JPH08240959A - Image forming method and device - Google Patents

Abstract

PURPOSE: To prevent image deviation from occurring by specifying surface pressure by the pressing force of a transfer roller to a photoreceptor drum. CONSTITUTION: A transfer material is allowed to pass between an image carrier having the superposed toner image of two or more colors and a transfer means, and the toner image is electrostatically transferred on the transfer material altogether while pressing the transfer means so that the surface pressure by the pressing force exerted on the image carrier is <=1000g/cm<2> . In order to form the image at a higher speed, the transfer roller must come into press-contact with and be separated from the photoreceptor drum in the midst of writing at least at the time of consecutive printing, and it must come into press-contact with the photoreceptor drum in the midst of developing even in the case of one print. In such press-contact and separation, when the surface pressure by the pressing force is 800g/cm<2> , for example, the variation of the circumferential speed of the photoreceptor drum to the rotational angle position of the photoreceptor drum is small and does not influence the image. However, when the surface pressure is 1500g/cm<2> , the variation is larger and if the transfer roller comes into press-contact with or is separated from the photoreceptor drum in the midst of writing by an optical system and in the midst of developing, the deviation in the image is generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method and apparatus,
In particular, the present invention relates to an image forming method and apparatus for preventing image misalignment due to pressing force and hardness of a transfer unit.

[0002]

2. Description of the Related Art FIG. 14 is an explanatory view of a conventionally known image forming apparatus, in which 1 is an image carrier (photosensitive drum or photosensitive belt) capable of carrying an electrostatic latent image on its outer periphery, and 2 is the above-mentioned. A charger 3 arranged to face the outer periphery of the photosensitive drum 1 for charging the outer periphery of the photosensitive drum 1 also develops an electrostatic latent image formed on the photosensitive drum 1 by image exposure 4. And developing devices 5 of different colors to form a toner image, transfer means such as a transfer roller for electrostatically collectively transferring the toner images on the photosensitive drum 1 onto the transfer material 6, 7 Is a separator for separating the transfer material 6 from the photosensitive drum 1, 8 is a cleaning blade for removing the toner remaining on the photosensitive drum 1, and 9 is a cleaning blade.
Is a pre-charging exposure means (PCL), 10 is an upstream registration roller for conveying the transfer material 6, 11 is a downstream registration roller, and 12 is a transfer power source.

[0003]

However, in such a conventional image forming apparatus, when a transfer roller or a transfer belt is used as the transfer means, and a pressing / separating mechanism for the photosensitive drum is provided. If the surface pressure of the pressing force applied to the transfer means is too high or the hardness of the transfer means is too high, a large vibration is applied to the photoconductor drum during pressure bonding, and the vibration causes an image being written or an image being developed. Cause a deviation. Further, also when they are separated from each other, vibration is similarly applied to the photosensitive drum to cause a shift in the image.

On the other hand, if the pressing force is too low, the transfer roller cannot firmly adhere to the photosensitive drum, so that no nip is formed and transfer unevenness, insufficient image density, and image misalignment are likely to occur.

That is, at the moment when the transfer roller is pressed against the photosensitive drum, the photosensitive drum vibrates in the pressing direction. This vibration affects the writing and development of the optical system and causes image sagging, misalignment and the like. Similarly, when the photosensitive drums are separated from each other, the photosensitive drum vibrates in the separating direction and exerts the same influence.

In this development, the higher the pressing force and the higher the hardness of the transfer roller, the greater the vibration, and the image is affected.

As a result of various experiments and researches, the present inventor has found that the surface pressure of the transfer roller against the photosensitive drum is 1000 g.
It has been found that the image shift can be prevented by setting it to be / cm ² or less.

The present invention has been made based on such knowledge.

[0009]

According to the image forming method of the present invention, a transfer material is passed between an image carrier having a toner image of two or more colors superposed on each other and a transfer means, and the transfer means is used to carry the image carrier. In the image forming method in which the toner images are electrostatically collectively transferred onto the transfer material while being pressed against the body, the surface pressure of the pressing force applied to the transfer means is set to 1000 g / cm ² or less.

