JP3298035B2 - Electrophotographic developing toner and 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 electrophotographic developer and a color image forming method.

[0002]

2. Description of the Related Art Conventionally, a single-color image formed on a photoreceptor is transferred onto a paper as a sequential transfer member or onto a transfer member as an intermediate transfer member, and then transferred onto a paper or the like at one time and superimposed. A method for forming an image to produce a full-color image is known. However, in the method of successively superimposing color images on paper or a transfer member instead of on the photoconductor, a transfer drum for supporting a transfer body such as paper or a member called an intermediate transfer body is required. There is a disadvantage that the structure of the machine body becomes large.

For this reason, a method has been proposed in which development is performed a plurality of times on a photoreceptor without using an intermediate transfer member or the like to form a color superimposed image. This method has the disadvantage that the photoreceptor requires the same size as the image surface and becomes large in order to form the entire color image on the photoreceptor, but since the intermediate transfer member is unnecessary, the entire apparatus is used. Has the advantage of being compact.

In a color image forming apparatus, an LED has an advantage as an exposure system as compared with a laser recording system due to the necessity of reducing the structure of a machine. That is, the LED exposure system is an exposure system configured by a light emitting diode (Light Emitting Diode). This shows an exposure system in which LED arrays are arranged in a staggered or linear manner at a density at which the LEDs themselves are to be recorded. This device has an advantage that it can be downsized by, for example, having a small light emitting portion and a very short optical path length for condensing light, as compared with a normal semiconductor laser exposure system or the like.

Further, for example, Japanese Patent Application Laid-Open No.
In JP-A-3-233471, there is proposed a method in which a photoconductor is charged, exposed, and developed in a sequence of four, a superposed image is formed by sequentially performing this process, and a batch transfer is performed after the formation. ing. This method has the advantage that the size of the photoreceptor does not need to be too large, and the entire machine can be reduced. Further, this method does not require a plurality of rotations of the photoconductor, and has the advantage that the printing speed of a full-color image and that of a monochrome image are the same.

In the above-described method of forming a color image on a photoreceptor without using an intermediate transfer member, charging and exposure are performed in a state where toner is developed on the photoreceptor after the second color development. Exposure is performed on the photoreceptor via the imaged toner. Although exposure through this toner causes problems, no complete solution has been found.

In the structure of the present invention in which an image is formed on a photoreceptor by performing the charging, exposing, and developing steps a plurality of times, four exposures are required to form a full-color image.
An ED exposure system is particularly preferable in that the size of the apparatus can be reduced. In this configuration, the toner developed on the photoconductor is further charged and charged.
Since it is necessary to repeat exposure and development, it is necessary to perform exposure in which the above-described influence of the toner is eliminated. In this case, light must pass through the toner in order to perform exposure from above the toner. However, with the conventional toner, the light of the LED cannot be sufficiently transmitted due to the influence of the pigment present in the toner, so that the charge on the photoconductor cannot be erased. As a result, the potential fluctuates especially at the edge,
This causes a problem that color turbidity occurs at the edge portion. In particular, since the depth of focus is small in the LED, the above problem is likely to occur as compared with the laser exposure. Further, in a multicolor color superimposed image forming system using so-called reversal development, which gives an exposure corresponding to an image to a photoconductor,
Since it is required to further write an image on the developed toner, if the depth of focus is small like an LED, the problem is also great.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to form a color image on a photoreceptor by sequentially forming a color image on a photoreceptor by a reversal development method. Thereafter, in an image forming method in which a color image is formed by transferring and fixing all at once, a color capable of forming a color image with good color reproducibility without generating color turbidity at an edge portion. An object of the present invention is to provide an image forming method. Another object of the present invention is to provide a color developer which does not cause color turbidity even at an edge portion.

[0009]

The object of the present invention is attained by adopting one of the following constitutions.

[0010]

( 1 ) a step of uniformly charging the surface of the photoreceptor,
A step of imagewise exposing the uniformly charged photoreceptor surface with an LED exposure system, a step of applying a bias voltage to the photoreceptor surface on which the image-like latent image is formed to invert the latent image, and a step of developing the latent image with a developing toner In the image forming method, the method includes a step of collectively transferring a color image formed by repeatedly performing the above-described steps while having a visible image on the photoreceptor, to a transfer body. The toner contains at least a resin and a pigment, and when the emission wavelength of the LED used in the exposure system is X nm, the number of pigment particles present in the toner whose major axis is less than X nm is 74% by number or more. 100% by number or less , X
pigment particles having a major axis of less than nm or more 2Xnm 0 number
% And 20 % by number or less and 2 % or more and 3 % or less and 3Xnm or less of the long axis pigment particles are 0% by number or more and 5% by number or less,
0 to 1% by number of pigment particles having a major axis of 3Xnm or more
An image forming method using a developer containing the following toner.

