JPH06110310A - One-component developing device and image forming device using the same - Google Patents

Abstract

PURPOSE:To prevent the shortage of toner and the generation of fog even in the case of prolonging a replacing period of one-component developer, as to a one-component developing device for electrostatically charging the one- component developer, carrying it to am image carrier and developing a latent image formed on the image carrier and an image forming device using the device. CONSTITUTION:The device is provided with an endless type developer carrier 50 which is brought into press-contact with the image carrier on which the electrostatic latent image is formed and carrys the one-component developer, and a toner controlling means which is brought into press-contact with the developer carrier 50 and controls the layer thickness of the one-component developer on the developer carrier 50. In the one-component developing device in which the developer carrier 50 is constituted of a porous elastic body and a developing bias voltage is impressed on the developer carrier 50, the one- component developer has a toner 20 and resin powder 21 which is electrostatically charged to a polarity reverse to that of the toner 20.

Description

Detailed Description of the Invention

(Table of Contents) Industrial Application Field of the Prior Art (FIG. 10) Problem to be Solved by the Invention Means for Solving the Problem (FIG. 1) Action Example (a) Description of Image Forming Apparatus (FIG. 2) To FIG. 4) (b) Description of developing device (FIGS. 5 to 9) (c) Description of another embodiment Effect of the invention

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a one-component developing device which charges a one-component developer and conveys it to an image carrier to develop a latent image on the image carrier, and an image forming apparatus using the same. .

In an image forming apparatus such as a copying machine, a printer or a facsimile machine, an electrophotographic apparatus or the like is used in order to record plain paper. The principle is that a photosensitive drum is charged, imagewise exposed and electrostatically charged. Form a latent image, develop with a developing device,
The process of transferring the toner image to the sheet and obtaining the toner image on the sheet is taken.

In such an image forming apparatus, a developing device using a one-component developer which can be inexpensively constructed and is easy to maintain is widely used, and one using a non-magnetic one-component toner is particularly used. Attention has been paid.

In the developing device using the non-magnetic one-component toner, it is desired that the toner is stably conveyed for a long period of time and the background portion is less contaminated.

[0006]

2. Description of the Related Art FIG. 10 is an explanatory diagram of a conventional technique. Figure 1
As shown in FIG. 0 (A), the developing device 5 ′ is filled with the one-component non-magnetic developer (toner) 20, and the one-component developer is conveyed by the developing roller 50 ′ while the blade 5
The layer thickness is regulated by 1 ', the developing roller 50' is brought into contact with the photosensitive drum 40, and the toner conveyed by the developing roller 50 'is electrically moved to the electrostatic latent image on the photosensitive drum 40 to develop the toner. To do.

The developing roller 50 'is a photosensitive drum 40.
Therefore, it is necessary to have elasticity, and to apply a developing bias, it is necessary to have a certain degree of conductivity.

As the developing roller 50 ',
As disclosed in Japanese Unexamined Patent Publication No. 6846, it is known that the toner is fitted into the concave portion and conveyed by providing the surface with unevenness of about 1/3 to 1/5 of the toner particle diameter.

However, in this method, when the temperature and humidity are high (for example, about 32 ° C. and about 80%), the friction coefficient of the toner increases, and the toner does not enter between the blade 51 'and the developing roller 50'. The toner is repelled by 51 ', and the toner on the developing roller 50' runs short.

To solve this problem, the present applicant has filed Japanese Patent Application No. 1-110322 (filed on April 28, 1991).
In FIG. 10B, as shown in FIG.
It has been proposed that a porous elastic body is used for 0 ', and the toner 20 is held in the pores of the porous elastic body, so that the toner can be stably transported even with environmental changes.

If the pore diameter of this porous elastic body is too large, the toner adheres to the background portion due to the developing electric field. Therefore, it is appropriate that the average particle diameter of the toner is about 1/2 to 2 times.

[0012]

However, the prior art has the following problems. According to the conventional proposal, if the life of the developing device is shortened and frequent replacement is performed, very stable development is possible, but if the replacement cycle is lengthened and the printer is used for a long period of time, printing with a high printing rate is possible. As a result, the print density was lowered or the print density was changed depending on the environment.

This is because when the pore diameter is the above-mentioned, the toner is clogged in the pores or the toner is fixed on the surface due to long-term use, and the amount of toner that the developing roller can supply decreases. there were.

