JPS61100767A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain a fixed toner image having good quality by forming a titled image in such a manner that the scattering of a toner on a transfer material after the sepn. from a transfer material support can be prevented. CONSTITUTION:The 1st electrostatic charger 401 disposed forward in the conveying direction of the 1st conveying belt 271 in such a manner that the aperture plane for discharge is made approximately flush with the extension plane of the conveying path plane of said belt is attached with conveying guide rods 402 having an insulating characteristic at suitable intervals in the longitudinal direction at the aperture plane for discharge in order to prevent the thrusting in of the transfer material. The high voltage of the polarity (positive polarity) reverse from the polarity of the toner in the stage of the development is impressed to the discharge wire 403 of the charge 401 by a power source D1 which is adjustable in the voltage. The high voltage of the same polarity (negative polarity) as the polarity of the toner in the stage of the development is impressed by a voltage adjustable power source D2 to the discharge wire 405 of the 2nd electrostatic charger 404 formed to the same construction as the construction of the charger 401.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an image forming apparatus equipped with a transfer device, and more particularly to an image forming apparatus that prevents disturbance of a toner image after transfer.

[Background of the invention]

Generally, in an image forming apparatus that transfers a toner image developed on an image carrier such as a photosensitive drum to a transfer material held on a transfer material support such as a transfer drum, the photosensitive drum has different color components. A variety of electrophotographic copying apparatuses have been proposed in which a color image is obtained by sequentially forming developed images and sequentially transferring the developed images onto a transfer material held on a transfer drum.

Figure 4 shows such color electronics! An example of a photocopying device is shown below. In the figure, 1 is a 315-sized photosensitive drum consisting of a surface insulating layer, a photoconductive layer, and a conductive substrate, and is supported on a shaft 2 and rotates in the direction of an arrow 3. When the photosensitive drum l rotates, the original w40 with the document table placed on the lath 4 moves to the lath 5.
It is irradiated with light.

The reflected light is reflected by the first scanning mirror 2-6 and the second scanning mirror 7, passes through the lens 8 and the third scanning mirror 2-9, and is then color-separated by the blue filter 101 of the color separation filter 10. Furthermore, the 4th Mi? -tto forms an image on the photosensitive drum l.

The photosensitive drum l is uniformly neutralized by an AC discharger 13 and a pre-exposure lamp 14, then charged by a primary charging discharger 15 to, for example, glass polarity, and then charged to a secondary charger 16. The discharge occurs at the same time that the color-separated image α light 12 is applied. Furthermore, by performing full-face exposure using the full-face exposure rung 17, a blue color separation latent image is formed on the drum 1.

The electrostatic latent image on the photosensitive drum l is then transferred to the developing device 18,
Visualized with toner. The developing device 18 is Yeo-18&
s magenta 18b1 cyan 18es and black 18604
The developing device is composed of several developing devices, and a developing device designated in accordance with the color separation filter used for exposure operates to obtain a toner image of the required color.

On the other hand, the transfer material 20 in the cassette 19 is fed into the transfer machine by the paper feed roller 21, and the leading edge of the transfer material is gripped by the grooves 4231 of the transfer drum 23. Note that the mesh screen 232, which is a transfer material carrying sheet to be described later and is provided on the transfer drum 23, has charges on the front and back sides of the screen removed in advance by AC dischargers 234 and 235 for separation.

The transfer material gripped by the groove /4' 231 of the transfer drum 23 is transferred to the screen 232 as the transfer drum 23 rotates.
The yellow toner image on the photosensitive drum is transferred onto the transfer material while the transfer material passes between the transfer discharge device 233 and the photosensitive drum l. Along with this transfer, the transfer material is held on the screen surface by electrostatic attraction.

During the above-mentioned transfer, the transfer drum 23 is in a state of grooving.

of? The tip of the transfer material 20 is gripped at 231 and rotated a predetermined number of times while being electrostatically absorbed λ'f by the mesh screen 232, and a toner image of the required number of colors is transferred onto the transfer material. That is, in the case of full-color copying, following the transfer of the yellow toner image described above, the transfer of the magenta toner image by green color separation exposure, and then the transfer of the cyan toner image by red color separation exposure are performed in sequence.

