JPH02105183A - Developing device - Google Patents

Abstract

PURPOSE:To evade the generation of a sleeve ghost by providing a resin layer which contains conductive particulates on the surface of a developer carrier. CONSTITUTION:The resin layer 18 which contains the conductive particulates is provided on the surface of the developer carrier 17. Therefore, when a voltage applied to an electrode brought into soft contact with the surface of said resin layer 18 is <=5V, the flowing current increases and the ratio of the applied voltage and current is made nearly constant up to a low applied voltage of 1,000microvolts. Consequently, contamination on the developer carrier 17 with a developer is reduced or prevented and the positive sleeve ghost is eliminated or reduced to obtain an image of high picture quality.

Description

[Detailed Description of the Invention] - 1 The present invention relates to a developing device for forming a latent image on an image bearing member such as an electrophotographic photoreceptor or an electrostatic recording dielectric material and making the latent image visible. In particular, the present invention relates to a developing device equipped with a developer carrier that supports and transports the developer in the developer container from the developer container to a developing area facing an image carrier.

[In the past, lt' of electrophotographic photoreceptors or electrostatic recording dielectric materials, etc.
Various developing devices have been proposed for image forming apparatuses that form If* on a carrier using an electrophotographic method or an electrostatic recording method, and visualize the latent image using a developing device. , a developing device illustrated in FIG. 9 is commonly used.

Referring to FIG. 9, the developing device 10 includes a developer container 12, which is disposed facing the image carrier l, and which stores the developer 11. The developer carrier 14 carries and conveys the developer from the developer 12 to the developing area 13 facing the image carrier l. The developer carrier 1
4 may have any structure, but is usually formed of a non-magnetic material in the shape of a sleeve or an endless belt, and a magnet 15 is disposed inside (the developer carrier 14 is usually Since it is sleeve-shaped, it will be simply referred to as "
(referred to as "developing sleeve"), aluminum or stainless steel is used as the non-magnetic material. Also, the developing device
O regulates the developer 11 carried by the developing sleeve 14 and conveyed to the developing area 13 to a predetermined thickness.
4): Developer regulating member 1 to form a developer S layer on
It is equipped with 6.

Such a developing device uses an l-component magnetic toner as a developer and is suitable for visualizing a latent image on an image carrier by jumping development.

In addition, the l-component magnetic toner subjected to jumping development contains a substance 2 for controlling the amount of charge (hereinafter referred to as "tolipo") of the l-component magnetic toner so as to increase the image density and obtain an image with less roughness. For example, vapor phase silica (hereinafter “
For example, for a negative polarity toner containing 60 parts by weight of magnetite in styrene acrylic, Dry silica exhibiting strong negative characteristics (compared to 100rn' vapor phase silica, HM
DS is added externally at a rate of 10 ji'T (J parts) per 100 rn' and heat treated.

Furthermore, as mentioned above, the developing sleeves in conventional developing devices are made of metals such as aluminum and stainless steel S:t4JFA, but an oxide film is formed on the surface of these so-called conductive sleeves. Therefore, the contact resistance when coming into contact with the developer exhibits a considerably high value in the low electric field caused by the toner.

However, in the case of a developer to which silica, which has strong negative properties, is externally added to a negative toner, a sleeve ghost, which is the history of the print pattern, occurs on the developing sleeve, and this also appears on the printed image. The sleeve ghost that occurs in the case of a developer in which negative silica is externally added to negative toner becomes a positive ghost as shown in FIG. In other words, when printing (image production) is performed after a non-printing area (white background), the printing area will be the area (a) where only light development is performed, and the area (a) where the printing is continued and dark development is performed. (b) where this occurs, resulting in density unevenness.

According to experiments and considerations by the present inventors, it has been found that the mechanism of such ghost formation is deeply related to the layer of fine powder (particle size of 5 to 6 microns or less) formed on the developing sleeve. In other words, there is a clear difference in the particle size distribution of the lowest layer of toner on the developing sleeve between the toner consumed area and the unconsumed toner area, and a fine powder layer is formed in the lowest toner layer of the unconsumed area. I understand.

The fine toner powder that forms the fine powder layer has a large surface area per volume, so compared to toner with a large particle size, it has a larger amount of triboelectric charge per mass, and due to its own reflection force, it Strongly electrostatically constrained. For this reason, the toner on the portion where the v&powder layer is formed cannot be sufficiently triboelectrically charged with the developing sleeve, resulting in a decrease in developing ability and a sleeve ghost appearing on the image.

