JP3162569B2 - Image forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method suitable for visualizing an electrostatic latent image formed on an electrostatic latent image holding member in an electrophotographic apparatus.

[0002]

2. Description of the Related Art In general, in an electrophotographic system, a photoreceptor using an optical semiconductor is first charged (charged) by corona discharge or the like, and an original image is formed thereon via an optical lens or laser. By applying a light signal by light (exposure), a potential drop corresponding to the irradiated light is caused to form a so-called electrostatic latent image. Next, the electrostatic latent image is visualized by contacting or approaching the charged toner (development), and the toner is transferred onto paper by the force of an electric field (transfer), and energy such as heat, pressure, and light is applied. A copy image is obtained by a process of fixing (fixing).

As a development process, a two-component development method using a toner and a carrier and a magnetic one-component development method using only a magnetic toner have been widely used. In recent years, a non-magnetic one-component developing method using only non-magnetic toner has been studied in order to reduce the size of the apparatus, reduce the cost, and improve the image characteristics.

In this non-magnetic one-component developing method, since the developing roller and the electrostatic latent image holding member are in contact with each other and no magnetic powder such as a carrier is used, it is difficult to stably and uniformly charge the developer. However, there has been a problem that fog of the developer, adhesion of the developer to a developing roller, an electrostatic latent image holder, a developing roller, a layer regulating member, and the like, filming, and the like are likely to occur. In addition, there is a limit to miniaturization of the entire apparatus.

For example, if an attempt is made to reduce the diameter of the electrostatic latent image holder, it is necessary to bring the electrostatic latent image holder into contact with the developing roller with high precision. This is because these contact portions also have a role of charging the toner, so that they must be in contact with a certain pressure and a certain nip in order to uniformly charge in the longitudinal direction of the roller. When the substantial diameter of the electrostatic latent image holding member is reduced to 20 mm or less, the distance between the electrostatic latent image holding member and the developing roller increases sharply when the contact portion is slightly separated from the contact portion. Is required.

In addition, if the toner particle size distribution is not sufficiently sharp, the charge amount distribution has a wide range, so that development for obtaining a high-quality image becomes difficult. Therefore, especially when the diameter of the electrostatic latent image holding member is small, the influence of the particle size distribution of the toner on the charge amount distribution becomes large, and the uniform charging can be performed even with a slight mechanical deviation between the latent image forming member and the developing roller. In order to obtain, it is necessary to sharpen the particle size distribution. In particular, when a toner having a certain average particle size is obtained, fine powder and coarse powder greatly deviating from the values have a large effect on the charge amount distribution, and therefore it is necessary to reduce the amount sufficiently.

In the case of the cleanerless process, the toner remaining on the latent image forming body after transfer is made uniform by a conductive brush or the like, but the particle size distribution has a certain width or more, and the charge amount of the particles is increased. When there is a large difference between the two, the uniformization was not sufficiently performed, and the next exposure or development step was seriously hindered. In addition, transfer methods other than corona discharge,
For example, in the case of transfer using a roller, the transfer efficiency changes depending on the width of the particle size distribution and the amount of coarse powder and fine powder.
In particular, unevenness occurred in solid and halftone portions. This phenomenon is more remarkable in the case of a color image using two or more color toners. If the particle size distribution, the average particle size, and the like of the toner of each color greatly differ, the transfer efficiency differs depending on the color at the time of transfer.
Unless the process and materials used are optimized, a desired image cannot be obtained.

[0008]

SUMMARY OF THE INVENTION According to the present invention, a developer is uniformly charged, a high-density image is obtained without fogging on an electrostatic latent image holding member. It is an object of the present invention to provide an image forming method which makes it difficult for a developer to adhere to a layer regulating member, filming, and the like, and makes it possible to reduce the size of the entire apparatus.

[0009]

According to a first aspect of the present invention, there is provided:
Supplying a developer to the outer peripheral surface of the developer carrying member to form a developer layer, and contacting the developer layer with an electrostatic latent image holding member to adhere the developer on the electrostatic latent image; Developing to a visible image.
A non-magnetic one-component developer having a volume particle size distribution in which particles having a particle diameter of 6 μm or more is less than 10% is used, and a nip width between the electrostatic latent image holding member and the developer holding member is set to 3 mm or less. An image forming method is provided.

In a second aspect of the present invention, a step of supplying a developer to an outer peripheral surface of a developer carrier to form a developer layer; and contacting the developer layer with an electrostatic latent image holding member; in single or multi-color image forming method comprising the step of developing a visible image by attaching the developer onto the electrostatic latent image, a diameter
The use of an electrostatic latent image carrier having a diameter of 20 mm or less , and the fraction of particles having a particle diameter of 70% or less of the average particle diameter D ₅₀ in the volume particle diameter distribution is 25% or less, and the average particle diameter D ₅₀
The present invention provides an image forming method characterized by using a single-color or plural-color non-magnetic one-component developer in which a fraction of particles having a particle size of 130% or more is 15% or less. . These developers can be preferably used in a cleanerless image forming apparatus.

[0011]

The present inventors have conducted intensive studies in order to obtain a clear, high-density, fog-free image. Under certain conditions, the width of the contact portion between the developing roller and the electrostatic latent image holding member ( When only the nip width is changed, the smaller the nip width, the smaller the fog, and the more difficult it is for the developer to stick to the electrostatic latent image holding member and the developing roller carrying the developer and to cause filming. I found it.

