JPH0744010A - Developing device, developer carrier and gap holding member - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a developing device in which a developer carrier has high wear resistance, excellent durability, and can exhibit a sleeve ghost prevention effect even after long-term use. is there. [Structure] A developing sleeve is formed of a conductive plastic composite material containing a conductive potassium titanate whisker. [Effect] The conductive potassium titanate whisker in the composite material acts as a leak site, and weakens the mirror power of the charged fine powder toner on the surface of the developing sleeve. Further, since the composite material has excellent wear resistance, conductivity, surface smoothness, and environmental characteristics, accumulation of fine powder on the surface of the developing sleeve is less likely to occur, and sleeve ghosts such as 15 ° C. and 10% RH are difficult to prevent. The object can be achieved even under the environment, for example, a good image without a sleeve ghost can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member, a developing device for developing an electrostatic latent image formed on an electrostatic recording dielectric image carrier, a developer carrier and a gap holding member. .

[0002]

2. Description of the Related Art As a developing device for developing an electrostatic latent image formed on an image carrier of an electrophotographic photosensitive member or an electrostatic recording dielectric, a predetermined minute gap is provided in a developing area facing the image carrier. It is known to develop an electrostatic latent image by transferring the developer from the developer carrying member to the electrostatic latent image on the image carrying member and applying it. An example of such a developing device is shown in FIG.

As shown in FIG. 9, the developing device 10 is installed so as to face a drum-shaped electrophotographic photosensitive member which is an image bearing member of the image forming apparatus and which rotates in the arrow direction, that is, the photosensitive drum 1. An electrostatic latent image is formed on the surface 1 by a known electrostatic latent image forming unit 20 including a charger and an exposing unit. As the exposing means, a means for projecting an optical image of a document, an optical system for scanning a laser beam modulated by a recorded image signal, or the like is adopted, and the latent image formed on the photosensitive drum 1 is developed by the developing device 10. And a toner image is formed.

The obtained toner image is transferred onto a transfer material such as paper by a known transfer means 30 including a transfer charger. The transfer material on which the toner image has been transferred is separated from the photosensitive drum 1 and sent to a known fixing means (not shown), where the toner image is fixed on the transfer material. The toner remaining on the photosensitive drum 1 after the transfer is removed by a known cleaning unit 40 including a cleaning blade and the like.

The developing device 10 contains an insulating one-component magnetic developer 11 containing no carrier particles in a developing container 12. The developer 11 is mainly composed of an insulating magnetic toner, and preferably, silica fine powder is slightly added externally. The fine silica powder is externally added for the purpose of controlling the triboelectric charge of the toner so as to increase the image density and obtain an image with less roughness. For example, it is known to externally add vapor phase silica (dry silica) and / or wet process silica (wet silica) to the toner.

[0006] such as styrene - to the negative polarity toner containing 60 parts by weight of magnetite acrylic resin, a strong contrast negative charging characteristics indicating a dry silica (e.g., 100 m ² fumed silica, HMDS the 100 m ² per 10 parts by weight The developer added externally with a heat treatment) added thereto is suitable for reversal development of a negative electrostatic latent image.

One-component magnetic developer, namely magnetic toner 11
Is carried out of the container 12 by a non-magnetic developing sleeve 14 which is a developer carrying member and which rotates in the direction of the arrow, such as aluminum or stainless steel, and is conveyed to the developing area 13 facing the photosensitive drum 1. In the developing area 13, the photosensitive drum 1 and the developing sleeve 14 face each other with a minute gap of 50 to 500 μm. In the developing area 13, the toner 11 is transferred and applied to the electrostatic latent image on the photosensitive drum 1, and the electrostatic latent image is developed as a toner image.

A holding member for maintaining a gap (SD gap) between the developing sleeve 14 and the photosensitive drum 1 in the developing area 13 is, as shown in FIG. 10, a cap type SD roller 19 fitted to both ends of the developing sleeve 14. Is formed in. Each S
The D roller 19 includes a thin-walled cylindrical portion 19b that constitutes a portion to be fitted to the end portion of the developing sleeve 14, and a thick-walled contact portion 19 formed around the opening side of the cylindrical portion 19b and the photosensitive drum 1.
It consists of a and.

The SD roller 19 is made of polyacetal resin (POM resin) (trade name Delrin, manufactured by DuPont), which is insulative and has a good lubricating property, and is fitted on the end portion of the developing sleeve 14 to be rotatable. It is provided. And SD roller 1
9 rotates in contact with the surface of the photosensitive drum 1 so that a predetermined S is provided between the photosensitive drum 1 and the developing sleeve 14.
It is designed to hold the D gap. In this example, since the SD gap is 300 μm, the contact portion 19 of the SD roller 19 is
The wall thickness of a is about 300 μm, and the wall thickness of the cylindrical portion 19b is about 250 μm.