In this way, the present inventors have discovered that sleeve ghost is a phenomenon that occurs not only because of the formation of a fine powder layer but also because the charging of the toner is largely dependent on the frictional charging between the developing sleeve and the developing sleeve. This study was also based on new findings.

Therefore, an object of the present invention is to provide a resin layer containing conductive fine particles on the surface of a developer carrier to reduce the mirroring force acting between the fine powder toner placed near the surface of the developer carrier and the developer carrier. It is an object of the present invention to provide a developing device capable of eliminating or reducing the occurrence of sleeve ghosts and obtaining high-quality images.

Another object of the present invention is to prevent contamination of the developer carrier by developer by containing a solid lubricant or solid lubricating particles in a resin layer containing conductive particles formed on the surface of the developer carrier. It is an object of the present invention to provide a developing device which can reduce or prevent so-called durable density reduction and can always obtain high-quality images.

1. The above objectives are achieved by the developing device according to the present invention. In summary, the present invention forms a thin layer of developer on the surface of a developer carrier, and forms a thin layer of developer on the surface of the developer carrier.

A developing device that transfers developer from the surface of the developer carrier to the surface of the image carrier while maintaining a small distance between the surface of the image carrier carrying the latent image and visualizes the latent image. The developer carrier has a conductive fine particle-containing resin layer formed by dispersing conductive fine particles in a resin on the surface of the developer carrier. When the voltage applied to the electrode in soft contact with the surface is less than 5 volts, the flowing current increases compared to the case where the conductive fine particle base A1 resin layer is not provided, and The ratio of applied voltage and current is 100
This developing device is characterized in that the voltage remains almost constant even when low voltage is applied down to 0 microvolts.

According to a preferred embodiment of the present invention, the volume resistivity of the conductive fine particle-containing resin layer on the surface of the developer carrier is 10.
The conductive fine particles are within a range of 20 cm or less and are configured to protrude from the surface. More preferably, the conductive fine particles contain a solid lubricant or solid-to-solid conductive fine particles.

Example 1 Next, the developing device according to the present invention will be explained in more detail with reference to the drawings.

FIG. 1 shows an embodiment of an image forming apparatus to which the developing VTM according to the present invention is applied. It has a carrier l. Around the image carrier l, there is an electrostatic latent image forming section 20°.A developing device tO1 that visualizes the latent image on the image carrier 1 transfers the visualized image on the image carrier l to a transfer material. Transfer separation unit 30 for transferring. A cleaning section 40 for cleaning residual developer on the image carrier l is arranged. Latent image forming section 20. Transfer section 30. Cleaning section 4
Since 0 is well known to those skilled in the art, further detailed explanation will be omitted.

The developing device 10 includes a developer container 1 for storing developer.
2, and a developer carrier 14 that supports and transports the developer in the developer container 12 from the developer container 12 to a developing area 13 facing the image carrier l. The developer carrier 14 is formed into a sleeve shape in this embodiment, but it can also be formed into an endless surface H/l-U', and a magnet 1 is installed inside.
5 is placed.

Further, the developing device 310 is provided with a magnetic blade 16 that regulates the thickness of the developer layer on the developer carrier 14 together with opposing magnetic poles.

From inside the developer container 12 to the developing area 13 on the developer carrier 14
The developer 11 conveyed to the developer 11 is made into spikes by the developing magnetic pole of the magnet 15, and a power source (not shown) connected to the developer carrier 3 separates the latent image on the image carrier l from the developer carrier. The developer on the developer carrier 14 flies to the image carrier l by an electric field, preferably an alternating electric field such as an AC field, formed between the image carrier 14 and the image carrier 14, and the image on the upper body of the image carrier 1 is visualized. .

According to the present invention, as shown in FIG. 2, the developer carrier 14 has a resin layer 18 on the surface of a conductive developer carrier 17 containing conductive fine particles having an average particle size of about 20 millimicrons. The conductive fine particle-containing resin layer 18 has an average volume resistivity of less than 1020 cm to 10-2 Ωcm.
Furthermore, the conductive fine particles are in the range of 10g0cm or less, preferably in the range of 7XIO to 7X10 = Ωcm, and the conductive fine particles are on the surface layer, and the secondary layer is formed so that the outermost layer has a gravel road shape. It is composed of distributed particles.

