JPH10307469A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain excellent faithful reproducibility for an image such as a dot and a line and a satisfactory image having a constant image density, in a developing device for attaining development by guiding a developer to a developing position facing an image carrier with a developer carrier facing it with a required interval. SOLUTION: In the developing device for holding the developer on the surface of the developer carrier 11 facing the image carrier 1 on which an electrostatic latent image is formed, with the required interval Ds and carrying the developer to the developing position facing the image carrier by the developer carrier, so as to attain the development, the interval Ds at which the developer carrier 11 and the image carrier 1 face each other is in the range of 150-400 μm and as the developer carrier, the following one is used; a dielectric layer 11d constituted so that a thickness (t) is >=50 μm, a dielectric constant ε is <=10 and a value (t/ε) obtained by dividing the thickness (t) by the dielectric constant εis in the range of 10-50 μm, is formed on the surface of a conductive substrate 11c.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used to develop a latent image formed on an image carrier in an image forming apparatus such as a copying machine or a printer, and more particularly, to a developing device for forming an electrostatic latent image. The developer is held on the surface of the developer carrier provided so as to face the image carrier to be formed at a required distance, and the developer is moved by the developer carrier to a developing position facing the image carrier. The present invention relates to a developing device adapted to carry and develop.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer, various developing devices have been used to develop an electrostatic latent image formed on an image carrier. As a device, in addition to a two-component developing system including a carrier and a toner in a developer, a one-component developing system using a developer not including a carrier is known.

In such a developing device of the one-component developing system, a developer carrier is provided so as to be in contact with the image carrier, and a developing position at which the developer contacts the image carrier by the developer carrier. And a developing device of a contact developing system, which performs development by guiding the developer to the image carrier, and a developer carrier is provided so as to face the image carrier at a predetermined interval, and the developer carries the developer with the image carrier. 2. Description of the Related Art There is known a non-contact developing type developing device in which development is performed by guiding the developing device to an opposing developing position.

Here, in the case of a contact developing type developing device,
Since the developer is brought into contact with the image carrier to perform development, the reproducibility of the electrostatic latent image formed on the image carrier is excellent, but the developer is also applied to non-image portions where the electrostatic latent image is not formed. There is a problem that fogging occurs in the formed image due to the adhesion.

For this reason, conventionally, the adhesion of the developer to the non-image area has been suppressed by changing the moving speed of the image carrier and the developer carrier.

However, in such a contact developing type developing device, the developer carrier is brought into contact with the surface of the image carrier at a constant pressure, and the developer carrier and the image carrier are in contact with each other as described above. If the moving speed is different, the surface of the image carrier is worn due to the contact with the developer carrier, causing a problem that stable image formation cannot be performed.

On the other hand, in the case of a non-contact developing type developing device in which the developer carrying member is opposed to the image carrying member at a predetermined interval, as in the above-described contact developing type developing device, Although the surface is not worn by the developer carrier, the density of the formed image greatly changes due to a change in the distance between the developer carrier and the image carrier at the developing position where the image carrier and the image carrier are opposed to each other. However, for example, even when the molding accuracy of the image carrier and the developer carrier is not sufficient and the distance between the image carrier and the developer carrier slightly fluctuates, the density of the formed image varies. In addition, there is a problem that density unevenness or the like occurs.

For this reason, conventionally, at the developing position where the developer carrier and the image carrier are opposed to each other, the interval between the developer carrier and the image carrier is set to a wide interval of 400 μm or more. A method has been used in which the interval is detected by a detecting means, and when the interval changes, the developing conditions are changed.

However, if the distance between the developer carrier and the image carrier is set to be large as described above, the electric field becomes strong at the edge portion of the electrostatic latent image on the image carrier, so that a so-called edge effect occurs. However, there is a problem that only the image density of the edge portion in the displayed image is increased, and the faithful reproducibility of the image of the point or the line is deteriorated.

In the case of a one-component developing type developing device,
In guiding the developer to the developing position facing the image carrier by the developer carrier, a developer holding the developer so that an appropriate amount of the developer is guided to the developing position facing the image carrier A regulating member is pressed against the surface of the carrier, and regulates the amount of the developer held on the surface of the developer carrier by the regulating member.

