JP2002202628A - Magnetic toner and image forming method using the magnetic toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide magnetic toners which have good fixability, excellent electrostatic charge stability and high image density even in long-term use, make it possible to obtain high-fineness images and are adequate for developing/ cleaning image formation and an image forming method. SOLUTION: The following magnetic toners are used in the image forming method of a contact electrostatic charge type: The toners contain at least a binder resin, a release agent and toner particles having magnetic powder; the weight average grain size is 3 to 20 μm; the magnetization intensity at a magnetic field 79.6 kA/m is 10 to 50 Am2/kg; the average circularity is >=0.970; the ratio of the weight average grain size to a number average grain size is <=1.4; the liberation rate of iron and iron compounds is from 0.05 to 3.00%; the temperature at which the viscosity in flow tester measurement attains 1.0×105 Pa.s is 80 to 120 deg.C and the temperature at which the viscosity attains 1.0×104 Pa.s is 100 to 150 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner for visualizing an electrostatic latent image in an image forming method such as an electrophotographic method, an electrostatic recording method, a magnetic recording method, and a toner jet method, and a method for using the toner. The image forming method.

[0002]

2. Description of the Related Art Many methods are known as electrophotography. In general, a photoconductive material is used and an electrostatic image carrier (hereinafter, also referred to as a "photoconductor") is formed by various means. An electrostatic latent image is formed on the recording medium, and then the latent image is developed with a toner to form a visible image. If necessary, the toner image is transferred to a recording medium such as paper. To obtain a copy by fixing the toner image to the toner image. Such an image forming apparatus includes a copying machine, a printer, and the like.

In recent years, LED and LBP printers have become the mainstream of printer devices in the recent market, and the direction of technology has been changed to higher resolution, that is, from 240, 300 dpi to 600, 800, 1200 dpi. ing. Accordingly, a higher definition has been required for the developing system. In addition, the functions of the copying machine have been advanced, and the digital copying machine is moving toward digitalization. In this direction, a method of forming an electrostatic charge image with a laser is mainly used, so that the direction is also moving toward a high resolution direction. Further, with the improvement of the image quality, there is a great demand for higher speed and longer life.

In the developing method used for such printers and copiers, the toner image formed on the photosensitive member in the developing step is transferred to a recording medium in the transferring step, but remains on the photosensitive member. The transfer residual toner in the image area and the fog toner in the non-image area are cleaned in a cleaning step, and the toner is stored in a waste toner container. For this cleaning step, conventionally, blade cleaning, fur brush cleaning, roller cleaning and the like have been used. From the viewpoint of the apparatus, the provision of such a cleaning apparatus inevitably increases the size of the apparatus, which is a bottleneck when aiming for a more compact apparatus. Further, from the viewpoint of ecology, a system with a small amount of waste toner is desired in terms of effective use of the toner, and a toner with high transfer efficiency and low fog is required.

Further, from the viewpoint of compactness of the apparatus, the one-component developing system is preferable because the developing device itself can be reduced in size and weight because carrier particles such as glass beads and iron powder are not required unlike the two-component system. . Further, in the two-component developing system, since it is necessary to keep the toner concentration in the magnetic toner constant, a device for detecting the toner concentration and replenishing a necessary amount of toner is required, and the developing device becomes large and heavy. On the other hand, in the one-component developing system, such an apparatus is not required, so that the apparatus can be made small and light, which is preferable.

[0006] The magnetic toner used in such an image forming process mainly comprises a binder resin and a colorant.
In addition, it generally contains an additive such as a charge control agent and a release agent for bringing out the properties required for the toner. As a colorant for the magnetic toner, magnetic powder is used as the colorant as it is, or carbon black or a nonmagnetic inorganic compound, an organic pigment, a dye, etc. are used together with the magnetic powder, and a low molecular weight polyethylene is used as a release agent. A material that is hardly compatible with the binder resin, such as low molecular weight polypropylene, is used.

However, the developing method using the insulating magnetic toner has an unstable factor related to the insulating magnetic toner to be used. The reason for this is that a considerable amount of fine powdered magnetic material is mixed and dispersed in the insulating magnetic toner, and a part of the magnetic material is exposed on the surface of the toner particles. This causes variations or deterioration of various characteristics required for the magnetic toner, such as development characteristics and durability, of the magnetic toner. This is considered to be caused by the presence of magnetic fine particles having a relatively lower resistance than the resin constituting the toner on the surface of the magnetic toner. In addition, the chargeability of the toner greatly affects development and transfer, and is closely related to image quality. Therefore, a toner capable of stably obtaining a high charge amount is desired.

On the other hand, although proposals regarding magnetic iron oxides contained in magnetic toners have been proposed, they still have points to be improved.

For example, JP-A-62-279352 proposes a magnetic toner containing a magnetic iron oxide containing a silicon element. Such magnetic iron oxide is
Although silicon element is intentionally present inside the magnetic iron oxide, there is still a point to be improved in the fluidity of the magnetic toner containing the magnetic iron oxide.

[0010] Japanese Patent Publication No. 3-9045 proposes that the shape of magnetic iron oxide is controlled to be spherical by adding a silicate. In the magnetic iron oxide obtained by this method, a large amount of silicon element is distributed inside the magnetic iron oxide because silicate is used for controlling the particle shape, and the amount of the silicon element on the surface of the magnetic iron oxide is small, The fluidity of the magnetic toner is improved to some extent due to the high smoothness of the magnetic iron oxide, but the adhesion between the binder resin and the magnetic iron oxide constituting the magnetic toner is insufficient.

Japanese Patent Application Laid-Open No. 61-34070 proposes a method for producing iron tetroxide by adding a hydrosilosilicate solution during the oxidation reaction to iron tetroxide.
Although triiron tetroxide according to this method has a Si element near the surface, the Si element exists in a layer near the surface of the triiron tetroxide, and the surface is vulnerable to mechanical shock such as friction. Have a point.

On the other hand, the toner is prepared by melt-mixing a binder resin, a colorant, and the like, uniformly dispersing the mixture, pulverizing the mixture with a fine pulverizer, and classifying with a classifier to obtain a toner having a desired particle size. Pulverization method), but there is a limit to the selection range of materials for reducing the toner particle size. For example, the resin colorant dispersion must be sufficiently brittle and capable of being pulverized with economically available manufacturing equipment. From this request,
In order to make the resin colorant dispersion brittle, when the resin colorant dispersion is actually finely pulverized at a high speed, particles having a wide particle size range are easily formed. Particles), and the magnetic powder tends to be detached from the resin during pulverization. Furthermore,
Such highly brittle materials are often further pulverized or powdered when used as a developing toner in a copying machine or the like.

On the other hand, Japanese Patent Application Laid-Open No. 2-256064 discloses a method for producing a pulverized toner in which free magnetic powder is removed by classification after pulverization. However, in the pulverization method, the magnetic iron oxide particles are essentially exposed on the surface of the toner, so that there remains a problem in the fluidity of the toner and the charging stability in a severe environment, and the transferability is poor. And there is room for further improvement.

In the pulverization method, it is difficult to completely and uniformly disperse solid fine particles such as a magnetic powder or a colorant in a resin, and depending on the degree of the dispersion, an increase in fog and a decrease in image density may occur. Cause.

That is, in the pulverization method, there is a limit to the fineness of the toner required for high definition and high image quality, and accordingly, the powder characteristics, particularly the uniform chargeability and fluidity of the toner are significantly attenuated.

In order to overcome the problems of the toner by the pulverization method as described above, and to satisfy the above requirements, a method of producing a toner by a suspension polymerization method has been proposed.

Toner by suspension polymerization (hereinafter referred to as “polymerized toner”)
Is easy to make the toner into fine particles, and since the obtained toner is spherical, it has excellent fluidity and is advantageous for high image quality.

However, when a magnetic substance is contained in the polymerized toner, the fluidity and the charging characteristics thereof are remarkably reduced, and the developability cannot be satisfied. this is,
This is because magnetic particles are generally hydrophilic and thus easily exist on the toner surface. In addition, in the granulation step when producing the polymerized toner, the hydrophilic magnetic material partially migrates to the aqueous system and exists as a free magnetic material detached from the toner. To solve this problem, it is important to modify the surface characteristics of the magnetic material.

Many proposals have been made regarding surface modification of a magnetic substance in order to improve the dispersibility and encapsulation property of the magnetic substance in the polymerized toner. For example, JP-A-59-200254, JP-A-59-200256, and JP-A-59-20025
No. 0257, JP-A-59-224102, etc., various techniques for treating a silane coupling agent for a magnetic material have been proposed. JP-A-63-250660 discloses that a silicon element-containing magnetic particle is treated with a silane coupling agent. There is disclosed a technology for processing by using the above method.