In order to solve this, it is conceivable to make the pore diameter of the developing roller larger than in the conventional proposal.
By doing so, as shown in the conventional proposal, since the pores of the developing roller are large and a large amount of toner is stored,
The adhesion of the toner to the developing roller becomes weak, and the so-called fog occurs, which stains the background of the print.

Therefore, it is an object of the present invention to provide a one-component developing device capable of preventing toner shortage and fogging even if the replacement cycle is lengthened, and an image forming apparatus using the one-component developing device.

[0016]

FIG. 1 shows the principle of the present invention. According to claim 1 of the present invention, an endless developer carrier 50 that conveys a one-component developer by being pressed against the image carrier 40 on which an electrostatic latent image is formed, and the developer carrier 50. The developer carrying member 5 has a toner regulating means 51 which regulates the layer thickness of the one-component developer of the developer carrying body 50 by pressing.
In the one-component developing device in which 0 is composed of a porous elastic body and a developing bias voltage is applied to the developer carrying member 50, the one-component developer is the toner 20 and the toner 20.
And a resin powder 21 that is charged to the opposite polarity.

According to claim 2 of the present invention, in claim 1,
A voltage is applied to the toner regulating means 51 to forcibly charge the developer. Claim 3 of the present invention
Is characterized in that the pore diameter of the porous elastic body of the developer carrying member 50 is set to 2.5 times to 4 times the average particle diameter of the toner 20.

According to a fourth aspect of the present invention, in the first, second, or third aspect, the volume resistivity of the porous elastic body of the developer carrying member 50 is set to 10 4 to 10 10 ohm cm. It is characterized by

According to a fifth aspect of the present invention, an endless image carrier 40, latent image forming portions 41 and 7 for forming an electrostatic latent image on the image carrier 40, and an electrostatic latent image are formed. Image carrier 40
One-component development in which the toner control means 51 is pressed against the endless developer carrier 50 that conveys the one-component developer by pressing the toner control means 51 to regulate the layer thickness of the one-component developer of the developer carrier 50. In the image forming apparatus including the device 5, the developer carrying member 50 is formed of a porous elastic body, and the developing bias voltage is applied to the developer carrying member 50, the one-component developer is the toner 20. And a resin powder 21 charged to the opposite polarity to the toner 20.

According to a sixth aspect of the present invention, in the fifth aspect,
Transfer means 4 for transferring the developed image of the image carrier 40 onto a medium.
2 is provided. A seventh aspect of the present invention is characterized in that, in the fifth or sixth aspect, a voltage is applied to the toner regulating means 51 to forcibly charge the developer.

According to claim 8 of the present invention, in claim 5 or 6 or 7, the pore diameter of the porous elastic body of the developer carrying member 50 is 2.5 times to 4 times the average particle diameter of the toner 20. It is characterized in that the number of times is not more than twice.

According to a ninth aspect of the present invention, in the fifth, sixth, seventh or eighth aspect, the volume resistivity of the porous elastic body of the developer carrying member 50 is 10 4 to 10 10 ohm c.
It is characterized in that it is m.

[0023]

According to claims 1 and 5 of the present invention, when the toner 20 is mixed with the resin powder 21 charged to the opposite polarity to the toner 20 as the one-component developer, as shown in FIG. Since the positively charged resin powder 21 is adsorbed on the toner 20 charged to the inside and enters the pores of the developer carrier 50, the electrostatic attraction force between the resin powder 21 and the bias voltage of the developer carrier 50 causes electrostatic attraction. The adhesive force of the toner 20 to the developer carrying member 50 works, and the attracting force between the toners 20 is generated by the resin powder 21, which makes it difficult for the toner 20 to pop out due to the developing electric field.

For this reason, even if the developer carrying member 50 having a small pore size and a large pore diameter is used, it is possible to prevent the printing background portion from being soiled and to perform stable development for a long period of time. According to claims 2 and 7 of the present invention, if the toner is forcibly charged from the blade 51, the toner can be stably charged without affecting environmental changes. However, if the toner is unipolar, some of the toner has a reverse polarity. It is charged to and adheres to the background part.

Here, when the resin powder 21 is mixed, the resin powder 2
Since 1 is charged to the opposite polarity, the toner 20 itself is always charged to the one polarity, and the effect of forced charging can be further enhanced.

