JPH086292A - Electrophotographic developing toner and image forming method - Google Patents

Abstract

PURPOSE:To provide a color image forming method capable of forming color images having good color reproducibility without generating color clouding at edges and further a color developer which does not generate color clouding at the edges. CONSTITUTION:This developer is used for the image forming method of forming the color images by having at least LED exposure systems 6 to 9 and plural developing devices 10 to 13 and forming the color images by repeating development plural times by a reversal development system on a photoreceptor, then integrally transferring the color images onto a transfer material and fixing the color images contains at least a resin and pigments. The developer described above contains toners consisting of >=74number% pigment particles existing in the toner particles having a major axis of Xnm or below, when the light emission wavelength of LED is defined as Xnm, <=20nunaber% pigment particles having the major axis of above Xnm to 2Xnm, <=5number% pigment particles having the major axis above 2Xnm to below 3Xnm and <=1number% pigment particles having the major axis of >=3Xnm.

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 photoconductor is transferred onto a paper, which is a sequential transfer body, or a transfer member, which is an intermediate transfer body, and is then collectively transferred onto a paper or the like and superposed. A method of forming an image and producing a full-color image is known. However, in the method of sequentially superposing color images on paper or a transfer member, not on these photoconductors, a transfer drum for supporting a transfer member such as paper or a member called an intermediate transfer member is required, There is a drawback that the structure of the machine body becomes large.

Therefore, there has been proposed a method of forming a color superposed image by developing a plurality of times on a photoconductor without using an intermediate transfer body or the like. In this method, since the entire color image is formed on the photoconductor, the photoconductor has the disadvantage that it needs to have the same size as the image surface and becomes large, but since an intermediate transfer body is not required, the entire apparatus is Has the advantage of being small.

In the color image forming apparatus, the LED is more advantageous as the exposure system than the laser recording system because the size of the machine is required to be small. That is, the LED exposure system is an exposure system composed of light emitting diodes. This shows an exposure system in which LED arrays are arranged in a staggered or linear fashion at the density at which the LEDs themselves should be recorded. This device has an advantage that it can be miniaturized as compared with an ordinary semiconductor laser exposure system and the like because the light emitting portion is small and the optical path length for focusing is very short.

Further, for example, JP-A-4-102874 and JP-A-4-102874
In 3-233471, etc., a method is proposed in which four photosensitive members are sequentially charged, exposed, and developed, and a superimposing image is formed by sequentially advancing this process, and then collectively transferred. ing. In this method, there is an advantage that the size of the photoconductor does not need to be increased so much and the entire machine can be downsized. Further, in this system, it is not necessary to rotate the photoconductor a plurality of times, and there is an advantage that the printing speeds of the full-color image and the monochrome image are the same.

In the method for forming a color image on the photoconductor without using the above-mentioned intermediate transfer member, charging and exposure are carried out in the state where the toner is developed on the photoconductor after the development of the second color. The photoreceptor is exposed through the imaged toner. There are problems with exposure through this toner, but a complete solution has not been found.

In the structure of the present invention in which the steps of charging, exposing and developing are carried out a plurality of times to form an image on the photosensitive member, four exposures are required to form a full color image.
The ED exposure system is particularly preferable in that the apparatus can be downsized. In this configuration, the toner developed on the photoconductor is further charged.
Since it is necessary to repeat the exposure and development, it is necessary to perform the exposure by eliminating the influence of the above-mentioned toner in the exposure. In this case, light needs to pass through the toner in order to perform exposure from above the toner. However, since the conventional toner cannot sufficiently transmit the light of the LED due to the influence of the pigment present in the toner, the charge on the photoconductor cannot be erased. As a result, the potential changes especially at the edges,
This will cause a problem of color turbidity at the edges. In particular, the LED has a shallow depth of focus, so that the above problems are more likely to occur as compared with laser exposure. Further, in a multicolor color superimposing image forming system using so-called reversal development, which gives exposure corresponding to an image on a photoreceptor,
Since it is required to write an image on the developed toner, if the depth of focus is shallow like an LED, this also poses a problem.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to form a color image on a photoconductor by a reversal development method while forming a color image on a photoconductor which has at least a constituent part consisting of a strip electrode, an LED exposure system and a developing device. After that, in the image forming method in which a color image is formed by transferring and fixing all at once, it is possible to form a color image with good color reproducibility without causing color turbidity at the edge portion. An object is to provide an image forming method. Another object is to provide a color developer that does not cause color turbidity even at the edge portion.

[0009]

The object of the present invention can be achieved by adopting any one of the following configurations.