However, although the dispersibility in the toner is improved to some extent by these treatments, it is difficult to uniformly render the surface of the magnetic material hydrophobic, and the exposure of the magnetic material to the toner surface is not suppressed. However, the above-mentioned problems have not been sufficiently solved.

On the other hand, regarding the amount of magnetic substance on the toner surface,
Japanese Patent Application Laid-Open No. 7-209904 proposes a toner having a special structure in which no magnetic fine particles are present on the toner surface layer. This toner is excellent in that the magnetic powder is excellent in encapsulating property and that the magnetic powder on the toner surface is not exposed.

However, according to the embodiment, the production method of the toner is complicated and it is difficult to produce the toner on a production scale. In addition, if the toner is repeatedly used under low humidity for a long period of time, the image quality is deteriorated due to the charge-up of the toner. And further improvement was required for the stability of toner charging.

Further, many techniques for reducing the particle size of the toner, such as Japanese Patent Application Laid-Open No. 1-123253, have been disclosed for improving the image quality. However, a toner having a small particle diameter has more difficulty in uniformly dispersing and encapsulating a magnetic powder, and the various problems described above have not been sufficiently solved.

Further, a method of adding an inorganic fine powder as an external additive to toner particles for the purpose of improving the flow characteristics, charging characteristics, etc. of the toner has been proposed and widely used.

For example, an inorganic fine powder which has been subjected to a hydrophobizing treatment or an inorganic fine powder which has been subjected to a hydrophobizing treatment according to JP-A-5-66608, JP-A-4-9860 or the like and further treated with a silicone oil or the like is added. Or JP-A-61-2
In JP-A-49059, JP-A-4-264453 and JP-A-5-346682, there are known methods in which a hydrophobic-treated inorganic fine powder and a silicone oil-treated inorganic fine powder are added in combination.

Also, many methods for adding conductive fine particles as an external additive have been proposed. For example, carbon black as conductive fine particles is used to impart conductivity to the toner, or to adhere or adhere to the toner surface for the purpose of suppressing excessive charging of the toner and making the tribo distribution uniform. It is widely known for use as an external additive. Also, JP-A-57-151952, JP-A-59-168458 and JP-A-60-6
No. 9660 discloses that conductive fine particles of tin oxide, zinc oxide and titanium oxide are externally added to a high-resistance magnetic toner. Also, JP-A-61-275
864, JP-A-62-258472, JP-A-61-141452, JP-A-02-12086
In JP-A-5, graphite, magnetite,
It is disclosed to add conductive polypyrrole particles and conductive polyaniline particles, and it is known to add various kinds of conductive fine particles to toner.

However, these proposals also have room for further improvement in improving the above-mentioned problem when toner particles having a smaller particle size are used to increase the resolution.

In recent years, space saving, cost reduction, and low power consumption due to miniaturization of copiers and printers have become very important issues, and the fixing device has been downsized, the apparatus has been simplified, and power consumption has been reduced. Things are needed.
Along with this, the toner lowers the viscosity of the toner at the time of melting and increases the bonding area with the fixing base material, or contains a release agent so that the toner can exhibit sufficient fixing performance with a low calorie and a low pressure. For example, there is a demand for improved fixability. For this reason, it is required to lower the Tg and the molecular weight of the binder resin used. However, a toner mainly composed of a soft component has problems that it is difficult to achieve compatibility with high-temperature offset resistance, and furthermore, there is a problem that developability in long-term use is reduced and sticking to a photoreceptor easily occurs.

On the other hand, regarding the improvement of the fixing property, for example,
JP-A-6-282098 discloses that the melt viscosity of a binder resin of a magnetic toner measured by a flow tester is specified.
A toner having excellent fixability has been proposed. The publication is
The surface of the magnetic material to be used is treated with inorganic fine particles so that the magnetic material is combined with a binder resin having a low melt viscosity so that the fixing property, the anti-offset property and the developing property are compatible. However, in the case of a toner having excellent transferability and high circularity, compatibility with developability is insufficient.

Japanese Patent Application Laid-Open No. Hei 8-137262 proposes a low melting point toner having a defined softening point temperature measured by a flow tester. This publication proposes a photoreceptor shaving means as a means for suppressing toner filming on a photoreceptor, which is likely to occur by using a low melting point toner. Is not a solution.

Furthermore, Japanese Patent Application Laid-Open No. 2000-284534 proposes a toner having excellent fixability containing a resin having a defined softening point temperature measured by a flow tester. The publication specifically describes a non-magnetic toner, and when applied to a magnetic toner, a sufficient effect cannot be obtained.

On the other hand, as a conventional image forming method, various methods such as an electrostatic recording method, a magnetic recording method, and a toner jet method are known. For example, in electrophotography, an electrostatic latent image is generally formed on a photoreceptor using a photoconductive substance as an image carrier by various means, and then the latent image is developed with toner. After the toner image is transferred to a recording medium such as paper as needed as a visual image, the toner image is fixed on the recording medium by heat, pressure or the like to obtain an image.

As a method for visualizing an electrostatic latent image, a cascade developing method, a magnetic brush developing method, a pressure developing method and the like are known. Further, a method is also used in which a magnetic toner is used and a rotating sleeve having a magnetic pole disposed at the center is used to fly between the photosensitive member and the sleeve by an electric field.

For example, in Japanese Patent Application Laid-Open No. 54-43027, a magnetic toner is thinly coated on a magnetic toner carrier, triboelectrically charged, and then brought close to an electrostatic latent image under the action of a magnetic field. A method is disclosed in which the toner is developed without being in contact with the developer. According to this method, by applying the magnetic toner thinly on the magnetic toner carrier, sufficient frictional charging of the magnetic toner becomes possible, and the development can be performed without contacting the electrostatic latent image while supporting the magnetic toner by a magnetic force. Since the transfer is performed, transfer of the magnetic toner to the non-image portion, that is, fogging is suppressed, and a high-definition image can be obtained.

Regarding transfer efficiency, transfer efficiency is generally high when a toner having a high and uniform charge amount distribution is used. However, as described above, such a magnetic toner is still improved. Have points to do.

It is said that spherical toner has high transfer efficiency because of its shape. In this regard, JP-A-61-2
No. 79864 discloses shape factors SF1 and SF2.
A proposal has been made in which Japanese Patent Application Laid-Open No. 63-2359
No. 53 proposes a magnetic toner which has been made spherical by mechanical impact. However, the transfer efficiency of these toners is still insufficient, and further improvement is needed.

On the other hand, such a spherical toner has the advantage that the transfer efficiency is higher than that of the pulverized toner, but also has the property that it is difficult to clean because of the spherical shape. Furthermore, as described above, the toner particle size is in the direction of smaller particle size, and it is more difficult to completely remove the transfer residual toner. However, by improving the cleaning device, it is possible to suppress toner slippage to a level that does not cause a serious problem, and it is possible to form an image having no practical problem in the conventional image forming method having a corona charging method. It is possible.

However, in recent years, primary charging and transfer processes using corona discharge, which have been conventionally used from the viewpoint of environmental protection, have been replaced with primary charging using a photosensitive member contacting member having great advantages such as low ozone and low power. (Contact charging) and a transfer process (contact transfer) are becoming mainstream.

For example, JP-A-63-149669 and JP-A-2-123385 have been proposed. These are related to a contact charging method and a contact transfer method, in which a conductive elastic roller is brought into contact with a photoconductor, and the surface of the photoconductor is uniformly charged while applying a voltage to the conductive roller.
Next, after a toner image is obtained by an exposure and development process, a transfer material is passed through the transfer member while pressing another conductive roller to which a voltage is applied to the photosensitive member, and the toner image on the photosensitive member is transferred to the transfer material. After that, a copy image is obtained through a fixing process.

However, it has been found that the contact charging method or the contact transfer method has a problem to be concerned, unlike the case where corona discharge is used.

Specifically, in the case of the contact charging method, first, the charging member is pressed against the surface of the photosensitive member with a pressing pressure.
Therefore, it is difficult to maintain sufficient contact between the contact charging member and the photoreceptor due to the presence of the untransferred residual toner, that is, the transfer residual toner, and the chargeability deteriorates. Transfer of the toner, that is, fogging is likely to occur. Further, since the toner is accumulated on the charging member, the photosensitive member cannot be uniformly charged, resulting in a decrease in image density and roughness. Further, since the charging member is in pressure contact, toner fusion is likely to occur, and these tendencies become more remarkable as the transfer residual toner increases.

