JPH04278966A - Wet type electrophotographic copying machine - Google Patents

Abstract

PURPOSE:To improve fixation property in the case that toner condensed and scattered by high-boiling solvent and low-boiling solvent is used. CONSTITUTION:A microcomputer 30 counts the number of copied sheets and detects the concentration of developer 24 in a developing tank 23 based on the detection signal of a CdS sensor 26 at the same time. Besides, it controls the replenishment of a toner bolt 21 and a developer bolt 22 so that the quantity of the toner and the developer is gradually made thin to the degree of 35g/780g (at starting time), 33.75g/780g (after thousand and five hundred sheets are copied), 32.5g/780g (after five thousand sheets are copied), 31.25g/780g (after seven thousand and five hundred sheets are copied) and 30g/780g (after ten thousand sheets are copied) every two thousand and five hundred sheets until ten thousand sheets from the starting time of copying.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet type electrophotographic copying machine which develops an electrostatic latent image using toner concentrated and dispersed using a high boiling point solvent and a low boiling point solvent.

0002

[Prior Art] In general, developers used in wet-type electrophotographic copying machines are made by dispersing colorants, resins, charge control agents, etc. in a highly insulating liquid. Consists of negatively charged toner particles. The characteristics of the copying process and recorded images using this type of wet developer are: 1. High resolution images are obtained due to development with fine particle toner; 2. 3. Excellent gradation reproducibility and good photographic reproducibility; 3. 4. Image fixation is easy. The developing and fixing sections are compactly designed, but there are problems in terms of safety.

[0003] Therefore, the present inventors developed a wet-type electrophotographic copying method in which an electrostatic latent image is developed using a toner concentrated and dispersed with a high-boiling point solvent and a low-boiling point solvent in order to improve safety, instead of the above-mentioned developer. developed a machine.

0004

[Problems to be Solved by the Invention] However, the developer in which the toner is concentrated and dispersed using the above-mentioned high boiling point solvent and low boiling point solvent initially has a low boiling point as a developer, as shown in FIG. As the amount of the boiling point solvent increases, there is a problem that the fixing performance gradually deteriorates.

In view of the above-mentioned conventional problems, it is an object of the present invention to provide a wet-type electrophotographic copying machine that can improve fixing performance when using toner concentrated and dispersed with a high-boiling point solvent and a low-boiling point solvent. purpose.

[0006]

[Means for Solving the Problems] In order to achieve the above object, a first means includes an image carrier for forming an electrostatic latent image by exposure, and a pre-charged surface on the image carrier before exposure. charging means for developing the electrostatic latent image on the image carrier with a developer having toner concentrated and dispersed with a high boiling point solvent and a low boiling point solvent; The present invention is characterized by comprising a control means for controlling the concentration to become thinner.

The second means includes an image carrier for forming an electrostatic latent image by exposure, a charging means for pre-charging the image carrier before exposure, and concentration using a high boiling point solvent and a low boiling point solvent. A developing device that develops the electrostatic latent image on the image carrier with a developer containing dispersed toner, and a control device that controls the charging potential of the charging device to decrease as the number of copies increases. It is characterized by having the following.

The third means includes an image bearing member for forming an electrostatic latent image by exposure, a charging means for charging the image bearing member in advance before exposure, and concentration using a high boiling point solvent and a low boiling point solvent. A developing means for developing the electrostatic latent image on the image carrier with a developer having dispersed toner; and a control means for controlling the developing bias voltage of the developing means to increase as the number of copies increases. It is characterized by having what it has.

[0009]

[Operation] The first means has the above-mentioned structure, so that the developer initially has a low boiling point, and when the amount of the high boiling point solvent increases due to copying running, the concentration of the developer becomes thinner and the toner does not reach the image carrier. The amount of adhesion becomes constant, therefore,
Fixing properties can be improved.

[0010] The second means has the above-mentioned structure, and when the developing solution initially has a low boiling point and the amount of high boiling point solvent increases due to copying running, the charging potential on the image carrier decreases and the image carrier The amount of toner adhering to the toner becomes constant, and therefore fixing performance can be improved.

The third means is that the developing solution initially has a low boiling point, and when the amount of high boiling point solvent increases due to copying running, the developing bias voltage increases and the amount of toner adhering to the image carrier remains constant. Therefore, fixing performance can be improved.

