JP2854572B2 - Image forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image forming method for developing an electrostatic latent image in an image forming method such as an electrophotographic method or an electrostatic printing method using a developer for developing an electrostatic image.

[0002]

2. Description of the Related Art In electrophotography, an inorganic photoconductive material such as selenium, zinc oxide and cadmium sulfide, or an organic photoconductive material such as anthracene and polyvinyl carbazole is contained in a binder resin as required. An electrostatic latent image is formed on the attenuated photoconductive layer or photosensitive plate, developed with a developer containing toner, transferred to paper or a sheet, and then fixed by a solvent, heat, pressure or heat and pressure. Things.

[0003] In electrophotography, the triboelectric charging property between a toner and a toner carrier during development is important. When the charge amount of the toner is small, the electrostatic attraction between the toner and the toner carrier is weak, so that the toner is easily released from the toner carrier by a slight impact, and fogging occurs on an image. Conversely, if the charge amount is too large, the toner is less likely to be released from the toner carrier during development, not only requiring a strong electric field in the apparatus, but also deteriorating the developability and causing density unevenness. Therefore, in the production of the toner, it is necessary to control the charge amount in a suitable range.

In order to control the charge amount of the toner, a method of adding a small amount of a charge control agent mainly composed of a dye to a mixture of a fixing resin and a colorant is generally employed. It is difficult to uniformly disperse the agent, and there is a problem that the charge amount of the toner itself becomes uneven. This tendency is remarkable in a color toner that does not use a low-resistance colorant such as carbon black or a magnetic material, and is particularly prolonged when the toner particle size is reduced.

On the other hand, recently, a two-component developing system has been reviewed in order to improve the image density of a color image. First, the applicant of the present application has proposed an invention described in JP-A-55-32060 in which an alternating electric field is applied as a device capable of forming a high-quality image by increasing the image density in using a two-component developing system. doing.

[0006] However, there is no discussion on the viewpoint of carrier particles adhering to the image area or any measures for preventing such eyes. In particular, when performing multicolor color copying, unlike a single-color black image, not only a uniform solid image without density unevenness is required, but also a vivid color is required. A duplicate copy will be provided.

The two-component developing system of the alternating electric field application type employs an alternating electric field for achieving an appropriate and stable toner particle adhesion to an image area and an antifogging effect of preventing toner particle adhesion to a non-image area (background area). The main focus was on applying an electric field.

In the two-component developing method, the developer contains at least a toner (containing a colored resin powder and various additives as necessary) and a carrier, and the carrier particles play an important role. In any of the contact development, the loss of the carrier particles due to the adhesion of the carrier particles to the image area has a problem that the charge amount stabilization of the toner particles cannot be achieved. The present inventors have confirmed that carrier particles adhered to the image area disturb the developed image itself, and in particular, lose the vividness of a multicolor image, resulting in a partial decrease in gradation and a decrease in image density. .

As a result of intensive studies conducted by the present inventors, the following findings have been obtained.

When hydrophobic inorganic oxide particles having a high triboelectric charge property obtained by subjecting inorganic oxide particles having a small particle diameter, which is particularly excellent in fluidity-imparting ability, to hydrophobicity treatment, are used as the fluidity improver, the inorganic oxide particles Due to its small diameter, friction with the magnetic particles causes charge-up (excessive charging), especially under low humidity, and adheres firmly to the magnetic particles, making it easier for the magnetic particles to adhere to the latent image carrier. I will. This trend is
As the electric field intensity increases, the developing speed increases, and the sleeve peripheral speed ratio (the ratio of the peripheral speed of the photosensitive drum to the peripheral speed of the sleeve) increases, the magnetic or mechanical regulation of the developer in the developer application unit increases. The stronger the is, the more noticeable. This carrier adhesion is particularly problematic when transparency is required, such as in a multicolor image.

Further, with the widespread use of image forming apparatuses such as color copying machines for electrophotography, the uses thereof have been diversified, and the requirements for image quality have become strict. In the copying of images such as color photographs, catalogs, and maps, it is required to reproduce extremely finely and faithfully without being crushed or interrupted even in minute portions.

Recently, in an image forming apparatus such as an electrophotographic color copying machine using a digital image signal, a latent image is formed by collecting dots of a constant potential, and a solid portion, a halftone portion and a light portion are formed. The part is represented by changing the dot density. However, in a state where the toner particles do not adhere to the dots and the toner particles protrude from the dots, it is not possible to obtain the gradation of the toner image corresponding to the dot density ratio of the black portion and the white portion of the digital latent image. There is a problem. Furthermore, when improving the resolution by reducing the dot size to improve the image quality,
The reproducibility of a latent image formed from minute dots becomes more difficult, and the image tends to be poor in resolution and in particular in gradation of a highlight portion and lack in sharpness.

Although the image quality is good in the initial stage, the image quality may deteriorate while copying or printing out. This phenomenon is caused by the fact that only the easily developed colored resin particles (that is, toner particles) are consumed first while copying or printing out, and the toner particles having poor developability are accumulated and remain in the developing machine. It is thought to happen by.

A number of developers have been proposed for the purpose of improving image quality. JP 5
Japanese Patent Application Laid-Open No. 1-3244 proposes a non-magnetic toner intended to improve the image quality by regulating the particle size distribution. The toner is mainly composed of a toner having a particle size of 8 to 12 μm, and is relatively coarse. At this particle size, it is difficult to form a dense “glue” on a latent image.
The particle size distribution is broad, and the uniformity also tends to be reduced in that the particle size distribution is broad from the characteristic that the number is 20% or more and 5% by number or less. In order to form a clear image using such a coarse toner particle and a toner having a broad particle size distribution, it is necessary to fill the gap between the toner particles by thickly overlapping the toner particles. There is also a problem that it is necessary to increase the image density, and the amount of toner consumption required to obtain a predetermined image density increases.

Japanese Patent Application Laid-Open No. 54-72054 proposes a non-magnetic toner having a sharper distribution than the former, but the size of particles having an intermediate weight is 8.5 to 11.0.
There is still room for improvement as a high-resolution color toner having a coarse particle size of μm and faithfully reproducing a minute dot latent image.

Japanese Unexamined Patent Publication (Kokai) No. 58-129439 proposes a non-magnetic toner having an average particle diameter of 6 to 10 μm and a maximum number of particles of 5 to 8 μm. However, images with low sharpness tend to be formed.

According to the study of the present inventors, toner particles of 5 μm or less clearly reproduce minute dots of a latent image and have a main function of “glue” of dense toner over the entire latent image. It was found that In particular, in the electrostatic latent image on the photoreceptor, due to the concentration of lines of electric force, the contour edge portion (that is, the edge portion of the minute dot portion) has a higher electric field strength than the inside, and the quality of the toner particles collected in this portion is high. Determines the sharpness of the image quality. According to the study of the present inventors, it has been found that the amount of particles having a particle size of 5 μm or less is effective for solving the problem of the gradation property in the highlight portion.

However, if the toner particle size is reduced to 5
Increasing the number of toner particles having a particle size of μm or less increases the cohesiveness of the toner itself, and causes a problem that the mixing property with the carrier such as the magnetic particles is reduced or the fluidity of the toner is reduced.

For the purpose of improving the fluidity, addition of a fluidity improver has been conventionally attempted.
In particular, it has been found that it is difficult to prevent toner scattering or satisfy high image density by balancing the fluidity and charging characteristics of the toner without removing the amount of coarse particles of the toner particles.

[0020]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming method using a developer having a stable triboelectric charging property and, in particular, excellent in preventing adhesion of magnetic particles.

An object of the present invention is to provide an image forming method using a color developer which is excellent in color mixing property, and particularly excellent in light transmittance in an overhead projector (OHP) in a trappen.

An object of the present invention is to provide an image forming method using a developer with less toner scattering.

An object of the present invention is to provide an image forming method using a developer capable of obtaining an image having high image quality and good color reproducibility.

An object of the present invention is to provide an image forming method which uses a developer which maintains good development characteristics even under a low temperature and a low humidity, and has an appropriate development characteristic even under a high temperature and a high humidity. Is to do.

An object of the present invention is to provide an image forming method using a developer having good fluidity.

An object of the present invention is to provide an image forming method using a developer having a high image density, fine line reproducibility, and excellent gradation in a highlight portion.

An object of the present invention is to provide an image forming method using a developer that does not change its performance over a long period of use.

An object of the present invention is to provide an image forming method using a developer having excellent transferability.

An object of the present invention is to provide an image forming method using a developer capable of obtaining a high image density with a small consumption.

An object of the present invention is to provide an image forming method capable of forming a toner image excellent in resolution, gradation of a highlight portion, and fine line reproducibility even in an image forming apparatus using a digital image signal. Things.

[0031]

The above object is achieved by the following constitution of the present invention.

According to the present invention, there is provided a two-component developer having at least a colored resin powder, a fluidity improver and magnetic particles on a surface of a developer carrying member provided opposite to a latent image carrier having an electrostatic latent image. Is supplied, the two-component developer is carried on the surface of the developer carrying member, and the latent electrostatic image of the latent image carrier is developed with the two-component developer in a developing unit to form a visible image. In the image forming method for forming, the colored resin powder is
A latent image having a volume average particle diameter of 4 to 10 μm, a particle size distribution of particles having a particle diameter of 16.0 μm or more in a volume distribution of 1.0% by volume or less, and an electrostatic latent image Has the same triboelectric charge polarity as the potential V (V) of
The magnetic particles have a weight average particle diameter of 35 to 65 μm, and in a weight distribution, a content of particles having a particle diameter of 26 μm or more and less than 35 μm is 1 to 20% by weight, and a particle diameter of 35 μm or more and less than 43 μm. The particles have a particle size distribution in which the content of the particles is 5 to 20% by weight, and the content of the particles having a particle size of 74 μm or more is 2% by weight or less. alternating electric field is formed, an electrostatic latent with respect to the potential of the electrostatic latent image V _L (V), the DC component V _DC alternating electric field having the same polarity as _{V L (V) (V)} , V DC (V) which are Image potential _VL
Potential V _PP M at the point of maximum electric field application opposite to (V)
ax (V) and the maximum charge intensity F (V / μm) of the image area formed by the closest gap G (μm) between the surface of the developer carrying member and the surface of the electrostatic latent image carrier are as follows: 5 ≦ F ≦ 3.5

(Equation 4) Is satisfied, the frequency ν (KHz) of the alternating electric field is 0.8 ≦ ν ≦ 3.0, the relative volume ratio of magnetic particles Q% in the developing section is 15.0 ≦ Q ≦ 45.0, and In the developing section, the relative speed ratio σ between the developer carrying member and the electrostatic image carrier is 1.2 ≦ σ ≦ 2.5 under the condition that the electrostatic latent image is reversibly developed using a two-component developer. And an image forming method.