Next, in the case of the contact transfer method, the transfer member is brought into contact with the photoreceptor via the transfer member at the time of transfer, so that the toner image formed on the photoreceptor is transferred to the transfer material. Are pressed against each other, which causes a problem of partial transfer failure called so-called "missing transfer". In addition, as the direction of technology in recent years, a higher resolution and higher definition developing method has been required, and in order to respond to such a demand, the particle diameter of the toner has been reduced, but this has been progressing. As described above, as the toner particle diameter becomes smaller, the adhesion force (mirror force, van der Waals force, etc.) of the toner particles to the photoconductor becomes larger than the Coulomb force applied to the toner particles in the transfer process, and as a result, the transfer is performed. The residual toner increases, and the transfer failure tends to be further deteriorated.

As described above, in an image forming method using a contact charging method and a contact transfer method, which are very preferable in consideration of the environment, a magnetic toner having high transferability, excellent charge stability, and less likely to cause toner fusion, and Development of an image forming method is desired.

On the other hand, with respect to the toner having a high transfer efficiency as described above, a system called development / cleaning or cleanerless has been proposed as a system without waste toner.

However, the disclosure of the conventional technology relating to both development and cleaning or cleanerless is disclosed in Japanese Patent Application Laid-Open No. H5-25-2.
As disclosed in Japanese Patent No. 287, the main focus is on a positive memory, a negative memory, and the like due to the influence of residual toner on an image. However, as the use of electrophotography is progressing, there is a need to transfer toner images to various recording media, and in this sense, it is not satisfactory for various recording media.

JP-A-59-133573, JP-A-62-203182, and JP-A-63-133179 disclose techniques related to cleanerless.
Gazette, JP-A-64-20587, JP-A-2-3
JP-A-02772, JP-A-5-2289, JP-A-5-53482, JP-A-5-61383, etc., but there is no description of a desirable image forming method, and the toner composition is also mentioned. Not.

As a developing method preferably applied to both the developing and cleaning or the cleaner-less operation, in the conventional developing and cleaning essentially having no cleaning device, it is essential to rub the surface of the image carrier with toner and the toner carrier. Therefore, many contact development methods have been studied in which the toner or the toner contacts the image carrier. this is,
This is because a configuration in which the toner or the toner contacts and rubs against the image carrier in order to collect the transfer residual toner in the developing unit is considered to be advantageous. However, the development / cleaning or cleanerless process to which the contact development method is applied causes toner deterioration due to long-term use, deterioration of the surface of the toner carrier, deterioration or wear of the photoconductor surface,
There is no sufficient solution to the durability characteristics. Therefore, a developing and cleaning method using a non-contact developing method is desired.

Here, it is assumed that the contact charging method is applied to a developing / cleaning method and a cleanerless image forming method. In the developing / cleaning method and the cleaner-less image forming method, the transfer residual toner remaining on the photoreceptor because it does not have a cleaning member directly contacts the contact charging member and adheres or mixes. Further, in the case of a charging method in which a discharge charging mechanism is dominant, the deterioration of the toner due to the discharge energy deteriorates the adhesion to the charging member. If the generally used insulating toner adheres to or mixes with the contact charging member, the charging property is reduced.

In the case of the charging method in which the discharge charging mechanism is dominant, the charging property of the member to be charged decreases sharply from the point where the toner layer adhered to the surface of the contact charging member becomes a resistance inhibiting the discharge voltage. Get up. On the other hand, in the case of the charging method in which the direct injection charging mechanism is dominant, the transfer residual toner adhered or mixed reduces the probability of contact between the surface of the contact charging member and the member to be charged, thereby charging the member to be charged. Is reduced.

The decrease in the uniform chargeability of the charged body causes a decrease in the contrast and uniformity of the electrostatic latent image after image exposure, thereby lowering the image density or increasing fog.

In the developing / cleaning method and the cleaner-less image forming method, the charge polarity and the charge amount of the transfer residual toner on the photoreceptor are controlled, and the transfer residual toner is stably collected in the developing process. The point is to keep the development characteristics from deteriorating, and the charge polarity and the charge amount of the transfer residual toner are controlled by the charging member.

This will be specifically described using a general laser printer as an example. In the case of reversal development using a charging member to which a negative polarity voltage is applied, a negatively charging photoreceptor, and a negatively charging toner, in the transfer step, an image visualized by a positive polarity transfer member is transferred to a recording medium. However, depending on the relationship between the type of recording medium (differences in thickness, resistance, dielectric constant, etc.) and the image area, the charge polarity of the transfer residual toner varies from plus to minus. However, due to the negative polarity charging member when charging the negatively charged photoreceptor, even the residual toner along with the surface of the photoreceptor is uniformly moved to the negative side even if it swings to the positive polarity in the transfer process. The charging polarity can be made uniform.

Therefore, when the reversal development is used as the developing method, a negatively charged transfer residual toner remains in a light portion potential portion of the toner to be developed, and a dark portion potential not to be developed of the toner. Is attracted toward the toner carrier due to the development electric field, and the transfer residual toner is collected without remaining on the photosensitive member having the dark portion potential. That is, by controlling the charging polarity of the toner remaining after transfer simultaneously with the charging of the photosensitive member by the charging member, the developing / cleaning and cleanerless image forming method is realized.

However, if the transfer residual toner adheres to or mixes with the contact charging member beyond the ability to control the toner charging polarity of the contact charging member, the charge polarity of the transfer residual toner cannot be uniformed, and the developing member may not be uniform. It becomes difficult to collect the toner. Even if the toner remaining on the toner carrier is collected by mechanical force such as rubbing, if the charge of the transfer residual toner is not uniform, the chargeability of the toner on the toner carrier is adversely affected, and the developing property is deteriorated. Lower.

That is, in the developing / cleaning and cleanerless image forming method, the charge control characteristics of the transfer residual toner when passing through the charging member and the adhesion / mixing characteristics to the charging member are closely linked to the durability characteristics and the image quality characteristics. ing.

Japanese Patent Publication No. 7-99442 discloses a configuration in which powder is applied to a contact charging member with a surface to be charged in order to prevent charging unevenness and perform stable uniform charging. However, the contact charging member (charging roller) is driven to rotate by the member to be charged (photoreceptor) (no speed difference drive), and the generation of ozone products is significantly reduced as compared with a corona charger such as a scorotron. However, the charging principle is still mainly a discharge charging mechanism as in the case of the roller charging described above. In particular, since a voltage obtained by superimposing an AC voltage on a DC voltage is applied to obtain more stable charging uniformity, the generation of ozone products due to discharge is increased. Therefore, when the apparatus is used for a long time, adverse effects such as image deletion due to ozone products are likely to appear. Further, when the present invention is applied to a cleanerless image forming apparatus, it becomes difficult for the applied powder to uniformly adhere to the charging member due to mixing of transfer residual toner, and the effect of performing uniform charging is weakened.

Japanese Patent Application Laid-Open No. 5-150539 discloses that, in an image forming method using contact charging, toner particles and silica fine particles which cannot be completely cleaned by a cleaning means such as a blade while image formation is repeated for a long time. It is disclosed that the toner contains at least visible particles and conductive fine particles having an average particle size smaller than the visible particles in order to prevent charging inhibition due to adhesion and accumulation on the surface of the charging means. I have. However, the contact charging or the proximity charging used here is based on the discharge charging mechanism, and has the above-mentioned problem due to the discharge charging, not the direct injection charging mechanism.

Further, when the present invention is applied to a cleanerless image forming apparatus, as compared with a case having a cleaning mechanism, a large amount of conductive fine particles and untransferred toner pass through the charging step, thereby affecting the chargeability. No consideration is given to the recoverability of the large amount of the conductive fine particles and the transfer residual toner in the developing step, and the influence of the collected conductive fine particles and the transfer residual toner on the developing characteristics of the toner. Furthermore, when a direct injection charging mechanism is applied to contact charging,
A necessary amount of the conductive fine particles is not supplied to the contact charging member, and a charging failure occurs due to the influence of the transfer residual toner.

In proximity charging, it is difficult to uniformly charge the photosensitive member with a large amount of conductive fine particles and transfer residual toner, and the effect of leveling the pattern of the transfer residual toner cannot be obtained. A pattern ghost for blocking image exposure occurs. Furthermore, when the power supply is momentarily interrupted or paper jam occurs during image formation, toner contamination inside the apparatus becomes remarkable.

