JP4091758B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus that can be used as a copying machine, a printer, and a printing plate for printing.
[0002]
[Prior art]
Conventionally, various apparatuses using an electrophotographic system are known, but typically, an image forming apparatus such as a so-called copying machine or printer that typically copies or prints an image on a normal transfer material such as plain paper or film. Is well known.
In such an image forming apparatus, a photosensitive member in which a photoconductive layer such as an organic photo semiconductor (OPC) is provided on the surface of a drum-like or belt-like conductive substrate made of aluminum or the like by coating or vapor deposition is used. An electrostatic latent image is formed on the surface of the body using a well-known electrophotographic method, and a visible toner image is formed by attaching toner to the electrostatic latent image. The film is transferred onto a normal transfer material such as a film or a second original drawing.
[0003]
Such transfer is usually carried out so that the transfer material is brought into close contact with the surface of the photosensitive member on which the toner image is formed, and a known means such as a corona charger or a charging roller is used from the back side of the transfer material at the close contact portion. This is performed by applying a transfer bias and electrostatically adsorbing the toner on the photoreceptor to the transfer material side.
[0004]
On the other hand, in the recent printing industry, a printed document is created as digital data, and this data is directly read by an electronic board device (DTP) and reproduced on a desktop to perform necessary processing and editing.
The data edited on the desktop is transferred to the plate making machine via the network line, and is printed as halftone data on a predetermined number of films for output.
This film is baked on a printing plate, for example, a PS plate (plate having a photosensitive layer) or the like, and is set in a printing machine as a printing plate of an offset rotary press or the like.
[0005]
[Problems to be solved by the invention]
By the way, in the conventional production of the printing plate, many troublesome processes such as exposure, development, washing, erasing, and burning are conventionally performed in the printing process of data on the film as a first step and the subsequent printing plate process. In order to perform these, an operator who is familiar with the work is required.
[0006]
The inventors of the present invention have focused on performing a printing plate using a conductive or semiconductive transfer material with an image forming apparatus using the electrophotographic method described above.
[0007]
However, when a printing plate is to be manufactured by an electrophotographic image forming apparatus having the above-described configuration, a transfer material having high electrical resistance such as paper or film used in a copying machine or a printer (hereinafter, usually referred to as normal). (It is called a transfer material and is treated as an insulating transfer material in this specification.) Transfer is performed on a conductive or semiconductive transfer material such as a PS plate under the same conditions as the transfer charge imparting conditions for When it was performed, it was difficult to obtain a clear image obtained with a transfer material such as paper.
[0008]
Therefore, the present inventors replaced a conventional transfer material having high electrical resistance such as paper and film, which has been conventionally used, with a conductive or semiconductive transfer material, such as a PS plate, and thereby a printing plate for printing. It is an object of the present invention to provide an image forming apparatus that can be used as a manufacturing apparatus, can obtain a sufficient image accuracy, and can form a clear image with a simple configuration.
[0009]
[Means for Solving the Problems]
In order to solve the above problem, in an image forming apparatus provided with a transfer unit that supplies a transfer material in contact with an image carrier and applies a bias from the back surface of the transfer material, the transfer material is electrically conductive (or Two types of transfer materials (semi-conductive) and insulating can be used, and the transfer section includes a first transfer means facing the image carrier and the first transfer as viewed from the transfer direction of the transfer material. The second transfer means is turned on when the second transfer means is composed of a pair of electrodes provided at upstream and downstream positions of the means and the transfer material is conductive (or semiconductive). When the transfer material is insulative, there is provided switching means that operates to turn on the first transfer means .
[0010]
Further, the second transfer means is applied with a lower transfer bias than the first transfer means .
[0011]
Still further, the conductive or semiconductive transfer material is electrically insulated from members other than the pair of electrodes provided respectively upstream and downstream of the image carrier and the first transfer means . It is characterized by that.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
A preferred embodiment of the present invention will be described with reference to the drawings. In the following example, a conductive or semiconductive transfer material (hereinafter referred to as a special transfer material) will be described. As the special transfer material, other types of conductive or semiconductive materials such as PS plates are used. The present invention can also be applied to a sex member.
[0015]
FIGS. 1 and 2 are views showing the periphery of a transfer portion for transferring a toner image of the image forming apparatus according to the present invention onto a transfer material. FIG. 1 is a case of transfer to a special transfer material, and FIG. The state at the time of transfer in the case of transfer to a normal transfer material having high resistance is shown.