In Claims 3 and 8 of the present invention, if the pore diameter of the porous elastic body of the developer carrying member 50 is smaller than 2.5 times the average particle diameter of the toner 20, clogging occurs and 4 times. When it exceeds, the small electrostatic attraction force of the resin powder 21 causes
Since it is impossible to prevent the toner 20 from popping out due to the developing electric field, the pore diameter is set to 2.5 to 4 times.

In Claims 4 and 9 of the present invention, if the volume resistivity of the porous elastic body of the developer carrying member 50 is smaller than 10 4 ohm cm, the blade 51 will be burned by the application of the charging bias. On the contrary, if it is larger than 10 10 ohm cm, the surface potential becomes high due to charge-up and fog occurs. Therefore, the volume resistivity is changed from 10 4 ohm cm to 10 10 ohm cm. did.

According to a sixth aspect of the present invention, the image carrier 40 includes:
Since the resin powder 21 is attracted to the toner 20 to form a toner image, the resin powder 21 is interposed between the toner 20 and the image carrier 40, and the Vonderworth force of the toner 20 on the image carrier 40. The suction force due to (mechanical suction force) decreases,
The transfer operation by the transfer unit 42 can be improved. is there.

[0029]

【Example】

(a) Description of Image Forming Apparatus FIG. 2 is a sectional view of an image forming apparatus of one embodiment of the present invention, FIG. 3 is a configuration diagram of a process cartridge of one embodiment of the present invention, and FIG. 4 is an image forming apparatus of one embodiment of the present invention. FIG. 3 is an explanatory diagram showing a printer as an image forming apparatus.

In the apparatus sectional view of FIG. 2, reference numeral 2 is a process cartridge, which is provided in the lower portion of the apparatus and is provided in the upper portion of a sheet cassette 12 for accommodating sheets, which will be described later with reference to FIG. A path is for conveying the paper from the paper cassette 12 to the upper stacker 14 by a U-shaped path, 6 is a heat fixing device, and a heat roller 6
No. 0 and a backup roller 61 are provided to fix the toner image on the sheet, and a cleaning roller 62 for removing the toner adhering to the heat roller 60 is provided.

Reference numeral 7 denotes an optical unit, which scans the light of a semiconductor laser driven by image information with a polygon mirror and passes over the developing device 5 as shown by a dotted arrow in the figure, and the photosensitive drum of the process cartridge 2. 40 is a unit for irradiating the sheet, and 8 is a sheet separating unit, which has a discharge electrode, discharges electric charges having a polarity opposite to the sheet back surface potential on the back side of the sheet after transfer, and neutralizes the back side of the sheet to remove the sheet. It is separated from the photosensitive drum 40.

Reference numeral 30 is a pickup roller for picking up the paper in the paper cassette 12, 31 is a registration roller for conveying the paper picked up by the pickup roller 30 with the leading ends aligned, and 32 is a manual feed guide. , Which is opened to the right side of the drawing, guides the manually fed paper to the manual feed roller 33, and 33 is a manual feed roller which conveys the paper inserted from the manual feed guide 32 to the process cartridge 2.

Reference numeral 34 is a cover shaft, and the front cover 1
A discharge roller 36 serves as a rotation shaft of 0, and is for discharging the paper having passed through the thermal fixing device 6 to the stacker 14.

In the configuration diagram of the process cartridge of FIG. 3, the process cartridge 2 comprises a drum cartridge 4 and a developing device 5. The developing device 5 is attached to the drum cartridge 4 by a pin, and by removing the pin, , Separated from the drum cartridge 4.

Explaining the structure of the drum cartridge 4, reference numeral 40 denotes a photosensitive drum, which is formed by forming an organic photosensitive material layer (OPC or the like) on the surface of a cylindrical substrate made of aluminum or the like, and rotates counterclockwise as shown in the drawing. What is done, 41
Is a charging roller, which is composed of a conductive rotary brush charger in which conductive rayon fibers are woven into a core metal and is planted, and uniformly charges the photosensitive drum 40 to about -650V.

A transfer roller 42 is provided on the drum cartridge 4 and is made of a conductive porous sponge material, for example, a porous polyurethane foam sponge material.
The photosensitive drum 40 is pressed against the photosensitive drum 40 and a transfer voltage is applied to transfer the toner image on the photosensitive drum 40 onto a sheet. Reference numeral 43 denotes a waste toner box (cleaner).
The residual toner of 0 is scraped by the scraping blade 44 and accommodated therein, and 45 is a grip, and the drum cartridge 4
And a roller cover 46 for protecting the transfer roller 42.

