JP3342460B2 - Image forming method and image forming developer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming method using electrophotography and an image forming developer used therein.

More specifically, the present invention relates to an image forming method using a charging means for charging a member to which a voltage is externally applied by bringing the member into contact with a member to be charged, and an image forming developer used for the method.

[0003]

2. Description of the Related Art Conventionally, a corona discharger has been known as a charging means in an electrophotographic apparatus. The corona discharger has a problem that a high voltage must be applied and a large amount of ozone is generated.

Recently, the use of contact charging means without using a corona discharger has been studied. Specifically, a roller is brought into contact with a member to be charged such as a photosensitive member while applying a voltage to a conductive roller as a charging member, and the surface of the member to be charged is charged to a predetermined potential. If such a contact charging means is used, the voltage can be reduced and the amount of generated ozone can be reduced as compared with a corona discharger.

For example, in Japanese Patent Publication No. 50-13661, it is possible to charge a photosensitive member by applying a low voltage by using a roller having a core covered with a dielectric material made of nylon or polyurethane rubber.

However, in the above-mentioned conventional example, the roller in which the core metal is coated with nylon does not have elasticity like rubber, so that it cannot maintain sufficient contact with the member to be charged, and tends to cause poor charging. . On the other hand, when the core metal is coated with the polyurethane rubber, the softener impregnated in the rubber gradually exudes. Therefore, when a photoreceptor is used as a member to be charged, there is a problem that the charging member is fixed to the photoreceptor at a contact portion when the photoreceptor is stopped, or an image blur occurs in a region of the contact portion. Was. When the softening agent in the rubber material of the charging member exudes and adheres to the surface of the photoreceptor, the resistance of the photoreceptor decreases and image deletion occurs.In severe cases, the toner becomes unusable or the toner remaining on the surface of the photoreceptor is charged. It may adhere to the surface of the member and cause a filming phenomenon. When a large amount of toner adheres to the surface of the charging member, the surface of the charging member is insulated, the charging ability of the charging member is lost, and the charging of the surface of the photoreceptor becomes non-uniform. This is because the residual toner is more strongly pressed against the surface of the photoreceptor against the charging member, so that the residual toner adheres to the charging member and the surface of the member to be charged, and the surface of the photoreceptor is easily damaged or scraped.

In a contact charging device, a DC voltage is applied to a charging member,
Alternatively, a voltage obtained by superimposing an AC voltage on a DC voltage is applied and used. At this time, in the vicinity of the contact portion between the charging member and the photoreceptor drum, the repetition of abnormal charging and flying motion of the residual toner particles having a small particle size and light weight is repeated. For this reason, there is a situation in which the electrostatic attraction and embedding of the residual toner on the charging member and the surface of the photosensitive drum are easily performed, and the contact charging means is very different from the case of using the non-contact charging means using the conventional corona discharger.

On the other hand, in recent years, small and inexpensive personal use copying machines and laser printers have appeared. In these small machines, it is preferable to use a cartridge system in which members such as a photoconductor, a developing device, and a cleaning device are integrated from a maintenance-free standpoint. Further, it is preferable to use a one-component dry magnetic developer because the structure of the developing device can be simplified as the developer to be used.

As a method using a magnetic toner, for example, a magneto-dry method using a conductive toner described in US Pat. No. 3,909,258; a method using dielectric polarization of toner particles; A method of transferring a charge by disturbing the latent image as described in JP-A-54-42141 and JP-A-55-18656.

In such a method using a dry magnetic developer, in order to form a visible image of good image quality, it is necessary that the developer has high fluidity and uniform chargeability. For this purpose, fine silica powder has conventionally been added to and mixed with toner powder. Silicic acid fine powder (ie, silica) itself is hydrophilic, and therefore, the developer to which it is added may cause agglomeration due to the moisture in the air to reduce the fluidity, or in extreme cases, the fine silica powder may be used. Moisture absorption lowers the charging performance of the developer. Accordingly, use of hydrophobized silica fine powder is disclosed in JP-A-46-5782 and JP-A-48-47345.
And JP-A-48-47346. Specifically, for example, a silicic acid fine powder which has been hydrophobized by reacting a silicic acid fine powder with an organosilicon compound such as dimethyldichlorosilane and substituting an organic group for a silanol group on the surface of the silicic acid fine powder is used. I have.

The magnetic toner itself has a polishing effect. Organic photoconductor (OPC) as photoreceptor
In an image forming process in which pressure contact with a photoreceptor having a low surface hardness is performed, especially in a developer in which a magnetic toner and an inorganic fine powder are mixed, a white drop phenomenon caused by scraping both the pressure contact member and the photoreceptor surface, Damage to the pressing member and the photoreceptor, and contamination of the photoreceptor such as toner fusing and filming are likely to occur.

Japanese Patent Application Laid-Open No. 60-186854 proposes to add polymer particles smaller than toner particles. When a developer was prepared and examined in the same manner as above, there was no effect on fusion of the toner on the photoreceptor, and in an apparatus using contact charging, there was a tendency that the contact charging device was contaminated to cause uneven charging.

In recent years, as the performance of host computers has become higher, a laser beam printer having a higher printing speed has been required. From the viewpoint of the office environment, an image forming apparatus that does not generate ozone has been desired.

In general, in contact charging, as the process speed increases, it is necessary to increase the applied voltage and the AC frequency in order to stabilize the charging on the photosensitive member. At the same time, there is a problem that the developer is easily fused to the photosensitive member.

In recent years, the demand for image quality has also become increasingly severe, and it has been demanded that even very fine latent images be faithfully reproduced without being crushed or cut off. Along with this, the particle size of the toner tends to be reduced. For example, JP-A-1-112253 proposes a developer having a volume average particle size of 4 to 9 μm.

In general, the smaller the particle size of the toner, the larger the specific surface area of the toner. Therefore, when the toner is used, the contact member and the photoconductor are easily contaminated.
Since the cohesiveness of the toner is increased, it is necessary to add more inorganic fine powder to ensure the fluidity. As a result, the whitening phenomenon caused by scraping the surface of the pressure-contact member and the photoreceptor, the pressure-contact member and the photoreceptor There is a tendency that fusion of the toner, filming, etc. due to scratching are promoted and image defects are caused.

[0017]

SUMMARY OF THE INVENTION The present invention provides an image forming method in which toner fusion does not occur on a photoreceptor or toner fusion is suppressed, and an image forming developer used therefor. The purpose is to:

An object of the present invention is to provide an image forming method capable of obtaining a toner image having a high density and no fog, and an image forming developer used for the method.

An object of the present invention is to provide an image forming method which does not easily contaminate a contact charging device and an image forming developer used for the method.

It is an object of the present invention to provide an image forming method that hardly causes uneven charging of a photoreceptor by a contact charging device, and an image forming developer used therein.

An object of the present invention is to provide an image forming method having at least a contact charging means and a developing means for developing with the developer of the present invention, and an image forming developer used therefor.

[0022]

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

According to the present invention, the charging member to which the charging bias voltage of the contact charging means is applied to the member to be charged is 5 to 500 g.
A charging step of charging the charged body by contacting with a contact pressure of / cm; an exposing step of exposing the charged charged body to form an electrostatic charge image on the surface of the charged body; developing step of developing by developing means the electrostatic image carried on the body; an image forming method having a the charging bias
And a DC voltage of at least -200 to -900 V
The developing means has a developer having a negatively-chargeable magnetic toner containing at least a magnetic substance as a binder resin and a colorant, and a hydrophobic inorganic fine powder.
The negatively-chargeable magnetic toner has a volume average particle diameter of 4-8 μm, 17-60% by number of magnetic toner particles having a particle diameter of 5 μm or less, and 5-50% of magnetic toner particles having a particle diameter of 6.35-10.08 μm.
1. Magnetic toner particles having a number% and a particle size of 12.7 μ or more
The hydrophobic inorganic fine powder is treated with at least silicone oil or silicone varnish, and the developer has a BET specific surface area of 1.8 to 3.5 m. ² / g, a loose apparent density of 0.4 to 0.52 g / cm ³ , and a true density of 1.4.
The present invention relates to an image forming method characterized by a weight of 5 to 1.8 g / cm ³ .

Further, according to the present invention, the charging member to which the charging bias voltage of the contact charging means is applied to the member to be charged is 5 to 5 times.
A charging step of charging the object to be charged by contacting with a contact pressure of 00 g / cm; an exposing step of exposing the charged object to form an electrostatic image on the surface of the object; an electrostatic image carried on the charged body developing step of developing with a developer is developing means has; an image forming developer used in the image forming method having, the charging bias
As a DC voltage of at least -200 to -900V
Developer are applied has a negatively chargeable magnetic toner and hydrophobic inorganic fine powder that contains at least a magnetic material as a binder resin and a colorant, the negatively chargeable magnetic toner 17-60% by number of magnetic toner particles having a volume average particle diameter of 4-8 μm and a particle diameter of 5 μm or less, and a particle diameter of 6.35-1.
It has a particle size distribution containing 5 to 50% by number of 0.08 μm magnetic toner particles and 2.0% by volume or less of magnetic toner particles having a particle diameter of 12.7 μm or more, and the hydrophobic inorganic fine powder has at least The developer is treated with silicone oil or silicone varnish, and the developer has a BET specific surface area of 1.
8 to 3.5 m ² / g, and a loose apparent density of 0.4 to
0.52 g / cm ³ and a true density of 1.45 to 1.8
g / cm ³ .