[0016]
As described above, in the example shown in FIG. 1, as a special transfer material, a hydrophilic layer is provided on a conductive substrate made of aluminum, or the surface of the substrate is treated so as to have hydrophilicity. The case where the transfer material which gave is used is shown.
[0017]
Each component constituting the conveyance path and the transfer unit will be described according to the supply direction (flow) of the transfer material.
In FIG. 1, a photosensitive layer made of an organic photoconductor such as copper phthalocyanine or an inorganic photoconductor such as selenium is coated or vapor-deposited on the surface of a substrate made of a metal such as aluminum that can be used as an image carrier. The electrophotographic photosensitive member rotates in the direction of arrow A. In this example, the photosensitive member 1 has a drum shape, but may have an endless belt shape.
[0018]
Although not shown, the surface of the photoconductor 1 is uniformly charged with a specific polarity around the photoconductor 1 according to the rotation direction A, such as an eraser such as an eraser lamp for electrostatically neutralizing the photoconductor 1. An exposure device that exposes optical information with a laser or LED to form a desired electrostatic latent image on the surface of the charged photoreceptor 1, and a surface of the photoreceptor 1. Developers for supplying toner powder as charged powder and developing the electrostatic latent image formed on the photoreceptor 1 to form a toner powder image are provided in order. Acts on the photosensitive member 1 in order according to the rotation of. As the photosensitive device 1 and the above-described devices around it, the configuration of each part of an image forming apparatus using a known electrophotographic method can be applied. In this example, lipophilic toner is used as the toner powder.
[0019]
In the figure, reference numeral 2 denotes a guide for guiding a transfer material conveyed from a transfer material supply source (not shown) along the upper surface thereof to the transfer unit 7. A preliminary guide 3 is provided to prevent the camera from falling down.
The transfer unit 7 basically has two types of transfer means that can be switched according to the properties of the transfer material, that is, whether the transfer material is a special transfer material or a normal transfer material. have.
In the figure, reference numeral 4 denotes an electrode member which is a first electrode used for transfer to a special transfer material which is one transfer means, and is composed of a conductive member, and the transfer portion 7 transport direction ( It is located upstream from the (B direction).
[0020]
Next, reference numerals 5 and 6 denote a transfer corona discharger for transferring a toner image onto a normal transfer material, and a separation corona discharger as means for separating the transfer material from the photoreceptor 1.
As another transfer unit and separation unit, a charging roller in which a necessary bias is applied to each conductive roller may be used.
Reference numeral 8 in the figure denotes one transport roller that supports a transport belt 9 that is a means for transporting a transfer material onto which an electrostatic latent image separated from the photoreceptor 1 is transferred to a fixing device (not shown). It also serves as a second electrode for transfer to a special transfer material, and is constituted by a conductive member.
[0021]
As described above, in the present invention, upstream of the dischargers 5 and 6 as viewed from the transfer material conveyance direction (B direction) so as to straddle the transfer corona discharger 5 and the separation corona discharger 6 of the transfer unit 7. The first and second electrode members 4 and 8 made of conductive members are respectively provided downstream of the special transfer material so that the two electrode members 4 and 8 straddle the corona discharger. It is supplied so as to be in contact with the surface of the photoreceptor at an appropriate pressure.
[0022]
In particular, the arrangement position of the first electrode member 4 is important, and is preferably a position where the transferred transfer material is surely in contact with the surface of the photoreceptor 1. Therefore, the first electrode member 4 is provided in the vicinity of the transfer corona discharger 4. In the embodiment, the first electrode member 4 is connected to the outer wall of the transfer corona housing of the transfer corona discharger 5 on the transfer material insertion side. 5b is electrically insulated from each other so as to be supported by bonding or the like via an appropriate insulating member, but may be provided at a position away from the corona housing, and similarly, as the second electrode Although it is configured to also serve as a support roller for the transport belt 9, the second electrode may be configured separately from the transport roller 8, in which case the second electrode needs to be limited to a roller shape. Absent.
[0023]
The transfer material used as one of the typical special transfer materials in the present invention is provided with a hydrophilic layer on a conductive 0.1-0.5 mm thick substrate made of aluminum or the like, or the substrate However, in addition to this, a conductive or semiconductive member with low electrical resistance may be used.
[0024]
Next, the transfer corona discharger 5 serving as the first transfer unit, the electrode plate 4 serving as the first electrode serving as the second transfer unit, and the transport roller 8 serving as the second electrode are characterized by the nature of the transfer material. The on / off switching of the corresponding operation will be described. Since the separation corona discharger 6 is turned on and off at the same timing as the transfer corona discharger 5, the power supply of the separation corona discharger 6 will be described together with the transfer corona discharger 5.