In an image forming method including a step of performing development on an electrostatic latent image using a developer carrier, when the surface of the developing roller is extremely close to the latent image surface, the surface of the electrostatic latent image carrier is Some of the electric charges may move in the developer layer due to air discharge or the like, and may reach the surface of the developing roller. That is, the charge on the surface of the electrostatic latent image holding member is removed by the developing roller, resulting in a decrease in the potential difference between the surface of the developing roller and the surface of the electrostatic latent image holding member, and this fact contributes to an increase in fog. I know. In particular, in the contact-type image forming method, it is unavoidable that the distance between the developing roller and the surface of the electrostatic latent image holding member becomes extremely narrow as the contact portion is approached, and the air discharge can occur when the interval is extremely small even at a low voltage. Therefore, it is desirable that the surfaces except for the contact portion between the developing roller and the electrostatic latent image holding member are separated as much as possible. Therefore, it is preferable that the diameters of both are smaller, and the smaller the diameter of both, the smaller the nip width and the more precisely the nip width can be controlled.

From the above, in the first aspect of the present invention, the nip width is 3 mm or less, and practically preferably 0.5 mm or more. further,
If a large amount of coarse powder is contained in the developer used at this time, the coarse powder prevents a medium-sized or small-sized particle from uniformly contacting the charging member. The charge of the developer is also likely to be non-uniform, and the amount of the oppositely charged developer is also increased. For this reason, fog increases, and the above-mentioned effects cannot be utilized to the maximum. Therefore, in the volume particle size distribution of the developer, it is desirable that the coarse powder having a size of 16 μm or more has a volume distribution of less than 10%. Here, the reason why the coarse powder having a particle diameter of 16 μm or more is that if the particle diameter of the developer is unnecessarily large, the resolution of an image is reduced, or an image bleeds, etc.
This is because it is considered that a material having a size of about 13 μm is used. Fine powder having a particle size of 4 μm or less also tends to cause fogging, toner scattering, and the like, and therefore, is preferably 3% or less in practical use.

In this image forming method, when the diameter D ₁ of the electrostatic latent image holding member is 20 mmφ or less, the above-described effect of preventing air discharge is high, and a good image can be obtained. However, in consideration of the strength and the like, the diameter D ₁ is preferably 5 mmφ or more. Further, the diameter D ₂ of the developing roller with respect to the diameter D ₁ of the electrostatic latent image holding member is too large, it becomes difficult to reduce and precisely control the nip width, too small an elastic developing roller Of the image becomes large, and the quality of the image is rather deteriorated. Therefore, in order to improve the image quality most effectively, D ₁
It is desirable to satisfy ≦ 20 (mmφ) and 0.5 <D ₂ / D ₁ <2. Here, any developing roller may be used as long as it is an elastic roller having conductivity.As the electrostatic latent image holder, inorganic photoconductors such as selenium and amorphous silicon, various organic photoconductors, etc. Any device that can perform image exposure and form a latent image may be used. Also,
The development method may be either a normal development method for forming an image on a non-exposed part or a reversal development method for forming an image on an exposed part,
The charge polarity of the developer may be either positive or negative.

In the second aspect of the present invention, when the substantial diameter of the latent image forming body is as small as 20 mmφ or less, the latent image forming body and the charge amount distribution are further controlled by controlling the particle size distribution and charge amount distribution of the developer. We succeeded in obtaining a uniform charge even for a slight mechanical deviation of the developing roller. In other words, when obtaining a developer having a sharper particle size distribution, and particularly obtaining a developer having a certain average particle size, fine powder and coarse powder greatly deviating from the values are subjected to charge amount distribution and other processes (transfer process using a roller, cleaning using a brush). Since the influence of the latent image forming member on the latent image forming member is as small as 20 mmφ or less, a high-quality image can be obtained by sufficiently reducing the amount thereof.

Further, in a color image forming apparatus using two or more color toners, if the particle size distribution and the charge amount distribution of each color are largely different, the cleaning property is different depending on the color and the transfer efficiency is different, so that the image quality is deteriorated. Tends to occur. This difference in transferability due to color is particularly remarkable in the case of roller transfer. Such a difference in transfer efficiency is caused not only by a method in which all colors are transferred at once, but also by a method in which each color is sequentially transferred, such as changing the roller material and setting transfer conditions for each color. Need to have a significant effect on process and image quality. In contrast, the average particle diameter D ₅₀ of the second mean particle diameter D ₅₀ of the largest becomes the developer in the developer according to the aspect of the r _1, smallest becomes the developer of the present invention
When was the r _2, the ratio r ₁ / r ₂ is ₁ ≦ r 1 / r ₂
When used under the condition of ≦ 1.2, these problems can be solved.

[0017]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited by these examples. The voltage conditions during development were all constant, and the potential difference between the white background on the surface of the electrostatic latent image holding member and the surface of the developing roller was 300 (V).

FIG. 1 is a diagram showing a configuration of a main part of an example of an image forming apparatus to which the method of the present invention can be applied. As shown in FIG. 1, the apparatus includes a developer container 1 as a developing device, a developer 2 stored in the developer container 1,
A stirrer 3 for stirring the developer 2, a developer supply roller 4 for transporting the stirred developer 2, and a developing roller 5 for carrying a predetermined amount of the developer 2 transported by the developer supply roller 4; Is provided. In the developing roller 5, the transported developer 2 passes through the developer layer thickness regulating member 6, is thinned and held on the surface of the developing roller 5, and at the same time, has a prescribed charge. The developer carried on the surface of the developing roller 5 in this manner is
An electrostatic latent image formed on a latent image holding member 7 provided in contact with the developing roller 5 with a nip width of 3 mm or less is developed using an electric field. On the electrostatic latent image holder 7, the developing roller 5, a charger 9 for uniformly charging the electrostatic latent image holder 7, and an electrostatic latent image holder 7 charged by the charger 9 are provided. Exposing device 8 for exposing the image according to an image signal, a transfer device 11 for transferring a developed image to a material to be transferred (not shown), and a developer 2 remaining on the electrostatic holding member without being transferred And a cleaning unit 10 for collecting the toner.