After a predetermined number of transfers, when the leading edge of the transfer material approaches the separation position, the gripper 231 is released, and the 11L separation device 234
Both the transfer material and the screen are neutralized by the alternating current corona discharge from 235 and 235, and the transfer material is forcibly separated by the separation claw 236 approaching the screen. After the transfer material is separated, it is guided by the conveyor belt 2-7 to the heat roller fixing device 2B, where it is heated and fixed, and then discharged onto the tray 30.

After the transfer, the photosensitive drum 1 is cleaned by a cleaning device 31 made up of 4 fI elastic blades to remove its surface force and proceed to the next image forming cycle.

FIG. 5 shows a perspective view of the transfer drum 23. As shown in FIG.

This transfer drum 23 is a screen 23 that carries a transfer material.
2, a cylinder 237 provided with a notch for supporting the screen at its edge, and grits 4231 for gripping the leading edge of the transfer material.

Materials for the above-mentioned screens include polyester, nylon, silk, knitted fibers such as e-ligropyrene, or polyester. A sheet of liglovirene or the like with holes pressed is used. In either case, a mesh screen with about 50 to 100 meshes is used.

By the way, in such an image forming apparatus, when the transfer material is separated from the screen force 1 of the transfer drum after the transfer is completed, an air discharge V6Yj generated between the transfer material and the screen is applied. Since the toner on the transfer material scatters and causes image holes, in order to prevent or reduce the occurrence of this aerial discharge, the AC discharger 234.
, 235 applies alternating current corona discharge from both the front and back sides of the transfer material 200, thereby removing charges on the front and back surfaces of the transfer material and the front and back surfaces of the screen, and removing the image (i1) caused by toner scattering.
Prevents product shortages.

However, even with such a method, toner scattering may occur after the transfer material is separated.

FIG. 6 is a schematic diagram illustrating the state of static elimination of the screen 232, which is a transfer material carrying sheet, the transfer material, and the toner by the above-described static elimination method.

FIG. 6A shows a state immediately after the toner image T is transferred onto the transfer material 20, and in the following description, for convenience, the polarity of the toner T is assumed to be negative (c). That is, the transfer discharge device 233
As a result, positive charges are attached to the back surface of the screen 232 and the back surface of the transfer material 20 corresponding to the open area of the screen. On the other hand, due to the action of these charges, a negative (→polar) toner image T is transferred to the surface of the transfer material 20, but after the transfer, the toner image T is negatively charged due to the air discharge when the photosensitive drum and the transfer material are separated. (
f) Some polar charges are also attached.

Fig. 6 FB) is separated from the transfer material 2 by the separating claw 236 (Fig. 4).
This is the state of charge when the static electricity is removed by the static eliminating dischargers 234 and 235 when the screen 232 is separated from the screen 232. AI and A2 in the figure are the static elimination dischargers 234
and the AC power applied to 235. In this state, the negative charge of the toner T on the surface of the transfer material 20 and the negative charge of the area without toner T are neutralized and disappear.
Or decrease by a considerable amount. In addition, the positive (+) charges on the back surface of the transfer material 2o and the front surface of the screen 232 also disappear or decrease by a considerable amount.

FIG. 6 (Q is the charge state of the transfer @ 20 after separating the transfer material 20 from the screen 232; the toner has a slight charge or a slight negative H charge; while the transfer material The electric charge on the front and back sides of the toner disappears or decreases considerably.At this time, the If force of the toner to the transfer material is dominated by the physical adhesion force due to surface energy, etc., and the adhesion force due to electrostatic force is dominant. Since it is small, the adhesion force of the toner to the transfer material as a whole is small.

Therefore, in this state, the fixing device 28 to which the heat roller pair is applied
When the transfer material enters the pair of heat rollers, it is caused by the repulsive force due to the frictional charge on the fixing roller or the pressure roller, or by the extrusion force of anti-offset liquid or air that occurs when the transfer material is squeezed by the pair of heat rollers. The toner image on the transfer material is swept away or pushed out in the opposite direction to the direction of movement, causing toner scattering. Is this phenomenon caused by the toner itself? This is particularly likely to occur in a high humidity environment where the electric charge is small.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that can prevent disturbance of a toner image that occurs after separating a transfer material from a transfer material carrying sheet and can obtain a high-quality fixed toner image.

