JPH01185567A - Image forming apparatus with multiple developing means - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to the transfer of toner images formed by different developing devices to a single transfer material, separation from an image carrier, and fixing of toner images. The present invention relates to an image forming apparatus that performs the process multiple times.

[Conventional technology]

Conventionally, image forming apparatuses have been configured to have multiple modes and double-sided modes as shown in FIG. Image formation is performed twice on the material using two developing devices. - After forming an electrostatic latent image by irradiating the image exposure 12 onto the surface of the image carrier 10 uniformly charged by the next charging device 11, the electrostatic latent image is transferred to the toner by the developing device 13 or 14. After the image is developed, a charge of opposite polarity to the toner is applied to the back side of the transfer material 18 brought into close contact with the toner image by a transfer device 15, and the toner image is transferred to the transfer material 18 by electrostatic attraction. Immediately after the transfer process is completed, a separating device 16 applies an AC corona or the like to the back surface of the transfer material 18 to remove electricity from the transfer material 18 and separate the transfer material 18 from the image carrier 10 .

The transfer material 18 that has thus completed the first transfer 9 separation step has the toner image fixed thereon by the fixing device 19, and is then sent in the direction of arrow a and loaded on the paper refeeding device 21. When the number of transfer materials on which the first image has been formed are loaded onto the refeeding device 21 as specified by the operator, those transfer materials 18 are then moved in the direction of arrow C by the refeeding device 21. The second toner image is transferred one by one to the image carrier 10.
The process of separation from This second toner image is formed using another developing device that is not the developing device used for the first image formation.

[Problem to be solved by the invention] The transfer material 18 is 1
During the second fixing process, a wavy shape called "curl" as shown in Fig. 2 is formed.Static charge removal separation uses the elastic force of the transfer material to separate the transfer material from the image carrier. In this method, the separation performance varies greatly depending on whether or not the transfer material is curled.

For example, as shown in FIG.
If the transfer material 18 is upwardly curled along the curved surface of the image carrier 10, the elastic force that tends to cause the transfer material 18 to separate from the surface of the image carrier 10 will not be large enough. Therefore, in the separation step, problems such as poor separation and retransfer tend to occur, both in terms of transportability of the transfer material 18 and in terms of image quality.

Furthermore, in the static elimination separation method, the separation performance increases (changes) depending on the state of developer adhesion called "fog" that slightly adheres to the white background area of the image carrier 10 surface during the development process. When there is less fog developer attached to the white background area of the image on the image carrier surface, poor separation and retransfer tend to occur.Furthermore, in the static elimination separation method, the amount of charge on the toner forming the toner image is large. The frequency of occurrence of retransfer increases (varies) depending on the difference in the toner image formed on the surface of the image carrier.Specifically, retransfer occurs when the amount of charge per unit weight of the toner forming the toner image formed on the surface of the image carrier is small. It's easy to do.

Among the toner images formed by two types of developing devices, one of the toner images has less fog developer attached to the white area of the image on the surface of the image carrier, and the toner forming the toner image If the charge I per unit weight of the toner image is small, it is extremely difficult to separate the transfer material on which the toner image has been electrostatically transferred from the image carrier using a static elimination separation type separation device, and separation failure or retransfer may occur. Cheap. Therefore, compared to the transfer material with the above-mentioned upper curl, there is less fog in the white background area of the image (and the toner image formed with toner with a small charge of 1 per unit weight is electrostatically transferred to the transfer material). An image forming apparatus having a conventional configuration in which the transfer material is separated by static electricity removal has the disadvantage that poor separation and retransfer occur frequently, resulting in significant deterioration of the conveyance of the transfer material and the image quality.

Here, the white background area of the image includes both the white background area on the document and the white background area formed by eraser exposure or the like.

[Summary of the invention]

The present invention focuses on adhesion parameters for the developer used by the developing device to adhere to the latent image area (image area) or background area (non-image area) of the image carrier,
Its outline is represented by the following explanation. Here, the term adhesion parameter means that when the developer is mainly toner,
Due to the characteristics of the toner particles themselves, the amount of charge and magnetization required to adhere to the image carrier is included, and when the developer consists mainly of toner and carrier, only the carrier in addition to the toner is present on the surface of the image carrier. This includes the amount of adhesion and the amount of "fogging" described later.
Also included.