Japanese Patent Application Laid-Open No. H11-15206 discloses a method of forming a developing / cleaning image which improves the developing / cleaning performance by improving the charge control characteristics of the transfer residual toner when passing through the charging member. An image forming method using a toner having toner particles containing carbon black and a specific azo-based iron compound and inorganic fine powder has been proposed. Further, in the developing and cleaning image forming method, it has been proposed to improve the developing and cleaning performance by reducing the amount of transfer residual toner by using a toner having excellent transfer efficiency with a specified toner shape factor.

However, the contact charging used here is also based on the discharge charging mechanism, and has the above-mentioned problem due to the discharge charging instead of the direct injection charging mechanism. Further, these proposals have an effect of suppressing a decrease in chargeability due to transfer residual toner of the contact charging member, but cannot expect an effect of positively increasing chargeability.

Further, some commercially available electrophotographic printers use a roller member which comes into contact with the photoreceptor between the transfer step and the charging step, and a developing and cleaning device which assists or controls the recoverability of the transfer residual toner in the development. There is also an image forming apparatus. Such an image forming apparatus exhibits good developing and cleaning properties and can greatly reduce the amount of waste toner, but increases costs and impairs the advantages of developing and cleaning in terms of downsizing.

On the other hand, JP-A-10-307456
Discloses an image forming apparatus which is applied to a developing / cleaning image forming method using a direct injection charging mechanism of a toner containing conductive charge-promoting particles having a particle diameter equal to or smaller than 1/2 of the toner particle diameter. ing. According to this proposal, it is possible to greatly reduce the amount of waste toner without generating a discharge product, and to obtain a developing and cleaning image forming apparatus which is advantageous in miniaturization at a low cost, and has poor charging, light shielding in image exposure. Alternatively, a good image free from diffusion can be obtained.

Japanese Patent Application Laid-Open No. 10-307421 discloses a developing and cleaning image forming method using a direct injection charging mechanism of toner containing conductive particles having a particle diameter of 1/50 to 1/2 of the toner particle diameter. There is disclosed an image forming apparatus which is applied to a method and in which conductive particles have a transfer promoting effect.

Further, Japanese Patent Application Laid-Open No. 10-307455 discloses that the particle size of the conductive fine powder is set to be equal to or smaller than the size of one pixel of the constituent pixels, and the particle size of the conductive fine powder is obtained in order to obtain better charging uniformity. It is described that the diameter is 10 nm to 50 μm.

In Japanese Patent Application Laid-Open No. 10-307457, conductive particles are made to have a size of about 5 μm in consideration of the visual characteristics of human beings so as to make it difficult to visually recognize the influence of the poorly charged portion on the image.
m, preferably 20 nm to 5 μm.

Further, according to JP-A-10-307458, the particle size of the conductive fine powder is set to be equal to or smaller than the toner particle size, so that the development of the toner is hindered during development, or the developing bias is reduced. To prevent image defects and prevent image leakage, and by setting the particle size of the conductive fine powder to be larger than 0.1 μm,
A developing and cleaning image forming method using a direct injection charging mechanism for solving the problem of embedding conductive fine powder in an image carrier and blocking light exposure and realizing excellent image recording is described.

According to JP-A-10-307456, a conductive fine powder is externally added to a toner, and at least a contact portion between the flexible contact charging member and the image bearing member is electrically conductive. The fine powder adheres to the image carrier in the developing process and remains on the image carrier after the transfer process, and is carried and interposed. Is disclosed.

However, these proposals still have room for further improvement in performance when toner particles having a smaller particle size are used in order to enhance stable performance and resolution in repeated use over a long period of time.

[0070]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic toner and an image forming method which solve the above-mentioned problems of the prior art.

That is, an object of the present invention is to provide a magnetic toner and an image forming method which have good fixability, excellent charge stability, high image density even after long-term use, and which can obtain a high-definition image. To provide.

An object of the present invention is to provide an image forming method capable of forming a good developing and cleaning image.

Another object of the present invention is to provide an image forming method capable of forming a cleaner-less image in which good chargeability is stably obtained.

[0074]

The present invention includes at least a binder resin, a release agent, and toner particles having a magnetic powder, a weight average particle diameter of 3 to 20 μm, and a magnetic field of 79.6.
Magnetization intensity at kA / m is 10 to 50 Am ² / kg
Wherein the average circularity of the magnetic toner is 0.970 or more, and the ratio of the weight average particle diameter to the number average particle diameter of the magnetic toner is 1.40 or less; The temperature at which the release ratio of the iron compound is from 0.05% to 3.00% and the viscosity of the magnetic toner measured by a flow tester is 1.0 × 10 ⁵ Pa · s is from 80 to
The present invention relates to a magnetic toner, which has a temperature of 120 ° C. and a temperature of 1.0 × 10 ⁴ Pa · s is 100 to 150 ° C.

The present invention also provides a charging step of charging an image carrier, an electrostatic latent image forming step of writing image information as an electrostatic latent image on the charged image carrier, and holding of the electrostatic latent image on the surface. The developing unit is formed by arranging the image bearing member to be fixed and the magnetic toner carrying member carrying the magnetic toner on the surface at a predetermined interval, and forming the magnetic toner on the surface of the magnetic toner carrying body with a thickness smaller than the above-mentioned spacing. A developing step of forming a toner image by transferring the magnetic toner to an electrostatic latent image in a developing section to which an alternating electric field is applied, and a transfer step of transferring the toner image to a recording medium. In an image forming method in which an image is repeatedly formed on a carrier, the magnetic toner includes:
Including at least a binder resin, a release agent, and toner particles having a magnetic powder, a weight average particle diameter of 3 to 10 μm,
Magnetization intensity in a magnetic field of 79.6 kA / m is 10 to 50
A magnetic toner having an Am ² / kg, an average circularity of 0.970 or more, a ratio of a weight average particle diameter to a number average particle diameter of 1.40 or less, and a free ratio of iron and an iron compound. 0.05 to 3.00%, and the temperature at which the viscosity measured by a flow tester is 1.0 × 10 ⁵ Pa · s is 80.
To 120 ° C. and a temperature of 1.0 × 10 ⁴ Pa · s is 100 to 150 ° C., wherein the charging step forms a contact portion with the image carrier. An image forming method, wherein the image carrier is charged by applying a voltage to a charging member that comes into contact therewith.

[0076]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the magnetic toner of the present invention will be described. The present inventors have conducted intensive studies and found that when the average circularity of the magnetic toner is 0.970 or more, the transferability of the magnetic toner becomes very good. This is because the contact area between the toner particles and the photoreceptor is small,
It is considered that the adhesion of the toner particles to the photoreceptor due to the mirroring power, van der Waals force, and the like is reduced. Further, since the circularity of the toner is as high as 0.970 or more, the magnetic toner forms uniform thin spikes in the developing section, and can faithfully develop the latent image, thereby improving the image quality.

The magnetic toner of the present invention preferably has a mode circularity of 0.99 or more in the circularity distribution of the magnetic toner. When the mode circularity is 0.99 or more, it means that many of the toner particles have a shape close to a true sphere, and the above-mentioned action is more remarkable, which is preferable.

Therefore, when such a magnetic toner is used, the transfer efficiency is high and the transfer residual toner is reduced, so that the toner in the pressure contact portion between the charging member and the photoreceptor becomes very small, and stable charging is performed. It is considered that toner fusion is prevented and image defects are remarkably suppressed.

These effects become more prominent in an image forming method including a contact transfer step in which a dropout during transfer is likely to occur.

The average circularity in the present invention is used as a simple method for quantitatively expressing the shape of particles, and is an index of the degree of unevenness of the magnetic toner. In the present invention, the circularity (Ci) of each particle measured for a particle group having a circle equivalent diameter of 3 μm or more is determined by the following equation (1), and all the particles measured as shown by the following equation (2) Is defined as the average circularity (C) obtained by dividing the sum of the circularities by the total number of particles (m). Average circularity in the present invention,
When the magnetic toner has a perfect spherical shape, the value is 1.000, and the average circularity becomes smaller as the surface shape of the magnetic toner becomes more complicated.

[0081]

(Equation 1)

(Equation 2)

The average circularity in the present invention can be determined, for example, by using a flow-type particle image analyzer “FPIA-100” manufactured by Toa Medical Electronics.
0 ".

The mode circularity is 0.40.
To 1.00 are divided into 61 in increments of 0.01, and the circularity of the measured particles is allocated to each divided range according to each circularity, and the circularity of the peak having the maximum frequency value in the circularity frequency distribution It is.