However, when the regulating member is pressed against the surface of the developer holding member holding the developer to regulate the amount of the developer, the regulating member holds the developer on the surface of the developer holding member. There has also been a problem that the developed developer is broken and fine powder is generated, and the fine powder is fused to the surface of the developer carrying member or the like, resulting in streaky density unevenness in an image to be formed.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems in a one-component developing system using a developer containing no carrier.

In the present invention, the developer carrying member is provided so as to face the image carrying member at a required interval,
In a non-contact developing type developing device in which the developer is guided to a developing position facing the image carrier by the developer carrier to perform development, when the distance between the developer carrier and the image carrier is increased. As described above, the edge effect does not occur, and only the image density of the edge portion in the formed image does not increase, and the fidelity reproducibility of the image of the point or the line does not deteriorate. Even when the distance from the carrier is changed, the density and the like of the formed image are not largely changed, and a good image having a constant image density while having excellent fidelity reproducibility of point and line images is obtained. It is an object of the present invention to be able to obtain it.

In the present invention, the regulating member is pressed against the surface of the developer carrier holding the developer as described above, and the amount of the developer retained on the surface of the developer carrier by the regulating member is controlled. In the case of regulating the developer, it is an object to suppress cracking of the developer held on the surface of the developer carrier, and to obtain a good image without occurrence of streak-like density unevenness. Is what you do.

[0015]

According to the first aspect of the present invention, in order to solve the above-described problems, the developing device faces an image carrier on which an electrostatic latent image is formed with a predetermined interval. In the developing device, the developer is held on the surface of the developer carrier provided as described above, and the developer is transported by the developer carrier to a developing position opposed to the image carrier to perform development. The distance between the carrier and the image carrier is set in the range of 150 to 400 μm, and the thickness t of the developer carrier on the surface of the conductive substrate is 50 μm or more and the relative dielectric constant ε is 10 or less. The value (t / ε) obtained by dividing the thickness t by the relative dielectric constant ε is 10 to 50 μm.
The one having a dielectric layer in the range of m was used.

Here, when a developer carrier having a dielectric layer provided on the surface of a conductive substrate is used as in the developing device according to the first aspect, the developer carrier and the image carrier are supported by the dielectric layer. The electric field acting on the body becomes controlled.

The distance between the developer carrier and the image carrier is set in the range of 150 to 400 μm as described above, and the thickness t is 50 μm on the surface of the developer carrier.
m, the relative permittivity ε is 10 or less, and the value (t / ε) obtained by dividing the thickness t by the relative permittivity ε is 10 to 50 μm.
When the dielectric layer having the range of m is provided, the edge effect at the edge portion of the electrostatic latent image formed on the image carrier is suppressed, and only the image density of the edge portion in the formed image increases, The fidelity reproducibility of point and line images is not degraded, and when the distance between the developer carrier and the image carrier fluctuates, the fluctuation of the density of the formed image is also suppressed. Thus, a good image having a constant image density can be obtained.

Here, the thickness t of the dielectric layer is set to 50 μm.
m and the relative permittivity ε of 10 or less are such that when the thickness t of the dielectric layer becomes thinner or the relative permittivity ε becomes higher than this, the electric field control by the dielectric layer becomes more difficult. This is because when the distance between the developer carrier and the image carrier fluctuates, the density of the formed image is likely to be uneven.

Further, the thickness t of the dielectric layer is set to a relative dielectric constant ε.
The value (t / ε) divided by 10 is set to be in the range of 10 to 50 μm because when the value of t / ε is smaller than 10,
The electric field in the dielectric layer cannot be sufficiently controlled, and an image formed due to a change in the distance between the image carrier and the developer carrier tends to have uneven density. On the other hand, when the value of t / ε is less than 50 μm. If the size is large, the developer is more likely to be supplied to the non-image portion, and fogging is likely to occur in the formed image.