[0025]
First, an electrode plate 4 as a first electrode member constituting one electrode of the second transfer means is electrically connected to a DC power source 20 having a polarity opposite to the polarity of the toner image via a switch 10. Similarly, the corona electrode 5a of the transfer corona discharger 5 is connected via a switch 11 to a DC power source 21 having a polarity opposite to the polarity of the toner image. Further, the corona electrode 6 a of the separation corona discharger 6 is connected to the AC power source 22 via the switch 12. Similarly, a transport roller 8 that is a second electrode member constituting the other electrode of the second transfer unit is connected to a DC power source 23 having a polarity opposite to the polarity of the toner image via a switch 13.
[0026]
The switches 10 and 13 for connecting the first and second electrode members 4 and 8 to the power sources 20 and 23 are turned on and off at interlocked timings so that they can work in cooperation with each other. Regarding the relationship between the transfer corona discharger 5 and the separation corona discharger 6, when the switches 10 and 13 are in the on state, the switches 11 and 12 are off, and when the switches 10 and 13 are in the off state, the switch 11, 12 is set to be on. The switches 10 and 13 are turned on when the transfer material is conductive or semiconductive, and the switches 11 and 12 are turned on when the transfer material is a normal transfer material having high electrical resistance such as paper.
[0027]
Further, a structure that contacts the transfer material in order to transport the transfer material around the transfer unit 7, for example, the electrode plate 4 that is the first electrode and the transport that is the second electrode, such as the guide 2 and the preliminary guide 3. Components other than the roller 8 and the photosensitive member 1 are electrically completely insulated, or are in an electrically floating state with respect to the ground through a varistor or the like.
[0028]
Next, with respect to FIG. 1 in the case where a special transfer material is used as the transfer material of this embodiment and in FIG. 2 in the case where a normal transfer material is used, the operation of the apparatus according to the present invention, in particular, on / off of each switch 10-13. This will be explained in more detail.
First, the special transfer material 14 is inserted into the image forming apparatus by manual feed or automatic feeding by a paper feed guide (not shown). The inserted special transfer material 14 is conveyed toward the transfer portion 7 of the photosensitive member 1 by the conveyance guide 2 and the preliminary guide 3, and the electrode plate 4, the transfer corona discharger 5, and the separation corona discharger 6 as the first electrode. , Is sent to the conveyor belt 9 via the support roller 8 which is the second electrode member, and is discharged out of the apparatus through a fixing device (not shown).
[0029]
The special transfer material 14 is moved by the two electrodes of the first electrode member 4 and the second electrode member 8 so that the surface of the special transfer material 14 comes into contact with the surface of the photoreceptor 1 at an appropriate pressure when passing through the transfer portion 7. The back surface is supported, and at this time, the switches 10 and 13 of the first electrode member 4 and the second electrode member 8 are turned on, and transfer from the respective power sources 20 and 23 to the special transfer material is performed. A suitable value of transfer bias is applied. At this time, the switches 11 and 12 of the transfer corona discharger 5 and the separation corona discharger 6 of the transfer unit 7 are turned off. In addition, as described above, the electrical relationship with each component constituting the transport path for transporting the special transfer material 14 including the transfer unit 7 and the like is all insulated, that is, electrically floating, and the transfer corona discharger 5 A bias is applied to the special transfer material 14 by rubbing the back surface of the special transfer material 14 on the electrode plate (first electrode member) 4 and the conveying roller 8 provided so as to cover the corona housing. The toner image can be transferred to the toner image 14. In addition, the application of the bias to the first electrode member 4 and the second electrode member 8 is set to substantially the same voltage, and in some cases, only one of the first and second electrode members is applied. It may be configured to apply a bias.
[0030]
In the configuration of this embodiment, the switches 10 and 13 of the first electrode member 4 and the second electrode member 8 are turned on with the switches 11 and 12 of the transfer corona discharger 5 and the separation corona discharger 6 turned off, respectively. Then, when a transfer experiment was performed by changing the value of the bias applied between the photosensitive member 1 and the special transfer material 14 stepwise, for example, the surface potential of the photosensitive member 1 is -750 to -850 V, and the polarity of the toner is negative. When the transfer to the special transfer material 14 is performed with the bias voltage to the special transfer material in the range of +50 V to 250 V, preferably in the range of +150 V to +200 V, it is sufficient as a plate for precise and clear printing. The preferable image which can be used was obtained.
