JPH06332234A - Image forming method - Google Patents

Abstract

PURPOSE:To stably obtain high image quality free from fogging at the time of image formation over a long period by using a laminated org. photosensitive body having a specific binder resin and using a specific developer. CONSTITUTION:The binder of a charge transfer layer consists essentially of a polycarbonate resin of the bisphenol Z type speleton. The developer consists of a toner formed by adding inorg. particulates to coloring particles and a carrier. The inorg. particulates are composed of a single kind of an inorg. compd. and have the maximal value xnm of a number ratio in a 20 to 50nm primary particle size range and another maximal value ynm in a 60 to 300nm range in a number primary grain size distribution curve. The number ratio of the primary grain size (x+y)/2nm is <=10 number % and the value of X/Y is in a 0.5 to 2.0 range where the ratios of the inorg. particulates of <(x+y)/2nm are respectively defined as X, Y number %. The value of z/x exists in a 150 to 400 range when the volume average grain size of the coloring particles is defined as znm. Further, the volume average grain size of the carrier exists in a 20 to 60mum range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photoreceptor and particularly to an image forming method characterized by a developer, and more particularly to an image forming method useful in color electrophotography.

[0002]

2. Description of the Related Art Conventionally, as a technique for forming a good multicolor development without color misregistration by using a compact and low-cost multicolor image forming apparatus, a uniformly charged image forming body is used. The surface is spot-exposed with a laser beam or the like to form an electrostatic latent image, and the electrostatic latent image of the image forming body is repeatedly developed by non-contact with a two-component developer containing color toner, A plurality of color toner images of different colors are superposed on the image forming body, and then,
A method of forming a multicolor image by collectively transferring and fixing the plurality of color toner images is known.

However, the technique for forming a multicolor image as described above has the following problems.

When a multicolor image is continuously formed, it is difficult to maintain the toner charge amount of each color within a certain range, and the toner charge amount is likely to change as the formation of the multicolor image is repeated. Then, when the toner charge amount of each color changes, the amount of developing toner governed by the change also changes, and the ratio of the developing toner amount of each of a plurality of superimposed color toner images changes with time. As a result, the color tone of the formed multicolor image changes with time.

The color toner constituting the developer used for forming a multicolor image has a relatively high charge retention property. Therefore, in the case of continuously forming a multicolor image, the action of the accumulated charges causes aggregation between the toner particles to reduce the fluidity. When the fluidity is lowered, an appropriate amount of toner cannot be stably transported to the developing area by the developer transport carrier, and good developing performance cannot be exhibited. In addition, it causes image defects such as uneven image density and image defects.

Since the development is carried out in a non-contact state with the image forming body, the developability is apt to be hindered by the physical adhesive force between the toner and the carrier, and the developing toner amount is reduced to obtain a sufficient image density. Absent.

Since a plurality of color toner images formed on the image forming body are collectively transferred, the time from the development to the transfer (contact time between the toner and the image forming body) becomes long, In, the electrostatic or physical adhesion of the toner to the image forming body is increased. For this reason, the transfer rate of the color toner image formed by the development onto the transfer body becomes low, which also causes a decrease in the image density.

In order to solve such a problem, an alternating electric field is applied, and further, inorganic fine particles such as silica having an average particle diameter of 70 to 200 nm according to the BET method are uniformly added to the toner by 0.1 to 1.0. A method of adding wt% to reduce the physical adhesive strength has been proposed. (JP-A-62-182775) When this method is used, the developability is certainly improved in the initial stage, but the developability is deteriorated over time due to the burying of the external additive in the toner and the like. Causes a decrease in concentration.

On the other hand, it is possible to reduce the embedding by using an external additive having a large particle diameter which is unlikely to be embedded in the toner due to an impact from the outside. However, since it is an external additive having a large particle size, it is difficult to uniformly adhere to the toner surface and the charge amount distribution is widened, so that the developing property and the transfer property are not stable at the same time.

The laminated organic photoreceptor comprises a charge generating layer (CGL) composed of a binder in which a charge generating substance (CGM) is dispersed on a conductive support, and a binder in which a charge transporting substance (CTM) is dispersed. The CTM on the surface of the photoconductor is decomposed by ozone generated when the surface of the photoconductor is charged as the multicolor image is formed repeatedly. Along with this, since the deteriorated CTM is increased in the surface layer, the charge transporting ability is lowered, and the potential of the surface of the photoreceptor is not lowered during the exposure.
Character reproducibility is poor, and color reproducibility is poor particularly in the formation of multicolor images. In addition, ozone is adsorbed on the deteriorated CTM, which makes it easier to adsorb water, lowering the electric resistance on the surface of the photoconductor and causing image deletion.