[Summary of the invention]

The gist for achieving the object of the present invention is that after corona transfer of the toner image visualized on the latent image carrier to the transfer material carried on the transfer material carrying notebook, corona charge removal is performed at the separation position. In an image forming apparatus that separates a transfer material from a transfer material carrying sheet and transports it through a fixing means to form a fixed toner image on the transfer material, a transfer material is separated from a transfer material carrying sheet, and is placed opposite to the lower part of the transfer material transport path leading to the fixing means. The image forming apparatus is characterized in that it is provided with a pair of corona dischargers that charge both the front and back surfaces of a transfer material to opposite polarities.

[Embodiments of the invention]

The present invention will be explained in detail below based on the embodiments shown in FIGS. 1 to 3.

In the figure, 271 is a mesh-like first belt body 271m.
is a first conveyor belt that rotates endlessly in the direction of the arrow by a drive source (not shown), and is disposed behind the separation claw 236, and the transfer material separated from the transfer drum 23 by the separation claw 236 is separated from the transfer drum 23 by the separation claw 236. The battery is transported between a pair of upper and lower opposing chargers. 272 is the 10th conveyance bell) 2
A first suction fan provided at the lower part of the transfer material conveying path surface of 71 brings the transfer material into close contact with the surface of the first belt body 271& by suction force passing through the main body of the first belt body 271. It looks like this. 4Ql is a first charger disposed in front of the conveyor belt 271 of the WJl in the conveyance direction so that the discharge opening surface substantially coincides with the extended surface of the conveyance path surface of the conveyor belt 271 of the WJl. In order to prevent the transfer material from entering, an insulating conveyor guide rod and a dome 4 are installed on the discharge opening surface.
02 are attached at appropriate intervals in the length direction, as shown in FIG. A high voltage having a polarity opposite to the toner polarity during development (positive polarity) is applied to the discharge wire 403 of the first charger 401 by a voltage-adjustable power source DI. Reference numeral 404 denotes a second charger formed in the same structure as the first charger 401, and the discharge opening surface of the first charger 401 is opposed to the discharge opening surface of the first charger 401. It is arranged above 401. This second charger 40
4, the voltage-adjustable power supply D is connected to the wire 405.
In step 2, a high voltage having the same polarity (negative polarity) as the toner polarity during development is applied. Preferably, the absolute values of the high applied voltages for both the first charger 401 and the second charger 404 are 4.5 kV to 7.5 kV-C'.

Note that the polarity of the high voltage 6 applied to the first charger 401 and the second charger 404 may be a high voltage having a polarity opposite to the above polarity. That is, these high voltage polarities are selected so that the difference between the charging potential on the front or back surface of the transfer material and the charging potential on the surface of the roller of the fixing device in contact with each surface is small.

Reference numeral 273 denotes a second conveyor belt formed in the same structure as the first conveyor belt 271, and the transfer material passed between the pair of upper and lower first chargers 401 and second charger 404. is conveyed to the fixing device 28 while being brought into close contact with the second belt member 273 & rotating in the direction of arrow B by the suction force of the suction unit 274.

Next, the operation of this embodiment will be explained. separation nail,
To 236! 9 distance sh* from '@'4r5'''°
The toner T on the transfer material 2o in ii is shown in FIG. 6(C).
As shown in FIG. 2, the transfer material 200 has no electric charge or has a slight negative polarity charge, while the electric charge on the front and back surfaces of the transfer material 200 has disappeared or been reduced by a considerable amount. In which state the transfer material 20 passes between the first charger 401 to which a voltage of positive polarity is applied and the second charger 404 to which a voltage of negative polarity is applied, as shown in FIG. As shown, a negative charge is attached to the surface of the transfer material 200 having the toner A, and the toner T is again charged to the negative (C) polarity, and a spreading (A) charge is attached to the back surface of the transfer material 20.

