JPH07117787B2 - Development device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in an electrophotographic copying apparatus which is an image forming apparatus, a printer or the like, and more particularly to a developing apparatus using a one-component toner. Is.

Conventional technology and its problems Conventionally, a volume average particle diameter of a dry one-component magnetic toner classified product used as a developer in a developing device such as an electrophotographic copying device which is an image forming device or a printer is within a range of 10 to 14 μm. In general, in the jumping development which is a typical dry one-component magnetic toner developing method, the volume average particle diameter of the one-component magnetic toner is 12 μm. In this one-component magnetic toner, the volume average particle size of 6.35 μm or less is about 20% or less in the number distribution, and the volume average particle size of 20.2 μm or more is about 2% or less in the volume distribution. The included toner is being used.

Although this depends on the capacity and efficiency of the crushing / classifying device in the toner manufacturing process, it has been mainly determined in consideration of the balance between the charging performance and the fluidity of the toner.

However, in recent years, in order to meet the market demand for higher image quality of electrophotographic copying machines, further reduction in particle size of toner has been attempted. For example, in the case of an electrophotographic laser beam printer, the print density is 60 times the conventional 300 dpi.
In order to realize the one with the resolution increased to 0dpi (23.6pel), it is necessary to increase the resolution, sharpness, etc. to faithfully reproduce the electrostatic latent image, and it is necessary to drastically review the development process for the conventional toner with a particle diameter of about 12 μm. On the other hand, by using a toner having a particle diameter of about 8 μm to 6 μm, the above problems can be solved relatively easily. As an example of such a toner having a small particle diameter, the volume average particle diameter of the toner classified product is
It is 6.0 μm. Further, in this one-component magnetic toner, a volume average particle size of 3.5 μm or less is about 20% or less in a number distribution, and a volume average particle size of 16 μm or more is about a volume distribution. The toner and the like are contained in a proportion of 1% or less. If this toner is a positive toner containing nigrosine or the like as a charge control agent, a 0.8% silica modified with amino-modified silicone oil is added as an external additive to the toner.
It is used as a developer after being externally added in an amount of about wt%.

However, in such a toner having a small particle diameter, tribo becomes too large due to friction with the developing sleeve. That is, since the small particle diameter toner has a larger specific surface area per volume than the conventional toner, the charge amount per volume / weight increases by about 30% when measured by the two-component tribo measuring method.
As described above, since the amount of fine powder having a particle diameter of 5 μm or less is greatly increased, the resin component in these small particle diameter toners becomes abundant, and as a result, the high tribo fine powder due to these small particle diameter toners causes the developing sleeve. The surface of the developer bearing member like this is easily contaminated. Therefore, there is a drawback that the generation of sleeve ghost as shown in FIG. Here, as for the sleeve ghost shown in FIG. 5, since the fine powder layer is formed in the portion (a) of FIG. 5, the charge amount of the toner other than the fine powder layer on the developing sleeve is lowered, and the density is lowered. The part (b) is a part where the fine powder layer is removed and the concentration is recovered.

As a countermeasure against such phenomena as the occurrence of sleeve ghost and the decrease in durable density, conventionally, a scraper is brought into contact with the developing sleeve to scrape all the developed toner from the developing sleeve, or after developing. A bias is applied to electrostatically transfer the toner from the developing sleeve to the image carrier, or a metal plate or roller grounded is placed against the developing sleeve to remove the developed toner from the developing sleeve. However, all of them have a drawback that the device is complicated and the cost is increased.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a developing device capable of easily removing the toner remaining on the developing sleeve from the developing sleeve after development and preventing a sleeve ghost and a decrease in durable density. Is to provide.