(1) In a toner obtained by adding inorganic fine particles to colored particles comprising at least a resin and a pigment, L
When the emission wavelength of ED is X nm, the number of pigment particles present in the toner is 74% by number or more with a long axis of less than X nm, and the number of pigment particles with a long axis of X nm or more and less than 2 X nm is 20% by number or less. There are 5 long-axis pigment particles of 2Xnm or more and less than 3Xnm.
An electrophotographic developing toner characterized in that the number of pigment particles is 3% or less and the number of pigment particles having a long axis of 3 × nm or more is 1% or less.

(2) A step of uniformly charging the surface of the photoconductor,
A step of imagewise exposing the uniformly charged surface of the photoreceptor with an LED exposure system, a step of applying a bias voltage to the surface of the photoreceptor on which an imagewise latent image is formed to invert the latent image, and a developing toner for the latent image. In the image forming method, there is a step of transferring the color image formed by repeating the above steps with a visible image on the photoconductor to the transfer body all together. 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 is 74% by number or more whose major axis is less than X nm. 20% by number or less of pigment particles having a long axis of Xnm or more and less than 2Xnm and 5% or less by number of long axis pigment particles of 2Xnm or more and less than 3Xnm, and 1% by number of long axis pigment particles of 3Xnm or more. Use a developer containing a toner that is The image forming method according to claim.

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

(4) The image forming method according to item (2) or (3), wherein the photoconductor is a negatively chargeable photoconductor.

That is, in the present invention, the transmittance of LED light can be increased by defining the relationship between the presence state of the pigment in the toner and the exposure wavelength, and as a result, the exposure from the toner can be facilitated. can do. For this reason,
In particular, when the images are superposed 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 photoconductor, then collectively transferring the color image to a transfer body, fixing the color image, and then ending the color image formation. Is. Here, the transfer body refers to a material that holds the final image transferred and fixed, such as copy paper (plain paper), a polyester transparent plate for OHP (overhead projector), and the like.

The image forming method which can be used in the present invention has a strip electrode and an exposure system, and further has a plurality of developing devices corresponding to color developers. This is a method in which the photosensitive member is rotated corresponding to each color, charging, exposure, and development are repeated to form the entire color image on the photosensitive member, and the color image is formed by transferring the entire color image onto the transfer member at once. In this case, the reversal development method is suitable because the stability of the exposure system can be maintained for a long period of time. An example of this image forming apparatus is shown in FIG.
The photoconductor may be a drum-shaped photoconductor or a belt-shaped photoconductor.

Further, another construction of the machine used in the present invention has at least a plurality of constituent parts including at least a strip electrode, an exposure system and a developing device, and a color image is formed on the photoconductor by a reversal development method. After being formed, it has a structure in which it is collectively transferred and fixed to a transfer body.

An example of the image forming apparatus used in the present invention is shown in FIG. Here, the image forming apparatus has at least one charging device, an exposing device, and a developing device under the endless image forming support stretched between the rotating rollers. That is, in this image forming apparatus, the steps of charging, exposing, and developing are configured as a unit, and a monochromatic image is sequentially formed on the image forming support (photoreceptor), and as a result, a full-color image is formed on the photoreceptor. After being formed, they are 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 the printing speed between the single-color image and the 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 structure at the charging, exposing, and developing process parts, and this process is stable. Further, it has an advantage that the machine can be made smaller because a flat structure can be formed as compared with the drum-shaped photoreceptor.

Further, it is preferable that the steps of charging, exposing and developing are installed below the photoconductor. The reason for this is
It is necessary to release the unit when a problem such as a paper jam occurs, but by installing a process such as exposure at the bottom, the top surface to be released can be lightened, so it is easy to release. This is because there is an advantage that replacement of the photoconductor is easy.

In the LED system, a mixed crystal of GaAs and GaP and G
A mixed crystal of aAs and AlAs is often used. Furthermore, InGaP
Some types are also used. The wavelength of the light generated (emission wavelength) is approximately 640 to 800 nm. The preferred range depends on the sensitivity of the photoconductor, but any of these ranges can be used when the organic photoconductor preferably used in the present invention is used. It is not necessary to limit the size of the LED when a single exposure system is used, but it is necessary to reduce the size in the case of a system having a plurality of charging, exposing and developing sections. Next to
The width of the LED is preferably 10 mm or less.

The LED exposure system is constructed in the form of an LED array in which the above-mentioned LEDs having a light emitting surface corresponding to the recording density are arranged in a line or in a plurality on the recording surface. In this case, depending on the recording density, 200, 240, 300, 400, 600dpi (dot / inc
The one having the constitution of h) is appropriately used. The LED corresponding to the recording density indicates, for example, in the case of 300 dpi, an LED having 300 light emitting parts per inch. That is, in this case, the major axis on the surface of the photoconductor 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 selected according to the recording density.

