KR950014872B1 - Image forming method - Google Patents

Abstract

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Description

Image Formation Method

1 is a schematic illustration of an image forming apparatus to which the magnetic toner of the present invention can be preferably applied.

FIG. 2 is an enlarged view of a developing portion of the image forming apparatus shown in FIG.

* Explanation of symbols for main parts of the drawings

1: Photosensitive drum 2: Primary charger

3: Warrior charging 4: Developing sleeve

7: pressure fixing roller 9: developer

11: Magnetic Doctor Blade

The present invention is contained in a developer for developing an electrostatic charge image for developing an electrostatic latent image in an image forming method using electrophotographic, electrostatic recording, electrostatic printing, and the like, and at least magnetic resin particles and surface modified silica fine particles. The present invention relates to an image forming method using a magnetic toner having a surface-modified fine silica powder. More specifically, the present invention relates to an image forming method for use in a magnetic toner suitable for high-speed image formation using an amorphous silicon drum as a full charge image carrier.

Conventionally, as an image forming method for performing electrophotographic, a photosensitive drum is used as a charge-charge image carrier, and the photosensitive drum surface is uniformly charged by a charging means such as a corona battery, and then image is exposed to the surface of the photosensitive drum. A toner image is formed on the surface of the photosensitive drum by forming a latent electrostatic image on the surface and developing the electrostatic latent image by a developing method such as a jumping development method or a magnetic brush method using a developer having a magnetic toner. Then, a method of transferring a toner image onto a recording medium and mounting it thereon is known as a general method.

A developer used to develop an electrostatic latent image on the surface of a photosensitive member, comprising a two-component developer in which a magnetic carrier such as iron powder or ferrite powder, and a toner having a resin and a colorant are mixed, and a one-component system that does not use a carrier. Developers are known.

In the developing method using the two-component developer, the toner image quality is largely influenced by the mixing ratio of the toner and the carrier, that is, the toner concentration of the two-component developer, so that the toner concentration in the developer is always controlled. There was a problem to be done.

On the other hand, the development using a one-component developer using a magnetic toner mainly composed of a resin and a magnetic powder does not require an apparatus for maintaining a constant toner concentration as compared to the two-component developing method, and is easy to process, and a developing device. There is an advantage that the size can be reduced.

In a system using a one-component developer having a magnetic toner, a phenomenon in which the magnetic toner agglomerates gradually appears as the charge amount of the magnetic toner gradually increases, so that a thin layer is coated on the sleeve which is the developer carrier. I tend to coat very thickly on the sleeve, causing background fogging. In particular, such a problem tends to occur in a high-speed copying machine which copies more than 50 copies per minute.

In order to solve such a problem, Japanese Unexamined Patent Publication No. 55-120041 discloses a method in which an insulating magnetic toner contains a silicon dioxide fine particle having a pH of 7 or more having a trimethylsiloxane group, that is, a hydrophobic silica fine powder. The addition of hydrophobic silica fine powder tends to control the increase in the charge amount of the insulating magnetic toner. However, in the high-speed copying machine, the charge amount increases in an environment with low humidity, which sometimes causes problems such as deterioration of image density and background blurring. Cause

The silica fine powder subjected to the hydrophobization treatment tends to form aggregates during the hydrophobization treatment, and at that time, aggregates of several hundred μm may be formed. Such aggregates inhibit the chargeability of the toner and cause a decrease in the charge amount of the toner. In addition, such large diameter aggregates have a very small specific surface area (m 2 / g), and the interaction with the toner particles is remarkably weak, so that the aggregates are easily separated from the toner particles and the aggregates are scattered alone in the developer. do.

Since the scattered silica agglomerate has a small specific gravity, it scatters in the copier in accordance with the airflow in the copier, and reaches the discharge wire used for corona charging to contaminate the wire of the charger. The contaminated portion has a weak corona discharge, resulting in an uneven distribution of the charge of the corona charger, and thus the resulting image has an uneven density. Wire contamination by silica has no specific problem with the one-component developer, but has a problem that can be caused by the two-component developer. Japanese Unexamined Patent Publication No. 60-107036 discloses a method for improving the discharge wire contamination by silica fine powder, wherein the volume density of silica fine powder is controlled to 30 g / l or less, and a smaller amount of silica fine powder is added to the developer. In this regard, a method for alleviating the harmful effects caused when a large amount is added is disclosed. However, this method is effective in mitigating the harmful effects, but the problem of contamination of the wire by the addition of silica fine powder still exists, resulting in contamination of the discharge wire after tens of thousands of repeated copies.

In particular, amorphous silicon, which has excellent durability as a photosensitive member, is excellent as a photosensitive drum used in high-speed copying machines, but in order to maintain the surface potential of dark areas, a large amount of corona moth current of more than 500 mA is required than other types of photosensitive members. The contamination of the discharge wire by the fine silica powder is more likely to occur.

As described above, there has been a demand for an image forming method using a magnetic toner that can be used in a developer for a high speed copying machine and which has excellent silica fine powder.

An object of the present invention is to provide a magnetic toner that solves the problems included in the prior art.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming method using a magnetic toner which has a stable charge amount and which contains surface-modified silica fine powder which does not cause harmful effects such as contamination of discharge wires generated by traveling on a plurality of radiant sheets. There is.