0012

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of main parts showing an embodiment of a wet-type electrophotographic copying machine according to the present invention, FIG. 2 is a front view showing a density sensor used in the developing tank of FIG. 1, and FIG. A circuit diagram showing the circuit configuration of the concentration sensor, FIG. 4 is similar to FIGS. 2 and 3.
FIG. 5 is a graph showing the characteristics of the high boiling point solvent during copy running in the developing tank of FIG. 1. FIG. 6 is a graph showing the rank of fixability.
FIG. 7 is a sectional view showing a schematic configuration of an embodiment of a wet-type electrophotographic copying machine according to the present invention, and FIG. 8 is an enlarged sectional view of the electrophotographic section of FIG. 7.

First, the structure of the wet-type electrophotographic copying machine according to the present invention will be explained with reference to FIGS. 7 and 8. In FIG. 7, the image of the original is illuminated by a halogen lamp (not shown), as in a normal copying machine, and includes a first mirror 1, a second mirror 2, a third mirror 3, a through lens 4, and a fourth mirror 4a.
, and is exposed onto the photosensitive drum 5. Figure 8
The photosensitive drum 5 rotates clockwise, and the surface of the drum 5 is positively charged by a charger 6 before exposure, and then the electrostatic latent image of the original image is removed by an eraser 7 after the charged potential in the non-image area is removed. is formed in the image area.

Negatively charged toner is adhered to the area on the photosensitive drum 5 where the electrostatic latent image is formed by the two developing rollers 8 and 9 to form a visible image, and then the excess is removed. The developer is removed by the squeeze roller 10. The toner on the photosensitive drum 5 is transferred to the front surface of the paper P by the transfer charger 11 applying a negative charge to the back surface of the paper P. The remaining toner on the photosensitive drum 5 is removed by a cleaning roller 12 and a cleaning blade 13, and the remaining toner is also removed by a static elimination lamp 14 in preparation for the next copying.

Note that the paper P for transferring the toner image is as follows:
As shown in FIG. 7, the paper is set in the paper feed cassette 15 in advance, is taken in by the paper feed roller 16, etc., and is taken in by the registration roller 17.
The photosensitive drum 5 is conveyed so as to match the toner image on the photosensitive drum 5, and the toner image is transferred by the transfer charger 11. This paper P is then separated from the photosensitive drum 5 by a separator roller 18 and a turn belt 19, and after the toner image is fixed by a fixing device 20, it is discharged.

Next, the detailed structure and operation of this embodiment will be explained with reference to FIGS. 1 to 6. In FIG. 1, a toner bottle 21 contains toner with a toner solid content of 25% and an isopa (insulating liquid) content of 75%. is 1:7:2
It is. Note that Isopa, a conventional wet type developer, contains 100% of the low boiling point solvent H. Isopa containing 100% low boiling point solvent H is stored in the developer bottle 22, and the toner bottle 2
The developer tank 23 is replenished together with the toner in the developer tank 23 under the control of the microcomputer 30, and the developer 24 is supplied to the aforementioned developer rollers 8 and 9.

A lamp 25 as shown in FIG. 2 and a CdS sensor 26 that receives the amount of light from the lamp 25 via the developer 24 are arranged inside the developer tank 23. Therefore, with the circuit configuration shown in FIG. 3, the CdS sensor 2
The concentration of the developer 24 in the developer tank 23 can be detected by the detection signal No.6. In this case, as the toner concentration of the developer 24 increases, the light transmittance decreases, so as shown in FIG.
is inversely proportional to the toner concentration.

Here, when the toner in the developer 24 at the start of copying is 35 g and the developer is 780 g, the high boiling point solvents L and M in the developer 24 are 3% (=35×0.75×
0.9/780). Conventionally, when a copying run is performed using this developer 24 at an image ratio of 7%, the ratio of high boiling point solvents L and M increases in direct proportion until 10K sheets reach 11%, as shown in FIG. It was found that the number does not increase after 10K sheets. In this case, as shown by the solid line in Figure 6,
The fixability rank was rank 4, which is an acceptable rank, at the start of copying, but it decreased to rank 3, which is the lowest standard, after 5K copies, and decreased to rank 2, which is a failure rank, after 10K copies.

In this embodiment, as shown in FIG. 1, the microcomputer 30 counts the number of copies and also detects the concentration of the developer 24 in the developer tank 23 based on the detection signal of the CdS sensor 26, and from the start of copying. The amount of toner and developer is 35g for every 2.5K sheets up to 10K sheets.
/780g (at start), 33.75g/780g (2.
32.5g/780g (after 5K copies), 31.25g/780g (after 7.5K copies), 3
The replenishment of the toner bottle 21 and developer bottle 22 is controlled so that the toner bottle 21 and the developer bottle 22 are gradually thinned to 0g/780g (after 10K sheets of copying). In this case, as shown by the broken line in FIG. 6, the fixability ranks range from rank 3.5 to rank 4, and therefore, the fixability can be improved.

