JP3284487B2 - Development method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing method for a copier or a printer, and more particularly to an electrophotographic developing method.

[0002]

2. Description of the Related Art Conventionally, a dry developer comprising toner particles as a developer and a magnetic carrier is carried on the surface of a developer carrier, and is conveyed and supplied to the vicinity of the surface of an image carrier carrying an electrostatic latent image. A method of forming a magnetic brush of developer on a developer carrying member and developing an electrostatic latent image while applying an alternating (alternating) electric field between the image carrying member and the developer carrying member to visualize the latent image. ,
well known. This developing method is often referred to as a magnetic brush developing method.

Since the developer carrier is generally used as a developing sleeve in a developing device, it is generally referred to as a developing sleeve in the following description. In addition, since the image bearing member is generally often used as a photosensitive drum, it will be generally referred to as a photosensitive drum in the following description.

[0004] As the above-mentioned developing method, conventionally, for example, a magnetic brush is formed on the surface of a developing sleeve by disposing a magnet inside with a developer (two-component developer) having a two-component system composition (carrier particles and toner particles). The magnetic brush is rubbed or brought close to the photosensitive drum opposed to the photosensitive drum while maintaining a small developing gap, and a continuous alternating electric field is applied between the developing sleeve and the photosensitive drum, so that the developing sleeve for toner particles is formed. A so-called magnetic brush developing method in which development is performed by repeatedly performing transfer from the side to the photosensitive drum side and reverse transfer in the opposite direction is known (for example, Japanese Patent Application Laid-Open No. 55-3).
2060, JP-A-59-165082). Further, a non-contact type alternating electric field development method using a two-component developer for simple color development or multiple development is well known (for example, JP-A-56-14268, JP-A-58-15858). -68051, JP-A-56-14
4452, JP-A-59-181362 and JP-A-60-1760690.

On the other hand, among image forming apparatuses using the above-mentioned developing method, there is a laser beam printer adopting an electrophotographic method as a high-speed and low-noise printer. A typical application of this printer is binary recording of images such as characters and figures. A so-called binary scanner which emits a laser beam corresponding to an image signal to be recorded and scans an electrophotographic photosensitive member while extinguishing the laser beam. A record is made. Since the recording of characters and figures does not require halftones, the structure of the printer is simplified. As a device capable of expressing halftones with the laser beam printer of the binary recording system, a device employing a dither method, a density pattern method, or the like is well known.

However, as is well known, it is difficult to obtain a high resolution with a printer employing the dither method and the density pattern method. Therefore, in recent years, a method of forming a halftone image while obtaining high resolution without lowering the recording density has been proposed. In this method, a halftone image is formed by modulating the width of a pulse signal for driving a laser by an image signal. That is, the luminous flux emission time per pixel of the laser is controlled according to the image density, and therefore, the photoconductor irradiation time per pixel of the laser beam for scanning the photoconductor is controlled according to the image density. Is done.

Specifically, the pulse width of the pulse signal is shortened for a low-density image portion to shorten the photosensitive member irradiation time length, and the pulse width is increased for a high-density image portion. Thus, the irradiation time length of the photoconductor is increased. According to such a pulse width modulation (PWM) method, high resolution and
An image with high gradation can be formed. Therefore, this method is indispensable especially for a color image forming apparatus requiring high resolution and high gradation.

[0008]

However, when an image is output by a copying machine as in the prior art, roughening occurs in a halftone area having a reflection density of 0.3 or less. This roughness was not so much generated in a character document or the like, but was often generated in a low density area such as a photographic image.

[0009] Then, when the cause of the generation of the roughness was examined, the following was found. When a latent image of a highlight portion is formed by a normal dot latent image, when viewed microscopically, the latent image on the photoconductor is not a broad latent image like an analog latent image but a local latent image. When you try to further reproduce than the low density, maximum contrast V ₀ becomes gradually smaller as the latent image accent Figure 10 from the effects of the film thickness of the photoreceptor. For example, V ₀ of when trying to reproduce the image of the degree of reflection density 0.2, 150-25
It will be about 0V. Also, in the case of reverse development, the surface potential of the non-image portion to take the fog, because they are 100~200V set higher than the DC component of the developing bias, V ₀ is a developing bias in the case of 150～250V D
The potential difference V _{CONT from the} C component is about 0 to 100V. The reason that V _CONT is 0 to 100 V is a very unstable contrast whether the toner is applied to the photoconductor side or the sleeve side. Therefore, when the latent image is developed by the two-component developer, the contact state of the magnetic brush greatly contributes to the development effect, and the roughness of the magnetic brush due to missing dots corresponding to the unevenness of the ears is liable to occur. .

Further, in order to eliminate the roughness, an alternating electric field is superimposed on the developing bias, and the bias is changed to 6 kHz.
As described above, a method has been proposed in which the frequency is increased so that the toner does not reciprocate in one pulse. According to this method, the toner makes an oscillating motion so as not to reciprocate between S and D. When the potential difference V _CONT between the surface potential of the photosensitive drum and the DC component of the developing bias is V _CONT <0, the DC component acts to attract the toner to the sleeve side, the toner is biased to the sleeve side, and V _CONT is V _CONT In the case of> 0, the DC component acts to attract toner to the drum side in accordance with the latent image potential, and an amount of toner corresponding to the latent image potential is biased to the photosensitive drum side. This tendency becomes more remarkable by applying an alternating electric field intermittently. Further, the toner that reaches the photosensitive drum that develops under such conditions repeats vibration on the photosensitive drum and concentrates on the latent image portion. For this reason, it has become possible to obtain a good image with uniform dot shape and no unevenness.

However, this developing method has a drawback that only toner having a certain amount of tribo is used for development. Toner with high tribo is hard to pop out of the carrier and the developing sleeve, and toner with low tribo is protruded even if it pops out. Before being reached, and as a result, the T
There is a disadvantage that the density greatly changes depending on the / (T + C) ratio [T: toner, C: carrier] .

Since the amount of toner supplied to the developing unit by the rotation of the developing sleeve is two to three times the amount of the toner used for normal development, most of the toner in the developing unit is removed from the photosensitive drum and the developing sleeve. If the reciprocating motion by the developing bias is performed during the period, the developing condition is determined by the state of the latent image, and T / (T +
C) It is considered that the concentration variation due to the ratio is reduced.