In the present invention, the two-component developer has (i) a triboelectric charge characteristic in which the absolute value of the triboelectric charge amount is 50 μc / g or more, and has a specific surface area S _A of 80 to 300 m by the BET method. ² / g of a hydrophobic inorganic oxide A based on the colored resin powder, a wt%, and (ii) triboelectric charging characteristics in which the absolute value of the triboelectric charging amount is 20 μc / g or less; specific by surface area S _B is 30 to 200 m ² / g
B) with respect to the colored resin powder
Weight%, and contained as flowable enhancing agent, the hydrophobic inorganic oxide specific surface area of the specific surface area of A S _A and the content a and the hydrophilic inorganic compound B S _B and content b is following condition specific surface area S it is preferable to satisfy the _a ≧ specific surface area S _B content a ≧ content b 0.3 ≦ content a + content b ≦ 1.5.

In the present invention, the hydrophobic inorganic oxide A is preferably a hydrophobic silica fine powder, and the hydrophilic inorganic compound B is preferably an alumina fine powder or a titanium oxide fine powder.

In the present invention, the colored resin powder contains 15 to 40% by number of particles having a particle size of 5 μm or less in the number distribution, and 1% in the volume distribution.
The content of particles having a particle size of 2.7 to 16.0 μm is 0.1 to
5.0 volume%, and has a particle size distribution in which the content of particles having a particle size exceeding 16 μm is 1.0 volume% or less,
In the particle size distribution of the colored resin powder, 6.35 to 10.
The content of particles having a particle size of 1 μm is expressed by the following formula:

[0037]

(Equation 5) [Wherein, V is 6.35 to 10.1 μm in the volume distribution.
Indicates the volume% of particles having a particle size of N, and N indicates the number% of particles having a particle size of 6.35 to 10.1 μm in the number distribution,
d _V indicates the volume average particle size of the colored resin powder].

Further, in the two-component developer of the present invention, the colored resin powder satisfies the above particle size distribution, and the hydrophobic inorganic oxide A and the hydrophilic inorganic compound B satisfy the above conditions. More preferred.

The “colored resin powder” according to the two-component developer of the present invention has a generic meaning of particles as an aggregate of individual colored resin particles.

[0040]

BEST MODE FOR CARRYING OUT THE INVENTION The two-component developer used in the present invention contains at least magnetic particles, colored resin powder, and a fluidity improver. Hereinafter, each constituent material will be described.

(1) Magnetic Particles The magnetic particles used in the present invention include, for example, metals such as iron, nickel, copper, zinc, cobalt, manganese, chromium, rare earth metals, and their alloys, which have been oxidized or not oxidized. Oxides and ferrites can be used.

In the present invention, it is preferable to coat the surface of the magnetic particles with a resin. As the method, a method of dissolving or suspending a resin coating material in a solvent, applying the solution, and attaching the coating material to the magnetic particles is preferable for stabilizing the coating layer.

The material for coating the surface of the magnetic particles varies depending on the colored resin powder material. For example, as a resin for negatively charging the colored resin powder, an aminoacrylate resin, an acrylic resin, or a copolymer of such a resin and a styrene-based resin is preferably located on the positive charging side in the charging series. As the resin that positively charges the colored resin powder, silicone resin, polyester resin, polytetrafluoroethylene, monochlorotrifluoroethylene polymer, and polyvinylidene fluoride are preferable because they are located on the negative side in the charging series.

The most suitable material for the magnetic particles used in the present invention is that 98% by weight or more of the magnetic particles is Cu-Zn-
Fe (composition weight ratio (5 to 20): (5 to 20): (30
To 80)). This is preferable because the surface can be easily smoothed, the charging ability is stabilized, and the coating can be stabilized. As a coating material used for this, an acrylic resin or a styrene-acrylic resin copolymer is used for the positively charged compound, and a silicone resin, polyvinylidene fluoride-polytetrafluoroethylene copolymer is used for the negatively charged compound. It is best to use

The magnetic particles coated with the resin are preferably 1
0 ⁷ Ω · cm, still more preferably in terms of 10 ⁸ Ω · cm, and most preferably behavior of 10 ⁹ ~10 ¹² Ω · those with electrical resistance tribo-imparting cm and in alternating electric field.

The coating amount of the above compound may be appropriately determined so that the magnetic particles satisfy the triboelectric charging characteristics and the electric resistance value between the colored resin powder and the fluidity improver. Generally, the total amount is 0.1 to 30% by weight (preferably 0.3 to 20% by weight) based on the magnetic particles according to the present invention.

The magnetic particles have a weight average particle diameter of 35 to 65 μm.
m, preferably 40 to 60 μm, and the content of magnetic particles having a particle size of 26 μm or more and less than 35 μm in a weight distribution is 1 to 20% by weight, and the content of magnetic particles having a particle size of 35 μm or more and less than 43 μm. Is 5 to 20% by weight,
And the content of magnetic particles having a particle diameter of 74 μm or more is 2% by weight.
A good image can be maintained when:

In the present invention, in order to obtain a good multicolor image, it is preferable to use a sharp-melt colored resin powder. On the other hand, this colored resin powder is very easy to fuse on the latent image carrier.

Once the colored resin powder is fused to the latent image carrier, electric charges are accumulated on the latent image carrier, and the developing bias potential V
Relates dark potential V _D of the _DC and the latent image, | V _DC -V _D | 200
V. When | V _DC −V _D | exceeds 200 V, magnetic particles of 35 μm or less adhere to the latent image carrier, exhibiting an effect of scraping off the fused material on the latent image carrier, and causing image defects. Will be resolved.

At this time, the weight distribution is from 26 μm to 3 μm.
When the content of the magnetic particles having a particle size of less than 5 μm exceeds 20% by weight, | V _DC −V _D | adheres to a portion smaller than 200 V, and problems such as image defects and drum scraping are likely to occur. Become.

On the other hand, when the content of the magnetic particles having a size of 26 μm or more and less than 35 μm is less than 1% by weight, the effect of polishing the magnetic particles tends to be insufficient, and the function of resolving image defects by scraping off the fused material is insufficient. Easy to be.

In the present invention, 26 μm or more to 35 μm
The content of the magnetic particles less than 1 to 20% by weight is as follows.
This is more effective when the volume average particle size of the colored resin powder is 4 to 10 μm. This is because the colored resin powder having a small particle size of 4 to 10 μm has a strong adhesion to the latent image carrier and is more easily fused, but the magnetic particles remove the attached colored resin powder. .

(2) Toner (colored resin powder itself or colored resin powder mixed with an external additive) Colored resin powder Binder resins used for the colored resin powder include polystyrene, poly-p-chlorostyrene, and polyvinyl toluene. ,
Homopolymers of styrene and its substitutes such as styrene-p-chlorostyrene copolymer and styrenevinyltoluene copolymer and copolymers thereof; styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer Copolymers of styrene and acrylate such as styrene-n-butyl acrylate copolymer; styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-n-butyl methacrylate copolymer Copolymers of styrene and methacrylic esters, such as coalescing;
Multi-component copolymer of styrene with acrylic acid ester and methacrylic acid ester; styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-butadiene copolymer, styrene-vinyl methyl ketone copolymer, styrene- Styrene copolymers of styrene and other vinyl monomers such as acrylonitrile indene copolymer, styrene-maleic acid ester copolymer; polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyester, polyamide, epoxy resin, Polyvinyl butyral, polyacrylic acid,
Examples include phenolic resins, aliphatic or alicyclic hydrocarbon resins, petroleum resins, and chlorinated paraffins. These can be used alone or in combination. In particular, low-molecular-weight polyethylene as a binder resin for a toner subjected to a pressure fixing method,
Low molecular weight polypropylene, ethylene-vinyl acetate copolymer, ethylene-acrylate copolymer, higher fatty acid, polyamide resin and polyester resin can be used alone or in combination.

Particularly preferred resins include styrene-acrylate resins and polyester resins.

In particular, the following equation

[0056]

Embedded image

Wherein R is an ethylene or propylene group, x and y are each an integer of 1 or more;
The average value of x + y is 2 to 10. ) As a diol component,
A carboxylic acid component (for example, fumaric acid, maleic acid, maleic anhydride, phthalic acid, terephthalic acid, trimellitic acid, and pyromellitic acid) comprising a divalent or higher carboxylic acid or an acid anhydride thereof or a lower alkyl ester thereof; At least a copolycondensed polyester resin is more preferable since it has sharp melting properties.

In particular, the apparent viscosity at 90 ° C. is 5 × 10 ⁴ in terms of light transmittance with a trapene having a toner image fixed thereon.
５5 × 10 ⁶ poise, preferably 25 × 10 ⁴ to 2 × 10
⁶ poise, more preferably 10 ⁵ to 10 ⁶ poise,
The apparent viscosity at 100 ° C. is 10 ^{4 to} 5 × 10 ⁵ poise,
Preferably it is 10 ^{4 to} 3.0 × 10 ⁵ poise, more preferably 10 ⁴ to 2 × 10 ⁵ poise. When this condition is satisfied, a color OHP having extremely good light transmittance can be obtained, and good results can be obtained in a fixing property, a color mixing property and a high-temperature offset resistance as a full-color toner. It is particularly preferable that the absolute value of the difference between the apparent viscosity P _{1 at} 90 ° C. and the apparent viscosity P _{2 at} 100 ° C. is in the range of 2 × 10 ⁵ <| P ₁ −P ₂ | <4 × 10 ^6. .