The above-mentioned measuring device “FPIA-1”
After calculating the circularity of each particle, in calculating the average circularity and the mode circularity, the particles are divided into classes obtained by dividing the circularity from 0.40 to 1.00 into 61 according to the obtained circularity, A calculation method of calculating the average circularity and the mode circularity using the center value and the frequency of the division point is used. However, an error between each value of the average circularity and the mode circularity calculated by this calculation method and each value of the average circularity and the mode circularity calculated by the above-described calculation formula directly using the circularity of each particle. Is very small and substantially negligible.In the present invention, for the reasons of data handling such as short-circuiting of calculation time and simplification of calculation formula, each particle described above is not used. Such a calculation method that is partially modified using the concept of a calculation formula that directly uses circularity may be used.

A specific example of the procedure for measuring the average circularity and the mode circularity is as follows. Surfactant about 0.
Approximately 5m of magnetic toner in 10mL of water in which 1mg is dissolved
g was dispersed to prepare a dispersion, and ultrasonic waves (20 KHz,
50 W) to the dispersion for 5 minutes, and when the concentration of the dispersion is 500
The measurement was carried out by the above-mentioned apparatus at 0 to 20,000 / μL,
The average circularity and mode circularity of a particle group having a circle equivalent diameter of 3 μm or more are determined.

In the present invention, the reason why the circularity is measured only for particles having a circle equivalent diameter of 3 μm or more is 3 μm.
This is because the particle group having a circle-equivalent diameter of less than m includes a large number of particles of the external additive that are present independently of the toner particles, and the circularity of the toner particle group cannot be accurately estimated due to the influence. .

The magnetic toner of the present invention is characterized in that the release rate of iron and iron compounds is 0.05 to 3.00%.
This release rate is preferably 0.05 to 2.00%, more preferably 0.05 to 1.50%, and still more preferably 0.05 to 2.00%.
5 to 1.00%. As described above, the magnetic toner of the present invention contains a magnetic powder. Accordingly, in the present invention, the release rate of iron and iron compound specifically indicates the ratio of the number of magnetic powders released from toner particles.

The release rate of iron and iron compounds can be measured, for example, by introducing a magnetic toner into plasma and then measuring the emission spectrum. In this case, the release rate is a value defined by the following equation based on the simultaneity of the emission of carbon atoms, which are constituent elements of the binder resin, and the emission of iron atoms.

[0089]

(Equation 3)

Here, "simultaneous light emission" means that light emission of iron atoms emitted within 2.6 msec from light emission of carbon atoms is simultaneous light emission, and light emission of iron atoms thereafter is light emission of only iron atoms.

In the present invention, since a large amount of magnetic powder is contained, simultaneous emission of carbon atoms and iron atoms means that toner particles contain magnetic powder, and only iron atoms are contained. Light emission can be rephrased to mean that the magnetic powder is separated from the toner particles.

The release rates of the above iron and iron compounds were determined according to Jap.
The measurement can be carried out based on the principle described on pages 65-68 of the Transactions of An Hardcopy 97. In such a case, for example, a particle analyzer (PT1000: manufactured by Yokogawa Electric Corporation) is preferably used. . More specifically, the apparatus introduces fine particles such as toner into the plasma one by one, and can determine the element, the number of particles, and the particle diameter of the luminescent material from the emission spectrum of the fine particles.

A specific measuring method using the above measuring device is as follows. Using a helium gas containing 0.1% oxygen, the measurement is performed in an environment of 23 ° C. and a humidity of 60%. In addition, a carbon atom (measuring wavelength 247.860 nm, K factor uses a recommended value) in channel 1 and an iron atom (measuring wavelength 239.56 n
The m and K factors used were 3.3764), and the emission number of carbon atoms was 1000 to 1400 in one scan.
Sampling is performed so that the number of emitted light atoms is counted, and scanning is repeated until the total number of emitted light atoms of carbon atoms becomes 10,000 or more, and the number of emitted light atoms is integrated. At this time, in a distribution in which the number of emitted carbon elements is on the vertical axis, and the cube root voltage of the carbon element is on the horizontal axis, the distribution has one maximum, and further, the distribution has no valley. Sampling and measurement. Then, based on this data, the noise cut levels of all elements are set to 1.50 V, and the release rate of iron and iron compounds is calculated using the above formula. The same measurement was performed in Examples described later.

Materials other than inorganic compounds containing iron atoms, such as an azo-based iron compound as a charge control agent, may be contained in the toner particles in some cases. At the same time, carbon in the organic compound emits light at the same time, and is not counted as a free iron atom.

The inventors of the present invention have studied and found that there is a strong relationship between the release rate of iron and iron compounds and the amount of exposure to the surface of toner particles, and that the amount of free magnetic powder is 3.00% or less. For example, it was found that the exposure of the magnetic powder to the surface of the toner particles was suppressed and that the toner had a high charge amount. The release rate of iron and iron compounds depends on the degree of hydrophobicity of the magnetic powder, the compatibility with the resin, the particle size distribution, the uniformity of the treatment, and the like. In this case, the magnetic powder that has not been sufficiently subjected to the surface treatment (has a strong hydrophilicity) tends to be present on the surface layer of the toner particles, and a part or all of the magnetic powder is released. Therefore, the lower the release rate of iron and iron compounds, the higher the charge amount of the magnetic toner.

On the other hand, if the release rate is larger than the above range, the leak point of the charge becomes too large, and the charge amount of the toner may be reduced. This tendency becomes particularly remarkable under high temperature and high humidity. Further, a toner having a low charge amount is not preferable because it causes an increase in fog and also lowers the transfer efficiency. Further, such a toner having a large release rate of iron and iron compound has a slightly poor fixability. this is,
This is probably because the magnetic powder having a large specific heat is present on the toner surface or is present separately from the toner, so that sufficient heat is not transmitted to the toner during fixing.

On the other hand, the release rate of iron and iron compounds is 0.05
% Means that the magnetic powder is not substantially released from the toner particles. As described above, the magnetic toner having a low release rate of iron and an iron compound has a high charge amount, but in the case of forming a large number of sheets, particularly in the case of forming a large number of sheets under low temperature and low humidity, the image density caused by the charge-up of the magnetic toner is increased. And the image becomes rough.
We believe this is for the following reasons.

Generally, the magnetic toner on the magnetic toner carrier is not entirely developed on the photosensitive member, and the magnetic toner exists on the magnetic toner carrier immediately after the development.
This tendency is particularly strong in jumping development using a magnetic toner, and the development efficiency is not so high. Further, as described above, the magnetic toner having a high circularity forms uniform thin spikes in the developing section, and is developed from the magnetic toner existing at the tip of the spikes. It is considered that it is not easily developed.

As a result, the magnetic toner in the vicinity of the magnetic toner carrier is repeatedly subjected to frictional charging by the charging member, and is charged up. Further, in such a state, the charging uniformity of the magnetic toner is impaired, and the image becomes rough.

Here, the release rate of iron and iron compounds is 0.0
When 5% or more of the toner is used, charge-up of the magnetic toner is suppressed by free magnetic powder or magnetic powder slightly existing on the surface of the toner particles, and the uniformity of the charge amount of the magnetic toner is reduced. It is encouraged and rust is suppressed.

For these reasons, in order to stably obtain a high charge amount, the release rate of iron and iron compounds needs to be 0.05% to 3.00%.

Further, the magnetic toner of the present invention has a high average circularity and a low liberation rate of iron and iron compounds as in the magnetic toner of the present invention.
Then, due to the synergistic effect of the uniformly high charge amount of the magnetic toner, the transfer efficiency becomes very high, and the fog becomes very small. Also, scattering of the magnetic toner is reduced, and the image quality is improved. Further, such a magnetic toner hardly undergoes selective development even in long-term use, and a difference in toner physical properties before and after use hardly occurs, so that the durability is also improved.

On the other hand, as disclosed in JP-A-5-150539 and JP-A-8-22191, charge-up can be suppressed by externally adding magnetite to an irregular toner surface. . However, when magnetite is externally added to a magnetic toner having an average circularity of 0.970 or more as in the present invention, fog is increased and the chargeability particularly under high temperature and high humidity is deteriorated. The reason for this is not clear, but a large amount of low resistance material such as magnetite is present on the surface of the toner particles, and when a relatively smooth magnetic toner having an average circularity of 0.970 or more is used. It is believed that this is because the shear is not sufficiently applied when magnetite is mixed, and the magnetite does not uniformly adhere to the surface of the toner particles, resulting in a difference in the amount of adhesion between the toner particles.

