JPH08240952A - Image forming method and device - Google Patents

Abstract

PURPOSE: To prevent the irregularity and the deviation of an image caused by pressing a transfer means to an image carrier by specifying the repulsive elastic modulus of the transfer means. CONSTITUTION: This device is constituted of the image carrier (photoreceptor drum) capable of forming an electrostatic latent image, a developing means performing the superposed-development of two or more colors with electrostatically charged toner on the image carrier, the transfer means(transfer roller) for electrostatically collectively transferring the toner image obtained by the development on a transfer material altogether, and a means for pressing the transfer roller to the image carrier. Then, the repulsive elastic modulus of the transfer roller is set to <=70%. In the figure, a chart showing the rotational angle position(0 to 360 deg.) of the photoreceptor drum and the positional deviation (a) and (b) of the photoreceptor drum in a state where the transfer roller is in press-contact with/separated from the photoreceptor drum is expressed. Obviously, it is satisfactory to set the repulsive elastic modulus of the transfer roller to <=70%. Furthermore, it is much more satisfactory to use the transfer roller whose repulsive elastic modulus is 20 to 60% even in the case elasticity is given by adding plasticizer and conductivity is given by adding conductor as the transfer roller to be used.

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 shift due to vibration when the transfer means is pressed against the image carrier and separated.

[0002]

2. Description of the Related Art FIG. 3 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 also 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, 9 is pre-charging exposure means (PCL), 10 Is an upstream register for transporting the transfer material 6. Controller, likewise downstream registration roller 11, 12 denotes a transfer power source.

[0003]

However, in such a conventional image forming apparatus, when a transfer roller is used as the transfer means and the transfer roller is pressed against the image carrier at the time of transfer, a transfer image defect is particularly caused. It is easy to occur.

As a result of various experiments and studies, the inventor of the present invention has found that when the repulsive elasticity of the transfer roller is large, the vibration and the peripheral speed unevenness given to the photosensitive drum under the same conditions are large, which causes an image being written in the optical system. Or disturb the image being developed,
It has been found that the image defects are generated by shifting or the like, but the image defects do not occur if the impact resilience of the transfer roller is set to an appropriate value.

The present invention has been made based on these findings.

[0006]

According to the image forming method of the present invention, a transfer material is passed between an image carrier having toner images of two or more colors superposed on each other and the transfer means. In the image forming method of electrostatically collectively transferring the toner images onto the transfer material by pressing the image carrier, the repulsion elastic modulus of the transfer means is set to 70% 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 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 against the image carrier, the repulsion elastic modulus of the transfer unit is 70% 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 area 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 curvature radius of 40 mm or more at least at the transfer or separation portion.

[0013]

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

In the present invention, the repulsion elastic modulus of the transfer means 5, for example, the transfer roller, is 70% or less, preferably 20 to.
60%.

Here, the impact resilience R (%) of the transfer roller
Means that a test piece is placed on a horizontal table of a tester, a steel ball is allowed to freely fall from a distance D ₀ of an upper surface of the test piece of 460 mm, and this test is performed for each of the three test pieces, or 1
Each test piece was conducted three times or more on three points, and the maximum repulsion distance D ₁ of each result was recorded.
It is obtained as D ₁ / D ₀ .

Table 1 shows the transfer rollers A to F with a peripheral speed of 100.
The amount of positional deviation (μm) of the photosensitive drum when it is pressed against the photosensitive drum of mm / sec with a force of 400 g / cm ² and then separated is a and b, respectively, and the peripheral speed of the photosensitive drum is the same. The unevenness (mm / sec) is respectively c and d
It is shown as.

[0017]

[Table 1]

The transfer rollers A to F are all of conductive foam sponge type, and the transfer roller A is
Bridgestone Corporation ion conductive type, electric resistance 3 x
It has a hardness of 10 ⁷ Ω, a hardness of 35 (Asker C hardness meter), and a repulsion elastic modulus of 62 (%).