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION The magnetic toner contained in the developer used in the present invention has a volume average particle diameter of 4 to 8 (preferably 6 to 8) .mu.m. It is preferred in that respect. Further, the developer having a magnetic toner has a BET specific surface area of 1.8 to 3.5 m ² / g, a loose apparent density of 0.4 to 0.52 g / cm ³ , and a true density of 1.
Since it is 45 to 1.8 g / cm ^3, it is more preferable in terms of the resolution of the developer and the suppression of fog.

The BET specific surface area of the developer according to the present invention measured by a nitrogen gas adsorption method is 1.8 to 3.5 m ² / g, and within this range, the developer of the present invention has a rapid rise.
The developer efficiency is good, and the effect of preventing fusion of the toner on the photoconductor is high.

The true specific gravity of the developer according to the present invention is 1.45 to 1.45.
In this range, the developer of the present invention has an appropriate amount of the latent image upon development, and has a high density that is faithful to the latent image without becoming thicker or thinner. An image is obtained. If the true specific gravity is less than 1.45, the inside of the apparatus is easily contaminated by scattering of the developer, and toner fusing on the photoreceptor is liable to occur due to increase in fog.

The loose apparent density of the developer according to the present invention is 0.4 to 0.52 (g / cm ³ ), which is characteristic that the loose apparent density is smaller than the true specific gravity. It is. The porosity calculated from the true specific gravity and the loose apparent density is 6
Preferably it is 2 to 75%.

The porosity (ε _a ) is calculated by the following equation.

[0030]

[Outside 1]

The solidified apparent density of the developer is preferably in the range of 0.8 to 1.0, and the porosity (ε _p ) at this time is 40 to 50.
% Is preferred.

Within this range, the developer of the present invention is always stable without causing clogging of the developer inside the developing device, and smoothly supplying the developer to the developing section without causing white spots. The density can be maintained, the toner does not leak or scatter, and even in a large number of print tests, the toner does not deteriorate and the fusion of the toner to the photoreceptor can be prevented.

The BET specific surface area of the developer containing the magnetic toner is determined by a BET one-point method using a specific surface area meter Autosoap 1 manufactured by QUANTACHROME.

The loose apparent density in the present invention was measured using a powder tester manufactured by Hosokawa Micron Co., Ltd. and a container attached to the powder tester, according to the procedure described in the instruction manual for the powder tester.

In the measurement of the true density in the present invention, when measuring fine powder, the following method was adopted as an accurate and simple method.

Stainless steel inner diameter 10mm, length about 5c
m cylinder with an outer diameter of approximately 10
A disk (A) having a height of 5 mm and a height of 5 mm, and a piston (B) having an outer diameter of about 10 mm and a length of about 8 cm are prepared. The disk (A) is placed at the bottom of the cylinder, then about 1 g of the measurement sample is placed, and the piston (B) is gently pushed. A force of 400 kg / cm ² is applied to this with a hydraulic press, and a product compressed for 5 minutes is taken out. The weight of the compressed sample is weighed (wg), and the diameter of the compressed sample (D
cm) and height (Lcm), and the true density is calculated by the following equation.

[0037]

[Outside 2]

The magnetic toner according to the present invention has a volume average particle diameter of 4 to 8 (preferably 6 to 8) μm,
It contains 17 to 60% by number of magnetic toner particles having a particle size of not more than μm, and contains 5 to 50% by number of magnetic toner particles having a particle size of 6.35 to 10.08 μm, and 12.7%
2.0% by volume of magnetic toner particles having a particle size of not less than μm
It has a particle size distribution contained below. Further 5 μm
The following magnetic toner particle group has the following formula

[0039]

[Outside 3] [Wherein N represents the number% of magnetic toner particles having a particle size of 5 μm or less, V represents the volume% of magnetic toner particles having a particle size of 5 μm or less, and k represents 4.6 to 6.7. Indicates a positive number. Here, N indicates a positive number of 17 to 60. Is preferable.

If the volume average particle diameter of the magnetic toner is less than 4 μm, the amount of toner on the transfer paper is small and the image density tends to be low in applications where the image area ratio is high, such as graphic images. This is considered to be due to the same reason that the density inside the edge portion in the latent image described later decreases. Further, the volume average particle diameter of the magnetic toner is 4 μm.
If it is less than 3, toner fusion is likely to occur on the photoconductor.

When the volume average particle diameter of the magnetic toner exceeds 8 μm, the resolution is not good, and the image quality tends to be deteriorated due to durability. When the number of magnetic toner particles having a particle diameter of 5 μm or less is less than 17% by number, the amount of magnetic toner particles effective for high image quality is small. In particular, as the toner is used by continuing printout, the effective magnetic toner particle component is reduced. As a result, the dispersion of the particle size distribution of the magnetic toner as shown in the present invention becomes worse, and the image quality gradually decreases. If it exceeds 60% by number, the magnetic toner particles tend to agglomerate with each other, resulting in a toner mass larger than the original particle size, resulting in rough image quality, reduced resolution, and an edge portion between the latent image and the interior. , The image tends to be slightly hollow, and the toner on the photosensitive member is easily fused.

The particle size in the range of 6.35 to 10.08 μm is preferably 5 to 50% by number or less, more preferably 8 to 50% by number.
40% by number is good. When the content is more than 50% by number, the image quality is deteriorated, and the development more than necessary (that is, the excessive amount of toner) occurs, the fine line reproducibility is reduced, and the toner consumption tends to be increased. On the other hand, if it is less than 5% by number, it becomes difficult to obtain a high image density. Number% (N%) and volume% (V%) of magnetic toner particles having a particle size of 5 μm or less
Has a relationship of N / V = −0.05N + k,
Indicates a positive number in the range of 4.6 ≦ k ≦ 6.7. Preferably 4.6 ≦ k ≦ 6.2, more preferably 4.6 ≦ k ≦
5.7. As indicated above, 17 ≦ N ≦ 60, preferably 25 ≦ N ≦ 60, more preferably 30 ≦ N ≦
60.

When k <4.6, the number of magnetic toner particles having a particle diameter smaller than 5.0 μm is small, and the image density, resolution, and sharpness are poor. The appropriate presence of fine magnetic toner particles, which was conventionally considered unnecessary, contributes to the closest packing of the toner in the development and contributes to the formation of a uniform image without roughness. In particular, by uniformly filling the fine lines and the contours of the image, the sharpness is further enhanced visually. When k <4.6, these properties are inferior due to the lack of the particle size distribution component.

From another viewpoint, in production, it is necessary to cut a large amount of fine powder by classification or the like to satisfy the condition of k <4.6, which is disadvantageous in terms of yield and toner cost. Becomes If k <6.7, the image density tends to decrease while printing repeatedly, due to the presence of fine powder more than necessary. It is thought that such a phenomenon occurs when excessive fine magnetic toner particles having an unnecessary charge are charged and adhered to the developing sleeve, thereby hindering the normal carrying of the magnetic toner on the developing sleeve and the charge application. Can be When k <6.7, toner fusion on the photoconductor is likely to occur.

The content of the magnetic toner particles having a particle diameter of 12.7 μm or more is preferably 2.0% by volume or less, more preferably 1.0% by volume or less, and further preferably 0.5% by volume or less. . If it is more than 2.0% by volume, it tends to hinder reproduction of fine lines.

The particle size distribution of the magnetic toner can be measured by various methods. In the present invention, the measurement was performed using a Coulter counter.

As a measuring device, Coulter Counter T
An interface (manufactured by Nikkaki) that outputs the number distribution and volume distribution using A-II type (manufactured by Coulter) and CX
-1 Connect a personal computer (Canon),
As an electrolytic solution, an approximately 1% NaCl aqueous solution is prepared using primary sodium chloride. As a measuring method, the electrolytic solution 100
0.1 to 5 ml of a surfactant, preferably an alkylbenzenesulfonate, is added as a dispersant in ~ 150 ml;
Further, 2 to 20 mg of a measurement sample is added. The electrolyte in which the sample is suspended is subjected to dispersion treatment for about 1 to 3 minutes with an ultrasonic disperser,
Using the Coulter Counter TA-II, a particle size distribution of 2 to 40 μm particles is measured based on the number, using a 100 μ aperture as an aperture, and then a value according to the present invention is determined.

The magnetic toner of the developer of the present invention contains a binder resin and a magnetic substance.

The binder resin of the magnetic toner according to the present invention is, for example, a homopolymer of styrene such as polystyrene and polyvinyltoluene and a substituted product thereof: styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-
Vinyl naphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-dimethylaminoethyl acrylate Polymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-dimethylaminoethyl methacrylate copolymer, styrene-vinyl methyl ether copolymer Polymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer Styrenic copolymers such as coalesced Methyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyethylene, polypropylene, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin , Paraffin wax, carnauba wax and the like. These can be used alone or in combination.

As the magnetic particles contained in the magnetic toner according to the present invention, a substance which is magnetized when placed in a magnetic field is used. For example, ferromagnetic metal powders such as iron, cobalt, and nickel; or alloys and compounds such as iron-based alloys, nickel-based alloys, magnetite, γ-Fe ₂ O ₃ , and ferrite can be used.

[0051] These magnetic fine particles are made of B by a nitrogen adsorption method.
The ET specific surface area is preferably 1 to 20 m ² / g, particularly 2.5 to 12 m ² / g, and the Mohs hardness is 5 to 5 m ² / g.
7 is preferred. The content of the magnetic powder is preferably from 10 to 70% by weight based on the weight of the toner.

Further, the magnetic toner has a bulk density of 0.35.
It is preferable to contain magnetic particles of g / cm ³ or more.

The developer of the present invention having the above-mentioned structure allows the toner on the surface of the contact charging member and the surface of the photosensitive drum to be removed even if a small amount of the residual developer remains on the photosensitive drum after the cleaning step. Is extremely unlikely to stick.