The developing sleeve 1 conveyed to the developing area 13.
The thickness of the toner 11 on the sheet 4 is regulated by the elastic blade 16. The elastic blade 16 is made of an elastic material such as urethane rubber, and substantially faces the magnetic pole N1 of the magnet roller 15 which is stationary in the developing sleeve 14. Due to the regulation of the toner 11 by the elastic blade 16, a thin toner layer 11 a is formed on the developing sleeve 14.

The elastic blade 16 and the developing sleeve 14
The gap between the developing sleeve 14 and the toner layer 11a
Is set to a minimum gap between the photosensitive drum 1 and the photosensitive drum 1, that is, a gap that can be made thinner than the SD gap between the two in the developing area 13.

As described above, in the developing device shown in FIG. 9, so-called non-contact development is performed. That is, development area 1
The thickness of the toner layer 11a conveyed to the developing sleeve 3 is
Since the toner 11 is thinner than the minute gap between the photosensitive drum 1 and the photosensitive drum 1, the toner 11 reaches the photosensitive drum 1 through the air gap from the developing sleeve 14. And improve the development efficiency at that time,
A developing bias voltage including an AC component is applied to the developing sleeve 14 from the bias power source 18 in order to form a developed image having high density and clear and suppressed fog.

As described above, the developing bias voltage is preferably a DC voltage superimposed with an AC voltage. The development bias voltage is the dark area potential of the latent image between its maximum and minimum values.
It is preferable that the voltage is such that the light portion potential exists, and that the above-mentioned DC voltage value exists between the dark portion potential and the light portion potential of the latent image. The frequency of the alternating voltage is 1-2 kH
z, peak-to-peak voltage (difference between maximum and minimum values)
Is preferably about 1.1 to 1.8 kV, and a rectangular wave, a sine wave, a triangular wave or the like is used as the waveform.

For example, when a latent image having a dark portion potential of −700 V and a light portion potential of −100 V is subjected to reversal development with negatively charged toner, the developing bias voltage has a DC component of −500.
V and AC components have a peak-to-peak voltage of 1.6k
A rectangular wave voltage of V and a frequency of 1.8 kHz can be used.

The developing bias voltage causes the toner 11
The electric field in the direction of transferring from the developing sleeve 14 to the photosensitive drum 1 and the electric field in the direction of transferring from the photosensitive drum 1 to the developing sleeve 14 act alternately. As a result, a good developed image can be obtained.

The reversal development is a development method in which a latent image of a latent image is visualized by adhering toner charged with the same polarity as that of the latent image to the potential portion of the latent image. On the other hand, a developing method in which toner charged with a polarity opposite to that of the latent image is made to adhere to a dark potential region of the latent image to make it visible is called normal development.

The toner 11 is charged to a polarity for developing an electrostatic latent image mainly by friction with the developing sleeve 14. As the toner 11, for example, a binder resin containing a styrene-acrylic copolymer as a main component and magnetite 6
Based on an insulating magnetic toner having a volume resistivity of about 10 ¹³ Ωcm containing 0% by weight and 1% by weight of a metal complex salt of a monoazo dye as a negative charge control agent, which was subjected to a hydrophobizing treatment to enhance fluidity. The silica fine particles were added to the toner weight of 0.
4% by weight externally added is used. Such toner is negatively charged by friction with the developing sleeve 14.

The magnetic pole S1 of the magnet roller 15 forms a magnetic field in the developing area 13 to prevent fog and contribute to clear development of a line image. The magnetic poles N2 and S2 contribute to the toner conveyance.

By the way, the toner is not consumed in the area of the developing sleeve 14 facing the non-image area of the photosensitive drum 1, but if the toner is not consumed continuously, it is considered that the developing sleeve is caused by electrostatic mirroring force. Not only is the fine powder layer strongly adhered and is not easily consumed in the image area of the photosensitive drum, but also the charge amount of the toner on the fine toner layer is reduced. Therefore, a ghost image is generated on the developed image, and the image quality is deteriorated.

FIG. 11 shows an example of the ghost image. The part (a) of FIG. 11 is the part where the image is developed after the white background continues, and the part (b) of FIG. 11 is the part where the image is developed again after the image continues. The density of the portion (b) is higher than that of the portion (a).

According to the experiments and consideration by the present inventors, the mechanism of this ghost generation is such that fine powder formed on the developing sleeve (having a particle size 4 much smaller than that of a toner having a normal particle size).
(mainly composed of toner particles of μm or less). That is, the toner particle size distribution of the lowermost layer of the toner layer on the developing sleeve has a clear difference between the toner consuming portion and the non-consuming portion, and a fine powder layer is formed on the lowermost layer of the toner layer in the non-consuming portion. Since the fine powder has a large surface area per volume, the amount of triboelectric charge per unit weight is larger than that of particles having a large particle size, and the fine powder itself is electrostatically strong against the developing sleeve due to the mirroring force. Be detained.

Therefore, the toner in the upper layer of the portion where the fine powder layer is formed is not triboelectrically charged sufficiently by the developing sleeve, so that the triboelectric charge amount decreases, and as a result, the sleeve ghost (partially imaged) is formed on the developed image. It appears as (low concentration). Especially when a toner having a small average particle size (9 μm or less) is used, this ghost tends to be remarkable.