In the image forming method of the present invention, the weight average diameter of the magnetic toner is preferably from 3 to 20 μm, more preferably from 4 to 20 μm, in order to further develop finer latent image dots faithfully for higher image quality. More preferably, it is 9 μm. In the case of a toner having a weight average particle diameter of less than 3 μm, transfer residual toner on the photoreceptor increases due to a decrease in transfer efficiency, and it becomes difficult to suppress abrasion of the photoreceptor and toner fusion in the contact charging step. Furthermore, in addition to an increase in the surface area of the entire magnetic toner, the fluidity and agitation properties of the powder decrease, and it becomes difficult to uniformly charge the individual toner particles, so that fog and transferability tend to deteriorate. This is not preferable for the magnetic toner used in the present invention, because it is liable to cause non-uniform unevenness of an image in addition to scraping and fusing.

The magnetic toner has a weight average particle diameter of 20 μm.
If it exceeds m, scattering is likely to occur in characters and line images, and it is difficult to obtain high resolution. Further, as the resolution of the apparatus becomes higher, the reproduction of one dot tends to be deteriorated for the toner of 20 μm or more.

Further, the magnetic toner of the present invention has a ratio of the weight average particle diameter to the number average particle diameter, ie, weight average particle diameter /
It is important that the ratio (D4 / D1) of the number average particle size is 1.40 or less, and more preferably 1.35 or less.

The ratio of weight average particle diameter / number average particle diameter is 1.4.
A value larger than 0 means that a large number of fine powders and coarse particles are present in the magnetic toner, which is not preferable because the selective development is likely to occur and the charge amount distribution is widened.

On the other hand, in a magnetic toner having a weight average particle diameter / number average particle diameter ratio of 1.40 or less, particularly 1.35 or less,
According to the shape factor of the magnetic toner that the average circularity of the magnetic toner is 0.970 or more, the synergistic effect of the particle size distribution that the particle size is uniform, the spikes in the developing unit become very uniform, An image having very excellent reproducibility can be obtained.

Here, the average particle size and particle size distribution of the magnetic toner can be measured by various methods such as Coulter Counter TA-II or Coulter Multisizer (manufactured by Coulter Co., Ltd.). Interface (made by Nikkaki) and PC9 that output the number distribution and volume distribution using
The measurement is preferably performed by connecting an 801 personal computer (manufactured by NEC). In the above measurement, a 1% NaCl aqueous solution is prepared using primary sodium chloride as the electrolytic solution. The electrolytic solution includes, for example, ISOTON R-II
(Manufactured by Coulter Scientific Japan) can be used.

As a specific measuring method of the above measurement, a surfactant, preferably an alkylbenzene sulfonate, is used as a dispersant in 100 to 150 mL of the electrolytic aqueous solution.
Add 1-5 mL, and further add 2-20 mg of the measurement sample. The electrolytic solution in which the sample was suspended was subjected to a dispersion treatment for about 1 to 3 minutes with an ultrasonic disperser, and the volume and the number of toner particles of 2 μm or more were measured using the Coulter Multisizer with a 100 μm aperture as the aperture. The distribution and the number distribution are calculated. Then, a volume-based weight average particle diameter (D4) obtained from the volume distribution and a number-based length average particle diameter obtained from the number distribution, that is, a number average particle diameter (D1) are obtained. The same measurement was performed in Examples described later.

The magnetic toner of the present invention has a temperature at which the viscosity measured by a flow tester is 1.0 × 10 ⁵ Pa · s is 80 to 120 ° C., and is 1.0 × 10 ⁴ Pa · s. A temperature of 100 to 150 ° C. Further, the temperature at which the temperature becomes 1.0 × 10 ⁵ Pa · s is from 80 to 110
° C, and the temperature at which 1.0 × 10 ⁴ Pa · s is reached is 100 to 100 ° C.
Preferably it is 140 ° C.

When the temperature at which the viscosity becomes 1.0 × 10 ⁵ Pa · s is less than 80 ° C., or when the temperature at which the viscosity becomes 1.0 × 10 ⁴ Pa · s is less than 100 ° C., However, in such a low-viscosity magnetic toner, the magnetic powder near the surface of the toner particles may be exposed or even fall off. In addition, the release rate fluctuates due to durability due to factors such as the embedding of an external additive. As a result, the fluidity and chargeability of the magnetic toner change, and the developability and transferability may be impaired.

In particular, in the case of a magnetic toner having a high degree of circularity and excellent fluidity and transferability as in the present invention, the contact area with the inside of a developing device or a charging member becomes large, so that the above-mentioned phenomenon becomes more serious. It is easy to occur. Furthermore, 1.0 × 1
If the temperature at which 0 ⁴ Pa · s is less than 100 ° C., the offset resistance may be impaired.

Conversely, when the temperature at which the viscosity becomes 1.0 × 10 ⁵ Pa · s exceeds 120 ° C., or when the temperature becomes 1.0 × 10 ⁴ Pa · s
When the temperature exceeds 150 ° C., the fluctuation of the release rate can be suppressed, but the low-temperature fixability is impaired, which is not preferable. That is, the present invention balances the circularity of the magnetic toner, the liberation rate of iron and iron compounds, the viscosity defined by the temperature, and the ratio of weight average particle diameter / number average particle diameter to achieve low-temperature fixability. Since the chargeability is stable without deteriorating the image quality, a high-quality image whose development / transferability does not change due to durability can be stably obtained.

The change in chargeability is, for example, a broadening of the charge amount distribution. As the charge amount distribution broadens, not only the magnetic toner having a low charge amount but also the toner particles charged to the opposite polarity increase. This magnetic toner is not transferred to the transfer material and cannot be confirmed on an image, but is not preferable in terms of toner consumption. Further, in the case of the cleaner-less image forming method according to the present invention, the load on the charging member is increased, which is not preferable.

The viscosity of the magnetic toner of the present invention measured by a flow tester can be measured by the following means.
Elevated flow tester (eg Shimadzu flow tester CF
T-500D), about 1.5 g of magnetic toner molded first using a pressure molding machine was applied with a load of 10 kgf (= 98 N) by a plunger at a constant temperature to a diameter of 1 m.
m, extrude from a 1 mm long nozzle, thereby lowering the plunger of the flow tester (outflow velocity)
Is measured. This outflow rate is set at each temperature (60 ° C to 180 ° C).
Temperature range at 5 ° C intervals), and from this value the viscosity η '
Is determined by the following equation.

[0117]

(Equation 4)

The magnetic toner of the present invention can also be produced by a pulverization method. When the magnetic toner is produced by a pulverization method, known methods are used. For example, a binder resin, a magnetic powder, a release agent, In some cases, components necessary as a magnetic toner such as a charge control agent and a colorant and other additives are sufficiently mixed by a mixer such as a Henschel mixer or a ball mill, and then a heat kneader such as a heating roll, a kneader or an extruder. Melt and knead with each other, disperse or dissolve other magnetic toner materials such as magnetic powder while the resins are mutually compatible, cool and solidify, pulverize, classify, and perform surface treatment if necessary To obtain toner particles. Either the classification or the surface treatment may be performed first. In the classification step, it is preferable to use a multi-divider classifier in terms of production efficiency.

The pulverizing step can be performed by a method using a known pulverizing apparatus such as a mechanical impact type or a jet type.
In order to obtain a magnetic toner having a specific degree of circularity according to the present invention, it is preferable to further apply heat to pulverize or to perform auxiliary mechanical impact. Further, a hot-water bath method in which finely pulverized (classified as necessary) toner particles are dispersed in hot water, a method in which the toner particles pass through a hot air flow, or the like may be used.

As a means for applying a mechanical impact force, for example, a method using a mechanical impact type pulverizer such as a Kryptron system manufactured by Kawasaki Heavy Industries and a turbo mill manufactured by Turbo Kogyo, a mechano-fusion system manufactured by Hosokawa Micron Corp. Like a device such as a hybridization system manufactured by Nara Machinery Co., Ltd., the toner particles are pressed against the inside of the casing by centrifugal force by a high-speed rotating blade, and a compressive force,
A method of applying a mechanical impact force to toner particles by a force such as a frictional force may be used.

In the case where the mechanical impact method is used, the processing temperature is set to a temperature near the glass transition point Tg of the toner particles (T
g ± 10 ° C.) is preferable from the viewpoint of prevention of aggregation and productivity. More preferably, it is carried out at a temperature in the range of the glass transition point Tg ± 5 ° C. of the toner particles,
It is particularly effective for improving the transfer efficiency.

