JPH04269777A - Non magnetic one component developing device - Google Patents

Abstract

PURPOSE:To obtain a good image by forming a stable toner layer on a developing roll. CONSTITUTION:A thin layer roll 3 is formed with a conductive material. The stable toner layer can be formed on an outer periphery surface of the roll 2a even when the developing roll 2 is electrified excessively making an unstable state in the formation of the toner layer by destaticizing with the effect of AC component by impressing voltage of DC component which is the same polarity as the impressed voltage on the developing roll 2 but with greater absolute value superimposed with the AC component on the beforementioned thin layer roll 3.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device using non-magnetic one-component toner used in copying machines, printers, etc.

0002

[Prior Art] In a developing device using non-magnetic single-component toner, in order to obtain high image quality, it is suitable to develop by bringing the developing roller into contact with the photoreceptor (touchdown development). When a developing roller with low resistance is used, background stains tend to occur, so it was necessary to use a material with a certain degree of high resistance for the developing roller, or to form a high-resistance layer on the outer circumferential surface. .

0003

[Problems to be Solved by the Invention] However, when a high-resistance material is used for the developing roller or a high-resistance layer is formed on the outer peripheral surface, the developing roller itself becomes electrically charged and There have been cases where the toner layer applied becomes unstable, resulting in poor images.

[0004] Also, in the developing device, for example,
As seen in Japanese Patent No. 174861, a blade-shaped thin layer control device consists of an electrode layer made of a conductive material to which an AC voltage is applied, and an insulating layer laminated on the electrode layer so as to be placed on the photoreceptor side. It has also been proposed to vibrate the member in synchronization with the frequency of the AC voltage, thereby forming a thin and uniform toner layer on the surface of the photoreceptor without forcing the regulating member into strong pressure contact with the developing roller. However, in the case of such a blade-type thin-layer regulating member, it is inferior to a roller-shaped thin-layer regulating member (thin-layer roller) in terms of stability in forming a toner layer, and it is difficult to apply an AC voltage to it. In some cases, there was little effect.

The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to form a stable toner layer on a developing roller so that high-quality images can be obtained.

[0006]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention uses a developing device as described above, in which the toner on the developing roller is scraped off by rotating in a direction opposite to the rotating direction of the developing roller. A thin layer roller is provided to form a thin toner layer, and the thin layer roller is made of a conductive material, and a DC component and an AC component having the same polarity and a larger absolute value than the voltage applied to the developing roller are provided. is applied, and the circumferential speed of the photoreceptor is Vp (mm/
sec), and the nip width between the photoconductor and the developing roller is L(
mm/sec), the frequency f(
Hz) satisfies the condition f≧Vp/L.

[0007] In this non-magnetic one-component developing device,
The voltage application part of the developing roller is made of metal, and the resistance between the voltage application part and the outer peripheral surface of the roller is 100MΩ.
It is preferable to provide a resistor layer so as to have a thickness of cm or more, or to form the outer peripheral surface of the developing roller from a polymeric material such as rubber or resin.

[0008]

[Operation] According to the developing device configured as described above, by applying to the thin layer roller a voltage in which an AC component is superimposed on a DC component having the same polarity as the voltage applied to the developing roller and a larger absolute value than the voltage applied to the developing roller, even if the developing Even when the roller is excessively charged at low temperature and low humidity and is in an unstable state regarding the formation of a toner layer, the AC component removes the charge and forms a stable toner layer in an appropriate state on the outer peripheral surface. This allows you to always obtain high-quality images. Since the voltage applied to the thin roller is larger in absolute value than the voltage applied to the developing roller, the thin roller not only regulates the toner on the outer peripheral surface of the developing roller into a thin layer, but also charges the toner. Since it also plays the role of imparting electricity, the amount of charge on the toner increases overall, making it difficult for background smudges to occur.