In order to achieve the above object, the present invention, the process of charging the amorphous silicon drum by the corona charging, the process of exposing the amorphous silicon drum to form an electrostatic latent image on the amorphous silicon drum, and the magnetic toner is a binder It comprises a resin resin, a charge control agent and a magnetic resin particles containing at least a magnetic powder and a surface-modified silica fine powder, wherein the surface-modified silica fine powder is a silica fine powder treated with a hydrophobic treatment agent, the silica fine powder, 180 The electrostatic latent image is developed by the magnetic toner supported on a developing sleeve to have a specific surface area of m 2 / g or more, a hydrophobic ratio of 60 to 95% and a volume density of 35 to 49 g / l, and to form a magnetic toner image. Transferring the magnetic toner phase onto an amorphous silicon drum with a transfer material; transferring the magnetic toner phase onto an amorphous silicon drum And the step of transferring to, and provides an image forming method, characterized in that, including a step of fixing a magnetic toner image formed on the transfer reigning.

The present inventors have carefully studied that a specific amount of hydrophobic treatment agent, especially hexamethyldi, is contained in a magnetic toner together with magnetic resin particles and has a specific specific surface area and volume density in a surface modified silica micropowder. When treated with silazane, it is firmly fixed without being decomposed by the decomposition process or the external addition process, thereby obtaining a magnetic toner having a surface-modified silica fine powder having specific properties that do not contain aggregates that cause contamination of the discharge wire. I found that.

In the present invention, the specific surface area of the silica fine powder initiator used in the production of the surface modified silica fine powder needs to be 300 m 2 / g or more, whereby the fine particles of the silica fine powder are treated at the time of treatment with the hydrophobing agent. A surface-modified silica fine powder having a specific surface area of 180 m 2 / g or more capable of preventing generation of aggregates can be obtained. The specific surface area of the silica fine powder initiator is preferably 350 to 500 m 2 / g, whereby the surface-modified silica fine particles having a specific surface area of 200 to 320 m 2 / g which can further improve the fluidity and durability of the developer. Powder can be obtained. When the specific surface area of the said silica fine powder initiator is smaller than 300 m <2> / g, aggregates generate | occur | produce easily at the time of the process by a hydrophobization agent, and it is difficult to make the specific surface area of the surface modified silica fine powder obtained below 180 m <2> / g.

According to the present invention, the specific surface area of the fine powder is a value calculated by the following method.

[Specific surface area]

According to the BET method, nitrogen gas is adsorbed on the surface of the sample, the amount of adsorption is determined based on the pressure difference indicated by the manometer, and the specific surface area is calculated.

In the present invention, the volume density of the initiator of the silica fine powder used in the production of the surface-modified silica fine powder is preferably 40 g / l or less, whereby aggregates are less likely to occur in the initiator of the silica fine powder. The formation of aggregates can also be suppressed even during treatment with a hydrophobizing agent, so that the volume density of the resulting surface-modified silica fine powder can be set to 35 to 49 g / l. When the volume density of the silica fine powder initiator exceeds 40 g / L, aggregates tend to form in the initiator of the silica fine powder, and when the silica fine powder initiator containing such aggregates is treated, it is not decomposed during the treatment of the aggregates in the initiator. Therefore, it remains as it is and becomes a cause of contamination of discharge wire. For handling, it is preferable to use a silica fine powder initiator with a specific surface area of 20 g / l or more.

The volume density of the fine powder according to the present invention is a value obtained by the following method.

[Volume density]

To a 100 ml measuring cylinder, a sample on paper is slowly added to make 100 ml. In this case, do not tap the paper. Find the difference between before and after adding the sample and calculate the volume density according to the following equation.

Volume density (g / ℓ) = sample weight (g) x 10

By treating the silica fine powder with 15 to 25 parts by weight of hexamethyldisilazane based on 100 parts by weight of the silica fine powder initiator, a surface-modified silica fine powder having almost no aggregates and having the properties required by the present invention is obtained. When hexamethyldisinelazan is used in an amount of 15 parts by weight or less, the surface modification of the silica fine powder is insufficient, so that the charge amount of the toner is lowered in a high humidity environment, and the concentration is easily caused. On the other hand, when the amount of hexamethyldisilazane added is more than 25 parts by weight, hexamethyldisilazane becomes excessive with respect to the silica fine powder to form aggregates, resulting in contamination of the discharge wire. In addition, when the hexamethyldisilazane is more than 25 parts by weight, the specific surface area of the surface-modified silica fine powder is smaller than 180 m 2 / g, so that the fluidity required as a toner for high-speed copying machines cannot be maintained while driving, resulting in background blurring. This occurs, and the reproducibility of the line image tends to be lowered, and in particular, scattering of the toner occurs.

Since the reaction of the hexamethyldisilazane with the silanol groups present on the surface of the silica fine powder is promoted by the moisture contained in the initiator of the silica fine powder, the present inventors have a small amount of the surface-modified silica fine powder by the moisture content. It was found that the rate (degree of hydrophobizing the powder) can be controlled.