The microcomputer 30 has a battery-backed memory for counting the number of copies, and this count value is reset, for example, when a service person replaces the developer 24. As shown in FIG. 9, after the developer 24 is replaced, for example, 24
When 99 sheets are copied, the output voltage of the CdS sensor 26 is taken in, and when the output voltage is 2.60V or more, the developer 24 is replenished, and when the output voltage is 2.40V or less, the supply is stopped. Similarly, 4999 pieces, 7499 pieces, 9999 pieces, 10000 pieces
If more than one sheet is copied, 2.85V and 3.10V respectively.
, 3.35V, 3.60V or more, replenish developer 24, 2.65V, 2.90V, 3.15V, 3.40
When the voltage drops below V, replenishment will be stopped. Note that the reason why a difference is set between the replenishment start voltage and the replenishment stop voltage is to prevent malfunctions due to noise contained in the detection signal of the CdS sensor 26.

Next, a second embodiment will be explained. 10 is a block diagram showing the main parts thereof, FIG. 11 is a graph showing the relationship between the charging potential of the photosensitive drum 5 in FIG. 10 and the amount of toner adhesion, and FIG. 5 is a graph showing the relationship between the charging potential of the drum 5. FIG. In this embodiment, as shown in FIGS. 10 and 11, the microcomputer 40 counts the number of copies and makes one copy from the start of copying.
For every 2.5K sheets up to 0K sheets, the charged potential of the photosensitive drum 5 changes to 1350V (at the start), 1300V (after copying 2.5K sheets), 1250V (after copying 5K sheets), and 1200V (
The output current of the high-voltage power source 41 is controlled so as to be 1150V (after copying 7.5K sheets) and 1150V (after copying 10K sheets).

That is, the amount of toner adhering to the photosensitive drum 5 is directly proportional to the charging potential (and the characteristics and rotational speed of the photosensitive drum) as shown in FIG. 11, and the charging potential of the photosensitive drum 5 is as shown in FIG. As shown, since it is directly proportional to the output current of the high voltage power source 41, fixing performance can be improved by decreasing the output current of the high voltage power source 41 as the number of copies increases. As shown in FIG. 13, the specific control of the microcomputer 40 is such that the output current of the high voltage power supply 41 is 365 μA (0 to 2499 sheets), 350 μA (25
00-4999 sheets), 340 μA (5000-7499
), 325 μA (7500 to 9999 sheets), 310 μA
(10,000 sheets or more). In this case as well, as shown by the broken line in FIG. 6, the fixability ranks are in the range of rank 3.5 and rank 4, and therefore, the fixability can be improved.

Next, a third embodiment will be explained. FIG. 14 is a block diagram showing the main parts thereof, and FIG. 15 is a graph showing the relationship between the developing bias voltage and the amount of toner attached to the photosensitive drum 5. In this embodiment, as shown in FIGS. 14 and 15, the microcomputer 42 controls the developing bias voltages of the developing rollers 8 and 9 to be 150 V (at the start), 200 V (2.
After copying 5K sheets), 250V (after copying 5K sheets), 300V
The output current of the high-voltage power supply 43 is controlled to be 350V (after copying 7.5K sheets) and 350V (after copying 10K sheets).

That is, the amount of toner attached to the photosensitive drum 5 is proportional to the developing bias voltage of the developing rollers 8 and 9 (and the characteristics and rotational speed of the photosensitive drum), as shown in FIG. Since the output current of the high voltage power supply 43 is proportional to the output current of the high voltage power supply 43, as the number of copies increases, the output current of the high voltage power supply 43 increases.
By increasing the output current of No. 3, fixing performance can be improved.

In this embodiment, since the developing bias voltage is increased, there is a risk that toner will not adhere at all to areas of the electrostatic latent image on the photosensitive drum 5 where the potential is low. For example, toner adheres thinly to the 180V region on the photosensitive drum 5 when the developing bias voltage is 150V, but does not adhere at all when the developing bias voltage is 200V. Therefore, in this embodiment, the microcomputer 4
2, when setting the developing bias voltage to 200V (after copying 2.5K sheets), 250V (after copying 5K sheets), 300V (after copying 7.5K sheets), or 350V (after copying 10K sheets), the original illumination The voltages applied to the halogen lamp 45 for use are 1.5V (after copying 2.5K sheets), 3V (after copying 5K sheets), 4.5V (after copying 7.5K sheets), and 6V (after copying 10K sheets), respectively. The lamp regulator 44 is controlled to decrease the amount. Therefore, in this example as well,
As shown by the broken line in Figure 6, the fixability rank is 3.5.
and is in the range of rank 4, and therefore, fixing performance can be improved.