Hereinafter, Examples 1 to 4 and Comparative Examples 1 to 7, which were carried out with respect to the first embodiment of the present invention, using the apparatus having the above-described configuration, will be described. Example 1 In the developing device of the image forming apparatus shown in FIG. 1, an organic photoreceptor having a diameter of 20 mm and a conductive urethane roller having a diameter of 10 mm were used, and the nip width was adjusted to 0.5 mm. The charge polarity of the photoreceptor was negative, and the developer was also of the same polarity and a reversal development method was employed. When the particle size distribution of the developer used was measured by a Coulter counter, the volume average particle size was 8.6 μm, and the volume average particle size was 16 μm.
The above coarse powder was 3% of the whole. As a result of the image output, the image was a clear line image, a solid image, and a uniform high-density (1.40 by Macbeth densitometer) fog-free image. In addition, even after outputting 10,000 sheets of the test chart having a printing rate of 5%, the image was a clear image without deterioration while maintaining the initial state. Example 2 In the developing device of the image forming apparatus shown in FIG. 1, an organic photoreceptor having a diameter of 18 mm and a conductive urethane roller having a diameter of 18 mm were used, and the nip width was adjusted to 0.5 mm. The charge polarity of the photoreceptor was negative, and the developer was also of the same polarity and a reversal development method was employed. When the particle size distribution of the developer used was measured by a Coulter counter, the volume average particle size was 6.8 μm, and the volume average particle size distribution was 16 μm.
The above coarse powder was 0.5% of the whole. As a result of the image output, the image was a clear line image, a uniform solid image, and a high-density (1.35 by Macbeth densitometer) fog-free image. In addition, even after outputting 10,000 sheets of the test chart having a printing rate of 5%, the image was a clear image without deterioration while maintaining the initial state. Example 3 In the developing device of the image forming apparatus shown in FIG. 1, the nip width was adjusted to 0.5 mm using an organic photoreceptor having a diameter of 10 mm and a conductive urethane roller having a diameter of 18 mm. The charge polarity of the photoreceptor was negative, and the developer was also of the same polarity and a reversal development method was employed. When the particle size distribution of the developer used was measured by a Coulter counter, the volume average particle size was 7.5 μm, and the volume average distribution was 16 μm.
The above coarse powder was 7% of the whole. As a result of the image output, the image was a clear line image, a uniform solid image, and a uniform high-density (1.38 by Macbeth densitometer) fog-free image. In addition, even after outputting 10,000 sheets of the test chart having a printing rate of 5%, the image was a clear image without deterioration while maintaining the initial state. Example 4 In the developing device of the image forming apparatus shown in FIG. 1, an organic photoreceptor having a diameter of 10 mm and a conductive urethane roller having a diameter of 5 mm were used, and the nip width was adjusted to 0.5 mm. The charging polarity of the photoreceptor was positive, and the developer was also of the same polarity and a reversal developing method was employed. When the volume particle size distribution of the developer used was measured by a Coulter counter, the volume average particle size was 7.0 μm, and the volume average particle size was 16 μm.
m or more was 0.2% of the whole. As a result of the image output, the image was a clear line image, a uniform solid image, and a high-density (1.42 by Macbeth densitometer) fog-free image. In addition, even after outputting 10,000 sheets of the test chart having a printing rate of 5%, the image was a clear image without deterioration while maintaining the initial state. Comparative Example 1 In the developing device of the image forming apparatus shown in FIG. 1, the nip width was adjusted to 3.5 mm using an organic photoreceptor having a diameter of 30 mm and a conductive urethane roller having a diameter of 18 mm. The charge polarity of the photoreceptor was negative, and the developer was also of the same polarity and a reversal development method was employed. When the particle size distribution of the developer used was measured by a Coulter counter, the volume average particle size was 7.8 μm, and the coarse powder having a volume particle size distribution of 16 μm or more was 5% of the whole. As a result of the image output, the line image was clear and the solid image was also high density (1.
35), but the image was somewhat non-uniform and extremely fogged. Further, after 1,000 sheets of the test chart with the printing rate of 5% were output, the image was considerably deteriorated as compared with the initial stage. Comparative Example 2 In the developing device of the image forming apparatus shown in FIG. 1, the nip width was adjusted to 3.5 mm using an organic photoreceptor having a diameter of 20 mm and a conductive urethane roller having a diameter of 10 mm. The charge polarity of the photoreceptor was negative, and the developer was also of the same polarity and a reversal development method was employed. When the particle size distribution of the developer used was measured by a Coulter counter, the volume average particle size was 7.8 μm, and coarse powder having a size of 16 μm or more was 5% of the whole. As a result of the image output, a clear line image and a uniform high density of a solid image (with a Macbeth densitometer of 1.3)
5), but the image was slightly uneven and had much fog. Further, after output of 1,000 test charts with a printing ratio of 5%, considerable image deterioration was observed as compared with the initial stage. Comparative Example 3 In the developing device of the image forming apparatus shown in FIG. 1, a nip width was adjusted to 0.5 mm using an organic photoreceptor having a diameter of 30 mm and a conductive urethane roller having a diameter of 18 mm. The charge polarity of the photoreceptor was negative, and the developer was also of the same polarity and a reversal development method was employed. When the particle size distribution of the developer used was measured by a Coulter counter, the volume average particle size was 7.8 μm, and the volume average particle size distribution was 16 (μm).
The coarse powder of m) or more was 5% of the whole. As a result of the image output, the line image was clear and the solid image was high in density (1.32 by Macbeth densitometer). However, the image was slightly uneven and had much fog. Further, when 1,000 sheets of a test chart having a printing rate of 5% were output, a sharp deterioration of the image was observed. Comparative Example 4 In the developing device of the image forming apparatus shown in FIG. 1, an organic photoreceptor having a diameter of 30 mmφ and a conductive urethane roller having a diameter of 18 mmφ were prepared, and the nip width was adjusted to 0.5 mm. The charge polarity of the photoreceptor was negative, and the developer was also of the same polarity and a reversal development method was employed. When the particle size distribution of the developer used was measured by a Coulter counter, the volume average particle size was 8.5 μm, and the volume average particle size was 16 μm.
The above coarse powder was 15% of the whole. As a result of the image output, although the line image was clear, the image had a low solid image density (1.02 by Macbeth densitometer) and a lot of fog. Comparative Example 5 In the developing device of the image forming apparatus shown in FIG. 1, an organic photoreceptor having a diameter of 10 mm and a conductive urethane roller having a diameter of 25 mm were used, and the nip width was adjusted to 0.5 mm. The charging polarity of the photoreceptor was negative, and the developer had the same polarity, and a reversal developing method was adopted. When the particle size distribution of the developer used was measured by a Coulter counter, the volume average particle size was 8.5 μm, and coarse powder having a size of 16 μm or more was 3% of the whole. As a result of the image output, the solid image had the developer spilled, and the image was extremely fogged. Comparative Example 6 In the developing device of the image forming apparatus shown in FIG. 1, the nip width was adjusted to 0.5 mm using an organic photoreceptor having a diameter of 20 mm and a conductive urethane roller having a diameter of 5 mm. The charging polarity of the photoreceptor was negative, and the developer had the same polarity, and a reversal developing method was adopted. When the particle size distribution of the developer used was measured by a Coulter counter, the volume average particle size was 8.5 μm, and the amount of coarse powder having a size of 16 μm or more was 0.5% of the whole. As a result of image output, the solid image density was low (0.98 as measured by Macbeth densitometer), and the image had a lot of fog. Comparative Example 7 In the developing device of the image forming apparatus shown in FIG.
An organic photoreceptor having a diameter of 8 mm and a conductive urethane roller having a diameter of 10 mm were prepared, and the nip width was adjusted to 0.5 mm. The charging polarity of the photoreceptor was negative, and the developer had the same polarity, and a reversal developing method was adopted. When the particle size distribution of the developer used was measured by a Coulter counter, the volume average particle size was 10.5 μm, and coarse powder having a volume average particle size of 16 μm or more was 20% of the whole. As a result of the image output, the line image was clear, the solid image was high in density (1.40 by Macbeth densitometer), the fog was small, but after outputting 10,000 sheets of a test chart with a printing rate of 5%, the image was slightly lower than the initial one. Deterioration was observed.