The silica fine powder initiator can control the hydrophobicity of the surface-modified silica fine powder obtained by treating with hexamethyldisilazane in the range of 60 to 95% by setting the water content to 0.5 to 5% by weight, more preferably. By setting the water content to 0.7 to 3% by weight, the hydrophobization rate of the surface-modified silica fine powder can be made within the range of 70 to 90%, and more excellent developability and durability can be obtained.

When the moisture content of the silica fine powder initiator is less than 0.5% by weight, the reaction between hexamethyldisilazane and silanol groups on the surface of the silica fine powder is insufficient, resulting in a hydrophobic ratio of the surface-modified silica fine powder being 60% or less. On the other hand, when the moisture content of the initiator of the silica fine powder is more than 5% by weight, the surface modification of the silica fine powder by hexamethyldisilazane is excessive, so that the hydrophobic ratio of the surface modified silica fine powder becomes 95% or more. The tendency is high.

The hydrophobic ratio of the surface-modified silica fine powder according to the present invention is a value obtained by the following method.

[Small yield test]

Take 1 g of the sample in a separatory funnel, add 100 ml of pure water, and shake it for 10 minutes with a tumbler mixer. After shaking, place the separatory funnel on a stand and stop for 10 minutes. Thereafter, 20 to 30 ml of the lower layer mixed solution is collected in a separatory funnel, the collected lower layer mixed solution is separated into a 10 mm quartz cell, placed in a colorimetric system using pure water as a blank, and the transmittance is made hydrophobic.

Physical properties of the surface-modified silica micropowder of the present invention prepared by the silica micropowder initiator are as follows.

Since the surface-modified silica fine powder according to the present invention has a specific surface area of 180 m 2 / g or more, when the surface-modified silica fine powder is mixed with a magnetic toner, the fluidity of the developer for a high-speed copying machine may be run against a plurality of radiant sheets. It is possible to obtain a developer which can be kept in an excellent state and has a low background flow and excellent reproducibility of line images. In view of stable fluidity, the surface-modified silica fine powder preferably has a specific surface area of 200 to 320 m 2 / g.

Since the surface-modified silica fine powder of the present invention has a bulk density of 35 to 49 g / L, the surface modified silica fine powder exhibits excellent performance against contamination of the discharge wire. When the volume density of the surface-modified silica fine powder is 35 g / l or less, when the magnetic toner is added in an amount sufficient to satisfy the development characteristics and durability, the flow of the magnetic toner becomes excessively high, and the magnetic toner is further scattered. It is easy to cause contamination of the discharge wire, and also to contaminate the transmission part of the transfer member, and to cause image contamination. When the volume density of the surface-modified silica fine powder exceeds 49 g / l, a large number of aggregates exist in the surface-modified silica fine powder obtained, resulting in contamination of the discharge wire, and also caused by the aggregates present in the surface-modified silica fine powder. As a result, the charging characteristics of the magnetic toner are suppressed, resulting in a decrease in image density.

In particular, when the bulk density of the surface-modified silica fine powder is in the range of 38 to 45 g / L, a magnetic toner having particularly excellent performance can be obtained.

Since the surface-modified silica fine powder has a hydrophobic ratio of 60 to 95%, a developer having excellent durability can be obtained, and it is preferable to have a hydrophobic ratio of 70 to 90%, whereby development characteristics and durability are improved. Excellent developer can be obtained.

When the hydrophobic ratio of the surface-modified silica fine powder is 60% or less, the chargeability tends to decrease in an environment with high humidity, and the image density is reduced, and when the hydrophobic ratio exceeds 95%, when running on a large number of radiant sheets. In particular, when driving on a large number of radiant sheets under low humidity, the charge amount of the surface-modified silica fine powder increases, causing background flow or black spots around the background flow or line image, and further, the increase in charge Decrease the concentration.

Hereinafter, the manufacturing method of the surface modified silica fine powder of this invention is demonstrated.

A predetermined amount of hexamethyldisilazane was stirred while rapidly stirring an initiator of a silica fine powder having a specific surface area of 300 m 2 / g or more, a water content of 0.5 to 5% by weight and a volume density of 40 g / l or less at high speed. 15-25 parts by weight) to 100 parts by weight of the initiator) is added dropwise or sufficiently mixed under spraying. Here, hexamethyldisilazane can be treated by diluting with a solvent such as alcohol. The initiator of the silica fine powder containing the mixed-dispersing treatment agent forms a powder liquid, and the powder liquid is heated to a boiling point temperature of hexamethyldisilazane in a nitrogen atmosphere and refluxed with stirring for 0.5 to 5 hours. Thereafter, excess treatment agent or the like may be removed as necessary. After completion of the treatment, the surface-modified silica fine powder of the present invention can be obtained by cooling to room temperature.

As the method for treating the surface-modified silica fine powder according to the present invention, a batch type treatment method in which the treatment of the initiator of the silica fine powder with hexamethyldisilazane is performed while stirring in a batch mixer is preferable. The surface-modified silica fine powder obtained by the treatment method is uniformly treated to obtain a product which is stable in quality and reproducible.