Next, the structure of the developing device 5 will be described.
Is a developing roller, which is formed by inserting a metal shaft into a conductive elastic roller, preferably a conductive porous sponge material, for example, a conductive porous polyurethane sponge material, and rotates clockwise as shown in the figure. Then, a one-component developer, which will be described later with reference to FIG. 5, is held by its surface holding force and conveyed to the photosensitive drum 40. The one-component developer is pressed against the photosensitive drum 40 so as to have a predetermined nip width, and- A developing bias voltage of 300 V is applied to the metal shaft.

Reference numeral 51 denotes a layer thickness regulating blade portion, which regulates the layer thickness of the toner adhered to the developing roller 50 to a predetermined thickness, and is constituted by a stainless plate having a thickness of 0.1 mm. Is pressed to, for example, negative -400V
When the toner layer thickness is regulated, a negative charge is injected into the toner, and the toner is forcibly charged negatively together with frictional charging, so that the toner is stably charged even at high humidity and high temperature.

Reference numeral 52 denotes a reset roller, which is made of a conductive sponge material, is in contact with the developing roller 50, is rotated in the same direction as the developing roller 50, and is applied with a bias voltage of -400 V. To scrape off the toner from the developing roller 50 and to supply the toner to the developing roller 50 at the left side of the drawing.

Reference numerals 53 and 54 denote paddle rollers, which rotate to agitate the one-component developer in the developing device 5 to charge it and convey it toward the reset roller 52.
Reference numeral 5 denotes a cassette housing unit which houses the toner cassette 56.

Reference numeral 56 denotes a toner cassette (toner replenishing portion), which stores the one-component developer and is detachably set in the cassette storing portion 55. Reference numeral 57 denotes a toner supply lever, which is provided in the toner cassette 56. Which is rotated and supplies the toner in the toner cassette 56 into the developing device 5. Reference numeral 58 is a grip, which is provided on the toner cassette 56 and is used for holding the toner cassette 56 by hand. Is a paper guide rib which guides the paper between the photosensitive drum 40 and the transfer roller 42 together with the roller cover 46.

The operation of this printer will be described with reference to FIGS. 2 to 3. The paper in the paper cassette 12 is picked up by the pickup roller 30, abutted against the registration roller 31, and the leading end of the registration roller 31 is aligned.
The character transfer path 3 is transferred in the direction of the photosensitive drum 40.

On the other hand, when the paper is picked up by the registration roller 31, the image exposure of the photosensitive drum 40 by the optical unit 7 is started, and the potential of the image exposure portion of the photosensitive drum 40 charged to −650 V by the charging roller 41. Becomes zero, and an electrostatic latent image corresponding to the image is formed.

In the developing device 5, the developing roller 50 is -40.
Since the bias voltage of 0V is applied, the negatively charged toner adheres to the image-exposed portion of the photosensitive drum 40 where the potential is zero, and a toner image is formed.

The toner image on the photosensitive drum 40 is transferred onto the sheet conveyed by the registration roller 31 onto the transfer roller 42.
Is transferred by electrostatic force and pressure by the photosensitive drum 4
The paper electrostatically attracted to 0 is separated from the photosensitive drum 40 by removing the potential on the back surface of the paper by the electric charge supplied to the paper separating unit 8.

The separated sheet is sent to the heat fixing device 6, the toner image on the sheet is heat fixed by the heat roller 60 of the heat fixing device 6, and is discharged to the stacker 14 by the discharge roller 36.

Similarly, the paper inserted by tilting the manual feed guide 32 is inserted into the photosensitive drum 40 by the manual feed roller 33.
The toner image on the photosensitive drum 40 is conveyed by the transfer roller 42 by the electrostatic force and pressure, and the sheet electrostatically attracted to the photosensitive drum 40 is charged by the sheet separating section 8 to the photosensitive drum. The toner image on the paper is thermally fixed by the heat roller 60 of the heat fixer 6 and discharged to the stacker 14 by the discharge roller 36.

4, the front cover 10 is opened to the front surface on the right side of the figure around the cover shaft 34, and the front cover 10 has a manual feed guide 32 and a manual feed roller. 33 and the paper separating section 8
The heat fixing device 6 and the discharge (drive) roller 36a on the upper side of the discharge rollers 36 are provided.

