JP2003098845A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent transfer residue from generated to avoid degradation of image quality by preventing the interlayer separation of a multilayer toner, when transferring from an intermediate transcriber onto a form. SOLUTION: An intermediate transcriber (5) uses a toner, of which the surface of a resin base particle is coated with an outer additive. The sticking force between resin base particles is higher than that between the resin base particle and the intermediate transcriber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using a toner having resin mother particle surfaces coated with an external additive.

[0002]

2. Description of the Related Art In color electrophotography, an intermediate transfer member is used to prevent abrasion of a photoconductor and facilitate superposition of color images. Further, resolution is improved by using a toner having a small particle diameter of 20 μm or less, or 10 μm or less. However, the toner having a small particle size has poor transferability as compared with the toner having a large particle size, and if the transfer electric field is strengthened to improve the transfer property, dielectric breakdown occurs and an image defect occurs. This transfer property largely depends on the adhesive force (van der Worth force, mirror image force) between the toner and the photoconductor and between the toner and the intermediate transfer body.

Therefore, in order to improve transferability, the adhesive force between the intermediate transfer member and the toner is made larger than the adhesive force between the photosensitive member and the toner, and further, the toner and the transfer sheet are separated from each other than the adhesive force between the intermediate transfer member and the toner. It has been proposed to increase the adhesive force to paper (Japanese Patent Publication No. 5-50337).

[0004]

By the way, the toner is coated with an external additive in order to improve the charging property, but there are several% of free mother particles in which the coating of the external additive is not sufficient.
Further, in the one-component developing method, the external additive is peeled off from the toner surface due to deterioration in use durability, or embedded in the resin mother particles to reduce the amount of the external additive on the surface. The chargeability is deteriorated by such free mother particles and the toner deteriorated in durability, and when charging failure occurs, the transferability from the photoconductor to the intermediate transfer body and from the intermediate transfer body to the paper is deteriorated by the electric force, and the transfer residue remains. Will occur. In particular, if there are normally-charged toner and poorly-charged toner among the multi-layered toners on the intermediate transfer body, interlayer separation occurs between the normally-charged toner and the poorly-charged toner when transferring to the paper by the transfer electric field. The transfer residue occurs on the intermediate transfer member, and the image on the paper is partially lacking in toner, resulting in deterioration of image quality.

[0005]

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned problems, and prevents the interlayer separation of the multilayer toner from occurring during the transfer from the intermediate transfer body to the paper, and prevents the transfer residual. The purpose is to prevent the image quality from deteriorating. Therefore, in the present invention, in an image forming apparatus having an intermediate transfer body using a toner in which the surface of the resin base particles is coated with an external additive, the adhesive force between the resin base particles is different from that of the intermediate transfer body. It is characterized by being larger than the force of attachment. Further, the present invention is characterized in that the image forming apparatus has an interdem structure having a plurality of image forming units each having an image carrier.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration example of an image forming apparatus to which the present invention is applied. A charger 2, an exposure unit 3, and a rotary developing device 4 are arranged around the photoconductor 1, and the toner image developed by the rotary developing device 4 faces the photoconductor 1 with the intermediate transfer member 5 interposed therebetween. It is transferred to the intermediate transfer body 5 by the transfer electric field by the transfer charger 6 arranged,
The residual potential after the transfer is removed by the charge removing unit 7, an electrostatic latent image is formed again, and toner development is performed. The rotary developing device 4 includes a yellow developing device 4Y and a magenta developing device 4.
M, a cyan developing unit 4C, and a black developing unit 4K. The developing units for each color are rotary-typed intermittently brought to the developing position for development, and the toner image is color-superposed on the intermediate transfer member 5. It The color image on the intermediate transfer member is a secondary transfer roller 9 facing the backup roller 8 with the intermediate transfer member interposed therebetween.
Is transferred to the transfer material 10 by the transfer electric field, and the residual toner on the intermediate transfer material is cleaned by the cleaner 11.

FIG. 2 is a diagram schematically showing the toner used in the present invention. Toner 40 is 1 for high resolution
The toner is a small particle diameter of 0 μm or less, and the surface of the resin mother particle 40a is coated with an external additive 40b for improving the charging property and weakening the adhesive force.