The present invention includes an image carrier, a means for forming a latent image on the image carrier, a first developing means and a second developing means for converting the latent image formed on the image carrier into a toner image, and a means for forming a latent image on the image carrier. The toner image processing means includes a step of transferring the toner image formed on the image carrier to a transfer material, a step of separating the transfer material from the image carrier, and a step of fixing the toner image to the transfer material. and the second above
The developing means includes a first developing means formed by the first developing means.
A second developer used by the second developing means to form a second toner image on the image carrier to be transferred again to the transfer material on which the toner image has been fixed by the processing means. is an image forming apparatus characterized in that a plurality of adhesion parameters for adhering to the surface of the image carrier are relatively large compared to the first developer used by the first developing means. Therefore, stable image formation can be achieved regardless of the condition of the transfer material.

Particularly preferable image forming apparatuses of the present invention include those which have a low amount of fogging developer attached to the white image area on the surface of the image carrier (and have a low amount of fogging developer per unit weight of toner forming the toner image). The object of the present invention is to prevent poor separation and retransfer by a simple configuration in which images are formed in order from the developing device with the smallest charge I, and to always obtain stable conveyance of the transfer material and high-quality images.

The term "fogging developer" in the white area of the image carrier surface on the surface of the image carrier is small means as described above.

(2) The number of fogging developer particles attached per unit area of the image blank area on the surface of the image carrier is small.

2) The number of fog developer particles having a particle size of 10 μm or more is small among the fog developer particles attached per unit area of the white background area of the image carrier surface.

3) The number of fog developer particles having a particle size of 15 μm or more is small among the fog developer particles attached per unit area of the white background area of the image carrier surface.

4) The number of fog developer particles having a particle size of 20 μm or more is small among the fog developer particles adhering per unit area of the image blank area on the surface of the image carrier.

5) The ratio of the area occupied by the fogging developer particles adhering to the image white area on the surface of the image carrier to the area of the entire image area is small.

〔Example〕

FIG. 1 is a schematic diagram of an image forming apparatus embodying the present invention. The developing device 13 is a two-component magnetic brush developing type developing device in which the developer contains a carrier and the like, and the developing device 14 is a one-component non-contact developing type developing device in which the developer does not contain a carrier. These developing devices have different developing methods, so when forming a toner image, fog that slightly adheres to the image white area on the surface of the image bearing member 10 and the adhesion state of the developer and the toner forming the toner image. The amount of charge is different. In this embodiment, the toner image formed by the developing device 14 has a smaller number of fogging developer particles attached per unit area of the white image area on the surface of the image carrier 10 than the toner image formed by the developing device 13. few. When the toner image formed on the surface of the image carrier 10 by the developing device 13 was observed under a microscope, the number of fog developer particles per unit area on the white background of the image was 390.
pieces/mrr? Met. On the other hand, the developing device 14
A similar observation was made for the same, and the number of fog developer particles per unit area was 165 particles/m rd. This result clearly shows that the toner image formed by the developing device 14 has fewer fogging developer particles on the white background portion of the image than the toner image formed by the developing device 13.

Furthermore, the toner image formed by the developing device 14 has a smaller amount of charge per unit weight of the toner forming the toner image than the toner image formed by the developing device 13.

In the image forming apparatus implementing the present invention, a toner image formed by the developing device 13 on one sheet of transfer material 18 and a toner image formed by the developing device 14
When an image is formed by transferring two types of toner images, including the toner image formed in step 1, image formation is performed in the following order. After the first electrostatic latent image is formed, the number of fogging developer particles adhering per unit area of the white background area of the image is small, and the amount of charge per unit weight of the toner forming the toner image is small. A toner image is formed by the developing device 14, the toner image is transferred onto the transfer material 18, and after the steps of separating the transfer material 18 and fixing the toner image are performed, the transfer material 18 is re-fed. Load it onto the device 21. The transfer performed here is electrostatic transfer, and the separation is performed by a static elimination separation method. Furthermore, it goes without saying that this first electrostatic latent image is an electrostatic latent image of an image that the operator has specified to be formed with the developer of the developing device 14. After the first image has been formed, the transfer material 18 is transferred to the paper refeeding device 2 for a predetermined number of sheets designated by the operator.
1, the transfer materials 18 are fed out one by one in the direction of arrow C by a refeeding device 21 to perform a second process of transferring the toner image and separating it from the image carrier 10. be exposed. The second toner image always has a larger number of fog developer particles attached per unit area of the white background area of the image carrier 10 surface than the first toner image (and a larger number of toner particles forming the toner image). The developing device 13 has a large amount of charge per unit weight.