Therefore, it is necessary to uniformly polish the surface of the photoconductor to remove the CTM whose surface layer has deteriorated. Therefore, at the time of development, a method in which a developing brush is brought into contact with the surface of the photoconductor to polish the surface of the photoconductor, or a cleaning blade made of a rubber elastic member is brought into pressure contact with the surface of the photoconductor during cleaning,
There is a method of scraping the residual image and polishing the surface of the photoreceptor at the same time.

However, when the mechanical strength of the charge transport layer is inferior, the surface of the photoconductor is greatly worn, and the wear state is non-uniform, so that the chargeability of the photoconductor is uneven and an image defect occurs. Also happens at the same time.

Therefore, when a polycarbonate resin having a bisphenol Z type skeleton having the structure of the following chemical formula 1 (hereinafter abbreviated as BPZ) is used as a binder for CTM, it has a bisphenol A type skeleton having the structure of the following chemical formula 2. As compared with the case where a polycarbonate resin (hereinafter abbreviated as BPA) is used, the mechanical strength is high, the wear of the surface layer of the photoconductor is small, and the scratch resistance is excellent, so that the photoconductor characteristics are stable for a long time. (JP-A-60-172045)

[0014]

[Chemical 1]

(However, in this general formula, R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ : hydrogen atom, halogen atom, substituted or unsubstituted aliphatic group, or Substituted or unsubstituted carbocyclic group, Z: Atom group necessary to form a substituted or unsubstituted carbocycle or a substituted or unsubstituted heterocycle, n: 10 to 1000.)

[0016]

[Chemical 2]

However, in the method of forming a multicolor image in a non-contact manner and transferring them collectively, the developing brush does not come into contact with the image forming body, so that the developing brush has no polishing effect and the cleaning blade on the photosensitive member is rewound once every several times. Because they only come into contact with each other
The surface of the photoconductor is difficult to polish. In addition, when an organic photoconductor using BPZ having high mechanical strength is used, the photoconductor surface is more difficult to be polished, resulting in image defects such as image deletion and blurred characters.

A sufficient solution to this problem has not yet been found.

[0019]

SUMMARY OF THE INVENTION An object of the present invention is to develop an electrostatic latent image formed on a laminated organic photoconductor with a developer and repeatedly form an image, particularly in a non-contact state. It is applied to a multicolor image forming method in which a plurality of color toner images of different colors are formed on the photoconductor by repeating the development by the above, and the plurality of color toner images that are overlapped are collectively transferred. In this case, the change in the amount of developing toner is small and good developability is stably exhibited, and the image density decreases due to insufficient amount of developing toner, the image density decreases due to transfer failure, and the image defect due to the decrease in fluidity occurs. , An improved specific developer capable of stably forming a multicolor image having good image quality and color quality for a long period of time without causing image defects or the like caused by the surface layer of the photoconductor not being polished Used It is to provide an image forming method.

[0020]

DISCLOSURE OF THE INVENTION The inventors of the present invention formed an electrostatic latent image on a laminated type photoreceptor having a charge transport layer on a charge generation layer, and formed the latent image at least a binder resin and a colorant. In a method of forming an image in a non-contact state with respect to the photoconductor, using a toner comprising a toner containing inorganic fine particles added to colored particles containing, and a carrier, the charge transport layer is a binder. As a main component, a polycarbonate resin having a bisphenol Z type skeleton is contained, and the inorganic fine particles of the developer are composed of a single type of inorganic compound. Maximum value of number ratio in the range of 20 to 50 (nm) x
(nm) while having a primary particle size of 60 to 300 (nm) and another number ratio maximum value y (nm), the primary particle size (x + y)
The number ratio of the inorganic fine particles of / 2 (nm) is 10 number% or less, and the ratio of the inorganic fine particles on the small particle size side having the particle size of (x + y) / 2 (nm) is X number%, (x + y) The percentage of the inorganic fine particles on the large particle size side having a particle size of / 2 (nm) or more is Y number%
, The value of “X / Y” is in the range of 0.5 to 2.0,
When the volume average particle diameter of the colored particles is z (nm),
The object can be achieved by using an image forming method characterized in that the value of “z / x” is in the range of 150 to 400 and the volume average particle diameter of the carrier is in the range of 20 to 60 μm. I found it.

