 2 is at least the photoreceptor 1.
A light irradiating means for irradiating light with respect to The wavelength range of light irradiation of the light irradiation means may be 500 to 800 nm, and in view of the depth of light penetration into the photosensitive layer, it preferably has a peak wavelength similar to image exposure. is there.

Further, the form of the pretreatment means 2 is roughly classified into a non-contact type and a contact type. As the non-contact method, a light irradiating unit that irradiates the photoconductor 1 with light, and a transparent conductive member that is disposed between the light irradiating unit and the photoconductor 1 in proximity to the photoconductor 1 in a non-contact manner And a voltage applying means for applying a voltage to the conductive member, which has an advantage of not damaging the photoreceptor.

Here, the conductive member may be appropriately selected as long as it is transparent and can transmit the light from the light irradiating means. For example, in the non-contact system, the plate member is mesh-shaped. A screen (corresponding to a grid) provided with the above openings may be used, or a transparent conductive film may be provided on a transparent material such as glass or film, and the selection may be made appropriately. In addition, as the conductive member, a dedicated member may be usually used. However, for example, when a charging device using a grid is used as a charging device, a part of the grid is extended and There is no problem even if the conductive member is also used.

In the non-contact method, the distance between the conductive member and the photosensitive member 1 is preferably as close as possible, and is about 0.5 mm to 1.5 mm. Further, the voltage applying means may be appropriately selected as long as it has the same polarity as the photosensitive member 1 and applies a DC voltage within the withstand voltage range of the photosensitive member 1. For example, in the non-contact system, the distance between the conductive member and the photosensitive member 1 is d, the voltage applied to the conductive member is VA, the conductive member and the photosensitive member 1 are
If the electric field between and is E and the breakdown voltage of the photoconductor 1 is considered,
3 (kV / mm) ≧ E = VA / d.

On the other hand, as the contact method, light irradiation means for irradiating the photoconductor 1 with light, and the light irradiation means and the photoconductor 1 are used.
With a transparent conductive member disposed in contact with the photoconductor 1 and a voltage applying means for applying a voltage to the conductive member, or a conductive state disposed in contact with the photoconductor 1. A mode in which a conductive roll, a voltage applying means for applying a voltage to the conductive roll, and a light irradiating means for irradiating the conductive roll with light in the vicinity of the contact portion of the photosensitive member 1 are mentioned, and the action of the electric field is facilitated. It has the advantage that it can be realized.

Here, the conductive member in the contact system may be appropriately selected as long as it is transparent and can transmit the light from the light irradiating means, but it does not damage the photoconductor 1 ( Flexible film, ring-shaped conductive cylindrical member, etc.) must be selected. Also,
As the conductive roll, a dedicated part may be usually used. For example, in a type using a charging roll as a charging device, this charging roll may be used also as a conductive roll. . Further, the voltage applying means may be appropriately selected as long as it has the same polarity as the photosensitive member 1 and applies a DC voltage within the withstand voltage range of the photosensitive member 1.

There are some prior arts in which a voltage applying means is added to the light removing means, but none of them are related to the pretreatment means 2 of the present invention. deep. In Japanese Patent Laid-Open No. 6-161337, a charge eliminating lamp is provided in a case having an opening facing the surface of the photosensitive drum, the opening of the case is covered with a conductive mesh member, and the mesh member is filled with toner. A bias voltage of the same polarity has been proposed. However, the “mesh member to which the bias voltage is applied” is a functional member that prevents the toner from adhering to the charge eliminating lamp while ensuring the optical path, and is not a functional means that applies an electric field to the photoconductor 1. I can't say
It does not correspond to the “pretreatment means 2” of the present invention.

Further, in Japanese Patent Laid-Open No. 63-144382, a photo-erasing means is provided on the photoconductive layer side of a photoconductor belt of the optical backside recording system, and the photoerasing means is opposed to the photoconductor belt. It has been proposed that a conductive roller to which a bias voltage having a polarity opposite to that of the photosensitive belt is applied is provided at the portion. However, this prior art is intended for a special image forming apparatus that adopts the optical backside recording method, and is completely targeted for the present invention (electrophotographic image forming apparatus using a photoconductor having a High-γ characteristic). Since they are different, the above prior art cannot be applied to the present invention as it is. Further, the "conductive roller to which a bias voltage is applied" is a functional member that applies a force from the surface of the photoconductor to the conductive layer side with respect to the latent image charge confined by the charge of the residual toner. Since the polarity is opposite to the polarity of the photoconductor, it cannot be said to be a functional means for applying an electric field having the same polarity as that of the photoconductor, and therefore does not correspond to the “pretreatment means 2” of the present invention.