As another method, there is a continuous treatment method in which the hexamethyldisilazane is applied to the initiator of the silica fine powder dispersed in the air stream, but in the continuous treatment method, it is necessary to treat the initiator of the silica fine powder uniformly and appropriately. Therefore, the surface-modified silica fine powders obtained are poor in uniformity, poor in reproducibility, and often change over time because they cannot be sufficiently processed. Therefore, this method is not desirable.

As a method for producing an initiator of a silica fine powder having a volume density of 40 g / l or less, for example, it may be carried out by a method of milling a commercially available silica powder having a bulk density of about 70 g / l. The method may also be used and an initiator of the silica fine powder may be prepared by any method as long as the silica fine powder has a volume density of 40 g / L or less.

As a method for producing an initiator of a silica fine powder having a water content of 0.5 to 5%, for example, a commercially available initiator of a silica fine powder having a water content of about 0.5 to 5% may be performed by a method such as humidification or drying. However, of course, other methods can be used, and as long as the silica fine powder having a water content of 0.5 to 5% by weight, the initiator of the silica fine powder can be produced by any method.

As described above, in the case where the magnetic toner is prepared by adding the surface modified silica fine powder of the present invention to the magnetic resin particles containing the binder resin, the charge control agent and the magnetic powder, aggregates do not form on the surface modified silica fine powder. Or small amount and moderate hydrophobicity, the interaction between the surface-modified silica fine powder and the magnetic resin particles is strong, the glass is suppressed in the magnetic resin particles of the surface-modified silica fine powder, Prevention of contamination can be remarkably improved, and image reproducibility such as image density during driving and in various environments can also be improved.

The surface-modified silica fine powder should be added at 0.05 to 5% by weight, preferably 0.1 to 4% by weight based on the magnetic toner.

Hereinafter, the magnetic resin particles according to the present invention will be described.

As a binder resin contained in the magnetic resin particles, a single copolymer of styrene or its substituents such as polystyrene, poly-p-chlorostyrene, polyvinyl toluene, styrene / p-chlorostyrene copolymer, styrene / propylene copolymer, styrene / Vinyl toluene copolymer, styrene / vinyl naphthalene copolymer, styrene / methyl acrylate copolymer, styrene / ethyl acrylate copolymer, styrene / butyl acrylate copolymer, styrene / octyl acrylate copolymer, styrene / methyl meta Acrylate copolymer, styrene / ethyl methacrylate copolymer, styrene / butamethacrylate copolymer, styrene / methyl α-chloromethacrylate copolymer, styrene / acrylonitrile copolymer, styrene / methylvinyl ether copolymer , Styrene / ethyl vinyl ether copolymer, styrene / methyl vinyl ketone copolymer, styrene / butadiene copolymer, styrene / die Styrene copolymers, such as a styrene copolymer and a styrene / acrylonitrile / indene copolymer, polyvinyl chlorite, polyvinylacetate, polyethylene, a polypropylene, a silicone resin, a polyester resin, an epoxy resin, polyvinyl butyral, Rosin, modified rosin, terpene resin, phenolic alcohol, xylene resin, aliphatic or cycloaliphatic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, and paraffin wax, which may be used alone or in a mixture.

Among these resins, in the present invention, a styrene-acrylic copolymer is preferably used, and among the styrene-acrylic copolymers, a copolymer containing a vinyl monomer containing a carboxyl group is particularly preferable.

As a vinylic monomer containing a carboxyl group, For example, unsaturated dibasic acids, such as maleic acid, a citric acid, itaconic acid, an alkenyl succinic acid, a fumaric acid, a mesaconic acid, maleic anhydride, a citric anhydride, an itaconic anhydride, an al, Unsaturated dibasic acid anhydrides such as kenyl succinic anhydride, methyl maleic acid maleic acid ester, ethyl maleic acid maleic acid ester, butyl maleic acid maleic acid ester, methyl citraconic acid half ester, ethyl citraconic acid half ester, butyl citraconic acid half ester, and itaconic acid Half esters of unsaturated dibasic acids such as methyl half ester, methyl alkenyl succinate methyl half ester, methyl fumarate half ester, methyl mesaconic acid half ester, and unsaturated dibasic esters such as dimethyl maleate and dimethyl fumanate. In addition, α, β-unsaturated such as acrylic acid, methacrylic acid, croronic acid, cinnamic acid (Alpha), (beta)-unsaturated acid anhydrides, such as croronic anhydride and cinnamic anhydride, the anhydrides of the said (alpha), (beta)-unsaturated acid and lower fatty acid, alkenyl malonic acid, alkenyl glutaric acid, alkenyl adipic acid, these Anhydrides and monoesters.

Of these, monomers having a maleic acid structure, a fumaric acid structure or a succinic acid structure are particularly preferable.

As the charge control agent contained in the magnetic resin particles according to the present invention, for example, an organometallic complex or a chelating compound is effective, and a monoazo metal complex, an acetylacetone metal complex, an aromatic hydroxycarboxylic acid or an aromatic dicarboxyl is used. There are acid metal complexes and phenol derivatives such as aromatic hydroxycarboxylic acids, aromatic mono or polycarboxylic acids and metal salts, anhydrides, esters and bisphenols.

Among them, charge control agents such as azo metal complexes represented by the following general formula (I) and basic organic acid metal complexes represented by general formula (II) are preferable.