( 2 ) The image forming method according to ( 1 ), wherein at least each of the band electrode, the LED exposure system and the developing device has the number of toners to be used.

( 3 ) The image forming method according to ( 1 ) or ( 2 ), wherein the photosensitive member is a negatively chargeable photosensitive member.

That is, in the present invention, by defining the relationship between the state of the pigment in the toner and the exposure wavelength, the transmittance of LED light can be increased, and as a result, exposure from the toner can be easily performed. can do. For this reason,
Particularly, when images are superimposed at the edge portion, color turbidity does not occur and an image with good reproducibility can be formed.

[0015]

[Action]

[Mechanical structure of the present invention] The image forming method used in the present invention is a method of forming a color image on a photoreceptor, then transferring the color image collectively to a transfer body, fixing the color image, and terminating the color image formation. It is. Here, the transfer body refers to a material that holds the final image after transfer and fixing, such as copy paper (plain paper) and a polyester transparent plate for OHP (overhead projector).

An image forming method that can be used in the present invention includes a band electrode, an exposure system, and a plurality of developing units corresponding to a color developer. In this method, the photoreceptor is rotated in accordance with each color, and charging, exposure and development are repeated to form the entire color image on the photoreceptor and collectively transferred to a transfer body to form a color image. In this case, the reversal development method is preferable because the stability of the exposure system can be maintained for a long time. FIG. 1 shows an example of this image forming apparatus.
The photoconductor may be either a drum-shaped photoconductor or a belt-shaped photoconductor.

Further, another machine used in the present invention has at least a plurality of components including at least a band electrode, an exposure system, and a developing device, and forms a color image on a photoreceptor by a reversal developing method. After forming, it is configured to collectively transfer and fix to a transfer body.

FIG. 2 shows an example of the image forming apparatus used in the present invention. Here, the image forming apparatus has at least one or more of a charging device, an exposing device, and a developing device below an endless image forming support that is stretched between rotating rollers. That is, in this image forming apparatus, the steps of charging, exposing, and developing are configured as a unit, and a single-color image is sequentially formed on an image forming support (photoreceptor), and as a result, a full-color image is formed on the photoreceptor. It is formed and is collectively transferred to a transfer body such as paper. Therefore, it is not necessary to rotate the photoconductor a plurality of times when forming a full-color image, and there is no difference in printing speed between a single-color image and a full-color image. In the present invention, an endless photoconductor is used as the photoconductor. The reason for this is that it is possible to take a planar configuration at the charge, exposure and development process sites, so that this process is stable. Further, since a flat structure can be formed as compared with the drum-shaped photoreceptor, there is an advantage that the size of the machine can be reduced.

Further, the steps of charging, exposing, and developing are preferably provided below the photosensitive member. The reason for this is
When a problem such as a paper jam occurs, it is necessary to release the unit, but by installing a process such as exposure at the bottom, the released upper surface can be reduced in weight, which is easy to release. This is because there is an advantage that the exchange of the photoreceptor becomes easy.

In the LED system, a mixed crystal of GaAs and GaP and G
Mixed crystals of aAs and AlAs are often used. In addition, InGaP
Types are also used. The wavelength of the generated light (emission wavelength) is generally about 640 to 800 nm. The preferred range depends on the sensitivity of the photoreceptor, but when the organic photoreceptor suitably used in the present invention is used, any of these ranges can be used. It is not necessary to limit the size of the LED when using a single exposure system, but it is necessary to reduce the size when using a system with multiple charging, exposure, and development sections. Becomes
It is preferable to make the width of the LED 10 mm or less.

The LED exposure system is configured as an LED array in which one or more LEDs having a light emitting surface corresponding to the recording density are arranged on the recording surface in one or more rows. In this case, 200, 240, 300, 400, 600 dpi (dot / inc
h) is appropriately used. The LED corresponding to the recording density is, for example, an LED having 300 light emitting units per inch in the case of 300 dpi. That is, in this case, the major axis on the photoreceptor surface is about 100 μm,
A material that emits light having an elliptical shape with a minor axis of about 90 μm is used. The emission diameter itself is variously controlled, and is selected according to the recording density.