As will be described later, when the metal conductive developer carrying member 17 constituting the developer carrier 14 is made of non-magnetic aluminum or stainless steel, as shown in FIG. An oxide film layer 19 is usually formed on the surface of the metal developer supporting member 17, but the present invention is also applied to such a developer carrier 14, and the oxide film layer 19 is formed on the surface of the metal developer supporting member 17.
A conductive fine particle-containing resin layer 18 as described above is formed thereon.

Next, the formulation of the conductive fine particle-containing resin layer of this example will be explained.

(Formula 1) Resin: Phenol resin (solid content) 30 parts by weight Carbon: CONDUCTEX 975 UB (manufactured by Columbian Carbon) 25 parts by weight Diluent: 200 parts by weight of methyl alcohol Methyl cellosolve Prepared with the above composition The resin liquid is applied to 7 random #
Approximately 1.0 pm-1,51 L is applied to the surface of a developer carrier made of aluminum that has been blasted at 400° C.
In this example, since a phenol resin was used as the resin, heat curing was performed at 150° C. for 30 minutes in a drying oven.

The surface resistivity and volume resistivity of the resin layer containing conductive fine particles at this time are the resistivity of the resin layer containing conductive fine particles formed on PET (polyethylene terephthalate) under the same film formation conditions. In this example, the resistance was about 7.0XIQ-1 Ωcm, which was obtained by measuring with a Loresta AP Intelligent manufactured by Yuka.

Next, the contact resistance between the developer carrier 14 and the developer according to this example was examined using the measurement method described below.

FIG. 4 shows the measuring device, and FIG. 5 shows the direction of the current flowing through the developer carrier 12 during measurement.

In this measurement, a minute voltage was applied to the voltage application brush 52 by a minute voltage application device and a minute voltmeter 51 while the developer carrier 14 was rotated in the direction of the arrow at about 1100 rpm. The voltage application brush was made from Azuma Trading Card (carbon brush), and each filament that made up the brush had a diameter of about 5 microns and a length of about 8 mm, ll! Approximately 5m
m, the total weight of the brush was approximately 10 m g.

Further, the current from the developer carrier 14 is passed through the current drawing brush 5.
3, and measured using a microcurrent meter 54. At this time, the distance between the voltage application brush 52 and the current drawing brush 53 was about 150 mm.

The current I flowing with respect to the applied voltage V is measured using the above measuring device, and the so-called V-1 measurement is performed in the range from 100 microvolts to several volts, and the contact resistance of the surface of the developer carrier 14 is determined. It was measured.

By examining the V-1 characteristics obtained in this way, we found that the conventional developer carrier cannot actually be expressed as V=IXR (R is resistance) for a microvoltage of several volts or less.
The barrier was often formed by a fairly resistive oxide layer. However, even in such a conventional developer carrier, according to the present invention, a conductive fine particle-containing resin layer of this embodiment is formed on the surface of a developer carrier having a conventional barrier layer, thereby reducing the 10-0 micron size. It has been found that V=I

In addition, in this experiment, the layer thickness of the conductive fine particle-containing resin layer was examined at a film thickness of 0.5 microns to 30 microns, but within the scope of this experiment, as shown in Figure 5, the thickness of the resin layer containing conductive particles was It is thought that the flow is mostly &-*)1→d→f.

Figure 6 shows the conventional developer carrier measured by the V-I measurement device related to the experiment and the developer of this example in which the conventional developer carrier was coated with a resin layer containing conductive fine particles. The V-I characteristics of the support are shown (curve (a) is for the conventional example, curve (a) is for the conventional example,
b) shows the present example), and the experimental results shown in FIG.
86 Botensiostat (manufactured by Toyo Technica Co., Ltd.)
The two-terminal method was used.

FIG. 6 shows that the conventional developer carrier does not satisfy the so-called equation (■=IXR), and the slope of the curve is high in the low voltage region, indicating that the resistance is high. Also, as the voltage increases,
It can be seen that the slope is gentle. In the case of this example, the voltage radio wave changes linearly, forming a resin layer containing conductive fine particles, and furthermore, the conductive fine particles protrude from the surface. It is understood that because of this structure, the resin layer serves as a charge leak site.