FIG. 3 is a diagram for explaining an example of a one-component non-magnetic developing type developing device. The toner 40 shown in FIG. 2 is agitated by an agitating rod 41, supplied to a developing roller 44 by a supply roller 42, rubbed against the surface thereof and frictionally charged, and further regulated to a constant thickness by a regulation blade 43. Are triboelectrically charged and are conveyed to the nip portion with the photoconductor. The toner that has not been used for the development returns to the inside of the developing device, and the stirring and the triboelectric charging by the supply roller and the regulating blade are repeated again. In the development, selective development is performed in which new toner having good charging performance and uniform charge distribution is preferentially consumed. Comparing the amount of toner consumed up to the life of the developing device and the number of printed sheets, about 95% of each development is repeatedly consumed and returned to the inside of the developing device. As a result of such usage durability, the external additive on the toner surface is embedded or peeled in the mother particles, and the amount of the external additive on the toner surface is reduced. In addition, even in a new toner, there is a few percent of free mother particles which are not sufficiently covered with the external additive. In a toner that is sufficiently covered with an external additive, the transfer efficiency is good because the charging performance is good and the adhesive force is weak, but the toner whose amount of the external additive on the surface decreases with the endurance of use and the adhesive force of the free mother particles have a low adhesive force. And the charging performance also decreases.

When the toner whose chargeability is deteriorated in this way is developed, the amount of charge is small, so the secondary transfer roller 9
The transferability when a transfer electric field according to (FIG. 1) is applied is not sufficient. Toners of different colors are usually attached to multiple layers on the intermediate transfer body, and if some of the multi-layered toners have poor charging, interlayer separation is performed between the normally charged toner and the poorly charged toner during transfer. Will occur. Therefore, in the present invention, from the intermediate transfer member to the transfer material (paper)
At the time of transfer to, the aim is to realize cleanerlessness of the intermediate transfer member by preventing interlayer separation, and this point will be described with reference to FIGS.

FIG. 4 is a diagram schematically showing the transfer from the intermediate transfer member to the paper. Normally, toner is attached in multiple layers on the intermediate transfer member, and here, for convenience of description, it is assumed that toner is attached in two layers as shown in FIG. Then, the adhesive force (van der Worth force, mirror image force) between the resin mother particles 30 and the intermediate transfer member 5 is F1, the adhesive force between the resin mother particles is F2,
When the adhesive force between the resin mother particles and the paper 10 is F3, F1 <F2 (1) is satisfied. When the formula (1) is satisfied, the toner causes interlayer separation when an adhesive force such that F1 <F3 (2) is satisfied is applied between the resin mother particles and the paper by the transfer electric field. Not transcribed.

FIG. 5 is a diagram schematically showing how the poorly charged toner and the normally charged toner are transferred without mutual separation due to mutual adhesion. Due to deterioration of durability of the toner 31,
Alternatively, the toner 32 is a non-charged toner in which the mother particles are free and the external additive is small, the chargeability is deteriorated, and the toner is not sufficiently charged, and the toner 32 is a normally charged toner, and the toner is between the toner and between the toner and each member. The adhesive force of is the same as in the case of Fig. 4,
If the expressions (1) and (2) are satisfied, the adhesive force F
When the toner is attracted to the sheet 10 in step 3, the mutual adhesion force F2 of the toner particles is larger than the adhesion force F1 of the intermediate transfer member, so that the poorly charged toner 31 is also attracted to the normally charged toner 32 and transferred together. .

FIG. 6 is a diagram schematically showing how a poorly charged toner and a normally charged toner are transferred as a lump by mutual adhesion. The uncharged toner 31 and the normally charged toner 32 are lumps, and the adhesion between the toners and between the toner and each member is the same as in the case of FIG. 4, and the formulas (1) and (2) are used.
If the formula is satisfied, the adhesive force F3 between the resin mother particles and the paper causes the resin mother particles to be more attracted to the paper 10 than the adhesive force F1 between the resin mother particles and the intermediate transfer member when the toner is attracted to the paper 10. Since the mutual adhesion force F2 is large, the poorly charged toner 31 is also attracted to the normally charged toner 32 and transferred as a lump.

As described above, by making the adhesive force between the resin mother particles larger than the adhesive force with the intermediate transfer member, it is possible to prevent interlayer separation caused by poorly charged toner. Of course, the external additive is sufficiently covered,
Toner that has been sufficiently charged is transferred by the transfer electric field, so that interlayer separation does not occur.