Further, the upper cover 11 is opened to the upper part of the apparatus around the shaft (not shown) in the upper part of the drawing, and the lower discharge (pinch) roller 36b of the discharge rollers 36 is provided.

Therefore, when the front cover 10 is opened, the U-shaped conveying path 3 from the registration roller 31 to the discharge roller 36 is opened, which is convenient for removing jammed paper. At this time, since the transfer roller 42 is provided on the process cartridge 2 side, the portion of the photosensitive drum 40 is not opened, but the transfer roller 42 has a deviation (parallelism, position) from the photosensitive drum 40. Since the transfer operation cannot be performed well, it is provided on the process cartridge 2 side. Even if this portion is not opened, there is no problem in removing the jammed paper.

Similarly, the reason why the entire heat fixing device 6 is provided on the front cover 10 is that when the heat fixing device 6 is divided so that the conveying path can be opened, a part of the heat fixing device 6 is placed on the process cartridge 2. This is because it has to be installed in the process cartridge 2, which makes it inconvenient to take out the process cartridge 2. Even if this portion is not opened, there is no problem in removing the jammed paper.

In opening the cover, as shown in FIG. 2, the front cover 10 is opened so that the upper cover 11 is not opened unless the front cover 10 is opened.
Is disposed on the upper cover 11 at the discharging portion.

Therefore, by opening the front cover 10,
When the upper cover 11 is opened, as shown in FIG.
The toner cassette 56 can be easily taken out and attached while the process cartridge 2 is installed from the front side of the apparatus with the upper part of the apparatus and a part of the front surface opened, and the toner cassette 5
Only 6 can be exchanged.

Since the front cover 10 opens the front side of the apparatus and the upper cover 11 opens the upper section of the apparatus, the process cartridge 2 can be easily taken out and attached, and even if the process cartridge 2 is large, replacement is easy. .

Therefore, the process cartridge 2 can be made large, and the developing device 5 in the process cartridge 2 can be made large, so that the amount of developer contained can be increased and the replacement cycle can be greatly extended.

Also, by replacing only the toner cassette 56,
Since the developer can be replenished, the exchange period can be further extended. Further, the discharge roller 36 is separated and the cover 1
Since 0 and 11 are opened, the entire U-shaped transport path 3 can be opened and the jammed paper can be taken out more easily.

(B) Description of Developing Device FIG. 5 is an explanatory view of a developing agent according to an embodiment of the present invention, FIG. 6 is an operation explanatory view of an embodiment of the present invention, and FIG. 7 is a comparative example explanatory view of the present invention.
8 and 9 are characteristic diagrams (No. 1) and (No. 2) of one embodiment of the present invention.

As shown in FIG. 5, the one-component developer is positively charged when the non-magnetic one-component toner in which hydrophobic silica is externally added to the polyester toner 20 having an average particle diameter of 10 microns is stirred together with the toner. A melamine resin powder 21 having a particle size of 0.3 micron was mixed at 0.5% by weight and used.

First, the pore diameter of the developing roller will be described with reference to FIGS. As the one-component developer, polyester toner 20 having an average particle diameter of 10 microns and hydrophobic silica externally added are used, and a developing roller 50 made of porous polyurethane of polycarbonate polyurethane is used. 10 micron, 20 micron, 25
Using 50,000, 40, and 50 microns, continuous printing of 30,000 sheets was performed in the apparatus shown in FIG.

Then, 3 in the developing roller of each pore diameter
In printing 10,000 sheets, the density at the rear edge of the black solid page printed in the initial stage was set to 1 and the density at the rear edge of the black solid page of the 30,000th sheet was examined. The results shown in Fig. 8 were obtained. It was

It can be seen from FIG. 8 that the smaller the pore diameter, the lower the print density due to continuous printing compared to the initial stage, and that the pore diameter is twice the average particle diameter of the toner 20 (20 microns) or less. Then, the print density will be reduced due to long-term use.

Examination of a porous body having the average particle diameter of the toner 20 equal to or less than twice the average particle diameter (20 microns) is shown in FIG.
As shown in FIG. 5, the toner is clogged in the pores of the porous body due to long-term use. As a result, even though the toner 20 is contained in the pores, the print density due to the insufficient supply of the toner is caused. Has occurred, only the toner adhering to the surface contributes to printing, and printing with a high printing rate becomes thin.

