JP2000112169A - Electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic device which prevents an image blur and flow in the electrophotographic device having an auxiliary electrification process and can steadily obtain high image quality at all times. SOLUTION: In an electrophotographic device in which an amount of wear per 1000 rotations of an electrophotographic photoreceptor caused in a process of clearing away transfer residual toner is 80 Å or less and an auxiliary electrification process using the same polarity as primary electrification is provided between the primary electrification and the cleaning process, toner particles used in a developing process is 100-150 in a shape factor SF-1 measured by an image analysis device and 2 wt.% or less in the amount of addition of auxiliary particles, which are present on the surfaces of the toner particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus, such as a copying machine, a laser beam printer, and a plain paper FAX, which can be widely used in electrophotographic applications.

[0002]

2. Description of the Related Art In an electrophotographic apparatus, abrasion of a photoreceptor used repeatedly occurs mainly in a step of cleaning untransferred toner. Generally, a cleaning method is used in which a plate-like elastic blade is brought into contact with the surface of the photoreceptor to scrape off the toner.

Such abrasion of the photoreceptor not only shortens the life of the photoreceptor and causes an increase in running cost, but also causes a change and deterioration in image quality due to a change in electrophotographic characteristics. Therefore, many attempts have been made to reduce wear on the surface of the photoconductor. For example, in the case of an organic photoreceptor, lubrication may be imparted to the surface, the strength of the constituent resin may be increased, and the resin may be three-dimensionally crosslinked.

On the other hand, as a charging means of an electrophotographic apparatus,
Corona charging, roller charging, needle electrode charging and the like are used, all of which involve discharge, and the generation of ionic discharge products is inevitable. When these discharge products accumulate on the surface of the photoreceptor, the surface resistance decreases, particularly in a high-humidity environment, and a so-called image flow or blur phenomenon occurs.

On the other hand, in a system where a certain amount of abrasion of the photoreceptor is allowed, the image flow can be prevented by removing the surface adhering material together with the components of the photoreceptor. In a system with a small amount of abrasion, means for improving the releasability of the photoreceptor surface to promote removal of adhered substances, and for mounting a heater on the photoreceptor to suppress lowering of the surface resistance, etc. Was used.

However, it was still insufficient. In particular, when a fine scratch is generated on the photoreceptor surface due to durability, a low-resistance discharge product attached to the groove is difficult to be removed in the cleaning process, and a streak-like image defect having a low concentration may occur in that portion. is there.

Further, in an electrophotographic apparatus of a reversal developing system in which the charging polarity in the transfer step is opposite to the primary charge, the charging ability in the next step tends to be uneven due to the influence of the transfer charge. Therefore, there is a method in which an auxiliary charging step having the same polarity as the primary charging is provided after the transfer, particularly between the cleaning step and the primary charging step, so as to cancel the influence of the reverse polarity of the transfer charging.

When such a process is used, the discharge amount further increases, and it becomes difficult to prevent the above-described image flow due to the discharge product.

[0009] Reversal development is generally used in an electrophotographic apparatus in which image input is digital, but in recent years, with the demand for higher image quality, the pixel density of digital input has increased, and 600 dp has been required.
Pixel densities of i or higher are being considered.

[0010]

In such a high-density digital image, the disturbance of the latent image in the minute low-resistance portion on the surface of the photoreceptor is more easily reproduced as an image. In particular, even if the unevenness does not appear in the image itself, the discharge product adheres to the unevenness, resulting in a streak-like image under high humidity.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electrophotographic apparatus which can prevent blur and flow of an image in an electrophotographic apparatus having an auxiliary charging step, and can always obtain a stable and high quality image.

[0012]

According to the present invention, the abrasion loss per 1000 revolutions of the electrophotographic photosensitive member generated in the step of cleaning the transfer residual toner is 80 ° or less. In an electrophotographic apparatus having an auxiliary charging process of the same polarity, the toner particles used in the developing step have a shape factor SF-1 of 100 to 100 measured by an image analyzer.
150, and the amount of auxiliary particles present on the surface of the toner particles is 2% by weight or less.