[0031]
The bias applied between the photosensitive member 1 and the special transfer material 14 is preferably opposite in polarity to the toner polarity. When a bias of DC 250 V or more is applied, a discharge occurs between the surface of the photosensitive member 1 and the special transfer material 14 and the image. Becomes unclear, and when a bias of 50 V or less is applied, the transfer efficiency tends to deteriorate.
[0032]
Next, FIG. 2 of Example 2 in which a normal transfer material is used as the transfer material will be described. First, the paper or film 15 that is a normal transfer material is inserted into the apparatus by a paper feed unit or a paper feed guide (not shown) as in the first embodiment. The inserted paper or film 15 is transported toward the transfer section 7 of the photoreceptor 1 by the transport guide 2 and the preliminary guide 3, and the electrode plate 4, the transfer corona 5, the separation corona 6, the second electrode, and the second electrode. It passes through the electrode 8, is sent to the conveyor belt 9, passes through a fixing device (not shown), and is discharged outside the device.
[0033]
At this time, the conveyance path for conveying the paper 15 which is a normal transfer material including the transfer unit 7 and the like is opposite to the case of the first embodiment, and the respective switches 11 and 12 of the transfer corona 5 and the separation corona 6 are turned on. In this state, the switches 10 and 13 of the electrode plate 4 and the transport roller 8 as the first and second electrode members are turned off, and the bias applied to the electrode plate 4 and the transport roller 8 is applied to the transfer corona 5. A high voltage bias that is an order of magnitude higher than that is applied.
In addition, about the switch of the electrode plate 4 and the conveyance roller 8, it may be in the ON state, without turning off depending on the case.
[0034]
In the second embodiment, the switches 11 and 12 of the transfer corona discharger 5 and the separation corona discharger 6 are respectively turned on, and the electrode plate 4 and the transport roller 8 which are the first and second electrode members are respectively turned on. With the switches 10 and 13 turned off, for example, the surface potential of the photosensitive member 1 is -750 V to -850 V, the toner polarity is negative, a bias of DC +6000 V is applied to the transfer corona 5, and a bias of AC 7000 V is applied to the separation corona 6. When the toner image was transferred to the transfer material, a sufficiently clear and preferable image could be obtained as a copying machine or a printer.
[0035]
【The invention's effect】
The image forming apparatus of the present invention is provided with two transfer units suitable for the properties of the transfer material, and by switching a switch for turning on and off the first and second transfer units, even in a transfer material such as paper, In addition, good transfer can be obtained even with a conductive or semiconductive transfer material for a printing plate for printing, and the cost can be reduced because of a simple configuration.
[Brief description of the drawings]
FIG. 1 is a schematic side sectional view showing a state of an image forming apparatus when a PS plate according to the present invention is used as a transfer material.
FIG. 2 is a schematic sectional side view showing a state of an image forming apparatus when paper or the like according to the present invention is used as a transfer material.
[Explanation of symbols]
1 Photoconductor (image carrier)
2 Guide 3 Preliminary guide 4 Electrode plate (first electrode member of second transfer means)
5 Transfer corona discharger (first transfer means)
6 Separation Corona Discharger 7 Transfer Unit 8 Conveying Roller (First Electrode Member of Second Transfer Unit)
9 Conveying belt 10 Switch 11 Switch 12 Switch 13 Switch 14 Special transfer material 15 Normal transfer material

Claims (3)

In an image forming apparatus provided with a transfer unit that supplies a transfer material in contact with an image carrier and applies a bias from the back surface of the transfer material, the transfer material is conductive (or semiconductive) and insulating. These transfer materials can be used, and the transfer section is located at upstream and downstream positions of the first transfer means as viewed from the transfer direction of the transfer material and the first transfer means facing the image carrier. A second transfer means comprising a pair of electrodes provided, and when the transfer material is conductive (or semiconductive), the second transfer means is turned on, and the transfer material An image forming apparatus , comprising: a switching unit that operates to turn on the first transfer unit when the first transfer unit is insulative . The image forming apparatus according to claim 1, wherein the second transfer unit is applied with a lower transfer bias than the first transfer unit . The conductive or semiconductive transfer material is electrically insulated from members other than a pair of electrodes provided upstream and downstream of the image carrier and the first transfer unit, respectively. The image forming apparatus according to claim 1 or 2.

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