The transfer roller B is an ion conductive type manufactured by Sumitomo Rubber Industries, Ltd., having an electric resistance of 7 × 10 ⁷ Ω, a hardness of 30 (Asker C hardness meter), and a repulsion elastic modulus of 53 (%).

The transfer roller C is a urethane urethane rubicell type manufactured by Nitto Kogyo Co., Ltd. (Toyo Polymer Co., Ltd.), an electric resistance of 1 × 10 ⁸ Ω, a hardness of 22 (Asker C hardness meter),
The impact resilience is 46 (%).

The transfer roller D has a repulsion elastic modulus of 76 (%).

The transfer roller E has a repulsion elastic modulus of 83 (%).

The transfer roller F has a repulsion elastic modulus of 87 (%).

FIG. 1 shows the rotational angle position (0
Is about 360 °) and the positional deviations a and b of the photoconductor drum in the pressure contact state and the separated state of the transfer roller.

FIG. 2 is a diagram showing the peripheral speed irregularities c and d of the photosensitive drum.

As is clear from the above experimental values, the repulsion elastic modulus of the transfer roller is preferably 70% or less, and the transfer roller used is made to have elasticity by adding a plastic material and is made conductive by adding a conductive material. It has elasticity, but the impact resilience is 20
Those of -60% are particularly preferable.

If the repulsion elastic modulus is 20% or less, the pressing force of the transfer roller against the photosensitive drum becomes weak, which is not preferable.

If the impact resilience exceeds 70%, the vibration applied to the photosensitive drum increases, the peripheral speed unevenness increases, and the image being written by the optical system or the image being developed is disturbed or displaced. As a result, image defects are likely to occur.

The electric resistance value of the transfer roller is 16 mm in diameter, 310 mm in length, and 4 mm in wall thickness for transfer rollers manufactured by different manufacturers (materials or components are different from each other). 170 g
When pressed with a force of / cm ² , the temperature is 20 ° C and the humidity is 50%.
Is an electric resistance value between the rotating shaft of the transfer roller and the aluminum base tube, measured under the environment.

The image bearing member may be an intermediate transfer member.

FIG. 4 shows such an intermediate transfer member 1a,
When this intermediate transfer body 1a is used, the electrostatic latent image formed on the rotated image carrier 1 is developed with the charged toner of the developing device 3 to form a toner image, and the toner image is formed. After transfer from the image carrier 1 to the intermediate transfer body 1a, and further electrostatic transfer to the transfer material 6 fed from the paper feeding section and energized in the transfer section where the intermediate transfer body 1a and the transfer roller 5 are in pressure contact with each other. Then, the transfer material 6 is carried out.

[0032]

As described above, according to the image forming method and apparatus of the present invention, there is a great advantage that an image defect caused by pressing the transfer means against the image carrier can be prevented.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an image forming method and apparatus according to the present invention.

FIG. 2 is an explanatory diagram of an image forming method and apparatus according to the present invention.

FIG. 3 is an explanatory diagram of a conventional image forming apparatus.

FIG. 4 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 (7)

[Claims] 1. 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 transfer means is pressed against the image carrier at the time of transfer so that the transfer material is applied to the transfer material. An image forming method for electrostatically transferring a toner image all at once, wherein the repulsion elastic modulus of the transfer means is 70% or less. 2. An image carrier 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 carrier, and a toner image obtained by the development as a transfer material. An image forming apparatus comprising a transfer means for electrostatically transferring all at once and a means for pressing the transfer means against the image carrier, wherein the repulsion elastic modulus of the transfer means is 70% or less. Forming equipment. 3. The image forming apparatus according to claim 2, wherein the image carrier is a photosensitive drum or a photosensitive belt. 4. 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 2 or 3. 5. The image forming apparatus according to claim 2, wherein the developing means is a non-contact developing means. 6. The image forming apparatus according to claim 2, 3, 4, or 5, wherein the developing means is a reversal developing means. 7. The image forming apparatus according to claim 2, wherein the image carrier has a curvature radius of 40 mm or more at least at a transfer or separation portion.