[Ⅰ]

[Azo Metal Complexes]

(In the above formula, M represents a coordination center metal, and M having a coordination number of 6 includes Sc, Ti, V, Cr, Co, Ni, Mn, or Fe. Ar represents a waste-niyl group or a naphthyl group. Examples of the substituent in this case include a nitro group, a halogen group, a carboxyl group, an anilide group, an alkyl group having 1 to 18 carbon atoms, or an alkoxy group. -S-, -O-, -CO-, -NH- or -NR- (R is an alkyl group having 1 to 4 carbon atoms). Represents hydrogen ions, sodium ions, potassium ions, ammonium ions or organoammonium ions)

[II]

[Basic Organic Acid Complexes]

[In the above formula, M represents a coordination center metal and M having a coordination number of 6 includes Sc, Ti, V, Cr, Co, Ni, Mn, or Fe. A is (It may have substituents, such as an alkyl group).

(X represents a substituent such as a hydrogen atom, a halogen atom, a nitro group, an alkyl group) and

(R represents a hydrogen atom, an alkyl group of C ₁ -C ₁₈ or an alkenyl group). Represents hydrogen ions, sodium ions, potassium ions, ammonium ions or organoammonium ions, and Z represents -O- or Is displayed.)

Examples of the specific compound of the azo metal complex represented by the general formula (I) are shown below.

Complex (Ⅰ) -1

Complex (Ⅰ) -2

Complex (Ⅰ) -3

Complex (Ⅰ) -4

Complex (Ⅰ) -5

Complex (Ⅰ) -6

The specific compound of the basic organic acid metal complex represented by general formula (II) below is shown.

Complex (Ⅱ) -1

Complex (Ⅱ) -2

Complex (Ⅱ) -3

Complex (Ⅱ) -4

Complex (Ⅱ) -5

Complex (Ⅱ) -6

Complex (Ⅱ) -7

Complex (Ⅱ) -8

Complex (Ⅱ) -9

Complex (Ⅱ) -10

These charge control agents can be used individually or in combination of 2 or more types.

The amount of the charge controlling agent added to the magnetic resin particles varies depending on the kind of the binder resin of the magnetic resin particles, the kind of the magnetic component or the content ratio thereof, but is preferably in the range of 0.1 to 10% by weight relative to the binder resin.

Examples of the magnetic powder contained in the magnetic resin particles according to the present invention include iron oxides such as magnetite, hemarite, and ferrite, metals such as iron, cobalt, and nickel, or metals such as aluminum, cobalt, copper, lead, magnesium, tin, and zinc. And ferromagnetic materials such as alloys of metals such as antimony, beryllium, bismur, cadmium, calcium, manganese, selenium, titanium, tungsten and vanadium, and mixtures thereof.

It is preferable that these ferromagnetic bodies are 0.05-2 micrometers, and it is more preferable that they are 0.1-0.5 micrometer.

The amount contained in the magnetic resin particles is preferably about 20 to 200 parts by weight based on 100 parts by weight of the resin component containing the binder resin, and more preferably 40 to 150 parts by weight based on 100 parts by weight of the resin component containing the binder resin. Do.

The magnetic properties upon application of 10 kDe are preferably a coercive force of 20 to 15 ersted (De), a saturation magnetization of 50 to 200 emu / g, and a residual magnetization of 2 to 20 emu / g.

To improve the releasability at the time of thermal fixing, the waxy materials such as low molecular weight polyethylene, low molecular weight, polypropylene, microcrystalline wax, garnauba wax, solazole wax or paraffin wax with respect to 100 parts by weight of the binder resin It is preferable to add 0.5-10 weight part to magnetic resin particle.

Other additives may be added to the magnetic toner of the present invention as needed.

Other additives include, for example, lubricants such as teflon, zinc stearate, and polyvinylidene fluoride (particularly, polyvinylidene fluoride is preferred), and abrasives such as cerium oxide, silicon carbide, and strontium titanate ( In particular, strontium titanate is preferred), fluidity imparting agents such as titanium oxide and aluminum oxide (particularly preferably hydrophobic), anti-caking agents, carbon black, zinc oxide, antimony oxide, tin oxide, and the like. Conductive imparting agents may be enumerated. In addition, a small amount of white fine particles or black fine particles of opposite polarity to the toner particles may be used as the developing agent.

Referring to FIGS. 1 and 2, an image forming method to which the magnetic toner of the present invention can be preferably applied will be described.

The surface of the photosensitive drum 1, such as an amorphous silicon drum, is charged with positive polarity by a primary charger 2, such as a corona discharger, a peak latent image is formed by the exposure 5, and the magnet 14 is provided. The latent image is developed by the one-component magnetic developer 10 containing the magnetic toner contained in the developing device 9 composed of the developing sleeve 4 and the magnetic blade 11. In the developing section, a bias such as an alternating current bias, a pulse bias or a direct current bias is applied by the bias applying means 12 between the conductive gas 16 of the photosensitive drum 1 and the developing sleeve 4. When the transfer sheet P is conveyed and transferred to the transfer unit, the negative charge toner image is formed on the surface of the photosensitive drum 1 by charging positively on the rear surface (opposite side of the photosensitive drum axis) of the transfer sheet P by the transfer charger 3. The transfer paper P is electrostatically transferred. The transfer paper P separated from the photosensitive drum 1 is fixed with the toner image on the transfer paper P by the heat press roller fixing unit 7. In the case of the amorphous silicon drum, the current value flowing through the primary charger 2 is preferably set to 600 to 2,000 mA, more preferably 700 to 1500 mA.

