JPH02230263A - Both-surface image forming device - Google Patents

Abstract

PURPOSE:To increase a toner fixing speed by setting the amount of liquid with which transfer paper is impregnated to less than a specific amount when a wet type toner image is transferred to the transfer paper, and forming images on both surfaces of the transfer paper without fixing any image between respective transfer parts. CONSTITUTION:First and 2nd wet type developing devices 12 and 22 are roller type developing devices and toner migrates on the photosensitive surfaces of photosensitive drums 11 and 21 according to electrostatic potentials to form visible images. Remaining liquid is squeezed by rollers 12' and 22' after development so that toner images are left on the photosensitive body surfaces, thereby making toner image transfer to transfer paper 6 ready. The images of toner are transferred to the paper surfaces through liquid films on the transfer paper surfaces with a transfer electric field to perform a transfer process. Here, the attraction amount of liquid developer at the time of the transfer is set to about <=300mg for transfer paper 6 of size A4 having no toner image. Consequently, the transfer paper 6 is impregnated with the liquid developer speedily right after the transfer and the toner images can be stuck strongly with ease.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a laser printer having a double-sided image forming mode;
The present invention relates to an electrophotographic apparatus such as a copying machine, and particularly to a double-sided image forming apparatus employing a wet developing method as an image forming means.

[Conventional technology]

An image forming apparatus related to this type of double-sided image forming apparatus is one in which a toner image formed by an image forming section having two dry developing devices is transferred to both sides of a transfer paper (Japanese Patent Application Laid-open No. 63-1
No. 42365), which has two dry developing devices and instead of omitting the intermediate fixing between the two developments, reverses the toner polarity of the toner image in one image forming section (Japanese Patent Application Laid-open No. 6
3-197979), and one with an intermediate fixing device between two image forming sections (Japanese Patent Application Laid-open No. 17736/1983).
, which is equipped with one image forming section and two transfer sections, and the transfer paper is reversed between the transfer sections, and after both sides are transferred, it is fixed once (Japanese Patent Laid-open No. 5
3-112738), a wet development method is used, and a reversing roller that scrapes off excess developer on the photoreceptor and a pressure blade that controls the amount of developer on this roller are provided, and the relative relationship between the reversing roller and the photoreceptor blade is There is a known method (Japanese Patent Publication No. 54-34541 f[!) in which the amount of developer is controlled by speed, gap, blade contact (1), surface smoothness of a reversing roller, etc.

[Problem to be solved by the invention]

In the above-mentioned conventional technologies, in those that use an intermediate fixing device, the temperature of the image forming section increases and the sensitivity of the photoreceptor becomes unstable, and in those that reverse the toner polarity, the process is complicated and the toner There is a problem that the material deteriorates.

In addition, in the case where the transfer paper is reversed between developing devices,
There are problems in that reliability during high-speed processing deteriorates and toner scatters.

In other words, in conventional image forming apparatuses capable of double-sided copying,
After transferring and fixing one side of the transfer paper, turn the transfer paper over and
The common method is to return the paper to the buffer tray for double-sided copying, refeed the paper from this tray, and copy on the other side.
This takes a long processing time.

When processing at high speed, there is a problem that immediately after heat fixing is performed on one side of the transfer paper, the photoconductor in contact with the heated transfer paper is heated and the sensitivity becomes unstable when transferring to the opposite side.

In the above-mentioned Japanese Patent Application Laid-open No. 53-112738, transfer units are provided at two locations for one photoreceptor, and the transfer paper is reversed from front to back while being conveyed between the two transfer units, so that intermediate fixing is omitted and both sides are printed. A method of temporary fixation is disclosed. Toner images transferred using dry toner do not undergo intermediate fixation, so the toner may be scattered due to vibrations of the paper due to the reversal operation of the transfer paper or the influence of the electric field during the next transfer, resulting in deterioration of image quality.

This problem depends on paper quality and environment, and the versatility of transfer paper is lost.