According to the image forming method of the present invention, the transfer material is passed between the image carrier having the toner images of two or more colors superposed and the transfer means, and the transfer means is pressed against the image carrier. In the image forming method in which the toner images are electrostatically collectively transferred onto the transfer material, the surface pressure of the pressing force applied to the transfer means is set to 25 g / cm ² or more and 1000 g / cm ² or less.

The image forming apparatus of the present invention is obtained by the above-mentioned development, and an image carrier capable of forming an electrostatic latent image, a developing means for carrying out superimposing development of two or more colors on the image carrier with charged toner. In an image forming apparatus including a transfer unit that electrostatically collectively transfers a toner image onto a transfer material and a unit that presses the transfer unit to the image carrier to separate them from each other, a pressing force applied to the transfer unit is applied. Surface pressure is 1000g /
It is not more than cm ² .

The image forming apparatus of the present invention is obtained by the above-mentioned development, and an image carrier capable of forming an electrostatic latent image, a developing means for carrying out superimposing development of two or more colors with charged toner on the image carrier. In an image forming apparatus including a transfer unit that electrostatically collectively transfers a toner image onto a transfer material and a unit that presses the transfer unit to the image carrier to separate them from each other, a pressing force applied to the transfer unit is applied. Surface pressure is 25g / cm
^{It is 2} or more and 1000 g / cm ² or less.

The hardness of the transfer means in the image forming apparatus of the present invention as measured by an Asker C hardness meter is 70 degrees or less.

The image carrier is a photosensitive drum or a photosensitive belt. As the photosensitive drum here, Se, A
Materials such as s ₂ Se ₃ , a-Si and OPC are used.
Especially as OPC used here, JP-A-64-17
It is preferable to use Y-type titanyl phthalocyanine or polycrystalline titanyl phthalocyanine described in JP-A No. 066, JP-A-2-183258, JP-A-2-183265 and JP-A-3-128973.

The developing means is an image carrier for carrying an electrostatic latent image and a two-component developing means for superimposing a DC component and an AC component on a developing region carrying a two-component developer.

The developing means is a non-contact developing means.

The developing means is a reversal developing means.

The image carrier has a radius of curvature of 40 mm or more at least at the transfer or separation portion.

The transfer means is a transfer roller or a transfer belt.

[0020]

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

In the present invention, the surface pressure of the transfer means 5, eg, the transfer roller, against the photosensitive drum 1 is set to 10 mm.
00 g / cm ² , and the hardness of the transfer roller is 70 degrees or less as measured by an Asker C hardness meter.

In FIGS. 1 and 2, as the transfer roller, an ion conductive type manufactured by Bridgestone Corp., a hardness of 30 (Asker C hardness meter), and an electric resistance of 3 × 10 ⁷ Ω are used, and the surface pressure of the pressing force is 800 g / cm ² and 1500 g / c respectively
When the transfer roller is pressed against the photosensitive drum so as to obtain m ² , the rotational angle position of the photosensitive drum (0 to 360
FIG. 4 is a diagram showing fluctuations in the peripheral speed of the photosensitive drum.

Further, FIGS. 3 and 4 also show the positional fluctuations of the photosensitive drum in the pressing and separating directions of the transfer roller with respect to time.

In order to speed up image formation, at least during continuous printing, it is necessary to press and separate during writing, and even one print needs to be pressed during development.

As is clear from FIGS. 1 to 4, upon pressing and separating as described above, the surface pressure of the pressing force is 800 g / cm.
^{At 2,} the amount of change in the peripheral velocity of the photosensitive drum with respect to the rotational angle position of the photosensitive drum is small and does not affect the image, but when the surface pressure of the pressing force is 1500 g / cm ² , the amount of change is large. When the transfer roller is pressed against the photosensitive drum or separated from the photosensitive drum during writing or developing, the image is misaligned.

