JPH03172880A - Image forming method - Google Patents

Abstract

PURPOSE:To perform a stable image forming action by setting transfer efficiency in a transfer stage at specified rate or more and eliminating a cleaning stage for cleaning an image carrier. CONSTITUTION:An electrostatic latent image is formed on the endless image carrier 1 and is developed. In an image forming method in which the developed image on the image carrier 1 is transferred on a printing medium, it is found out that remaining toner does not cause an afterimage on the printing medium even though the image carrier 1 is not cleaned by separating a cleaning part, taking a transfer device 4 as a transfer roller 4', and setting the transfer efficiency in the transfer stage >=80% by the use of polyester toner and magnetite carrier for electrostatically charging developer to be positive. Therefore, a remaining toner quantity after transfer is set <=20% with respect to an image toner quantity just after development, that is, the transfer rate is set >=80%, so that the cleaning stage is not necessitated and excellent printing is obtained without afterimage on a printing paper.

Description

[Detailed description of the invention] [Table of contents] Overview Industrial field of application Prior art (Figure 7) Means for solving the problems to be solved by the invention (Figure 1) Working examples (Figure 2) 6) Effects of the Invention [Summary] Regarding an image forming method in which an electrostatic latent image is formed on an image carrier, developed, and transferred to a printing medium, the present invention aims to omit the cleaning process and forms an endless image. An image forming method comprising the steps of forming an electrostatic latent image on a carrier, developing the electrostatic latent image on the image carrier, and transferring the developed image on the image carrier to a printing medium, By setting the transfer efficiency in the transfer step to 80% or more, the cleaning step of cleaning the image carrier was omitted.

[Industrial application field]

The present invention relates to an image forming method in which an electrostatic latent image is formed on an image carrier, developed, and transferred to a printing medium.

2. Description of the Related Art In electrophotographic devices, transfer type electrostatic recording devices, and the like, an image forming method is used in which an electrostatic latent image is formed, developed, and transferred.

In such an image forming method, it is desirable that the steps are simple.

[Conventional technology]

FIG. 7 is an explanatory diagram of the prior art.

For example, in electrophotography, an image carrier (photosensitive drum) 1 is pre-charged with a pre-charger 2a, and a photoimage generating section 2b is exposed to a light image to form an electrostatic latent image on the photosensitive drum l.

Next, developer is supplied to the photosensitive drum 1 by the developing roller 32 of the developing device 3, and the electrostatic latent image on the photosensitive drum 1 is developed.

Further, the developed image (toner image) on the photosensitive drum 1 is transferred by the transfer device 4 onto a print medium (paper) which is taken out from the hopper by a pickup roller 60 and fed by conveyance rollers 61 and 62.

For reuse, the photosensitive drum 1 is subjected to AC static neutralization or optical static neutralization, and a cleaning section 5 cleans toner remaining on the surface.

In the developing device 3, the stirring roller 31 stirs the developer inside and supplies it to the developing roller 32, and the layer thickness regulating blade 33
The thickness of the developer layer on the developing roller 32 is regulated to a constant value, and the remaining developer is returned to the stirring roller 31 by a flow plate.
The consumed toner is replenished from the toner replenishing section 30.

As described above, in the prior art, the cleaning process was an essential process for reusing the photosensitive drum I.

[Problem to be solved by the invention]

However, the cleaning process had the following problems.

■ Cleaning has to accomplish the difficult task of removing residual toner without damaging the photosensitive drum 1, making it extremely difficult to operate satisfactorily, resulting in poor cleaning, drum filming, etc. problems often occurred.

(2) Furthermore, if the toner collected by cleaning is sent to the developing device again for development, there is a fear that the print quality will deteriorate, so the collected toner has been discarded.

Therefore, there is a problem in that the amount of toner consumed increases, leading to an increase in running costs.

Therefore, an object of the present invention is to provide an image forming method that can omit the cleaning step.

[Means to solve the problem]

FIG. 1 is a diagram showing the principle of the present invention.

As shown in FIG. 1, the present invention includes a step of forming an electrostatic latent image on an endless image carrier 1, a step of developing the electrostatic latent image on the image carrier 1, and a step of developing the electrostatic latent image on the image carrier 1. An image forming method comprising a step of transferring the developed image of image carrier 1 onto a printing medium, in which the transfer efficiency in the transfer step is set to 80% or more, thereby omitting the cleaning step of cleaning the image carrier 1. .