However, in the conventional developing method, the density greatly changes depending on the T / (T + C) ratio as described above. This is because the conventional developing method involves development only in an appropriate range of toner in the tribo, and therefore T / (T
+ C) It is considered that the amount of toner involved in the development changes with the change in the ratio, which changes the development density. For this reason, with the conventional improved development method,
Although the roughness at a concentration of 0.2 to 0.3 is reduced, T /
There is a problem that the density fluctuation due to the (T + C) ratio is particularly large on the low density side.

Accordingly, it is an object of the present invention to provide an image processing apparatus which is uniform in a highlight portion, has less density fluctuation due to the T / (T + C) ratio, and
Accordingly, an object of the present invention is to provide an image method capable of stably obtaining a high-quality image.

[0015]

In order to achieve the above object, the present invention provides a developer container for containing a developer having toner particles and magnetic particles; and a latent image support on which an electrostatic latent image is formed. And a developer carrying member configured to form a developing unit between the developer container and carrying the developer in the developer container to the developing unit while carrying the developer therein;
A magnetic field generating means provided inside the developer carrier, wherein the developing section supplies the latent image carrier to the latent image carrier. _Vpp [V]: peak of an alternating voltage applied to the developer carrier Peak-to-peak voltage _Vf [Hz]: frequency of alternating voltage applied to the developer carrier _Vcont [V]: image contrast potential (latent image when maximum image density is output from DC voltage of developing bias) potential difference between) Q [C / kg]: the average toner triboelectricity d [m]: developer carrier - when the distance of the latent image bearing _{member, | V pp -2V cont | /} 16V f 2 <d 2 / | Q | is provided with means for applying an alternating voltage to the developer carrier so that an alternating electric field satisfying the condition of | / Q | is formed intermittently.
An object of the present invention is to provide a developing method characterized by using toner particles having a fluidity of 15 % or less.

[Measurement method] 200 mesh, 100
Overlay the screen in the order of mesh and 60 mesh, toner 5
g on a 60 mesh sieve. 15 seconds for sieve
After the vibration, the toner weight on each screen is measured. The apparatus used was a powder tester (PT-D) manufactured by Hosokawa Micron Corporation.

[0017]

(Equation 2) (The value calculated by the above equation is a value indicating the fluidity of the present invention, and the higher the fluidity, the smaller the value.)

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, constituent materials of a developer suitable for the present invention will be described in detail. For details of the external additive and developing method of the toner particles characterized in the present invention,
This will be described in Examples.

As the binder used in the toner of the present invention, various material resins conventionally known as toner binder resins for electrophotography are used.

For example, styrene-based copolymers such as polystyrene, styrene-butadiene copolymer, styrene-acrylic copolymer, and ethylene-based copolymers such as polyethylene, ethylene-vinyl acetate copolymer, and ethylene-vinyl alcohol copolymer Copolymer, phenolic resin, epoxy resin, acrylic phthalate resin, polyamide resin, polyester resin, maleic acid resin and the like. In addition, the production method of any resin is not particularly limited.

The effect of the present invention is remarkable when a polyester resin having a high negative chargeability is used among these resins. That is, the polyester-based resin has excellent fixability and is suitable for a color toner, but has a strong negative charging ability and tends to be excessively charged. However, when the polyester resin is used in the composition of the present invention, the harmful effects are improved and excellent. A toner is obtained.

In particular, the following equation

[0023]

Embedded image

(Wherein R is an ethylene or propylene group, x and y are each an integer of 1 or more, and x +
The average value of y is 2-10. A) a carboxylic acid component comprising a divalent or higher carboxylic acid or an acid anhydride thereof or a lower alkyl ester thereof (for example, fumaric acid, maleic acid, maleic anhydride, phthalic acid) Acid, terephthalic acid, trimellitic acid, pyromellitic acid, etc.) are more preferred because they have sharp melting properties.

The coloring agents used in the present invention include dyes and pigments known as non-magnetic toners, such as phthalocyanine blue, induslen blue, peacock blue, permanent red, lake red, rhodamine lake, Hansa yellow, permanent yellow, Benzidine yellow or the like can be used. As its content,
In order to reflect the transparency of the OHP film sensitively, the amount is 12 parts by weight or less, preferably 0.5 to 9 parts by weight, based on 100 parts by weight of the binder resin.

The toner of the present invention does not limit the negatively chargeable property and the positively chargeable property. However, when producing a negatively chargeable toner, a charge control agent is added particularly for the purpose of stabilizing the negative charge property. Is preferred. Examples of the negative charge control agent include an organometallic complex such as a metal complex of an alkyl-substituted salicylic acid (for example, a chromium complex or a zinc complex of di-tert-butylsalicylic acid).

In the case of preparing a positively chargeable toner, nigrosine, a triphenylmethane compound, a rhodamine dye, polyvinyl pyridine, or the like may be used as a charge control agent having a positive charge. When a color toner is prepared, it is desirable to use a colorless or light-colored positive charge control agent that does not affect the color tone of the toner.

If necessary, additives may be added to the toner of the present invention as long as the characteristics of the toner are not impaired. Such additives include, for example, charge aids such as organic resin particles and metal oxides, or lubricants such as Teflon, zinc stearate, and polyvinylidene fluoride, or fixing aids (eg, low molecular weight polyethylene, low molecular weight polypropylene). Etc.).

In order to prepare the colorant-containing resin particles according to the present invention, a thermoplastic resin may be sufficiently mixed with a pigment or dye as a colorant, a charge control agent, and other additives by a mixer such as a ball mill, if necessary. After mixing, heat roll, kneader, melt using a hot kneader such as extruder,
The pigments or dyes are dispersed or dissolved in the resin mixed with each other by kneading and kneading, and after cooling and solidification, pulverization and strict classification are performed to obtain the colorant-containing resin particles according to the present invention. I can do it.

In the present invention, a two-component developer in which a carrier is used in combination with a toner is also applicable.

The carrier used in the present invention includes, for example, iron, nickel, copper, zinc, surface oxidized or unoxidized.
Metals such as cobalt, manganese, chromium, and rare earths, and alloys or oxides thereof, and ferrites can be used. In addition, there is no particular limitation on the manufacturing method.

As the method of coating the surface of the carrier with a resin or the like, a method of dissolving or suspending a coating material such as a resin in a solvent, applying the coating material, and attaching the coating material to the carrier,
Any conventionally known method, such as a method of simply mixing with a powder, can be applied.

The substance fixed to the carrier surface varies depending on the toner material. Examples thereof include polytetrafluoroethylene, monochlorotrifluoroethylene polymer, polyvinylidene fluoride, silicone resin, polyester resin, metal complex of ditersharry butylsalicylic acid, and styrene-based. It is appropriate to use resin, acrylic resin, polyamide, polyvinyl butyral, nigrosine, aminoacrylate resin, basic dye and its lake, silica fine powder, alumina fine powder, etc. alone or in combination, but it is not necessarily limited to this. Not done.