As described above, the developer according to the present invention has a very good matching with the charging step according to the present invention, makes it possible to sufficiently exhibit the capability of the charging step, and can always perform good image formation. .

The present inventors believe that the reason why the developer according to the present invention exerts the above effects is due to the uniform dispersion of the magnetic particles in the magnetic toner of the developer. If uniform dispersion is not realized, in the rich part of the magnetic material, not only the ratio of the magnetic material exposed to the surface becomes high, but also the ratio of the binder resin decreases, so that the elasticity decreases, Because of the mechanical pressure and the electric pressure in the DC or AC electric field due to the voltage applied to the charging member at the contact portion of the photoreceptor surface with the contact charging member, strong rubbing is performed on both member surfaces, Scratches and abrasions are likely to occur. Conversely, in the rich portion of the binder resin, the viscoelasticity increases because of the decrease in the proportion of the magnetic material, so that the charging member or the photosensitive member surface has a dot-like shape.
Alternatively, a phenomenon of sticking to a film is likely to occur.

The bulk density of the magnetic material is determined by the existence of aggregates of magnetic particles.
It can be understood that it indicates the abundance indirectly. Magnetic
The bulk density of the body is 0.35 g / cm^ThreeIf less than magnetic
There are many aggregates in the body,
And it is difficult to obtain sufficient dispersibility. For this reason, the bias of the magnetic body
Causes scratches and scrapes on the contact charging member and photoreceptor surface.
Cheating. Further, at the contact portions of the two members, the fixing
Easy to cause elephants. Good content of magnetic material in developer
In order to obtain scatter, the bulk density is 0.35 g / cm ^Threethat's all,
Preferably 0.5 g / cm^ThreeUse a magnetic material with the above
Good to do.

In the present invention, the bulk density of the magnetic material
A value measured by IS (Japanese Industrial Standard) K-5101.

The magnetic material contained in the developer according to the present invention has a coercive force (Hc) of 100 Oersted (Oe) or less under a magnetic field of 10,000 Oersted (Oe).
, And more preferably 80 oersted (Oe) or less. It can be understood that the coercive force of the magnetic particles is dominated by crystal magnetic anisotropy and shape anisotropy, and indirectly defines the surface shape. When the magnetic material becomes crystalline, the coercive force increases and the magnetic particles have sharp edges on the surface.
When a developer containing such magnetic particles having an edge portion on the surface is used in the present invention, not only is the contact charging member and the photosensitive drum surface scratched or scraped, but also in the contact portions of both members. The fixing phenomenon due to the embedding of the developer is likely to occur. Therefore, it is preferable to reduce the coercive force of the magnetic particles and make the surface substantially close to a curved surface. However, since the coercive force may show a value of 100 Oersted (Oe) or less even when the magnetic particles form an aggregate, the bulk density is 0.35 g / cm ³ or more even in this case. Is preferred.

Further, the magnetic substance contained in the magnetic toner according to the present invention is not more than 10 emu / g, preferably 7 emu / g under a magnetic field of 10,000 Oersted (Oe).
It is preferable to use magnetic particles having a residual magnetization (σr) of not more than g. When the residual magnetization of the magnetic material is larger than 10 emu / g, the magnetic aggregation of the magnetic particles increases, and the magnetic particles tend to be present as aggregates in the magnetic toner particles. It is not preferable because the developer causes a fixing phenomenon on the body surface.

The magnetic properties of the magnetic material refer to values measured by, for example, VSMP-1 manufactured by Toei Industry Co., Ltd.

The magnetic material according to the present invention is preferably produced by a wet method using ferrous sulfate as a raw material and contains 0.1 to 10% by weight of a divalent metal compound such as manganese or zinc. It is preferably formed from magnetite or ferrite.

The magnetic material contained in the magnetic toner according to the present invention is preferably subjected to a crushing treatment if necessary. As means used to crush the magnetic material, a mechanical crusher having a high-speed rotor for crushing the powder, and a weight roller for dispersing or crushing the powder. The provided pressure disperser is exemplified.

When the aggregate of magnetic particles is crushed using a mechanical pulverizer, the impact force of the rotor is likely to be excessively applied to the primary particles of the magnetic particles, and the primary particles themselves are destroyed. Thus, fine powder of magnetic particles is easily generated. Therefore, when a magnetic material that has been crushed by a mechanical pulverizer is used as a raw material for a toner, if a large amount of fine magnetic particles is present, the ratio of the magnetic fine particles that are exposed on the developer surface increases. For this reason, the polishing effect of the developer itself is enhanced, which deviates from the characteristics originally required.

On the other hand, a pressure disperser having a weight roller such as a fred mill is preferable in terms of the efficiency of the crushing process of the aggregates of the magnetic particles and the suppression of the generation of the fine magnetic particles.

The magnetic toner according to the present invention is preferably negatively charged. If necessary, a charge control agent may be contained, and a negative charge control agent such as a metal complex salt of a monoazo pigment or a metal complex salt of salicylic acid, alkylsalicylic acid, dialkylsalicylic acid or naphthoic acid is used. Further, the magnetic toner according to the present invention preferably has a volume resistivity of 10 ¹⁰ Ω · cm or more, particularly 10 ¹² Ω · cm or more, in view of triboelectric charge and electrostatic transferability. The volume resistivity referred to here is determined by molding the toner at a pressure of 100 kg / cm ² ,
cm is applied, and is defined as a value converted from a current value one minute after the application.

As the binder resin of the magnetic toner contained in the developer of the present invention, a polymerizable monomer unit having a carboxyl group or an acid group composed of an acid anhydride thereof is 3 to 30 parts by weight in 100 parts by weight of the binder resin. Parts by weight, preferably 3-20
It is particularly preferable to use a binder resin having a weight part and an acid value of 1 to 70.

In the present invention, various resins can be used as the binder resin, but tetrahydrofuran (T
HF) The molecular weight distribution of the soluble component by gel permeation chromatography (GPC) is such that the weight average molecular weight / number average molecular weight (Mw / Mn) ≧ 5, and the molecular weight is 2,000 or more and less than 15,000, preferably 2,000. ~ 1
It has a peak in the region of 0000 and a molecular weight of 15,000.
Resins having peaks or shoulders in the range of 0 to 100,000 are preferred. This means that the THF-insoluble component mainly affects the offset resistance and the magnifying property, and the THF-soluble component having a molecular weight of less than 15,000, particularly a component having a molecular weight of 10,000 or less, is mainly blocking, and is fused to the photoreceptor. Affects the filming properties and the molecular weight of the THF-soluble component 10,
This is based on the fact that the components of 000 or more, especially 15,000 or more mainly affect the fixing property.

The copolymer containing a carboxyl group or an acid group composed of an acid anhydride group thereof may be contained in any one or both of the molecular weight distribution regions.

In the present invention, the peak of the chromatogram by GPC (gel permeation chromatography) or / and the molecular weight of the shoulder are measured under the following conditions.

The column was stabilized in a 40 ° C. heat chamber, and tetrahydrofuran was passed through the column at this temperature as a solvent at a flow rate of 1 ml per minute, and the THF of the resin was adjusted to a sample concentration of 0.05 to 0.6% by weight. Measure by injecting 50 to 200 μl of the sample solution. In measuring the molecular weight of the sample, the molecular weight distribution of the sample was calculated from the relationship between the logarithmic value of a calibration curve prepared from several types of monodisperse polystyrene standard samples and the count number. As a standard polystyrene sample for preparing a calibration curve, for example, Press
ure Chemical Co. Or Toyo Soda Kogyo Co., Ltd. having a molecular weight of 6 × 10 ² , 2.1 × 10 ³ , 4 × 10
³ , 1.75 × 10 ⁴ , 5.1 × 10 ⁴ , 1.1 × 10 ⁵ ,
3.9 × 10 ⁵ , 8.6 × 10 ⁵ , 2 × 10 ⁶ , 4.48
It is suitable to use × 10 ⁶ and to use at least about 10 standard polythiolylene samples. An RI (refractive index) detector is used as the detector.

In order to accurately measure the molecular weight region of 10 ³ to 4 × 10 ^6, a plurality of commercially available polystyrene gel columns may be used in combination.
Μ-styragel 500, 10 ³ , 10 ⁴ ,
10 ⁵ combination or, manufactured by Showa Denko KK of Shodex KF
-80M or a combination of KF-802, 803, 804, 805, or TSKgel G100 manufactured by Toyo Soda
0H, G2000H, G2500H, G3000H, G
4000H, G5000H, G6000H, G7000
A combination of H and GMH is preferred.

The weight% of the binder resin having a molecular weight of 10,000 or less according to the present invention is obtained by cutting out a molecular weight of 10,000 or less in a chromatogram by GPC and obtaining a molecular weight of 10,000 or less.
The weight ratio to the cutout of 00 or more is calculated, and the weight% with respect to the entire binder resin is calculated.

Examples of the polymerizable monomer having an acid group that can be used in the present invention include the following.

Α, β such as acrylic acid and methacrylic acid
-Unsaturated carboxylic acids; α, β-unsaturated dicarboxylic acids or half esters thereof such as maleic acid, butyl maleate, octyl maleate, fumaric acid, butyl fumarate; n-butenyl succinic acid, n-octenyl succinic acid; Alkenyl dicarboxylic acids such as n-butyl succinate, n-butenyl malonic acid, n-butenyl adipic acid and the like, and half esters thereof and the like can be mentioned.

In this case, the amount of the polymerizable monomer containing an acid group is preferably 3 to 30 parts by weight based on the total amount of the binder resin.
The acid value of the entire binder resin is preferably 1 to 70, more preferably 5 to 50.