[0021]

The present invention will be described in detail below.

A feature of the present invention is that it is composed of a single type of inorganic fine particles, and the number of primary particle diameters (the particle diameters of particles separated into individual unit particles) are two. That is, the inorganic fine particles exhibiting the distribution of are contained as an external additive of the toner, and this toner is used for the image forming body using BPZ as the binder of CTL.

In the present invention, not only the large particle size component which is difficult to adhere to the toner surface but also the small particle size external additive of the same component is mixed to impart fluidity, and also to improve the large particle size. Since the external additive having a small particle diameter component adheres to the portion which cannot be uniformly adhered only by the external additive, the external additive is evenly adhered to the toner surface. As a result, the chargeability of the toner becomes stable, and the burial speed of the external additive is not constant due to the difference in particle size, so that the burial is mitigated and the physical adhesive force between the toner and the carrier is reduced. In addition, it is possible to achieve stable developability and transferability over a long period of time.

When a toner containing a small particle size and a large particle size external additive is mixed in an organic photoconductor using BPZ, a good image quality color tone free from image defects such as image deletion and blurred characters is obtained. It is possible to stably form a multicolor image over a long period of time.

If the range of x is less than 20 nm, the external additive is likely to be buried and stable fluidity cannot be obtained. When it is above 60 nm, a large amount of the external additive having a large particle size is present, so that the fluidity is deteriorated. In addition, since the toner is not evenly attached to the toner surface, the charge amount distribution is widened and fogging is caused. In either case, the developing / transferring property is deteriorated and the fog is increased.

When the range of y is less than 2x, the particle diameters of x and y are close to each other, so that the external additive is likely to be buried, the physical adhesive force is increased, and the developing / transferring property is deteriorated. . In addition, the polishing effect on the surface of the photoconductor is low, and image defects such as image deletion and blurred characters occur. If it is higher than 5x, the external additive is less likely to adhere to the toner surface, so that the external additive is likely to be detached, resulting in in-apparatus contamination, developability, and transferability deterioration.

When the proportion of the inorganic fine particles having a particle diameter of (x + y) / 2 (nm) is larger than 10% by number, the number of external additives having a small particle diameter and a large particle diameter is small, so that fluidity and burial resistance are low. Performance and abradability to the photoreceptor are poor, and sufficient performance cannot be obtained.

If the ratio X / Y of the number% on the small particle size side and the large particle size side of the number primary particle size distribution is less than 0.5, the effect of polishing the surface of the photoconductor is obtained, but the small particle size component is small. Therefore, the decrease in developability and the decrease in transferability due to the decrease in fluidity are caused. When it is higher than 2, the embedding speed of the external additive is increased due to the small amount of particles on the y side, resulting in poor durability. Further, since the large particle diameter component is small, the photoreceptor cannot be sufficiently polished.

Next, when the range of z / x is less than 150, the durability of the toner itself is deteriorated, and the entire toner is pulverized, so that a large amount of toner spent on the carrier is generated. Above 400, the effect of the small particle size component does not appear in terms of the ratio of the carrier diameter to the toner diameter. In either case, the developing / transferring property is deteriorated and the fog is increased.

If the particle size of the carrier is less than 20 μm, there is no great difference from the particle size of the toner, so that the adhesive force between the toner and the carrier increases and carrier scattering occurs. If it is 60 μm or more, in the thin layer forming developing method, the developer brush becomes sparse and the image becomes rough.

When the toner used in the present invention is used in contrast to the organic photoreceptor using BPA as the binder for CTL, BPA has poor mechanical strength and the external additive having a large particle size is used as the photoreceptor. Since the effect of polishing the surface is too high, the surface of the photoconductor is greatly worn and unevenly worn, resulting in image defects.

When an organic photoconductor using BPZ having a mechanical strength higher than that of BPA as a binder of CTL is used, when an external additive containing only a small particle size component having poor polishing ability is added to the toner. The surface of the photoconductor is hardly polished. Further, when an external additive containing only a large particle size component is added, a polishing force on the surface of the photoreceptor can be obtained, but a stable polishing force cannot be obtained because it is not attached uniformly and is easily released.