Dyes or pigments can be used as colorants. For example, phthalocyanine blue, indaslen blue, peacock blue, permanent red, lake red, rhodamine lake, Hansa yellow, permanent yellow, and benzidine yellow can be used. The content thereof is 12 parts by weight or less, preferably 0.5 to 9 parts by weight with respect to 100 parts by weight of the binder resin so as to reflect the light transmittance of the OHP film sensitively.

In the present invention, the colored resin powder has a volume average particle size of 4 to 10 μm and has a number distribution
The content of particles having a particle size of 5 μm or less is 15 to 40% by number, and the content of particles having a particle size of 12.7 to 16.0 μm is 0.1 to 5.0% by volume in a volume distribution. , 16
It has a particle size distribution in which the content of particles having a particle diameter of at least 1.0 μm is not more than 1.0% by volume, and in the particle size distribution of the colored resin powder, the content of particles having a particle diameter of 6.35 to 10.1 μm is contained. The quantity is

[0061]

(Equation 6)

[Wherein, V represents the volume% of particles having a particle diameter of 6.35 to 10.1 μm, and N represents 6.35 to 10.1 μm.
And d _V represents the volume average particle size of the colored resin powder]. The aggregation degree of the toner comprising the colored resin particles and the external additive is 25% or less, the apparent density is 0.2 to 0.8 g / cm ³ ,
It is preferable that the apparent viscosity is in the range of 10 ^{4 to} 5 × 10 ⁵ poise at 100 ° C. and 5 × 10 ^{4 to} 5 × 10 ⁶ poise at 90 ° C., and the endothermic peak value of DSC is 58 to 72 ° C. .

The particle size distribution of the colored resin powder itself and the particle size distribution of the external additive (toner) of the colored resin powder to which the fine fluidity improver is added are substantially the same.

The colored resin powder having the above particle size distribution is
It can faithfully reproduce the latent image formed on the photoreceptor, and is excellent at reproducing halftone dots and minute dot latent images such as digital images. Give a good image. Furthermore, high image quality can be maintained even when copying or printing out is continued, and even in the case of a high-density image, good development can be performed with less toner consumption than the conventional non-magnetic toner, and it is economical. It also has advantages in terms of performance and miniaturization of the copier or printer body.

The reason why such effects are obtained in the colored resin powder of the present invention is not necessarily clear, but is presumed as follows.

In the colored resin powder of the present invention, 5 μm
One feature is that the colored resin particles having the following particle diameters are 15 to 40% by number. Conventionally, in colored resin powder, colored resin particles of 5 μm or less are difficult to control the charge amount, or impair the fluidity of the toner, as a component that scatters the toner and stains the machine, and as a component that causes image fog. It was thought that aggressive reduction was necessary.

However, according to the study of the present inventors, it has been found that colored resin particles of about 5 μm are indispensable components for forming high-quality images.

For example, the surface potential on the photoreceptor is changed by using a non-magnetic toner composed of a colored resin powder having a particle size distribution ranging from 0.5 μm to 30 μm and a fluidity improver, and a two-component developer having a carrier. Then, from a large development potential contrast in which many colored resin particles are easily developed,
Develop the latent image with the latent image potential changed on the photoreceptor to the halftone, and further develop the latent image of the latent image on the photoreceptor to a latent image of small fine dots where only a few colored resin particles are developed, and collect the developed colored resin particles on the photoreceptor When the particle size distribution of the colored resin powder was measured, it was found that there were many colored resin particles having a size of 8 μm or less, particularly, about 5 μm on the latent image of fine dots. When colored resin particles having a particle size of about 5 μm are smoothly supplied to the development of the latent image on the photoreceptor, the image is faithful to the latent image, and an image with excellent reproducibility can be obtained without protruding from the latent image. Things.

In the colored resin powder of the present invention, 12.
The colored resin particles having a particle size of 7 to 16.0 µm have a particle size of 0.1 to 5.
It is preferably 0% by volume.

This is related to the necessity of the above-mentioned colored resin particles having a particle size of about 5 μm. The colored resin particles having a particle size of 5 μm or less certainly reproduce a latent image of fine dots faithfully. Has the ability, but itself quite cohesive,
Therefore, the fluidity of the colored resin particles or the non-magnetic toner may be impaired.

The present inventors have tried to improve the fluidity by adding the above-mentioned fluidity improver (preferably two or more inorganic oxides) for the purpose of improving the fluidity. The image density,
It was confirmed that the conditions for satisfying the items of toner scattering and fogging were narrow. Therefore, the present inventors have further studied the particle size distribution of the toner. As a result, 15 to 40% by number of colored resin particles having a particle size of 5 μm or less are contained.
Colored resin particles having a particle diameter of 12.7 to 16.0 μm
It has been found that the content of about 5.0% by volume can solve the problem of fluidity and achieve high image quality. 12.
It is considered that the colored resin particles having a particle size of 7 to 16.0 μm have a fluidity controlled at all times to the colored resin particles having a particle size of 5 μm or less, and as a result, copying or printing was continued. Even in this case, a sharp image with high density and excellent resolution and gradation is provided.

Further, for the colored resin particles having a particle diameter of 6.35 to 10.1 μm, the volume% (V) and the number% (N)
And the volume average particle size (d _V )

[0073]

(Equation 8) Is preferably satisfied.

The present inventors have studied the state of the particle size distribution and the development characteristics, and have found that there is a state of existence of the particle size distribution most suitable for achieving the object as shown by the above formula.

When the particle size distribution is adjusted by general air classification, the above value is large, which means that the colored resin particles having a particle size of about 5 μm that faithfully reproduces a minute dot latent image increase, and the above value is small. It can be understood that this means that the colored resin particles having a particle size of about 5 μm are reduced.

Therefore, when d _V is in the range of 4 to 10 μm, preferably 6 to 10 μm and the above relational expression is further satisfied, good fluidity of the toner or developer and faithful latent image reproducibility are achieved. Is done.

For the colored resin particles having a particle size of 16 μm or more, the content is preferably set to 1.0% by volume or less, and as small as possible.

The configuration of the present invention will be described in more detail.

The colored resin particles having a particle size of 5 μm or less are preferably 15 to 40% by number of the total number of particles, and more preferably 2 to 40%.
0 to 35% by number is good. When the content of the colored resin particles having a particle size of 5 μm or less is less than 15% by number, the number of particles effective for high image quality is small. In particular, as the toner is used by continuing copying or printing, the effective coloring resin particle component is reduced. As a result, the balance of the particle size distribution of the toner as shown in the present invention deteriorates, and the image quality gradually decreases. If it exceeds 40% by number, the cohesion between the colored resin particles is liable to occur, resulting in a toner mass larger than the original particle size, resulting in rough image quality, reduced resolution, and an edge portion of the latent image. The density difference between the image and the inside becomes large, and the image tends to be slightly hollow.

The colored resin particles having a particle diameter of 12.7 to 16.0 μm are preferably 0.1 to 5.0% by volume, more preferably 0.2 to 3.0% by volume. If the content is more than 5.0% by volume, the image quality is deteriorated, and more than necessary development and excessive toner adhesion occur, resulting in an increase in toner consumption. On the other hand, if the content is less than 0.1% by volume, the image density will decrease due to the decrease in fluidity.

Colored resin particles having a particle size of 16 μm or more
It is preferably 0% by volume or less, more preferably 0.1% by volume.
6 volume% or less is good. When the content is more than 1.0% by volume, not only does it hinder the reproduction of fine lines, but in the transfer, coarse colored resin particles of 16 μm or more protrude from the thin layer surface of the colored resin particles developed on the photoreceptor. As a result, the delicate state of contact between the photoconductor and the transfer paper via the toner layer is made irregular, causing fluctuations in the transfer conditions and causing a transfer failure image.

The volume average diameter of the colored resin powder is 4 to 10 μm.
m, preferably 6 to 10 μm, more preferably 7 to 9
μm, which cannot be considered separately from the above-mentioned components. Volume average particle size 4
If it is less than μm, in applications where the image area ratio is high, such as a graphic image, there is a problem that the amount of applied toner on the transfer paper is small and the image density is low. This is considered to be due to the same reason as described above for lowering the density inside the edge portion of the latent image. Volume average particle size 1
If it exceeds 0 μm, the resolution is not good, and if the use is continued at best at the beginning of copying, the image quality tends to deteriorate.

The particle size distribution of the colored resin powder can be measured by various methods. In the present invention, the measurement was carried out using a Coulter counter based on the measuring method described later.

Fluidity improver The developer used in the present invention has an absolute value of a charge amount of 100 μc / μm when frictionally charged with the magnetic particles used in the present invention.
g, preferably 30 μc / g or less, more preferably 10 μc / g or less.

Further, it is preferable to use two or more flow improvers.

The first fluidity improver preferably has an absolute value of the charge amount of 30 μc / g or less. In order to impart fluidity, the smaller the particle size of the other fluidity improver is, the more effective the fluidity is with respect to fluidity.
When the specific surface area is measured by the T method, the BE is 30 m ² / g or more.
It is preferable to use a fluidity improver having a T specific surface area.

As the second fluidity improver, the triboelectric charge after reciprocal mixing with the magnetic particles 60 times is Aμt / g, and the triboelectric charge after reciprocating 30,000 times is Bμc / g. Those that satisfy the conditions are good.

0.5 ≦ | B / A | ≦ 2 and 15 ≦ | A | ≦ 100

The case where a hydrophilic inorganic compound B is used as the first fluidity improver and a hydrophobic inorganic oxide A is used as the second fluidity improver will be described below. A powder in which a colored resin powder and a fluidity improver are mixed may be referred to as a toner.

In order to make the present invention more effective, the specific surface area of the hydrophobic inorganic oxide A must be S _A , and the hydrophilic inorganic compound B
When the specific surface area was S _B of, satisfy the following relationship S _A ≧ S _B, respectively a percent by weight so as to satisfy the following formulas A and B with respect to the colored resin powder (colored resin powders reference), b wt% (Based on colored resin powder).

A ≧ b, 0.3 ≦ a + b ≦ 1.5

If a <b or (a + b) is not within the above range, it becomes difficult to balance the chargeability and the fluidity.

Further, when (a + b)> 1.5, the fixing characteristics as toner deteriorates, and in particular, the transparency of the trapene decreases.