The treatment amount of the above compound may be appropriately determined so that the carrier satisfies the above conditions, but is generally 0.1 to 30% by weight (preferably 0.1 to 30% by weight) based on the total amount of the carrier.
5 to 20% by weight).

The average particle size of these carriers is 10 to 100.
μm, preferably 20-70 μm.

In a particularly preferred embodiment, Cu—Zn—
Fe ternary ferrite whose surface is a combination of a silicone resin or a resin such as a fluorine resin and a styrene resin, for example, polyvinylidene fluoride and styrene-
Methyl methacrylate resin; polytetrafluoroethylene and styrene-methyl methacrylate resin, fluorine-based copolymer and styrene-based copolymer; silicone-based resin 90:10 to 20:80, preferably 70:30 to
A mixture having a ratio of 30:70, 0.01 to 5
% By weight, preferably 0.1-1% by weight,
A coated ferrite carrier having the above average particle diameter, in which carrier particles of 250 mesh pass and 400 mesh on are 70% by weight or more, may be mentioned. As the fluorine-based copolymer, a vinylidene fluoride-tetrafluoroethylene copolymer (10:90 to 90:10) is exemplified, and as the styrene-based copolymer, styrene-2-ethylhexyl acrylate (20:80 to 80:20), and styrene-2-ethylhexyl acrylate-methyl methacrylate (20 to 60: 5 to 30:10 to 50).

When the coated ferrite carrier has a sharp particle size distribution, a favorable triboelectric charging property is obtained with respect to the toner of the present invention, and there is an effect of further improving electrophotographic properties.

When a two-component developer is prepared by mixing with the toner of the present invention, the mixing ratio is 2 to 15% by weight, preferably 4 to 13% by weight as the toner concentration in the developer. Then usually good results are obtained. If the toner concentration is less than 2% by weight, the image density tends to decrease,
If it exceeds 15% by weight, fog and scattering in the machine are increased, and the useful life of the developer tends to be shortened.

[0039]

FIG. 2 is a schematic sectional view of a color image forming apparatus according to an embodiment of the present invention.

This embodiment has a digital color image reader section at the top and a digital color image print section at the bottom. The original 30 is placed on the platen glass 31 in the reader unit,
The original 3 is scanned by exposure using the exposure lamp 32.
The reflected light image from 0 is condensed on the full color sensor 34 by the lens 33 to obtain a color separation signal. The color-separated image signal is processed by a video processing unit (not shown) through an amplifier circuit (not shown) and sent to a printing unit.

In the printer section, a photosensitive drum 1 serving as an image carrier is rotatably supported in the direction of an arrow. A pre-exposure lamp 11, a corona charger 2, and a laser exposure optical system serving as a light beam emitting means are provided around the photosensitive drum 1. 3, potential sensor 12,
Four developing units 4y, 4c, 4m, and 4BK of different colors, an on-drum light amount detecting unit 13, a transfer device 5, and a cleaning unit 6 are arranged.

In the laser exposure optical system 3, an image signal from the reader unit is converted into an optical signal by a laser output unit (not shown), and the converted laser light is reflected by the polygon mirror 3a, and the lens 3b and the mirror 3c, and is projected on the surface of the photosensitive drum 1.

The laser output section is on-off modulated by a PWM (pulse width modulation) electric signal in accordance with image density information.

At the time of image formation in the printer section, the photosensitive drum 1
Is rotated in the direction of the arrow to uniformly charge the photosensitive drum 1 after charging by the pre-exposure lamp 11 by the charger 2, and irradiate the light image E for each separation color to form a latent image.

Next, a predetermined developing unit is operated to reversely develop the latent image on the photosensitive drum 1 to form a toner image on the photosensitive drum 1 using a resin as a base. The developing unit selectively approaches the photosensitive drum 1 in accordance with each separated color by the operation of the eccentric cams 24y, 24c, 24m, and 24BK.

Further, the toner image on the photosensitive drum 1 is
The image is transferred from a recording material cassette 7 to a recording material supplied to a position facing the photosensitive drum 1 via a transfer system and a transfer device 5. In the present embodiment, the transfer device 5 includes a transfer drum 5a, a transfer charger 5b, and an adsorption charger 5c for electrostatically adsorbing a recording material.
A recording material carrying sheet 5f made of a dielectric material is provided on a peripheral opening area of a transfer drum 5a which is rotatably driven and has an attraction roller 5g, an inner charger 5d, and an outer charger 5e opposed thereto. Are integrally extended in a cylindrical shape. The recording material supporting sheet 5f uses a dielectric sheet such as a polycarbonate film.

As the transfer device in the form of a drum, that is, the transfer drum 5a is rotated, the toner image on the photosensitive drum is transferred onto the recording material carried on the recording material carrying sheet 5f by the transfer charger 5b.

As described above, a desired number of color images are transferred onto the recording material sucked and conveyed to the recording material carrying sheet 5f to form a full-color image.

In the case of forming a full-color image, when the transfer of the toner images of four colors is completed in this way, the recording material is separated from the transfer drum 5a by the action of the separation claw 8a, the separation push-up roller 8b and the separation charger 5h. The sheet is discharged to the tray 10 via the roller fixing device 9.

On the other hand, the post-transfer photosensitive drum 1 is subjected to an image forming process again after the residual toner on the surface is cleaned by the cleaning device 6.

When forming images on both sides of a recording material,
Immediately after the fixing device 9 is ejected, the conveyance path switching guide 19 is driven, and once guided to the reversing path 21a via the conveyance vertical path 20, the rear end of the reversing roller 21b is moved forward by the reverse rotation of the reversing roller 21b. And is retracted in the direction opposite to the direction in which the sheet is fed, and stored in the intermediate tray 22. Thereafter, an image is formed on the other surface again by the above-described image forming step.

Further, in order to prevent scattering of powder on the recording material carrying sheet 5f of the transfer drum 5a, adhesion of oil on the recording material, and the like, the fur brush 14 and the recording material carrying sheet 5f are interposed. 14, a backup brush 15, an oil removing roller 16, and a recording material carrying sheet 5.
Cleaning is performed by the action of the backup brush 17 facing the roller 16 via f. Such cleaning is performed before or after image formation, and at any time when a jam (paper jam) occurs.