In either system, a developing system that does not contact the photoconductor is used for development. In this case, a thin layer forming and developing method in which the developer is transported to the developing area in a thin layer is preferable.

[Developing Method for Thin Layer Formation] A thin layer forming method is a method in which a developing area is 20 to 50 on a surface of a developer carrying member (developing sleeve).
A method of forming a 0 μm developer layer. In order to form the thin layer, there are a magnetic blade using a magnetic force, a method of pressing a developer layer regulating rod against the surface of a developer carrying member, and the like.
Furthermore, there is a method in which a urethane blade, a phosphor bronze plate or the like is brought into contact with the surface of the developer carrier to regulate the developer layer.

As the developer carrier, one having a magnet built in the carrier is used. As the surface constituting the developer carrier, aluminum or aluminum or stainless steel whose surface is oxidized is used. .

The pressing force of the pressing regulating member is 1 to 15 gf /
mm is preferred. When the pressing force is small, the conveyance becomes unstable due to insufficient regulating force. On the other hand, when the pressing force is large, the stress on the developer increases, and the durability of the developer decreases. The preferred range is 3 to 10 gf / mm
It is.

The gap between the developer carrier and the surface of the photoreceptor is preferably larger than the developer layer. Further, a method of applying only a DC component as a developing bias, a method of applying an AC bias, or both of them may be used.

The size of the developer carrying member is 10 to 10 mm in diameter.
40 mm is preferred. When the diameter is small, the mixing of the developer is insufficient, and it is difficult to ensure a sufficient mixing state for charging the toner, and when the diameter is large, the centrifugal force on the developer becomes large, A problem of toner scattering occurs.

[Construction of Photosensitive Member] As the photosensitive member used in the present invention, any of so-called drum-shaped or belt-shaped photosensitive members can be used. In a particularly preferred combination, a single charging / exposure system is provided, and when a plurality of developing devices are provided, either a drum-shaped or a belt-shaped photoconductor can be used. On the other hand, in the case of a configuration having a plurality of charging / exposing / developing units, the photoconductor used is preferably an endless so-called belt-shaped one.

The structure of the photoreceptor is obtained by forming an organic photoconductor or an inorganic photoconductor on the surface of a belt-shaped support coated or deposited with a conductive material such as aluminum. is there. A particularly preferred embodiment is an organic photoreceptor.

It should be noted that a negatively chargeable photoreceptor is more preferable than a positively chargeable photoreceptor from the viewpoint that conventionally used toners, which have a large accumulation of technology, can be used and the photoreceptor can be easily manufactured.

[Construction of Developer] The toner used in the present invention is a toner obtained by adding inorganic fine particles to colored particles containing a binder resin, a colorant, and other additives used as required. . The average particle size is usually from 1 to 30 μm, preferably from 5 to 15 μm as a volume average particle size. There is no particular limitation on the binder resin constituting the colored particles, and various conventionally known resins are used. For example, styrene resin
Acrylic resin, styrene / acrylic resin, polyester resin and the like can be mentioned.

The colorant is not particularly limited, and carbon black, nigrosine dye, aniline blue, carbon coil blue, chrome yellow, ultramarine blue, Dupont oil red, quinoline yellow, methylene blue chloride, and the like, which are conventionally known for color toners, are used. Phthalocyanine Blue Malachite Green Oxalate
Rose Bengal and the like.

More specifically, for example, carbon black / nigrosine dye or the like is used as a black toner, and pigments required for yellow, magenta, and cyan toners include CI Pigment Blue 15: 3, CI Pigment Blue 15, and CI Pigment Blue 15. Pigment Blue 15: 6, CI Pigment Blue 68, CI Pigment Red 48-3, CI Pigment Red 122, CI Pigment Red 212, CI Pigment Red 57-1, CI Pigment Yellow 17, CI Pigment Yellow 81, CI Pigment Yellow 154, etc. Can be suitably used.

In order to constitute the toner of the present invention, when the dispersion diameter of the pigment is the emission wavelength (X nm) of the LED, the number of the major axis of less than X nm is 74% by number or more, preferably 80% by number.
As described above, the pigment having a major axis of X nm or more and less than 2X nm is 20% or less, preferably 15% or less, and the major axis pigment of 2X nm or more and less than 3X nm is 5% or less, preferably 3% or less, and 3X nm or more. It is necessary that one having a major axis of 1% or less is preferably not present. The long axis is obtained by measuring the length in the longitudinal direction of the pigment particles observed by a scanning electron microscope or a transmission electron microscope. The number% is calculated by measuring 500 pigments present in the toner.