In particular, in magnetic toner, the amount of magnetic material contained in each fine powder toner particle tends to be smaller than the amount of magnetic material contained in toner having an appropriate particle diameter, and the charge amount per unit weight is small. Since the charge amount per unit weight of the toner particles having an appropriate particle diameter is higher, the adhesion due to the mirroring force on the developing sleeve is strong, and the ghost phenomenon becomes more remarkable.

Such a sleeve ghost phenomenon has been solved by the techniques proposed in JP-A-1-276174, JP-A-1-27726 and JP-A-2-176682. The techniques proposed in these publications are characterized by using a developing sleeve in which a resin in which conductive fine particles such as carbon fine particles and / or graphite fine particles are dispersed is coated on an aluminum sleeve substrate. Further, Japanese Unexamined Patent Publication (Kokai) No. 2-109073 is characterized in that a developing sleeve formed of a composite material containing carbon fiber and polymer resin is used. In both cases, the occurrence of sleeve ghost is prevented.

This is because the excess charge of the fine powder toner is eliminated by the leak site formed by the resin and the conductive fine particles or the carbon fibers exposed on the surface, and the mirror power of the fine powder toner with respect to the developing sleeve is weakened. It is prevented.

[0026]

However, as described above, a developing sleeve in which a resin containing conductive particles such as carbon is coated on an aluminum sleeve substrate is used, and a cap type SD roller is used for the developing sleeve. Maintaining the SD gap with the photosensitive drum causes the following problems.

The conductive fine particle-containing resin coat layer on the developing sleeve is gradually worn away as the number of images formed is increased, so that the effect of reducing ghost is reduced. Especially when a toner having a small average particle size (particle size of 9 μm or less) is used, an elastic rubber blade must be used in order to stably impart a uniform triboelectric charge to the toner.
The rubbing of the coating layer on the surface of the developing sleeve is severe, and a sleeve ghost is generated when an image is formed on several thousand sheets, and the life of the developing sleeve is exhausted.

Also, the cap type SD roller of the SD gap holding member may be scraped by sliding friction when deformed in contact with the surface of the photosensitive drum or deformed into a trumpet shape, so that the SD gap cannot be held constant. is there. In particular, when the SD gap is made small, it is necessary to make the SD roller ultra-thin, so that it is difficult to form the roller, and it is easily deformed and the cost is high.

In this case, it is conceivable to provide thick portions at both ends of the developing sleeve to maintain the SD gap, but in the case of an aluminum developing sleeve, the aluminum portion of the photosensitive drum is exposed to the ground portion. The developing roller and the developing sleeve have to be insulated from each other, which eventually requires SD rollers (which are insulative), and this method is not effective.

An object of the present invention is to provide a developing device in which the developer carrier has high wear resistance, excellent durability, and can exhibit a sleeve ghost prevention effect even after long-term use. is there.

Another object of the present invention is to provide a gap holding member that maintains a minute gap between the developer bearing member and the image bearing member, which has high wear resistance and excellent durability, and has a predetermined minute amount even after long-term use. It is an object of the present invention to provide a developing device capable of maintaining a constant gap.

Still another object of the present invention is to provide a developer carrier and a gap holding member having the above characteristics.

[0033]

The above items are achieved by the developing device, the developer carrying member and the gap holding member according to the present invention. In summary, according to the present invention, the developer is carried on the developer carrier having a predetermined minute gap between the image carrier and the image carrier in the developing area facing the image carrier by the gap holding members provided at both ends. In the developing device for transferring the developer onto the image carrier in the developing region to develop the electrostatic latent image formed on the image carrier, the developer carrier is electrically conductive. The developing device is formed of a conductive plastic composite material containing treated potassium titanate whiskers.

The gap holding member is integrally provided at both ends of the developer carrying member, and the gap holding member is formed of an insulating plastic composite material containing potassium titanate whiskers which has not been subjected to a conductive treatment. . Alternatively, the gap holding member is provided so as to be fitted on both ends of the developer carrying member, and the gap holding member is formed of an insulating plastic composite material in which potassium titanate whiskers which have not been electrically conductive are mixed.

Further, in the present invention, a gap holding member for opening a predetermined minute gap with the image carrier is provided at both ends in the developing region facing the image carrier so that the developer is carried and conveyed to the developing region. The developer carrier according to the item (1), which is formed of a conductive plastic composite material containing a conductivity-treated potassium titanate whisker.

Further, the present invention is provided by fitting the developer carrying member on both ends of the developer carrying member for opening a predetermined minute gap with the image carrying member in the developing area facing the image carrying member. A gap holding member, which is formed of an insulating plastic composite material containing a non-conductive-treated potassium titanate whisker.