The hydrophobic inorganic oxide A used in the present invention has a specific surface area of 80 to 300 m ² / g, and a negatively chargeable inorganic oxide having an absolute value of a triboelectric charge with magnetic particles of 50 to 100 μc / g. Oxides are preferred. As a preferred example, it is more preferable to use a treated silica fine powder obtained by subjecting a silica fine powder generated by vapor-phase oxidation of a silicon halide to a hydrophobic treatment. It is particularly preferable that the treated silica fine powder is obtained by treating the silica fine powder such that the degree of hydrophobicity measured by a methanol titration test shows a value in the range of 30 to 80.

As a method for hydrophobizing, a reaction with silica fine powder
Alternatively, it is provided by a chemical treatment with an organic silicon compound that physically adsorbs.

As a preferred method, silica fine powder produced by vapor phase oxidation of a silicon halide is treated with an organosilicon compound.

Examples of such organosilicon compounds include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allylphenyldichlorosilane, benzyl Dimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, ρ-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilyl acrylate, vinyldimethylacetoxysilane, dimethylethoxy Silane, dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1,3-divinyltetramethyldi Siloxane, 1,3-diphenyltetramethyldisiloxane and 2 to 12 per molecule
There is a dimethylpolysiloxane having hydroxyl groups bonded to Si, each of which has one siloxane unit and the terminal unit is one each. These are used alone or as a mixture of two or more.

The treated silica fine powder has a particle size of 0.1.
It is preferable to use one having a range of 003 to 0.1 μm. Commercial products include Taranox-500 (Talco) and AEROSIL R-972 (Nippon Aerosil).

The following are examples of the hydrophilic inorganic compound B. For example, Al ₂ O ₃ , TiO ₂ , Ge
Metal oxides such as O ₂ , ZrO ₂ , SC ₂ O ₃ , HfO ₂ , carbides such as SiC, TiC, W ₂ C, and Si ₃ N
₄ , nitrides such as Ge ₃ N ₄ are preferred because of their low charging ability.
Among them, Al ₂ O ₃ , TiO ₂ , SC ₂ O ₃ , ZrO ₂ ,
GeO ₂ and HfO ₂ are colorless or white, and when used in a color toner, they are suitable without adversely affecting the color. As the hydrophilic inorganic compound B, a hydrophilic inorganic oxide such as Al ₂ O ₃ or TiO ₂ can be easily produced with a suitable particle size by a gas phase method, and is more preferable. However, it is not preferable that the particles have an extremely square shape or needle shape.

The case where the first fluidity improver is powdery alumina or powdery titanium oxide and the second fluidity improver is hydrophobic silica will be described below. A powder in which a colored resin powder and a fluidity improver are mixed may be referred to as a toner.

In a developer having a non-magnetic colored resin powder, a fluidity-imparting agent and magnetic particles, the colored resin powder has negative chargeability, has a volume average particle size of 4 to 10 μm,
And a flowable imparting agents, specific surface area by BET method specific surface area by alumina and / or the BET method, such as in the range of 30 to 200 m ² / g 30 to 200 m ² /
g of titanium oxide and a hydrophobic silica having a specific surface area of 80 to 300 m ² / g by the BET method are preferably used in combination.

The particle diameter of the colored resin powder used in the present invention is such that the volume average particle diameter is 4 to 10 μm, and 16.0 μm
It is preferable that the colored resin particles having the above particle size have a volume average distribution of 1.0% by volume or less, and the colored resin particles having a particle size of 5.04 μm or less have a number distribution of 35% by number or less. preferable.

Therefore, since the particle diameter of the colored resin powder is small, the toner adheres to the minute electrostatic latent image faithfully, and the toner adherence at the edge of the electrostatic latent image is small. As a result, an image with high resolution and good color reproducibility can be obtained. In particular, in a halftone region in a digital copying machine, a fine latent image is provided, and the effect of the particle size is large, resulting in a good image.

However, since the toner has a small particle diameter, charging tends to be excessive. This can be solved by adding a low-charging substance such as alumina or titanium oxide. The alumina and titanium oxide, for reasons described below, 30 m ² / g (particle size about 40mμ) ~200m ² /
g (particle diameter: about 12 mμ), more preferably 80 m ² / g (particle diameter: about 25 mμ) to 150 m ^2.
/ G (particle size about 15 mμ).

For example, B larger than 200 m ² / g
Alumina and titanium oxide having an ET specific surface area have sufficient fluidity, but tend to deteriorate. Deterioration appears as a phenomenon in which the amount of charge changes greatly or the fluidity of the developer deteriorates when copying runs continuously with little toner consumption.

In the case of alumina or titanium oxide having a BET specific surface area smaller than 30 m ² / g, it is difficult to obtain sufficient fluidity even when used in combination with another fluidity imparting agent. Dispersion of the fluidity-imparting agent tends to be insufficient, and fogging tends to occur in images.

Assuming that the BET specific surface area of the alumina or titanium oxide is S _B , the fluidity becomes insufficient when only alumina and titanium oxide are used in the range of 30 ≦ S _B ≦ 100 m ² / g. It is necessary to use in combination with hydrophobic silica having a high effect of giving. Further, 100 <S _B ≦ 200 m ²
In the range of / g, the surface of the colored resin particles is uniformly and densely covered, so that when only low-charged alumina or titanium oxide is used, the charge amount may be too low. Therefore, it is necessary to use in combination with negatively charged hydrophobic silica.

As described above, in terms of negative chargeability and fluidity-imparting ability, hydrophobic silica functions to supplement alumina and titanium oxide. Therefore, if the BET specific surface area of the hydrophobic silica is not less than 80 m ² / g, a sufficient function cannot be obtained. It is more preferably 150 m ² / g or more.

In the present invention, by using alumina or titanium oxide in combination with hydrophobic silica, not only the above-described control of the charge amount but also other adverse effects associated with the reduction in the particle size of the colored resin powder can be improved. You.

When the particle size of the colored resin powder is reduced, Coulomb force and Van der Waals force acting between the colored resin particles are reduced.
Since the strength becomes relatively stronger than the gravity and the inertial force, the adhesive force between the colored resin particles is increased, and the aggregate of the colored resin particles is easily generated. On the other hand, alumina and titanium oxide weaken the adhesive force between the colored resin particles due to charging, and make it difficult to generate aggregates of the colored resin particles. When the particle size of the colored resin powder is reduced, the number of contact points between the colored resin powder and the carrier increases, and carrier spent tends to occur. On the other hand, alumina and titanium oxide also serve as good spacers between the carrier and the colored resin particles and exert a good effect.

Furthermore, when alumina, titanium oxide and hydrophobic silica are used in combination, each of them becomes more effective than when each is used alone.
The fluidity of the toner becomes good, and the mixing property of the developer and the toner cleaning property become good.

Charge Control Agent A charge control agent may be added to the colored resin powder of the present invention in order to stabilize the charge characteristics. At that time, a colorless or light-colored charge control agent that does not affect the color tone of the colored resin particles is preferable. In the present invention, when a negative charge controlling agent is used, the present invention becomes more effective. In this case, the negative charge controlling agent includes, for example, a metal complex of an alkyl-substituted salicylic acid (for example, chromium of di-tert-butylsalicylic acid). Complex or zinc complex).
When the negative charge control agent is added to the colored resin particles, it is added in an amount of 0.1 to 10 parts by weight, preferably 0.5 to 8 parts by weight, based on 100 parts by weight of the binder resin.

In the present invention, the mixing ratio of the magnetic particles and the toner (or the colored resin powder) is 2.0% by weight to 12% by weight, preferably 3% by weight, as the toner concentration in the developer.
Good results are obtained when the content is between 9% by weight and 9% by weight. If the toner density is less than 2.0% by weight, the image density becomes low,
If it exceeds 2% by weight, fog and scattering in the machine tend to increase, and the useful life of the developer tends to be shortened.

In the present invention, a metal salt of a fatty acid such as zinc stearate, aluminum stearate or a fine powder of a fluorine-containing polymer such as polytetrafluoroethylene, polyvinylidene fluoride and tetrafluoroethylene-vinylidene fluoride may be used as a lubricant. A fine powder of a ride copolymer, an abrasive such as cerium oxide or silicon carbide, or a conductivity-imparting agent such as tin oxide or zinc oxide may be added.

To prepare the colored resin powder according to the present invention, a thermoplastic resin and a pigment or dye as a colorant, a charge control agent and other additives, if necessary, are thoroughly mixed by a mixer such as a ball mill. Then, using a hot kneader such as a heating roll, kneader, or extruder, melt or knead and knead the resin to dissolve or disperse the pigments or dyes in the resin, and solidify by cooling and solidifying. And strict classification can be performed to obtain the colored resin powder according to the present invention.

Next, an example of a developing device that can carry out the image forming method of the present invention will be described with reference to FIG.

The latent image carrier 1 is made of an insulating drum for electrostatic recording or α-Se, Cds, ZnO ₂ , OPC, α-Si
And a photosensitive drum or a photosensitive belt having a photoconductive insulating material layer as described above. The latent image carrier 1 is rotated in the direction of arrow a by a driving device (not shown). Reference numeral 22 denotes a developing sleeve that is close to or in contact with the latent image carrier 1, and is made of, for example, a nonmagnetic material such as aluminum or SUS316. The developing sleeve 22 has a horizontally long opening formed in the longitudinal direction of the container on the lower left wall of the developing container 36, the substantially right half circumferential surface of which projects into the container 36, the left substantially half circumferential surface is exposed outside the container, and the developing sleeve 22 is rotatably supported. And is driven to rotate in the direction of arrow b.

Reference numeral 23 denotes a fixed permanent magnet (magnet) as a fixed magnetic field generating means inserted into the developing sleeve 22 and positioned and held in the position and orientation shown in the figure.
Even when the magnet 2 is driven to rotate, the magnet 23 is fixedly held at the position and posture shown in the figure. The magnet 23 has four magnetic poles: an N-pole 23a, an S-pole 23b, an N-pole 23c, and an S-pole 23d. The magnet 23 may be provided with an electromagnet instead of a permanent magnet.