FIG. 5 shows the surface pressure (g / cm ² ) of the above pressing force.
And the peripheral speed unevenness (%) of the photosensitive drum in the normal case are shown in FIG. 6. Similarly, FIG. 6 shows the surface pressure (g / cm ² ) of the pressing force and the pressure contact and separation of the photosensitive drum in the normal case. The relation of the deviation (%) of the directions is shown.

As is apparent from FIGS. 5 and 6, the occurrence of image shift can be prevented by setting the surface pressure of the pressing force to 1000 g / cm ² or less.

7 and 8 also show the relationship between the hardness of the transfer roller, the peripheral speed unevenness (%) of the photosensitive drum, and the displacement (%) of the photosensitive drum in the pressure contact and separation directions. From FIG. 8, it can be seen that the image deviation does not occur when the hardness of the transfer roller is 70 degrees or less.

9 and 10 respectively show the relationship between the surface pressure (g / cm ² ) of the above pressing force, the image density measured by a Macbeth densitometer and the image slippage (%) generated at the time of transfer. The following types of rollers were used, and the optimum transfer bias value for each roller was set and tested, but all transfer rollers showed similar results.

(1) Ionic conductive type manufactured by Bridgestone Corporation, (2) Electronic conductive type manufactured by Bridgestone Corporation,
(3) Toyo Polymer Co., Ltd. urethane foam Rubycell type, (4) Sumitomo Rubber Industries, Ltd. ion conductive type, (5) Sumitomo Rubber Industries, Ltd. EPDM type,
(6) Sumitomo Rubber Industries, Ltd. epichlorohydrin type, (7) Inoac Corporation END
UR ion conductive type, (8) foamed silicon type manufactured by Tigers Polymer Co., Ltd., (9) foamed urethane type manufactured by Hokushin Kogyo Co., Ltd., (10) foamed silicon type manufactured by Shin-Etsu Polymer Co., Ltd.

In addition to the transfer roller, evaluations were performed using a transfer belt and a corona discharger as shown in FIGS. 11 to 13, a transfer belt and a transfer roller, and a transfer belt and a brush. Gave similar results.

The electric resistance value of the transfer roller is 16 mm in diameter, 310 mm in length, and 4 mm in thickness.
And put this in an aluminum tube with a diameter of 30 mm
When pressed with a force of g / cm ² , the temperature is 20 ° C and the humidity is 50.
% Is the electrical resistance value between the rotary shaft of the transfer roller and the aluminum tube measured under the environment of%.

The image bearing member may be an intermediate transfer member.

FIG. 15 shows such an intermediate transfer member 1a. When the intermediate transfer member 1a is used, the electrostatic latent image formed on the rotated image carrier 1 is transferred to the developing device 3. The toner image is developed by charged toner to form a toner image, the toner image is transferred from the image carrier 1 to the intermediate transfer member 1a, and the transfer unit in which the intermediate transfer member 1a and the transfer roller 5 are in pressure contact with each other is a paper feeding unit. After the electrostatic transfer is performed on the transfer material 6 that is fed from and is energized, the transfer material 6 is unloaded.

[0035]

As described above, according to the image forming method and apparatus of the present invention, it is possible to prevent the occurrence of image deviation by setting the pressing force and the hardness of the transfer means to desired values. There are great benefits.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a peripheral speed of a photosensitive drum in an image forming apparatus of the present invention.

FIG. 2 is an explanatory diagram of a peripheral speed of a photosensitive drum in the image forming apparatus of the present invention.

FIG. 3 is an explanatory diagram of the displacement of the photosensitive drum in the image forming apparatus of the present invention.

FIG. 4 is an explanatory diagram of the displacement of the photosensitive drum in the image forming apparatus of the present invention.

FIG. 5 is an explanatory diagram of the peripheral speed unevenness of the photosensitive drum in the image forming apparatus of the present invention.