In the developing device according to a second aspect of the present invention, in order to solve the above-mentioned problem, the amount of the developer held on the surface of the developer carrier is regulated by a regulating member. When transported to the developing position facing the image carrier, at least the surface of the conductive substrate in the developer carrier has a rubber hardness of 10 to 70 degrees and an elongation of 4
It is made of 00 to 1200% of a conductive elastic material. The above rubber hardness and elongation are in accordance with JIS K6
It is a value measured according to 301.

According to a second aspect of the present invention, at least the surface of the conductive substrate in the developer carrier has a rubber hardness of 10 to 70 degrees and an elongation of 400 to 12 degrees.
When the developer held by the developer carrier is regulated by the regulating member as described above, the surface of the developer carrier deforms and is added to the developer when the developer is made of a conductive elastic material of 00%. The load is reduced, the generation of fine powder due to the cracking of the developer is suppressed, and the occurrence of density unevenness in an image formed by fusing the fine powder of the developer to the surface of the developer carrier is also reduced.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a developing device according to an embodiment of the present invention will be specifically described with reference to the accompanying drawings.

In this embodiment, as shown in FIG. 1, a photosensitive layer 1 is provided on the surface of a cylindrical conductive support 1a.
The surface of the image carrier 1 is charged by a charging device (not shown) using the image carrier 1 formed of the photosensitive drum 1 on which the surface b is formed. The image carrier 1 is irradiated with light from a device (not shown).
An electrostatic latent image corresponding to the image information is formed on the surface of the.

Here, in the developing device of this embodiment, as shown in FIGS. 1 and 2, a conductive base 11c having a conductive elastic layer 11b provided around a conductive rotating shaft 11a is provided. A developer carrier 11 having a dielectric layer 11d formed on the surface is used.

When the developer carrying member 11 is provided so as to face the image carrying member 1 with a predetermined distance Ds therebetween, as shown in FIG. A roller member 11e having a diameter slightly larger than the diameter of the developer carrier 11 is rotatably provided on both sides of the roller, and a distance Ds at a position where the developer carrier 11 and the image carrier 1 are opposed by the roller member 11e. Is 150 to 400
It is set to the range of μm.

The dielectric layer 11d provided on the developer carrier 11 has a thickness t of 50 μm or more and constitutes the dielectric layer 11d as shown by a solid portion in FIG. A material having a relative dielectric constant ε of 10 or less is used, and a value (t / ε) obtained by dividing the thickness t by the relative dielectric constant ε is set to be in a range of 10 to 50 μm. Note that various plastic materials, elastomer materials, rubber materials, and the like can be used as a material forming the dielectric layer 11d.

In this developing device, the main assembly 10 of the developing device provided with the developer carrier 11 is provided.
A developer (toner) 12 is accommodated in the
Is supplied to the developer carrier 11 side by rotating feed blades 13 and the supply roller 1 provided so that the developer 12 thus delivered is brought into contact with the developer carrier 11.
4 supplies the developer 12 to the surface of the developer carrier 11 and conveys the supplied developer 12 to the image carrier 1 by rotation of the developer carrier 11.

Further, while the developer 12 is being conveyed to the image carrier 1 by the developer carrier 11, the regulating member 15 is pressed against the surface of the developer carrier 11,
The regulating member 15 regulates the amount of the developer 12 conveyed to the developing area, and the developer 12 is frictionally charged.

Then, the amount of the conveyed toner is regulated by the regulating member 15 and the frictionally charged developer 12 is moved to the developing position opposed to the image carrier 1 by the developer carrier 11 at a required distance Ds. A DC power supply 16 a and an AC power supply 16 b are provided between the developer carrier 11 and the image carrier 1.
Then, a developing bias voltage in which an AC pulse voltage is superimposed on a DC voltage is applied to supply the developer held on the surface of the developer carrier 11 to the electrostatic latent image formed on the image carrier to develop the image. Is to be performed.