Means for Solving the Problems The above object is achieved by the developing device according to the present invention. That is, in summary, the present invention has a developing container containing a one-component developer, and a developer carrier provided in the opening of the developing container to carry the one-component developer. Is a developing device that obtains tribo by friction with the surface of a developer carrier, the volume average particle diameter of the one-component developer is 4 to 9 μm, and the developer carrier is a conductive base material and this conductive base material. It is provided on the top, contains conductive particles, and has a volume resistivity of 10 ^-3 to 10 ³ Ωcm.
A developing device having the resin surface layer of

The volume average particle diameter of the developer is set to 9 μm or less and 4 μm or more because the volume average particle diameter is 19 pel or 23.6 pel when the volume average particle diameter is 9 μm or more.
This is because when reproducing the latent image of, the sharpness was not improved so much and the volume average particle size was 4 μm.
If it is less than m, it is technically difficult to stably contain magnetite in the resin, and from the viewpoint that crushing and classification are too expensive, a one-component magnetic toner having a volume average particle diameter of 4 μm or less is produced. Because it is difficult.

That is, according to the present invention, as a conductivity-imparting agent on the surface of the developing sleeve, for example, by forming a conductive resin layer containing carbon particles having a volume resistivity of 10 ⁻³ to 10 ³ Ω · cm, toner fine powder is formed. It is possible to improve the sleeve ghost and the decrease in the durable concentration due to the formation of the layer on the surface of the developing sleeve.

Embodiment Hereinafter, the present invention will be described based on an embodiment thereof with reference to the accompanying drawings.

Referring to FIG. 2, there is shown a schematic sectional view of an embodiment of a developing device according to the present invention, which is like a photosensitive drum carrying a latent image formed through a predetermined process. It is arranged adjacent to the latent image carrier 1 and develops the latent image on the latent image carrier to form a visible image. The developing device is provided with a developer hopper 3 for accommodating the developer 4, and a developer discharging opening B provided at a bottom position of the developer hopper 3 is provided with the developer 4 in the developer hopper 3. A developing sleeve 7 as a developer carrying member which is rotatable in the direction of arrow A in order to charge the developer by contact and rubbing.
Is provided. On the outer periphery of the developing sleeve 7,
A conductive resin layer 6 which will be described later in detail is formed.

At this time, since the developing sleeve 7 is arranged so as to close the developer discharge opening B, the developing sleeve 7 cooperates with the developer hopper 3 and the developer 4 stored in the developer hopper 3 is cooperated with.
Is held and the developing sleeve 7 is rotated, so that the developer can be conveyed onto the developing sleeve 7. The developing sleeve 7 contains the developing magnet 5.

Further, a cutting blade 2 made of a ferromagnetic metal is provided at the peripheral end portion extending from the upper end portion of the developer hopper 3 to form the developer discharge opening B, from the surface of the developing sleeve 7 to about 200 to 300 μm. The developing sleeve 7 is suspended in the longitudinal direction so as to face the developing sleeve 7 with a gap width of.

Here, the conductive resin layer 6 formed on the outer periphery of the developing sleeve 7 described above will be described.

This conductive resin layer 6 is, as shown in FIG.
It is formed on the surface of the developing sleeve 7 as a developer carrying member, and is composed of a resin layer containing conductive fine particles such as carbon powder having an average particle diameter of about 20 mm, The layer, that is, the conductive resin layer 6 has an average volume resistivity in the range of 10 ⁻³ to 10 ³ Ω · cm, a thickness of 1.0 μm to 20 μm, and the conductive fine particles are surface layers. In addition, the conductive fine particle layer has a size of secondary particles of 1.0 micron or less due to the conductive fine particles and the resin.

The content of the conductive fine particles contained in the conductive resin layer 6 for imparting conductivity is 30 to 70.
% By weight. At that time, 30 to 100% by weight of carbon graphite may be contained in the conductive fine particles such as the above-mentioned carbon powder.

In order to form such a conductive resin layer 6 on the outer surface of the developing sleeve 7, a conductive paste having the components described below is applied and coated on the outer surface of the developing sleeve 7 by a spray method or a dip method. Thus, the conductive resin layer 6 was formed on the surface of the developing sleeve 7.

