JPH05158340A - Development device - Google Patents

Abstract

(57) [Summary] [Object] The present invention provides a developing device 1 capable of obtaining a high-quality image by improving the structure of a developer carrier to eliminate a bias leak phenomenon. According to the present invention, a developer carrier for carrying a developer along a predetermined circulation path, which has a carrying region 13a carrying a developer on its surface and a non-bearing region 13b not carrying a developer, is provided. In the developing device that visualizes the electrostatic latent image by contacting a carrier carrying a latent image, the electric resistance value of the non-carrying region 13b in the developer carrier is set to the carrier region 13
It is larger than the electric resistance value of a. With this configuration, the insulating property of the non-carrying region 13b is increased, the bias leak phenomenon is eliminated, and the deterioration of the image quality can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for developing an electrostatic latent image into a visible image by using it in an electrophotographic device, an electrostatic recording device or the like. The present invention relates to a developing device capable of obtaining a quality image.

[0002]

2. Description of the Related Art As one of developing methods using a one-component developer, a pressure developing method (Impression Developmennt) is known.

This method is characterized in that the electrostatic latent image and the toner particles or the toner carrier are brought into contact with each other at a relative peripheral velocity of substantially zero (US Pat. Nos. 3152012 and 3731).
148, JP-A-47-13088, JP-A-47-13089, etc.), because a magnetic material is not required, the apparatus can be simplified and downsized, and since non-magnetic toner is used, colorization is easy. It has many advantages such as

In the above-mentioned pressure developing method, it is necessary to use a developing roller having elasticity and conductivity in order to perform development by pressing or contacting the surface of the toner carrier with the electrostatic latent image.

Particularly when the electrostatic latent image carrier is a rigid body,
In order to avoid damaging this, it is an essential condition that the developing roller is made of an elastic body. Further, in order to obtain the well-known developing electrode effect and bias effect, it is preferable to provide a conductive layer on or near the surface of the developing roller and apply a bias voltage if necessary.

A conductive layer is provided on the surface of the elastic developing roller,
In order to apply a developing bias voltage to this conductive layer, it is necessary to form the developing roller with a conductor or to supply power by directly contacting the electrode with the surface of the developing roller. When the elastic developing roller is made of a conductor, rubber or sponge whose resistance is reduced by dispersing conductive carbon is used.

As described above, in the process of developing by pressing this developing roller against a photoconductor holding a latent image by using an elastic developing roller having at least a surface having conductivity, the surface of the conductive developing roller is exposed to light. By being brought into pressure-sliding contact with the body surface, the surface area of the developing roller is divided into a developing area via the toner layer and a non-developing area not via the toner layer.

Since there is a toner layer between the photosensitive layer and the conductive layer on the surface of the developing roller in the developing area, no voltage is directly applied to the photosensitive layer when a developing bias is applied, but there is no toner layer in the non-developing area. Therefore, a voltage of several hundreds of volts is directly applied to the photosensitive layer. Therefore, if there is a pinhole in the photosensitive layer, or the surface of the photosensitive member is in a state of sliding contact with the surface of the developing roller due to long-term use, the photosensitive layer is worn away, and extremely, the photosensitive layer is peeled off from the conductive base. In some cases, a bias leak phenomenon occurs between the conductive layer that is the base of the photosensitive layer and the conductive layer on the surface of the developing roller.

In the contact development system in which a developer carrying member is brought into contact with a photosensitive member for development, the bias leak phenomenon, which is the above-mentioned problem, easily occurs because a thin toner layer is formed when a developing bias voltage is applied. This is because the resistance value of the surface of the non-image portions on both ends of the developing roller is low.

[0010]

When the bias leak phenomenon as described above occurs, there is a problem that the image density is deteriorated in the reversal developing system and the background fog is generated in the regular developing system, and the image quality is remarkably deteriorated.

Therefore, it is an object of the present invention to provide a developing device capable of obtaining a high quality image by improving the structure of the developer carrying member to eliminate the bias leak phenomenon.