[0037]

【Example】

Embodiment 1 FIG. 1 is a configuration diagram showing an embodiment of a developing device of the present invention, and FIG. 2 is a perspective view showing a developing sleeve provided in the developing device of FIG. The present embodiment is characterized in that the developing sleeve 17 molded from a conductive plastic composite material containing a conductive potassium titanate whisker is used as the developer carrying member. The other configurations of the developing device of this embodiment are basically the same as those of the conventional developing device shown in FIG. 9, and the same reference numerals as those in FIG. 1 denote the same members.

The developing device 10 of this embodiment is a developing container 1 containing a magnetic toner 11 which is an insulating one-component magnetic developer.
2, the developing sleeve 17 is disposed in the opening of the developing container 12 facing the photosensitive drum 1. The toner 11 in the developing container 12 is carried on the developing sleeve 17 by the magnet roller 15 built in the developing sleeve 17, and is conveyed to the developing area 13 facing the photosensitive drum 1 as the developing sleeve 17 rotates. During the conveyance, the toner 11 on the developing sleeve 17 is regulated by the elastic blade 16 provided above the opening of the container 12 and is formed on the thin toner layer 11a.

Toner layer 11 conveyed to developing area 13
Is used for developing the electrostatic latent image on the photosensitive drum 1, and the latent image is developed and visualized as a toner image. At the time of development, a bias power source 18 prints a developing bias in which an AC voltage is superimposed on a DC voltage on the developing sleeve 17.

The developing sleeve 17 has an outer diameter of 16 mm.
As shown in FIG. 2, the longitudinal direction is the development area portion 17a used for development and the cap type SD on both sides thereof.
It is divided into an end portion 17b into which a roller (not shown) is fitted. The surface of the developing area 17a is sandblasted in order to provide the developing area 17a with an appropriate surface roughness and to impart chargeability and toner transportability to the toner, and the center specified in JIS-B0601. The average roughness Ra is approximately 2 μm. The end portion 17b is not subjected to sandblasting in order to fit the SD roller, and has a surface center average roughness Ra≈0.03 μm.

As described above, the developing sleeve 17 is made of a conductive plastic composite material filled with conductive potassium titanate whiskers (general formula of potassium titanate: K ₂ O.nTiO ₂ ). In this example, as a conductive plastic composite material filled with conductive potassium titanate whiskers, Wistat (trade name) manufactured by Otsuka Chemical
It was used.

This wistat has an average fiber diameter of 0.3 to
Conductive treatment was performed on the surface of potassium titanate whiskers (trade name: Tismo, made by Otsuka Chemical) having an average fiber length of 0.7 to 20 μm, and the obtained conductive potassium titanate whiskers (trade name: Dentor, made by Otsuka Chemical). It is made of a conductive plastic composite material in which is mixed with POM resin. This wistat is molded at a temperature of about 200 ° C and the mold temperature at about 10
A developing sleeve made of a conductive plastic composite material can be obtained by molding using a known extruder at 0 ° C. and a pressure of about 1000 kg / cm ² .

According to such a conductive plastic composite material, the volume resistivity of the conductive potassium titanate whisker, and hence the volume resistivity of the developing sleeve 17, can be easily controlled by changing the compounding ratio of the conductive potassium titanate whiskers. . Specifically, conductive potassium titanate whisker content ratio of about 25 wt% or more, if preferably above about 40 wt%, can the volume resistivity of the developing sleeve 10 ⁰ [Omega] cm or less, almost the aluminum developing sleeve It was possible to obtain the same electrical resistance.

After forming the developing sleeve 17, the developing area portion 17a was sandblasted as described above. For sandblasting, a blasting machine manufactured by Fuji Manufacturing Co., Ltd. was used, and a nozzle of the type 3 (diameter of about 6 mm) was used. As the irregular-shaped abrasive grains, alundum abrasive grains (trade name: Morundum A # 400, manufactured by Showa Denko) were used. The blast conditions were a pressure of 2.0 k / cm ² and a time of 20 seconds. If necessary, air blasting or cleaning in alcohol can be added to the blast treatment after the treatment.

In this embodiment, as described above, the developing sleeve 17 is formed of the conductive plastic composite material containing the conductive potassium titanate whiskers. According to this
Since the conductive potassium titanate whiskers are needle-shaped crystals, they have the effect of acting as leak sites, and weaken the mirror power of the charged fine powder toner on the surface of the developing sleeve. Further, this conductive plastic composite material is excellent in conductivity, surface smoothness and environment, and it is difficult for accumulation of fine powder on the surface of the developing sleeve to occur, so that sleeve ghost and charge-up hardly occur.

As a result, not only in a normal environment, for example, 15
Even in a low-humidity environment where it was difficult to completely prevent sleeve ghosts, such as at 10 ° C. and 10% RH, good images without sleeve ghosts could be obtained.

Further, since the conductive plastic composite material has excellent wear resistance, the developing sleeve 17 has high wear resistance and also has excellent durability.

An experimental example using the developing sleeve of this embodiment will be described. The developing sleeve 17 was incorporated in the developing device 10 shown in FIG. 1 and used for development, and image formation was performed under a normal environment. The developing sleeve 17 is biased by a bias power source 18 at VDC = -500V, VAC (peak-to-peak voltage Vpp) = 1600V, frequency 1800Hz.
Was applied. The SD gap between the developing sleeve 17 and the photosensitive drum 1 was about 300 μm.