The developer carrier of this example was incorporated into a developing device having the structure shown in FIG. 1, and was attached to an image forming apparatus, which is an electrophotographic copying apparatus, to produce an image. Development was performed using a non-contact jumping development method. The developing bias is AC bias Vpp 1600V, frequency 1800V.
Hz, and the distance between the developer carrier and the image carrier was approximately 300 microns.

Further, in the image development experiment of this example, a one-reversal development system was used, using a negative polarity developer in which positive ghosts are relatively likely to appear.

In an image forming apparatus configured to have a developer carrier according to the present invention, whether or not there is a positive ghost in the obtained image,
There were very few. On the other hand, when images were produced by incorporating a developing device having a conventional developer carrier, positive ghosts appeared considerably.

This means that the developer carrier constructed according to the present invention is the sixth
As shown in the figure, this is due to the property of making it easier for the charge to move from the developer to the developer carrier even under a low voltage of 1 volt or less. It is thought that the positive ghost reduction effect was obtained because the charge of the fine powder was lowered, the mirroring force of the developer itself was reduced, and the fine powder became easier to separate from the developer carrier.

The present invention obtains its effects by coating a conventional developer carrier in a thin layer as in this embodiment.

Conventional conductive developer carriers use metals such as aluminum and stainless steel (SO3), and if one looks closely, one surface is oxidized. This is as shown in FIG. 3.The present invention is capable of forming a resin layer containing conductive fine particles on a developer carrier having an oxide film with a relatively low barrier on its surface. Similar effects can be obtained by doing this.

In other words, when a conductive fine particle-containing resin layer is provided on the surface, the conductive fine particles protrude and become a charge leak site, which causes the oxide film to deteriorate. This is thought to be because the barrier can be penetrated.

By further imparting surface lubricity to the conductive fine particle-containing resin layer described in the above embodiment, the effect of reducing positive ghosts is ensured, and the development rate increases as the operating time of the developer increases. It becomes possible to reduce contamination caused by the developer on the agent carrier.

An example is as follows.

(Formulation 2) Resin: Phenol resin (solid content) 15 parts by weight Carpore-C0NDUCTEX UB (Columbian Carbon) 15 parts by weight Conductive lubricant (7pm) 15 parts by weight Diluent: Methyl alcohol Methyl Sorosolve 225 parts by weight The resin liquid prepared with the above composition was coated with the coating method, Day! The surface of the developer carrier made of aluminum was blasted with 7 random #400 by the ping method or the spray method, and was coated with a thickness of about 6 pm. Next, in this example, a phenol resin was used as the resin. For use, heat curing was performed at 150° C. for 30 minutes in a drying oven.

The surface resistivity and volume resistivity of the resin layer containing conductive fine particles at this time are the resistivity of the resin layer containing conductive fine particles formed on PET (polyethylene terephthalate) under the same film formation conditions. In this example, the value was approximately 7.0 x 10-1 Ωcm, which was obtained by measuring with Yuka's Loresta AP Intelligent. , the effect of reducing contamination of the developer carrier by the developer was remarkable. That is, by imparting solid lubricity to the surface of the developer carrier, it was possible to prevent the durability of the density from decreasing. This is thought to be because the surface of the developer carrier has lubricating properties, making it difficult for contaminants to adhere to the surface.

The above effect can also be obtained by applying a resin containing conductive fine particles obtained by the following formulation onto the surface of the developer carrier.

(Formulation 3) Resin: Phenol resin (solid content) 15 times conductive lubricant for double junctions, 15 parts modified artificial graphite (IuLm) Diluent, 225 parts methyl alcohol methyl solosolve 1 bottle Prepared using the following formula: The resistivity of the conductive fine particle-containing resin layer film was approximately 7.0XIO-'Ωcm. Also, regarding graphite, I tried changing the particle size, but the result was 0.
．． It worked effectively regardless of whether it was artificial or natural from 37 zm to 7 pm.

Furthermore, the same effect could be obtained even when a solid lubricant was used as the lubricant. The prescription at that time was as follows.

(Formulation 4) Resin: Phenol resin (solid content) 15! 1 part carbon CON [1 UCTEX 975 II B (
Columbian Carbon Co.) 15 parts by weight Solid lubricant: 15 parts by weight of molybdenum disulfide Diluent: 225 parts by weight of methyl alcohol methyl solosolve In addition to molybdenum disulfide, boron nitride or the like can also be used as a solid lubricant.