The method for measuring the acid value used in the present invention is described below.

The acid value is measured according to JIS K-0670.

Samples 2 to 10 g in 200 to 300 ml
Weighed in an Erlenmeyer flask, and ethanol: benzene = 1: 1
About 50 ml of the mixed solvent of No. 2 is added to dissolve the resin. If solubility is poor, a small amount of acetone may be added.
Using a phenolphthalein indicator, titration is performed with a previously standardized N / 10 potassium hydroxide-ethanol solution, and the acid value (mg KOH / g) is determined from the consumption of the potassium hydroxide solution by the following formula (3).

Oxidation = KOH (ml) × N × 56.1 / sample weight (3) (where N is a factor of N / 10 KOH)

The comonomers for obtaining the binder resin having an acid group according to the present invention include the following.

For example, styrene, 0-methylstyrene, m
-Methylstyrene, p-methylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, p-ethylstyrene,
2,4-dimethylstyrene, pn-butylstyrene,
Styrene derivatives such as p-tertbutylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene, p-n-dodecylstyrene; ethylene, propylene, butylene , Ethylenically unsaturated monoolefins such as isobutylene; unsaturated polyenes such as butadiene; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide, and vinyl fluoride; vinyl acetate, vinyl propionate;
Vinyl esters such as vinyl benzoate; methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, methacrylic acid Α-methylene aliphatic monocarboxylic esters such as stearyl, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate; N-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate Acrylates such as phenyl acrylate; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and methyl isopropenyl ketone; N-vinyl pyrrole; Vinyl carbazole, N
N- such as vinylindole and N-vinylpyrrolidone
Vinyl compounds; vinyl naphthalenes; acrylonitrile,
Acrylic acid derivatives such as methacrylonitrile and acrylamide or methacrylic acid derivatives are exemplified.

These vinyl monomers are used alone or in combination of two or more with the monomers having an acid group.

Among these, a combination of monomers that results in a styrene copolymer and a styrene acrylic copolymer is preferred.

As the crosslinkable monomer, a monomer having two or more polymerizable double bonds is mainly used.

The vinyl copolymer used in the present invention is:
It is preferably a polymer cross-linked with a cross-linkable monomer as exemplified below.

Aromatic divinyl compounds (eg, divinylbenzene, divinylnaphthalene); diacrylate compounds linked by an alkyl chain (eg, ethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,4-butanediol) Diacrylate,
1,5-pentanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, and methacrylate in place of the acrylate of the above compound); diacrylate linked by an alkyl chain containing an ether bond Compounds (eg,
Diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol # 400 diacrylate, polyethylene glycol # 600 diacrylate, dipropylene glycol diacrylate, and methacrylate instead of the above compound); Diacrylate compounds linked by a chain containing an aromatic group and an ether bond [for example, polyoxyethylene (2) -2,2-bis (4-hydroxyphenyl) propane diacrylate, polyoxyethylene (4) -2 ,
2-bis (4-hydroxyphenyl) propane diacrylate and acrylates of the above compounds, instead of methacrylates]; and polyester-type diacrylate compounds [for example, trade name MANDA (Nippon Kayaku)] Is raised.

As the polyfunctional crosslinking agent, pentaerythritol triacrylate, trimethylolethane triacrylate, trimethylolpropane triacrylate, tetramethylolmethanetetraacrylate, oligoester acrylate, and acrylates of the above compounds are used instead of methacrylate. And triallyl cyanurate and triallyl trimellitate.

These cross-linking agents may be used in combination with other monomer components 10
It is preferable to use about 0.01 to 5 parts by weight (more preferably about 0.03 to 3 parts by weight) with respect to 0 parts by weight.

Among these crosslinkable monomers, those which are preferably used in toner resins from the viewpoint of fixing properties and anti-offset properties include aromatic divinyl compounds (particularly divinylbenzene), aromatic groups and ether bonds. And diacrylate compounds linked by a chain.

The method for synthesizing the binder resin according to the present invention is preferably a method for synthesizing two or more polymers or copolymers.

This is a method in which a first polymer or copolymer soluble in THF and soluble in a polymerizable monomer is dissolved in the polymerizable monomer, and the monomer is polymerized to obtain a resin composition.
In this case, a composition is formed in which the former and the latter polymers or copolymers are uniformly mixed.

The first polymer or copolymer soluble in THF is preferably solution polymerization or ionic polymerization.
The second polymer or copolymer for producing the component insoluble in HF is prepared by suspension polymerization or bulk polymerization in the presence of a crosslinkable monomer under conditions in which the first polymer or copolymer is dissolved. It is preferable to synthesize with. The first polymer or copolymer is used in an amount of 10 to 120 (preferably 20 to 100 parts by weight) based on 100 parts by weight of the polymerizable monomer for forming the second polymer or copolymer. Is preferred.

As a solvent used in the solution polymerization, xylene, toluene, cumene, acid cellosolve, isopropyl alcohol, benzene and the like are used. In the case of a styrene monomer, xylene, toluene or cumene is preferred.
It is appropriately selected depending on the polymer to be polymerized. The initiator is di-tert-butyl peroxide, tert-butyl
-Butylperoxybenzoate, benzoyl peroxide, 2,2'-azobisisobutyronitrile, 2,
2'-Azobis (2,4 dimethylvaleronitrile) or the like is used at a concentration of 0.1 part by weight or more (preferably 0.4 to 15 parts by weight) based on 100 parts by weight of the monomer. The reaction temperature varies depending on the solvent used, the initiator, and the polymer to be polymerized, but is preferably from 70 ° C to 180 ° C. In the solution polymerization, it is preferable to perform the polymerization at 30 parts by weight to 400 parts by weight with respect to 100 parts by weight of the solvent.

The binder resin used in the present invention preferably has a THF-insoluble content of 10 to 70%. If the THF-insoluble content is less than 10% by weight, the magnetic toner tends to stick to the contact charging member.

When the THF-insoluble content exceeds 70% by weight, the strength of the toner itself becomes too large, and the surface of the latent image carrier or the surface of the contact member may be damaged by contact charging, and conversely, it may be easily fixed. is there.

The THF-insoluble component in the present invention indicates the weight ratio of the polymer component (substantially cross-linked polymer) insoluble in the THF solvent in the resin composition in the magnetic toner, and includes the cross-linking component. It can be used as a parameter indicating the degree of crosslinking of the resin composition. The THF-insoluble matter is defined by a value measured as follows.

0.5 to 1.0 g of the toner sample was weighed (W ₁ g), and a cylindrical filter paper (for example, No. 86 manufactured by Toyo Roshi Kaisha, Ltd.) was used.
R) and run through a Soxhlet extractor, where T
After extracting with 100 to 200 ml of HF for 6 hours and evaporating the soluble component extracted with the solvent, 10
After vacuum drying for several hours at 0 ° C., the amount of the THF-soluble resin component is weighed (W ₂ g). The weight of a component other than the resin component such as a magnetic substance or a pigment in the magnetic toner is defined as (W ₃ g). T
The HF insoluble content is obtained from the following equation.

[0098]

[Outside 4]

In the present invention, the molecular weight of the peak or / and the shoulder of the chromatogram by GPC (gel permeation chromatography) is measured under the following conditions.

The developer of the present invention preferably has a hydrophobic inorganic fine powder as an additive. The hydrophobic inorganic fine powder is preferably a hydrophobic metal oxide fine powder, and more preferably a hydrophobic silicic acid (silica) fine powder.

Among the inorganic fine powders, the BET specific surface area by nitrogen adsorption measured by the BET method is 70 to 300 m ^2.
/ G gives good results. Hydrophobic silica fine powder 0.1 to 3. based on 100 parts by weight of magnetic toner.
0 parts by weight, preferably 0.2 to 2.0 parts by weight is used.

As the hydrophobic silica fine powder, a negatively charged hydrophobic silica fine powder is preferable for a negatively charged magnetic toner.

As the hydrophobic silica fine powder used in the present invention, those having a triboelectric charge of -100 μc / g to −300 μc / g are preferably used. Tribo charge is -10
If less than 0 μc / g, the triboelectricity of the developer itself is reduced, and the humidity characteristics tend to be reduced. -3
If the amount exceeds 00 μc / g, the memory of the developer-carrying member is promoted, and the developer is liable to be affected by silica deterioration or the like, which tends to impair the durability characteristics. BET
Those having a specific surface area of less than 300 m ² / g have little effect on the addition to the developer, and those having a specific surface area of more than 70 m ² / g have a high probability of being present as a free substance, causing uneven distribution of silica and generation of black spots due to aggregation of silica. Easy to cause.

In the present invention, examples of the hydrophobizing agent for treating the inorganic fine powder include a silane coupling agent, silicone oil, and silicone varnish.

Silicon oil and silicone varnish are more preferable than silane coupling agents in terms of hydrophobicity and lubricity.

The silicone oil or silicone varnish used in the present invention generally includes those represented by the following formula:

[0107]

[Outside 5] [R: C ₁ ~ ₃ alkyl group R ': alkyl, halogen-modified alkyl, phenyl, silicone oil modified group R of the modified phenyl such as ": alkyl or Arukookishi group of C ₁ ~ _3]

For example, dimethyl silicone oil, alkyl-modified silicone oil, α-methylstyrene-modified silicone oil, chlorophenyl silicone oil, and fluorine-modified silicone oil can be used. Preferably, the silicone oil has a viscosity at 25 ° C. of about 50 to 1000 centistokes. Silicone oil having a molecular weight that is too low may generate volatile components due to heat treatment or the like. If the molecular weight is too high, the viscosity becomes too high and the processing operation becomes difficult.