As described above, based on the embodiment described above,
The developer is uniformly charged, and a high-density image is obtained without fogging on the electrostatic latent image holding member. The developer is fixed to the electrostatic latent image holding member, the developing roller, the layer regulating member, and filming. In order to provide an image forming method that makes it difficult to generate an image, and enables miniaturization of the entire apparatus, the nip width between the electrostatic latent image holding member and the developing roller is 3 mm or less, and the particle size of the developer used is In the distribution, it is desirable that the coarse powder having a particle size of 16 (μm) or more is less than 10% in a volume distribution. Further, the ratio of the diameter D _{1 of the} electrostatic latent image holding member to the diameter D ₂ of the developing roller is 20 mmφ or less. It is understood that it is desirable that D ₂ / D ₁ is 0.5 <D ₂ / D ₁ <2. Example 5 Alcohol-soluble nylon is formed as an adhesive layer on an aluminum drum having a diameter of 19.95 mmφ to a thickness of 0.6 μm. And a charge generation layer thereon. Then, a coating liquid in which Y-type tititanyl phthalocyanine and polypinyl bral were dispersed in toluene at a weight ratio of 1 to 1 was provided so as to have a film thickness of 0.2 μm. Further, a hydrazone compound and a bisphenol z-type polycarbonate were dispersed thereon in 1,1,2-trichloroethane at a weight ratio of 1 to 1 to provide a coating having a thickness of 20 μm.

Using this as a latent image holding member, a prototype of a laser beam printer capable of outputting four images per minute in A4 size was produced. This was subjected to one-component non-magnetic development using a black developer containing polyester as a binder resin.

The particle size distribution of the black developer was measured with a Coulter Multisizer (manufactured by Nikkaki Co., Ltd.), and the volume average particle size D ₅₀ =
7.5 μm, not more than 5.0 μm by volume distribution, 12.2%,
10% or more and 8.1% were obtained. The latent image holding member was charged to −500 V using a scorotron, and a roller was used for transfer.

The cleaning was performed using a cleaning blade. The fogging of the image output in the above process was measured using a Minolta CR-121 colorimeter. That is, the difference (%) between the reflectance of the white background portion of the output image and the reflectance of the virgin paper not passing through the machine was defined as fog. As for the image defect, the image density is output as a solid black solid with an image density of 1.3 or more.
Defects other than the defect based on the photoreceptor were counted. As a result, an extremely good image having a fog of 1.1% and an image defect of 0 was obtained. Also, when the character image was output, no beating was recognized. Example 6 A single-layer type positive photosensitive organic photoreceptor made of phthalocyanine, perylene, hydrazone derivative, and polycarbonate was used as a latent image holding member on a 19.95 mm diameter aluminum drum. A prototype laser beam printer was developed. This was subjected to one-component non-magnetic development using a black developer using a styrene-acryl copolymer as a binder resin.

The particle size distribution of the black developer was measured with a Coulter Multisizer (manufactured by Nikkaki Co., Ltd.), and the volume average particle size D _{50 was} measured.
= 8.3 μm, 5.8 μm or less 10.1 in volume distribution
%, 10.8 μm or more and 12.1%. The latent image carrier was charged to +500 V using a scorotron, and a roller was used for transfer. Cleaning was performed using a cleaning blade. The image output by the above process had an extremely good fog of 1.2% and no image defects. Also, when the character image was output, no beating was recognized. Example 7 Using the same organic photoconductor as in Example 1 as a latent image holding member, a laser beam printer capable of outputting four images per minute in A4 size was prototyped. This was subjected to one-component non-magnetic development using a black developer containing polyester as a binder resin.