The experimental results are shown in Table 1. As shown in Table 1, in the developing sleeve (conventional sleeve) coated with the conventional carbon fine particle-containing resin, the effect of reducing the sleeve ghost was found to decrease due to the image formation of about 10,000 sheets. With the developing sleeve made of a plastic composite material (the sleeve of the present invention), the effect of reducing the sleeve ghost did not change even after the image formation of about 50,000 sheets, and long-term stability was shown.

[0050]

[Table 1]

In the above, the conductive plastic composite material used for the developing sleeve 17 was mixed with the conductive potassium titanate whisker which was made conductive by the conductive treatment, but the present invention is not limited to this, and various metals can be used. Conductive potassium titanate whiskers whose surface is coated with a material to make them conductive can be used. Specifically, Super Dentol (trade name, made by Otsuka Chemical) coated with silver, and Riobert (trade name, made by Otsuka Chemical) coated with copper or nickel.
Can be used.

These metal-coated conductive potassium titanate whiskers have a volume resistivity of 1 × 1 with super dentol.
It has a very low resistance of 0 ^-4 Ωcm and 5 × 10 ^-4 Ωcm at Riobert, and by using a conductive plastic composite material containing these, a developing sleeve with a further excellent sleeve ghost reduction effect can be obtained. Obtainable.

Further, although the present invention is applied to the sleeve-shaped developer carrier, the present invention is not limited to this, and is also applied to the elastic roller-shaped developer carrier used in contact with the photosensitive drum. be able to.

Embodiment 2 FIG. 3 is a schematic structural view showing another embodiment of the developing device of the invention. This embodiment is applied to a developing device using a non-magnetic one-component developer containing no magnetic material, that is, a non-magnetic toner (non-mag toner). 3, the same reference numerals as those shown in FIG. 1 denote the same members.

As shown in FIG. 3, the developing device 10 of the present embodiment is provided with a developing sleeve 25 in the opening portion of the developing container 10 containing the non-magnetic toner 24 facing the photosensitive drum 1, and inside the developing sleeve 25. There is no magnet roller installed.

Similar to the developing sleeve 17 of the first embodiment, the developing sleeve 25 is formed by molding a conductive plastic composite material WISTAT (trade name, manufactured by Otsuka Chemical Co., Ltd.) containing conductive potassium titanate whiskers. Has been done.

Similarly, the surface of the developing area portion of the developing sleeve 25 is appropriately roughened. However, in this embodiment, the surface is JIS-formed by sandblasting using irregularly shaped alundum abrasive grains. The ten-point average roughness Rz specified in B0601 is set to Rz≈1 to 10 μm.

As in the first embodiment, an elastic blade 21 for restricting the toner 24 carried on the developing sleeve 25 is provided above the opening of the developing container 12. The elastic blade 21 is inclined so as to descend toward the upstream side in the rotation direction of the developing sleeve 25, and
Although they are abutted in the direction opposite to the rotation direction, they may be abutted in the forward direction.

An elastic roller 22 made of sponge rubber having a cell number of 20 to 100 cells / inch is provided at a position upstream of the elastic blade 21 in the container 12 in the rotational direction of the developing sleeve 25. The elastic roller 22 rubs the non-magnetic toner 24 against the developing sleeve 25 to support it.
It also serves to peel off the toner returned from the developing area 13 without being used for development from the developing sleeve 25. At the lower part of the opening of the container 12, a prevention member 23 that is in contact with the developing sleeve 25 and prevents the toner 24 from leaking from the container 12 is provided.

The non-magnetic toner 24 is made by dispersing a pigment such as carbon in a thermoplastic resin such as styrene resin, acrylic resin or polyethylene resin. The toner 24 is preferably used by externally adding fine silica powder.

In the developing device of this embodiment, the elastic roller 22
Rotates in the direction of the arrow to supply the non-magnetic toner 24 near the developing sleeve 25, and the toner 24 is fed to the elastic roller 22.
And the developing sleeve 25 are in contact with each other at a nip portion (abutting width in the circumferential direction of 1 to 1 mm) to rub against the developing sleeve 25 so that the developing sleeve 25 adheres and carries the developing sleeve 25. This elastic roller 2
2 and the developing sleeve 25 have a rotational speed of 5 to 5 between them.
A peripheral speed difference of 600 mm / sec is provided.

Toner 2 carried on the developing sleeve 25
4 is conveyed toward the developing area 13 with the rotation of the developing sleeve 25, is rubbed by the elastic blade 21 to be formed on the thin layer 24a during the conveyance, and is subjected to a sufficient amount of triboelectrification. The subsequent developing process is the same as that of the conventional developing device described with reference to FIG.