A known technique can be used for the silicon oil treatment method.

For example, silica fine powder and silicon oil may be directly mixed using a mixer such as a Henschel mixer, or a method of spraying silicon oil onto base silica may be used. After dissolving or dispersing the silicone oil in an appropriate solvent, it may be mixed with a base silica fine powder, and then the solvent may be removed to form hydrophobic silica.

It is more preferable that the inorganic fine powder used in the present invention is first treated with a silane coupling agent, and then treated with silicon oil or silicone varnish.

In general, the silicon oil treatment alone requires a large amount of silicon oil to cover the surface of the fine powder, so that agglomerates of the fine powder are likely to be formed during the processing, and when applied to a developer, the fluidity of the developer may be deteriorated. It is conceivable that the silicon oil treatment process requires careful attention. Therefore, in order to remove the agglomerates of the fine powder while maintaining good moisture resistance, it is better to treat the silica fine powder with a silane coupling agent and then treat it with silicon oil to achieve the silicon oil treatment effect more sufficiently. That is.

The silane coupling agent used in the present invention is hexamethyldisilazane or a general formula RmSiYn R: an alkoxy group or a chlorine atom m: an integer of 1 to 3 Y: an alkyl group vinyl group, glycidoxy group, methacryl group And n is an integer of 3 to 1, and typically includes, for example, dimethyldichlorosilane, trimethylchlorosilane, allyldimethylchlorosilane, allylphenyldichlorosilane, benzyldimethylchlorosilane, and vinyltrichlorosilane. Ethoxysilane, γ-
Examples include methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, divinylchlorosilane, and dimethylvinylchlorosilane.

The fine powder can be treated with a silane coupling agent by a dry treatment in which the fine powder is converted into a cloud by stirring and a vaporized silane coupling agent is reacted, or the fine powder is dispersed in a solvent to form a silane coupling agent. Can be treated by a wet method in which the reaction is carried out dropwise.

In the present invention, the processing amount of silicon oil or silicon varnish is 1 to 100 parts by weight of inorganic fine powder.
-35 parts by weight, more preferably 2-30 parts by weight.
If the treatment amount of the silicone oil or the silicone varnish is too small, the moisture resistance is not improved, and the fine powder may absorb moisture under high humidity, so that a high-quality copy image may not be obtained. If too much silicon oil or silicone varnish is processed,
Aggregates of inorganic fine powders are easily formed, and moreover, free silicone oil or silicone varnish is formed, so that when applied to a developer, there is a problem that fluidity cannot be improved in some cases.

In the present invention, amino-modified silicone oil or amino-modified silicone varnish can be used as silicone oil or silicone varnish for hydrophobizing inorganic fine powder.

As the amino-modified silicone oil, a silicone oil having a structure represented by the following formula (I) can be used.

[0118]

[Outside 6](Where R₁, R₆Represents a hydrogen, an alkyl group, an aryl group or
Represents an alkoxy group;_TwoIs an alkylene group, phenyl
A ren group;_ThreeHas a nitrogen-containing heterocycle in its structure
R represents a compound_Four, R_FiveIs hydrogen, alkyl, ant
Represents a hydroxyl group. R _TwoMay not be required. However,
Alkyl, aryl, alkylene and phenylene groups
Amine may be contained and the chargeability is not impaired
May have a substituent such as halogen. m is 1 or more
In the above numbers, n and l are positive numbers including 0. However
n + 1 is a number of one or more genders).

The most preferred structure among the above structures is one in which the number of nitrogen atoms in the side chain containing a nitrogen atom is one or two.

Many nitrogen-containing unsaturated heterocycles have hitherto been known, and examples thereof are given below.

[0121]

[Outside 7]

Examples of the nitrogen-containing saturated heterocycle are shown below.

[0123]

[Outside 8]

The present invention is not restricted to the above compounds, but preferably has a 5-membered or 6-membered heterocyclic ring.

As the derivatives, known compounds such as a vinyl group, a mercapto group, a methacryl group, a glycidoxy group and a ureide group may be used as long as they do not impair the charge control of the hydrocarbon group, the halo group and the amino group. Can guide everything,
Their derivatives can be used.

The nitrogen equivalent of the silicone oil used in the present invention is preferably 10,000 or less, preferably 300 to 2%.
000 is preferred. Here, the nitrogen atom equivalent is a value obtained by dividing the molecular weight by the number of nitrogen atoms per molecule by the equivalent per nitrogen atom (g / eqio). These are 1
It may be used in a kind or a mixed system of two or more kinds.

As a method of treating the silicon oil, known techniques can be used. For example, a fine powder and an amino-modified silicone oil are mixed using a mixer, the amino-modified silicon oil in the fine powder is sprayed using a sprayer, or the amino-modified silicon oil in a solvent is finely powdered according to the present invention. As a silicon varnish used to obtain an amino-modified silicon varnish for processing, methyl silicon varnish,
Phenylmethyl silicon varnish can be mentioned, and methyl silicon varnish is particularly preferable.

Methyl silicon varnish is a polymer consisting of T ³¹ units, D ³¹ units and M ³¹ units represented by the following structural formula, and is a three-dimensional polymer containing a large amount of T ³¹ units.

[0129]

[Outside 9]

In order to convert the above-mentioned silicon varnish into an amino-modified silicon varnish, a part of the methyl group or phenyl group present in the above-mentioned T ³¹ unit, D ³¹ unit and M ³¹ unit is converted to a group having an amino group. What is necessary is just to substitute. Examples of the group having an amino group include those represented by the following structural formula.

[0131]

[Outside 10]

As the method of amino-modified silicon varnish treatment, the same known technique as oil treatment can be used.

The amount of the amino-modified silicone oil or amino-modified silicone varnish solid of the present invention to be treated is the same as that of the inorganic fine powder 1
3 to 50 parts by weight, more preferably 5 parts by weight, per 100 parts by weight
~ 40 parts by weight is good. If the processing amount is less than 5 parts by weight, the surface of the inorganic fine powder cannot be sufficiently coated, and the improvement in moisture resistance is small. If the processing amount is more than 40 parts by weight, aggregates of the inorganic fine powder are generated and dispersed in the toner. Addition tends to be insufficient.

The tribo value of the silica fine powder is measured by the following method. Non-resin-coated carrier iron powder having a main particle size of 0.2 g of silica fine powder and 200 to 300 mesh left overnight under an environment of 23.5 ° C. and 60% RH (for example, Nippon Iron Powder Co., Ltd.) EFV200 / 300) 9.
8 g was weighed accurately under the above-mentioned environment, and approximately 50 c. c. Mix thoroughly (hold in hand and shake up and down about 50 times for about 20 seconds) in a polyethylene jar with a volume of. Next, as shown in FIG. 3, the mixture was placed in a metal measuring container 32 having a 400-mesh screen 33 at the bottom.
5 g is put in and a metal lid 34 is formed. At this time, the weight of the entire measurement container 32 is weighed and defined as W ₁ (g). Next, in the suction device 31 (at least the portion in contact with the measurement container 32 is an insulator), the pressure of the vacuum gauge 35 is adjusted to 250 mmHg by adjusting the air volume control valve 36 by suctioning from the suction port 37. In this state, suction is sufficiently performed to remove silica by suction. The potential of the electrometer 39 at this time is set to V (volt). Where 3
Reference numeral 8 denotes a capacitor having a capacity of C (μF). The weight of the whole measurement container after suction is weighed and is defined as W ₂ (g). The triboelectric charge (μc / g) of this silica is calculated as shown below.

[0135]

[Outside 11]

As the fine silica powder used in the present invention, both dry silica (or fumed silica) produced by vapor phase oxidation of a silicon halide and wet silica produced from water glass or the like can be used. It is possible. Dry silica having few silanol groups on the surface and in the inside of the fine silicic acid powder and having no residue such as Na ₂ O, SO ₃ ²⁻ is more preferable than wet silica.

In the case of fumed silica, a composite fine powder of silica and another metal oxide can be obtained by using another metal halide such as aluminum chloride or titanium chloride together with a silicon halide in the production process. Yes, including them.

The average particle size of the particles is 0.0%.
It is preferable to be within a range of from 01 to 2μ, and it is particularly preferable to use silica fine powder having a range of from 0.02 to 0.2μ.

The degree of hydrophobicity of the inorganic fine powder in the present invention is as follows:
The value measured by the following method is used. Other measurement methods can be applied with reference to the measurement method of the present invention.

100 ml of ion-exchanged water and 0.1 g of a sample were put into a 200 ml separatory funnel of a sealed stopper type, and were rotated at 90 rpm with a shaking machine (Tabler shaker mixer T2C type).
Shake for 10 minutes. After shaking, the mixture was allowed to stand for 10 minutes, and after the inorganic powder layer and the aqueous layer were separated, the lower aqueous layer was separated for 20 minutes.
Approximately 30 ml is collected, placed in a 10 mm cell, and the transmittance is measured at a wavelength of 500 nm based on a blank ion-exchanged water containing no fine powder, and the value of the transmittance is used as the degree of hydrophobicity of the inorganic fine powder. It is.

In the present invention, the hydrophobic inorganic fine powder has a hydrophobicity of 60% or more (more preferably 90% or more). When the degree of hydrophobicity is less than 60%, it is difficult to obtain a high-quality image due to moisture adsorption of the inorganic fine powder under high humidity.

For the hydrophobizing treatment, conventionally known hydrophobizing agents and methods are used.

Other additives may be added to the developer of the present invention as long as they do not have a substantial adverse effect. For example, a fixing aid (for example, low molecular weight polyethylene or the like) and a metal oxide such as tin oxide as a conductivity-imparting agent may be added.