In this embodiment, the gap between the recording material carrying sheet 5a and the photosensitive drum 1 is reduced by operating the eccentric cam 25 at a desired timing and operating the cam follower 5i integrated with the transfer drum 5f. The configuration can be set arbitrarily. For example, during standby or when the power is off, the interval between the transfer drum and the photosensitive drum is increased.

FIG. 1 is an enlarged sectional view of the developing device.

The developing device has a developer container 116. The inside of the developer container 116 is divided into a developing chamber (first chamber) R1 and a stirring chamber (second chamber) R2 by a partition wall 117, and a toner storage chamber R3. Inside is a supply toner (non-magnetic toner) 11
8 are accommodated. The partition 117 has a supply port 12.
0 is provided, and a replenishing toner 118 in an amount corresponding to the toner consumed through the replenishing port 120 is dropped and replenished into the stirring chamber R2.

On the other hand, a developer 119 is accommodated in the developing chamber R1 and the stirring chamber R2. The developer 119 is a two-component developer having a non-magnetic toner and magnetic particles (carrier) (the mixing ratio of the non-magnetic toner is about 4 to 1 by weight.
0%. ). Here, the non-magnetic toner is 5 ×
It has a volume average particle size of 10 ^-6 to 8 × 10 ^-6 m. Also,
The magnetic particles consist of resin-coated ferrite particles (maximum magnetization of 60 emu / g), the weight average particle size is 5 × 10 ⁻⁵ m, and the resistance value is 10 ⁸ Ω · cm.
The above values are shown. The magnetic permeability of the magnetic particles is about 5.0.

An opening is provided in a portion of the developer container 116 close to the photosensitive drum 1, and a developing sleeve 111 projects outside from the opening. The developing sleeve 111 is rotatably incorporated in the developing container 116. The outer diameter of the developing sleeve 111 is 32 mm, and its peripheral speed is 2.8 × 10 ⁻¹ m / sec. Developing sleeve 11
1 is arranged such that the distance between the photosensitive drum 1 and the photosensitive drum 1 is 5 × 10 ⁻⁴ m. The developing sleeve 111 is made of non-magnetic material, and has a magnet 112 fixed therein as a magnetic field generating means.

The magnet 112 has a developing magnetic pole S ₁ , a magnetic pole N ₃ located downstream thereof, and magnetic poles N ₂ , S ₂ , N ₁ for transporting the developer 119. The magnet 112 is arranged in the developing sleeve 111 such that the developing magnetic pole S ₁ faces the photosensitive drum 1.

The developing magnetic pole S ₁ forms a magnetic field near the developing section between the developing sleeve 111 and the photosensitive drum 1, and the magnetic field forms a magnetic brush.

The blade 1 is located above the developing sleeve 111.
Reference numeral 15 is arranged at a predetermined distance from the developing sleeve 111. The distance between the developing sleeve 111 and the blade 115 is 8 × 10 ⁻⁴ m. The blade 115 is the developing container 1
16 fixed. The blade 115 is made of a nonmagnetic material such as aluminum or SUS316, and regulates the layer thickness of the developer 19 on the developing sleeve 111. Developing room R
A transport screw 113 is accommodated in the inside 1. The transport screw 113 is rotated in the direction indicated by the arrow in the figure,
The developing chamber R1 is driven by the rotation of the transport screw 113.
The developer 119 inside is transported in the longitudinal direction of the developing sleeve 111.

A transport screw 114 is accommodated in the storage room R2. The transport screw 114 transports the toner along the longitudinal direction of the developing sleeve 111 by its rotation, and the toner falls freely from the supply port 120 into the stirring chamber R2.

The developing sleeve 111 carries the developer at a position near the magnetic pole N ₂ , and the developer 119 is conveyed toward the developing unit as the developing sleeve 111 rotates. Developer 1
19 the developing sleeve 111 while succession by the magnetic force magnetic particles of the magnetic pole S ₁ of the developer 119 to reach the vicinity of the developer
And a magnetic brush of the developer 119 is formed.

The end of the magnetic brush is developed by rubbing the surface of the photosensitive drum 1. At this time, the fluidity of the toner in the developer is adjusted to a value of 20% or less as measured by the method described above, and a titanium oxide or alumina is used as an external additive to be externally added to the resin of the toner. As a result, it is possible to obtain an image with a small density fluctuation due to a change in environment or T / (T + C) ratio.

If the fluidity of the toner is increased, when the toner is mixed with the carrier, the toner not sufficiently charged is moved without restraint. for that reason,
The toner to which no charge is applied frequently repeats the contact with the carrier, so that a sufficient charge is immediately applied.
As a result, the toner having a high fluidity increases the number of times of contact with the carrier, and almost all the toners have a uniform tribo value. However, although it was possible to improve fluidity by using a conventional external additive such as silica, it was difficult to obtain stable developing conditions because the triboelectric fluctuation due to the environment was too large. Therefore, if titanium oxide or alumina was used as an external additive, it was possible to reduce the tribo-fluctuation caused by environmental fluctuations.However, conventional titanium oxide-based and alumina-based particles have a lower toner flow rate than silica-based particles. It is difficult to increase the fluidity, usually the liquidity is 2
It was difficult to reduce the content to 0% or less.

In the present invention, by using titanium oxide described below as an external additive, it has become possible to stably obtain an image having very little density fluctuation. The details are described below.

In the present invention, a TiO ₂ component and a Ti (OR) _m (OH) _n component [wherein R represents a hydrocarbon group, m and n each represent an integer of 0 to 4] m + n is 4. ], And a toner for developing an electrostatic image to which a treated fine powder treated with a silane-based organic compound is externally added.

In the present invention, the TiO ₂ component is 85 to 9
A fine powder is formed of a composition containing 9.5% by weight and 0.5 to 15% by weight of a Ti (OR) _m (OH) _n component, and the surface of the fine powder is a silane-based organic compound. An electrostatic image developer having a processed fine powder treated with a compound is preferred.

The present inventors have conducted intensive studies focusing on the fluidity of the toner for developing an electrostatic image, including the chargeability, transferability, and cleaning properties. They have been found to be extremely effective in imparting properties and stabilizing charging.

This cannot be achieved with inorganic fine powder such as titanium oxide as a generally known fluidity-imparting agent.

The reason is that the conventional method for producing titanium oxide requires a sintering, hydrolysis or thermal decomposition step at a high temperature, so that the particles tend to be coarsened, and the resulting titanium oxide particles are anatase or rutile. It becomes easy to take the crystal structure of the mold.