[Effect]

In the present invention, the transfer efficiency is generally 60-70%,
It has been discovered that by setting the transfer efficiency to 80% or more, residual toner does not appear as an afterimage on the print medium even without cleaning.

That is, if the residual toner after transfer is less than 20%, it will not appear as an afterimage, so the transfer efficiency is set to 80% or more and the cleaning step is omitted.

〔Example〕

FIG. 2 is an explanatory diagram of the present invention.

The present invention conducted the following experiments.

■ In the electrophotographic apparatus shown in Fig. 7, the cleaning section 5
When the printer was removed from the device, cleaning was not performed, and printing was performed using a developer containing a positively charged polyester toner and a magnetite carrier.
An afterimage appeared on the printing paper.

At this time, the mass M of the toner image was calculated by completely peeling off the toner image on the drum l immediately after development using an adhesive tape whose mass had been measured in advance and measuring the mass.

Next, the toner residual image on the drum 1 after the transfer was peeled off in the same manner, the quality of the toner residual image iN was calculated, and the ratio (residual toner ratio) N7M was determined.

As a result, the residual toner rate was approximately 30%, and therefore the transfer efficiency was 70%.

(2) Next, in the electrophotographic apparatus shown in FIG. 7, the cleaning section 5 was reattached to the apparatus, cleaned, and printed. When the printing was performed, a good print without an afterimage was obtained on the printing paper.

At this time, the amount of toner remaining immediately after the cleaning brush of the cleaning section 5 was determined in the same manner as in (2), and it was found to be approximately 15% to 20% of the amount of toner immediately after development.

Since the transfer efficiency of (2) was 70%, it means that about lθ~15% of the toner was cleaned with the cleaning brush.

■ Furthermore, when printing was carried out under the same conditions with the cleaning unit 5 installed in the electrophotographic apparatus shown in Fig. 7 and the distance between the cleaning brush and the photosensitive drum 1 slightly larger, an afterimage was generated on the printing paper. .

The amount of toner remaining immediately after the cleaning brush at this time was about 25% of the amount of toner immediately after development.

■Same as 7, cleaning brush and photosensitive drum 1
By changing the zero interval or changing the transfer current of the transfer device 4,
The amount of remaining toner was varied, and the presence or absence of an afterimage and the OD value of the afterimage were measured.

When we organized these results and plotted the ratio of the amount of remaining toner to the amount of toner immediately after development on the horizontal axis, and the density (OD value) of the afterimage on the printing paper on the vertical axis, we found that Figure 2 (A) characteristics were obtained.

That is, it has been found that no afterimage appears when the proportion of the remaining toner amount is up to 20%, and when it exceeds 20%, an afterimage appears and the density gradually increases.

Assuming that the developer removed from the photosensitive drum 1 by the cleaning brush is also transferred to the printing paper, the horizontal axis represents the transfer efficiency, and the vertical axis represents the afterimage OD value on the printing paper. The result of (A) can be expressed as shown in FIG. 2 (B).

From the above facts, if the amount of toner remaining after transfer is 20% or less of the amount of image toner immediately after development, that is, the transfer efficiency is 80% or more, there will be no afterimage on the printing paper without the need for a cleaning process. It was found that good printing could be obtained.

The following methods can be used to improve the transfer efficiency.

(2) Set the distance between the transfer wire of the transfer corotron 4 and the photosensitive drum 1, wire diameter, transfer current, transfer voltage, transfer voltage application time (transfer charge width), etc.

■ A transfer roller with high transfer efficiency is used for the transfer device 4.

The transfer roller is a conductive or dielectric roller that applies a voltage of opposite polarity to the toner and presses the printing paper against the photosensitive drum 1 to transfer the toner.
Compared to an i-type transfer charger, printing paper is transferred to photosensitive drum 1.
Transfer efficiency improves by the amount of pressure applied.

0 Use a non-magnetic component developer with high transfer efficiency.

FIG. 3 is a characteristic diagram of a non-magnetic component developer.

As shown in FIG. 3, the non-magnetic component developer has a uniform charge amount compared to other non-magnetic two-component developers.
High transfer efficiency can be obtained.

Next, a specific example will be explained.

B. FIG. 4 is a diagram illustrating a first specific example of the present invention.

In the figure, the same parts as those shown in FIG. 7 are indicated by the same symbols, and the cleaning section is removed from the electrophotographic apparatus 7 in FIG. 7, and the transfer device 4 is replaced with a transfer roller 4'. It is.