That is, the transfer material 20 having the toner image is charged by the opposing first chargers 401 that apply voltages of mutually different polarities.
By passing the toner T between the transfer material 20 and the second charger 404, the toner T can be reliably held on the transfer material by electrostatic force with a strong force, and it can also be applied to areas of the transfer material 20 where there is no toner. Because of the presence of negative H charges, no large potential difference is generated between the toner area and its surroundings, so toner scattering is less likely to occur.

The range of the surface potential of the transfer material after being charged is determined by the first charger 40.
When the voltage applied to the first and second chargers 404 is positive and negative, respectively, the surface side (toner side) is H2oov N
hsoov, A side (-)3200V-(A) soo
It is preferable to set it to v.

Therefore, even if the transfer material is conveyed to the fixing device 28 in such a state and fixed under pressure and heat, good image quality can be obtained because the toner does not scatter.

By the way, in a low humidity environment, when paper is used as a transfer material, the resistance becomes high and the front and back sides of the charged paper are charged to 1100QV or more or +tooov or more, and the difference with the surface potential of the fixing device roller increases. Toner scattering may actually increase. On the other hand, in a high humidity environment, the resistance of L becomes low, and after charging, the front and back sides of the paper are charged only to -toov or less or +100V or less, and a sufficient charging effect may not be exhibited.

In such a case, the high voltage applied to the first charger 401 and the second charger 404 is controlled in a low humidity environment, a normal humidity environment, and a high humidity environment to increase the charging potential of the transfer paper. It may be adjusted so that it falls within the range described above.

In addition, if a synthetic resin sheet for O, H, P, (over head, glow projector) is used as the transfer material, and stone has a higher resistance than paper, the charger 401 and the second
The high voltage applied to the charger 402 may be controlled to be lower than that for paper.

Further, a first charger 401 or a second charger 404
A large number of grid wires may be stretched across the discharge openings, and a bias voltage may be applied to these wires to control the surface potentials of the front and back surfaces of the transfer material to a predetermined potential. It is preferable to apply this charging device to the first charging device 401 because the charging potential control effect is higher when the charging device is closer to the transfer material.

Further, the voltages applied to the first charger 401 and the second charger 404 can be controlled according to various environmental conditions or transfer material materials by manual adjustment or by using a known sensor and control circuit. It may also be possible to automatically deposit the money.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to prevent toner from scattering on the transfer material after separation from the transfer material support, and it is possible to obtain a fixed toner image of good image quality. This is particularly effective in preventing toner scattering, which tends to occur when a thick toner layer is formed by overlapping a plurality of toner layers as in a full-color image.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of essential parts showing an embodiment of the painting house forming apparatus according to the present invention, and FIG. tJrJ2 is a plan view of the band 11 in FIG.
Figure 3 is a schematic diagram showing the state of charge on the front and back sides of the transfer material, Figure 4 is a sectional view of a conventional color electrophotographic copying machine, Figure 5 is a perspective view of its transfer drum, and Figure 6 ('J t ( B) *(
2) is a schematic diagram showing the state of charge on the transfer material and the transfer material carrying sheet by conventional separation charge removal, respectively. 1: Photosensitive drum 2: Axis 4: Document platen 5: U/Pro: 1st scanning Mirror 7: second scanning mirror,
13: L/7″9: No. 36'-1O: Color separation filter ll: Ki 4 mirror 13: AC release door 2.'
; 14: ptH light 2 ring 15: primary charging discharge 8λ 16 = secondary 1; charging discharge/.

Claims (1)

[Claims] After the toner image visualized on the latent image carrier is corona-transferred to the transfer material carried on the transfer material-bearing sheet, the transfer material is separated from the transfer material-bearing sheet while performing corona charge removal at the separation position, and then fixed. In both image forming apparatuses that form a fixed toner image on the transfer material by conveying the toner through the fixing means, a pair of opposing polarities are provided on the transfer material conveyance path leading to the fixing means, and the front and back surfaces of the transfer material are charged to opposite polarities. An image forming device characterized by being provided with a corona discharger.