In the present invention, since the light scattering of the LED can be prevented by adjusting the dispersion particle size of the pigment present in the toner, the photosensitive member can be sufficiently exposed even through exposure through the toner. Therefore, there is no problem in exposing an edge portion where toner particles overlap.

Here, the pigment having a major axis of less than X nm is 74% by number.
If it is less than 3, the amount of light passing therethrough decreases, the exposure via the toner becomes insufficient, and toner color mixing occurs at the edge portion due to development, resulting in color turbidity. Xnm or more and 2Xnm
Less than 20% by number of long-axis pigments and 2Xnm to 3Xnm
If the long-axis pigments of less than 5% by number and more than 3X nm of the long-axis pigments exceed 1% by number, LED
Light scattering occurs, and light is scattered around the developed toner, resulting in insufficient exposure. As a result, color mixing of the toner occurs at the edge portion, causing color turbidity.

As a method for forming such a dispersed state, a method in which a pigment is firstly dispersed in a resin or the like in advance and then dispersed in a resin for forming a toner is preferable.
As a method of controlling the particle size, a method of reducing the particle size at the stage of pigment synthesis is preferable. Further, even when the pigment is primarily dispersed in a resin or the like, since the pigment forms agglomerated particles, a method in which the agglomerated particles are crushed using a crusher or the like is preferably used. In this case, in order to reduce the pigment having a large particle diameter, it is preferable to remove the pigment having a major axis having a major axis of 3X nm or more in a step such as classification before use.

In order to disperse the pigment, a method in which the pigment is dispersed and used as described above is preferred. In this method, unlike the method of vigorously kneading and dispersing the resin and the pigment for constituting the toner itself, it is preferable to use the resin and the pigment vigorously dispersed in another resin. The reason for this is that, although the dispersion itself of the pigment is improved by vigorous dispersion treatment, there is a problem that the molecular chain of the resin is cut off, and there is a problem that the fixing property is reduced, and in particular, the occurrence of offset is excessive.

As a device for dispersing the pigment in the resin, a device capable of repeatedly dispersing with high energy, such as a Banbury mixer, a two-roll or a three-roll, is preferred.

The resin for dispersing the pigment is not particularly limited, and any resin proposed as a resin for toner can be used.

On the other hand, a method in which the pigment itself is pulverized and classified and used as a predetermined particle size distribution can also be mentioned as a preferable method. That is, unlike the above-described method in which the pigment is primarily dispersed in the resin and then dispersed in the toner resin, the pigment is directly pulverized and classified and used as a predetermined particle size distribution.

Examples of other additives include charge control agents such as salicylic acid derivatives and azo metal complexes, and fixability improvers such as low molecular weight polyolefins and carnauba wax.

Further, the colored particles have a number average primary particle diameter of silica, titanium oxide, aluminum oxide, etc. of 5 to 30 nm.
It is preferable that the inorganic fine particles are added and mixed to form a toner. The addition amount of the inorganic fine particles is 0.
It is 1 to 5% by weight, preferably 0.3 to 2% by weight. In addition,
The inorganic fine particles are preferably hydrophobized with various known coupling agents and the like.

As the carrier constituting the two-component developer, an uncoated carrier composed only of magnetic material particles such as iron and ferrite, a resin-coated carrier in which the surface of the magnetic material particles is coated with a resin or the like, or a resin and a magnetic powder Any of the resin-dispersed carriers obtained by mixing the above may be used. The average particle size of this carrier is 30 to 150 in volume average particle size.
μm is preferred.

[0045]

EXAMPLES The present invention will be described below in detail with reference to examples, but embodiments of the present invention are not limited thereto.

1. The machine configuration 1 of the present invention was evaluated by modifying a color copier Konica 9028 having a reversal development system manufactured by Konica Corporation and changing the laser exposure system to a wavelength of 660 nm.
An evaluator modified to an LED array having a recording density of 300 dpi was used. This configuration is shown in FIG. In this configuration, there is one band electrode and one LED exposure system, and a plurality of (four color) developing devices corresponding to the color developer are provided. As the photoconductor, a laminated organic photoconductor in which an undercoat layer, a charge generation layer and a charge transport layer were formed on a drum-shaped aluminum cylinder was used.