FIG. 6 is an explanatory diagram of the displacement of the photosensitive drum in the image forming apparatus of the present invention.

FIG. 7 is an explanatory diagram of peripheral speed unevenness of a photosensitive drum in the image forming apparatus of the present invention.

FIG. 8 is an illustration of misalignment of the photosensitive drum in the image forming apparatus of the present invention.

FIG. 9 is an explanatory diagram of image density of the image forming apparatus of the present invention.

FIG. 10 is an explanatory diagram of image slip of the image forming apparatus of the present invention.

FIG. 11 is an explanatory diagram of a transfer belt in the image forming apparatus of the present invention.

FIG. 12 is an explanatory diagram of a transfer belt in the image forming apparatus of the present invention.

FIG. 13 is an explanatory diagram of a transfer belt in the image forming apparatus of the present invention.

FIG. 14 is an explanatory diagram of a conventional image forming apparatus.

FIG. 15 is an explanatory diagram of an image forming apparatus using an intermediate transfer member.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image carrier 1a Intermediate transfer body 2 Charging device 3 Developing device 4 Image exposure 5 Transfer means 6 Transfer material 7 Separator 8 Cleaning blade 9 Pre-charging exposure means 10 Upstream registration roller 11 Downstream registration roller 12 Transfer power source

Claims (12)

[Claims] 1. A transfer material is passed between an image carrier having a toner image of two or more colors and a transfer means, and the toner image is transferred onto the transfer material while pressing the transfer means against the image carrier. In the image forming method of electrostatically transferring all at once, the surface pressure of the pressing force applied to the transfer means is 1000 g.
/ Cm ² or less, the image forming method. 2. A transfer material is passed between an image carrier having a toner image of two or more colors superposed and a transfer means, and the toner image is transferred onto the transfer material while pressing the transfer means against the image carrier. In the image forming method of electrostatically transferring all at once, the surface pressure of the pressing force applied to the transfer means is 25 g / c.
An image forming method, characterized in that it is not less than m ^{2 and not} more than 1000 g / cm ² . 3. An image carrier capable of forming an electrostatic latent image, developing means for carrying out superposed development of two or more colors on the image carrier with charged toner, and a toner image obtained by the development as a transfer material. In an image forming apparatus comprising a transfer means for electrostatically transferring all at once and a means for pressing the transfer means to the image carrier to separate them from each other, the surface pressure of the pressing force applied to the transfer means is 1000 g / cm. An image forming apparatus characterized by being ² or less. 4. An image bearing member capable of forming an electrostatic latent image, developing means for carrying out overlapping development of two or more colors with charged toner on the image bearing member, and a toner image obtained by the developing as a transfer material. In an image forming apparatus comprising a transfer unit for electrostatically transferring all at once and a unit for pressing the transfer unit onto the image carrier to separate them from each other, the surface pressure of the pressing force applied to the transfer unit is 25 g / cm. ² or more 1000 g / cm ²
An image forming apparatus comprising: 5. An image forming apparatus according to claim 3, wherein the transfer means has a hardness of 70 degrees or less as measured by an Asker C hardness meter. 6. The image forming apparatus according to claim 3, 4 or 5, wherein the image carrier is a photosensitive drum or a photosensitive belt. 7. The developing means is an image carrier for carrying an electrostatic latent image and a two-component developing means for superimposing a DC component and an AC component on a developing area carrying a two-component developer. The image forming apparatus according to claim 3, 4, 5, or 6. 8. The image forming apparatus according to claim 3, wherein the developing means is a non-contact developing means. 9. The image forming apparatus according to claim 3, wherein said developing means is a reversal developing means. 10. The image forming apparatus according to claim 3, wherein the image carrier has a curvature radius of 40 mm or more at least at a transfer or separation portion. . 11. The image forming apparatus according to claim 3, wherein the transfer means is a transfer roller. 12. The image forming apparatus according to claim 3, wherein the transfer means is a transfer belt.