When the magnetic toner according to the present invention is produced by a pulverization method, the binder resin may be, for example, a homopolymer of styrene such as polystyrene and polyvinyltoluene and a substituted product thereof; a styrene-propylene copolymer, and styrene-vinyltoluene. Copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-
Ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer,
Styrene-dimethylaminoethyl acrylate copolymer,
Styrene-methyl methacrylate copolymer, styrene-
Ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-dimethylaminoethyl methacrylate copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl Styrene-based copolymers such as methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer; polymethyl methacrylate, polybutyl Methacrylate, polyvinyl acetate, polyethylene, polypropylene, polyvinyl butyral, silicone resin, polyester resin, polyamide resin, epoxy resin, polyacrylic resin, rosin, modified rosin, tempel resin, phenolic resin, aliphatic or alicyclic carbonization Containing resins, aromatic petroleum resins, paraffin wax, and carnauba wax may be used alone or in combination. In particular, styrene-based copolymers and polyester resins are preferred in terms of development characteristics, fixability, and the like.

Glass transition temperature (Tg) of magnetic toner
Is preferably 40 to 80 ° C, more preferably 45 to 70 ° C. If the Tg is lower than 40 ° C., the storage stability of the magnetic toner tends to decrease, and if the Tg is higher than 80 ° C., the fixability may be poor. The glass transition point of the magnetic toner can be measured using, for example, a differential scanning calorimeter of a high precision internal heating type input compensation type such as DSC-7 manufactured by PerkinElmer. The measuring method at this time is ASTM
Performed according to D3418-8. In the present invention, a DSC curve measured when the sample is heated once to obtain a pre-history, rapidly cooled, and then heated again at a heating rate of 10 ° C./min and a temperature in the range of 30 to 200 ° C. is used. .

The magnetic toner according to the present invention can be obtained by atomizing a molten mixture into air using a disk or a multi-fluid nozzle described in JP-B-56-13945, etc. to obtain a spherical toner, Is an emulsion represented by a dispersion polymerization method in which a toner is directly produced using a water-soluble organic solvent in which a soluble polymer is insoluble or a soap-free polymerization method in which a toner is produced by directly polymerizing in the presence of a water-soluble polar polymerization initiator. Production can also be performed by a method of producing a toner using a polymerization method or the like.

The magnetic toner of the present invention can be produced by the pulverizing method as described above. However, the toner particles obtained by this pulverizing method are generally irregular in shape, and the magnetic toner of the present invention is of an irregular shape. In order to obtain the physical property that the average circularity is 0.970 or more, which is an essential requirement, it is necessary to perform a mechanical / thermal or some special treatment, and the productivity becomes poor.

Therefore, in the present invention, it is preferable that the toner particles are produced by a polymerization method, particularly, a suspension polymerization method. In this suspension polymerization method, a polymerizable monomer and a colorant (and, if necessary, a polymerization initiator, a crosslinking agent, a charge control agent, and other additives) are uniformly dissolved or dispersed to form a polymerizable monomer system. After that, the polymerizable monomer system is dispersed in a continuous layer (for example, an aqueous phase) containing a dispersion stabilizer by using a suitable stirrer, and simultaneously undergoes a polymerization reaction, thereby obtaining toner particles having a desired particle size. Is what you get.

The toner obtained by the suspension polymerization method (hereinafter referred to as “polymerized toner”) has an average circularity of 0.970 or more and a mode circularity of 0.99 or more since the individual toner particles are substantially spherical in shape. It is easy to obtain a magnetic toner that satisfies the physical properties essential for the present invention, and furthermore, such a magnetic toner has a relatively uniform distribution of the charge amount and thus has high transferability.

However, even when ordinary magnetic powder is contained in the polymerized toner, a large number of magnetic powders exist on the surface of the toner particles, and the charging characteristics of the toner particles are significantly reduced. Further, due to the strong interaction between the magnetic powder and water during the production of the suspension polymerization toner, it is difficult to obtain a magnetic toner having a circularity of 0.970 or more, and the particle size distribution of the magnetic toner becomes wider. .

This is because (1) the magnetic powder is generally hydrophilic and thus easily present on the surface of toner particles;
(2) It is considered that the reason is that the magnetic powder moves randomly when the aqueous solvent is stirred, and the surface of the suspended particles composed of the monomer is dragged by the magnetic powder, distorting the shape and making it difficult to form a circle. In order to solve these problems, it is important to modify the surface characteristics of the magnetic powder.

Many proposals have been made regarding the surface modification of magnetic powder used in polymerized toner. As described above, Japanese Patent Application Laid-Open Nos.
No. 0256, JP-A-59-200257,
JP-A-59-224102 proposes various silane coupling agent treatment techniques for magnetic powders. JP-A-63-250660 discloses that silicon-containing magnetic particles are treated with a silane coupling agent. Techniques are disclosed.

However, although the release of the magnetic powder is suppressed to some extent by these treatments, there is a problem that it is difficult to uniformly hydrophobize the surface of the magnetic powder. Inevitably, the generation of non-hydrophobic magnetic powder cannot be avoided, the dispersibility of the magnetic powder is not sufficient, and the particle size distribution becomes wide.

As an example of using hydrophobic magnetic iron oxide, Japanese Patent Application Laid-Open No. 54-84731 proposes a toner containing magnetic iron oxide treated with alkyl trialkoxysilane. Although the electrophotographic properties of the magnetic toner have certainly been improved by the addition of the magnetic iron oxide, the surface activity of the magnetic iron oxide is inherently low, and coalesced particles are formed at the processing stage and hydrophobicity is not reduced. Uniform or not always satisfactory.

Further, when a magnetic powder having a small particle size is used, uniform processing becomes more difficult, and further improvement is required for application to the present invention. Furthermore, when a large amount of a treating agent or the like is used to improve the encapsulation of the magnetic powder, or when a highly viscous treating agent is used, the degree of hydrophobicity is certainly increased, but coalescence of particles occurs. Therefore, the dispersibility deteriorates.

The magnetic toner produced using such a magnetic powder has non-uniform triboelectric charging properties, resulting in poor fog and poor transferability.

As described above, in the polymerized toner using the conventional surface-treated magnetic powder, compatibility between hydrophobicity and dispersibility is not necessarily achieved, and such a polymerized toner is subjected to the contact charging step of the present invention. Even when applied to an image forming method, it is difficult to stably obtain a high-definition image.

Therefore, the magnetic powder used in the magnetic toner of the present invention is preferably subjected to a uniform hydrophobic treatment with a coupling agent. When the surface of the magnetic powder is hydrophobized, it is very preferable to use a method in which the magnetic powder is dispersed in an aqueous medium so as to have a primary particle size, and the surface treatment is performed while hydrolyzing the coupling agent. In this hydrophobizing method, the magnetic powders are less likely to coalesce than in the gas phase, and the repelling action between the magnetic powders by the hydrophobizing process works, so that the magnetic powder is almost in the state of primary particles. Surface treated.

The method of treating the surface of the magnetic powder while hydrolyzing the coupling agent in an aqueous medium does not require the use of a coupling agent that generates a gas such as chlorosilanes or silazanes. In the gaseous phase, magnetic powders are easily united with each other, and a high-viscosity coupling agent, which has been difficult to treat well, can be used, and the effect of hydrophobization is enormous.

Examples of the coupling agent usable in the surface treatment of the magnetic powder used in the present invention include a silane coupling agent and a titanium coupling agent. More preferably used is a silane coupling agent, which is represented by the general formula (I).

## STR1 R _m SiY _n (I) [wherein, R represents an alkoxy group, m represents an integer of 1 to 3, Y is an alkyl group, vinyl group, glycidoxy group, hydrocarbon group such as methacrylic group And n represents an integer of 1 to 3. However, m + n = 4. ]

Examples of the silane coupling agent represented by the general formula (I) include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, and β- (3,4 epoxycyclohexyl) ethyltrisilane. Methoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane Methoxysilane, vinyltriacetoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane Diphenyl diethoxy silane, n- butyl trimethoxysilane, isobutyl trimethoxysilane, trimethyl methoxysilane, hydroxypropyl Ritori silane, n- hexadecyl trimethoxy silane, can be mentioned n- octadecyl trimethoxysilane.

Among these, it is particularly preferable to use an alkyltrialkoxysilane coupling agent represented by the following general formula (II) in combination.

Embedded image C _p H _{2p + 1} —Si— (OC _q H _{2q + 1} ) ₃ (II) wherein p represents an integer of 2 to 20, and q represents an integer of 1 to 3. ]

When p in the above formula is smaller than 2, the hydrophobic treatment becomes easy, but it is difficult to impart sufficient hydrophobicity, and the exposure or release of the magnetic powder from the toner particles is suppressed. Things get harder. When p is larger than 20, the hydrophobicity is sufficient, but the coalescence of the magnetic powders increases, and it becomes difficult to sufficiently disperse the magnetic powders in the toner particles, and fog and transferability are reduced. It tends to worsen.