That is, the carbon powder used as the conductive fine particles is
We chose a type with a highly developed carbon molecule structure and high electrical conductivity, and used a thermosetting phenolic resin as the binder.

(Components of conductive paste) Resin: Phenolic resin 50 parts by weight Carbon · · CONDUCTEX900 50 parts by weight Colombian Carbon Diluents · · Methyl alcohol Others methyl cellosolve 250 parts by weight At this time, it is formed on the developing sleeve 7. The thickness of the conductive resin layer 6 was about 4 μm.

Thus, using the developing device having the developing sleeve 7 having the conductive resin layer 6 formed on the outer periphery of the developing sleeve 7 like the developing device according to the present invention, the photosensitive drum 1
The latent image formed above was developed using a small particle size toner as a developer in a low humidity environment where the sleeve ghost is the most severe, and as a result of evaluating the occurrence of the sleeve ghost, as compared with the conventional metal conductive sleeve, The occurrence of ghosts has been greatly reduced.

The toner used in the above examples was mainly composed of a styrene-acrylic copolymer, 90 parts by weight of magnetite as a magnetism-imparting agent and 2 parts by weight of nigrosine as a charge control agent, and then pulverized and classified. A dry one-component positive toner having a volume average particle size of 6 μm, a volume average particle size of 3.5 μm or less is 20% or less in number distribution, and a volume average particle size of 16 μm or more is 1% or less in volume distribution. .
0.8 parts by weight of amino-modified silicone oil-treated silica is externally added to this toner-classified product in order to increase the fluidity and stabilize the toner charge, and the resulting product is used as a developer.

Now, let us consider how to reduce the occurrence of the sleeve ghost when developing is performed using the developing device having the developing sleeve according to the present invention.

That is, the charge-up of the toner itself near the surface of the developing sleeve can be carried out by the method of leaking to the developing sleeve in the present invention. So far, various surface treatment methods have been proposed for the conventional developing sleeve, but these are mainly macroscopic development in the developing process, and a method of positively providing a so-called leak site in the insulating toner. is not. In contrast,
According to the present invention, in the developing sleeve as the developer carrying member, by mixing and arranging the conductive fine particles and the fine particles having the surface lubricity in the portion in contact with the toner as described above, the charge leak in the insulating toner is prevented. It was made possible.

Originally, the developing sleeve in the insulating toner used was a conductive sleeve, which is a well-known fact. However, when small-sized toner is used, the sleeve ghost becomes worse than before because the fine powder toner is strongly electrostatically attracted to the surface of the developing sleeve due to its own mirroring force as described above. This is because
In the present invention, the charge of the fine powder toner adsorbed on the developing sleeve is easily leaked after the development. From a macroscopic point of view, this is considered to be a reduction in the contact resistance between the toner and the developing sleeve in the present invention.

That is, in the present invention, the size of the secondary particles formed between the conductive fine particles and the resin is set to 1 μm or less, and the surface layer of the film is formed into a gravel path to apparently reduce the contact resistance. It was successful in making a leak site. On the other hand, it is considered that the conventional metal surface obtained by roughening the metal surface by sandblasting or the like did not have a preferable effect because the insulating layer of the oxide film was formed on the metal surface. Incidentally, among the metal plating, the exceptional effect was obtained only by the Au-plated developing sleeve, but this fact seems to support the inventors' estimation. Regarding the volume resistivity of the coat film, the development of charge-up occurs on a macroscopic scale in the insulating toner unless an electrically conductive sleeve is originally used, and a decrease in development density occurs with the sleeve ghost. Therefore, the range is naturally limited.

Regarding the film thickness, it is 2
The lower limit is naturally determined from the relationship of the density of leak sites due to secondary particles. Further, with respect to the upper limit of the film thickness, the conductive fine particle-containing resin layer of the present invention has a high volume resistivity with respect to a metal, and therefore it is clear that the effect decreases if the thickness is made too thick.