According to the above-mentioned technical means, in the case of the photoconductor 1 having the potential attenuation characteristic that the potential is rapidly attenuated at a certain exposure amount A0, when the photoconductor 1 is charged and irradiated with light, it is photoexcited. The generated ion pair is generated, and there is a charge transfer that cancels the charging potential. On the other hand, when the photoconductor 1 is irradiated with light without being charged, the photoexcited ion pair is immediately bound and stabilized, so that no charge transfer occurs. Since the pretreatment unit 2 according to the present invention applies an electric field having the same polarity as that of the photoconductor 1 before image formation, the electric field acts on the photoconductor 1 as an external electric field and the photoconductor 1 corresponds to a charged state. become. In this state, since the pretreatment unit 2 simultaneously irradiates light, a large number of photoexcited ion pairs are generated, and the number of opportunities for opening the trap inside the photoconductor 1 is increased, so that the trap can be opened or made uniform. To be For this reason, a charge transfer phenomenon that cancels the charging potential occurs, and the residual potential of the photoconductor 1 is effectively removed. In this way, the light irradiation and the external electric field work effectively, and the same effect as that of the charging exposure is exerted and the photoconductor 1 is discharged.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail based on the embodiments shown in the accompanying drawings. First Embodiment FIG. 2 shows a first embodiment of an image forming apparatus to which the present invention is applied. In the figure, reference numeral 11 is a single-layer organic photoconductor having a potential attenuation characteristic (High-γ characteristic) that abruptly attenuates the potential at a certain exposure amount, 12 is a charging device for charging the photoconductor 11, and 13 is a charging device. An optical writing device that irradiates light onto the photosensitive body 11 thus formed to form an electrostatic latent image (in the present embodiment, a negative latent image for image exposure), for example, laser light generation including a semiconductor laser and a polygon mirror. Vessels are used. Further, reference numeral 14 is a developing device that visualizes the electrostatic latent image formed on the photoconductor 11 with toner having the same polarity charge as that of the photoconductor 11, and 15 is a toner image on the photoconductor 11. A transfer device such as a corotron that transfers the recording paper 16 to the recording paper 16, a paper peeling device 17 such as a corotron that peels the recording paper 16 electrostatically attracted to the photoconductor 11, and a recording paper 1
A fixing device for fixing the unfixed toner image on 6 is a cleaner for removing residues such as residual toner on the photoconductor 11, and a destaticizing device for removing residual charges on the photoconductor 11.

In the present embodiment, the photoreceptor 11 is a single-layer type organic photoreceptor in which X-type metal-free phthalocyanine is dispersed in a binder resin. Specifically, X
A positively charged single-layer type photoconductor was prepared by using a type metal-free phthalocyanine (manufactured by Dainippon Ink and Chemicals, Inc.) and Fastgen Blue as a photosensitive material. The details of the photoreceptor have already been disclosed in JP-A-3-287171. Further, in the present embodiment, the photosensitive member was manufactured in a drum shape using an aluminum drum main body. In the single-layer type photoconductor 11 configured as described above, since the main body of charge transfer is holes, the surface is positively charged before use.

The potential attenuation characteristics of the resin-dispersed single-layer type photosensitive member 11 are shown in FIGS. 3 (a) and 3 (b). The solid line in FIG. 3A shows the light attenuation characteristic of the resin-dispersed single-layer type photoconductor 11, and when light is irradiated after charging, the light attenuation process due to the exposure amount of the surface potential is gradually gradual at first. Attenuation is shown, and when the light quantity is further increased, the surface potential is rapidly attenuated during the gentle attenuation. On the other hand, FIG.
The solid line indicates the dark decay characteristics of the resin-dispersed single-layer type photoconductor 11, and the change with time after being charged to a predetermined potential shows a gentle decay at first, and then shows a rapid decay with the passage of time. The curve is such that the potential drops.