In the present invention, the amount of abrasion per 1000 rotations of the electrophotographic photosensitive member generated in the cleaning process of the transfer residual toner is 80 ° or less, and the auxiliary charging having the same polarity as the primary charging is performed between the primary charging and the cleaning process. In an electrophotographic apparatus having a process, toner particles used in a developing step have a shape factor SF-1 measured by an image analyzer of 110 <SF-1 ≦.
180, and the value of the shape factor SF-2 is 110 <SF−
2 ≦ 140, and the ratio B / A of the value B obtained by subtracting 100 from the value of SF-2 and the value A obtained by subtracting 100 from the value of SF-1
Is 1.0 or less, and the amount of auxiliary particles present on the surface of the toner particles is 2% by weight or less.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

In the prior art, as the abrasion amount of the photoreceptor is reduced, an image flow and a blur due to a discharge product are likely to occur. In particular, this phenomenon is remarkable in a digital electrophotographic apparatus having a high pixel density having an auxiliary charging step, and it has been even more difficult to prevent an image from flowing through a fine flaw caused by the durability of the photosensitive member.

As a result of intensive studies by the present inventor on this point, the toner particles used in the developing process are set to have a shape factor SF-1 of 100 to 150 measured by an image analyzer, and the auxiliary particles existing on the surface of the toner particles It has been found that by setting the addition amount to 2% by weight or less, blurring or running of an image does not occur even in a high-humidity environment.

In general, various auxiliary particles are added to a toner in order to improve fluidity, transfer property, cleaning property and the like. Specifically, for example, fine particles of silica, alumina, titanium oxide, fatty acid metal salt and the like are used. These auxiliary particles are generally smaller than the toner particles, and the effect is exhibited by being carried on the surface of the toner particles. However, in some cases, the toner particles are detached from the toner particles in the developing step and the transferring step.

The auxiliary particles are generally harder than the constituent material of the surface of the organic photoreceptor, and fine particles are generated when such detached particles are slid on the photoreceptor in the cleaning step.

On the other hand, in a general toner production method, particles are obtained by kneading components such as a resin, a colorant, and a wax, followed by pulverization and classification. The surface of such pulverized toner particles has many large and small irregularities, and the supporting force of the auxiliary particles on such a surface is not necessarily uniform, and
If the amount of the auxiliary particles is not increased more than necessary, the effect is hardly exhibited.

The shape factor SF-1 used in the present invention is 100
As a method for producing a toner having a particle diameter of 150 to 150, there is a suspension polymerization method described in JP-A-59-53856 and JP-A-59-61842.

Further, in the present invention, SF-1 is 110 <SF-1 ≦ 180, and the value of the shape factor SF-2 is as follows. 110 <SF-2 ≦ 140
And a value B obtained by subtracting 100 from the value of SF-2 and SF-
A toner in which the ratio B / A to the value A obtained by subtracting 100 from the value 1 is 1.0 or less is also used. Such a toner can be obtained by subjecting a normal pulverized toner to spheroidization by further performing a mechanical or thermal treatment.

When such substantially spherical or nearly spherical toner particles are used, the surface area is smaller than that of the pulverized toner, and the effect of the auxiliary particles can be obtained with a smaller amount.

Further, the holding power of the auxiliary particles on the surface of the toner particles is made more uniform, and the probability that free particles which are easily released and easily transferred to the photosensitive member are present is extremely small. Therefore, it has become possible to suppress the occurrence of scratches on the photoreceptor due to these auxiliary particles.

If the surface wear of the photoreceptor exceeds 80 ° per 1000 rotations of the photoreceptor, the adhered substances are removed to some extent, but the essential purposes are to improve the life of the photoreceptor, reduce the running cost, and stabilize the image quality. I can't achieve it.

In particular, in a full-color copying machine or the like in which reproducibility of a highlight density region is required, it is desirable to minimize potential fluctuation due to abrasion of the photosensitive member.

As described above, as the auxiliary particles to be added to the toner, one or more submicron particles such as silica, alumina, titanium oxide, and fatty acid metal salts are used.