In any of the systems, the development system which does not contact the photoconductor is used for the development. In this case, a thin layer forming developing system in which the developer is conveyed to the developing area in a thin layer is preferable.

[Development Method for Forming Thin Layer] The thin layer forming method is 20 to 50 in the developing area on the surface of the developer carrying member (developing sleeve).
A method of forming a 0 μm developer layer. When forming this thin layer, there are a magnetic blade that uses a magnetic force and a method of pressing a developer layer restriction rod against the surface of the developer carrying member.
Further, there is also a method of contacting a surface of a developer bearing member with a urethane blade, a phosphor bronze plate or the like to regulate the developer layer.

As the developer carrying member, one having a magnet built into the carrying member is used, and as the developer carrying member surface, aluminum or aluminum whose surface is oxidized or stainless steel is used. .

The pressing force of the pressure regulating member is 1 to 15 gf /
mm is preferred. When the pressing force is small, the regulation force is insufficient and the conveyance becomes unstable. 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
Is.

The gap between the developer bearing member and the surface of the photosensitive member is preferably larger than that of the developer layer. Further, either a system in which only a DC component is applied as the developing bias, or a system in which an AC bias or both are applied may be used.

As the size of the developer carrying member, the diameter is 10 to
40 mm is suitable. If the diameter is small, the developer is insufficiently mixed, and it becomes difficult to ensure a sufficient mixed state for charging the toner.If the diameter is large, the centrifugal force against the developer becomes large, The problem of toner scattering occurs.

[Structure of Photoreceptor] As the photoreceptor used in the present invention, any of so-called drum-shaped or belt-shaped photoreceptors can be used. A particularly preferable combination has a single charging / exposure system, and a drum-shaped or belt-shaped photosensitive member can be used when it has a plurality of developing devices. On the other hand, the photoconductor used in the case of the constitution having a plurality of charging / exposure / developing portions is preferably an endless so-called belt-shaped one.

The photosensitive member is obtained by coating or vapor-depositing a conductive material such as aluminum on a belt-shaped support and forming an organic photoconductor or an inorganic photoconductor on the surface of the support. is there. A particularly preferred form is an organic photoconductor.

Incidentally, in the sense that conventionally used toner, which has a great deal of accumulated technology, can be used, and the photoconductor is easy to manufacture, the negative charge type photoconductor is preferable to the positive charge type.

[Structure of Developer] The toner used in the present invention is a toner obtained by adding and mixing inorganic fine particles to colored particles containing a binder resin, a colorant, and other additives used as necessary. . The average particle diameter is a volume average particle diameter of usually 1 to 30 μm, preferably 5 to 15 μm. The binder resin that constitutes the colored particles is not particularly limited, and various conventionally known resins can be used. For example, styrene resin
Examples thereof include acrylic resin, styrene / acrylic resin, polyester resin and the like.

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

More specifically, for example, carbon black and nigrosine dye are used as black toner, and CI pigment blue 15: 3, CI pigment blue 15, CI are used as pigments required for yellow, magenta and cyan toners. 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. The above pigments can be preferably used.

In order to form the toner of the present invention, when the dispersion diameter of the pigment is the emission wavelength (Xnm) of the LED, the number of long axes below Xnm is 74% by number or more, preferably 80% by number.
As described above, the pigment having a long axis of Xnm or more and less than 2Xnm is 20 number% or less, preferably 15 number% or less, and the long axis of 2Xnm or more and less than 3Xnm is 5 number% or less, preferably 3 number% or less, and 3Xnm or more. It is necessary that the major axis is less than 1% by number and preferably not exist. The long axis is the length of the pigment particles in the longitudinal direction 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 dispersed particle size of the pigment present in the toner, the photoconductor is sufficiently exposed even through the exposure through the toner. Since it can be exposed to light, no problem occurs in the exposure of the edge portion where the toner particles overlap.

Here, 74% by number of pigments having a long axis of less than X nm
When the amount is less than the above, the amount of light passing therethrough is reduced, the exposure through the toner is insufficient, and the toner is mixed with color at the edge portion due to development, resulting in color turbidity. Xnm or more 2Xnm
20% by number or more than 2Xnm and 3Xnm of long axis pigment less than
If the number of long-axis pigments of less than 5% by number or more and the number of long-axis pigments of 3Xnm or more exceeds 1% by number, the LED is used in any case.
Light scattering occurs, and light is scattered around the developed toner, resulting in insufficient exposure. As a result, toner color mixing occurs at the edge portion and color turbidity occurs.