An electrophotographic device with this configuration uses a positively charged polyester toner and a magnetite carrier as a developer.
After repeated printing, no afterimage occurred.

Further, when the transfer efficiency was measured in the same manner as described above, the transfer efficiency was about 81%.

When the transfer roller 4' was used, the transfer efficiency did not change even at high temperatures, and stable printing without afterimages was possible without cleaning.

5 is a diagram illustrating a second specific example of the present invention.

In the figure, the same parts as shown in Figures 4 and 7 are:
They are indicated by the same symbols, and 7 is a heat roller fixing device.

Further, the cleaning section 5 includes a cleaner blade 50 and a waste toner box 51.

The transfer corotron 4 has a transfer voltage of 5 KV and a transfer current of 15
0 μA was applied. In this electrophotographic apparatus, the cleaner blade 50 of the cleaning section was removed to prevent cleaning, and the toner used was a one-component developer (negatively charged polyester toner) shown in FIG. 3, and printing was performed repeatedly. No afterimage was observed on the printing paper PP.

Further, when the transfer efficiency was measured in the same manner as described above, the transfer efficiency was 81 to 85%.

c. FIG. 6 is a diagram illustrating a third specific example of the present invention.

In the figure, the same parts as those shown in FIG. 5 are indicated by the same symbols.

In this electrophotographic apparatus, a transfer roller 4' was used as the transfer device (transfer corotron) 4 shown in FIG. 5, and a transfer voltage of 5 KV and a transfer current of 10 μA were applied to the transfer roller 4'.

In this electrophotographic apparatus, the cleaner blade 50 of the cleaning section was removed to prevent cleaning, and the toner used was a one-component developer (negatively charged polyester toner) shown in FIG. 3, and printing was performed repeatedly. No afterimage was observed on the printing paper PP.

Further, when the transfer efficiency was measured in the same manner as described above, the transfer efficiency was 81% to 85%.

Furthermore, since the transfer roller 4' is used, it has excellent environmental characteristics.
The transfer efficiency was 80% or more in any environment.

2. Remove the cleaning section 5 from the configuration shown in FIG. 7,
Using a positively charged polyester toner and a magnetite carrier as a developer, applying a transfer voltage of 5 KV and a transfer current of 150 μA to Transfer Roller I/Ron 4, and repeatedly printing, no afterimage was observed on the printing paper PP. Ta.

The transfer efficiency at this time was about 80%.

As described above, when the transfer efficiency is set to 80% or more, good printing without residual images is possible even if the cleaning step is omitted.

Further, the image carrier is not limited to a photosensitive drum, but may be a dielectric material or the like.

Although the present invention has been described above using examples, the present invention can be modified in various ways according to the gist of the present invention, and these are not excluded from the present invention.

〔Effect of the invention〕

As described above, according to the present invention, (1) the cleaning step can be omitted, so there are no problems of poor cleaning or filming caused by cleaning, and a stable image forming operation is possible.

(2) Since the cleaning process can be omitted, there is no toner to be discarded, the toner can be used efficiently, running costs can be lowered, and the effort of disposing of waste toner can be saved.

(2) Since the cleaning step can be omitted, there is no need to provide a cleaning section, and the device can be made smaller and less expensive.

[Brief explanation of the drawing]

Figure 1 is a diagram of the principle of the present invention, Figure 2 is an explanatory diagram of the present invention, Figure '3 is a characteristic diagram of the non-magnetic component developer used in the present invention, and Figure 4 is the first embodiment of the present invention. FIG. 5 is a diagram illustrating a second specific example of the present invention, FIG. 6 is a diagram illustrating a third specific example of the present invention, and FIG. 7 is a diagram illustrating a prior art. In the figure, 1. Photosensitive drum (image bearing member) 2a-Pre-charger, 2b-.-Photoimage generating section, 3-Developing device, 4.--Transfer device, .--Cleaning section.

Claims (1)

[Claims] A step of forming an electrostatic latent image on an endless image carrier (1), a step of developing the electrostatic latent image on the image carrier (1), and a step of developing the electrostatic latent image on the image carrier (1). ), the image forming method comprises a step of transferring a developed image of (1) onto a printing medium, and the transfer efficiency in the transfer step is set to 80% or more, thereby omitting a cleaning step of cleaning the image carrier (1). An image forming method characterized by: