JPH034291A - Image forming device - Google Patents

Abstract

PURPOSE:To improve cleaning capacity by using such a cleaning blade, as a cleaning means for an image carrier, that the peak temperature of the loss factor of a rubber elastic material is equal to or less than a specific temperature. CONSTITUTION:Conditions to restore the creeping of a rubber elastic material relate to the peak temperature of the loss factor tandelta of the dynamic viscoelasticity data of the rubber elastic material; and durability becomes highest when the peak temperature of the tandelta is 0 deg.C or below. Therefore, the cleaning blade 11 made of a rubber elastic material, such as polyurethane, whose peak temperature of tandelta comes to 0 deg.C or below, is used as the cleaning means 10. Thus, the cleaning capacity in low temperature environment is improved in a device where color toner with a volumetric average grain diameter less than or equal to 9mum is used.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an image forming apparatus such as a color electrophotographic copying machine or a color printer, and particularly to a means for cleaning residual toner from the surface of an image carrier thereof.

[Prior Art] A system that repeats the process of cleaning the toner that does not contribute to the transfer but remains on the surface of the image carrier after transferring the transferable toner image formed on the surface of the moving image carrier to a transfer material is described. It has been well known for a long time.

In this type of image forming apparatus, a cleaning blade made of a rubber elastic material is brought into pressure contact with the image carrier in order to remove the residual toner on the image carrier, which is simple and can be miniaturized due to its structure. It is also very advantageous in terms of cost, so it has been put into practical use more widely than before.

The materials for these rubber elastic materials include polyisoprene, butadiene-stalene copolymer, polybutadiene, polychloroprene, isobutylene-isoprene copolymer, butadiene-acrylonitrile copolymer, ethylene-propylene copolymer, chlorosulfonated polyethylene, Among these, polyurethane is particularly preferred, including acrylic acid ester copolymers, polyurethanes, organic polysiloxanes, perfluoropropene/vinylidene fluoride copolymers, and the like. In many cleaning devices using these cleaning blades, the edge portion of the cleaning blade is brought into contact with the surface of the image carrier in the forward direction as shown in FIG. 2 or in the opposite direction as shown in FIG. ing.

[Problems to be Solved by the Invention] However, in recent years, there has been a tendency to reduce the particle size of toner as a means of improving image quality, and the same applies to image forming apparatuses such as color copying machines and printers. (Conventionally, the volume average particle size was reduced from 12 to 13 μm to 9 μm or less.) These color toners have stronger adhesion to the image carrier surface than conventional black and white toners, As the particle size becomes smaller, cleaning becomes increasingly difficult. This adhesion force to the surface of the image carrier is further enhanced in a low-temperature, low-humidity environment with low absolute humidity. In addition, the aforementioned rubber elastic material exhibits a large change in characteristics depending on the environmental temperature, especially in a low-temperature environment (usually 15 ℃ or below), creep recovery (time course of strain when stress is suddenly removed from a place where strain exists) deteriorates, resulting in an extreme decrease in cleaning ability. (Table 1 shows an example of the temperature dependence of the basic physical properties of rubber elastic materials.
According to IS-6301 physical test method for vulcanized rubber.

Therefore, in order to clean color toner having a small particle size (volume average particle size of 9 μm or less), a rubber elastic material that does not deteriorate creep recovery even in a low temperature environment is required.

As a result of studies by the inventors, it has been found that there is a correlation between the creep recovery state and the peak temperature of the loss coefficient tan δ of the dynamic viscoelasticity data of the rubber elastic material.

Means (and operation) for solving problem E] According to the present invention, by using a cleaning blade such that the peak temperature of the loss coefficient tan δ of the rubber elastic material is 0° C. or less as a cleaning means for the image bearing member, This improves the cleaning ability of an image forming apparatus using color toner having a volume average particle size of 9 microns or less in a low temperature, low humidity environment (approximately 15 DEG C. or less).

[Embodiment] Next, the image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

FIG. 1 shows a full color electrophotographic copying machine which is an embodiment of the present invention. An image carrier 1 is supported rotatably in the direction of the arrow, and an electrostatic image is formed on the image carrier 1 by a charger 2 and an exposure means 3. The latent image is generated by four developing devices attached to the rotary developing unit 4, that is, a yellow developing device 4Y, a magenta developing device 4M, a cyan developing device 4C,
The image is developed and visualized in an arbitrary developer in the black developer 4B, ie, in the yellow developer 4Y in FIG. These developments are carried out using a toner made of styrene-acrylate resin or polyester resin and having a volume average particle diameter of 7 to 9μ, and the visible image (toner image) is transferred to the transfer drum 5.
The image is transferred by a transfer device 6 to a transfer material 8 held above and conveyed.

On the other hand, the image carrier 1 is cleaned of residual toner by a cleaning means 10, and is subjected to the next image forming process.

Thereafter, a toner image is formed on the image carrier L in the same manner, and toner images of the second, third, and fourth colors are transferred onto the same transfer material P in a superimposed manner. The multiple-transferred transfer material 8 is separated from the transfer drum 5 by a separation charger 7, passed through a fixing device 9, and discharged to the outside of the machine.

Such a full-color image forming apparatus and method are well known to those skilled in the art, so further detailed description thereof will be omitted.

According to the invention, the cleaning means 10 is a plate cleaning means having a cleaning plate 11. The cleaning blade 11 can be arranged in the head direction with respect to the moving direction of the image carrier 1, but from the point of view of cleaning efficiency, it is arranged in the direction opposite to the moving direction of the image carrier I as shown in the figure. It is preferable to do so.

Polyurethane was used as the cleaning blade, and dynamic viscoelastic data such as the loss coefficient JAN86, which was most correlated with the creep recovery of the rubber elastic body described above, was measured using a Rheobexy Analyzer manufactured by Iwaki Seisakusho.

The measurement method is the forced torsional vibration method, which is calculated using the formula shown below.

A torsional sine wave vibration (input) at a constant angle is applied, the response torque (output) is measured, and the dynamic viscoelasticity is determined by the respective Fourjer transformations.

Angular displacement 200, frequency: fo-ω. /2π displacement θ (1) − θ. exp(iω.t)
Angular velocity Ω(t)-dθ(t)/dt-iω0θoe
Xp (iω.t) Torque T (t) −T,, exp (i (ωo
t+δ)) The complex viscosity η″ (·η′−iη″) and various dynamic characteristics are obtained from the following equations. F means Fourier transformation.

The loss coefficient tan δ·G''/G' A is an equipment constant and is determined by the test fixture as follows.

A simple diagram of the device is shown in FIG.

An example of this is shown in Figure 5, where samples A, B,
C is an elastic blade made of different materials.
The peak temperature of tan δ is A knee 3℃ B = 2℃ C214
It is ℃. These blades can be used in low-temperature, low-quality environments (1
The results of the actual machine durability test at 5°C/10%) are shown in Figure 5, where the tanδ Peak temperature of A and D is 0°C.
Only the following samples passed the durability test of 10,000 sheets or more and became usable for practical use. (In addition to A-c, sample E was also supplemented.

) For A and D, polyether-based PTMG (polytetramethylene glycol) is used as the volume in urethane rubber synthesized through a polyaddition reaction of isocyanate, polyol, and various active hydrogen compounds.

This deterioration of leap recovery at low temperatures can be improved by using lactone polyester or adipate polyester as the polyol, or by increasing the molecular weight of the polyol.

The color toner used in the Mataki Examples had a volume average particle size of 7 to 9.
Although μ is used, it goes without saying that if there are a plurality of developing devices, this can be applied as long as the volume average particle diameter of the toner in at least one developing device is 9 μ or less.

[Effects of the Invention] As explained above, a rubber elastic material can be used as a cleaning means for an image bearing member in an image forming apparatus having a plurality of developing devices, at least one of which contains color toner having a volume average particle size of 9 μm or less. By using a cleaning blade whose loss coefficient tan δ has a peak temperature of 0° C. or less, the cleaning ability in a low-temperature, low-quality environment can be improved.

[Brief explanation of the drawing]

5B is a schematic diagram of an embodiment of an image forming apparatus embodying the present invention. FIGS. 2 and 3 are explanatory diagrams illustrating the relationship between the image carrier and the blade cleaning means. A schematic diagram of the device for measuring dynamic viscoelasticity. Figure 5 shows the dynamic viscoelasticity data of rubber elastic materials. Figure 6 shows the correlation when performing actual machine tests using each of the rubber elastic materials listed in Figure 5. Figure 1: Image carrier (photosensitive drum) 2: Charger 3: Exposure means 4: Rotating developing unit 4Y: Yellow developer 4M: Magenta developer 4C: Cyan Developing device 4B...Black developing device 5...Transfer drum 6...Transfer charger 7...Separation charger 8...Transfer material 9...Fixer 10...Cleaning means II...・Cleaning plate 20...Sample 21...Chuck 22...Manpower 23...Output

Claims (1)

[Claims] As a cleaning means for an image carrier in an image forming apparatus having a plurality of developing devices, at least one of which contains color toner having a volume average particle size of 9 μm or less, a rubber elastic material having a peak temperature of loss coefficient tan δ of 0° C. or below An image forming apparatus characterized in that a cleaning blade is used.