[0026]

As explained above, the invention according to claim 1 provides an image bearing member for forming an electrostatic latent image by exposure, and a charging means for charging the image bearing member in advance before exposure. ,
a developing means for developing the electrostatic latent image on the image carrier with a developer having toner concentrated and dispersed by a high boiling point solvent and a low boiling point solvent; Since the image forming apparatus includes a control means for controlling the image forming apparatus, the concentration of the developer becomes thinner and the amount of toner adhering to the image bearing member becomes constant, thereby improving fixing performance.

The invention according to claim 2 provides an image carrier for forming an electrostatic latent image by exposure, a charging means for pre-charging the image carrier before exposure, a high boiling point solvent and a low boiling point solvent. a developing means for developing the electrostatic latent image on the image carrier with a developer having toner concentrated and dispersed by the above; and a control means for controlling the charging potential of the charging means to decrease as the number of copies increases. As a result, the charging potential on the image bearing member is reduced, and the amount of toner adhering to the image bearing member becomes constant, thereby improving fixing performance.

The invention according to claim 3 provides an image carrier for forming an electrostatic latent image by exposure, a charging means for charging the image carrier in advance before exposure, and a high boiling point solvent and a low boiling point solvent. a developing means for developing the electrostatic latent image on the image carrier with a developer having toner concentrated and dispersed by the above; and a control means for controlling the developing bias voltage of the developing means to increase as the number of copies increases. As a result, the developing bias voltage becomes high and the amount of toner adhering to the image bearing member becomes constant, thereby improving fixing performance.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of main parts showing an embodiment of a wet-type electrophotographic copying machine according to the present invention.

2 is a front view showing a density sensor used in the developing tank of FIG. 1. FIG.

FIG. 3 is a circuit diagram showing the circuit configuration of the concentration sensor of FIG. 2;

FIG. 4 is a graph showing the output characteristics of the concentration sensor of FIGS. 2 and 3;

FIG. 5 is a graph showing the characteristics of a high boiling point solvent during copy running in the developing tank of FIG. 1;

FIG. 6 is a graph showing ranks of fixability.

FIG. 7 is a sectional view showing a schematic configuration of an embodiment of a wet-type electrophotographic copying machine according to the present invention.

8 is an enlarged sectional view of the electrophotographic section of FIG. 7. FIG.

FIG. 9 is a diagram showing the relationship between the number of copies and toner replenishment start voltage and toner replenishment stop voltage after developer replacement.

FIG. 10 is a block diagram showing essential parts of a second embodiment of a wet-type electrophotographic copying machine according to the present invention.

11 is a graph showing the relationship between the charging potential of the photosensitive drum of FIG. 10 and the amount of toner adhesion.

12 is a graph showing the relationship between the output current of the high-voltage power supply in FIG. 10 and the charging potential of the photosensitive drum.

FIG. 13 is a diagram showing the relationship between the number of copies and the output current from the high-voltage power supply after replacing the developer.

FIG. 14 is a block diagram showing main parts of a third embodiment of a wet-type electrophotographic copying machine according to the present invention.

FIG. 15 is a graph showing the relationship between the developing bias voltage and the amount of toner attached to the photosensitive drum.

[Explanation of symbols]

5 Photosensitive drum 6 Charger 8, 9 Developing roller 21 Toner bottle 22 Developing bottle 23 Developing tank 24 Developing solution 26 CdS sensor 30, 40, 42 Microcomputer 41, 43
High voltage power supply 44 Lamp regulator 45 Halogen lamp

Claims (3)

[Claims] 1. An image carrier for forming an electrostatic latent image by exposure, a charging means for pre-charging the image carrier before exposure, and a toner concentrated and dispersed with a high boiling point solvent and a low boiling point solvent. Wet electrophotography, comprising: a developing means for developing the electrostatic latent image on the image carrier with a developer having the following: a control means for controlling the concentration of the developer to become thinner as the number of copies increases. Copy machine. 2. An image carrier for forming an electrostatic latent image by exposure, charging means for pre-charging the image carrier before exposure, and a toner concentrated and dispersed with a high boiling point solvent and a low boiling point solvent. A wet type electronic device comprising: a developing means for developing the electrostatic latent image on the image carrier with a developer having the above-mentioned electrostatic latent image; and a control means for controlling the charging potential of the charging means to decrease as the number of copies increases. Photocopy machine. 3. An image carrier for forming an electrostatic latent image by exposure, a charging means for pre-charging the image carrier before exposure, and a toner concentrated and dispersed with a high boiling point solvent and a low boiling point solvent. and a control means for controlling the developing bias voltage of the developing means to increase as the number of copies increases. Electrophotocopy machine.