(Material Example) The binder resin for toner used in the present invention is not particularly limited, and various resins can be used. For example, styrene resin, acrylic resin, styrene / acrylic copolymer resin, polyester resin and the like can be mentioned, but polyester resin is preferable from the viewpoint of burial resistance.

As the coloring agent used in the present invention, various dyes and pigments can be used. The content of the toner is 1.0 to 10.0 wt% so that it is sufficiently colored and does not cause contamination such as separation.
% Is preferred.

If desired, a releasing agent and a charge control agent may be added.

Examples of the inorganic fine particles used in the present invention include fine particles of silica, alumina, titanium oxide, zirconium oxide and the like, and silica fine particles are preferable from the viewpoint of their chargeability and specific gravity. Further, from the viewpoint of environmental dependence, it is preferable that the hydrophobic treatment is performed.

The method for hydrophobizing the silica fine particles will be described below. The method for adjusting the number particle size distribution of the hydrophobic silica fine particles is such that various particle sizes can be obtained by changing the water content and temperature conditions during high temperature hydrolysis of silicon tetrachloride in oxyhydrogen flame. It is possible to obtain the particle size by classifying according to.
Further, as a method of hydrophobizing treatment, it can be obtained by reacting a silanol group of silica with a coupling agent such as dimethylchlorosilane or hexamedyldisilazane.

Further, in order to improve the fluidity, other inorganic fine particles may be added and mixed. Addition amount is 0.01wt% ~ 1
0.0 wt% is preferable. If it is less than 0.01 wt%, the effect is insufficient, and if it is more than 10.0 wt%, the amount of free external additive is large, resulting in in-flight contamination.

The carrier is not particularly limited, and the carrier is composed of magnetic particles such as iron, ferrite, and magnetite, the coating carrier is obtained by coating the surface of magnetic particles with a resin, and the magnetic particles are dispersed and contained in a binder resin. A magnetic substance-dispersed carrier or the like can be used. As the coating resin, a styrene / acrylic copolymer, a silicone resin, a fluorine resin or the like can be used.

The laminated organic photoreceptor comprises a charge generating layer (CGL) composed of a binder in which a charge generating substance (CGM) is dispersed on a conductive support, and a binder in which a charge transporting substance (CTM) is dispersed. A charge transporting layer (CTL) in that order, and the charge generating substance is a phthalocyanine-based pigment,
Antoanthrone pigments, azo pigments, pigments such as indigo pigments, dyes such as pyrylium dyes, or pigments such as cyanine pigments are used, and as the charge transport substance, pyrene, carbazoles such as isopropylcarbazole, hydrazones, Pyrazolines, oxasonyl compounds, thiazole compounds, triarylmethane compounds, polyarylalkanes and the like are used, and as the binder, polyarylate resin, polysulfone resin, polyamide resin, acrylic resin, acrylonitrile resin, Methacrylic resin, vinyl chloride resin, vinyl acetate resin, phenol resin, epoxy resin, polyester resin, alkyd resin, polycarbonate, polyurethane or a copolymer resin containing two or more of repeating units of these resins,
For example, styrene-butadiene copolymer, styrene-acrylonitrile copolymer and the like are used.

(Definition of Measurement Method) [Particle Size of xy] The number particle size distribution of the inorganic fine particles was photographed with a scanning electron microscope at a magnification of 20,000 for each of the 500 inorganic fine particles. The electron micrograph was input to an image analyzer SPICCA (manufactured by Japan Avionics Co., Ltd.), and the particle size of each inorganic fine particle was measured to obtain the image.

[How to obtain X and Y] From the number particle size distribution data obtained by the above method, (x +
The number% less than y) / 2 (nm) is defined as X, and (x + y) / 2 (n
The number% above m) was defined as Y, and the ratio was defined as X / Y.

[Particle size of Z] The particle size distribution is measured with a Coulter counter (manufactured by Coulter Co.).

[Carrier particle size] Microtrac SR
The volume average particle diameter measured by AMK-II (manufactured by Nikkiso Co., Ltd.) was determined.

[0045]

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

Various materials used in this example and comparative examples are as follows.