Reference numeral 24 denotes a base fixed to the side wall of the container on the upper edge side of the developer supply opening on which the developing sleeve 22 is disposed, and the front end side is projected to the inside of the container 36 from the position of the upper edge of the opening. A non-magnetic blade as a developer regulating member disposed along the longitudinal direction, for example, a SUS 316 formed by bending a SUS 316 into a cross-shaped cross section.

Reference numeral 26 denotes a magnetic particle limiting member whose upper surface is in contact with the lower surface of the non-magnetic blade 24 and whose front end surface is a developer guide surface 261. The portion constituted by the non-magnetic blade 24 and the magnetic particle limiting member 26 is a regulating portion.

Reference numeral 27 denotes magnetic particles having a resistance value of 10 ⁷ Ω ·
cm or more, preferably 10 ⁸ Ω · cm or more, and more preferably 10 ⁹ to 10 ¹² Ω · cm. Ferrite particles (maximum magnetization of 55 to 75 emu / g) coated with a resin can be used. 37 is a non-magnetic toner. Reference numeral 40 denotes a sealing member that seals the toner accumulated in the lower portion of the developing container 36, has elasticity, is bent in the rotation direction of the sleeve 22, and elastically presses the surface side of the sleeve 22.
The seal member 40 has an end on the downstream side in the sleeve rotation direction in a contact area with the sleeve so as to allow the developer to enter the inside of the container.

Reference numeral 30 denotes a scattering prevention electrode plate for applying a voltage of the same polarity as that of the floating developer generated in the developing step to adhere to the photoreceptor side to prevent scattering.

50 is a toner density detection sensor (not shown)
Is a toner supply roller that operates according to the output obtained from the toner supply roller. As the sensor, the developer volume detection method,
A piezoelectric element, an inductance change detection element, an antenna system using an alternating bias, and a system for detecting optical density can be used. The non-magnetic toner 37 is supplied by stopping the rotation of the roller. The fresh developer supplied with the toner 37 is mixed and stirred while being conveyed by the screw 51. Accordingly, a tribo is applied to the replenished toner during this conveyance. Reference numeral 53 denotes a partition plate, which is cut out at both ends in the longitudinal direction of the developing device. At this portion, the fresh developer conveyed by the screw 61 is delivered to the screw 62.

The S magnetic pole 23d is a transport pole. The collected developer after the development is collected in the container, and the developer in the container is further transported to the regulating section.

In the vicinity of 23d, the fresh developer transported by the screw 52 provided close to the sleeve and the recovered developer after development are exchanged.

Numeral 54 denotes a conveying screw for making the amount of developer uniform in the axial direction of the developing sleeve.

The distance d ₂ between the end of the non-magnetic blade 24 and the surface of the developing sleeve 22 is 100 to 900 μm, preferably 150 to 800 μm. This distance is 100 μm
If the particle size is smaller, the magnetic particles to be described later are clogged in the meantime, and the developer layer is likely to be uneven, and the developer necessary for good development cannot be applied, so that only a developed image having a small density and a lot of unevenness can be obtained. There are disadvantages that cannot be achieved. d ₂ is preferably 400 μm or more in order to prevent non-uniform coating (so-called blade jam) due to unnecessary particles mixed in the developer. If it is larger than 900 μm, the developing sleeve 22
The amount of the developer applied thereon increases, so that the predetermined developer layer thickness cannot be regulated, the magnetic particles adhere to the latent image carrier increases, and the developer circulation described later, There is a disadvantage that the development regulation is weakened and the toner tribo is insufficient and fogging is likely to occur.

The angle θl is -5 ° to 35 °, preferably 0 °
° to 25 °. When θl <−5 °, the developer thin layer formed by the magnetic force, mirroring force, cohesion, etc. acting on the developer becomes sparse and uneven, and when θ> 35 °, the non-magnetic blade becomes The amount of developer applied increases, and it is difficult to obtain a predetermined amount of developer.

In this magnetic particle layer, the sleeve 22 has an arrow b
Even when the sleeve 22 is driven to rotate in the direction, the movement becomes slower as the distance from the sleeve surface increases due to the balance between the magnetic force and the restraining force based on gravity and the conveying force in the moving direction of the sleeve 22. Of course, some fall under the influence of gravity.

Accordingly, by appropriately selecting the arrangement positions of the magnetic poles 23a and 23d and the fluidity and magnetic characteristics of the magnetic particles 27, the magnetic particle layer is conveyed toward the magnetic pole 23a closer to the sleeve to form a moving layer. Due to the movement of the magnetic particles, the magnetic particles are conveyed to the developing area with the rotation of the sleeve 22 and subjected to development.

FIGS. 2 and 3 illustrate the main part of the developing method according to the present invention, in which a developer having colored resin particles and magnetic particles charged to the opposite polarity to the colored resin particles is used.
An electrostatic image carrier as an electrostatic image carrier, and a developing unit (the closest gap G) formed by the developer carrier for carrying the developer.
(Μm)).

The alternating electric field in FIG. 2 has a rectangular wave shape. In this waveform, in the case of normal development, the potential V _PP Max (V) at the maximum electric field application point referred to in the present invention indicates that the electrostatic image is negative (V _D
(V)), the maximum on the positive side of the rectangular wave (upper in the figure)
It becomes a point and the background potential becomes _VL (V). In the case of reversal development with this waveform, as shown in FIG.
_L (V), the maximum electric field application point is the lower point in the figure, and the background potential is V _D (V).

Since the magnetic particles adhere to the image area and disturb the developed image, a development method capable of preventing the adhesion of the magnetic particles to the image area was investigated. Since the present invention is a reversal development, for example, the background portion potential V _D -
600 (V), the electrostatic image potential _VL is -250 (V),
The DC component _VDC for preventing toner particles from adhering to the background portion is set to -490 (V).

The present inventors have conducted experiments on the assumption of a large number of development method patterns. As a result, many of them have found that magnetic particles have adhered to the image area, At the same time, it was also clarified that the tonality tended to decrease and the image density also decreased.

The present inventors have further conducted experiments and studies. As a result of the magnetic particles adhering to the image area, the maximum electric field strength for causing a large amount of toner particles to adhere to the image area was reversed. It has been found that there is a problem peculiar to the two-component type developer that causes the adhesion of the toner. Therefore, when a number of experiments and considerations were added to decrease the maximum electric field strength from the high value as in the conventional case, the condition was reached that the adhesion of the magnetic particles could be greatly reduced. Although the prevention of the adhesion of the magnetic particles was originally carried out to improve the image gradation, it was also found that if the maximum electric field intensity was too weak, the image gradation deteriorated rather and a sufficient density could not be obtained.

FIG. 3 will help to easily understand the reversal developing method in the present invention.

The maximum electric field intensity F (V / μm) of the image portion is
The potential V _L (V) of the electrostatic image and the DC component V of the alternating electric field
_DC (V), the potential V _PP Max (V) at the maximum electric field application point located on the opposite side of the potential V _L (V) of the electrostatic image with respect to the DC component V _DC (V) of the alternating electric field, and the developer carrying Equation formed by the closest gap G (μm) between the member surface and the surface of the electrostatic image carrier,

[0138]

(Equation 8) In the range of 1.5 ≦ F ≦ 3.5, there was no adhesion of magnetic particles and the gradation was good. If F> 3.5, the magnetic particles adhere to the image portion at a uniform ratio, the overall image transparency tends to be impaired, and image unevenness during transfer tends to occur.

On the other hand, when F <1.5, the magnetic particles adhere well, but the sharpness of the line is impaired and the image density tends to decrease. Preferably, 1.5 ≦ F
≦ 3.5, more preferably 2.0 <F ≦ 3.0.

The developing system in which the developer is reciprocated by such an AC electric field has a high developing efficiency, and is effective when a large image area and a large amount of toner are used, such as a full-color copy. However, since the developer reciprocates,
The colored resin particles and the magnetic particles are easily separated from each other, and toner is easily scattered. Therefore, it is desired that the developer has a function of reducing toner scattering.

However, conventionally, when the volume average diameter of the colored resin powder is small, it is difficult to achieve both the toner scattering and the image density because the environmental difference in the charge amount of the developer is large. For example, if toner scattering in an environment with a low charge amount becomes a problem, toner scattering can be prevented by increasing the charge amount. However, at the same time, the charge amount is increased even in an environment where the charge amount is originally high, so that an image having a low image density has an adverse effect of being further reduced,
It was difficult to achieve both. However, in the present invention, since the difference in the environment of the charge amount is small, it is easy to control the charge amount to be compatible with the toner scattering and the image density in various environments.

The adhesion of the magnetic particles other than the adhesion of the colored resin particles to the image area occurs on the non-image area. In the present invention, the prevention of the magnetic particles from adhering to the non-image area is also preferable for the reasons described above. It will be. This condition is within a range in which the colored resin particles do not adhere to the non-image portion, and the DC component V _DC (V) with respect to the non-image portion potential _VL (V) is the following condition even if _VL is variable. Good to meet.

50 ≦ | V _DC −V _L | ≦ 200. Since the non-image portion potential may fluctuate depending on the environment, this value is preferably 150 (V) or less in order to increase reliability.

Further, as a preferable condition, it is preferable that the frequency ν (KHz) of the alternating electric field satisfies 0.8 ≦ ν ≦ 3.0. Preferably, 0.8 to 2.21 is good.
If it is less than 0.8 KHz, fog increases, and if it exceeds 3.0 KHz, the sharpness and gradation of the line deteriorate.

In the present invention, in the developing method, the developer layer may be in non-contact or in contact with the latent image holding member in the developing section in a state where no alternating electric field is applied.

Further, such a combination of the developing method and the developer is also a good combination in the following points.

The fluidity improver having a weak charging ability in the developer has a weak adhesion to the latent image of the photoreceptor. Therefore, in the developing method in which an alternating electric field is not applied, the flow improver is not consumed by the development, and is not consumed in the developing device. Tends to accumulate. However, according to the developing method of the present invention, the chance of contact with the photoreceptor is greatly increased, and such a tendency can be eliminated.