The one-component developer remaining in the photosensitive drum after the transfer process is removed by the operation of the cleaning machine 8 having the cleaning blade. The remaining charge of the photosensitive drum 1 after cleaning is removed by the erase exposure 6, and thus the process of restarting the charging process by the primary charger 2 is repeated.

The photosensitive drum 1 includes a photosensitive layer 15 and a conductive gas 16, and rotates in the direction of the arrow. The developing sleeve 4 of the nonmagnetic cylinder, which is the developer carrying member, rotates in the developing section in the same direction as the surface of the electrostatic image bearing member. Inside the developing sleeve 4, the multipolar permanent magnet (magnetrol) 14, which is a magnetic field generating means, is disposed so as not to rotate. The one-component insulating magnetic developer 10 in the developing device 9 having the stirring rod 13 is applied on the bar magnetic cylinder surface, and the magnetic toner particles are formed by friction between the flat surface of the developing sleeve 4 and the magnetic toner particles. Negative triboelectricity is given. Further, the thickness of the developer layer is made by placing an iron magnetic doctor blade 11 close to the cylindrical surface (spacing of 50 µm to 500 µm) and facing the magnetic pole position of one of the multipole permanent magnets. Thin (30 μm to 3000 μm) and uniformly regulated, a developer layer in the developing portion smaller than the distance between the electrostatic image carrier 1 and the developing sleeve 4 can be formed in a non-contact state. By adjusting the rotational speed of the developing sleeve 4, the peripheral speed of the developing sleeve 4 is approximately equal to or close to the speed of the electrostatic image bearing surface. As the magnetic doctor blade 11, a counter magnet may be formed using a permanent magnet instead of iron. In the developing unit, an alternating bias or pulse bias may be applied between the developing sleeve 4 and the electrostatic image bearing surface by the biasing means 12. This AC bias preferably has a frequency f of 200 to 4,000 Hz and V _pp of 500 to 3,000 V.

When the magnetic toner particles are transferred in the developing portion, the magnetic toner particles are transferred to the electrostatic image carrier 1 by the action of the electrostatic force of the electrostatic image bearing surface and the action of an AC bias or a pulse bias.

Instead of the doctor blade 11, by pressing the elastic blade against the surface of the correction image carrier 1 using an elastic blade molded of an elastic material such as silicone rubber, the total thickness of the developer layer is regulated or developed on the developing sleeve. You may apply an agent.

In the case of using the magnetic toner of the present invention having a specific surface-modified silica fine powder, the photoconductor 1 is an amorphous silicon drum, and even if a large amount of corona discharge current flows through the primary charger 2, the primary charger 2 The discharge wire of) can be satisfactorily prevented or suppressed from contamination.

The present invention will be described in detail based on the following examples. This invention is not limited to this.

[Preparation Example of Surface-Modified Silica Fine Powder 1]

Humid silica (specific surface area: 380㎡ / g, water content: 2.34wt%, bulk density: 26.8g / ℓ) 100 parts by weight is placed in a container with a high speed mixer and stirred at 8,500 rpm in a nitrogen atmosphere. 20 parts by weight of hexamethyldisilazane was sprayed, and stirring was continued for 5 minutes, and then the obtained powder liquid was subjected to reflux stirring at 200 ° C. for 3 hours under a nitrogen stream. Thereafter, the mixture was cooled to room temperature to obtain a surface-modified silica fine powder 1. The surface-modified silica fine powder 1 thus obtained had a specific surface area of 240 m 2 / g, a hydrophobic ratio of 79%, and a volume density of 43.5 g / l.

[Preparation Example of Surface-Modified Silica Fine Powders 2 to 7]

Surface-modified silica fine powders 2 to 7 were obtained in the same manner as in Preparation Example of surface-modified silica fine powder 1, except that the addition amounts of fumed silica and hexamethyldisilazane were changed as shown in Table 1. The results are shown in Table 1.

[Preparation Example of Comparative Surface-Modified Silica Fine Powders 1 to 4]

Comparative surface-modified silica fine powders 1 to 4 were obtained in the same manner as Surface-modified silica fine powder 1, except that the addition amounts of fumed silica and hexamethyldisilazane were changed as shown in Table 1. The results are shown in Table 1.

[Preparation Example of Comparative Surface-Modified Silica Fine Powder 5 to 8]

Commercially available surface-modified silica fine powder batch-treated, Talanox -500 (manufactured by Tulco), commercially available surface-modified silica fine powder R-812 (manufactured by Nippon Aerosil Co., Ltd.), R-972 Nippon Aerosil Co., Ltd. and the commercially available surface-modified silica fine powder RX-200 (manufactured by Megusa, Japan) were treated as surface modified silica fine powders 5 to 8, respectively. Table 1 shows various physical property values of the comparative surface modified silica fine powders 5 to 8.