In the first separation process, the transfer material 18 has not undergone the fixing process even once, so it does not have large curls that work against separation, so the toner image to be transferred is
The transfer material 18 can be easily separated after transfer, even if the toner image is formed by a developing device 14 with a small amount of fogging developer particles per unit area (and a small amount of charge per unit weight of the toner forming the toner image). It is possible to do with poor separation,
No retransfer occurs. In the second separation process, the transfer material 18 has large curls caused in the first fixing process, but the toner image to be transferred has a large number of foggy developer particles per unit area, and the toner image is not formed. The developing device 13 has a large amount of charge per unit weight of toner.
Since the toner image is formed using a toner image, the transfer material 18 can be easily separated, and separation failure and retransfer will not occur. The image forming apparatus with the configuration of this embodiment and the conventional configuration, that is, the order of forming toner images of two developing devices is such that the developing device with the most foggy developer particles and the largest amount of charge per unit weight of toner starts first. Table 1 shows the results of measuring and comparing the frequency of occurrence of separation defects and retransfer between the image forming apparatus and the image forming apparatus configured to form a toner image.

It is clear from this experimental result that the present invention is highly effective.

r In the present invention, the amount of charge of the toner per unit weight on the image carrier was determined using a suction type Faraday gauge method. Since the measurement in the present invention is a relative comparison of developing means, it is sufficient to use the same developing means. For details on the principle of the suction type Faraday gauge method, see, for example, the Electrophotography Society Journal Vol.
1.11. It has been introduced as No. 1. J In the above-mentioned embodiment, the configuration was explained using as an example a configuration in which images are formed in order from the developing device in which the number density of fog image agent particles adhering to the white background area of the image is small and the amount of charge per unit weight of toner is small. The gist of the invention is to form an image using a developing device in which the adhesion state of the fogging developer that adheres to the white background portion of the image is disadvantageous to a separation device using a static elimination separation method, and in which the amount of charge per unit weight of toner is small. The same effect can be obtained by determining whether there is more or less fog developer depending on the particle size distribution of the fog developer particles as described below.

If there is no large difference in the number of fog developer particles per unit area adhering to the white background area of the toner image formed by the two developing devices, the fog developer particles with larger particle size will be larger than all the fog developer particles. A similar effect can be obtained by forming an image in order from the developing device that occupies a smaller number of developing devices. The ratio of fog developer particles with a large particle size to the total number of fog developer particles is defined as, for example, the number of fog developer particles with a particle size of 10 μm or more among the fog developer particles that adhere to the white background area of the image. Fog is the value divided by the total number of developer particles.

If no large difference was observed in the proportion of fog developer particles with a particle size of 10 μm or more,
For example, the same effect can be obtained by determining whether there is more or less fogging developer between two developing devices based on the ratio of fogging developer particles of 15 μm or 20 μm or more and determining the order of the developing devices that form an image. be able to. Table 2 is 2
The number of fog developer particles per unit area adhering to the white background area of the toner image formed by the two developing devices is about the same, and the particle size of the developing device 14 is 10% larger than that of the developing device 13.
According to the present invention, when the ratio of the number of fog developer particles of μm or more is small and the toner image formed by the developing device 14 has a smaller charge ↑ per unit weight of the toner forming the toner image, An image forming apparatus with a configuration in which images are formed in order from the developing device 14 with less fog developer and a small charge 1 per unit type of toner, and an image forming apparatus with a conventional configuration in which images are formed in the reverse order. These are the results of measuring and comparing the frequency of occurrence of poor separation and retransfer between the two devices.

Among the fog developer particles adhering to the white background area of the toner images formed by the developing devices 13 and 14 used here, the ratio of the number of fog developer particles with a particle size of 10 μm or more is 46%, respectively. and 31%.