Here, the relative volume ratio that defines the amount of the developer conveyed to the developing area in the developing device and the developer having the above configuration will be described. The relative volume ratio is the developing unit,
That is, the value is defined in a portion where the toner is transferred or supplied from the sleeve 22 to the photosensitive drum 1. The application amount M (g / g) of the developer (mixture: at the time of non-springing) per unit area of the surface of the sleeve 22 in the developing section is used.
cm ² ), the height h (cm) of the developing space, the true density ρ (g / cm ³ ) of the magnetic particles, and the weight ratio C / (T + C) (%) of the carrier particles on the sleeve surface (where C is the carrier). And T is the weight of the toner), and the relative speed ratio σ between the sleeve 22 and the photoconductor 1 and is represented by the following equation.

Relative volume ratio Q (%) = M / h × 1 / ρ × C / (T + C) × σ × 100

The relative volume ratio Q depends on the developer transportability and charging characteristics or the configuration of the developing device, in particular, the arrangement of the magnetic poles of the magnet roller 23, the strength of the magnetic poles, the shape of the developer regulating member 26, and the non-magnetic property. largely changed by a distance d ₂ between the end and the sleeve 22 surface of the blade 24, a copy image, in particular a great influence on the image density.

The present inventors studied the relationship between the relative rest ratio Q and the image density under various experimental conditions, and found that the relative volume ratio Q
In the range of 15.0 ≦ Q ≦ 45.0 (%) (more preferably, 15.0 ≦ Q ≦ 28.0).
(%)), It was found that a good color image could be obtained. Further, it has been found that when Q is within the above range, a stable image can be obtained even when the atmosphere environment changes.

The above condition proposed as a preferred developing method in the present invention is based on the assumption that the image density and the image quality do not change monotonously with the amount of the developer applied on the sleeve 22 and the increase or decrease of the developing space. The relative volume ratio Q as a temporal abundance of magnetic particles in the developing space (amount of magnetic particles passing through the developing unit per unit time) is 15.0 to 45.0% (preferably 15.0 to 25.0%).
(8.0%), a sufficient and stable image density can be obtained, and even if it is less than 15.0% or more than 45.0%, a slight decrease in image density and image quality unfavorable for color image copying occurs. Further, it is based on the finding that sleeve ghost and fogging do not occur when the image quality is within the above numerical value range.

When the relative volume ratio is in the range of 15.0 to 45.0%, the spikes formed on the surface of the sleeve 22 are formed in a sparse state to a desirable extent, and both the sleeve 22 and the spikes on the spikes are not sparse. Since the magnetic toner (colored resin particles) 102 is sufficiently opened to the photosensitive drum 1 and the non-magnetic toner 102 on the sleeve also undergoes a period transition by an alternating electric field, almost all the non-magnetic toner 102 can be consumed for development. As a result, a high development efficiency (a ratio of the non-magnetic toner 102 present in the developing unit that can be consumed for development) and a high image density can be obtained. Preferably, a small but intense spike vibration is caused, whereby the magnetic particles 27 and the non-magnetic toner 102 adhering to the sleeve 22 are loosened. In any case, it is possible to prevent the occurrence of uneven sweep and ghost images as in the case of a magnetic brush. Further, the friction of the magnetic particles 27 and the non-magnetic toner 102 becomes active due to the vibration of the ears, so that the frictional charging of the non-magnetic toner 102 can be improved, and the occurrence of fog can be prevented.

The relative volume ratio Q is preferably set within the above range, but more preferably, the relative speed ratio σ
Is preferably set to 1.2 <σ <2.5. The relative speed ratio is represented by the following equation, where a is the peripheral speed of the sleeve and b is the peripheral speed of the photoconductor.

Σ = a / b

By setting σ> 1.2, the development efficiency can be increased. However, when σ> 2.5, the density of the copied image in the solid portion becomes non-uniform, and so-called “bleeding” tends to occur.

Hereinafter, the respective measuring methods (1) to (8) relating to the characteristic values of the developer used in the present invention will be described.

(1) Particle size distribution measurement: Coulter counter TA-II type (manufactured by Coulter Inc.) was used as a measuring device, and an interface (manufactured by Nikkaki) for outputting a number average distribution and a volume average distribution, and CX-
1 Connect a personal computer (manufactured by Canon Inc.) and prepare a 1% NaCl aqueous solution using primary grade sodium chloride as an electrolyte.

The measuring method is as follows.
In 50 ml, 0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant, and 0.5 to 50 mg of a measurement sample is further added.

The electrolyte in which the sample was suspended was subjected to a dispersion treatment for about 1 to 3 minutes by an ultrasonic disperser, and the particle size distribution of particles of 2 to 40 μm was measured by the Coulter Counter TA-II using an aperture of 100 μm. Is measured to obtain a volume average distribution and a number average distribution.

From the obtained volume average distribution and number average distribution, the volume average particle size and the number average
Values such as the ratio of the colored resin particles having a particle size of 1 μm or less and the ratio of the colored resin particles having a particle size of 16.0 μm or more in the volume average distribution are obtained.

(2) Measurement of triboelectric charge amount: FIG. 4 is an explanatory view of a triboelectric charge amount measuring device. First, a mixture of particles to be measured and magnetic particles used as a developer is prepared. The mixing ratio is 5 parts by weight with respect to 95 parts by weight of the magnetic particles in the case of the colored resin powder, and 2 parts by weight with respect to 98 parts by weight of the magnetic particles in the case of the fluidity imparting agent.

As the magnetic particles used for the measurement, the magnetic particles used for the developer used in the present invention are used. For example, ferrite particles coated with a styrene-based resin,
0% by weight or more (more preferably 75 to 95% by weight), and 0.2 to 0.7% by weight of styrene-acrylic acid 2-
One coated with an ethylhexyl-methyl methacrylate copolymer may be mentioned.

The particles to be measured and the magnetic particles are placed in a measurement environment (23 ° C., 60% RH), allowed to stand for at least 12 hours, then put in a polyethylene bottle, mixed well, and stirred (60 reciprocal mixings). ).

A polyethylene bottle having a volume of 100 ml is used, and a turbula mixer (3 times / second) is used for stirring.

Next, a conductive screen 1 of 500 mesh (which can be appropriately changed to a size that does not allow magnetic particles to pass) is provided at the bottom.
A mixture of particles and magnetic particles whose frictional charge is to be measured is placed in a metal measurement container 112 having a metal cover 13 and a metal lid 114 is provided. At this time, the weight of the entire measurement container 112 is weighed and is defined as W ₁ (g). Next, in the suction device 111 (at least a portion in contact with the measurement container 112 is an insulator),
The air is suctioned from the suction port 117 and the air volume control valve 116 is adjusted to adjust the pressure of the vacuum gauge 115 to 250 mmAq. In this state, suction is sufficiently performed (about 2 minutes) to remove toner by suction.
The potential of the electrometer 119 at this time is set to V (volt).
Here, reference numeral 118 denotes a capacitor having a capacity of C (μF). Also, the weight of the whole measuring container after suction is weighed and W
₂ (g). This triboelectric charge amount T (μc / g) is calculated as in the following equation.

[0167]

(Equation 9)

(3) Measurement of apparent viscosity: A flow tester CFT-500 type (manufactured by Shimadzu Corporation) is used. Approximately 1.0 to 1.5 g of 60 mesh pass sample
Weigh. Using a molding machine, this is 100 kg / cm ²
Press for 1 minute with load.

The pressurized sample is subjected to a flow tester measurement under the following conditions under normal temperature and normal humidity (temperature about 20 to 30 ° C., humidity 30 to 70% RH) to obtain a temperature-apparent viscosity curve. From the obtained smooth curve, the apparent viscosities at 90 ° C. and 100 ° C. are determined and defined as the apparent viscosity with respect to the temperature of the sample.

RATE TEMP 6.0 D / M (° C./min) SET TEMP 70.0 DEG (° C.) MAX TEMP 200.0 DEG INTERVAL 3.0 DEG PREHEAT 300.0 SEC (sec) LOAD 20.0 KGF ( kg) DIE (DIA) 1.0 MM (mm) DIE (LENG) 1.0 MM PLUNGER 1.0 CM ² (cm ² )

(4) Measurement of Resistance Value of Magnetic Particles Using a sandwich type cell having a measuring electrode area of 4 cm ² and an electrode spacing of 0.4 cm, an applied voltage E ( V / cm), the current flowing through the circuit is measured, and the resistance value of the magnetic particles is obtained.

(5) Measurement of agglomeration degree: The degree of agglomeration is used as a means of measuring the flow characteristics of a sample (colored resin powder having an external additive). Judge is bad.

As a measuring apparatus, a powder tester (manufactured by Hosokawa Micron Co., Ltd.) is used.

As a measuring method, 200 mesh, 100 mesh, and 60 mesh screens are placed on the shaking table in a narrow order of opening, that is, in order of 200 mesh, 100 mesh, and 60 mesh screen so that the 60 mesh screen is at the top. Set again.

An accurately weighed sample (5 g) was added to the set 60-mesh screen, and the input voltage to the shaking table was increased by 2%.
1.7V and the amplitude of the shaking table at that time is 60V.
Adjust to fall within the range of ９０90μ (rheostat scale about 2.5) and apply vibration for about 15 seconds. Thereafter, the weight of the sample remaining on each sieve is measured to obtain the degree of aggregation based on the following equation.

[0176]

(Equation 10)

The sample was prepared for about 1 hour at 23 ° C. and 60% RH.
The measurement environment is 23 ℃, 60%
RH.

(6) Measurement of hydrophobicity: The methanol titration test is an experimental test for confirming the hydrophobicity of fine silica powder having a hydrophobic surface.

The "methanol titration test" defined herein for evaluating the degree of hydrophobicity of the treated silica fine powder is carried out as follows. 0.2 g of the test silica fine powder is added to 50 ml of water in a 250 ml Erlenmeyer flask. Methanol is titrated from the burette until all of the silica is wetted. At this time, the solution in the flask is constantly stirred with a magnetic stirrer. The end point is observed by the suspension of the whole amount of the fine silica powder in the liquid, and the degree of hydrophobicity is expressed as the percentage of methanol in the liquid mixture of methanol and water at the end point.

(7) Measurement of apparent density: The apparent density is measured using a powder tester (manufactured by Hosokawa Micron). For the measurement, a 60-mesh screen is set on a vibrating table, and a cup for measuring apparent density (content: 100 cc) whose weight has been measured in advance is placed immediately below.