Here, the light-dark attenuation characteristic of the conventional laminated type photoreceptor (shown by dotted lines in FIGS. 3A and 3B) and the light-dark attenuation characteristic of the resin dispersion single layer type photoreceptor 11 used in the present embodiment. Compare with. Since the surface potential of the laminated type photoreceptor is negatively charged and the resin-dispersed single-layered type photoreceptor 11 is positively charged, the potential as an absolute value is used in the laminated type photoreceptor of FIG. . As can be seen from FIG. 3, the sensitivity characteristics of the conventional laminated photoreceptor are such that the sensitivity region relatively reacts to the irradiation light over the entire region, whereas the single layer photoreceptor according to the present embodiment has a certain irradiation characteristic. It is understood that the surface potential attenuates gently even after exposure to the light amount, and the surface potential abruptly attenuates when the light amount increases after a certain irradiation light amount.

The photosensitive member having the above-described sensitivity characteristics in which the light attenuation characteristic and the dark attenuation characteristic change on and off with an inflection point in an S-shaped curve is a single-layer type in which zinc oxide is dispersed in a resin. Photoreceptors and organic photoreceptors in which phthalocyanine is resin-dispersed have also been reported, but the photoreceptor surface potential at the time of exposure has a long relaxation time at which it begins to decay, or many charges required for charging are required, The changes in the potential holding performance and the sensitivity during repeated use were large, and were not suitable for practical use. Therefore, in the present embodiment, a single-layer type photoconductor in which an X-type non-metallic phthalocyanine is dispersed in a resin is used as a type which overcomes these problems and has a sensitivity characteristic at a practical level.

Further, in the present embodiment, the charging device 1
As shown in FIGS. 2 and 4, No. 2 has a scorotron configuration using a grid, a DC voltage of 5.0 kV is applied to the corotron wire 21, and 300 to 700 V is applied to the shield 22 and the grid 23. Was applied so that the surface potential of the photoconductor 11 was charged to 300 to 700V.

Further, in the present embodiment, the static eliminator 2
Reference numeral 0 is composed of a light eliminating lamp 31 and a screen 32 provided between the photoconductor 11 and the conductive member as a conductive member. The static elimination lamp 31 is composed of a tongue lamp, is squeezed to a wavelength of 500 nm to 800 nm through a filter, and irradiates light having a light amount of about 5 to 10 times that lowers the surface potential of the photoconductor 11 to the residual potential. It is a thing. The screen 32 is 0.1 mm
It is made of a stainless steel plate material having a thickness of 80 to 90% in the form of a mesh and is placed 1 mm away from the photoconductor 11. A bias power source 33 is connected to the screen 32, and in the present embodiment,
Bias voltage of the same polarity as the photoconductor 11 is 500 to 2000
It is applied within the V range.

Next, an image forming process of the image forming apparatus according to this embodiment will be described. In the present embodiment, when the drum-shaped photoconductor 11 starts rotating, the charging device 12 and the neutralization device 20 operate simultaneously. Then, first, the drum-shaped photosensitive member 11 is positively charged by the charging device 12 including a scorotron. Then, the optical writing device 13 irradiates a laser beam according to the image signal, and the photoconductor 1
An electrostatic latent image is formed on 1. Next, the developing device 14 reversely develops the electrostatic latent image (well portion of the potential of the laser beam irradiation portion) on the photoconductor 11 with toner having the same polarity charge as the charge polarity. The obtained toner image is transferred onto the recording paper 16 by the transfer device 15.
Then, the non-fixed toner image on the recording paper 16 peeled off from the photoconductor 11 by the peeling device 17 is fixed by the fixing device 18 to obtain a predetermined copy image.

After this, the photoconductor 1 which has passed through the peeling device 17
In No. 1, the residual toner is cleaned by the cleaner 19 and enters the charge eliminating device 20. At this point of time, the photosensitive member 11 is unstable due to the mixture of the place where the latent image is formed and the place where the latent image is not formed, and the electric charge of the opposite polarity received when passing through the transfer device 15. In this state, the static eliminator 20 applies an electric field between the screen 32 to which the bias voltage is applied and the photoconductor 11 and simultaneously irradiates the photoconductor 11 with light from the static eliminator 31. Then, the photoconductor 11 receives light irradiation in a state where an electric field is applied by the action of an electric field,
The residual charges and the charges (photoexcited ion pairs) generated in the inner layer of the photoconductor 11 are released from the trap binding and move so as to cancel the charging potential, and the inner layer of the photoconductor 11 is homogenized electrically. Therefore, the surface potential of the photoconductor 11 is effectively eliminated, and the surface potential of the photoconductor 11 is initialized in preparation for the next image forming process.

