JPH08240951A - Image forming method and device - Google Patents

Abstract

PURPOSE: To prevent a defective image from being formed by the deformation of a transfer means by specifying the compression set of the transfer means in a method for collectively electrostatically transferring a toner image altogether from an image carrier having the superposed toner images of two or more colors. CONSTITUTION: This device is constituted of the image carrier 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, and the transfer means (transfer roller) for electrostatically collectively transferring the toner image obtained by such development on a transfer material altogether. The compression set of the transfer roller is set to <=40%. It is desirable to bring the transfer roller into contact with/separated from the image carrier. In such a case, when the deterioration rate of the transfer roller is lower than 97%, uneven transfer is caused much in a solid image and a halftone image, especially, and an appropriate transfer area is decreased as the deterioration rate is decreased. Then, the defective image is not formed by fixing the compression set of the transfer roller to a proper value. Namely, when the compression set exceeds 40%, the defective image is suddenly increased.

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 in which an appropriate transfer area is widened without causing image defects.

[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 circumference of the photosensitive drum 1 for charging the outer circumference 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 the transfer roller is used as the transfer means, when the transfer permanent distortion is large and the transfer roller is used for a long time, the transfer roller is It will be deformed, resulting in defective images.

As a result of various experiments and studies, the inventor of the present invention has found that when the deterioration rate of the transfer roller is less than 97%, there are many transfer irregularities especially in solid images and halftone images, and the proper transfer area also decreases as the deterioration rate decreases. However, it was found that an image defect does not occur if the compression set of the transfer roller is set to an appropriate value.

The present invention has been made based on these findings.

[0006]

In 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 and a transfer means, and the toner image is transferred onto the transfer material. In the image forming method of electrostatically transferring all at once, the compression set of the transfer means is set to 40% 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, the compression set of the transfer unit is 40% 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 transfer means is brought into close contact with and separated from the image carrier.

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 radius of curvature of 40 mm or more at least at the transfer or separation portion.

[0014]

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

In the present invention, the compression set of the transfer means 5, for example, the transfer roller, is set to 40% or less.

Here, the compression set C of the transfer roller is set.
(%) Means that after the original thickness t ₀ (mm) of the test piece is correctly measured, it is a compression plate made of aluminum and parallel to both sides, and the test piece is compressed to 50% of its thickness, and the temperature is 70 ±. After continuously heating for 22 hours in a constant temperature bath of 1 ° C., the test piece was taken out, the test piece was removed from the compression plate, and allowed to stand at room temperature for 30 minutes.
₁ (mm) was measured and calculated as (t ₀ −t ₁ ) / t ₀ .

Table 1 shows transfer rollers A to F having a diameter of 18 mm.
Was pressed to the photosensitive drum with a force of 500 g / cm ² , and the number of prints and each transfer roller A when a 200,000 print passing test was performed under the worst environment of temperature 30 ° C. and humidity 80%
9 shows the relationship of the compression ratio of F.

Here, the deterioration rate (%) of the transfer roller is
(Weight of the test piece after use) / (original weight of the test piece)
It was obtained from.

[0019]

[Table 1]

The transfer roller A is an ion conductive type manufactured by Bridgestone Corporation, hardness 35 (Asker C hardness meter), electric resistance 3 × 10 ⁷ Ω, compression set 2.0%.
belongs to.

The transfer roller B is an ionic conductive type manufactured by Sumitomo Rubber Industries, Ltd., hardness 30 (Asker C hardness meter), electric resistance 7 × 10 ⁷ Ω, and compression set 28.0%.

The transfer roller C is a urethane urethane rubicell type manufactured by Nitto Kogyo Co., Ltd., hardness 22 (Asker C hardness meter), electric resistance 1 × 10 ⁸ Ω, compression set 31.0.
%belongs to.

The transfer roller D has a compression set of 45.0.
%belongs to.

The transfer roller E has a compression set of 48.0.
%belongs to.

The transfer roller F has a compression set of 53.0.
%belongs to.

As is clear from Table 1 above, FIG.
Appropriate transfer area (μA) in an environment of 0 ° C and 50% humidity
FIG. 3 is a diagram showing the deterioration rate (%) of the transfer roller.

FIG. 2 shows that when the transfer power source 12 is a constant current source,
3 is a diagram showing a relationship between a transfer rate% of a transfer roller and a transfer current (μA) in an environment of a temperature of 20 ° C. and a humidity of 50%,
The proper transfer area x (μA), the insufficient density area, and the area where image repelling occurs are as shown in FIG.

FIG. 2 also applies when the transfer power source 12 is a constant voltage source.

As is clear from FIGS. 1 and 2, when the deterioration rate was less than 97%, transfer unevenness was confirmed especially in solid images and halftone images. In addition, the proper transfer area also decreases as the deterioration rate decreases.

FIG. 4 shows the relationship between the compression set and the number of image defects.

Here, the o mark is after copying 100,000 sheets,
The marks indicate after copying 200,000 sheets, and A to F indicate the types of transfer rollers.

As is apparent from FIG. 4, the compression set is 4
If it exceeds 0%, the number of defective images sharply increases.

Regarding the electric resistance value of the transfer roller, a transfer roller manufactured by each company (different in material or composition of components) has a diameter of 16 mm, a length of 310 mm, and a wall thickness of 4 mm. 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. 5 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 the 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 is carried out.

[0036]

As described above, according to the image forming method and apparatus of the present invention, there is a great advantage that the occurrence of image defects due to the deformation of the transfer means 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 a diagram showing a relationship between compression set and the number of image defects.

FIG. 5 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 (8)

[Claims] 1. An image forming method in which 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 images are electrostatically collectively transferred onto the transfer material. 40% compression set of the transfer means
An image forming method characterized by the following. 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. In an image forming apparatus including a transfer unit that collectively transfers electrostatically, a compression set of the transfer unit is 40
% Or less, the image forming apparatus. 3. The image forming apparatus according to claim 2, wherein the image carrier is a photosensitive drum or a photosensitive belt. 4. The image forming apparatus according to claim 2, wherein the transfer means is in close contact with and away from the image carrier. 5. The developing means is an image carrier that carries an electrostatic latent image, and a two-component developing means that superimposes a DC component and an AC component on a developing region carrying a two-component developer. The image forming apparatus according to claim 2, 3 or 4. 6. The image forming apparatus according to claim 2, 3, 4, or 5, wherein said developing means is a non-contact developing means. 7. The image forming apparatus according to claim 2, 3, 4, 5 or 6, wherein the developing means is a reversal developing means. 8. The image forming apparatus according to claim 2, wherein the image carrier has a radius of curvature of 40 mm or more at least at a transfer or separation portion.