5, 6, and 7 are main part configuration diagrams illustrating an example of a conventional double-sided copying machine that does not invert the transfer paper (no inversion of the transfer paper). 63-14236
5 is a configuration diagram of the copying machine disclosed in No. 5, in which 51 is a feeding section that accommodates a large number of transfer sheets and feeds them one by one in response to a feeding signal, and 52 is a discharge section that accommodates transferred copies. , 53 is a transfer paper conveyance path, 54 and 55 are a first image forming means and a second image forming means, respectively, 56 is a fixing means (heated fixing roller), and 57 is between the first and second image forming means 5455. Arranged temporary fixing means (intermediate fixing means...pressure fixing roller)
, 58 is a document reading section. FIG. 6 is a block diagram of the copying machine disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 60-191281, in which 61 is a stainless steel glass, 62 is a document, 63 is a first optical system, 64 is a second optical system, 65 is a first transfer section consisting of a first photosensitive drum 613; 66 is a second photosensitive drum 63;
3, 617 is a transfer paper conveyance path, 618
638 is the first fixing section (intermediate fixing section), 638 is the second fixing section, 6
37 is a paper ejection section. Figure 7 shows the above-mentioned Japanese Patent Application Laid-Open No. 60-177.
361 is a configuration diagram of a copying machine disclosed in Publication No. 361, in which 7l is a first photosensitive drum, 72 is a second photosensitive drum, 73 is a document feed tray, 74 is a document discharge tray, 75 is a transfer paper feed section, 76 is a transfer paper discharge section, 77 is a first fixing section (intermediate fixing roller), 78 is a second fixing section, 79 is a transfer paper intermediate discharge tray, and 80 is an ADF.

In these conventional technologies, each transfer part (photosensitive trem)
Since a fixing device (intermediate fixing section) is installed between the
During high-speed processing, as described above, the transfer process at the next transfer section is performed before the heat in the intermediate fixing section is dissipated, so the temperature of the photosensitive drum at the second transfer section rises and the transfer sensitivity becomes unstable. There is a problem with becoming.

As described above, in a method in which toner images are sequentially transferred to both sides of a transfer paper and a fixing section is provided in the middle, fixing devices are required in two places, and in addition to the above-mentioned problems, the conveyance path of the transfer paper is becomes long, making it difficult to downsize the entire image forming apparatus and increasing power consumption.

Furthermore, when copying both sides of a left-right spread document, there is a problem of consistency (registration) between the front and back images.
The intermediately fixed transfer paper shrinks due to dehydration due to heating,
A magnification error occurs in the paper making direction. Shrinkage caused by heating and dehydration recovers rapidly, but it does not recover in a short time of 1 second or less during transport between image forming sections, and even if you try to correct the magnification error by changing the magnification, the vertical Due to differences in grain, cross grain, paper quality, thickness, and moisture content depending on the environment,
It is not possible to uniquely determine the correction value.

In addition, the above-mentioned Japanese Patent Application Laid-Open No. 1986-63 which omitted the inversion of the transfer paper and the intermediate fixing.
- The method described in Publication No. 197979 attempts to solve the above-mentioned problems of the prior art, but in order to prevent image quality deterioration caused by scattering of toner due to the application of an electric field in the subsequent transfer section, the polarity of the toner is changed. However, as the device is operated, the amount of charge and polarity of the toner increases.
This results in unstable development, leading to deterioration of the developing material. In order to avoid this deterioration of the developer material, it is possible to reverse the charge polarity of the photoreceptor and the toner from the beginning, but this requires two toner supply systems, which is not preferable from the point of view of maintenance and service.

It is an object of the present invention to provide a double-sided image forming apparatus that solves the above-mentioned conventional problems, eliminates transfer paper reversal and intermediate fixing, and also solves new problems such as image bleeding and show-through due to the omission of intermediate fixing. It is about providing.