(Binder resin) Binder: Polyester resin (Pigment) Yellow (Y) pigment: CIPig.YELLOW 17 Magenta (M) pigment: CIPig.RED 122 Cyan (C) pigment: CIPig.BLUE 15: 3 ( Carrier) A carrier in which styrene-acrylic resin is coated on spherical ferrite particles having an average particle diameter of 48 μm (external additive) As the inorganic fine particles, silica fine particles hydrophobized with hexamethyldisilazane were used.

(Layered Organic Photoreceptor) An aluminum roller having a diameter of 180 mm was used as a conductive support, a charge generating layer using bisazo CGM was applied to the surface thereof, and then a structure of the following chemical formula 3 was used as a binder. A photoreceptor coated with a charge transport layer using BPZ and hydrazone-based CTM having C. As a comparative example, a photoreceptor coated with a charge transport layer using BPA having a degree of polymerization of 350 as a binder was used.

[0049]

[Chemical 3]

(Development conditions) A developing bias in which an alternating electric field of 8 KHz and 1.8 KVp-p was superposed was applied with the distance between the developer carrying member and the latent image holding member being 500 μm.

(Cleaning Device) Using a cleaning device provided with a cleaning member such as a cleaning blade placed in pressure contact with the organic photoconductor, the toner not transferred and remaining on the organic photoconductor is cleaned. The pressing force of the cleaning member against the organic photoconductor is preferably 5 to 50 g / cm from the viewpoint of improving the cleaning property. In addition, in the pre-stage of the cleaning step, it is preferable to add a charge eliminating step of eliminating the charge on the surface of the organic photoreceptor in order to facilitate cleaning. This static elimination step is performed by, for example, a static eliminator that causes AC corona discharge.

(Image Forming Process) The outline of the color image forming process using the developer according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a sectional view of a color printer.

In the figure, reference numeral 1 is a photosensitive drum having a photosensitive layer in which a charge generating layer and a charge transporting layer are laminated on an aluminum cylinder, and BPZ is used as a binder in the charge transporting layer and rotated in the arrow direction. . Reference numeral 2 is a charger for uniformly charging the photoconductor drum 1, and reference numeral 3 is a static elimination exposure device before charging.
After the photosensitive drum 1 is uniformly charged, the image exposure means 4 performs image exposure based on the image signal. The image exposure means 4 uses a laser diode (not shown) as a light source,
An optical path is bent by the reflection mirror 42 through a rotating polygon mirror 41, an fθ lens, etc., and scanning is performed, and a latent image is formed by the rotation (sub-scanning) of the photosensitive drum 1. A two-component system composed of a toner such as yellow (Y), magenta (M), cyan (C), and black (Bk) to which the inorganic fine particles peculiar to the present invention are externally added is provided around the periphery of the photosensitive drum 1. A developing device 5 containing a developer is provided. First, the first color (yellow toner) is developed by a developing sleeve that contains a magnet and rotates while holding the developer, and the developer is a layer thickness regulating member. Therefore, the layer is regulated to a layer thickness of 300 to 600 μm on the developing sleeve 51 and is conveyed to the developing area.

The gap between the developing sleeve 51 and the photosensitive drum 1 in the developing area is 0.4 to 1.0 larger than the layer thickness (developer).
mm, an AC bias VAC and a DC bias VDC are applied in the meantime to perform contactless development, and toner images of four colors of Y, M, C and Bk are formed on the photosensitive drum 1 in an overlapping manner. It

This four-color toner image is transferred from the cassette 6 onto the transfer paper fed by the paper feed roller 61 or the like by the action of the transfer pole 7, and is conveyed and fixed to the fixing device 9 by the conveying means 8 to form a color image. Is formed and is discharged to the paper discharge unit 10.

On the other hand, the surface of the photosensitive drum 1 after the transfer is destaticized by the static eliminator 11 and then cleaned by the cleaning blade 13 of the cleaning device 12, and the cleaned toner is conveyed by the screw 14 and the waste toner (not shown) is drawn. Collected in a box. Thus, the photosensitive drum is ready for the next color image formation.

Example 1 A mixture of 100 parts of a binder resin and 3.5 parts of a cyan pigment was melt-kneaded, pulverized and classified to give colored particles having a volume average particle diameter of 8.5 μm, and an external additive. To 100 parts of colored particles, 3.0 parts was added to obtain a toner,
This was mixed with a carrier at a toner concentration of 7% to obtain the developer of Example 1.