In producing the magnetic toner of the present invention,
A method in which the constituent materials are kneaded well by a heat kneader such as a hot roll, a kneader, or an extruder, and then obtained by mechanical pulverization and classification; a method in which the materials are dispersed in a binder resin solution and then spray-dried. Or each method can be applied, such as a polymerization toner production method in which a predetermined material is mixed with a monomer to constitute a binder resin to form an emulsified suspension, and then the monomer is polymerized to obtain a toner. .

Hereinafter, the contact charging step of the present invention applicable to the developer and the image forming method of the present invention will be specifically described.

FIG. 1 is a schematic structural view of a contact charging device showing an embodiment of the present invention. Reference numeral 1 denotes a photosensitive drum as an object to be charged, which is formed by forming an organic photoconductor (OPC) 1b as a photosensitive layer on an outer peripheral surface of a drum base 1a made of aluminum at a predetermined speed in a direction indicated by an arrow. Rotate. In this embodiment, the photosensitive drum 1 has an outer diameter of 30 mmφ. Reference numeral 2 denotes a charging roller which is a charging member brought into contact with the photosensitive drum 1 with a predetermined pressure, and is a metal core 2a.
Is provided with a conductive rubber layer 2b, and a surface layer 2c, which is a release coating, is provided on the peripheral surface. The conductive rubber layer has a thickness of 0.
It preferably has a thickness of 5 to 10 mm (preferably 1 to 5 mm). The surface layer in this embodiment is a release film, and it is preferable to provide a release film in terms of matching with the developer and the image forming method according to the present invention. However, if the resistance is too high, the photoreceptor drum 1 is not charged. If the resistance is too low, a large voltage is applied to the photoreceptor drum 1, causing damage to the drum and generation of pinholes. Resistance value (preferably, low volume efficiency of 10 ⁹ to 1
0 ¹⁴ Ωm). At this time, the thickness of the release coating is preferably within 30 μm (preferably 10 to 30 μm). The lower limit of the thickness of the releasable coating is considered to be about 5 μm if the coating is free of peeling and burrs.

In this embodiment, the outer diameter of the charging roller 2 is 12
mmφ and a conductive rubber layer 2 having a thickness of about 3.5 mm
b is an ethylene-propylene-diene terpolymer (E
For the PDM) and the surface layer 2c, a 10 μm-thick nylon-based resin (specifically, methoxymethylated nylon) was used. The hardness of the charging roller 2 is 54.5 ° (ASKER-
C). E is a power supply unit that applies a voltage to the charging roller 2 and supplies a predetermined voltage to the core 2 a (5 mm in diameter) of the charging roller 2. In FIG. 1, E indicates a DC voltage, but as shown in FIG. 4, it is preferable that an AC voltage is superimposed on a DC voltage.

In order to adjust the electric resistance value, it is preferable to disperse a conductive fine powder such as carbon in the conductive rubber layer and / or the release coating.

Preferred process conditions in this case are shown below.

Contact pressure: 5 to 500 g / cm AC voltage: 0.5 to 5 KVpp AC frequency: 50 to 3000 Hz DC voltage (absolute value): 200 to 900 V

FIG. 2 is a schematic structural view of a contact charging member showing another embodiment of the present invention. The same members as those of the apparatus shown in FIG.

The contact charging member 3 of this embodiment is in the form of a blade which is brought into contact with the photosensitive drum 1 in a forward direction at a predetermined pressure. The blade 3 is electrically conductive to the metal supporting member 3a to which a voltage is supplied. A rubber layer 3b is supported, and a surface layer 3c serving as a releasable film is provided at a contact portion with the photosensitive drum 1. Nylon having a thickness of 10 μm was used as the surface layer 3c. According to this embodiment, the same operation and effect as those of the above-described embodiment can be obtained without problems such as adhesion between the blade and the photosensitive drum.

In the above-described embodiment, a roller-shaped or blade-shaped charging member is used. However, the present invention is not limited to this, and the present invention can be applied to other shapes.

In this embodiment, the charging member is composed of the conductive rubber layer and the release film, but the invention is not limited to this. For preventing leakage to the photoreceptor between the conductive rubber layer and the surface of the release film. It is preferable to form a high resistance layer, for example, a hydrin rubber layer with small environmental fluctuation.

As the release coating, polyvinylidene fluoride (PVDF) or polyvinylidene chloride (PVDC) may be used instead of the nylon resin. As a photoreceptor, O
Amorphous silicon, selenium, Zn other than PC photoreceptor
O or the like can also be used. In particular, when amorphous silicon is used for the photoconductor, compared to the case where other materials are used, even if the softening agent of the conductive rubber layer adheres to the photoconductor even to a small extent, the image flow becomes severe, so The effect of the insulating coating is great.

In the cleaning step according to the present invention, the photosensitive drum after the transfer of the toner image is generally wiped off by a cleaning member such as a blade or a roller of a cleaner to remove the untransferred toner and other contaminants. And repeatedly subjected to image formation. As a material of the cleaning blade or the roller, polyurethane or silicone resin is preferable.

The cleaning step can be performed simultaneously in the charging step, the developing step, or the transfer step related to electrophotography.

The present invention is particularly effective for an image forming apparatus provided with a latent image carrier having an organic compound formed on the surface of the latent image carrier to be charged. When the organic compound forms the surface layer, the binder resin contained in the magnetic toner and the surface layer easily adhere to each other. Particularly, when the same material is used, toner fusion occurs at the contact point. Cheap.

The surface material of the latent image bearing member used in the present invention includes silicone resin, vinylidene chloride resin, ethylene-vinyl chloride resin, styrene-acrylonitrile resin, styrene-methyl methacrylate resin, styrene resin, polyethylene terephthalate resin, polycarbonate Resins. Without being limited to these, other monomers or copolymerization or blending between the exemplified resins can also be used.

The present invention is particularly effective for an image forming apparatus in which the diameter of the latent image carrier is 50 mm or less. This is because, in the case of a small-diameter drum, even if the linear pressure is the same, the curvature is large, so that the pressure is likely to be concentrated at the contact portion.

It is considered that the same phenomenon occurs in the belt photosensitive member, and the present invention is also effective for an image forming apparatus having a radius of curvature of 25 mm or less at the contact portion.

Further, the image forming method and apparatus of the present invention will be described with reference to FIG.

Contact charger 5 having voltage applying means 515
02, the photosensitive member surface is charged to a negative polarity, a digital latent image is formed by image scanning by exposure 505 with a laser beam, and a developing device 509 having a developing sleeve 504 including a magnetic blade 511 and a magnet is included. The latent image is reversely developed with a negatively chargeable one-component magnetic developer 510. In the developing section, between the conductive substrate of the photosensitive drum 501 and the developing sleeve 504, an alternating bias, a pulse bias and / or a DC bias are applied by a bias applying means 512. When the transfer paper P is conveyed and reaches the transfer portion, the transfer means 503 charges the transfer paper P from the rear surface (the surface opposite to the photosensitive drum side), whereby the developed image (toner image) on the photosensitive drum surface is formed. The image is electrostatically transferred onto the transfer paper P. Transfer paper P separated from photosensitive drum 501
Is subjected to a fixing process for fixing the toner image on the transfer paper P by the heating and pressing roller fixing device 507.

The one-component developer remaining on the photosensitive drum after the transfer step is removed by a cleaning device 508 having a cleaning blade. After the cleaning, the photosensitive drum 501 is gradually charged by the erase exposure 506, and again,
The process starting from the charging process by the charger 502 is repeated.

The electrostatic image carrier (photosensitive drum) has a photosensitive layer and a conductive substrate, and moves in the direction of the arrow. A non-magnetic cylindrical developing sleeve 504 serving as a toner carrier rotates in the developing section so as to advance in the same direction as the surface of the electrostatic image holding member. Inside the non-magnetic cylindrical sleeve 504, a multi-pole permanent magnet (magnet roll) as a magnetic field generating means is arranged so as not to rotate. The one-component insulating magnetic developer 510 in the developing device 509 is applied on the non-magnetic cylindrical surface,
Due to friction between the surface of the magnetic toner particles and the magnetic toner particles, the magnetic toner particles are given, for example, a negative triboelectric charge.
Further, the thickness of the developer layer is reduced (from 30 μm to 500 μm) by disposing an iron magnetic doctor blade 511 close to the cylindrical surface (interval: 50 μm to 500 μm) and opposed to one magnetic pole position of the multipole permanent magnet. (300 μm) and uniformly regulated, and a developer layer thinner than the gap between the electrostatic image holding member 501 and the toner carrier 504 in the developing section is formed so as to be in non-contact. By adjusting the rotation speed of the toner carrier 504, the surface speed of the sleeve is substantially equal to or close to the speed of the electrostatic image holding surface. The opposed magnetic poles may be formed by using permanent magnets instead of iron as the magnetic doctor blade 511. In the developing unit, an AC bias or a pulse bias may be applied between the toner carrier 504 and the electrostatic image holding surface by the bias unit 512. This AC bias has f of 200 to 4,000 Hz and Vpp of 500 to 3.0.
00V is sufficient.

At the time of transfer of the magnetic toner particles in the developing portion, the magnetic toner particles transfer to the electrostatic image side due to the electrostatic force of the electrostatic image holding surface and the action of the AC bias or the pulse bias.

Instead of the magnetic doctor blade 511,
The thickness of the developer layer may be regulated by pressing using an elastic blade made of an elastic material such as silicon rubber, and the developer may be applied on the developer carrying member.