The particle size distribution of the black developer was measured with a Coulter Multisizer (manufactured by Nikkaki Co., Ltd.), and the volume average particle size D _{50 was} measured.
= 7.5 μm, 5.3 μm or less in volume distribution 12.2
%, 9.8 μm or more and 10.1%. The charging of the latent image holding member is performed by using a scorotron so as to become -500 V,
The transfer was performed using a roller. For cleaning, a so-called cleaner-less method using a conductive brush without using a cleaning blade was employed.

The image output by the above process had an extremely good fog of 0.3% and no image defects. In addition, when a character image was output, no overtone was recognized. Example 8 The same organic conductor as in Example 5 was used as a latent image holding member,
A prototype of a color laser beam printer capable of outputting four color images per minute in A4 size was produced. This printer is a so-called tandem type color printer in which developers of respective colors of yellow, magenta, cyan, and black are sequentially developed and transferred to paper or the like each time. This apparatus has a latent image forming, developing step, and transferring step for each color. For each color, one-component non-magnetic development was performed using a developer (yellow, magenta, cyan, black) using polyester as a binder resin.

The particle size distribution of each developer was measured with a Coulter Multisizer (manufactured by Nikkaki), and the following results were obtained. Yellow has a volume average particle diameter D ₅₀ = 7.8 μm and a volume distribution of 5.5 μm or less 10.1% and 10.1 μm or more 9.8%. Magenta has a volume average particle diameter D ₅₀ = 7.5 μm,
In a volume distribution, 5.3 μm or less and 12.2%, and 9.8 μm or more and 10.1%. 11.9%. Cyan has a volume average particle diameter D ₅₀
= 8.3 µm, 5.8 µm or less 8.7% by volume distribution,
10.8 μm or more and 13.1%. Black has a volume average particle diameter D ₅₀ = 8.1 μm and a volume distribution of 5.7 μm or less 8.9.
%, 10.5 μm or more and 11.9%. 1 the ratio of the average particle diameter D ₅₀ of each developer most different (cyan / magenta).
It was 11. The latent image holding member was charged to −500 V using a scorotron, and an elastic roller was used for transfer. Cleaning was performed using a cleaning blade.

The evaluation of the full-color image output by the above process was performed as follows. 10m width on the short side of A4
m, a solid image is output in the order of yellow, cyan, magenta, black, red, breen, and blue at an interval of 10 mm. At that time, the reproducibility of each color, the fog of the non-image portion, and the image defect were measured. As a result, the fog was 0.9% or less at all places, and the image defect was 0, which was extremely good. Further, the image was an extremely high-quality image having good color reproducibility. In addition, when character images were output in all colors, no overtones were recognized. Example 9 In a process similar to that of Example 8, a so-called cleanerless method was adopted in which only a cleaning was performed without using a cleaning blade and a conductive brush was used. When a full-color image similar to that of Example 8 was output by the above process, the fog was 0.5% or less at all locations and the image defect was 0, which was extremely good. Further, the image was an extremely high-quality image having good color reproducibility. Also, if you output character images in all colors,
No bet was found. Example 10 The same process and the same developer as in Example 9 were used to charge the latent image holding member, instead of corona charging using a scorotron, but by bringing a conductive elastic roller into contact with the latent image holding member while rotating the latent image holding member. A roller charging method was used in which a DC bias voltage was applied to the roller to charge the latent image holding member. The bias voltage was adjusted so that the surface potential of the latent image holding member was -500 V for each color. When a full-color image similar to that of Example 4 was output by the above process, the fog was 0.6% or less at all places and the image defect was 0, which was extremely good. Further, the image was an extremely high-quality image having good color reproducibility. Comparative Example 8 The diameter of an aluminum drum serving as a conductive support was 25 m.
A laser beam printer capable of outputting an image of four sheets per minute in A4 size was produced by using the same organic conductor as in Example 1 except for mφ as the latent image holder. This was subjected to one-component non-magnetic development using a black developer containing polyester as a binder resin.