When the electrostatic latent image formed on the image carrier 1 is developed as described above, the edge effect at the edge portion of the electrostatic latent image formed on the image carrier 1 is suppressed, and There is no increase in image density alone at the edge portion, no deterioration in the faithful reproducibility of point or line images, no fogging in the formed image, Even when the distance Ds from the carrier 1 fluctuates, the density and the like of an image to be formed rarely fluctuate, and a good image having a constant image density can be obtained.

Further, in the developer carrier 11 described above,
Conductive elastic layer 1 provided around conductive rotating shaft 11a
The material constituting 1b has a rubber hardness of 10 to 70 degrees,
When an elongation of 400 to 1200% is used, the regulating member 15 is pressed against the surface of the developer carrier 11 as described above, and the developer 1 on the surface of the developer carrier 11 is pressed.
When regulating the amount of 2, the load applied to the developer 12 due to the deformation of the developer carrying member 11 is greatly reduced, and the developer 12 is less likely to be cracked by the pressure contact of the regulating member 11, so that the developing The occurrence of streak-like density unevenness in an image formed by fusing the fine powder of the agent 12 to the surface or the like of the developer carrier 11 is also suppressed.

Next, the distance Ds between the developer carrier 11 and the image carrier 1 is set in the range of 150 to 400 μm, and the thickness t of the developer carrier 11 is 50
μm or more, and its relative permittivity ε is 10 or less,
It will be clarified based on experiments that the above-described effects can be obtained when the dielectric layer 11d having a value of t / ε of 10 to 50 μm is provided.

In this experiment, when providing the dielectric layer 11d on the surface of the developer carrying member 11, the dielectric layer 11d
As a material constituting d, a styrene-based thermoplastic elastomer material having a relative permittivity ε of about 3 and a urethane material having a relative permittivity ε of about 8 are used.
μm, 50 μm, 100 μm, and 150 μm, and using a material having a relative dielectric constant ε of about 3, the above t /
In the case of using each developer carrier 11 having a value of ε of 0 μm, 17 μm, 33 μm, and 50 μm, and a material using a material having a relative dielectric constant of about 8, the value of t / ε is 0 μm,
Each developer carrier 1 of 6 μm, 12 μm, and 19 μm
1 was used.

Then, each developer carrier 11 is used by the above-mentioned roller member 11e using each developer carrier 11 described above.
The gap (developing gap) Ds between the image bearing member 1 and the image carrier 1 is changed, and the screen rulings are respectively determined under the developing conditions under which an image having an image density of 1.4 is obtained when a solid black image is formed. Is a high-resolution, low-density halftone image consisting of halftone dots having a screen angle of 300 lines, a screen angle of 0 °, and a black to white ratio (B / W ratio) of 25%. The density was measured, and the relationship between each image density and the developing gap Ds was determined. Here, each developer carrier 1 provided with a dielectric layer 11d having a relative dielectric constant ε of about 3
5 (A) shows the results obtained when using each of the developer carriers 11 provided with a dielectric layer 11d having a relative dielectric constant ε of about 8.
FIG. 5B shows the results in the case of using.

As a result, when the developing gap Ds is small, the value of t / ε in the dielectric layer 11d provided on the developer carrier 11 changes, so that the image density largely changes, and the developing gap Ds decreases. The image density became constant as the size increased.

Next, based on the results shown in FIGS. 5A and 5B, the distances (developing gaps) Ds between the developer carrier 11 and the image carrier 1 are set to 150 μm, 200 μm, 2 μm.
In the case where the distance Ds was set to 50 μm, 300 μm, and 350 μm, the relationship between the image density difference generated when the interval Ds fluctuated in the range of ± 100 μm and the value of t / ε was obtained, and the results are shown in FIG. .

As a result, when the dielectric layer 11d is provided on the surface of the developer carrying member 11, as the value of t / ε in the dielectric layer 11d increases, the developing gap Ds
Is smaller than 10 μm, the density of the formed image is greatly changed by the change of the developing gap Ds. It is preferable that the thickness be 10 μm or more. In particular, when the value of t / ε is 30 μm or more,
In the case where the developing gap Ds is as narrow as 150 μm, even if the developing gap Ds fluctuates, the density of the formed image is constant and an image having a stable density can be obtained.