Next, the vibration is started by adjusting the rheostat scale to 2.0. The measurement sample is gently discharged from the vibrating top of the 60-mesh screen so as to enter the measurement cup.

When the cup is filled with the sample, the vibration is stopped, the upper surface of the cup of the pile is cut off with a blade, and the balance is accurately weighed with a balance.

Since the measuring cup has a content of 100 cc, the apparent density (g / cm ³ ) = the weight of the sample ÷ 1
00 can be obtained.

The sample was prepared for about 1 hour at 23 ° C. and 60% RH.
The measurement environment was 23 ° C and 60%
RH.

(8) Measurement of Endothermic Peak Value by DSC In the present invention, the measurement is carried out using a differential thermal analysis measuring device (DSC measuring device), DSC-7 (manufactured by PerkinElmer).

The measurement sample is 5 to 20 mg, preferably 10
Weigh the mg precisely.

This was put in an aluminum pan, and an empty aluminum pan was used as a reference.
The measurement is performed at a temperature rising rate of 10 ° C./min under normal temperature and normal humidity between 00 ° C.

The temperature at which the endothermic peak of the main peak in the temperature range of 40 ° C. to 100 ° C. is obtained in the process of raising the temperature is defined as the endothermic peak value of the present invention.

[0189]

EXAMPLES <Example 1> 100 parts by weight of polyester resin (weight average molecular weight (Mw) 17000, number average molecular weight (Mn) 3500) obtained by condensing propoxylated bisphenol and fumaric acid 5 parts by weight of phthalocyanine pigment Parts-Chromium complex salt of di-tert-butylsalicylic acid 4 parts by weight

The above materials were sufficiently premixed with a Henschel mixer, melt-kneaded at least twice with a three-roll mill, cooled, and cooled to a particle size of about 1 with a hammer mill.
It was coarsely ground to about 2 mm. Next, it was pulverized by a pulverizer using an air jet method. Further, the obtained finely pulverized product was classified by a multi-segmentation classifier to have a volume average particle size of 8.3.
25% by number of particles having a particle diameter of 5 μm or less in the number distribution, 46% by number of particles having a particle diameter of 6.35 to 10.1 μm in the number distribution, and 6.35 to 35% in the volume distribution.
11. 67% by volume of particles having a particle size of 10.1 μm;
1.6% by volume of particles having a particle size of 7 to 16.0 μm,
Particles having a particle size exceeding 16.0 μm yielded a negatively-chargeable cyan colored resin powder having a cyan color of 0%.

The above colored resin particles (100 parts by weight) and BET
-3 μm with a specific surface area of 100 m ² / g by the method
0.3 parts by weight (approximately 0.3% by weight) of c / g alumina fine powder, a specific surface area of 250 m ² / g by the BET method, and a charge amount obtained by hydrophobizing with hexamethyldisilazane.
0.5 parts by weight (about 0.5% by weight) of 80 μc / g silica fine powder was mixed to obtain a cyan toner.

The apparent viscosity of this cyan toner was 6.00 × 10 ⁵ poise at 90 ° C., 1.1 × 10 ⁴ poise at 100 ° C., the apparent density was 0.35 g / cm ³ ,
The endothermic peak at C was 67.2 ° C. Table 1 shows the physical property values of the toner, and Table 2 shows the physical property values of the fluidity improver.

6 parts by weight of the cyan toner and styrene-
The surface was coated (0.5% by weight of coating weight) with a methyl methacrylate-2-ethylhexyl acrylate copolymer (copolymerization weight ratio = 45: 35: 20; weight average molecular weight (Mw) 5000; number average molecular weight 2000). Cu (15) -Zn
(15) -Fe (70) ferrite particles (electrical resistance value 10 ¹⁰ Ω · cm; weight average particle diameter 52 μm; particle diameter 10 μm
The content of the following magnetic particles is substantially 0% by weight,
3% by weight of magnetic particles having a particle size of less than μm, 9% by weight of magnetic particles having a particle size of 26 μm or more and less than 35 μm, and a combined amount of magnetic particles having a particle size of 35 μm or more and less than 43 μm 1
2% by weight, content of magnetic particles having a particle size of 74 μm or more 0.1
(% By weight) was mixed with 94 parts by weight to prepare a two-component developer.

Next, the developing device shown in FIG. 1 in which the gap between the developing sleeve and the cut blade is set to 650 μm using the above-mentioned developer is subjected to reversal development of a digital color reversal development type Canon color laser copying machine PIXEL. The distance between the photosensitive drum 1 (organic photosensitive material) and the surface of the sleeve 22 was set to 500 μm. The peripheral speed ratio σ between the photosensitive drum and the developing sleeve was set to 1.7. The developing sleeve used had an outer diameter of 32 mm, and the photosensitive drum used had an outer diameter of 80 mm. The photosensitive drum used was an OPC drum, and had a charged latent image potential of -700 V and an exposure latent image potential of -150 V. Frequency 2000H as bias power supply 4
z, -550 to AC voltage with a peak-to-peak value of 2000V
Development was performed using a DC voltage superimposed thereon.

At this time, Q = 25.0, F = 2.80
(V / μm).

With this combination, very good images were obtained at the initial image density without fogging or adhesion of magnetic particles.

Further, under normal temperature and normal humidity (23 ° C./60% RH)
, The image density was 1.45 to 1.6.
0 and a very good image were obtained. When a color OHP was prepared and the projected image was viewed, a clear image without shadow due to the attachment of the magnetic particles was obtained.

Furthermore, under low temperature and low humidity (15 ° C./10% R
H), when the continuous durability was performed, the image density was 1.40 to
A good image of 1.50 was obtained. Under high temperature and high humidity (32.
(5 ° C./85% RH), a good image having an image density of 1.50 to 1.60 was obtained, and no toner scattering was observed.

Table 3 shows the development characteristics.

The multi-segment classifier used in this embodiment and the classification process by the classifier will be described with reference to FIGS. 5 and 6, the multi-divider 51 has a side wall having a shape indicated by 72 and 74, a lower wall has a shape indicated by 75, and a side wall 73 and a lower wall 75.
Are provided with knife-edge-type classification edges 67, 68, respectively.
Has been fractionated. A raw material supply nozzle 66 that opens to the classification chamber is provided below the side wall 72, and a Coanda block 76 that is bent downward in the direction of extension of the tangent at the bottom of the nozzle to form a long elliptical arc is provided. The classifying chamber upper wall 77 includes a knife edge type inlet edge 69 in the classifying chamber lower direction,
Further, in the upper part of the classifying chamber, the intake pipes 64 and 65 opening to the classifying chamber.
Is provided. First and second gas introduction adjusting means 70 and 71 such as dampers and a static pressure gauge 7 are provided in the intake pipes 64 and 65.
8,79 are provided. Discharge pipes 61, 62, and 63 having discharge ports that open into the room are provided on the lower surface of the classifying chamber so as to correspond to the respective dividing areas. Classification powder supply nozzle 6
6 is introduced into the classifying region under reduced pressure, and moves by drawing a curved line 80 by the action of the Coanda effect of the Coanda block 76 due to the Coanda effect and the action of the high-speed air flowing in at that time. It was classified into a cyan fine powder 62 and an ultra fine powder 63 having a diameter and a particle size distribution.

Example 2 The volume average particle size was 8.0 μm and the number distribution was 5%.
36% by number of particles having a particle size of μm or less, and 6.35 to
38% by number of particles having a particle diameter of 10.1 μm, and 65% of particles having a particle diameter of 6.35 to 10.1 μm in a volume distribution.
% By volume, and particles having a particle size of 12.7 to 16 μm
A two-component developer was prepared in the same manner as in Example 1 except that 6% by volume, and particles having a particle size exceeding 16.0 μm were 0%. The test was performed. Table 3 shows the results.

Example 3 100 parts by weight of polyester resin obtained by condensation of propoxylated bisphenol and fumaric acid (weight average molecular weight (Mw) 17000, number average molecular weight (Mn) 3500) 100 parts by weight Rhodamine pigment 3 parts by weight・ Di-tert-butylsalicylic acid chromium complex 4 parts by weight

Using the above materials, the volume average particle diameter was 8.5 μm in the same manner as in Example 1, and 18% by number of particles having a particle diameter of 5 μm or less in the number distribution were 6.35.
55% by number of particles having a particle size of １10.1 μm, and 6 particles having a particle size of 6.35 to 10.1 μm in the volume distribution.
9% by volume, 2.6% by volume of particles having a particle size of 12.7 to 16.0 μm, and 0.1% by volume of particles having a particle size exceeding 16.0 μm. Colored resin particles were obtained.

The amount of charge having a specific surface area of 95 m ² / g by the BET method is substantially 0 in 100 parts by weight of the colored resin particles.
0.4 parts by weight of alumina fine powder and 0.4 parts by weight of silica fine powder having a specific surface area of 150 m ² / g by the BET method and having a hydrophobicity of 90 μc / g treated with dimethyldichlorosilane were added. Then, a magenta toner was obtained.

A two-component developer was prepared in the same manner as in Example 1, and an image output test was performed in the same manner as in Example 1. Table 3 shows the results.

Example 4 100 parts by weight of polyester resin (weight average molecular weight (Mw) 17000, number average molecular weight (Mn) 3500) obtained by condensing propoxylated bisphenol and fumaric acid I. Pigment Yellow 17 3.5 parts by weight Chromium complex salt of di-tert-butylsalicylic acid 4 parts by weight

Using the above materials, the volume average particle diameter was 7.7 μm in the same manner as in Example 1, and 31% by number of particles having a particle diameter of 5 μm or less in the number distribution were 6.35.
42% by number of particles having a particle size of １10.1 μm, and 6 particles having a particle size of 6.35 to 10.1 μm in the volume distribution.
5% by volume, 0.5% by volume of particles having a particle diameter of 12.7 to 16.0 μm is 0.5% by volume, and particles exceeding 16.0 μm are 0% by weight. Obtained.

In the same manner as in Example 1, a yellow toner is prepared by mixing hydrophobic silica and alumina with yellow colored resin particles, and further mixed with a resin-coated ferrite carrier to prepare a two-component developer. Table 3 shows the results of an image-drawing test performed in the same manner as in Example 1.