The particle size distribution of the black developer was measured with a Coulter Multisizer (manufactured by Nikkaki Co., Ltd.), and the volume average particle size D _{50 was} measured.
= 7.5 μm, 5.3 μm or less in volume distribution 12.2
%, 9.8 μm or more and 10.1%. The charging of the latent image holding member is performed by using a scorotron so as to become -500 V,
The transfer was performed using a roller. Cleaning was performed using a cleaning blade. In the image output by the above process, fog was 5.5%, and 12 solid image defects were recognized. In addition, part of the character image was recognized. Comparative Example 9 Using the same organic photoconductor as Comparative Example 8 as a latent image holding member, a laser beam printer capable of outputting an image of four sheets per minute in A4 size was prototyped. This was subjected to one-component non-magnetic development using a black developer containing polyester as a binder resin. The particle size distribution of the black developer was measured with a Coulter Multisizer (manufactured by Nikkaki Co., Ltd.), and the volume average particle size D _{50 was} 7.8 μm.
m, 5.5 μm or less in volume distribution 21.5%, 10.1
A value of 16.1% or more was obtained. The latent image holding member was charged to -500 V using Scotroton, and a roller was used for transfer. Cleaning was performed using a cleaning blade. In the image output in the above process, the image output in the above process was found to have a fog of 6.2% and 10 solid image defects. In addition, the solid image had a defect, and the character image was fuzzy. Comparative Example 10 A color laser beam printer capable of outputting four color images per minute in A4 size was prototyped using the same organic photoconductor as in Comparative Example 8 as a latent image carrier. This printer is a so-called tandem type color printer in which developers of respective colors of yellow, magenta, cyan, and black are sequentially developed and transferred to paper or the like each time. Therefore, a latent image formation, development step, and transfer step are provided for each color. For each color, a developer using polyester as a binder resin (yellow, magenta, cyan,
Black) was used for one-component non-magnetic development. The particle size distribution of each developer was measured with a Coulter Multisizer (manufactured by Nikkaki), and the following results were obtained. Yellow has a volume average particle size D ₅₀ = 7.8 μm and a volume distribution of 5.5 μm or less 10.1% and 10.1 μm or more 9.8%. Magenta has a volume average particle diameter D ₅₀ = 8.1 μm and a volume distribution of 5.7% or less 8.9% and 10.5 μm or more 11.9.
%, Cyan has a volume average particle diameter D ₅₀ = 8.3 μm, and the volume distribution is 5.8% to 8.7%, 10.8 μm to 13.
1%. Black has a volume average particle size D ₅₀ = 7.5 μm, a volume distribution of 5.3 μm to 12.2%, and 9.8 μm to 1
0.1%, the ratio of the average particle diameter D ₅₀ of the developing agent was 1.11 in the most different (cyan / black). The latent image holding member was charged to −500 V using a scorotron, and an elastic roller was used for transfer. Cleaning was performed using a cleaning blade. When a full-color image similar to that of the fourth embodiment is output by the above process, fog is as high as 6.5% at the maximum, 4.8% at the minimum, and 1 image defect.
Five were found. In addition, when a character image was output, a part of the image was recognized. Comparative Example 11 An organic photoconductor similar to that of Example 5 was used as a latent image holder, and a color laser beam printer capable of outputting four color images per minute in A4 size was prototyped. This printer is a so-called tandem type color printer in which developers of respective colors of yellow, magenta, cyan, and black are sequentially developed and transferred to paper or the like each time. Therefore, a latent image formation, development step, and transfer step are provided for each color. For each color, one-component non-magnetic development was performed using a developer (yellow, magenta, cyan, black) using polyester as a binder resin. The particle size distribution of each developer was measured with a Coulter Multisizer (manufactured by Nikkaki), and the following results were obtained. Yellow has a volume average particle size D ₅₀ = 7.8 μm and a volume distribution of 5.
5 μm, below 10.1%, 10.1 μm to 9.8%, magenta: volume average particle diameter D ₅₀ = 5.9 μm, volume distribution 4.1 μm to 22.5%, 7.7 μm to 8.1 %,
Cyan has a volume average particle diameter D ₅₀ = 9.3 μm, and a volume distribution of 6.5% to 8.7%, 12.1 μm to 18.3.
%. Black has a volume average particle diameter D ₅₀ = 8.1 μm and a volume distribution of 5.7% to 8.9%, 10.5 μm to 1
1.9%.

The ratio of the average particle diameter D ₅₀ of each developer was 1.58 in cyan / magenta. The latent image holding member was charged to −500 V using a scorotron, and an elastic roller was used for transfer. Cleaning was performed using a cleaning blade. The full-color image output by the above process had many fogs, image defects, and poor color reproducibility.

Hereinafter, an image forming apparatus usable in the present invention will be described in more detail. When a latent image holding member usable in the present invention forms a latent image by light, selenium-based alloys such as selenium, selenium hyso, selenium tellurium, selenium hystellurium, CdS, CdSe, CdSSe, Zn
Inorganic photoconductors such as O or amorphous silicon, and various types of organic photoconductors called OPCs (single-layer type or stacked type) may be used. Anything that can form is acceptable. Various types of OPC are known, and a single-layer photoreceptor is prepared by mixing a charge generating material, a charge transporting material, and a binder resin.

At this time, various crystal forms (α, β, γ, and phthalocyanine pigments such as metal-free phthalocyanine, titanyl phthalocyanine, vanadyl phthalocyanine, and copper phthalocyanine aluminum chlorophthalocyanine are used as the charge generating material.
δ, ε, ζ, η, θ, ι, κ, λ, μ, ν, ξ, ο,
π, ρ, σ, τ, υ, φ, χ, ψ, ω, A, B, C, Y
Azo dyes and pigments such as monoazo, disazo, trisazo and tetrakisazo, perylene dyes and pigments such as perylene anhydride or perylene imide, perinone dyes and pigments, indigo dyes and pigments, quinacridone dyes and the like. Pigments, anthraquinones,
Polycyclic quinone dyes and pigments such as dibromoanthanthrone, cyanine dyes and pigments, xanthene dyes and pigments, pyrylium, eutectic complexes consisting of thiapyrylium dyes and polycarbonate resin, azulhenium dyes,
Examples include a squarylium dye and a charge transfer complex of an electron-donating substance and an electron-accepting substance.

The charge transport materials include hydrazone compounds, pyrazoline compounds, oxazole compounds, oxadiazole compounds, thiazole compounds, thiadiazole compounds, imino compounds, ketazine compounds, enamine compounds, amidine compounds, stilbene compounds, butadiene compounds, carbazole compounds and Polymer compounds in which these are introduced into the main chain or side chain of the polymer can be mentioned. The thickness of the single-layer type photoreceptor is appropriately determined according to the performance required for the photoreceptor, but is usually 2 to 25 μm.

The laminate type photoreceptor comprises a charge generating material and a charge transporting material separately. The charge generating material is obtained by dispersing the above compound in a binder resin such as polypinyl butyral resin and phenoxy resin, and applying various coating methods such as spin coating, dip coating, pulling method, roller coating, doctor blade coating, spray coating, and vacuum deposition. Method, sputtering method, or glow discharge, for example, plasma CVD method or the like can be appropriately selected and adopted. The thickness of the charge generation layer is appropriately determined according to the performance required for the photoreceptor, but is usually 0.1 to 2 μm.