Next, as shown in FIG. 7, the values of t / ε are 0 μm, 17 μm, 33 μm, 50 μm, and 66 μm.
Developer carrier 11 provided with respective dielectric layers 11d
And the difference (Vir-Vb) between the DC voltage Vb applied between the developer carrier 11 and the image carrier 1 from the DC power supply 16a and the surface potential Vir of the image carrier 1 is changed. An image was formed, and the relationship between the image density in the formed image and the value of (Vir-Vb) was examined. The result is shown in FIG.

As a result, in the developer carrier 11 provided with the dielectric layer 11d having the value of t / ε of 66 μm, the DC voltage Vb
(Vir-Vb) between the image potential and the surface potential Vir of the image carrier 1
Must be set to −600 V or less. Therefore, in order to obtain a sufficient density difference between the image portion and the non-image portion, the potential difference between the image portion and the non-image portion must be very large, and fog occurs in the non-image portion. It is very difficult to suppress the occurrence of the t / t in the dielectric layer 11 d provided on the surface of the developer carrier 11.
It was preferable to set the value of ε to 50 μm or less.

When the dielectric layer 11d is provided on the surface of the developer carrier 11 as described above,
When the value of t / ε in 1d is set to 10 to 50 μm, the dielectric layer 11 is formed using a material having a small relative dielectric constant ε.
When the thickness t of the dielectric layer 11d is reduced, the thickness t of the dielectric layer 11d is reduced.
Therefore, it is preferable to set the thickness t of the dielectric layer 11d to 50 μm or more because the density of an image formed greatly changes due to the variation in the thickness.

In providing the dielectric layer 11d on the surface of the developer carrying member 11, if the relative dielectric constant ε of the dielectric layer 11d is larger than 10, the dielectric layer 11d
d, the electric field acting between the developer carrier 11 and the image carrier 1 is not sufficiently controlled by the dielectric layer 11d, and the image carrier 1 and the developer carrier 1
The density in the formed image also changed even when the interval from 1 slightly changed.

Next, in the developer carrying member 11 in the developing device of the above-described embodiment, each developer carrying member 11 in which the kind of the conductive elastic layer 11b provided around the rotation shaft 11a is changed is used. An experiment was conducted in which the regulation member 15 was pressed against the surface of each of the developer carrying members 11 to perform regulation, and the material constituting the elastic layer 11b had a rubber hardness of 10%.
It is apparent that the use of the developer carrier 11 having an elongation of 400 to 1200% at a temperature of 70 to 70 degrees prevents the developer 12 from being cracked by the pressing of the regulating member 15.

Here, in this experiment, the developer 12
The toner manufactured as follows was used.

In producing the toner, 10 parts of a polyester resin (manufactured by Kao Corporation: Tufton NE-1110) is used.
0 parts by weight, 8 parts by weight of carbon black as a coloring agent (manufactured by Cabot: Mogul L), 3 parts by weight of a charge control agent (manufactured by Orient Chemical: Bontron S-34), and a release agent (Sanyo Chemical Industries, Ltd.) Manufactured by Viscol TS-200) in a ratio of 2.5 parts by weight, mixed with a Henschel mixer at a rotation speed of 2800 rpm for 3 minutes, kneaded using a twin-screw kneading extruder, and allowed to cool. After coarse pulverization and further fine pulverization by an ultrasonic jet pulverizer (manufactured by Nippon Pneumatic), classification was performed with an elbow jet (manufactured by Matsuzaka Trading) to obtain toner particles. Then, hydrophobic silica (Cabotil TS-500, manufactured by Cabot Corporation) was added to the toner particles at a ratio of 0.8% by weight, and these particles were rotated at 2 rpm by a Henschel mixer.
The mixture was mixed at 500 rpm for 90 seconds to produce a negatively chargeable toner.

(Experimental Example 1) In this experimental example 1, the current
A conductive elastic layer around the rotation axis 11a of the image material carrier 11
Use a styrene elastomer to provide 11b
As shown in Table 1 below, the rubber hardness was 44
Degree, elongation 710%, volume resistivity 10 ⁶Ω · cm
Provided on the elastic layer 11b.
In addition, using a material having a relative dielectric constant of about 3 and a film thickness of 100 μm
Was formed.