[Means to solve the problem]

The above purpose is to install a photoreceptor and a charging device on both sides of the conveyance path of the transfer paper. In a double-sided image forming apparatus, which includes image forming sections each having a developing device and a cleaning device, and sequentially transfers toner images formed in each image forming section onto both sides of a transfer sheet being conveyed to create a double-sided copy. , the image forming means provided in the image forming section is a wet developing type developing device, and the transfer of the wet toner image to the transfer paper is performed using a developer impregnated into the transfer paper without a toner image equivalent to A4 size. The liquid volume is 300μ or less,
This is achieved by forming images on both sides of the transfer paper without fixing between the transfer sections.

[Effect]

The development method of the developing device is a wet development method with small particle size, resulting in high resolution and fast toner fixation speed.Since there is no intermediate fixing, the temperature rise of the next stage photoreceptor is small, making the entire device compact. , it is easy to save power.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram illustrating an embodiment of a double-sided image forming apparatus according to the present invention, in which 1 is a transfer paper feeding IIE roller, 2 is a roller brake, 3 is a pull-out roller, and 4 is a transfer paper feed roller 6 Dancer roller for tension and tracking adjustment, 5 is a guide roller, 6 is a transfer paper, 7 is a direction change roller, 8 is a drive roller, 9 is a winding roller, 0 is a first image forming section, 11 is a first photosensitive member 12 is a first wet developing device, 13 is a first cleaning device, 14 is a first main charging device, 15 is a first local static elimination exposure section, 16 is a first whole surface static elimination exposure section, and 17 is a first cleaning device. 1 an exposure optical system, 18 a first transfer charger, 20 a second image forming section, 21 a second photosensitive drum, 22
2 is a second wet developing device; 23 is a second cleaning device;
4 is a second main charger, 25 is a second local static elimination exposure unit, 26 is a second entire static elimination exposure unit, 27 is a second exposure optical system, 28 is a second transfer charger, 30 is a heating device for fixing, 3l is a heater roller.

In the figure, this embodiment is a wet-development type high-speed double-sided copying device using a roll of transfer paper (transfer web), and the transfer paper 6 is pulled out from the paper feed roll 1 braked by a roller brake 2. Roller 3, dancer roller 4.
Transfer charger 1 of first image forming section 10 via guide roller 5
It comes into contact with the first photoreceptor drum l1 at position 8.

The transfer paper 6 is transferred from the first image forming section lO to the second transfer charger 28 of the second image forming section 20 via the direction changing roller 7.
After contacting the photosensitive drum 21 and passing through the second image forming section 20, the sheet is conveyed at a constant speed by the drive roller 8 so as to pass through the heat fixing device 3o and reach the take-up roll 9.

Note that, if necessary, a cutter such as a rotary ivy may be provided downstream of the drive roller 8 to cut it into a predetermined size.

Although not shown, if the stretched transfer paper deviates in the width direction of the conveyance path or its speed changes, the amount of displacement is detected by an appropriate sensor, and correction control is automatically performed using this detection signal. .

An optical system that projects an original image, or an LE that writes an image using a digital image signal. The D array or laser optical system is provided at the position 17.27, but the details are not directly related to the present invention, so the explanation will be omitted.

The developer used in the wet developing device is a petroleum solvent (Iso
par) is used to disperse the charged resin solid component as a toner.

The first and second wet-type developing devices 12 and 22 shown in FIG. 1 are roller-type developing devices, and toner migrates onto the photosensitive surface of the photoreceptor drum according to the electrostatic potential to form a visible image. After the development is completed, roll the roller l2'',
22" to scrape off (squeeze) excess liquid and prepare for toner image transfer onto transfer paper.

After squeezing the excess liquid, the toner image concentrated in the liquid film on the photoreceptor surface is transferred onto the paper surface by a transfer electric field via the liquid film between the transfer paper surface and the transfer process is executed. .

By the time the transfer paper is separated from the photoreceptor surface, the developer has soaked into the transfer paper, and the toner image on the transfer surface strongly adheres to the transfer paper, making it susceptible to large shocks, vibrations, and light contact with objects. Then it won't flow.

Therefore, toner image diffusion does not occur during high-speed operation.

The most important thing in high-speed double-sided transfer using wet development is controlling the amount of developer adsorbed to the paper during transfer, that is, 1F! ．． This is the squeeze control amount on the light surface. If a large amount of developer solvent (lsopar) is adsorbed,
Bleeding occurs in the image during the subsequent transfer process, and even on dry double-sided copy paper, the image on the other side appears faint, making the copy extremely difficult to read.

Transfer paper has its thickness and degree of lipophilicity. There are differences in paper quality such as transparency, and it is not possible to unambiguously determine the developer adsorption star during transfer.
(Q title) copy paper) size A4 without toner image
With transfer paper, duplex copying is good at 120cm or less,
If it is approximately 300 square meters or less, the copy image will be of good quality.

Note that as the number of image areas (parts of toner) increases, the amount of developer adsorbed also increases.

Bleeding images can be evaluated using a blank copy, a copy without toner image, and a squeeze setting with liquid ■. Used developer has a large amount of adsorption and is prone to bleeding. The adsorption amount of the developer in this image evaluation is calculated by weighing the image immediately after transfer and after complete drying, taking into account the moisture content due to environmental humidity. The amount of adsorbed liquid can be controlled by controlling the amount of liquid on the photoreceptor surface by controlling the rotation speed of a squeeze roller (scraping roller).

FIG. 2 is a block diagram of a double-sided image forming apparatus illustrating another embodiment of the present invention, and is an example of a copying machine using cut sheets as transfer paper.

In the figure, the same symbols as in Figure 1 correspond to the same parts,
33 is a paper feed roller, 34 is a first separation belt, and 35 is a second
Separation belt, 36 transfer paper conveyance belt, 60 transfer paper,
61 is a paper feed tray, and 90 is a paper discharge tray.

The configuration of this embodiment includes a first image forming section 10 and a second image forming section 20.
A transfer paper separation bell l-34.35 is provided in each of the
Separation of the transfer paper from the photoreceptor during high-speed transfer is ensured, and a transfer paper conveyance belt 36 is provided between the first image forming section 10 and the second image forming section 20 to convey the transfer paper. Is going.

In wet development method 2, it is difficult to separate the transfer material from the photoreceptor regardless of the type of transfer paper, but this separation is particularly difficult with the roll material of the above embodiment. In this example, the separability is improved by using a cut sheet.

In addition, in this embodiment, since the transfer corona (transfer corona) can completely cover the charged area of the transfer charging device and tightly wrap the transfer paper around the photoreceptor drum, there is no reduction in resolution due to gap transfer, and even wet development can be performed at minute intervals. It is possible to prevent the toner from scattering around the image.

FIG. 3 is a configuration diagram of a developer scraping mechanism that constitutes a wet developing section installed around the light-absorbing drum of the image forming section,
110 is a photoreceptor drum, 120 is a scraping roller (R
R roller), 121 is a scraper, and 130 is a toner image.

In the figure, the RR roller 120 is the photoconductor drum 110.
The photosensitive drum 1 is rotated in a direction opposite to the direction of rotation of the photosensitive drum 1.
They are arranged at minute intervals on the surface of 10.

The RR roller 120 has a scraper 1 in contact with its surface.
21 is provided to remove the developer attached to the surface of the RR roller 120.

Excess developer is scraped off from the surface of the photoreceptor drum 110 due to the relative speed difference between the photoreceptor drum 110 and the RR roller 120, the gap between the photoreceptor drum 110 and the RR roller 120, the surface smoothness of the RR roller, and scraper 12
It is controlled by the amount of developer removed from the surface of the RR roller 121 according to No. 1.

By setting each of the control factors described above, it is possible to precisely control the developer that adheres to the surface of the photoconductor drum 120.

FIG. 4 is a characteristic diagram illustrating the change in the amount of developer adhering to the surface of the photoreceptor drum when the rotational speed of the scraping roller is changed, and the horizontal axis is the rotational speed of the RR roller (rp
m), and the vertical axis shows the amount of developer attached to the transfer paper (blank copy) immediately after double-sided transfer to A4 size transfer paper (blank copy).
■).

In the same figure, as the rotational speed of the RR roller is increased, the amount of developer solution adhering to the surface of the photoreceptor gradually decreases, and then
There is a tendency to increase.

If the adhesion interval exceeds 300 cm, the quality of the transferred image will be extremely degraded, so this area (defective area) is not suitable.

The area where the transferred image is best is when the number of rotations of the RR roller is 3.
The rotation speed is 20 to 53 Qrpm, but if the rotational speed is such that the amount of adhesion is 300 cm or less, an image with less show-through, image blurring, and blurring of the transferred image can be obtained.

〔Effect of the invention〕

As explained above, according to the present invention, by employing the wet developing method in the developing device, (1) the particle size of the wet toner is approximately 1/1/2 that of the dry toner;
10, which significantly improves image quality and resolution.

(2) Can be fixed with slight evaporation of solvent (Isopar),
Contributes to power saving.

(3) Immediately after transfer, the developer rapidly soaks into the transfer paper, and the toner image easily and firmly adheres to it.

(4) Since no intermediate fixing is required, power consumption can be reduced and the device can be made more compact, and the rise in temperature of the photoconductor can be suppressed, resulting in less temperature rise inside the machine.

It is possible to overcome the drawbacks of the prior art and provide a double-sided image forming apparatus with excellent functionality.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of essential parts of an embodiment of a double-sided image forming apparatus according to the present invention, FIG. 2 is a block diagram of a double-sided image forming apparatus explaining another embodiment of the present invention, and FIG. A configuration diagram of the developer scraping mechanism that constitutes the wet developing section installed around the photoconductor drum in the image area. Figure 4 shows the developer adhering to the surface of the photoreceptor drum when the rotational speed of the scraping roller is varied. Characteristic diagrams explaining changes in liquid volume, Figures 5 and 6,
FIG. 7 is a diagram illustrating a main part configuration of an example of a conventional double-sided copying machine. 1...Transfer paper feed roller, 2...Roller brake, 3...Pull-out roller, 4...Dancer roller for tension and tracking adjustment of transfer paper, 5...
... Guide roller, 6 ... Transfer paper, 7 ... Direction changing roller, 8 ... Drive roller, 9 ... Winding roller, ■0 ... First image forming section , 1l...first photoreceptor drum, 12...first wet developing device, 13...
...First cleaning device, 14...First main charging device, 15...First local static elimination exposure section, 16... First entire surface static elimination exposure section, l7... First exposure optical system, 18
...First transfer charger, 20...Second image forming section,
21... Second photoconductor drum, 22... Second wet developing device, 23... Second cleaning device, 24...
...Second main charger, 25...Second local charge elimination exposure section, 26...Second entire charge elimination exposure section, 27...Second
n-light optical system, 28...second transfer charger, 30...
. . . Heating device for fixing, 31 . . . Heater roller. Figure 5B

Claims (1)

[Claims] Image forming sections each consisting of a photoreceptor, a charging device, a developing device, and a cleaning device are provided on both sides of the transfer paper transport path, and the toner images formed in each image forming section are transferred to both sides of the transfer paper being transported. In a double-sided image forming apparatus that creates a double-sided copy by sequentially transferring images to a sheet of paper, the image forming means provided in the image forming section is a developing device of a wet type development type, and the transfer of this wet toner image to a transfer paper is performed by:
A double-sided image characterized in that when there is no toner image equivalent to A4 size, the amount of developer impregnated into the transfer paper is 300 mg or less, and images are formed on both sides of the transfer paper without being fixed between each transfer section. Forming device.