As a method for forming such a dispersed state, a method in which the 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, the pigment forms agglomerated particles. Therefore, it is preferable to use a method in which the agglomerated particles are crushed by using a crusher or the like. In this case, since the pigment having a large particle diameter is reduced, it is preferable to remove the pigment having a particle diameter having a long axis of 3 × nm or more in a step such as classification before use.

In order to disperse the pigment, it is preferable to use it by dispersing it in the resin as described above. 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 vigorously disperse and use it 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 broken, and the fixing property is deteriorated, and in particular, offset is excessively generated.

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

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

On the other hand, a method in which the pigment itself is pulverized and classified to be used in a predetermined particle size distribution can be also mentioned as a preferable method. That is, unlike the method of firstly dispersing the pigment in the resin and then dispersing the pigment in the resin for toner, the pigment is directly pulverized and classified to be 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 improving agents such as low molecular weight polyolefins and carnauba wax.

Further, the colored particles have a number average primary particle diameter of 5 to 30 nm, such as silica, titanium oxide and aluminum oxide.
It is preferable that the inorganic fine particles are added and mixed to form a toner. The addition amount of this inorganic fine particle 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 resin, or a resin and magnetic powder are used. Any of the resin dispersion type carriers obtained by mixing the above may be used. The average particle size of this carrier is 30 to 150 in terms of volume average particle size.
μm is preferred.

[0045]

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

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

The process of the image forming method is shown in FIG. 1. In FIG. 1, the image is a photoreceptor 26 uniformly charged by a strip electrode 27.
The LED exposure system 21 performs imagewise exposure for the image. Then, the developing device 22 reversely develops the image under a bias, so that an image of one color is formed on the photoconductor. In this case, the photoconductor is not cleaned and is not transferred. Then, the second color process is performed according to the above process, and this process is repeated for four colors. After the four-color image is formed on the photoconductor, the transfer section 23 transfers the toner onto the image transfer body such as paper, and then the fixing section 24 fixes the toner onto the image transfer body such as paper. The photoconductor that has completed the transfer is cleaned by the cleaning unit 25, and the next image is formed.

The developing device is a color copying machine Ko manufactured by Konica Corporation.
The developing device used in nica9028 was modified and used.
The developing conditions are as shown below.

Photoconductor surface potential = -550V DC bias = -250V AC bias = Vp-p: -50 to -450V Dsd = 300 .mu.m Pressing control force = 10 gf / mm Pressing control rod = SUS416 (magnetic stainless steel) / 3 mm diameter Developer carrier diameter = 20 mm Developer layer = 100 μm Dsd: The closest distance between the developer carrier surface and the photoreceptor 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, 1 denotes an endless image forming support (photoreceptor) supported by a rotating roller 20. Further, 2, 3, 4, 5 are band electrodes, and 6, 7, 8, 9 are LEs.
D exposure system, 10, 11, 12, and 13 represent developing devices. In this configuration, first, the belt electrode 2 uniformly charges the photoconductor 1. Then, the LED exposure system 6 performs exposure corresponding to the image, a bias is applied, and the image is visualized on the photoconductor 1 by reversal development by the developing device 10. Subsequently, the photoreceptor visualized by the developing device 10 is successively charged by the strip electrode 3, exposed by the exposure system 7, and developed by the developing device 11, and further, the strip electrode 4, the exposure system 8, the developing device 12, and then the The steps of the strip 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 visible image formed on the photoconductor is transferred onto the image transfer body by the sequential transfer section 14. Further, the cleaning unit 17 sequentially cleans the untransferred toner, and the photosensitive member enters the next image forming process.

As the photoreceptor, there was used a laminated organic photoreceptor in which a subbing layer, a charge generation layer and a charge transport layer were successively laminated on a 100 μm-thick support on which belt-shaped aluminum was vapor deposited. Further, the support of the belt-shaped photosensitive member is formed by adhering the end portions of the sheet to form an endless shape. Furthermore, an LED array arranged at 300 dpi (dot / inch) was used as the exposure section.

As the LED, an LED having a wavelength of 770 nm was used.

The developing device is a color copying machine Ko manufactured by Konica Corporation.
The developing device used in nika9028 was modified and used.
The developing conditions are as shown below.