In each of the above examples, a phenolic resin was used as the conductive fine particle-containing resin layer forming resin, but in addition, 1. vinyl hydrochloride, vinyl acetate, a polymer of vinyl hydrochloride and vinyl acetate, polyester, polystyrene, PMMA, cellulose acetate , butyral, melamine, epoxy resin, aqueous casein, etc. can be used similarly.

Furthermore, in addition to the heat c'T plastics and thermosetting resins mentioned above, UV (ultraviolet) curing resins can be used as well. However, in the case of UV curing resin.

Considering the curing conditions, the film thickness cannot be made very thick, but it can be made sufficiently thick by using it in combination with a thermosetting resin or a thermoplastic resin.

In the above description, a negative developer was used as the developer, but it will be obvious that a positive developer can be used as well.

Furthermore, in the above embodiments of the present invention, aluminum sandblasted with 7 random #400 was used as the developer carrier metal, but the same effect can be obtained by using aluminum after drawing processing. Furthermore, other metals besides aluminum may also be used.

The configuration of the developing device according to the present invention is not limited to the configuration shown in FIG. 1, and as shown in FIGS. 7 and 8, a rigid magnetic blade may be used as the developer layer thickness regulating member. with an elastic blade.

Alternatively, a metal plate or the like may also be used.

&1 Standing J As explained above, in the developing device according to the present invention, a layer in which conductive fine particles are dispersed in a resin is formed on the surface of the developer carrier, and a layer containing conductive fine particles is formed on the surface of the conductive fine particle-containing resin layer. When the voltage applied to the electrode in soft contact is less than 5 volts, the flowing current increases compared to the case where the conductive fine particle-containing resin layer is not provided, and the applied voltage Since the ratio of current to current is almost constant for low voltage applications down to too many microvolts, positive sleeve ghost can be eliminated or significantly reduced, resulting in high image quality. It has the advantage of being able to obtain images of

Furthermore, according to the present invention, by containing solid slippery fine particles in the conductive fine particle-containing resin layer, contamination of the developer carrier by the developer can be reduced or prevented. It prevents a decrease in durable density and allows you to always obtain high-quality images.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing an embodiment of an image forming apparatus equipped with a developing device according to the present invention. 2 and 3 are partial cross-sectional views of a developer carrier constructed according to the present invention. FIG. 4 is an explanatory diagram illustrating the outline of a measuring device for measuring the resistivity of a developer carrier. FIG. 5 is an explanatory diagram showing the mode of current flowing on the surface of the developer carrier. FIG. 6 is a graph showing the VI characteristics of a developer carrier configured according to the present invention and a conventional developer carrier. 7 and 8 are cross-sectional views of other embodiments of the developing device constructed according to the present invention. FIG. 9 is a sectional view of a conventional developing device. FIG. 10 is a plan view of a copy for explaining sleeve ghosts. 1: Image carrier 1O: Developing device 12: Developer container 13: Developing area 14: Developer supporting member 17: Developer supporting member 18: Resin layer containing conductive fine particles Fig. 2 Fig. 3 Fig. 6 Current No. 8 Figure 9 Figure 1o Figure

Claims (1)

[Claims] 1) A thin layer of developer is formed on the surface of a developer carrier, and a minute gap is maintained between the surface of the developer carrier and the surface of the image carrier carrying a latent image. The developing device transfers a developer from the surface of the developer carrier to the surface of the image carrier to visualize a latent image, and the developer carrier includes conductive fine particles dispersed in a resin. By having a resin layer containing conductive fine particles formed on the surface of the developer carrier, a voltage of less than 5 volts is applied to an electrode that is brought into soft contact with the surface of the resin layer containing conductive fine particles. On the other hand, the flowing current increases compared to the case where the conductive fine particle-containing resin layer is not provided, and the ratio of the applied voltage to the current is almost equal to the applied voltage up to 1000 microvolts. A developing device characterized by being constant. 2) The conductive fine particle-containing resin layer on the surface of the developer carrier has a volume resistivity in a range of 10^2 Ωcm or less, and the conductive fine particles protrude from the surface. Developing device. 3) The developing device according to claim 1 or 2, further comprising a solid lubricant or solid lubricating conductive fine particles.