It is necessary that the amount of the auxiliary particles added is 2% by weight or less. When two or more types of auxiliary particles are added, the total amount is 2% by weight or less. If the content is more than 2% by weight, even if the toner particles are substantially spherical, particles that are partly detached are likely to be present, and the particles carried on the surface of the toner particles may contact the photoreceptor. Comes up that could cause scratches.

FIG. 1 shows the configuration of an electrophotographic apparatus according to the present invention, taking a digital full-color copying machine as an example. In FIG. 1, reference numeral 1 denotes a photosensitive member which rotates in the direction of the arrow. 2 is a primary charger, 3 is input light having a digital image signal (the light source is not shown), and 4 is a developing device, here, four developing devices 4 having yellow, magenta, cyan and black toners, respectively. 1, 4-2, 4-3 and 4-4.

Reference numeral 5 denotes a transfer unit, which comprises a transfer drum 5-1 having a resin film formed in a cylindrical shape, and a transfer brush 5-2 provided in contact with a photosensitive drum facing position inside the transfer drum 5-1. The transfer of the four colors is sequentially performed on the transfer paper 6 wound on the transfer drum by the brush biased with the polarity.

The transfer residual toner is supplied to the cleaning unit 7.
It is scraped off. Reference numeral 8 denotes an auxiliary charger having the same polarity as the primary charging.

[0031]

The present invention will be described below with reference to examples.

Example 1 Photoreceptor Preparation Example: A negative-polarity photoreceptor was prepared.

A charge generation layer in which a phthalocyanine pigment having sensitivity to semiconductor laser light was dispersed in a resin, and a charge transport layer in which a triphenylamine compound was dissolved in the resin were laminated.

Further, a dispersion of polytetrafluoroethylene powder in a polycarbonate resin and a solvent was applied on the charge transport layer to form a surface layer. Polytetrafluoroethylene was 30% by weight of the entire surface layer.

A digital color copying machine (CLC700; manufactured by Canon) using a laser as a light source is prepared as an electrophotographic apparatus, and an auxiliary charger is mounted between the cleaner and the primary charger so that the same charging as the primary charging can be performed. Was remodeled.

Example of Toner Preparation: A styrene monomer, a colorant, a wax and the like were mixed in stirred water, and heated and polymerized together with a polymerization initiator to obtain a toner having an average particle diameter of 6 μm.
The shape factor SF-1 was 105 and SF-2 was 109.

1% by weight of silica fine particles was externally added thereto to obtain a toner having excellent fluidity. 6 parts by weight of this toner and a resin-coated magnetic ferrite carrier 94 having an average particle size of 50 μm
Parts by weight to prepare a two-component developer.

A durability test by continuous printing was performed using such an electrophotographic apparatus. After repeating 10,000 copies in a normal temperature and normal humidity environment, the sample was left in a 30 ° C./85% RH environment to obtain a copy sample. In each of the samples at the time, a good image equivalent to the initial state was maintained.

The amount of abrasion on the surface of the photoreceptor at this time was 60 ° per 1000 rotations of the photoreceptor.

The evaluation was performed without mounting the heater of the photoreceptor in any environment including the following examples.

Example 2 Photoreceptor Preparation Example: A negative polarity OPC photoreceptor was prepared.

A charge generation layer in which a phthalocyanine pigment sensitive to semiconductor laser light was dispersed in a resin, and a charge transport layer in which a triphenylamine compound was dissolved in the resin were laminated.

Further, as a surface layer, a material obtained by dispersing a powder of tin oxide and polytetrafluoroethylene in an acrylic monomer and a solvent is applied on the charge transporting layer, and a UV initiator is used together with a photoinitiator.
Cured to form a film. Polytetrafluoroethylene was 25% by weight of the entire surface layer.

Digital color copying machine using a laser as a light source as an electrophotographic apparatus (CLC1000; manufactured by Canon)
Was prepared.

The same toner as in Example 1 was further added with 0.7% by weight of strontium titanate fine powder externally, and a durability test was performed by continuous printing on 10,000 sheets in the same manner. Normal humidity environment, and 30
Good samples equivalent to those at the initial stage were maintained in the samples at both the temperature of 85 ° C. and the environment of 85% RH.