Therefore, it has been found that the pore diameter should be twice the average particle diameter of the toner 20 (20 microns) or more, but if it is simply increased, fog will occur. Explaining this, first, as a comparative example, a polyester-based toner 20 having an average particle diameter of 10 μm, which is a conventional one-component developer, with externally added hydrophobic silica is used, and a porous polyurethane of polycarbonate-based polyurethane is used. The developing roller 50 composed of
When printing with a print background portion was performed using five types of 0 micron, 25 micron, 40 micron, and 50 micron, the results shown by the dotted line in FIG. 9 were obtained.

According to this, it was found that the larger the pore diameter, the larger the fog on the printed background portion. As a cause for this, as the pore diameter increases, the mechanical restraining force of the pores of the toner 20 decreases, as shown in FIG. Is considered to be attached.

Therefore, in this embodiment, as a one-component developer, a polyester magnetic toner 20 having an average particle diameter of 10 microns and a non-magnetic one-component toner externally added with hydrophobic silica are positively charged when stirred together with the toner. The melamine resin powder 21 having a particle size of 0.3 micron is used in an amount of 0.1% by weight.
Using a mixture of 5%, a developing roller 50 composed of a porous polyurethane of polycarbonate type polyurethane was used as in the comparative example, and a developing roller 50 having pore diameters of 10 μm, 20 μm, 25 μm, 40 μm and 50 μm was used.
I used one to print with a print background,
The results shown by the solid line in FIG. 9 were obtained.

As a result, the fog on the printed background does not increase until the pore diameter is 4 times (40 microns) the average particle diameter of the toner 20. This means that the toner 20 is electrostatically attracted to the developing roller 50 by the positively charged resin powder 21 in the pores of the developing roller 50 as shown in FIG. It is considered that the resin powder 21 is sucked, receives a restraining force, and becomes difficult to jump out of the pores with respect to a weak external electric field, and does not adhere to the printing background portion.

On the contrary, when the negatively charged toner 20 was mixed with the negatively charged fluorine resin, fog was generated even if the pore diameter was small. In order to investigate the cause of this fog, the charge polarity of the toner attached to the photosensitive drum 40 was examined, and it was found that the toner 20 was positively charged on the contrary.

From these results, it was revealed that only the resin powder 21 having the positive charging characteristic can reduce the fog with respect to the negatively charging toner 20. This resin powder 2
In addition to the melamine resin described above, 0.5 micron acrylic resin or styrene-acrylic resin has the same effect.

In the developer mixed with the resin powder 21, the charge is injected from the blade 51 and the toner 20 is negatively charged in the forced charging by the blade 51 shown in FIG. However, since the positively charged resin powder 21 is positively charged, all the toner 21 is negatively charged, which contributes to the prevention of fog.

Here, regarding the pore diameter of the developing roller 50, as shown in FIG. 8, the average particle diameter of the toner 20 is 2.
5 times or more is required, and from the viewpoint of fogging prevention, FIG.
As shown in, the optimum range is not more than 4 times.

Further, considering the volume resistivity of the porous body of the developing roller 50, it has been confirmed that the range of 10 4 ohm cm to 10 10 ohm cm is optimum.
That is, in the developing roller 50 whose volume resistivity is smaller than 10 4 ohm cm, the bias voltage of the blade 51 (−
The application of 400 V) caused partial burnout, resulting in large black dots in the printing.

On the other hand, with the developing roller 50 having a volume resistivity higher than 10 to the 10th power ohm cm, the printing density gradually increased after continuous printing, and finally the fog became severe. This is because when the surface potential of the developing roller 50 was measured, the surface potential gradually increased and became close to the surface potential of the photosensitive drum 40, and the cause was charge-up.

Further, it has been found that the developer containing the resin powder 21 can perform the transfer operation well. That is, when the toner 20 is only the toner 20, when the toner 20 adheres to the photosensitive drum 40 by an electrostatic force, the Von der Waals force acts due to the close contact between the toner 20 and the photosensitive drum 40, and the toner 20 also mechanically adheres to it, which makes transfer difficult.

On the other hand, when the resin powder 21 is mixed, when the toner 20 adheres to the photosensitive drum 40 by the electrostatic force, the resin powder 21 is formed between the photosensitive drum 40 and the toner 20.
Is sandwiched, the Von der Waals force due to the close contact between the toner 20 and the photosensitive drum 40 is reduced, and transfer is facilitated.