[0009] The developing roller has a voltage application section made of metal, and a resistor layer is provided on the outside so that the resistance between the voltage application section and the roller outer circumferential surface is 100 MΩcm or more. If the side is made of a polymeric material such as rubber or resin to provide a high resistance element, it is possible to prevent background smudges that tend to occur when the resistance of the developing roller is low.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing a non-magnetic one-component developing device according to the present invention.

This developing device is a non-magnetic one-component developing device that develops by bringing a developing roller 2, which has toner adsorbed onto its outer peripheral surface, into contact with a drum-shaped photoreceptor 1 carrying a latent image on its surface. Arrow B which opposes the rotation of roller 2 in the direction of arrow A
A thin layer roller 3 is provided below the developing roller 2, and the thin layer roller 3 is made of stainless steel (SUS),
It is made of a conductive material such as aluminum (Al).

A DC component having the same polarity (negative polarity in this example) as the voltage applied to the developing roller 2 by the DC power supply 17 and a larger absolute value is applied to the thin layer roller 3.
The voltage with the C component superimposed is applied to the DC power supply 15 and the AC power supply 16.
The detailed explanation will be given later, but when the circumferential speed of the photoreceptor 1 is Vp (mm/sec) and the nip width between the photoreceptor 1 and the developing roller 2 is L (mm/sec),
The frequency f (Hz) of the above AC component is f≧Vp/L
We are trying to meet the following conditions.

The developing roller 2 has a developing roller shaft (core metal) 4, which serves as a voltage application section, formed of metal, and has a resistance of 100 MΩc between the developing roller shaft 4 and the roller outer peripheral surface 2a on the outside thereof.
A resistor layer 5 is provided so that the resistor layer 5 is equal to or more than m.
is made of polymeric materials such as rubber and resin.

This developing device includes a toner cartridge section 7.
The toner T inside is scraped out by the conveying member 8 to the toner supply chamber 9 in which the developing roller 2 is housed, and the toner T sent into the toner supply chamber 9 is stirred by the stirring member 6 rotating in the direction of the arrow. and is sent to the supply roller 11 rotating in the direction of arrow C.

The supply roller 11 is made of a conductive elastic member such as carbon-containing urethane foam.
A negative voltage is applied to the rotating shaft by the DC power supply 18,
Amount L1 of the outer circumferential surface biting into the developing roller 2 =
They are pressed together with a pressure of about 1mm.

The developing roller 2 and the supply roller 11 are designed to have a linear velocity difference at their contact portions, thereby efficiently frictionally charging the toner. The toner charged by the friction is electrostatically attracted to the developing roller 2, and is carried toward the thin layer roller 3 rotating in contact with the lower part of the developing roller 2.

As mentioned above, the thin layer roller 3 is made of metal and is applied with a bias voltage, and is pressed against the developing roller 2 at a pressure of, for example, about 50 g/cm. It rotates in the direction of arrow B, which is opposite to the rotational direction of the developing roller 2, and mechanically scrapes off the toner adsorbed on the outer peripheral surface of the developing roller 2 to a predetermined thickness (thin layer).

The toner, which has been made into a thin layer by the thin layer roller 3 and has been sufficiently charged, is carried over the developing roller 2 in the direction of arrow A and comes into contact with the photoreceptor 1, thereby causing the toner to be deposited on the photoreceptor. The electrostatic latent image formed on the surface of 1 is developed. It should be noted that the method of developing by bringing the developing roller 2 into contact with the photoreceptor 1 as described above provides a high-quality image with excellent resolution compared to the developing method in which a gap is provided between them.

By the way, when a material with low resistance is used for the developing roller 2, reverse charge is injected into the toner, which tends to cause background stains. Therefore, it is common practice to use a developing roller with a high resistance value as a whole, or to have a multilayer structure with high resistance on the outer peripheral surface side. The specific resistance value required to prevent the background smudge is generally 100 MΩ between the developing roller shaft 4 and the roller outer circumferential surface 2a shown in FIG.
It is desirable to make it more than cm.