In this embodiment, the abrasion of the developing sleeve 25 caused by the sliding friction of the elastic roller 22 and the elastic blade 21 is larger than that of the developing sleeve 17 of the first embodiment. However, like the developing sleeve 17, potassium titanate is used. Since it is made of a plastic composite material containing whiskers, it withstands abrasion and exhibits the desired performance.

According to the experiment conducted in this embodiment,
In the conventional developing sleeve coated with the carbon fine particle-containing resin, the triboelectrification charge imparting ability for the non-magnetic toner 24 was lowered by the image formation of about 2,000 sheets, but with the developing sleeve 25 of this embodiment, about 20,000 sheets were obtained. Even in the image formation, the triboelectric charge imparting ability did not change, and a good image density of about 1.4 was maintained.

Embodiment 3 FIG. 4 is a schematic configuration diagram showing still another embodiment of the developing device of the present invention. The present embodiment is applied to a developing device using a two-component developer composed of toner and carrier.

As shown in FIG. 4, the developing device 10 of this embodiment includes a developing container 12 containing a two-component developer 27, and a developing sleeve 26 is arranged in the opening of the container 12 facing the photosensitive drum 1. In the developing sleeve 26, a magnet roller 29 having a plurality of magnetic poles, in this example, 8 magnetic poles, is installed.

The developing sleeve 26 is formed of a conductive plastic composite material Wistat (trade name, manufactured by Otsuka Chemical Co., Ltd.) containing conductive potassium titanate whiskers, as in the previous embodiments. . Example 2
Similarly to the above, the surface of the developing area portion of the developing sleeve 26 is sandblasted with irregular-shaped alundum abrasive grains,
Ten-point average roughness Rz≈1 specified in JIS-B0601
It is set to 10 μm.

At the upper part of the opening of the developing container 12, a doctor blade 28 for restricting the length of the magnetic brush of the two-component developer 27 carried on the developing sleeve 26 is spaced apart from the developing sleeve 28 by a predetermined distance. A developer stirring mechanism 35 is provided in the container 12.

In this embodiment, the magnet roller 29 in the developing sleeve 26 rotates in the direction of the arrow. The magnet roller 29 may rotate in the direction opposite to the arrow. By the rotation of the magnet roller 29 and the rotation of the developing sleeve 26, the developer 27 carried on the developing sleeve 26 is conveyed toward the developing area 12, and during the conveyance, the developer 27 is thinly layered by the doctor blade 28. 27a is formed to adjust the length of the magnetic brush.

According to the experiment conducted in this embodiment,
The developing sleeve 26 made of a conductive plastic composite material is
It is also effective when a two-component developer is used, and a good image density of about 1.4 was maintained even when forming an image on about 20,000 sheets.

Embodiment 4 FIG. 5 is a perspective view showing a developing sleeve in still another embodiment of the developing device of the present invention. In this embodiment, as shown in FIG. 5, the SD contact portion 3 is provided on both ends of the developing sleeve 31.
The feature is that 1b is integrally provided and has the function of the SD roller. The SD contact portion 31b is insulative.

As in the case of Example 1, the developing region portion 31a except the both ends of the developing sleeve 31 is a POM-based conductive plastic composite material Wistat (trade name; Otsuka Chemical Co., Ltd.) containing conductive potassium titanate whiskers. Product) was molded and formed.

The SD contact portion 31b of the developing sleeve 31 is
About 10 wt% of conductive potassium titanate whisker
%, A POM-based high resistance plastic composite material (trade name: Whist, volume resistivity 10 ¹⁵ Ωcm or more; manufactured by Otsuka Chemical Co., Ltd.) was used and molded together with the development area portion 31a.

The developing sleeve 3 is the same as in the first embodiment.
In the developing area portion 31a of No. 1, chargeability to toner,
In order to impart toner transportability, an appropriate surface roughness (R
a or Rz).

SD on a conventional aluminum developing sleeve
With a combination of rollers, since the straightness of the cylinder of the sleeve tube is about 30 μm and the tolerance of the SD roller is about 30 μm, the SD gap between the photosensitive drum and the developing sleeve can fluctuate by about 60 μm in the worst case. There was a nature. According to the developing sleeve 31 of this embodiment, since the whiskers to be mixed are extremely fine, the mold transferability of the plastic composite material molded product is high, and the straightness of the cylinder can be increased to about 7 μm. Since there is no cap-type SD roller on the body, the variation of the SD gap can be suppressed to 10 μm or less, which is very useful for improving the image quality.

Also, for example, 100 μ, which is effective for recent high image quality,
Small S that cannot be set with SD rollers, such as m or less
Even the D gap can be realized without problems by using the developing sleeve 31 provided with the SD contact portion 31b of the present embodiment. Since the SD contact portion 31b is also made of a plastic composite material and has excellent wear resistance, the SD contact portion 31b has a long service life.
With an SD roller, even if it is created by a method such as shaving from a round bar, the life of the SD roller is limited to the formation of thousands of images.

Table 2 shows the results of the experiment conducted in this example.