Next, another embodiment of the developing device according to the present invention will be described with reference to FIGS. 3 and 4.

The developing device shown in FIGS. 3 and 4 has substantially the same structure as that of the developing device shown in FIG. 2 described above. Therefore, the developing device shown in FIG. Is
The same reference numerals are given and the description thereof is omitted.

In the developing device shown in FIGS. 3 and 4, the elastic member 20 made of urethane rubber, phosphor bronze or the like is used in place of the cutting blade 2 of the above-described embodiment so that the elastic member 20 is in contact with the surface of the developing sleeve 7. As is the case with the above-described embodiment, the conductive resin layer 6'is formed on the outer periphery of the developing sleeve 7 in the developing device as well. However, the conductive resin layer 6 ′ is applied to the outer surface of the developing sleeve 7 by a spray method with a conductive paste having the components described below to coat the conductive resin layer 6 ′ on the surface of the developing sleeve 7. ′
Is formed.

(Conductive paste) Resin: Phenolic resin 50 parts by weight Carbon ・ ・ CONDUCTEX900 10 parts by weight (Colombia Carbon Co., Ltd.) Carbon graphite ・ CSPE 40 parts by weight (Nippon Graphite Co., Ltd.) Diluent ・ ・ Methyl alcohol Others Methyl Cellsolve 250 parts by weight Part At this time, the conductive resin layer had a thickness of about 6 μm, and the volume resistivity of the conductive resin layer was 5.0 × 10 ⁰ Ω · cm as measured by the four-end probe method, and its surface The resistivity is 7.3
It was × 10 ³ Ω / B.

Thus, it is formed on the photosensitive drum 1 by using the developing device having the developing sleeve in which the conductive resin layer 6'is formed on the outer periphery of the developing sleeve 7 as in the second embodiment of the present invention. The developed latent image was developed using a small particle size toner as a developer in a low humidity environment where the sleeve ghost is the most severe, and the occurrence of the sleeve ghost was evaluated. In comparison with the case of using the conductive conductive sleeve and the developing sleeve of the above-described Example 1, the density decrease and the generation of sleeve ghost were greatly improved.

The small particle size toner used in the above examples is
A negative toner containing styrene-acrylic copolymer as a main component, magnetite as a magnetizing agent in an amount of 90 parts by weight, and a monoazo metal complex as a charge controlling agent in an amount of 2 parts by weight was used. The volume average particle size of this toner classified product is 6 μm, and the volume distribution of particles having a volume average particle size of 3.5 μm or less is 20 μm.
% Or less, and the volume average particle diameter of 16 μm or more is 1% or less in volume distribution. 0.8 parts by weight of dry negative silica treated with hexamethylene disilazane was added to the toner classified product in order to increase the fluidity and stabilize the toner charge, and it was used as a developer.

Now, let us consider the decrease in the density and the decrease in the occurrence of the sleeve ghost when the development is carried out by using the developing device having the developing sleeve of the second embodiment and using the developer.

When the latent image formed on the photosensitive drum 1 is developed, this negative small particle toner has a poorer degree of both sleeve ghost and lowering of the durable density as compared with the positive small particle toner used in the above-described embodiment. . Therefore, when comparing the positive small particle size toner and the negative small particle size toner, there is a difference in the charge amount of the toner, and the negative small particle size toner has a positive small value of about −25 μc / g by the two-component tribo measurement method. It was found to be considerably higher than the particle size toner of +18 μc / g. From this, it is easily estimated that the charge amount of the fine powder toner (negative small particle diameter toner) having a volume average particle diameter of about 5 μm or less is increased, and it is considered that the negative small particle diameter toner is severe in the sleeve ghost and the decrease in the durable concentration. .