On the other hand, the TiO ₂ component and Ti (OR) _m
(OH) In the fine powder of the composition having the _n component (where m and n are integers from 0 to 4, satisfying m + n = 4 and R represents a hydrocarbon group), particles And the primary particles have less coalescence between the primary particles, and it is possible to impart good fluidity to the colorant-containing resin particles, that is, the toner, and to reproduce fine lines and highlights of the original document. And provide a high-quality toner image excellent in image quality.

In addition, since the fine powder used in the present invention contains a titanium alkoxide and a titanium hydroxy component, the activity T on the surface of the fine powder is higher than that of ordinary rutile, anatase or amorphous titanium oxide particles.
The i-OH group is much more and therefore exhibits good dispersibility when dispersed in the colorant-containing resin particles, and when attached to the surface of the colorant-containing resin particles, the binder resin and the fine powder High adhesion to the body, no fine powder detaches from the surface of the colorant-containing resin particles due to durability, and does not contaminate the surface of the carrier particles or the photoreceptor drum. It is possible to

Further, the treated fine powder used in the present invention is T
Since it has an iO ₂ component and a Ti (OR) _m (OH) _n component, when the toner and the carrier in which the treated fine powder is dispersed in the colorant-containing resin particles are frictionally charged, the Ti (OR) in the treated fine powder is _{The m} (OH) _n component serves as a kind of leak point to suppress the charge amount from becoming excessive. In particular, it greatly functions to suppress an excessive charge amount under low temperature and low humidity, and a stable charge amount can be obtained. In particular, when a polyester resin is used as the binder resin, the effect is large. Further, when the colorant-containing resin particles are reduced in size, the effect is remarkable.

Further, since the treated fine powder used in the present invention has small primary particles and very few secondary aggregates, it contains a coloring agent when used in a color toner for forming a full-color image. External addition to resin particles can be performed uniformly, excellent light transmittance in visible light, and clear OHP
An image is obtained. This has not been achieved with conventional titanium oxide particles.

Further, when the surface of the fine powder is to be treated with, for example, a silane-based organic compound, conventional rutile-type, anatase-type or amorphous titanium oxide fine particles have a small amount of active Ti-OH groups on the surface and can be sufficiently treated. What was not present was the fine powder used in the present invention.
The reaction between the (OR) _m (OH) _n component and the treating agent proceeds smoothly, and the surface can be treated uniformly without forming aggregates. It can be raised sufficiently to the level. This makes it possible to stably charge under high temperature and high humidity.

In the present invention, a TiO ₂ component and a TiO ₂ component produced by thermally decomposing a volatile titanium compound such as a titanium alkoxide at a relatively low temperature of 600 ° C. or lower, preferably 200 to 400 ° C., are preferably used. (OR) _m (O
H) A fine powder of a composition containing an _n component as a main component is preferred.

In particular, after a volatile titanium compound is vaporized or atomized at a relatively low temperature of 200 to 400 ° C., it is hydrolyzed (or may be thermally decomposed) in the presence of heated steam to decompose. It is preferable to cool the mixture in a short time as soon as possible to a temperature at which the fine particles do not coalesce again (preferably 100 ° C. or lower).

By the above means, a fine powder having a fine primary particle diameter can be obtained.

This will be described in further detail.

[0080] Namely, the present inventors suppressed coarsening of fine powder, made various studies in order to generate a coherent less fine powder, not only the TiO ₂ component, Ti (OR)
_In the case of a composition containing an _m (OH) _n component as an essential component, crystallization of titanium oxide is suppressed, and the particles become finer in particle diameter, the shape becomes more spherical, and the Ti −
The present inventors have found that OH groups are shifted in more directions, and have reached the present invention.

This cannot be achieved with rutile or anatase titanium oxide or amorphous titanium oxide.

In particular, the TiO ₂ component used in the present invention and Ti
The fine powder of the composition having the (OR) _m (OH) _n component as a main component has a TiO ₂ component of 85 to 99.5% by weight and a Ti (OR) _m (OH) _n component of 0.5 to 15% by weight. It is preferable to have

That is, when the TiO ₂ component is less than 85% by weight, a system in which a large amount of titanium alkoxide and titanium hydroxy component remains or a system containing a large amount of impurities is applied to this. It is difficult to produce a fine powder having a distribution, and individual particles tend to have a non-uniform composition. When the toner containing the fine powder as described above is charged with carrier particles, the charge amount distribution is broad. And it is difficult to achieve uniform development and a high transfer rate.

On the other hand, when the TiO ₂ component is more than 99.5% by weight, the fine powder approaches the pure titanium oxide particles as much as possible, easily taking a crystal structure, and the particles tend to become coarse. With this, it is not easy to obtain the desired good fluidity.

The Ti (OR) _m (OH) _n component has a content of 0.1.
When the content is less than 5% by weight, the dispersibility of the treated fine powder in the color-containing resin particles is reduced, and especially when the treated fine powder is attached to the surface of the colorant resin particles (when the treated fine powder is externally added). Desorption from the particle surface is likely to occur, and carrier contamination and drum contamination are likely to occur. In particular, when the surface of the carrier is contaminated, the charge amount of the toner is greatly reduced, and toner scattering and fogging at the time of durability are deteriorated, and it is difficult to maintain a constant image density. Furthermore, Ti (O
When R) _m (OH) _n component is less than 0.5% by weight,
Fine powder tends to coarsen, making it difficult to improve the fluidity of the toner to a target level.

When the Ti (OR) _m (OH) _n component is 15
If the amount of the fine powder is larger than the percentage by weight, the cooling property is reduced, and a mark of defective cleaning may be generated on an image. This applies fine powder (particularly Ti
It is presumed that the toner is contaminated by (OR) _m (OH) _n component (fine powder containing more components), and the releasability of the toner from the photoconductor is greatly reduced.

Therefore, in the present invention, the treated fine powder has a Ti (OR) _m (OH) _n component of 0.5 to 15% by weight, preferably 1.0 to 12% by weight, more preferably 1.5 to 15% by weight.
Those containing 10% by weight are good.

The composition ratio between the TiO ₂ component and the Ti (OR) _m (OH) _n component is determined according to the following procedure.

First, the fine powder is left in a vacuum dryer at 60 ° C. for 3 days and dried under reduced pressure to determine the water content.

Next, an elemental analyzer EA- manufactured by Carlo Elba, Inc.
In 1108, the C amount and the H amount are calculated, and from these values, the composition ratio of the TiO ₂ component and the Ti (OR) _m (OH) _n component is calculated.