TABLE 1

* 1: Commercially available surface modified silica fine powder (Taloxox-500: Hexamethylsilazane)

* 2: Commercially available surface-modified silica fine powder (R-812: hexamethyldisilazane)

* 3: Commercially available surface modified silica fine powder (R-972: Dimethyldichlorosilane)

* 4 Commercially available surface modified silica fine powder (R-200: hexamethyldisilazane)

Example 1

Styrene 86.0 parts by weight

Butyl acrylate 14.0 parts by weight

Monobutyl maleate 10.0 parts by weight

0.8 parts by weight of di-tert-butylperoxide

The mixture of substances was added dropwise to 200 parts by weight of cumene under reflux (temperature: 146 to 156 ° C.) over 4 hours, the solution polymerization was completed under cumene reflux, and the cumene was removed while raising the temperature to 200 ° C. under reduced pressure. .

30 weight part of styrene-acrylate copolymers obtained here were melt | dissolved in the mixture of the following substance, and the mixed solution was obtained.

Styrene 49.0 parts by weight

Butyl acrylate 18.0 parts by weight

Monobutyl maleate 3.0 parts by weight

0.3 parts by weight of divinylbenzene

0.8 parts by weight of benzoyl peroxide

tert-butylperoxy-2-ethylhexanoate 0.6 parts by weight

170 weight part of water which melt | dissolved 0.15 weight part of polyvinyl alcohol partial saponifieds was added to the said mixed solution, and it was set as suspension dispersion liquid with vigorous stirring. Further, 100 parts by weight of water was added, and the suspension dispersion was added to a reaction vessel substituted with a nitrogen atmosphere, followed by polymerization at about 80 ° C. for 8 hours. After the completion of the polymerization, the reaction product was filtered, washed with water and dehydrated sufficiently to obtain a styrene-acrylate air antibody composition.

100 parts by weight of the styrene-acrylate copolymer composition, 60 parts by weight of magnetite (average particle diameter: 0.2 µ, FeO content: 26.5% by weight), 2 parts by weight of the charge control agent shown in (II) -1 to the compound and low 3 parts by weight of the molecular weight ethylene-propylene copolymer was premixed with a mixer, followed by melt kneading with a twin screw extruder set at 130 캜. The kneaded material was left to cool and then roughly ground. The pulverized product was finely pulverized using a jet stream type pulverizer and classified using a wind classifier to obtain black magnetic resin particles 1 having a weight average particle diameter of 11.5 mu.

To the magnetic resin particles 1 thus obtained, 0.4 wt% of the surface-modified silica fine powder 1 was added to obtain the magnetic toner 1 of the present invention.

The performance of the magnetic toner 1 was evaluated using a commercially available electrophotographic copying machine NP-9800 (manufactured by Canon) having an amorphous silicon photosensitive drum and applying a current of about 1,000 mA to the primary charger to charge the amorphous silicon drum. An electrostatic latent image charged with an electrostatic charge was formed on the amorphous silicon drum, the magnetic toner had negative friction reduction, and the electrostatic latent image was developed by a conventional developing method.

Contamination of the discharge wire of the corona battery was evaluated based on the degree of concentration unevenness of the intermediate color image after 200,000 copies.

In order to evaluate the image density stability at the time of copying, 1,000,000 sheets of continuous copying were performed. The image density remained almost 1.40 after 1,000,000 copies from the beginning of the radiation, and no problem occurred in image reproducibility. For the purpose of evaluating the stability under various environmental conditions, the evaluation was performed under a high humidity environment with a temperature of 30 ° C. and a humidity of 85% RH, but the image concentration was stable at 1.25. Moreover, although evaluation was performed even in the low humidity environment of the temperature of 23 degreeC, and humidity of 5% RH, image density was stable at 1.35.

[Examples 2 to 7 and Comparative Examples 1 to 8]

Magnetic toner 2 in the same manner as in Example 1, except that the surface-modified silica fine powder, the amount of the surface-modified silica fine powder, the charge control agent and the charge control agent were added as shown in Table 2, respectively. -7 and comparative magnetic toners 1-8 were prepared and evaluated by the same method. The results are shown in Table 2.

In Table 2

* 1: Image density was measured using a reflectometer.

* 2: The image was reproduced in a normal temperature-humidity environment (23 degreeC / 60% RH).

* 3: The image was reproduced in a high humidity environment (30 degreeC / 85% RH).

* 4: The image was reproduced in a low humidity environment (23 ° C / 5% RH).

Evaluation standard :

A: There is no nonuniformity due to wire contamination on the half tone image.

AB: There is a slight nonuniformity due to wire contamination on the halftone image.

C: Nonuniformity due to wire contamination on the intermediate color image is remarkable.