At this time, the amount of wear on the surface of the photosensitive member was 30 ° per 100,000 rotations of the photosensitive member.

Embodiment 3 A digital copying machine of reversal development type (GP-55; manufactured by Canon Inc.) was prepared as an electrophotographic apparatus, and an auxiliary charger was mounted between a cleaner and a primary charger to perform primary charging. Modified so that the same charge can be obtained.

As the photoreceptor, the same material as in Example 1 was used, and a film was formed on a substrate having a size corresponding to the above apparatus.

Example of Toner Preparation: The toner produced by the pulverization method is further subjected to a spheroidizing treatment to have an average particle diameter of 7 μm.
A toner having a shape factor SF-1 of 144 and an SF-2 of 126 was obtained. 1% by weight of silica fine particles was externally added thereto to obtain a toner having excellent fluidity.

Under these conditions, 10,000
A durability test was performed by continuous printing of the sheets. As a result, a good image equivalent to the initial state was maintained in the samples at both the normal temperature and normal humidity environment and the 30 ° C./85% RH environment.

At this time, the amount of wear on the surface of the photoreceptor was 70 ° per 100,000 rotations of the photoreceptor.

Comparative Example In Example 1, toner having a shape factor SF-1 of 153 and an SF-2 of 148 was used. The silica of the auxiliary particles required 2% by weight in order to impart fluidity equivalent to that of Example 1.

The other conditions were evaluated under the same conditions as in Example 1.

As a result, although there was no problem at normal temperature and normal humidity, when an image sample was taken after the apparatus was left in a 30 ° C./85% RH environment, white stripes appeared on the entire surface in a halftone image.

At this time, the amount of wear on the surface of the photosensitive member is
It was 65 ° per 10,000 rotations.

[0056]

According to the present invention as described above,
Abrasion of the photoreceptor is suppressed, and contamination of the photoreceptor surface in an electrophotographic apparatus having an auxiliary charging process having the same polarity as the primary charging between the primary charging and the cleaning process, and the resulting image blur and flow are prevented. In addition, it has become possible to provide an electrophotographic apparatus that can always obtain high image quality stably.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically illustrating a configuration example of an electrophotographic apparatus according to the present invention.

[Brief description of reference numerals]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Primary charging device 3 Input light 4 Developing device 4-1, 4-2, 4-3, 4-4 Developing machine 5 Transfer unit 5-1 Transfer drum 5-2 Transfer brush 6 Transfer paper 7 Cleaning unit 8 Auxiliary charger

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Haruka Sakami 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2H005 AA08 AA15 AA21 CB13 DA07 EA07 2H034 AA06 AA07 BA00 BF00 2H068 AA03 AA04 AA19 AA20 AA37 BA12 BA38 BB25 BB31 BB51 CA37 FA03 FA15 FA16 FB13

Claims (2)

[Claims] An abrasion loss per 1000 rotations of the electrophotographic photosensitive member caused in a cleaning process of the transfer residual toner is 80 ° or less, and an auxiliary charging process having the same polarity as the primary charging is provided between the primary charging and the cleaning process. In an electrophotographic apparatus, toner particles used in a developing process have a shape factor SF-1 of 100 to 150 measured by an image analyzer, and the amount of auxiliary particles present on the surface of the toner particles is 2% by weight or less. An electrophotographic apparatus, characterized in that: 2. An abrasion loss per 1000 revolutions of the electrophotographic photosensitive member caused in a cleaning step of the transfer residual toner is 80 ° or less, and an auxiliary charging process having the same polarity as the primary charging is provided between the primary charging and the cleaning step. In electrophotographic equipment,
The toner particles used in the developing step have a shape factor SF-1 measured by an image analyzer of 110 <SF-1 ≦ 180 and a shape factor SF-2 value of 110 <SF-2 ≦ 140.
And a value B obtained by subtracting 100 from the value of SF-2 and SF-
The ratio B / A to the value A obtained by subtracting 100 from the value of 1 is 1.0 or less, and the amount of the auxiliary particles present on the surface of the toner particles is 2% by weight or less. Electrophotographic equipment.