Further, when the charge transporting substance does not have a film-forming property, the charge transporting layer may be prepared by dissolving or dispersing the following binder resin and the charge transporting substance in an appropriate solvent, and applying this solution. Prepare by drying. Known binder resins for electrophotographic photoreceptors include polycarbonate, polyester, polyester carbonate, polyvinyl chloride, acrylic resin, vinyl chloride-vinyl acetate copolymer, polyvinyl acetal, phenolic resin, and polyarylate. Can be mentioned. In this case, it is preferable to mix the polymer compound in the range of 0.3 to 2 parts by weight with respect to 1 part by weight of the charge transporting substance. Solvents include aliphatic chlorine, aromatic hydrocarbon, aromatic chlorine, ether,
Examples thereof include ester-based and ketone-based organic solvents. Various coating methods such as spin coating, dip coating, pull-up method, roller coating, doctor blade coating, and spray coating can be used as the coating method. The thickness of the charge transport layer is usually preferably from 10 to 30 μm.

Such an organic or inorganic photoconductor is usually formed on a conductive support, and may be any known and commonly used conductive support for photoconductors.
Metal materials such as aluminum, brass, iron, stainless steel,
Examples of the resin include a resin having conductivity. When the photoconductive layer is provided on the conductive support, an adhesive layer may be provided as necessary. The adhesive layer can be appropriately selected from known resins such as casein and nylon, and preferably has a thickness in the range of 0.1 to 5 μm.

The developing method includes a reversal developing method in which the developer adheres to a portion where the potential is decreased by light irradiation, and a normal developing method in which the developer adheres to a portion where the potential is maintained without being irradiated with the light. Although there are methods, the present invention is not limited to either of them. The surface potential is not limited to either positive or negative, and may be selected depending on the photoconductor used. Further, as means for irradiating light, laser, LED, E
L, a solid head such as a phosphor, or a bulb such as halogen can be used. Further, a latent image forming method of an ion deposition method in which a potential difference is formed by ion flow using a dielectric instead of the photoreceptor can also be used.

When a latent image is formed by a potential difference, the latent image holding member is charged to a certain potential using a corona discharge or a charging roller, a charging brush or the like, and the potential such as light is changed there to change the latent image. However, the smaller the diameter of the latent image holding member, the more likely the charging becomes uneven.
It is remarkable at 0 mmφ or less. This is for the same reason as the rapid change in distance during the development process. Such non-uniform charging results in image quality deterioration such as increased image fog. Therefore, if the particle size distribution and charge amount distribution of the developer are as narrow as possible, the influence is less likely to occur. The material used for the charging roller, charging brush, and charging roller brush may be any material as long as it has conductivity and can charge the latent image holding member to a certain potential. For brushes, such as resin and elastomer, which are provided with, it is possible to use metal, carbon fiber, and other materials that have conductivity by themselves, as well as fibrous materials that are made by compounding a conductive filler with resin. it can. The roller does not need to have a single-layer structure, and a laminate of two or more layers may be used in order to obtain desired performance.
As the bias to be applied, any one of AC, DC, and DC with AC superimposed may be used.

The developer carrier used here may be any material as long as it has conductivity and can apply a certain bias voltage to the developer. For example, metal rigid bodies, conductive resins, and conductive elastomers with low elastic modulus are also used.These are not used in a single-layer structure, but are plated with metal to modify the surface. Or coating with a conductive paint. As the bias to be applied, any one of AC, DC, and DC with AC superimposed may be used.

The latent image carrier and the developer carrier are generally rotated in opposite directions. Since the ratio of the rotation speed at this time depends on these diameters, it is usually expressed by a peripheral speed ratio, but this is not particularly limited unless it is 1: 1.
4: 1 (except 1: 1).

The developer carrier and the developer supply roller are rotated in the same direction, and the peripheral speed ratio is suitably in the range of 0.1: 1 to 10: 1. A bias voltage may be applied to the developer supply roller. The potential of the bias voltage varies depending on the bias of the developer carrier and the characteristics of the developer. In this case, the potential value becomes larger than the potential of the developer carrying member). The bias may be DC, AC, or DC plus AC. As the material of the developer supply roller, a foamed polyurethane elastomer having conductivity to which a bias can be applied, another conductive elastomer, a metal-coated rubber roller, or a general rubber roller may be used in some cases.

In order to form a uniform developer layer on the developer carrier, a blade or the like for forming the developer layer is required, and the shape, material, attachment portion, etc. thereof can be applied to the development process. Anything is fine. For example, the material of the developer forming blade may be a silicone resin or an elastomer that is easily charged positively if the developer is negatively charged, and may be negatively charged if the developer is positively charged. It is recommended to use a fluorine-based resin or an elastomer which is easily charged. However, since the chargeability differs depending on the binder resin, pigment, CCA and the like of the developer, it is necessary to select an optimum material in an actual system.

As a cleaning method, there are a method using a cleaning blade and a so-called cleaner-less method for cleaning using a cleaning brush. When using a cleaning blade, it is pressed against the developer carrier, but as a method,
A method of pressing only with the weight of the cleaning blade itself, a method of applying weight using an elastic body such as a spring, or the like can be used. In the case of pressing with its own weight, the blade can be used integrally with a heavy object such as a metal. In the case of the cleaner-less method, if the particle size distribution of the developer is wide and the charge amount is distributed, it is difficult to perform cleaning with such a cleaning brush. Therefore, the present invention is effective for a cleanerless process. For this cleaning brush, a conductive fibrous substance is appropriate, and in addition to a substance that is conductive itself such as metal and carbon fiber,
A fibrous material obtained by combining a conductive filler with a resin or the like can be used. In addition to the shape of the brush, a brush-like roller in which the fibrous material is fixed radially to a rotating shaft is also effective. The bias to be applied may be any one of AC, DC, and DC with AC superimposed, as long as the developer can be made uniform.