FIG. 1 shows the process of the image forming method. In FIG.
Then, an imagewise exposure corresponding to the image is performed by the LED exposure system 21. Next, reverse development is performed by the developing device 22 under the application of a bias, and first, a one-color image is formed on the photoconductor. In this case, the photosensitive member is not cleaned and is not transferred. Next, a second color process is performed according to the above process, and this process is repeated for four colors. After the four color images are formed on the photoreceptor, the toner is transferred onto an image transfer body such as paper by the transfer unit 23, and then fixed on the image transfer body such as paper by the fixing unit 24. The photoconductor on which the transfer has been completed is cleaned by the cleaning unit 25, and the next image is formed.

The developing unit is a color copier Ko manufactured by Konica Corporation.
The developer used for nica9028 was modified and used.
The development conditions are as shown below.

Photoreceptor surface potential = -550 V DC bias = -250 V AC bias = Vp-p: -50 to -450 V Dsd = 300 μm Pressing control force = 10 gf / mm Pressing control rod = SUS416 (made of magnetic stainless steel) / diameter 3 mm 1. Developer carrier diameter = 20 mm Developer layer = 100 μm Dsd: closest distance between developer carrier surface and photoconductor surface Mechanical Configuration 2 of the Present Invention An image forming process of the image forming apparatus having the configuration shown in FIG. 2 will be described (evaluator 2).

Here, reference numeral 1 denotes an endless image forming support (photoreceptor) supported by a rotating roller 20. Further, 2, 3, 4, and 5 are band electrodes, and 6, 7, 8, and 9 are LEs.
D exposure systems, 10, 11, 12, and 13 indicate developing units. In this configuration, first, the photoconductor 1 is uniformly charged by the band electrode 2. Next, exposure corresponding to the image is performed by the LED exposure system 6, a bias is applied, the image is reversely developed by the developing device 10, and the image is visualized on the photoconductor 1. Next, the photoreceptor visualized by the developing device 10 is sequentially charged by the band electrode 3, exposed by the exposure system 7, and developed by the developing device 11, and further, the band electrode 4, the exposure system 8, the developing device 12, and Steps in the band electrode 5, the exposure system 9, and the developing device 13 are sequentially performed. In this case, unlike the image forming method shown in FIG. 1, the visual image formed on the photoconductor is sequentially transferred onto the image transfer body by the transfer unit 14. The photoreceptor enters the next image forming process as the untransferred toner is sequentially cleaned by the cleaning unit 17.

As the photoreceptor, a laminated organic photoreceptor was used in which an undercoat layer, a charge generation layer and a charge transport layer were successively laminated on a belt-like aluminum support having a thickness of 100 μm. Further, the support of the belt-shaped photoreceptor has an endless shape formed by bonding the ends of the sheet. Further, as an exposure unit, an LED array arranged at 300 dpi (dot / inch) was used.

An LED having a wavelength of 770 nm was used as the LED.

The developing device is a color copier Ko manufactured by Konica Corporation.
The developer used for nika9028 was modified and used.
The development conditions are as shown below.

Photoreceptor surface potential = -550 V DC bias = -250 V AC bias = Vp-p: -50 to -450 V Dsd = 300 μm Pressing control force = 10 gf / mm Pressing control rod = SUS416 (made of magnetic stainless steel) / diameter 3 mm 2. Developer carrier diameter = 20 mm Developer layer = 120 μm Pigment Preparation Examples As pigments, CI Pigment Yellow 17 as a yellow pigment, CI Pigment Red 122 as a magenta pigment,
CI Pigment Blue 15: 3 was used as a cyan pigment, and carbon black (Mogal L: manufactured by Cabot Corporation) was used as a black pigment.

The major axis particle size was adjusted by pulverizing and classifying each pigment. This is referred to as “ground pigment”. Further, each pigment was repeatedly mixed with a polyester resin and a two-roll at a pigment concentration of 40% by weight to adjust the long-axis particle size. This is referred to as “kneaded pigment”. The particle size of the pigment thus obtained was observed with a transmission electron microscope, and the major axis particle size was measured. The pulverized pigment was embedded in an ultraviolet curable resin, and a thin piece having a thickness of about 0.1 μm was prepared using a microtome and measured. The kneaded pigment was dispersed in this resin, and a thin piece having a thickness of about 0.1 μm was prepared by a microtome and measured. The results are shown in the table below. Since the wavelengths were different in the above-described evaluation machines, the pigment particle diameters were adjusted to meet the conditions of both.