(Examples 2 to 10 and Comparative Examples 1 to 9) Table 1 shows the pigment, the particle size of the external additive, the particle size of the colored particles, the z / x ratio and the number particle size distribution of Example 1 as shown in Table 1. Changing Example-2 to 10
And the developers of Comparative Examples-1 to 9 were obtained.

(Comparative Example 10) Charge transport layer (CT
Comparative Example 10 was obtained in the same manner as in Example 1 except that the binder resin of L) was changed to BPA.

[0060]

[Table 1]

(Evaluation Results) The toner shown in Table 1 was mixed with a carrier at a toner concentration of 7% to obtain a developer, which was subjected to a continuous copy test of 30,000 sheets using a Konica 9028 modified machine (fixed modification). It was evaluated by. The evaluation was performed based on the rate of change in the charge amount at the initial stage and after 30,000 sheets, the change in the amount of developing toner, the change in the transfer rate, and the presence or absence of image defects. The results are shown in Table 2.

[0062]

[Table 2]

Charge rate change rate: The charge rate change rate indicates the rate of charge quantity after copying 30,000 sheets when the initial charge quantity is 100. ◇ Development toner amount: unit area (1 cm ² ). Weight of toner developed per hit (mg) ◇ Transfer rate: Ratio of toner on transfer member to total development amount ◇ Image defect was judged by the presence or absence of background fog and image deletion.

1. Ground fog: Absolute density of fog generated on a white background of a copy image after completion of copying 30,000 sheets was measured by an image density measuring device (RD918 type density measuring device manufactured by Macbeth Co.) and judged by a difference from the blank paper density. .

2. Image deletion: Images were observed after the test and classified into the following 4 ranks for judgment.

A: No image deletion is observed. B: Occurrence is seen in a part of the image, but characters can be discriminated. C: Occurrence is seen in a part of the image. Impossible D: Occurred in the entire image However, in Table 2, the background fog is described as “ground”, and the image flow and its degree are described as “image-A, B, C, D”.

(Effects of Embodiment) From Table 2, the image forming method of the embodiment is excellent in all the characteristics such as the rate of change in charge amount, the amount of developing toner, the transfer rate and the image quality. It can be seen that it is not practical because it is bad, especially the background fogging and image deletion occur.

[0068]

As described above, according to the image forming method of the present invention, by using the laminated organic photoreceptor having the characteristic of the binder resin and the improved developer peculiar to the present invention, It is possible to stably provide high image quality without fogging during image formation for a long period of time, and especially when a color image formed by superposing a plurality of color toner images on a photoconductor is formed many times, a developer. It has excellent fluidity and developability, and has excellent transferability of a color toner image formed by superposition to a transfer body, and can provide a stable color image with excellent image quality and color quality for a long period of time. The effects such as being able to be achieved are exhibited.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of an image forming apparatus.

[Explanation of reference numerals] 1 photoconductor drum 2 charging device 3 exposure device for discharging 4 image exposure means 5 developing device 6 cassette 7 transfer electrode 8 transporting means 9 fixing device 12 cleaning device

Claims (1)

[Claims] 1. An electrostatic latent image is formed on a multi-layer photosensitive member having a charge transport layer on a charge generation layer, and the latent image is added with inorganic fine particles to colored particles containing at least a binder resin and a colorant. In an image forming method including a step of developing in a non-contact state with respect to the photoconductor using a developer including a toner and a carrier, the charge transport layer is a polycarbonate resin having a bisphenol Z-type skeleton as a binder. Containing as a main component, the inorganic fine particles of the developer is composed of a single type of inorganic compound, in the number primary particle size distribution curve of the inorganic fine particles, the number in the range of primary particle size 20 ~ 50 (nm) It has a maximum value x (nm) of the ratio and has a primary particle size of 60-
Has another number ratio maximum value y (nm) in the range of 300 (nm),
The number ratio of the inorganic fine particles of primary particle size (x + y) / 2 (nm) is
10% by number or less, the proportion of the inorganic fine particles on the small particle size side having a particle size of (x + y) / 2 (nm) is X% by number, (x +
y) / 2 (nm) or more, the value of "X / Y" is 0.5-
When it is in the range of 2.0 and the volume average particle diameter of the colored particles is z (nm),
An image forming method characterized in that the value of "z / x" is in the range of 150 to 400, and the volume average particle diameter of the carrier is in the range of 20 to 60 m.