As the electrophotographic apparatus, of the above-described components such as the photosensitive member, the developing means, and the cleaning means, a plurality of components are integrally connected as an apparatus unit, and this unit is detachably attached to the apparatus body. May be configured. For example, a unit is formed by integrally supporting at least one of the charging unit, the developing unit, and the cleaning unit together with the photoreceptor, and the unit is detachably attached to the apparatus main body. It may be configured to be detachable. At this time, the above-described device unit may be provided with a charging unit and / or a developing unit.

When the image forming apparatus of the present invention is used as a facsimile printer, the optical image exposure 505 is an exposure for printing received data. FIG. 6 is a block diagram showing an example of this case.

The controller 611 controls the image reading section 610 and the printer 619. The entire controller 611 is controlled by the CPU 617. The read data from the image reading unit is transmitted to the partner station through the transmission circuit 613. Data received from the partner station is sent to the printer 619 through the receiving circuit 612. Predetermined image data is stored in the image memory. Printer controller 6
Reference numeral 18 controls the printer 619. 614 is a telephone.

The image received from the line 615 (image information from the remote terminal connected via the line) is demodulated by the receiving circuit 612, and the CPU 617 performs a decoding process of the image information, and sequentially executes the image memory 616. Is stored in
When the image of at least one page is stored in the memory 616, the image of the page is recorded. CPU 61
Reference numeral 7 reads out one page of image information from the memory 616 and sends out the decoded one page of image information to the printer controller 618. The printer controller 618 uses C
Upon receiving the image information of one page from the PU 618, the printer 619 is controlled to record the image information of the page.

The CPU 617 receives the next page during recording by the printer 619.

As described above, image reception and recording are performed.

Hereinafter, the number of parts in the Synthesis Examples and Example 1 indicates parts by weight.

[0175]

EXAMPLES Synthesis Example 1 200 parts of cumene was placed in a reactor and heated to the reflux temperature. To this, 85 parts of a styrene monomer, 15 parts of an acrylic acid monomer, and 8 parts of di-tert-butyl peroxide.
5 parts were mixed. Furthermore, under cumene reflux (146 ° C to 15
(6 ° C.) to complete the solution polymerization, and the temperature was raised to remove cumene. The obtained styrene-acrylic acid copolymer is soluble in THF, and has a weight average molecular weight (Mw) of 3,500, a weight average molecular weight / number average molecular weight (Mw / Mn) of 2.52,
The molecular weight at which the main peak of GPC was located was 3,300, and the glass transition point (Tg) was 56 ° C.

30 parts of the above copolymer was dissolved in the following monomer mixture to obtain a mixed solution.

[0177]

[Table 1]

170 parts of water in which 0.1 part of partially saponified polyvinyl alcohol was dissolved was added to the above mixed solution to prepare a suspension dispersion. The above suspension dispersion was added to a reactor filled with 15 parts of water and purged with nitrogen, and a suspension polymerization reaction was performed at a reaction temperature of 70 to 95 ° C. for 6 hours. After the reaction is completed, the mixture is filtered, dehydrated and dried,
A copolymer composition was obtained. The composition is a styrene-acrylic acid copolymer, styrene-acrylic acid-acrylic acid n-
The butyl copolymer was uniformly mixed. The obtained resin composition was measured for the molecular weight distribution of the THF-soluble component.
In the PC chart, there are peaks at positions of about 3,500 and about 31,000, and Mn = 5,100 and Mw = 11.0.
50,000, Mw / Mn = 22.5, molecular weight 10,000 or less 27w
t%. Further, the Tg of the resin is 59 ° C.
Glass transition point T of components less than 10,000 fractionated by PC
g ₁ was 57 ° C.

The acid value of this resin composition was 22.0.

Synthesis Example 2 200 parts of cumene was charged into a reactor and heated to a reflux temperature. The following mixture was subjected to solution polymerization under cumene reflux.

[0181]

[Table 2] Cumene was removed. The obtained styrene-acrylic acid n-
Butyl copolymer has Mw = 6,900, Mw / Mn =
It had a main peak at a position of 2.36 and a molecular weight of 7,200, and had a Tg of 64 ° C.

30 parts of the above styrene-maleic acid n-butyl half ester copolymer was dissolved in the following monomer mixture to form a mixture.

[0183]

[Table 3] Styrene-n-butyl maleate half-ester copolymer and styrene-n-butyl acrylate-n-maleic acid
A resin composition of a butyl half ester copolymer was obtained.

The acid value of the resin composition was 20.6.

Synthesis Example 3 200 parts of cumene was charged into a reactor and the temperature was raised to the reflux temperature. To this, 78 parts of styrene monomer, 15 parts of n-butyl acrylate monomer, 7 parts of n-butyl maleate half ester, 0.3 parts of divinylbenzene, di-tert-
A mixture of 1.0 part of butyl peroxide was added dropwise over 4 hours under reflux of cumene, and a polymerization reaction was further performed for 4 hours. Thereafter, the solvent was removed by ordinary vacuum distillation to obtain a copolymer. The obtained copolymer had Mw = 250,000 and Mw / Mn =
11.0, Tg = 60 ° C.

The acid value of this copolymer was 19.5.

Reference Synthesis Example 1 The same procedure as in Synthesis Example 3 was carried out except that the styrene monomer was 82 parts, the n-butyl acrylate monomer was 18 parts, and the n-butyl maleate half ester was 0 part.

The acid value of this copolymer was 0.4.

Synthesis Example 4 The same procedures as in Synthesis Example 3 were carried out except that the styrene monomer was 82 parts and the n-butyl maleate half ester was 3 parts.

The acid value of the obtained copolymer was 7.3.

Synthesis Example 5 Synthesis Example 5 was carried out in the same manner as in Synthesis Example 3 except that 70 parts of a styrene monomer and 15 parts of n-butyl maleate were used.

The acid value of the obtained copolymer was 48.

Production Example 1 100 parts of resin composition of Synthesis Example 1 100 parts of magnetic fine powder (BET value of 8.6 m ² / g) 100 parts of negative charge control agent (monoazo dye-based chromium complex) 1.1 parts・ 3 parts of low molecular weight polypropylene (Mw = 6,000)

The above mixture was melt-kneaded with a twin-screw extruder heated to 140 ° C., and the cooled kneaded material was coarsely pulverized by a hammer mill, and the coarsely pulverized material was finely pulverized by a jet mill. The powder is air-classified, and the ultrafine powder and the coarse powder are simultaneously strictly classified and removed by a multi-segmentation classifier (elbow jet classifier manufactured by Nittetsu Mining Co., Ltd.) utilizing the Coanda effect, and the volume average particle size is 6.4 μm. A negatively chargeable magnetic toner (I) (Tg 57 ° C.) was obtained.

Production Example 2 100 parts of resin composition of Synthesis Example 2 110 parts of magnetic fine powder (BET value of 8.6 m ² / g) 110 parts of negative charge control agent (monoazo dye-based chromium complex) 1.1 parts・ 3 parts of low molecular weight polypropylene (Mw = 6,000)

The above mixture was treated in the same manner as in Production Example 1 to obtain negatively-chargeable magnetic toners (II) and (III) having different average particle diameters.
I got

Production Example 3 100 parts of resin composition of Synthesis Example 3 80 parts of magnetic fine powder (BET value of 8.6 m ² / g) 1.1 parts of negative charge control agent (monoazo dye-based chromium complex)・ 3 parts of low molecular weight polypropylene (Mw = 6,000)

The above mixture was used in the same manner as in Production Example 1 to obtain a negatively chargeable magnetic toner (IV).

Production Examples 4 and 5 The procedure of Production Example 1 was repeated except that the resin compositions of Synthesis Examples 4 and 5 were used instead of the resin compositions of Synthesis Example 3 to obtain negatively-chargeable magnetic toners (V) and (VI). ) Got.

Reference Production Example 1 100 parts of resin composition of Reference Example 1 90 parts of magnetic fine powder (BET value of 7.7 m ² / g) 90 parts of negative charge control agent 1.1 parts of salicylic acid chromium complex・ 3 parts of low molecular weight polypropylene (Mw = 6,000)

A negatively chargeable magnetic toner (VII) (Tg 55 ° C.) was obtained in the same manner as in Production Example 1 using the above components.

The following Table 1 shows the particle size distribution of the toner described above.

[0203]

[Table 4]

Examples 1 to 6 and Comparative Examples 1 to 3 Fine silica powder shown in Table 2 below and the above magnetic toner were mixed with a Henschel mixer to obtain a developer.

Next, each of these adjusted magnetic developers was applied to an image forming apparatus (Canon LB) having a contact charging device and a polyurethane cleaning blade shown in FIG.
P-8II remodeling machine), a DC voltage (-700 V) and an AC voltage (300 Hz, 1500 Vpp) are applied and a toner image is continuously formed at a printing speed of 8 sheets (A4) / min by a reversal developing method. Test at room temperature and humidity (25 ° C,
The test was performed at 60% RH, high temperature and high humidity (30 ° C., 90% RH) and low temperature and low humidity (15 ° C., 10% RH), and the printout image was evaluated. At the same time, the appearance of the charging member (roller type) and the surface of the laminated OPC photosensitive drum were observed.

The photoreceptor used had a surface abrasion characteristic of 2.5 × 10 ^-2 cm ³ by the Taber abrasion tester.

As described above, the charging roller 2 has a diameter of 12 m.
m, the core metal has a diameter of 5 mm, and the conductive rubber layer 2b
Has a thickness of about 3.5 mm, the release coating formed of methoxymethylated nylon has a thickness of 20 μm, and is pressed against the OPC photoreceptor at a total pressure of 1.2 kg (linear pressure 55 g / cm). did.