<Examples 5 to 8> A cyan toner was prepared by using the colored resin particles and the fluidity improvers shown in Tables 1 and 2, and an image formation test was performed in the same manner as in Example 1. Table 3 shows the results. As can be seen from Table 3, the toner of Example 1 was particularly excellent in durability and fog as compared with the toners of Examples 5 to 8.

<Comparative Example 1> As in Example 1, the volume average particle diameter was 11.1 µm, and the number distribution of particles having a particle diameter of 5 µm or less was 8% by number. 5 particles with a particle size of 1 μm
2% by number, and 6.35 to 10.1 in the volume distribution.
36% by volume of particles having a particle size of μm, 12.7 to 1
20.2% by volume of particles having a particle size of 6.0 μm,
Particles having a particle size exceeding 6.0 μm gave cyan colored resin particles of 3.0% by volume.

A cyan toner was prepared in the same manner as in Example 1, a two-component developer was prepared, and an image output test was performed in the same manner as in Example 1. Highlight part with lower image density compared to Example 1 (image density about 0.2 to 0.6)
Was inferior in gradation. Table 3 shows the test results.

[0212]

[Table 1]

[0213]

[Table 2]

[0214]

[Table 3] (Note 1) The evaluation of fog was performed by REFLEC manufactured by Tokyo Denshoku Co., Ltd.
Using TOMETER MODEL TC-6DS,
The yellow toner image was measured using a blue filter, the cyan toner image was measured using an amber filter, and the magenta toner image was measured using a green filter.
It calculated from the following formula using n filter. The smaller the value, the less fog. Fog (reflectance) (%) = reflectance of standard paper (%)-reflectance of non-image portion of sample (%)

(Note 2) The toner scattering state was determined by visually observing the toner scattering state around the developing device after the 5,000-sheet durability test. ◎… very good, ○… good, △… normal

(Note 3) The gradation of the highlight portion is determined by visually checking the quality of a toner image when an original image having a dot area of about 10% is copied. …: Good, △: Slightly good, ×: Roughness is observed.

Example 9 A two-component developer containing the cyan toner of Example 1, a two-component developer containing the magenta toner of Example 3, and a two-component developer containing the yellow toner of Example 4. When a full-color image was copied using a developer, a full-color toner image which was faithful to the color tone of the original image and was excellent in gradation was obtained.

[0218]

The image forming method of the present invention contains magnetic particles having a specific particle size distribution, colored resin powder having a specific particle size distribution, and a fluidity improver having a specific triboelectrification property. As a result, the triboelectric charge characteristics are stable, carrier adhesion is suppressed, toner scattering and fogging are unlikely to occur, and a large number of sheets are durable from the beginning under normal temperature, normal humidity, low temperature, low humidity, and high temperature, high humidity environments. It is possible to form a good image with a small difference in image density until later.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a main part of a developing unit to which an electrostatic image developer of the present invention can be applied.

FIG. 2 is a schematic diagram of an alternating electric field pattern according to the present invention in the case of normal development.

FIG. 3 is a schematic view of an alternating electric field pattern according to the present invention in the case of reversal development.

FIG. 4 shows an apparatus for measuring a charge amount used in the present invention.

FIG. 5 is an explanatory diagram relating to a classification step using a multi-division classification means.

FIG. 6 is a schematic cross-sectional perspective view of a multi-segment classification means.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Latent image carrier 22 Developing sleeve 23 Fixed magnetic field generating means (permanent magnet) 23a, 23b, 23c, 23d Magnetic pole 24 Non-magnetic blade 26 Magnetic particle limiting member 27 Magnetic particle 30 Scatter prevention electrode plate 36 Container 37 Non-magnetic toner 40 Seal Member 50 Toner concentration detection sensor 51 Screw 52 Screw 53 Stripper 54 Conveyor screw 102 Non-magnetic toner (colored resin powder) 261 Developer guide surface

Continuation of front page (56) References JP-A-63-41865 (JP, A) JP-A-63-26669 (JP, A) JP-A-62-289858 (JP, A) JP-A-62-182775 (JP, A) , A) JP-A-60-159767 (JP, A) JP-A-60-154261 (JP, A) JP-A-60-129764 (JP, A) JP-A-62-75686 (JP, A) 62-75687 (JP, A) JP-A-62-112170 (JP, A) JP-A-62-112171 (JP, A) JP-A-62-192757 (JP, A) JP-A-62-291666 (JP, A A) JP-A-62-174772 (JP, A) JP-A-58-1157 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 13/06-13/095 G03G 15 / 06-15/095 G03G 9/00-9/113

Claims (6)

(57) [Claims] 1. A two-component developer having at least a colored resin powder, a fluidity improver, and magnetic particles is supplied to a surface of a developer carrying member provided opposite to a latent image carrier having an electrostatic latent image. The two-component developer is carried on the surface of the developer carrying member, and the latent electrostatic image of the latent image carrier is developed with the two-component developer in a developing unit to form a visible image. In the image forming method, the colored resin powder has a volume average particle size of 4 to 10 μm,
In the volume distribution, it has a particle size distribution in which the content of particles having a particle size of 16.0 μm or more is 1.0% by volume or less, and has the same polarity as the potential V _L (V) of the electrostatic latent image. The magnetic particles have a triboelectric charging polarity, and the magnetic particles have a weight average particle diameter of 35 to 65 μm, and the content of particles having a particle diameter of 26 μm or more and less than 35 μm in a weight distribution is 1 to 20% by weight. Having a particle size distribution in which the content of particles having a particle size of 35 μm or more and less than 43 μm is 5 to 20% by weight, and the content of particles having a particle size of 74 μm or more is 2% by weight or less; forming an alternating electric field having an AC component and a DC component, the potential of the electrostatic latent image V _L (V), the DC component V _DC alternating electric field having the same polarity as _{V L (V) (V)} , V DC With respect to (V), the potential V at the maximum electric field application point located opposite to the potential _VL (V) of the electrostatic latent image. _PP Max (V) and the maximum charge intensity F (V / μm) of the image area formed by the closest gap G (μm) between the developer carrying member surface and the electrostatic latent image carrier surface
The following relation 1.5 ≦ F ≦ 3.5 Is satisfied, the frequency ν (KHz) of the alternating electric field is 0.8 ≦ ν ≦ 3.0, the relative volume ratio of magnetic particles Q% in the developing section is 15.0 ≦ Q ≦ 45.0, and In the developing section, the relative speed ratio σ between the developer carrying member and the electrostatic image carrier is 1.2 ≦ σ ≦ 2.5 under the condition that the electrostatic latent image is reversibly developed using a two-component developer. An image forming method. Wherein said two-component developer, (i) the absolute value of the triboelectric charge quantity has a triboelectric charging characteristic is 50μc / g or more, specific surface area by the BET method: S _A is 80~300m ² / g
A based on the colored resin powder
Weight%, and (ii) the absolute value of the triboelectric charge amount is 20 μc
/ G have triboelectrification characteristics or less, the hydrophilic inorganic compound of specific surface area S _B by the BET method 30 to 200 m ² / g B
Is contained as the fluidity improver based on the colored resin powder, and the specific surface area S of the hydrophobic inorganic oxide A is
_A and the content a specific surface area of the hydrophilic inorganic compound B S _B and content b is following condition specific surface area S _A ≧ specific surface area S _B content a ≧ content b 0.3 ≦ content a + content b ≦ 2. The image forming method according to claim 1, wherein 1.5 is satisfied. 3. a hydrophobic inorganic oxide A is hydrophobic silica fine powder, claim 2, wherein the hydrophilic inorganic compound B is a fine alumina powder or titanium oxide fine powder
2. The image forming method according to 1., 4. The colored resin powder according to the number distribution,
The content of particles having a particle size of 5 μm or less is 15 to 40% by number .
Ah is, in volume distribution, the content of particles having a particle size of 12.7~16.0μm is 0.1 to 5.0% by volume, 16
It has a particle size distribution in which the content of particles having a particle size exceeding μm is 1.0% by volume or less, and in the particle size distribution of the colored resin powder, 6.35 to 10.
The content of particles having a particle size of 1 μm is expressed by the following formula: [Wherein, V is 6.35 to 10.1 μm in the volume distribution.
Indicates the volume% of particles having a particle size of N, and N indicates the number% of particles having a particle size of 6.35 to 10.1 μm in the number distribution,
d _V indicates the volume average particle size of the colored resin powder]. Wherein said two-component developer, (i) the absolute value of the triboelectric charge quantity has a triboelectric charging characteristic is 50μc / g or more, specific surface area by the BET method: S _A is 80~300m ² / g
A based on the colored resin powder
Weight%, and (ii) the absolute value of the triboelectric charge amount is 20 μc
/ G have triboelectrification characteristics or less, the hydrophilic inorganic compound of specific surface area S _B by the BET method 30 to 200 m ² / g B
Is contained as the fluidity improver based on the colored resin powder, and the specific surface area S of the hydrophobic inorganic oxide A is
_A and the content a specific surface area of the hydrophilic inorganic compound B S _B and content b is following condition specific surface area S _A ≧ specific surface area S _B content a ≧ content b 0.3 ≦ content a + content b ≦ 1.5, and the colored resin powder has a content of particles having a particle size of 5 μm or less in a number distribution of 15 to 40% by number, and a volume distribution of 12.7 to 16.0 μm. The colored resin has a particle size distribution in which the content of particles having a particle size of 0.1 to 5.0% by volume and the content of particles having a particle size exceeding 16 μm is 1.0% by volume or less. In the particle size distribution of the powder, 6.35 to 10.
The content of particles having a particle size of 1 μm is expressed by the following formula: [Wherein, V is 6.35 to 10.1 μm in the volume distribution.
Indicates the volume% of particles having a particle size of N, and N indicates the number% of particles having a particle size of 6.35 to 10.1 μm in the number distribution,
d _V indicates the volume average particle size of the colored resin powder]. 6. The method according to claim 1, wherein the fluidity improver has an absolute value of a charge amount of 100 μc / g or less when frictionally charged with the magnetic particles. Image forming method.