[0012]

In order to solve the above-mentioned problems, the invention according to claim 1 has a predetermined circulation path having a carrying region for carrying a developer on its surface and a non-bearing region for carrying no developer. In a developing device for visualizing the electrostatic latent image by contacting the developer carrying member carrying the developer along with the carrying member carrying the electrostatic latent image, The electric resistance value is made larger than the electric resistance value of the carrying region.

The invention according to claim 2 is characterized in that the electrical resistance value of the supporting region is R1 <10 ⁷ ohm · cm, and the electrical resistivity value of the non-supporting region is R2> 10 ⁸ ohm · cm. ..

[0014]

According to the invention of claim 1, the electric resistance value of the non-supporting area of the developer in the developer carrying member in the developing device for contact development is made larger than the electric resistance value of the carrying area. Insulation property is increased, the bias leak phenomenon is eliminated, and deterioration of image quality can be prevented.

Electrical resistivity value R1 <10 ^{7 of the} carrying region
Ohm · cm, electric resistivity value R2> 1 of the non-supported area
With 0 ⁸ ohm · cm, it is possible to eliminate the bias leakage phenomenon.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a developing device 1 of a contact one-component type according to this embodiment, which is applied to an electrophotographic device or the like.

The developing device 1 is arranged next to a photoconductor 11 as a carrier for carrying an electrostatic latent image.

The developing device 1 includes a toner container 14 as a developer storing means, a non-magnetic toner 15 which is a developer housed in the toner container 14, and the toner container 14.
A developing roller 12 having conductivity and elasticity as a developer carrying member, which is arranged in a state of being in contact with the photoconductor 11 and rotatably in the direction of the arrow on one end side thereof;
The supply roller 1 arranged in contact with the developing roller 12 and rotatable in the same direction as the developing roller 12.
7, a mixer 16 that agitates the non-magnetic toner 15 in the toner container 14, and a non-magnetic toner 15 that is arranged in contact with the outer circumference of the developing roller 12 and is conveyed from the supply roller 17 to the developing roller 12. And a blade 18 as a thin layer forming means for forming the thin layer on the outer circumference of the developing roller 12.

Further, the developing device 1 is provided with a bias power source 10 including a resistance R for applying a predetermined bias voltage to the developing roller 12 and the supply roller 17 and a DC power source E.

The blade 18 is rotatably held by a first blade holder 21, a spacer 22, and a second blade holder 23 around a support shaft 24, and is urged toward the developing roller 12 by a spring 25. There is.

The spring constant of the spring 25 is determined by the blade 18
Is set smaller than the spring constant of
Even if the abutting portion 18a is worn, there is almost no change in the pressing force, and a stable thin layer forming ability is maintained for a long period of time.

Further, in FIG. 1, 26 is a recovery blade made of Mylar film.

The peripheral speed of the photoconductor 11 is, for example, 70 mm /
sec, the peripheral speed of the developing roller 109 is, for example, 180 mm /
It is set to sec.

The developing roller 12 is shown in FIG.
Will be described in more detail with reference to.

The developing roller 12 is made of stainless steel and has a structure in which an elastic layer 12b and a conductive layer 12c are laminated on the outer circumference of a cylindrical metal shaft 12a having a diameter of 8 mm.

FIG. 3 shows the positional relationship between the width of the developing roller 12 and the developing area.

In FIG. 3, La is the width of the developing roller 12, which is an effective developing area in which the non-magnetic toner 13 is conveyed,
That is, the carrying area 13 a of the non-magnetic toner 13 is regulated by the blade 18 pressed against the developing roller 12. Lc is a semi-cylindrical silicon rubber tip 18a
2 shows the width of the blade 18 having a thickness of 0.2 mm which is bonded to each other.

As shown in FIG. 1, the rubber chip 18
a is pressed against the surface of the developing roller 12 by utilizing the elasticity of the blade 18. Lp is the width of the rubber chip 18a, and the non-magnetic toner 13 is conveyed in substantially this width,
It reaches the carrying region 13a.