It is clear from this experimental result that the present invention is highly effective.

Furthermore, if the particle size distribution in terms of number of fog developer particles adhering to the white background area of the toner image formed by either of the two developing devices is concentrated in the particle size of 10 μm or less, the following A greater effect can be obtained by determining whether there is a lot of fog developer or not and determining the order of developing devices that form an image using a method such as the following. The particle size distribution of the fog developer particles adhering to the white background area of the toner image in the two developing devices is accumulated from the larger particle size, and the value is calculated based on the total number of fog developer particles. A larger effect can be obtained by forming images in order from the developing device having a smaller particle size reaching 50% (and a smaller amount of charge per unit weight of the toner forming the toner image).

If the cumulative value is 50% and no difference is recognized between the fog conditions of the two developing devices, the numerical particle size distribution is accumulated from the one with the largest particle size and that value becomes the total number of foggy developer particles. The same effect can be obtained by comparing the fog adhesion state (size of fog) of two developing devices with a particle size of 30%, 20%, or 10%.

Table 3 shows the number and size distribution of foggy developer particles adhering to the white background area of the image, cumulatively starting from the largest particle size, and the particle size at which the value becomes 10% of the total number of foggy developer particles is the developing device. 13 is 15 μm, and developing device 14 is 11 μm.
In addition, when the amount of charge per unit weight of the toner forming the toner image formed by the developing device 14 is smaller than that of the developing device 13, according to the present invention, fog is reduced (
In addition, an image forming apparatus that forms an image first with the developing device 14, which has a small amount of charge per unit weight of toner, and an image forming apparatus that has a conventional configuration that forms an image in the reverse order, are susceptible to poor separation and retransfer. This is the result of measuring and comparing the frequency of occurrence.

Table 3 It is clear from the experimental results that the present invention is highly effective.

In addition, the same effect can be obtained by forming images in order from the developing device in which the area occupied by the fogging developer particles has a small proportion to the area of the entire white background portion of the image, and the amount of charge per unit weight of toner is small. .

In the embodiments of the present invention, a combination of a two-component magnetic brush developing type developing device and a one-component non-contact developing type developing device has been described, but regardless of the developing method or type of developer, the developing device can be Fog adhering to the image white area on the surface of the image carrier during the process The same effect can be achieved if the order of image formation is determined depending on the amount of developer and the amount of charge per unit weight of the toner image formed by the developing device. is obtained. Further, in this embodiment, the effect was explained for an image forming apparatus having only two developing devices, but the number of developing devices is not limited to two, and the same effect can be obtained for an image forming apparatus having two or more developing devices. Obtainable.

〔Effect of the invention〕

The present invention solves the problems of the conventional technology, and makes it possible to always obtain stable transfer material conveyance and high-quality images without causing separation defects or retransfer using a new but relatively simple configuration. did it.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an image forming apparatus embodying the present invention. FIG. 2 is an explanatory diagram of curling of the transfer material that occurs during the fixing process. FIG. 3 is an explanatory diagram of the relationship between the curved surface of the image carrier surface and the curved surface of the curl of the transfer material when the top-curled transfer material is passed through. 1O: Image carrier 11 Primary charging device 12: Image exposure 13: Developing device A14: Developing device B
15: Transfer device 16: Separation device 17
:Cleaning device 18 Transfer material 19:
Fixing device 21: Paper refeeding device

Claims (2)

[Claims] (1) An image carrier, means for forming a latent image on the image carrier, first developing means and second developing means for converting the latent image formed on the image carrier into a toner image, and A toner image processing means for performing the steps of transferring the toner image formed on the image carrier to a transfer material, separating the transfer material from the image carrier, and fixing the toner image to the transfer material; The second developing means transfers the second toner image to be transferred again to the transfer material onto which the first toner image formed by the first developing means has been fixed by the processing means onto the image carrier. The second developer used by the second developing means adheres to the surface of the image carrier relatively compared to the first developer used by the first developing means. An image forming apparatus characterized in that a plurality of adhesion parameters are large. (2) The above-mentioned adhesion parameter is the amount of charge of toner particles contained in the first and second developers and the amount of developer particles that adhere to the background portion of the latent image on the image bearing member. The image forming apparatus according to item 1.