TABLE 2

(1): Added amount of surface modified silica fine powder added to magnetic main particles

(2): amount of charge control agent added to 100 parts by weight of the binder resin

Evaluation standard :

A: Excellent

AB: Good

B: Available

C: impossible

Even when the magnetic toner of the present invention is used in a high speed copying machine, especially a high speed copying machine using an amorphous silicon drum as a photosensitive drum, the surface-modified silica fine powder is free of aggregates, has a small hydrophobic ratio, and has strong interaction with magnetic resin particles. That is, since the surface-modified silica fine powder is strong enough to be suppressed from being separated from the magnetic resin particles, contamination of the discharge wire can be remarkably prevented. In addition, since the hydrophobic ratio of the surface-modified silica fine powder is in the range of 60 to 95%, an increase in the charge amount of the magnetic toner can be suppressed at the time of radiation or in a low-humidity environment. It is possible to get

Claims (23)

Charging an amorphous silicon drum with a corona electrostatic charge, exposing the amorphous silicon drum to form an electrostatic latent image on the amorphous silicon drum, and the magnetic toner contains at least a binder resin, a charge control agent, and a magnetic powder It consists of a magnetic resin particles and a surface-modified silica fine powder, wherein the surface-modified silica fine powder is a silica fine powder treated with a hydrophobization treatment agent, the silica fine powder, a specific surface area of 180 m 2 / g or more, 60 to 95% Developing the electrostatic latent image with the magnetic toner supported on a developing sleeve to form a magnetic toner image having a hydrophobic ratio and a volume density of 35 to 49 g / l, and the magnetic toner on an amorphous silicon drum. And transferring the image to the transfer material, and fixing the magnetic toner image formed on the transfer material. The imaging method. The image forming method according to claim 1, wherein the amorphous silicon drum is charged by a corona discharger having a current of 600 mA to 2,000 mA. 2. The image forming method according to claim 1, wherein the amorphous silicon drum is charged by a corona charge having a current of 700 mA to 1,500 mA. The image forming method according to claim 1, wherein the electrostatic latent image formed on the amorphous silicon drum has an electrostatic charge, and the magnetic toner has a negative frictional charge. According to claim 1, The surface-modified silica fine powder, 100 parts by weight and hexa silica fine powder having a specific surface area of 300 m 2 / g or more, water content of 0.5% to 5% by weight and volume density of 40g / L or less Hydrophobicity prepared by a process comprising mixing 15 parts by weight to 25 parts by weight of methyldisilazane and heating the silica fine powder mixed with hexamethyldisilazane at a temperature above the boiling point of hexamethylsilazine. Image forming method characterized in that consisting of fine silica powder. The method of claim 1, wherein the surface-modified silica fine powder has a specific surface area of 200 m 2 / g to 320 m 2 / g. 3. The image forming method according to claim 2, wherein the silica fine powder has a water content of 0.7% by weight to 3% by weight. The method of claim 1, wherein the surface-modified silica fine powder has a hydrophobicity of 70% to 90%. The method of claim 1, wherein the surface-modified silica fine powder has a bulk density of 38 g / L to 45 g / L. The image forming method according to claim 1, wherein the surface-modified silica fine powder is added in an amount of 0.05 wt% to 5 wt% in the magnetic toner. The image forming method according to claim 1, wherein the surface-modified silica fine powder is added in an amount of 0.1 wt% to 4 wt% in the magnetic toner. The image forming method according to claim 1, wherein the binder resin is made of a styrene-acrylic copolymer. The image forming method according to claim 1, wherein the binder resin is made of a vinyl copolymer having a carboxyl group. The image forming method according to claim 1, wherein the binder resin is made of a styrene-acrylic copolymer having a carboxyl group. The image forming method according to claim 1, wherein the binder resin is made of a polyester resin. The image forming method according to claim 1, wherein the magnetic resin particles contain 0.1 wt% to 10 wt% of a charge control agent based on the binder resin. The image forming method according to claim 1, wherein the magnetic resin particles contain azo metal complexes. The image forming method according to claim 1, wherein the magnetic resin particles contain an azo metal complex represented by the following formula. [Wherein, M represents Sc, Ti, V, Cr, Co, Ni, Mn or Fe, Ar represents an aryl group which may have a substituent, X, X ', Y and Y' are each -S- , -O-. -CO-, -NH- or -NR- (R represents an alkyl group having 1 to 4 carbon atoms), and Ka Represents hydrogen ions, sodium ions, potassium ions, ammonium ions or organoammonium ions.] The image forming method according to claim 1, wherein the magnetic resin particles contain a basic organic acid metal complex. The method of claim 1, wherein the magnetic resin particles contain a basic organic acid metal complex represented by the following formula. [Wherein M represents Sc, Ti, V, Cr, Co, Ni, Mn or Fe and A represents (You may have a substituent which consists of alkyl groups.). (X represents a substituent consisting of a hydrogen atom, a halogen atom, a nitro group or an alkyl group) or (R represents a hydrogen atom, an alkyl or alkenyl group having 1 to 18 carbon atoms), Y Represents hydrogen ions, sodium ions, potassium ions, ammonium ions or organoammonium ions, and Z represents -O- or ]. The image forming method according to claim 1, wherein the magnetic resin particles contain 40 parts by weight to 150 parts by weight of the magnetic powder based on 100 parts by weight of the resin component. The image forming method according to claim 1, wherein the magnetic resin particles contain 0.5 parts by weight to 10 parts by weight of a waxy substance with respect to 100 parts by weight of the binder resin. 3. The image forming method according to claim 2, wherein the silica fine powder has a specific surface area of 350 m 2 / g to 500 m 2 / g.