(C) Description of Other Embodiments In addition to the above embodiments, the present invention can be modified as follows. Although the example in which the plus resin powder is added to the minus toner has been described, the minus resin powder may be added to the plus toner.

Although the polyurethane sponge has been described as an example of the porous body of the developing roller 50, other porous elastic bodies such as urethane sponge and silicon sponge can be used.

Although the image forming apparatus has been described as a printer,
It may be another image forming apparatus such as a copying machine or a facsimile. The photosensitive member is not limited to the drum shape, and may have other endless shapes such as an endless belt shape, or may be a dielectric material as in the electrostatic recording method.

The present invention has been described above with reference to the embodiments.
Various modifications are possible within the scope of the invention, and these modifications are not excluded from the scope of the invention.

[0079]

As described above, according to the present invention,
It has the following effects. As a one-component developer, a mixture of toner and resin powder of opposite polarity was used, so that a porous body having a large pore size can be used for the developing roller, clogging of the toner is eliminated, and long-term use is possible. It is possible to prevent a decrease in print density.

Further, even if a porous body having a large pore diameter is used for the developing roller, fog is reduced and the development can be stably carried out.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a sectional view of an image forming apparatus according to an embodiment of the present invention.

FIG. 3 is a configuration diagram of a process cartridge according to an embodiment of the present invention.

FIG. 4 is an explanatory diagram of an image forming apparatus according to an embodiment of the present invention.

FIG. 5 is an explanatory diagram of a developing agent according to an exemplary embodiment of the present invention.

FIG. 6 is a diagram illustrating a developing operation according to an embodiment of the present invention.

FIG. 7 is an explanatory diagram of a comparative example of the present invention.

FIG. 8 is a characteristic diagram (1) of an example of the present invention.

FIG. 9 is a characteristic diagram (part 2) of the embodiment of the present invention.

FIG. 10 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

 40 photosensitive drum 50 developing roller 51 blade 20 toner 21 resin powder

Claims (9)

[Claims] 1. An image carrier (40) having an electrostatic latent image formed thereon.
And a one-component developer of the developer carrying body (50), which is brought into pressure contact with the developer carrying body (50) having an endless shape and which conveys the one-component developer, and the developer carrying body (50). And a toner regulating means (51) for regulating the layer thickness of the developer carrier, the developer carrier (50) is made of a porous elastic body, and a developing bias voltage is applied to the developer carrier (50). In the one-component developing device, the one-component developer includes a toner (20) and the toner (2).
0) and a resin powder (21) charged to the opposite polarity, a one-component developing device. 2. The one-component developing device according to claim 1, wherein a voltage is applied to the toner regulating means (51) to forcibly charge the developer. 3. The pore size of the porous elastic body of the developer carrying member (50) is 2.5 times the average particle size of the toner (20).
3. The amount is set to 2 to 4 times or less.
One-component developing device. 4. The volume resistivity of the porous elastic body of the developer carrying member (50) is set to 10 4 to 10 10 ohm c.
4. The one-component developing device according to claim 1, 2 or 3, wherein 5. An endless image carrier (40) and a latent image forming section (4) for forming an electrostatic latent image on the image carrier (40).
1, 7) and the image carrier (40) on which the electrostatic latent image is formed, and the toner regulating means (51) on the endless developer carrier (50) that conveys the one-component developer by pressing. And a one-component developing device (5) that regulates the layer thickness of the one-component developer of the developer carrying member (50) by pressing the developer carrying member (50) with a porous elastic body. In the image forming apparatus configured to apply a developing bias voltage to the developer carrying member (50), the one-component developer includes the toner (20) and the toner (2).
0) and a resin powder (21) charged to the opposite polarity, the image forming apparatus. 6. The image forming apparatus according to claim 5, further comprising transfer means (42) for transferring the developed image of the image carrier (40) onto a medium. 7. The image forming apparatus according to claim 5, wherein a voltage is applied to the toner regulating means (51) to forcibly charge the developer. 8. The pore size of the porous elastic body of the developer carrying member (50) is 2.5 times the average particle size of the toner (20).
7. The amount is set to double to four times or less.
Alternatively, the image forming apparatus of 7. 9. The volume resistivity of the porous elastic body of the developer carrying member (50) is set to 10 4 to 10 10 ohm c.
m is set to be 5 or 6 or 7 or 8
Image forming device.