Here, the non-magnetic toner 13 is likely to leak in a width corresponding to both ends d2 of the blade 18,
Before reaching the blade 18, urethane sponge (not shown) is pressed against both ends of the developing roller 12 to prevent the non-magnetic toner 13 from leaking.

Therefore, the non-developing area, that is, the non-carrying area 1
3b is a value obtained by subtracting the width Lp of the rubber chip 18a from the width La of the developing roller 12 and is assigned to both ends.

The supply roller 17 is a metal shaft 17
A roller having a flexible polyurethane foam layer 17b having a conductivity of 10 ⁶ Ωcm or less around a,
It is adapted to be rotationally driven in the direction of the arrow in the figure, for example, at a peripheral speed of 90 mm / sec.

The supply roller 17 not only carries the non-magnetic toner 13 described above, but also has a function of scraping off a part of the non-magnetic toner 13 remaining on the developing roller 12 without being developed. Combined.

Next, the operation of the developing device 1 will be described.

This developing device 1 does not require carrier particles, a magnet roller, a toner concentration control device, etc., and is a developing system which can be made compact and inexpensive.

Non-magnetic toner 13 in the toner container 14
Is supplied to the toner supply roller 17 while being agitated by the mixer 16.
The non-magnetic toner 13 is supplied to the developing roller 12 by the toner supply roller 17, and the toner particles are charged by friction with the surface of the developing roller 12 and electrostatically adsorbed and conveyed. After that, the toner conveyance amount is regulated by the blade 18, and at the same time, the friction between the two causes triboelectric charging of the toner.

In this embodiment, the negatively charged photoreceptor 11 is used.
Since the non-magnetic toner 13 is a negatively charged toner and the blade 18 is made of a material that easily gives negative charge, the developing bias potential is -400V with respect to the surface potential -550V of the photoconductor 11. Is supplied to the metal shaft 12a of the developing roller 12 via the resistor R, and the developing roller 12 rotates in the direction of the arrow at a speed of about 1.2 to 4 times that of the photosensitive member 11 and the photosensitive member 11 0.0 to 4 mm
There is a contact width (developing nip) of.

Further, since the toner particles are triboelectrically charged even at the developing position, an extremely sharp image can be obtained with less fog. The undeveloped toner passes through the recovery blade (mylar film) 17 and returns to the toner container 14.

Next, the relationship between the electric resistance value of the surface of the developing roller 12 and the bias leak will be described.

The elastic layer 12b of the developing roller 12 is
An elastic body made of conductive urethane rubber is provided in a roller shape on the metal shaft 12a.
A developing bias voltage can be applied by supplying power to 2a.

The conductive layer 12 is formed on the elastic layer 12b.
c is provided, which is the carrying region 13a and the non-bearing region 1
It is divided into 3b. The conductive layer 12c is formed by dispersing conductive carbon fine particles in polyurethane resin.
It has a conductivity of 0 ³ ohm · cm and can be manufactured by the following steps.

A conductive polyurethane paint was applied to the surface of the NBR rubber, dried, and then heat-treated to form it. As the conductive polyurethane paint, trade name "SPAREX DH20Z313" manufactured by Nippon Miractolan Co., Ltd. is used, and an equal amount of a diluted solution prepared by mixing methyl ethyl ketone and tetrahydrofuran at a ratio of 1: 1 is added thereto. This is a mixture of conductive carbon in a weight ratio of 30 to 40%.

"Suparex DH20Z313" is a solution type conductive polyurethane paint based on thermoplastic polyurethane. An elastic layer 12 made of NBR rubber washed with a solvent after sufficiently stirring the diluted coating material
It is applied to the surface of b by the dipping method. The pulling speed of the NBR rubber roller was 5 mm / sec. After application, it was dried in air for 30 minutes and then heat-treated at 100 degrees for about 20 minutes.

The conductor layer 12c thus prepared
Had a thickness of about 40 μm and a specific resistance value of 5 × 10 ³ ohm · cm.