(Experimental Example 2) In Experimental Example 2, when a conductive elastic layer 11b is provided around a rotating shaft 11a of a developer carrier 11, a styrene elastomer is used as shown in Table 1 below. Is provided with an elastic layer 11b having a rubber hardness of 77 degrees, an elongation of 850%, and a volume resistivity of 10 ⁵ Ω · cm. On this elastic layer 11b, a material having a relative dielectric constant ε of about 3 is formed. A dielectric layer 11d having a thickness of 100 μm was provided.

(Experimental Example 3) In Experimental Example 3, when the conductive elastic layer 11b is provided around the rotation shaft 11a of the developer carrier 11, urethane rubber is used as shown in Table 1 below. , Rubber hardness 68 degrees, elongation 980
%, Elastic layer 1 having a volume resistivity of 10 ⁵ Ω · cm
1b, a dielectric layer 1 having a thickness of 100 μm using a material having a relative dielectric constant of about 3 is formed on the elastic layer 11b.
1d was provided.

(Experimental Example 4) In Experimental Example 4, when the conductive elastic layer 11b is provided around the rotating shaft 11a of the developer carrier 11, silicon rubber is used as shown in Table 1 below. , Rubber hardness 50 degrees, elongation 290
%, Elastic layer 1 with volume resistivity value of 10 ⁶ Ω · cm
1b, a dielectric layer 1 having a thickness of 100 μm using a material having a relative dielectric constant of about 3 is formed on the elastic layer 11b.
1d was provided.

Next, a printing durability test of 10,000 sheets was performed using the developer carrying member 11 shown in the above-mentioned Experimental Examples 1 to 4, and evaluation of density unevenness in the formed image was performed. Table 1 is also shown. In evaluating the density unevenness of the image after the 10,000-sheet printing test, a case where a good image was obtained without the density unevenness was indicated by “○”, and a case where streak-like density unevenness occurred was indicated by “×”. .

[0050]

[Table 1]

As a result, in the developer carrier 11, the conductive elastic layer 11 is formed around the conductive rotating shaft 11a.
In the case of Experimental Examples 1 and 3 provided with the elastic layer 11b having a rubber hardness of 10 to 70 degrees and an elongation in the range of 400 to 1200%, the developer carrier 11 is provided as described above. When the amount of the developer 12 on the surface is regulated by the regulating member 15, it is suppressed that the developer 12 is broken and the fine powder of the developer 12 is fused to the surface of the developer carrier 11 or the like. No density unevenness occurred in the resulting image.

On the other hand, in the experimental example 2 in which the hard elastic layer 11b having a rubber hardness of 77 degrees was provided, the elongation was 290%.
In the case of Experimental Example 4 provided with a small amount of the elastic layer 11b, when the amount of the developer 12 on the surface of the developer carrier 11 is regulated by the regulating member 15, the developer 12 is cracked to generate fine powder, The fine powder fused to the surface of the developer carrying member 11 and the like, and streaky density unevenness occurred in the formed image.

[0053]

As described above in detail, in the developing device according to the first aspect of the present invention, the developer provided so as to face the image bearing member on which the electrostatic latent image is formed at a required distance. When the developer is held on the surface of the carrier and the developer is transported to the developing position facing the image carrier by the developer carrier and the development is performed, the distance between the developer carrier and the image carrier is set. Is in the range of 150 to 400 μm, and the thickness t is 50 μm or more, the relative dielectric constant ε is 10 or less, and the thickness t
Is divided by the relative dielectric constant [epsilon] to provide a dielectric layer having a value (t / [epsilon]) in the range of 10 to 50 [mu] m, and the electric field acting between the developer carrier and the image carrier by the dielectric layer is provided. Is now properly controlled.