However, when a developing roller with a high resistance value is used, the developing roller is strongly charged due to friction with the supply roller, and most of the toner is removed from the outer circumferential surface of the roller due to the electrical action in the thin roller section. It's easy to get scraped off. In this case, toner cannot be sufficiently supplied to the developing section, resulting in a decrease in density of the developed image.

FIGS. 3 and 4 are diagrams showing the potentials of various parts when the developing device is operating normally (FIG. 3) and when the developing roller is excessively charged (FIG. 4). in general,
The voltage applied to the supply roller and the thin layer roller takes a large value (in absolute value) toward the toner polarity side with respect to the core metal of the developing roller shaft. By doing so, the supply roller also acts to supply toner, and the thin layer roller not only regulates the layer thickness of toner excessively attracted to the outer peripheral surface of the developing roller to an optimal thickness, but also imparts an electric charge to the toner. As a result, the toner charge amount increases overall, making it difficult for background smudges to occur (as background smudges tend to occur when toner is in a low-charged state).

In a developing device having such a thin layer roller, when the developing device is operating normally, the outer circumferential surface of the roller changes relative to the core metal potential of the developing roller shaft portion, as shown in FIG. Since the electrical charge (charged part of the developing roller) is not so large, the potential of the toner layer adhering to the developing roller is large and its adhesion is strong, so the thin roller regulates the toner layer to an appropriate layer thickness. can be sent to the developing section that comes into contact with the photoreceptor.

However, when the developing roller is strongly charged by the supply roller, for example, when the coefficient of friction becomes large, such as in a high temperature and high humidity environment, or when the resistance of the developing roller becomes large, as in a low temperature and low humidity environment, , as shown in FIG. 4, the charge on the outer circumferential surface of the roller (the charged portion of the developing roller) is greater than the core metal potential of the developing roller shaft, so the potential of the toner layer adhering to the outer circumferential surface is small. Since the adhesion is weak, most of the toner layer is scraped off by the thin layer roller. Therefore, it becomes impossible to send the amount of toner necessary for optimal development to the developing section.

On the other hand, depending on the materials of the developing roller and supply roller, the charging polarity of the developing roller may appear in the opposite direction to the toner polarity, and in such cases, the toner regulating force of the thin layer roller is also reduced. At the same time, low-charged toner is sent to the developing section, making it impossible to obtain high-quality images.

However, in this embodiment, as described above, a voltage in which an AC component is superimposed on a DC component having the same polarity as the voltage applied to the developing roller 2 and a larger absolute value than the voltage applied to the developing roller 2 is applied to the thin layer roller 3. Even if the roller 2 is excessively charged at low temperature and low humidity and is in an unstable state regarding the formation of a toner layer, the charge is removed by the action of the AC component and an appropriate toner layer is formed on the outer peripheral surface 2a. This allows you to always obtain high-quality images.

The potential of each roller and the resistance value of the developing roller 2 are set to, for example, the following values, and the method of measuring the resistance value of the developing roller 2 at that time is as shown in FIG. A measuring electrode 13 with a width L2 = 1 cm is connected between a pair of grounded guard electrodes 12, 12 provided on the outer circumferential surface 2a of the developing roller 2 at intervals in the axial direction. This is done by connecting the anode (+) side of the DC power supply 19 to the developing roller shaft (core metal) 4 via an ammeter 20.

Core metal potential of developing roller shaft -300V Supply roller potential -600V Thin layer roller potential -600V+AC500V
(200Hz) (Peak-Peak) Developing roller resistance 1000
As a result of setting 0 MΩcm in this way, the experimental results shown in Table 1 were obtained.

From this experimental result, it was found that an appropriate amount of toner was applied on the developing roller 2 (0.4 mg on the surface of the developing roller 2).
/cm2 to 0.8 mg/cm2), it is desirable to lower the surface potential of the outer circumferential surface 2a of the developing roller 2 by about 50V to 80V with respect to the DC portion of the thin layer roller potential.