As an example of the constitution of the intermediate transfer member for making the adhesive force between the resin mother particles and the intermediate transfer member smaller than the adhesive force between the resin mother particles, urethane is used as the belt material of the intermediate transfer member. Polyester, polycarbonate,
It is also possible to use PET or the like, and the PET may include a fluorine-containing or silicon-containing machine.

Next, the adhesive force of each of the new toner and the toner after the endurance of use is compressed into a tablet by pressing the toner, and the tablet is pressed against the intermediate transfer member or a sheet of the same material as that of the toner. An example in which the friction coefficient when pressed and slid is measured will be described. [Example] Toner X is 1000 to 5000 kgf / cm
Compressed ² (toner influence of the mother particle becomes dominant with respect to adhesion by compressing under high pressure), and those tableted 20gf / cm ² ~400gf / cm ² intermediate transfer member and the surface material is the same in Use a toner that has a friction coefficient smaller than that when the toner tablets are pressed against a sheet and slid on the sheet (fixed) and one of the toner tablets is fixed and the other is slid in the same manner.
When the transfer efficiency was measured, it was 99.6 to 1 in the initial stage.
It was possible to secure 00% and 99.3 to 99.7% even after running.

Further, when PT-1000 (manufactured by Yokogawa Electric Co., Ltd.) was used to measure the initial toner by a particle analyzer method, 5% of free mother particles (number ratio)
The data on the toner surface layer was obtained. In the above example, an image forming apparatus using a rotary developing machine and having one photosensitive member has been described as an example. However, image formation in a tandem configuration including a plurality of image forming units each having a photosensitive member is described. The present invention can be applied to the case of being used in a device.

[0017]

The toner is generally composed of mother particles containing a resin such as polyester, styrene or acrylic as a main component and an external additive for coating the surface of the mother particle. The external additive has an adhesive force to a member that comes into contact with the toner. It also has the function of making it smaller and the function of charging the toner. And the transfer efficiency approaches 100%,
In order to achieve an image forming apparatus having a configuration excluding a cleaner mechanism, free mother particles having large adhesion to a contacting member and low chargeability (charge amount of almost 0) are exposed on the surface of free mother particles or It is also necessary to consider the transfer efficiency of the toner whose durability has deteriorated.

Therefore, in the present invention, by making the adhesive force between the resin mother particles constituting the toner larger than the adhesive force between the intermediate transfer member and the resin mother particles, the toner which is difficult to be transferred by electric force is Since it is transferred by being attracted to the surrounding toner, it is possible to achieve high transfer efficiency and stable transfer characteristics regardless of the usage history (durability) of the device, and it is also possible to realize a cleanerless mechanism for intermediate transfer members. Is.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of an image forming apparatus to which the present invention is applied.

FIG. 2 is a diagram schematically showing a toner used in the present invention.

FIG. 3 is a diagram illustrating an example of a one-component non-magnetic developing type developing device.

FIG. 4 is a diagram schematically showing transfer from an intermediate transfer member to a sheet.

FIG. 5 is a diagram schematically showing how a poorly charged toner and a normally charged toner are transferred without mutual separation due to mutual adhesion.

FIG. 6 is a diagram schematically showing how a poorly charged toner and a normally charged toner are transferred as a lump by mutual adhesion.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photosensitive member, 2 ... Charging device, 3 ... Exposure unit, 4 ... Rotary type developing device, 5 ... Charging device, 7 ... Static elimination light, 8 ... Backup roller, 9 ... Secondary transfer roller, 10 ... Transfer material, 11
... cleaner.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H005 AA08 AA21                 2H030 AB02 AD01 BB24 BB42                 2H200 GA12 GA23 GA46 GA47 GA49                       GB02 HA02 HA12 HB12 HB22                       JA02 JB06 JB16 JC03 JC07                       JC12

Claims (2)

[Claims] 1. In an image forming apparatus having an intermediate transfer member using a toner in which the surface of a resin mother particle is coated with an external additive, the adhesive force between the resin mother particles is the adhesive force between the resin mother particle and the intermediate transfer member. An image forming apparatus characterized by being larger than. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus has a plurality of image forming units each including an image carrier.