Further, in the present embodiment, when the relationship between the distance between the screen 32, which is a conductive member, and the photoconductor 11 and the external electric field was examined, the results shown in Table 1 were obtained.

[0037]

[Table 1]

In the table, assuming that the thickness of the photoconductor layer (P / R) is 0.025 mm and the charging potential of the photoconductor 11 is 300V, the screen 32, which is a conductive member, and the photoconductor 11 are separated from each other. It is understood that when the distance is 1 mm, the external electric field acts about 24.4 V and 48.8 V with respect to the conductive member applied voltages of 1000 V and 2000 V, respectively. Here, the external electric field is (voltage applied to the conductive member / 1.0
25) × 0.025. When the separation distance is separated by, for example, about 1.5 mm, the external electric field is 16.4 with respect to the conductive member applied voltages of 1000 V and 2000 V.
It is understood that the voltage V is reduced to about 32.8V.

Further, FIG. 5 shows a schematic diagram of the potential change state of the photoconductor in the present embodiment. In the figure, cycle 1-2 shows the difference between the charged surface potential of the first rotation and the charged surface potential of the second rotation after the photoconductor 11 starts to rotate. Further, the halftone (HT) potential indicates the potential when the photoconductor 11 is charged and exposed to light by an optical writing device (digital exposure system) over an image area ratio of 75%, and the HT portion potential difference is the photoconductor 11. The difference between the halftone (HT) potential of the first rotation and the halftone (HT) potential of the second rotation is shown.

FIG. 6 shows the relationship between the voltage applied to the conductive member (screen 32) and the cycle 1-2 in the grid potential (VGrid).
Was changed to 300V, 500V, and 700V and examined. Further, FIG. 7 shows a conductive member (screen 32).
The relationship between the applied voltage and the potential difference of the HT part is calculated by using the grid potential (VGr
id) was changed to 300V, 500V, 700V, and was investigated. According to FIG. 6, cycle 1-2 does not improve so much even if the voltage applied to the conductive member is increased,
It can be seen from FIG. 7 that the potential difference decreases as the applied voltage in the HT portion potential difference increases.
From the above results, when the image output was performed by applying a bias larger than the bias applied to the grid 23 of the charging device 12 made of scorotron to the conductive member before being charged to a desired potential, the density was stabilized. It was confirmed that an image could be obtained.

Second Embodiment FIGS. 8 and 9 show a second embodiment of the image forming apparatus to which the present invention is applied. In the figure, the basic configuration of the image forming apparatus is substantially the same as that of the first embodiment, but the first embodiment is the same.
Unlike the above, the charge eliminating device 20 includes a charge eliminating lamp 31 and a conductive glass plate 34 as a conductive member provided between the charge eliminating lamp 31 and the photoconductor 11. In the present embodiment, as the conductive glass plate 34, for example, a so-called Nesa glass in which a transparent conductive film is baked on the side of the static elimination lamp 31 of a transparent glass plate having a thickness of 1 mm is used, It is spaced apart from the photoconductor 11 by about 1 mm. A bias power source 33 is connected to the conductive glass plate 34, and a DC bias of about 500 to 2000 V is applied. A Tang ten lamp was used as the static elimination lamp 31, and a filter was used to transmit only the wavelength of 500 nm to 800 nm.

Therefore, in the case of the first embodiment, since the screen 32, which is a conductive member, blocks the optical path of the static elimination light from the static elimination lamp 31, it is necessary to increase the light quantity of the static elimination lamp 31 to some extent. According to the present embodiment, the conductive glass plate 34 does not block the optical path of the static elimination light from the static elimination lamp 31, so that the surface potential of the photoconductor 11 is reduced to the residual potential by 2 to 5 times. It was confirmed that just by irradiating with light, the charge removal effect of the photoconductor 11 can be obtained, and an image with stable density can be obtained, as in the first embodiment.

Third Embodiment FIG. 10 shows a charge eliminating device 20 and a charging device 12 used in the image forming apparatus according to the present embodiment. In the figure,
Unlike the first and second embodiments, the static eliminator 20 is configured such that the arc tube 35 of the static eliminator lamp 31 has conductivity.
5 is brought close to the photoreceptor 11 by about 0.5 mm to 1.5 mm, and the arc tube 35 is connected to the bias power source 33.
Voltage of the same polarity as the photoconductor 11 (about 500-2000V)
Is applied. According to the present embodiment, since it is not necessary to use a dedicated member as the conductive member,
The device configuration is simplified.

Fourth Embodiment FIG. 11 shows a charge eliminating device 20 and a charging device 12 used in the image forming apparatus according to the present embodiment. In the figure,
The static eliminator 20 includes the static eliminator 3 as in the first embodiment.
The screen 36 is provided between the photosensitive member 11 and the photosensitive member 11, but unlike the first embodiment, the screen 36 extends the grid 23 of the charging device 12 made of a scorotron to the static elimination lamp 31 side, and the grid 23 It is configured integrally with. A bias power supply 37 that also serves as a grid power supply is connected to the screen 36. In the present embodiment, since the screen 36 has to be arranged close to the photoconductor 11, the grid 23 of the charging device 12 is inevitably closer to the photoconductor 11 as compared with the respective embodiments. Need to be placed.
Therefore, according to the present embodiment, the charging device 12 and the static eliminator 20 can be integrated by using the grid 23 as well, and the device configuration is simplified accordingly.

Fifth Embodiment FIGS. 12 and 13 show a fifth embodiment of the image forming apparatus to which the present invention is applied. In the figure, the basic configuration of the image forming apparatus is substantially the same as that of the first embodiment, but unlike the first embodiment, the static eliminator 20 includes a static elimination lamp 31, and the static elimination lamp 31 and the photoconductor 11. It is composed of a conductive film 38 as a conductive member provided therebetween. The same components as those in the first embodiment are designated by the same reference numerals as those in the first embodiment, and detailed description thereof will be omitted here. In the present embodiment, the conductive film 38 is formed by curving a transparent film member having a transparent conductive film printed thereon in a convex shape toward the photoconductor 11.
The conductive film 38 is connected to a bias power source 33 for applying a bias voltage of about 500 to 2000V.

Therefore, in the present embodiment, the static eliminator 20 applies an electric field directly to the photoconductor 11 via the conductive film 38 and simultaneously irradiates the photoconductor 11 with light from the static elimination lamp 31. At this time, the contact type static eliminator 20 in the present embodiment is different from the non-contact type static eliminator in the photoconductor 11 and the conductive film 38 which is a conductive member.
Since the distance between and is extremely small, the external electric field also dramatically increases, and the residual charges and the charges generated in the inner layer of the photoconductor 11 are easily released from the trap binding and easily moved to be discharged, so Easy to homogenize. Therefore, in the present embodiment, the static elimination effect of the photoconductor 11 is larger than that of the non-contact type static eliminator. The contact type is slightly inferior to the non-contact type in terms of maintainability because the conductive film 38, which is a conductive member, is soiled with toner or the like.

The difference between the voltage applied to the conductive member (conductive film 38) in the present embodiment and the cycle 1-2 (the charged surface potential of the first rotation and the charged surface potential of the second rotation after the photoconductor 11 starts rotating). 14), the results of examining the relationship with the grid potential (VGrid) changed to 300V, 500V, and 700V are shown in FIG. 14, and the voltage applied to the conductive member (conductive film 38) and the HT portion potential difference (one rotation of the photoconductor 11). The relationship between the halftone (HT) potential of the eye and the halftone (HT) potential of the second rotation) is defined as the grid potential (VGrid) of 300.
Fig. 1 shows the results of the examinations with V, 500 V, and 700 V changed.
5 respectively. According to the figure, the potential difference between the cycle 1-2 and the HT part is suppressed to be smaller than that in the case of the non-contact type static eliminator (see FIGS. 6 and 7 of the first embodiment), and the repetitive charging characteristics and the residual potential are reduced. It is confirmed that the stability is further improved.

Sixth Embodiment FIG. 16 shows a charge eliminating device 20 and a charging device 12 used in the image forming apparatus according to the present embodiment. In the figure,
In the static eliminator 20, a light-transmissive conductive cylindrical member 39 is disposed in contact with the photoconductor 11, and a bias power source 33 for applying a bias voltage (about 500 V to 2000 V) is connected to the conductive cylindrical member 39 to make the conductive material. The static elimination lamp 31 is provided inside the cylindrical member 39. Therefore, also in the present embodiment, the static eliminator 2 is substantially the same as in the fifth embodiment.
Reference numeral 0 indicates that the electric field is directly applied to the photoconductor 11 via the conductive cylindrical member 39, and at the same time, the light from the discharge lamp 31 is applied to the photoconductor 1.
1 to irradiate the photosensitive body 11 effectively.

Seventh Embodiment FIG. 17 shows a charge eliminating device 20 and a charging device 12 used in the image forming apparatus according to the present embodiment. In the figure,
In the static eliminator 20, a conductive bias roll 40 is disposed in contact with the photoconductor 11, a bias power source 33 for applying a bias voltage (about 500 V to 2000 V) is connected to the bias roll 40, and the bias roll 40 is further connected.
A static elimination lamp 31 for light irradiation is provided in the vicinity of the downstream side of the contact portion with the photoconductor 11. Therefore, according to the present embodiment, the static eliminator 20 applies an electric field to the vicinity of the downstream side of the contact portion of the bias roll 40 with the photoconductor 11 and simultaneously irradiates the photoconductor 11 with light from the static erasing lamp 31. Effectively eliminates static electricity.

Eighth Embodiment FIG. 18 shows a charge eliminating device 20 and a charging device 12 used in the image forming apparatus according to the present embodiment. In the figure,
The charging device 12 differs from the first to seventh embodiments in that a conductive charging roll 41 is arranged in contact with the photoconductor 11 and the charging roll 41 has a VP-P (peak-to-peak voltage) of 2.0.
Bias power supply 42 with kV and DC voltage of 300-700V
Are connected. On the other hand, the static eliminator 20 uses the charging roll 41 to which the bias is applied, and is provided with a static elimination lamp 31 which is irradiated with light in the vicinity of the upstream side of the contact portion of the charging roll 41 with the photoconductor 11. Therefore, according to the present embodiment, the static eliminator 20 includes the charging roll 41.
The electric field is applied to the vicinity of the upstream side of the contact portion of the photoconductor 11 with the photoconductor 11, and at the same time, the light from the static elimination lamp 31 is irradiated to
Effectively removes electricity. The charging roll 41 as the charging device 12 charges the photoconductor 11 on the downstream side of the contact portion with the photoconductor 11.

[0051]

As described above, according to the present invention, in an image forming apparatus using a photoreceptor having a High-γ characteristic, light irradiation is simultaneously performed under the action of an electric field having the same polarity as the photoreceptor before image formation. Therefore, it is possible to ensure the stability of the repeated charging characteristics and the stability of the residual potential of the photoconductor, and the image forming apparatus using the photoconductor of the High-γ characteristic can be secured. The prospect of practical application was obtained.

In the present invention, when a photoreceptor composed of X-type metal-free phthalocyanine and a binder resin is used as a photoreceptor having a High-γ characteristic, stability of repeated charging characteristics of the photoreceptor having a High-γ characteristic and The stability of the residual potential can be ensured extremely reliably.

Furthermore, in the present invention, as the pretreatment means, a conductive member to which a bias is applied is disposed between the light irradiating means and the photoconductor so as not to be in contact with the photoconductor. The charge removal effect of the photoconductor can be exhibited without damaging the photoconductor. On the other hand, in the present invention, when the conductive member that is arranged in contact with the light irradiation unit and the photoconductor and is applied with the bias is used as the pretreatment unit, the electric field can be surely applied to the photoconductor. This makes it possible to more reliably promote the charge removal effect of the photoconductor.

Further, in the present invention, as the pretreatment means, a conductive roll to which a bias is applied so as to contact the photosensitive member and a light irradiating means for irradiating the vicinity of the contact portion of the conductive roll with the photosensitive member are used. By doing so, it becomes possible to irradiate the photoconductor directly with the light by the light irradiation means while surely applying the electric field to the photoconductor. Can be promoted. Utilizing a charging roll as an existing conductive roll,
If the light irradiation means for irradiating light is provided in the vicinity of the upstream side of the photoconductor contact portion of the charging roll, the configuration of the pretreatment means can be extremely simplified.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of an image forming apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing the configuration of the image forming apparatus according to the first embodiment.

FIG. 3A is an explanatory diagram showing a light attenuation characteristic of the photoconductor used in the first embodiment, and FIG. 3B is an explanatory diagram showing its dark attenuation characteristic.

FIG. 4 is an explanatory diagram showing a static eliminator used in the first embodiment.

FIG. 5 is an explanatory diagram showing changes in the potential state of the photoconductor corresponding to the image forming process in the first embodiment.

FIG. 6 is a graph showing a relationship between a voltage applied to a conductive member and a charging potential difference (cycle 1-2) between the first rotation and the second rotation of the image forming cycle in the first embodiment.

FIG. 7 is a graph showing the relationship between the voltage applied to the conductive member and the halftone potential difference between the first rotation and the second rotation of the image forming cycle in the first embodiment.

FIG. 8 is an explanatory diagram showing a configuration of an image forming apparatus according to a second embodiment.

FIG. 9 is an explanatory diagram showing a static eliminator used in the second embodiment.

FIG. 10 is an explanatory diagram showing a static eliminator used in the third embodiment.

FIG. 11 is an explanatory diagram showing a static eliminator used in the fourth embodiment.

FIG. 12 is an explanatory diagram showing a configuration of an image forming apparatus according to a fifth embodiment.

FIG. 13 is an explanatory diagram showing a static eliminator used in the fifth embodiment.

FIG. 14 is a graph showing a relationship between a voltage applied to a conductive member and a charging potential difference (cycle 1-2) between the first rotation and the second rotation of the image forming cycle in the fifth embodiment.

FIG. 15 is a graph showing the relationship between the voltage applied to the conductive member and the halftone potential difference between the first rotation and the second rotation of the image forming cycle in the fifth embodiment.

FIG. 16 is an explanatory diagram showing a static eliminator used in the sixth embodiment.

FIG. 17 is an explanatory diagram showing a static eliminator used in the seventh embodiment.

FIG. 18 is an explanatory diagram showing a static eliminator used in the eighth embodiment.

FIG. 19 is a graph showing a potential decay characteristic of a single-layer type photoconductor by an induction effect.

[Explanation of symbols]

1, 11 ... Photoreceptor, 2 ... Pretreatment means, 12 ... Charging device,
23 ... Grid, 20 ... Static eliminator, 31 ... Static erasing lamp,
32, 36 ... Screen (conductive member), 33, 37,
42 ... Bias power source, 34 ... Conductive glass plate (conductive member), 35 ... Arc tube (conductive member), 38 ... Conductive film (conductive member), 39 ... Conductive cylindrical member (conductive member), 40 ... Bias roll (conductive roll), charging roll (conductive roll)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kumiko Ichikawa 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Xerox Co., Ltd. Incorporated (72) Inventor Tetsuya Kato 3-10-1 Higashisanda, Tama-ku, Kawasaki City, Kanagawa Prefecture Matsushita Giken Co., Ltd.

Claims (5)

[Claims] 1. An image is formed by an electrophotographic method using a photoconductor (1) having a potential decay characteristic that abruptly decays at a certain exposure amount (A0) with a uniformly charged surface potential (VP). The image forming apparatus is provided with pretreatment means (2) for simultaneously irradiating the photoconductor (1) with light under the action of an electric field of the same polarity as the photoconductor (1) before image formation. Forming equipment. 2. The image forming apparatus according to claim 1, wherein the photoconductor (1) is a single-layer organic photoconductor composed of an X-type metal-free phthalocyanine and a binder resin. 3. The pretreatment means (2) according to claim 1, wherein the pretreatment means (2) irradiates the photoconductor (1) with light, and the pretreatment means (2) is provided between the photoirradiation means and the photoconductor (1). 2. An image forming apparatus comprising: a transparent conductive member that is disposed in non-contact with the photosensitive member (1) in a non-contact manner, and a voltage applying unit that applies a voltage to the conductive member. 4. The pretreatment means (2) according to claim 1, wherein the pretreatment means (2) irradiates the photoconductor (1) with light, and the pretreatment means (2) is provided between the photoirradiation means and the photoconductor (1). 2. An image forming apparatus comprising: a transparent conductive member disposed in contact with the photoconductor (1) and voltage applying means for applying a voltage to the conductive member. 5. The pretreatment means (2) according to claim 1, wherein the conductive roll is arranged in contact with the photoconductor (1), and a voltage applying means for applying a voltage to the conductive roll. An image forming apparatus, comprising: a light irradiating means for irradiating light on the vicinity of a contact portion of a photosensitive member (1) of a conductive roll.