However, in the portions corresponding to the non-supporting regions 13b at both ends in the length direction of the developing roller 12, the ratio of carbon dispersed in the resin is increased in order to increase the resistance value of the coating material applied to the surface of the support region 13a. Have lower than.

In this embodiment, the resistance value of the unsupported region 13b of the conductor layer 12c is 10 ⁷ ohm · cm. The film thickness of the conductor layer 12c of the developing roller 12 is at least 10 μm.
If not, the friction with the blade 18 causes abrasion.

In the manufacturing process, the conductor layer 12c is used.
When the supporting area 13a of No. 1 is formed by the dipping method, the non-supporting area 13b is masked,
Next, a high resistance non-supporting region 13b is formed by the dipping method while masking the supporting region 13a.
Adopt a process.

The electric resistance R1 of the carrying region 13a is 10 ⁷
It is known that the contrast between the image area and the non-image area is lowered when the resistance is higher than ohm · cm, and the resistance value of this portion must be set to about 10 ⁷ ohm · cm or less.

Regarding the resistance value R2 of the non-carrying region 13b, the developing roller 12 is prepared in the range of about 10 ³ ohm · cm to 10 ⁹ ohm · cm, and the developing bias voltage of about 400 V is applied without the toner layer. And the developing roller 12
The bias leak was examined under the worst condition by using an aluminum drum instead of the photoconductor 11 as the object to be pressed against. The results are shown in Table 1.

[0050]

[Table 1] As is clear from Table 1, it was confirmed that the range of R2 at which the bias leak phenomenon did not occur was R2> 10 ⁸ ohm · cm. The value of the electric resistance value was obtained from the voltage-current characteristics using a fragment of the conductor layer 12c of the developing roller 12 as a sample.

When another developing roller having a normal uniform resistance distribution (about 10 ³ ohm · cm) is used, if the photosensitive layer is damaged due to long-term use, the aluminum base and the developing roller will be damaged. A bias leak phenomenon occurs with the bias power source applied to the developing bias potential, the developing bias potential becomes 0 V even in the carrying region, and in the case of reversal developing, the developing density is remarkably reduced.

However, when the developing roller 12 of the present embodiment is used, the above-mentioned problematic phenomenon does not occur, an image density of 1.4 and an extremely sharp image without any background fog can be obtained. It was This was the same even after 10,000 sheets of life had ended.

The present invention can be modified in various ways within the scope of the invention in addition to the embodiments described above.

For example, as shown in FIG. 4, a high-resistance Teflon tube 3 corresponding to the width of the non-carrying region 13b.
It is also possible to implement a structure in which 0 is coated on both ends of the conductive developing roller 12A.

[0055]

As described above, according to the present invention, in the developing device for contact development, the electric resistance value of the non-supported area of the developer in the developer carrying member is made larger than the electric resistance value of the carrying area. It is possible to provide a developing device capable of preventing the deterioration of image quality by increasing the insulating property of the non-bearing region and eliminating the bias leak phenomenon.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a developing device of this embodiment.

FIG. 2 is a cutaway perspective view of a developing roller in the developing device according to the present exemplary embodiment.

FIG. 3 is a plan view showing a dimensional relationship of developing rollers in the developing device of the present embodiment.

FIG. 4 is a perspective view showing another example of the developing roller in the developing device of this embodiment.

[Explanation of symbols]

 1 developing device 12 developing roller 13 non-magnetic toner 13a carrying region 13b non-bearing region

Claims (2)

[Claims] 1. A developer carrying member carrying a developer on the surface thereof and a non-supporting region not carrying the developer and carrying the developer along a predetermined circulation path, carries an electrostatic latent image. In the developing device which makes the electrostatic latent image visible by contacting the carrying member, the developing device is characterized in that the electric resistance value of the non-carrying region of the developer carrying member is made larger than the electric resistance value of the carrying region. .. 2. The electrical resistivity value R1 <10 of the carrying region.
⁷ ohm · cm, electric resistivity value R2> of the unsupported area
The developing device according to claim 1, wherein the developing device has a pressure of 10 ⁸ ohm · cm.