The compound other than TiO ₂ is Ti (O
It is confirmed by FT-IR analysis that the compound is represented by R) _m (OH) _n (m + n = 4). After drying under reduced pressure, components other than the above two compounds are trace amounts. You can ignore it.

The raw materials for the fine powder used in the present invention include titanium alkoxides such as titanium tetramethoxide, titanium tetraethoxide, titanium tetrapropoxide, titanium tetrabutoxide, and diethoxy titanium oxide.
Tetrahalogenated titanium compounds such as titanium tetrachloride and titanium tetrabromide, and volatile titanium compounds such as trihalogenated monoalkoxytitanium, dihalogenated dialkoxytitanium and monohalogenated trialkoxytitanium can also be used.

When the volatile titanium compound is vaporized or atomized, it is preferable to dilute the volatile titanium compound with a diluting gas at a ratio of 0.1 to 10% by volume. The diluent gas serves as a carrier gas for introducing the vaporized volatile titanium compound into a decomposition furnace for decomposing.

Here, as the diluting gas, argon gas,
An inert gas such as helium gas or nitrogen gas, or steam or oxygen is used. In particular, it is preferable to use helium gas and / or nitrogen gas. Further, if necessary, a dispersing aid, a surface modifier and the like may be contained.

In the present invention, since the volatile titanium compound is decomposed after being vaporized or atomized, an oxygen-containing gas is required except for using an oxygen-containing compound such as alkoxide.

The decomposition temperature is preferably 600 ° C. or lower, more preferably 200 to 400 ° C., and particularly preferably 250 to 350 ° C. At a temperature lower than 200 ° C., it is difficult to obtain a sufficient decomposition rate, while at a high temperature higher than 600 ° C., it is difficult to obtain fine fine powder.

Further, in the present invention, it is preferable to rapidly cool to a temperature at which the generated fine powders do not coalesce immediately after decomposition so that they do not coalesce in the gas phase. The quenching prevents coalescence of the fine powders, and enables the obtained fine powders to be collected and recovered in the state of primary particles.

Next, the surface treatment which is another feature of the present invention will be described.

The present invention is also characterized in that the surface of the fine powder is treated with a silane-based organic compound in order to adjust the charging characteristics and to improve the stability under high humidity.

In particular, as described above, after a fine powder serving as a nucleus is generated by a gas phase method, a silane-based organic compound vaporized or atomized is immediately mixed with the fine powder, and surface treatment is performed in a gas phase. Is preferred.

The inventors proposed a TiO ₂ component and Ti
The fine powder of the composition containing the (OR) _m (OH) _n component as a main component has much higher surface activity than that of pure titanium oxide, that is, T which can react with a silane-based organic compound.
It is advantageous for the reaction because it contains more i-OH groups, and can be uniformly treated with a small amount of treating agent to increase the degree of hydrophobicity. In particular, when surface treatment is performed in the gas phase, unlike conventional wet treatment, surface treatment can be performed without taking steps such as filtration, drying, and crushing, so that uniformity is maintained without impairing the characteristics of the fine powder before treatment. In addition, the surface treatment can be sufficiently performed.

The amount and time of treatment of the silane-based organic compound with respect to the fine powder of the composition mainly composed of the TiO ₂ component and Ti (OR) _m (OH) _n are not particularly limited. Of the treated fine powder in terms of SiO ₂ is preferably 1 to 18% by weight, more preferably 1.5 to 18% by weight.
It is preferable that the surface of the fine powder is treated with a silane-based organic compound so as to be 16% by weight, more preferably 2.5 to 14% by weight.

When the Si content of the treated fine powder in terms of SiO ₂ is lower than 1% by weight, it means that the treatment was not sufficient or the treatment did not work for some reason. It tends to increase the density under high temperature and high humidity, scatter the toner at the time of durability, fog and the like. Further, when the Si amount in terms of SiO ₂ exceeds 18% by weight, this corresponds to the case where the treatment amount of the silane-based organic compound is extremely large, which is a fine powder having a small primary particle size and low cohesiveness. Is not easy to produce, resulting in a processed fine powder with many agglomerates. This makes it difficult to impart good fluidity to the toner. Due to the removal of the treating agent that could not sufficiently react with the surface of the base fine powder, a fogged and rough toner image is likely to be generated. Further, this causes a new problem of carrier contamination.

As described above, the fine powder of the composition containing the TiO ₂ component and Ti (OR) _m (OH) _n of the present invention as the main components is much finer than the conventional titanium oxide. There are many Ti-OH groups in it, so the surface activity is high, it is advantageous for the reaction with silane-based organic compounds, and the surface of the fine powder can be uniformly treated with a small amount of treating agent to increase the degree of hydrophobicity. .

In addition, when the treatment is performed in the gas phase, the amount of Si in terms of SiO ₂ can be increased without forming secondary aggregates. This is not possible with other processing methods, for example, wet processing. In other words, by simply increasing the amount of the treating agent to be added to increase the amount of Si in terms of SiO ₂ by a normal wet processing method, the amount of Si in terms of SiO ₂ itself can be increased. They tend to agglomerate, have a lower BET specific surface area and a larger apparent primary particle size than before the treatment.

On the other hand, in the case of the gas phase treatment method, the amount of Si in terms of SiO ₂ can be increased without substantially changing the value of the BET specific surface area before and after the treatment and maintaining the primary particle diameter of the base.

In the present invention, when measuring the amount of Si in terms of SiO ₂ , X-ray fluorescence spectroscopy is used.

The silane-based organic compound used in the present invention may be appropriately selected depending on the purpose of surface modification, for example, control of charging characteristics, and stabilization of charging under high humidity and reactivity. For example, compounds such as alkylalkoxysilanes, siloxanes, silanes, and silicone oils that do not themselves thermally decompose at the reaction temperature are preferred.

Particularly preferred are alkylalkoxysilanes represented by the following general formula, which have both a volatile group such as a coupling agent and a hydrophobic group and a reactive bonding group. Good to use.

R _m SiY _{n wherein} R represents an alkoxy group, m represents an integer of 1 to 3, Y represents a hydrocarbon group such as an alkyl group, a vinyl group, a glycidoxy group, and a methacryl group; Represents an integer of 1 to 3]

For example, vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, methyltrimethoxysilane, methyltriethoxysilane, isobutyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane Examples thereof include silane, trimethylmethoxysilane, hydroxypropyltrimethoxysilane, phenyltrimethoxysilane, n-hexadecyltrimethoxysilane, and n-octadecyltrimethoxysilane.