Photoconductor surface potential = -550V DC bias = -250V AC bias = Vp-p: -50 to -450V Dsd = 300 .mu.m Pressing regulation force = 10 gf / mm Pressing regulation rod = SUS416 (magnetic stainless steel) / 3 mm in diameter Developer carrier diameter = 20 mm Developer layer = 120 μm 3. Pigment Preparation Example As a pigment, 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 crushing and classifying each pigment. This is called "crushed pigment". Further, each pigment was repeatedly mixed with a polyester resin in a state of a pigment concentration of 40% by weight with a two-roll mill to adjust the major axis particle size. This is called a "kneading pigment". The particle size of the pigment thus obtained was observed with a transmission electron microscope to measure the major axis particle size. The pulverized pigment was embedded in an ultraviolet curable resin, and a thin piece having a thickness of about 0.1 μm was prepared by 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-mentioned evaluation machine, the pigment particle diameters were adjusted to meet the conditions of both.

[0056]

[Table 1]

[0057]

[Table 2]

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

[0059]

[Table 3]

[0060]

[Table 4]

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

[0062]

[Table 5]

6. Evaluation items In the evaluation, a full-color image with a pixel ratio of 50% was printed in an environment of normal temperature and low humidity (20 ° C / 15% RH) using the evaluation device under the above conditions, and the presence or absence of color turbidity was evaluated. In Evaluation Machine 1, Developers 1 to 5 and Comparative Developers 1 and 2 were used, and in Evaluation Machine 2, Developers 6 to 10 and Comparative Developers 3 and 4 were used. The development was carried out in the order of yellow → magenta → cyan → black. Especially in this evaluation, since the yellow toner was first developed, the color turbidity was evaluated in the image adjacent to the yellow image. As an evaluation method, a reflection image of the edge portion of the yellow image was photographed with an optical microscope, and then the image was magnified 20 times, and then the color turbidity of the edge portion was visually determined. The case where a large number of toners of other colors are mixed and the color turbidity is observed without expansion is marked as ×, and the color turbidity that is mixed but the color turbidity cannot be visually judged is △, and further If the toner is observed on the edge in a very small amount (a few particles), △ ～
It was evaluated as ◯, and the state where no other color toner was present in 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 strip electrode / LE
D A color image is formed by sequentially transferring and fixing a color image after the image formation while sequentially forming a color image on the negatively charging photoreceptor by a reversal development method, which has at least a plurality of components including an exposure system and a developing device. In the image forming method for forming an image, it is possible to provide a color image forming method capable of forming a color image having good color reproducibility without causing color turbidity at an edge portion. Furthermore, it is possible to provide a color developer that does not cause color turbidity even at the edge portion.

[Brief description of drawings]

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

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

[Explanation of symbols]

 1 Endless image forming support (belt-like photoconductor) 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 Developer 11 Developer 12 Developer 13 Developing device 14 Transfer part 18 Fixing part 20 Rotating roller 21 LED exposure system 22 Developing device 23 Transfer part 24 Fixing part 25 Cleaning part 26 Photoconductor 27 Band electrode

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G03G 15/01 J 112 A 113 Z 15/08 503 A 507 L G03G 9/08 381

Claims (4)

[Claims] 1. A toner comprising a colored particle comprising at least a resin and a pigment, to which inorganic fine particles are added.
When the emission wavelength of X is X nm, the number of pigment particles present in the toner is 74% by number or more with a long axis of less than X nm,
20% by number of pigment particles having a long axis of Xnm or more and less than 2Xnm
Below, 5% by number or less of long-axis pigment particles of 2Xnm or more and less than 3Xnm, and 1% by number of long-axis pigment particles of 3Xnm or more
The toner for electrophotographic development according to the following: 2. A step of uniformly charging the surface of the photoreceptor, a step of imagewise exposing the uniformly charged surface of the photoreceptor with an LED exposure system, and a bias voltage is applied to the surface of the photoreceptor on which an imagewise latent image is formed. The step of applying and reversing the latent image, the step of developing the latent image with a developing toner, and the step of repeating the above steps with the visible image on the photoconductor to form a color image on the transfer body. In the image forming method including the step of transferring all at once,
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,
74% by number or more of the pigment particles present in the toner have a long axis of less than X nm, and 20% by number or less of pigment particles having a long axis of X nm or more and less than 2 X nm, and a pigment having a long axis of 2 X nm or more and less than 3 X nm. An image forming method comprising using a developer containing a toner having 5% by number or less of particles and 1% by number or less of long-axis pigment particles of 3 × nm or more. 3. The image forming method according to claim 2, wherein at least each of the strip electrode, the LED exposure system and the developing device has the number of toners to be used. 4. The photosensitive member is a negatively charging photosensitive member.
Alternatively, the image forming method described in 3.