As a result, when the electrostatic latent image formed on the image carrier is developed using the developing device of the present invention, the edge effect at the edge portion of the electrostatic latent image formed on the image carrier is suppressed, In the case where only the image density at the edge portion of the formed image is not increased, the fidelity reproducibility of the point or line image is not deteriorated, and when the distance between the developer carrier and the image carrier fluctuates. Also, it is suppressed that the density or the like of the formed image fluctuates greatly,
A good image having a constant image density can be obtained.

Further, as set forth in claim 2 of the present invention,
In the above-described developing device, at least a surface portion of the conductive substrate in the developer carrier has a rubber hardness of 10 to 70 degrees,
When composed of a conductive material having an elongation of 400 to 1200%,
When a regulating member is pressed against the surface of the developer carrier to regulate the amount of the developer on the surface of the developer carrier, the load applied to the developer due to deformation of the developer carrier is greatly increased. As a result, the cracking of the developer is suppressed, and the fine powder of the developer is fused to the surface of the developer carrying member to prevent the occurrence of streak-like density unevenness in an image formed. Became.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a developing device according to an embodiment of the present invention.

FIG. 2 is a partial explanatory view showing a state in which a developer carrying member is provided so as to face an image carrying member at a predetermined interval in the developing device according to the embodiment.

FIG. 3 is an explanatory plan view showing a state in which a developer carrier is provided so as to be opposed to an image carrier at a required interval in the developing device according to the embodiment;

FIG. 4 is a view showing a range of a thickness t of a dielectric layer provided on a surface of a developer carrier and a relative dielectric constant ε in the developing device according to the embodiment.

FIG. 5 shows an experimental example of the present invention in which the relative dielectric constant ε is about 3;
A halftone image was developed using each developer carrier having a dielectric layer formed of the above material and each developer carrier having a dielectric layer formed of a material having a relative dielectric constant of about 8. FIG. 7 is a diagram showing a relationship between image density and development gap Ds in the case.

FIG. 6 shows the thickness t of the dielectric layer in the experimental example of the present invention.
Is divided by the relative dielectric constant ε (t / ε), and when a halftone image is developed using each developer carrier, the developing gap Ds varies within a range of ± 100 μm. FIG. 5 is a diagram showing a relationship between an image density difference generated in the above and the value of t / ε.

FIG. 7 shows a relationship between a developer carrier and an image carrier when development is performed using each developer carrier provided with dielectric layers having different values of t / ε in an experimental example of the present invention. DC bias voltage Vb to be applied to the surface and the surface potential V of the image carrier
FIG. 6 is a diagram illustrating a relationship between a difference (Vir−Vb) from ir and an image density in a formed image.

[Explanation of symbols]

 Reference Signs List 1 image carrier 11 developer carrier 11c conductive substrate 11d dielectric layer 12 developer (toner) 15 regulating member Ds distance between developer carrier and image carrier t thickness of dielectric layer ε dielectric layer Dielectric constant of

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoichi Fujieda 2-3-13 Azuchicho, Chuo-ku, Osaka City Inside Osaka International Building Minolta Co., Ltd. (72) Inventor Ryuji Inoue 2-3-3 Azuchicho, Chuo-ku, Osaka-shi No. 13 Osaka International Building Minolta Co., Ltd.

Claims (2)

[Claims] An image bearing member on which an electrostatic latent image is to be formed is provided with a developer on a surface of the developer bearing member provided at a predetermined distance from the image bearing member. In a developing device which transports the developer to a developing position opposed to the image carrier, and sets the distance between the developer carrier and the image carrier in the range of 150 to 400 μm, As the carrier, the thickness t is 50 μm or more and the relative dielectric constant ε is 10 or less on the surface of the conductive substrate, and the value obtained by dividing the above thickness t by the relative dielectric constant ε (t / ε) is 10 to 10.
A developing device comprising a dielectric layer having a thickness of 50 μm. 2. The developing device according to claim 1, wherein
The amount of the developer held on the surface of the developer carrier is regulated by a regulating member to be conveyed to a developing position facing the image carrier, and at least the surface of the conductive substrate in the developer carrier is covered with rubber. A developing device comprising a conductive elastic material having a hardness of 10 to 70 degrees and an elongation of 400 to 1200%.