More preferably, the formula C _a H _{2a + 1} -Si-
(OC _b H _{2b + 1} ) _{3 wherein} a represents an integer of 4 to 12,
b represents an integer of 1 to 3].

Here, when a in the general formula is smaller than 4, the treatment becomes easy, but good hydrophobicity is hardly obtained.
When a is larger than 13, the hydrophobicity becomes sufficient, but the coalescence of the fine powders increases, and the fluidity imparting ability tends to decrease.

On the other hand, if b is larger than 3, the reactivity is lowered and good hydrophobicity is hardly obtained.

Therefore, in the present invention, a is preferably 4 to 12, more preferably 4 to 8, and b is preferably 1 to 3, more preferably 1 to 2.

Further, the treated fine powder of the present invention has an average particle diameter of preferably 0.005 to 5 from the viewpoint of imparting fluidity.
0.1 μm, more preferably 0.01-0.05 μm.

If the average particle size is larger than 0.1 μm, the fluidity is reduced and the toner is liable to be non-uniformly charged. As a result, toner scattering, fogging and the like are likely to occur, and it is difficult to produce a high quality toner image. . In addition, the average particle size is 0.0
When the particle size is smaller than 05 μm, the treated fine powder is easily embedded on the surface of the colorant-containing resin particles, so that the toner tends to deteriorate quickly and the durability tends to decrease. This tendency is more remarkable than when applied to a color toner having a sharp melt property.

The particle size of the treated fine powder in the present invention is measured by a transmission electron microscope.

On the other hand, in this embodiment, V _pp [V] is used as the developing bias. : Peak-to-peak voltage V _f [Hz] of the alternating voltage applied to the developer carrier : Frequency of alternating voltage applied to developer carrier V _cont [V] : Image contrast potential (potential difference from latent image potential when maximum image density is output from DC voltage of developing bias) Q [C / kg]: Average tribo of toner d [m]: Developer carrier-latent image carrier When the distance of the body is set, the alternating voltage is applied so that an alternating electric field satisfying the condition of | V _pp -2V _cont | / 16 V _f ² <d ² / | Q |

The toner used in this example has a triboelectric charge of about 2.0 × 10 ⁻² C / kg and a toner of about 3.0 × 10 ⁻² C / kg.
Two types of C / kg were used.

Next, a method for measuring the triboelectric charge (two-component developer) of the toner will be described with reference to FIG. FIG.
FIG. 3 is an explanatory diagram of an apparatus for measuring a triboelectric charge amount of a toner.

First, a two-component developer whose triboelectric charge is to be measured is put in a polyethylene bottle having a capacity of 50 to 100 ml in a metal measuring container 142 having a 500-mesh screen 143 therein. Shake by hand for about 2 seconds, add about 0.5 to 1.5 g of the developer, and close the metal lid 144. At this time, the weight of the entire measurement container 142 is measured and is set to W ₁ (kg). Next, in the suction device 141 (at least a portion in contact with the measurement container 142 is an insulator)
The air is sucked from the suction port 147, and the air volume control valve 146 is adjusted to adjust the pressure of the vacuum gauge 145 to 250 (mmAq). In this state, suction is sufficiently performed (preferably for 2 minutes) to remove the resin by suction. The potential of the electrometer 149 at this time is set to V (V). Here, 148 is a capacitor whose capacity is C (F).
And Further, the weight of the entire measurement container 142 after suction is weighed to be W ₂ (kg). The triboelectric charge amount of this toner (C / k
g) is calculated as in the following equation.

Amount of triboelectric charge of resin (C / kg) = C × V ×
10 ^-3 / (W ₁ -W ₂ )

In this embodiment, a highlight halftone image having an image density of about 0.2 and a solid image are output.
The smoothness of the highlight halftone image and the density of the solid image were evaluated. Here, the formation of the electrostatic latent image for outputting the above image is as follows. First, set the photosensitive drum to 65
It is uniformly charged to 0V. Here, when outputting a highlight halftone image, the semiconductor laser is used for PWM.
Exposure (pulse width modulation) is performed and the surface potential is increased to about 450 V
In the case of outputting a solid image, the voltage was lowered to about 100 V (V _cont = 400 V). (This example was performed by reversal development.)

Next, a description will be given of a developing process performed using the developing device having the above-described configuration and the toner having the above-described charge amount.

In this embodiment, the DC voltage is 500 V
And the intermittently applied alternating voltage amplitude V _{pp is set} to 200
It is fixed at 0 V and the frequency _Vf is changed. As described above, the toner tribo is about 2.0 × 10 ⁻² C / kg and about 3.
The image quality of the output image under the above-described latent image conditions was evaluated for two types of the image having a density of 0 × 10 ⁻² C / kg. (At this time,
As shown in FIG. 7, the time during which the alternating electric field was interrupted was set to one period for each period of the alternating electric field. )

As a result, as can be seen from Table 1 below,
_{A = | V pp -2V cont |} / 16V f 2 and B = d ² / | Q
Only when the relationship of | satisfies A <B, the solid was maintained at a high density and the reproducibility of highlight was good.

[0128]

[Table 1]

FIGS. 5 and 6 show toner 1 on the developing sleeve.
It is a figure showing the force applied to an individual. In the figure, q is the charge amount, m is the mass, a is the acceleration, ΔV is the potential difference between the photosensitive drum and the developing sleeve, and d is the gap between the photosensitive drum and the developing sleeve.

An alternating voltage is applied to the toner from the developing sleeve for 1 / (2 VF) seconds per cycle. The distance X during which the toner can move can be obtained by the following equation (1).

[0131]

(Equation 3)

The distance X _{+ at which the} toner can move from the developing sleeve in the direction of the photosensitive drum is obtained by the following equation (2).

[0133]

(Equation 4)

The distance X _{− at which the} toner can move from the photosensitive drum to the developing sleeve is obtained by the following equation (3).

[0135]

(Equation 5)

Here, the condition that the toner developed on the photosensitive drum is not returned to the developing sleeve at the moving distance X ₋ when the peeling voltage is applied for one cycle is set, so that the toner is exposed to light. Repeated bias vibration on the drum. This is, X _+> X _- due to it is.

The condition at this time is a condition such as the following equation (4) in which X ₋ is smaller than the gap d between the photosensitive drum and the developing sleeve.