In contrast to the developer using the negative small particle size toner, in the system using the developing sleeve of the above-described embodiment, the effect of reducing the sleeve ghost and the decrease in the durability concentration is insufficient,
By developing and printing 1000 to 2000 sheets, the level was reduced to the same level as the system using a normal metallic conductive sleeve.

Therefore, when the developing sleeve was analyzed, it was found that the surface of the developing sleeve 7 was contaminated by the resin component and silica in the toner, and in fact, the surface of the developing sleeve 7 was washed or washed with water. By wiping vigorously, the image density and sleeve ghost were restored to the initial levels.

Therefore, the inventors of the present invention include carbon graphite having a solid lubricating surface, particularly a cleavable crystal surface, in the conductive resin layer, so that the physical force applied to the fine powder causes It is thought that the toner fine powder may be easily separated, so that carbon graphite is contained in the conductive paste used when the conductive resin layer is prepared as described above. As a result, the surface of the developing sleeve 7 containing carbon graphite in the conductive resin layer was not contaminated by the resin component or silica in the toner as described above even after development and printing of 10.000 sheets.

Next, another embodiment of the developing device according to the present invention will be further described.

In the above-mentioned examples, in addition to the binders of carbon and carbon graphite used in these examples, the binder includes thermosetting phenol, polystyrene, butyral, vinyl chloride vinegar, PMMA, and the like. The same effect was obtained even when a resin such as an ultraviolet curable epoxy acrylate was used.

In order to prevent a decrease in density caused by insufficient charging of toner in a high humidity environment, an elastic member 20 made of urethane rubber, phosphor bronze or the like is used as in the developing device shown in FIGS. 3 and 4. It is effective to press the developing sleeve 7 against the developing sleeve 7 to form a thin layer of the developer applied on the developing sleeve 7 to regulate the toner. that time,
When the developing device having such a configuration is used, as described above, normally, the sleeve ghost and the density decrease in the low humidity environment are aggravated, but by using the developing sleeve of the embodiment according to the present invention, Such adverse effects are greatly reduced.

Effects of the Invention As described above, according to the developing device of the present invention,
Since the toner particles can be prevented from adhering to the developing sleeve and the uniformly charged toner particle layer can be coated on the developing sleeve, that is, a proper amount of tribo can be imparted to the one-component developer having a small particle diameter of 4 to 9 μm. It is possible to solve various problems such as a sleeve ghost or a decrease in durability density due to excessive triboelectric charging as in a conventional developing device using a magnetic one-component toner.

[Brief description of drawings]

FIG. 1 is a partial schematic enlarged view partially showing a surface condition of an outer circumference of a developing sleeve used in an embodiment of a developing device according to the present invention. FIG. 2 is a schematic sectional view of an embodiment of a developing device equipped with the developing sleeve according to the present invention. FIG. 3 is a schematic sectional view of an embodiment of another developing device equipped with the developing sleeve according to the present invention. FIG. 4 is a schematic sectional view of an embodiment of still another developing device having the developing sleeve according to the present invention. FIG. 5 is an explanatory diagram of a sleeve ghost that occurs when developing is performed using a developing device having a conventional developing sleeve. 1: Photosensitive drum 2: Cut blade 4, 4 ': Developer 6, 6': Conductive resin layer 7: Development sleeve

Front page continuation (72) Inventor Keiji Okano 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Kimio Nakahata 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP 62-95563 (JP, A) JP 60-247669 (JP, A) JP 62-286070 (JP, A) JP 53-5634 (JP, A)

Claims (1)

[Claims] 1. A developer container for accommodating a one-component developer, and a developer carrier for carrying a one-component developer provided in an opening of the developer container, wherein the one-component developer is a developer carrier. In a developing device that obtains tribo by friction with the body surface, the volume average particle diameter of the one-component developer is 4 to 9 μm, and the developer carrier is provided on the conductive base material and the conductive base material. Contains conductive particles and has a volume resistivity of 10 ^-3 to 10 ³ Ωcm
A developing device having the resin surface layer of.