[0029]

[Table 1]

By the way, when an AC voltage is applied to the thin layer roller 3, a wavy toner layer is formed on the developing roller 2 according to the cycle T of the AC voltage as shown in FIG. Such a wavy toner layer can also be formed in a system using, for example, magnetic toner and a finely magnetized sleeve.
Although there is no practical problem when applied to an actual developing device, in that case it is necessary to select an appropriate frequency of the AC component.

That is, the nip width between the developing roller and the photoreceptor is L (mm), the peripheral speed of the photoreceptor is Vp (mm/sec), and the peripheral speed of the developing roller is Vd (mm/sec): However, the contact with the photoreceptor Assume that they are rotating in the same direction at the same position.

When the frequency of the AC component is f (Hz), the time it takes for the photoreceptor to pass through the nip width is L/Vp, and the distance the developing roller rotates within that time (L/Vp
)×Vd is the distance between the toner peaks Vd/f (1/f
= AC component period T) is smaller than the condition (L/Vp
)×Vd≦Vd/f It is necessary to determine the frequency f so as to satisfy the inequality f≧Vp/L.

As a specific example, Vp=92 (mm/sec
), Vd=144 (mm/sec), L=0.5 (mm
), the frequency f of the AC component is f≧92/
0.5 to f=184 (Hz) or higher.

[0034]

As explained above, according to the present invention, an AC component having the above-mentioned predetermined frequency is superimposed on a DC component having the same polarity as the voltage applied to the thin layer roller and having a larger absolute value than the voltage applied to the developing roller. Since we apply a voltage of
Even if the developing roller is excessively charged and is in an unstable state for forming a toner layer, the action of the AC component removes the charge and forms a stable toner layer in an appropriate state on its outer peripheral surface. As a result, you can always obtain high-quality images.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a non-magnetic one-component developing device showing an embodiment of the present invention.

FIG. 2 is a perspective view for explaining a method of measuring the resistance of the developing roller of the developing device shown in FIG. 1;

FIG. 3 is a diagram showing the potentials of various parts when the developing device is operating normally.

FIG. 4 is a diagram showing the potential of various parts when the developing roller is excessively charged.

5 is a diagram showing the relationship between the potentials of the developing roller and the thin layer roller and the wavy toner layer formed on their surfaces in the embodiment shown in FIG. 1; FIG.

[Explanation of symbols]

1 Photoreceptor
2 Developing roller 2a Roller outer peripheral surface 3 Thin layer roller 4 Developing roller shaft (voltage application part) 5
Resistor layer 11 supply roller
15, 17, 18, 19 DC power supply

Claims (3)

[Claims] 1. A developing device using a non-magnetic one-component toner that develops by bringing a developing roller, which has toner adsorbed onto its outer circumferential surface, into contact with a photoreceptor carrying a latent image on its surface, wherein the rotational direction of the developing roller is A thin layer roller is provided which rotates in a direction opposite to the direction of the developing roller to scrape off the toner on the developing roller to form a thin toner layer, and the thin layer roller is made of a conductive material, and the thin layer roller is made of a conductive material. A voltage obtained by superimposing an AC component on a DC component with the same polarity as the applied voltage and a larger absolute value than that of the applied voltage is applied, and the circumferential speed of the photoreceptor is reduced to Vp(
mm/sec), and the nip width between the photoreceptor and the developing roller is L (mm/sec), and the frequency f (Hz) of the AC component satisfies the condition f≧Vp/L. A non-magnetic one-component developing device featuring: 2. The non-magnetic one-component developing device according to claim 1, wherein the voltage applying part of the developing roller is formed of metal, and the resistance between the voltage applying part and the outer peripheral surface of the roller is 100 MΩcm or more on the outside thereof. A non-magnetic one-component developing device characterized in that a resistor layer is provided so as to have the following characteristics. 3. The non-magnetic one-component developing device according to claim 1 or 2, wherein the outer peripheral surface side of the developing roller is formed of a polymeric material such as rubber or resin. Device.