[0078]

[Table 2]

As shown in Table 2, when a cap type SD roller is combined with a conventional developing sleeve coated with a resin containing carbon fine particles (conventional coated sleeve),
By forming about 5,000 sheets, the SD roller pitch unevenness in the image (unevenness of several mm due to SD roller dirt) and cycle unevenness (SD roller cycle of about 50 m due to SD roller deformation etc.)
Although the image deterioration such as m) occurs, the developing sleeve 31 of the present embodiment (the sleeve with the SD contact portion of the present invention) has an S-shaped insulating plastic composite material at both ends.
Since the D contact portion 31b is integrally formed, there is no image deterioration such as pitch unevenness even when forming about 20,000 images, and about 1.4
The image density was maintained to some extent.

In Examples 1 to 4 described above, a general POM-based material was used as the conductive plastic composite material and the insulating plastic composite material, but PA (nylon) was used.
It is also possible to use a material such as a PPS-based (polyphenylene sulfide) -based material.

Embodiment 5 FIG. 6 is a perspective view showing a developing sleeve in still another embodiment of the developing device of the present invention. In this embodiment, as shown in FIG. 6, the SD contact portion 3 is provided on both ends of the developing sleeve 32.
Insulating plastic composite material (trade name POTICON, manufactured by Otsuka Chemical Co., Ltd.) in which the SD contact portion 32b having 2b is compounded with potassium titanate Wis (trade name Tismo manufactured by Otsuka Chemical Co., Ltd.), which has not been treated to be conductive. ).

The developing area portion 32a of the developing sleeve 32 is formed of PIST-based conductive plastic composite material Wistat (trade name, manufactured by Otsuka Chemical Co., Ltd.) containing conductive potassium titanate whiskers, as in the first embodiment. did. Similarly, the developing area portion 32a is blasted to have an appropriate surface roughness in order to impart chargeability to the toner and transportability of the toner.

In the present embodiment as well, as in the case of the fourth embodiment, the cap SD card is not required for the developing sleeve 32, so that even a minute SD gap of 100 μm or less which cannot be set by the SD roller can be realized without any problem. In addition, the SD contact portion 32b and the like are excellent in wear resistance and have a long service life.

According to the experiment conducted in this embodiment, when the conventional developing sleeve coated with the resin containing carbon fine particles is combined with the cap type SD roller, the SD image is formed in the image by forming about 5,000 sheets. Although the image deterioration such as the pitch unevenness of the rollers was observed, the SD contact portion 32 is formed on both ends of the present embodiment.
According to the developing sleeve 32 integrally formed with b, the image deterioration such as pitch unevenness did not occur even when the image was formed on about 20,000 sheets, and the good image density was maintained.

Sixth Embodiment FIG. 7 is a perspective view showing a developing sleeve in still another embodiment of the developing device of the present invention. In this embodiment, as shown in FIG. 7, a conventional aluminum developing sleeve 33 is used.
The SD contact portion 33b is formed by coating an insulating plastic composite material (trade name: POTICON, manufactured by Otsuka Chemical Co., Ltd.), which is mixed with potassium titanate wis which has not been electrically conductive, on both ends of the SD contact portion 33b. SD gap is about 150 μm
The thickness of the SD contact portion 33b is also about 150μ.
It was set to m. The above-mentioned coating is performed by melting the plastic composite material containing the whistle at, for example, about 200 ° C. and dipping the both ends of the developing sleeve 33, or
Alternatively, it can be carried out by dissolving a plastic composite material containing a whistle in a solvent and dipping it therein.

The developing region portion 33a excluding both ends of the developing sleeve 33 is formed by coating the aluminum sleeve with a resin containing carbon fine particles and applying the resin, followed by drying, as is conventional.

In this embodiment, since the conventional type aluminum developing sleeve is used as a base, the life of the developing area portion 33a of the developing sleeve 33 is the same as the conventional one, but the cap type SD roller is not used. No deterioration in image life such as unevenness due to long-term use was ameliorated, because there was no reduction in the life of the SD roller due to abrasion or deformation.

Embodiment 7 FIG. 8 shows S in still another embodiment of the developing apparatus of the present invention.
It is a perspective view showing a D roller. In this embodiment, in order to maintain the SD gap with the photosensitive drum, the cap sleeve S is attached to the developing sleeve.
In the case of using the D roller 34, the SD roller 34 was formed of a POM-based insulating plastic composite material (POTICON, manufactured by Otsuka Chemical Co., Ltd.) in which a potassium titanate whisker that was not subjected to a conductivity treatment was blended.

The SD roller 34 is composed of a thin-walled cylindrical portion 34b to be fitted into the end portion of the developing sleeve, and a thick-walled contact portion 34a with the photosensitive drum around the opening side of the cylindrical portion 34b. In this example, the wall thickness of the cylindrical portion 34b is about 150.
The thickness of the cylindrical portion 34a is about 100 μm.

Conventionally, a problem in producing an SD roller is that it is difficult to form a thin-walled cylindrical portion necessary to keep the SD gap stable. When molding SD rollers with a mold, it is often not possible to sufficiently form a thin-walled cylindrical portion.
In the mass-produced roller, 250 μm was the limit of the SD gap.