[0056]

[Table 1]

[0057]

[Table 2]

4. Preparation Example of Toner 100 parts by weight of a polyester resin, 3 parts of a low molecular weight polypropylene and the above-mentioned pigment were kneaded, pulverized and classified to obtain colored particles. 1.0% by weight of hydrophobic silica (number average primary particle diameter = 12 nm) was added to the colored particles to obtain a toner. The production examples are shown in the following table. Further, the results of measuring the particle size of the pigment in the colored particles with a transmission electron microscope are also shown, and it was confirmed that there was no difference from the result of measurement with the pigment alone, as shown below.

[0059]

[Table 3]

[0060]

[Table 4]

5. Example of Developer Preparation To the toner obtained above, a carrier coated with a styrene-acrylic resin was added to ferrite particles having a volume average particle diameter of 60 μm to prepare a developer having a toner concentration of 7% by weight. A list of developers is shown in Table 5 below.

[0062]

[Table 5]

6. Evaluation Items The evaluation was performed by using an evaluation apparatus under the above conditions, printing a full-color image having a pixel ratio of 50% in a normal temperature and low humidity (20 ° C./15% RH) environment, and evaluating the presence or absence of color turbidity. Evaluator 1 used Developers 1 to 5 and Comparative Developers 1 and 2, and Evaluator 2 used Developers 6 to 10 and Comparative Developers 3 and 4. The development was performed in the order of yellow → magenta → cyan → black. In particular, in this evaluation, since the yellow toner is developed first, color turbidity was evaluated in an image adjacent to the yellow image. The evaluation was performed by taking a reflection image of the edge portion of the yellow image with an optical microscope and then magnifying the image 20 times, and then visually determining the color turbidity of the edge portion. A case where a large number of toners of other colors are mixed and color turbidity is observed without enlargement is represented by x, and a case where multi-colored toner is mixed but color turbidity cannot be determined visually is indicated by △. When a very small amount (about several) of toner is observed on the edge,
○ was evaluated, and the state where no other color toner was present at the edge portion was evaluated as ○. The results are shown in Table 6 below.

[0064]

[Table 6]

[0065]

According to the present invention, at least the band electrode / LE
D At least a plurality of components including an exposure system and a developing device are provided. A color image is formed by sequentially transferring and fixing after forming an image while sequentially forming a color image on a negatively chargeable photoreceptor by a reversal developing method. In an image forming method for forming an image, it is possible to provide a color image forming method capable of forming a color image with good color reproducibility without generating color turbidity at an edge portion. Further, it is possible to provide a color developer which does not cause color turbidity even at an edge portion.

[Brief description of the drawings]

FIG. 1 is a sectional view of an image forming apparatus according to the present invention.

FIG. 2 is a sectional view of another image forming apparatus of the present invention.

[Explanation of symbols]

 Reference Signs List 1 endless image forming support (belt-shaped photoreceptor) 2 band electrode 3 band electrode 4 band electrode 5 band electrode 6 LED exposure system 7 LED exposure system 8 LED exposure system 9 LED exposure system 10 Developing device 11 Developing device 12 Developing device 13 Developing unit 14 Transfer unit 18 Fixing unit 20 Rotating roller 21 LED exposure system 22 Developing unit 23 Transfer unit 24 Fixing unit 25 Cleaning unit 26 Photoconductor 27 Strip electrode

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ identification code FI G03G 15/08 503 G03G 9/08 361 507 15/08 507L (58) Investigated field (Int.Cl. ⁷ , DB name) G03G 9/08

Claims (3)

(57) [Claims] A step of uniformly charging the surface of the photoreceptor;
To expose the surface of the photoreceptor charged in an imagewise manner by LED exposure system
The bias voltage is applied to the photoreceptor surface on which the image-like latent image is formed.
Applying and inverting the latent image, and developing the latent image with a developing toner
With the step of visualizing with the visible image on the photoreceptor
Transfer the color image formed by repeating the above process
In the image forming method including the step of batch transfer to
The toner contains at least a resin and a pigment and is exposed to light.
When the emission wavelength of the LED used in the system is X nm,
Pigment particles present in the toner having a major axis of less than X nm
Not less than 74% by number and not more than 100% by number, and
Pigment particles having a major axis of less than 0% and more than 20
% Or less, no long-axis pigment particles of 2Xnm or more and less than 3Xnm
Long axis pigment of 3% to 5% by number, not less than 5%
Contains toner having 0% to 1% by number of particles
An image forming method comprising using a developer. 2. At least a band electrode, an LED exposure system and
Each developer has the number of toners used
The image forming method according to claim 1, wherein: 3. A photoconductor according to claim 1, wherein said photoconductor is a negatively chargeable photoconductor.
Or the image forming method according to 2.