FIG. 5 is a schematic diagram of the image forming apparatus. In the image forming apparatus, the toner layer thickness on the sleeve is set to 13
0 μm, the closest gap between the sleeve and the OPC photoconductor is 30
The image forming test was performed while applying a DC bias (−500 V) and an AC bias (1800 Hz, 1600 Vpp) to the developing sleeve.

Table 2 shows the physical properties of the hydrophobic silica.
Table shows the physical properties of the developer, and Table 4 shows the composition of the developer and the evaluation results. The roller type of FIG. 1 was used except that the blade type charging device of FIG. 2 was used in Example 4.

The evaluation criteria are shown below.

Photoreceptor fusion (photoreceptor surface after 6000 sheets of image output) ○: No fusion at all ○ △: White spots due to fusion of 1 to 3 points of toner in A4 solid black △: A4 solid White spots due to fusion of 3 to 10 points of toner in black ×× Reproducibility of 100 white dots due to fusion of 10 or more points of toner in A4 solid black (x shown in FIG. 5
(Reproducibility of 0 μm checker pattern image) ○: 2 or less defects ○ △: 3 to 5 defects △: 6 to 10 defects ×: 11 or more defects

[0212]

[Table 5]

[0213]

[Table 6]

[0214]

[Table 7]

[0215]

As described above, in the step of charging the latent image holding member by contacting the same, the developer according to the present invention employs the above-described configuration to prevent the cleaning step from being performed. As a result, even when a small amount of the residual developer is present on the photosensitive drum, sticking to the surface of the charging member and the surface of the photosensitive drum and generation of scratches are extremely unlikely to occur.

As described above, the developer according to the present invention has extremely good matching of the charging step according to the present invention.
It was possible to provide an image method in which the ability of the charging step according to the present invention was sufficiently exhibited and a good image was always formed.

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing a contact charging roller used in an image forming apparatus of the present invention.

FIG. 2 is an explanatory view schematically showing a contact charging blade which is another embodiment of the contact charging means.

FIG. 3 is an explanatory diagram of a measuring device used for obtaining a charge amount.

FIG. 4 is an explanatory view schematically showing a contact charging roller used in the image forming apparatus of the present invention.

FIG. 5 is a schematic view showing a specific example of the image forming apparatus of the present invention.

FIG. 6 is a block diagram illustrating a specific example of a facsimile apparatus.

FIG. 7 is a diagram showing a checker pattern used to determine the reproducibility of minute dots.

[Explanation of symbols]

 1 photosensitive drum 2, 3 contact charging member E power supply

Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI G03G 9/083 G03G 9/08 101 15/08 507 15/08 507L (72) Inventor Tetsuto Kuwashima 3-30-2 Shimomaruko, Ota-ku, Tokyo Within Canon Inc. (72) Inventor ▲ Takeguchi Go Tsuyoshi 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Koichi Tomiyama 3-30-2 Shimomaruko, Ota-ku, Tokyo Within Non Co., Ltd. (72) Motoki Hisagi, Inventor 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroshi Yuza 3-30-2, Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Eiichi Imai 3-30-2 Shimomaruko, Ota-ku, Tokyo Within Canon Inc. (56) References JP-A-1-112253 (JP, A) JP-A-1-221755 (JP, A JP-A-64-7086 (JP, A) JP-A-1-154175 (JP, A) JP-A-63-208880 (JP, A) JP-A-63-139369 JP, A) JP-A-63-139367 (JP, A) JP-A-63-139371 (JP, A) JP-A-64-73367 (JP, A) JP-A-61-173275 (JP, A) (58) ) Surveyed field (Int.Cl. ⁷ , DB name) G03G 9/08 G03G 5/00

Claims (18)

(57) [Claims] A charging step of contacting a charging member to which a charging bias voltage of contact charging means is applied with a charging member at a contact pressure of 5 to 500 g / cm to charge the charging member;
An exposure step of exposing the charged object to form an electrostatic image on the surface of the object; and a developing step of developing the electrostatic image carried on the object by developing means. An image forming method, wherein the charging bias is at least -200 to -900.
V DC voltage is applied and the developing means has a developer having a negatively-chargeable magnetic toner containing at least a binder and a magnetic substance as a colorant and a hydrophobic inorganic fine powder. cage, the negatively chargeable magnetic toner has a volume average particle diameter of 4-8μm, 17-60% by number or less of the magnetic toner particles with particle sizes of 5 [mu] m, the magnetic toner particles having a particle diameter 6.35-10.08Myuemu 5-5
It has a particle size distribution containing 0% by number and 2.0% by volume or less of magnetic toner particles having a particle diameter of 12.7 μ or more. The hydrophobic inorganic fine powder is at least treated with silicone oil or silicone varnish. The developer has a BET specific surface area of 1.8 to 3.5 m ² / g.
And a loose apparent density of 0.4 to 0.52 g / cm ³
Wherein the true density is 1.45 to 1.8 g / cm ³ . Wherein said negatively chargeable magnetic toner, the content of the following formulas N / V = -0.05N + k (wherein a particle size of 5μm or less of magnetic toner particles, N is the following magnetic toner particles with particle sizes of 5μm % Represents the content number, V represents the content volume% of the magnetic toner particles having a particle size of 5 μm or less, k represents a positive number of 4.6 to 6.2, and N represents
Represents a positive number of 17-60. 2. The image forming method according to claim 1, wherein the particle size distribution satisfies the following: 3. The image forming method according to claim 1, wherein the hydrophobic inorganic fine powder is treated with a silicone oil or silicone varnish after being treated with a silane coupling agent. 4. The hydrophobic inorganic fine powder has a hydrophobicity of 60.
The image forming method according to claim 1, wherein the ratio is not less than%. 5. The apparatus according to claim 1, wherein the member to be charged has a photosensitive layer formed of an organic photoconductor.
5. The image forming method according to any one of claims 1 to 4. 6. The image forming method according to claim 1, wherein the member to be charged has a radius of curvature of 25 mm or less at a contact portion with the charging member. 7. The image forming method according to claim 1, wherein the member to be charged is a photosensitive drum having a diameter of 50 mm or less. 8. A developing means includes: a developer; a developer carrier for carrying the developer and transporting the developer to a developing section; and a layer of the developer carried and transported by the developer carrier. A developer layer thickness regulating member for regulating the thickness, wherein the layer thickness of the developer carried on the developer carrier is such that the charged member and the developer carrier in the developing section are The image forming method according to any one of claims 1 to 7, wherein the gap is set to be smaller than the gap, and a developing bias voltage is applied to the developer carrier when the electrostatic charge image is developed. 9. The image forming method according to claim 8, wherein the developing bias voltage has an AC bias voltage or a pulse bias voltage. 10. A charging member to which a charging bias voltage of a contact charging unit is applied to a member to be charged is 5 to 500 g / cm.
A charging step of charging the member to be charged by contacting with the contact pressure of: a light exposure step of exposing the charged member to form an electrostatic image on the surface of the member; A developing step of developing the charged electrostatic image with a developer of the developing unit. The developing bias for image formation used in the image forming method, wherein the charging bias is at least −200 to −−. 900
V DC voltage is applied, and the developer is a negative band containing at least a magnetic material as a binder resin and a colorant.
Has a conductive magnetic toner and hydrophobic inorganic fine powder, the negatively chargeable magnetic toner has a volume average particle size 4-8Myuemu, the following magnetic toner particles with particle sizes of 5 [mu] m 17-60% by number, particle size 6.35-10.08 μm magnetic toner particles in 5-5
It has a particle size distribution containing 0% by volume and 2.0% by volume or less of magnetic toner particles having a particle size of 12.7 μ or more. The hydrophobic inorganic fine powder is at least treated with silicone oil or silicone varnish. The developer has a BET specific surface area of 1.8 to 3.5 m ² / g.
And a loose apparent density of 0.4 to 0.52 g / cm ³
And a true density of 1.45 to 1.8 g / cm ³ . 11. The negatively chargeable magnetic toner has a particle size 5μm
The content of the following magnetic toner particles is represented by the following formula: N / V = −0.05N + k (where N represents the content number% of the magnetic toner particles having a particle size of 5 μm or less, and V is the magnetic toner particles having a particle size of 5 μm or less. , K represents a positive number of 4.6 to 6.2;
Represents a positive number of 17-60. The image forming developer according to claim 10, having a particle size distribution satisfying the following: 12. The method according to claim 10, wherein the hydrophobic inorganic fine powder is treated with a silicone oil or silicone varnish after being treated with a silane coupling agent.
Or the image forming developer according to item 11. 13. The hydrophobic inorganic fine powder has a degree of hydrophobicity of 6
The image forming developer according to claim 10, wherein the content is 0% or more. 14. The image forming developer according to claim 10, wherein the member to be charged has a photosensitive layer formed of an organic photoconductor. 15. The image forming developer according to claim 10, wherein the charged member has a radius of curvature of a contact portion with the charging member of 25 mm or less. 16. The object to be charged is a photosensitive drum having a diameter of 50 mm or less.
The image forming developer according to any one of the above. 17. A developing means comprising: a developer; a developer carrier for carrying the developer and transporting the developer to a developing section; and a layer of the developer carried and transported by the developer carrier. A developer layer thickness regulating member for regulating the thickness, wherein the layer thickness of the developer carried on the developer carrier is such that the charged member and the developer carrier in the developing section are 17. The image forming developing device according to claim 10, wherein a developing bias voltage is applied to the developer carrier when the electrostatic charge image is developed. Agent. 18. The image forming developer according to claim 17, wherein the developing bias voltage has an AC bias voltage or a pulse bias voltage.