The insulating plastic composite material POTICON used in this example had an average fiber system of 0.3 to 0.7 μm,
Since the potassium titanate whiskers having an average fiber length of 10 to 20 μm are mixed as a reinforcing material, the SD roller 34 having the ultrathin cylindrical portion 34a of about 100 μm can be formed. Further, since the SD roller 34 is excellent in dimensional accuracy, surface smoothness and wear resistance, the life and strength of the SD roller 34 are improved.

Table 3 shows the results of the experiment conducted in this example.

[0093]

[Table 3]

As shown in Table 3, the conventional POM S
In the D roller, image defects such as pitch unevenness due to the SD roller occurred in the image due to the image formation of about 4000 sheets, but the SD roller 34 made of the plastic composite material containing the potassium titanate whisker of the present embodiment (SD roller of the present invention). So, even with the image formation of about 16,000 sheets, deterioration such as pitch unevenness was not recognized,
Good results have been obtained.

In the above, the SD roller 34 is formed of the POM-based insulating plastic composite material, but the present invention is not limited to this.
Materials such as PA and PPS can be used.

Even in the case of conductive potassium titanate whiskers, if the compounding ratio is reduced to about 10 wt% or less, it is replaced with potassium titanate whiskers which have not been treated for conductivity,
It is possible to mix it with an insulating plastic composite material.

[0097]

As described above, in the present invention, since the developer carrier is formed of the conductive plastic composite material containing the conductive potassium titanate whiskers, the long life of the developer carrier, Provided is a developing device that achieves high durability and greatly reduces image deterioration due to long-term use.

Further, according to the developer carrying member having SD contact portions integrally provided at both ends as the SD gap holding member by the insulating plastic composite material containing the non-conductive-treated potassium titanate whiskers, Unlike a gap holding member such as a roller, it is possible to prevent image deterioration such as unevenness due to abrasion or deformation of the SD gap abutting portion, and it is possible to reduce the cost.

Further, according to the SD roller of the cap type formed by the insulating plastic composite material containing the potassium titanate whisker which is not subjected to the conductivity treatment, the dimensional accuracy is
SD roller with excellent surface smoothness and wear resistance can be realized.
The predetermined SD gap can be maintained constant, and the life and strength of the SD roller can be greatly improved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a developing device of the present invention.

FIG. 2 is a perspective view showing a developing sleeve provided in the developing device of FIG.

FIG. 3 is a schematic configuration diagram showing another embodiment of the developing device of the invention.

FIG. 4 is a schematic configuration diagram showing still another embodiment of the developing device of the present invention.

FIG. 5 is a perspective view showing a developing sleeve in still another embodiment of the developing device of the present invention.

FIG. 6 is a perspective view showing a developing sleeve in still another embodiment of the developing device of the present invention.

FIG. 7 is a perspective view showing a developing sleeve in still another embodiment of the developing device of the present invention.

FIG. 8 shows S in still another embodiment of the developing device of the present invention.
It is a perspective view showing a D roller.

FIG. 9 is a schematic configuration diagram showing a conventional developing device.

10 is a cross-sectional view showing setting of an SD gap between a developing sleeve provided in the developing device of FIG. 9 and a photosensitive drum.

11 is an explanatory diagram showing a sleeve ghost that has occurred when the developing device in FIG. 9 is used.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum 10 Developing device 13 Developing area 17, 25, 26, 31, 32, 33 Developing sleeve 31b, 32b, 33b SD contact part 34 SD roller

Claims (5)

[Claims] 1. A developer is carried on a developer carrier having a predetermined minute gap from the image carrier in a developing region facing the image carrier by means of a gap holding member provided at both ends, and development is carried out. In a developing device that conveys the developer onto the image carrier in the developing region and develops the electrostatic latent image formed on the image carrier in the developing region, the developer carrier is subjected to a conductive treatment. A developing device formed of a conductive plastic composite material containing a potassium titanate whisker. 2. The gap holding member is integrally provided at both ends of the developer carrying member, and the gap holding member is made of an insulating plastic composite material containing a non-conductive potassium titanate whisker. The developing device according to claim 1, which is formed. 3. The insulating plastic composite material, wherein the gap holding member is provided by fitting on both ends of a developer carrying member, and the gap holding member is blended with potassium titanate whisker which is not subjected to a conductive treatment. The developing device according to claim 1, which is formed by. 4. A developer for carrying a developer and transporting the developer to a developing area, wherein a gap holding member for opening a predetermined minute gap with the image carrying body in a developing area facing the image bearing body is provided at both ends. A developer carrier, which is formed of a conductive plastic composite material containing conductive potassium titanate whiskers. 5. A gap holding member, which is provided by being fitted to both ends of the developer carrying member to open a predetermined minute gap between the developer carrying member and the image carrying member in a developing area facing the image carrying member. A gap holding member, which is formed of an insulating plastic composite material containing a potassium titanate whisker that has not been electrically conductive.