[0138]

(Equation 6)

When the development is performed under such conditions, the reciprocation between the SD and the SD cannot be sufficiently performed due to the alternating electric field of one cycle, and when the alternating voltage is cut off, the DC component is changed to a latent image. Since it works so as to attract an amount of toner corresponding to the potential to the photosensitive drum, dropout of dots does not occur. Further, by intermittently repeating the vibration on the photosensitive drum, the toner is concentrated on the latent image portion, and each dot is faithfully reproduced. Therefore, only a non-uniform image can be obtained with the conventional rectangular bias. Even with a shallow latent image, a uniform image can be output.

The non-image portion is set to be higher than the DC component of the developing bias, as in this embodiment, in order to normally remove fog. For this reason, in the non-image part,
Since V _cont in Equations 2 and 3 becomes negative, X ₊
<X _- to become. Further, since the alternating voltage is cut off, the DC component works to attract the toner to the sleeve side, and the toner is further biased to the developing sleeve side, so that fog on the photosensitive drum does not occur.

In this embodiment, the alternating electric field to be applied is shown in FIG. 7, but the present invention is not limited to this. For example, as shown in FIG. 8, two wavelengths may be applied, five wavelengths may be paused, or as shown in FIG. 9, one wavelength may be applied, and ten wavelengths may be paused. In the embodiment, a rectangular wave is used.
Various applications such as a triangular wave and a sine wave can be applied, and the most appropriate application method can be selected according to the copying speed and development conditions. The ratio between the bias application time and the pause time is 1: 1 /
Preferred results were obtained at 2-1: 15.

Further, a feature of the present invention is that the fluidity of the toner is set to 20% or less by the above-mentioned measuring method. FIG. 4 shows that when the fluidity of the toner and the image density are 0.6, T / (T +
C) shows the relationship with the density fluctuation value when the ratio fluctuates by 1% from the appropriate central value. D _Max 1.8 irrespective of toner fluidity
Before and after, the concentration becomes 0.1 with increasing T / (T + C) ratio.
Although it changes before and after, at a halftone density (especially a 0.6 level density), in the method of forming an image by modulating the pulse width of the laser beam as in the present invention, the fluidity of the toner is high, % Or less, the toner tribo-distribution is sharp around the optimum value for development, so T / (T + C)
It is considered that the development was carried out sufficiently faithfully irrespective of the ratio fluctuation and reached saturation. Therefore, it is considered that even if the T / (T + C) ratio changes, the density does not easily change. Conversely, when the fluidity is poor, the halftone image is not sufficiently developed, and it is considered that when the T / (T + C) ratio rises and the amount of tribo toner suitable for development increases, the density increases. When a plurality of colors are superimposed on each other to output an image, such as a full color, this halftone density fluctuation appears as a color change. Therefore, in order to always obtain a stable image, the minimum fluctuation value is 0.1%. must suppress below, it is a permissible level of 4, the value of fluidity it is possible to 20% or less by using an external additive of the present invention, that always stable images can be obtained (As shown in FIG. 4,
If the value of the liquidity is 15% or less, the variation value is 0.05.
It is as follows. ).

In the present embodiment, titanium oxide is described. However, the same treatment as that of the present embodiment is carried out on alumina to improve the fluidity of the toner to 20% or less of the numerical value of the present invention. The effect was obtained.

[0144]

As described above, according to the present invention,
Means for applying an alternating voltage to the developer carrier so that an alternating electric field satisfying the above-mentioned conditions is formed intermittently; The use of a toner exhibiting the fluidity of the value makes it possible to make the highlight image uniform and to use the environment and T / (T
+ C) Even if the ratio fluctuates, an image having a small density fluctuation can be stably obtained.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of a developing device according to the present invention.

FIG. 2 is a sectional view of the image forming apparatus according to the embodiment of the present invention.

FIG. 3 is a configuration diagram of a measuring device for measuring a triboelectric charge amount of a two-component developer.

FIG. 4 shows the flowability of toner and T / (T + C) when D = 0.6.
It is a figure which shows the relationship of the density fluctuation by ratio fluctuation.

FIG. 5 is an explanatory diagram showing a force acting on a toner.

FIG. 6 is an enlarged explanatory view of FIG. 5;

FIG. 7 is a waveform chart showing a first example of a developing bias voltage in the present embodiment.

FIG. 8 is a waveform chart showing a second example of the developing bias voltage in the present embodiment.

FIG. 9 is a waveform chart showing a third example of the developing bias voltage in the present embodiment.

FIG. 10 is a surface potential diagram showing latent images of a solid portion and a highlight portion.

[Explanation of symbols]

1 Image Carrier (Photosensitive Drum) 111 Developer Carrier (Developing Sleeve) 112 Magnet

Continuation of the front page (56) References JP-A-6-270442 (JP, A) JP-A-2-222966 (JP, A) JP-A-7-223815 (JP, A) (58) Fields investigated (Int) .Cl. ⁷ , DB name) G03G 15/08 G03G 15/09 G03G 9/08

Claims (3)

(57) [Claims] A developing unit formed between a developer container containing a developer having toner particles and magnetic particles; and a latent image support on which an electrostatic latent image is formed. A developer carrying member that carries the developer to the developing section while carrying the developer; and a magnetic field generating means provided inside the developer carrying body, and the developing section supplies the developer to the latent image carrier. In the method, V _pp [V]: peak-to-peak voltage of the alternating voltage applied to the developer carrier _Vf [Hz]: frequency of the alternating voltage applied to the developer carrier V _cont [V]: image Contrast potential (potential difference from latent image potential when maximum image density is output from DC voltage of developing bias) Q [C / kg]: average tribo of toner d [m]: developer carrier-latent image carrier | V _pp -2V _cont | / 16V _f A means for applying an alternating voltage to the developer carrier so that an alternating electric field satisfying the condition of ² <d ² / | Q | is formed intermittently. 15 if you go
%, Wherein toner particles exhibiting a fluidity of not more than% are used. [Measurement Method] The screens are laid in the order of 200 mesh, 100 mesh, and 60 mesh from the bottom, and 5 g of the toner is placed on the 60 mesh screen. The screen is vibrated for 15 seconds, and the weight of the toner on each screen is measured after the vibration. (Equation 1) (The value calculated by the above equation is a value indicating the fluidity of the present invention, and the higher the fluidity, the smaller the value.) 2. The developing method according to claim 1, wherein the average particle size of the toner is 8 μm or less. 3. A TiO ₂ component and a Ti (OR) _m (OH) _n component [ _where R represents a hydrocarbon group, and m and n each represent an integer of 0 to 4] as an external additive of the toner. , M + n
Is 4), and a treated fine powder which has been treated with a silane-based organic compound.