When a developer image developed on a latent image holding member is transferred onto paper or the like, the influence of corona discharge is relatively small.
In some cases, the particle size distribution is so large that uniform transfer cannot be performed. The present invention is particularly effective for a roller transfer system, and the effect becomes extremely remarkable when the diameter of the transfer roller is 15 mm or less. The material of the transfer roller is not particularly limited. The elastic modulus and hardness are not limited, and when applying a bias, any of AC, DC, and DC in which AC is superimposed may be used.

The developer transferred to paper or the like is subjected to heat, pressure,
Alternatively, it is fixed by a chemical change. In the case of heat fixing, a heater (xenon lamp, xenon lamp,
A method using a heater made of metal such as nichrome or Kanthal) or a method of applying heat to the developer portion on demand may be used.

In a color type electrophotographic apparatus using two or more colors of developer, if the particle size distribution and charge amount distribution of each color are significantly different, the cleaning performance differs depending on the color, and the transfer efficiency is different, so that the image quality deteriorates. Has occurred.
This difference in transferability due to color is particularly remarkable in the case of roller transfer. Such a difference in transfer efficiency is caused not only by a method in which all colors are transferred at once, but also by a method in which each color is sequentially transferred, such as changing the roller material and setting transfer conditions for each color. Need to have a significant effect on process and image quality. Therefore, the developer according to the present invention can also solve these problems.

The material of the developer usable in the present invention is as follows.
Any material can be used as long as it is used for a normal non-magnetic one-component developer. For example, as a coloring agent used in such a developer, carbon black, Fast Yellow G,
Benzidine Yellow, Pigment Yellow, India First, Orange, Irgazine Red, Carmine FB,
Permanent Bordeaux FFR, Pigment Orange R,
Lisor Red 2G, Rake Red C, Rhodamine F
Known colorants such as B, rhodamine B lake, phthalocyanine blue, pigment blue, brilliant green B, phthalocyanine green, and quinacridone can be used.

Examples of the binder include styrene and its copolymers, epoxy resins, polyester resins and their copolymers (unsaturated polyesters), acrylate and methacrylate resins and their copolymers, polyolefins and their copolymers Fluorinated resin, polyamide, polyurethane resin and the like.

Other additives include a charge control agent, wax, silica and the like. These are selected from known substances according to the requirements in terms of counter electrode properties and process, and are added at an appropriate mixing ratio.

Examples of the charge controlling agent include quaternary ammonium salts (including polymers) for positive charging, dyes such as nigrosine, alkylamides, and alkoxy amines. For negative charging, various metal complexes such as metal complexes of monoazo dyes and their salts, metal salts of fatty acids, resin acid soaps and the like can be mentioned.

Examples of the wax include polyolefin, carbana wax, ester wax, amide wax and the like. The charge control agent and the wax,
It is generally added as a so-called internal additive which is added simultaneously with kneading the resin, but it is also effective as a so-called external additive which is mixed with the developer powder.
Usually, they are added in the range of 0.1 to 20% by weight.
As the silica, those having various surface treatments of 10 to 50 nm are generally used, and are usually used as a so-called additive which is mixed with 0.2 to 5% by weight of a developer, but can also be used as an internal additive. . In addition to silica, 0.1 to 20% by weight of particles of a developer having an average particle diameter of about 10 to 80% (including organic substances such as resin and inorganic substances such as lead titania zirconate) may be added. it can.

[0052]

According to the present invention, the developer is uniformly charged, a high-density image without fog on the electrostatic latent image holding member can be obtained, and the electrostatic latent image holding member, the developer holding member, Sticking of the developer to the layer regulating member, filming, and the like are unlikely to occur, and the entire apparatus can be reduced in size. Further, when the developer of the present invention is used, even when a color image is formed, an extremely high-quality image having good color reproducibility can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of an image forming apparatus that can be used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Developer container 2 ... Developer 5 ... Developer carrier 7 ... Photoconductor 10 ... Cleaning unit

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yasuhiro Osugi 1-14-10 Uchikanda, Chiyoda-ku, Tokyo Inside the head office of Tokyo Electric Co., Ltd. (56) References JP-A-5-307319 (JP, A) JP-A-5-216275 (JP, A) JP-A-62-279261 (JP, A) JP-A-62-103675 (JP, A) JP-A-2-61652 (JP, A) JP-A-4-1773 (JP, A) JP-A-2-132459 (JP, A) JP-A-58-1947 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 13/01 G03G 13 / 08 G03G 15/01-15/01 117 G03G 15/08-15/08 507 G03G 9/08

Claims (2)

(57) [Claims] A step of supplying a developer to an outer peripheral surface of a developer carrier to form a developer layer; and contacting the developer layer with an electrostatic latent image holding member to form the developer layer on the electrostatic latent image. Applying a developer to develop a visible image, using an electrostatic latent image holding member having a diameter of 20 mm or less, and having an average particle diameter D ₅₀ in a volume particle size distribution. Of 70
% Of particles having a particle size of not more than 25%,
And an image forming method which comprises using a non-magnetic one-component developer fraction of a plurality of colors is less than 15% of the particles having a particle size of more than 130% of the average particle diameter D _50. 2. An average particle diameter D ₅₀ of a developer having the largest size among the non-magnetic one-component developers of the plurality of colors is represented by r ₁ ,
Most When the average particle diameter D ₅₀ of the small consisting developer was r _2, claims, characterized in that the ratio r ₁ / r ₂ is used under the condition of _{1 ≦ r 1 / r 2 ≦} 1.2 2. The method according to 1.