When q is larger than 3, the reactivity of the silane coupling agent is reduced, and it is difficult to sufficiently perform the hydrophobic treatment. In particular, alkyltrialkoxysilane in which p in the formula represents an integer of 2 to 20 (more preferably, an integer of 3 to 15) and q represents an integer of 1 to 3 (more preferably, an integer of 1 or 2) It is good to use a coupling agent.

The amount of the above-mentioned coupling agent to be treated is such that the total amount of the silane coupling agent is 0.05 to 20 parts by mass, preferably 0.1 to 100 parts by mass of the magnetic powder.
The amount is preferably adjusted according to the surface area of the magnetic powder, the reactivity of the coupling agent, and the like.

In order to treat a magnetic powder with a coupling agent in an aqueous medium as a surface treatment, a method of stirring an appropriate amount of the magnetic powder and the coupling agent in the aqueous medium can be mentioned. The stirring is preferably performed sufficiently by a mixer having stirring blades so that the magnetic powder becomes primary particles in an aqueous medium.

Here, the aqueous medium is a medium containing water as a main component. Specifically, water itself as an aqueous medium, water with a small amount of a surfactant added,
Examples thereof include those in which a regulator is added and those in which an organic solvent is added to water. As the surfactant, a nonionic surfactant such as polyvinyl alcohol is preferable. The surfactant is preferably added in an amount of 0.1 to 5% by mass relative to water.
Examples of the pH adjusting agent include inorganic acids such as hydrochloric acid. Examples of the organic solvent include alcohols.

In the magnetic powder thus obtained, no aggregation of particles is observed, and the surface of each particle is uniformly subjected to a hydrophobic treatment. Therefore, when used as a material for polymerized toner, the uniformity of toner particles is good. It becomes something.

The magnetic powder used in the magnetic toner of the present invention may be, for example, triiron tetroxide, γ-iron oxide or the like which may contain elements such as phosphorus, cobalt, nickel, copper, magnesium, manganese, aluminum and silicon. And iron oxide as a main component, and these are used alone or in combination of two or more. These magnetic powders are BET by nitrogen adsorption method.
The specific surface area is preferably ² to 30 m ² / g, particularly preferably ³ to 28 m ² / g.
m ² / g is more preferred. Further, those having a Mohs hardness of 5 to 7 are preferable.

Examples of the shape of the magnetic powder include polyhedrons, octahedrons, hexahedrons, spheres, needles, and scaly shapes, and those having little anisotropy such as polyhedrons, octahedrons, hexahedrons, and spheres. It is preferable for increasing the image density. The shape of such a magnetic powder can be confirmed by SEM or the like.

The volume average particle diameter of the magnetic powder is 0.05
To 0.40 μm, more preferably 0.10 to
0.30 μm. When the volume average diameter is less than 0.05 μm, the decrease in blackness becomes remarkable, the coloring power of the black-and-white toner becomes insufficient, and the aggregation of the composite oxide particles becomes strong, so It tends to deteriorate. Further, it becomes difficult to perform a uniform surface treatment of the magnetic powder, and the release rate of iron and iron compounds increases. Further, when the particle size of the magnetic powder is smaller than 0.05 μm,
The magnetic powder itself becomes strongly reddish, and the resulting image also tends to be reddish black, which degrades image quality.

On the other hand, the volume average particle size of the magnetic powder was 0.40.
If it exceeds μm, the coloring power becomes insufficient as in the case of a general coloring agent. In addition, especially when used as a colorant for small particle size toners, it becomes probabilistically difficult to uniformly disperse magnetic powder in individual toner particles, dispersibility tends to deteriorate, and toner durability increases. May be inferior in some cases.

The volume average particle diameter of the magnetic powder can be measured using a transmission electron microscope. Specifically, after sufficiently dispersing the toner particles to be observed in the epoxy resin,
A cured product obtained by curing in an atmosphere at a temperature of 40 ° C. for 2 days is used as a sample on a slice by a microtome, and is shown in a transmission electron microscope (TEM) at a magnification of 10,000 to 40,000 times in a visual field. The particle diameter of 100 magnetic powders is measured. Then, the volume average particle size is calculated based on the equivalent diameter of a circle equal to the projected area of the magnetic powder. The same measurement was performed in Examples described later.

In the present invention, other coloring agents may be used in addition to the magnetic powder. Coloring agents that can be used in combination include magnetic or non-magnetic inorganic compounds, known dyes and pigments. Specifically, for example, cobalt, ferromagnetic metal particles such as nickel, or chromium, manganese, copper,
Examples include alloys containing zinc, aluminum, and rare earth elements, particles such as hematite, titanium black, nigrosine dye / pigment, carbon black, and phthalocyanine. These may also be used after treating the surface.

Further, the magnetic powder used in the present invention preferably has a volume average variation coefficient of 35 or less. The volume average variation coefficient of the magnetic powder is an index indicating the breadth of the particle size distribution of the magnetic powder. A volume average variation coefficient of more than 35 means that the particle size distribution of the magnetic powder is wide. When such a magnetic powder is used, the uniformity of the processing of the magnetic powder described above is poor, and the dispersibility in the toner tends to deteriorate. Further, it is difficult to uniformly enter the magnetic powder into each of the toner particles during granulation, and a large difference in the content of the magnetic powder among the toner particles is likely to occur. In the present invention, the volume average variation coefficient is defined to be obtained by the following equation.

[0154]

(Equation 5)

The degree of hydrophobicity of the magnetic powder used in the present invention is 35.
~ 95%, more preferably 40 ~
95%. The degree of hydrophobicity can be arbitrarily changed depending on the type and amount of the treating agent on the surface of the magnetic powder. The degree of hydrophobicity indicates the hydrophobicity of the magnetic powder, and a substance having a low degree of hydrophobicity means having a high degree of hydrophilicity.

Therefore, when a magnetic powder having a low degree of hydrophobicity is used, the suspension polymerization method suitably used in producing the magnetic toner of the present invention transfers the magnetic powder to an aqueous system during granulation. As a result, the particle size distribution becomes broad and the average circularity of the toner particles becomes low. This occurs because the magnetic powder that has not been sufficiently hydrophobized is likely to be exposed on the surface of the toner particles. Further, those having a low degree of hydrophobicity are not preferred because the release rate of iron and iron compounds increases. On the other hand, in order to increase the degree of hydrophobicity to more than 95%, it is necessary to use a large amount of a treatment material on the surface of the magnetic powder. May be impaired.

The degree of hydrophobicity in the present invention is measured by the following method. The degree of hydrophobicity of the magnetic powder is measured by a methanol titration test. The methanol titration test is an experimental test for confirming the degree of hydrophobicity of a magnetic powder having a hydrophobized surface.

The degree of hydrophobicity measurement using methanol is performed as follows. Add 0.1 g of the magnetic powder to 50 mL of water in a 250 mL beaker. Thereafter, methanol is gradually added to the liquid to perform titration. At this time, methanol is supplied from the bottom of the liquid, and the stirring is performed with gentle stirring. The end of the sedimentation of the magnetic powder is defined as the point at which no suspended matter of the magnetic powder is observed on the liquid surface.The degree of hydrophobicity is defined as the volume percentage of methanol in the mixture of methanol and water when the sedimentation end is reached. Will be revealed. The same measurement was performed in Examples described later.

The magnetic powder used in the magnetic toner of the present invention is preferably used in an amount of 10 to 200 parts by mass based on 100 parts by mass of the binder resin. More preferably, 20 to 1
It is preferable to use 80 parts by mass. If the amount is less than 10 parts by mass, the coloring power of the magnetic toner is poor, and it is difficult to suppress fog. On the other hand, when the amount exceeds 200 parts by mass, the magnetic force on the magnetic toner carrier increases the holding force and the developability is reduced. In addition, it becomes difficult to uniformly disperse the magnetic powder in individual toner particles, May decrease.

The content of the magnetic powder in the toner particles was measured by, for example, a thermal analyzer (trade name, manufactured by PerkinElmer Co., Ltd., TG).
It can be measured using A7. The measuring method is as follows.
The magnetic toner is heated to 100.degree. C., the weight loss between 100.degree. C. and 750.degree. C. is defined as the mass of the component obtained by removing the magnetic powder from the toner particles, and the remaining mass is defined as the amount of the magnetic powder.

The magnetic powder used for the magnetic toner of the present invention, for example, in the case of magnetite, is manufactured by the following method.

An aqueous solution of a ferrous salt is added with an equivalent or an equivalent or more of an alkali such as sodium hydroxide to the iron component,
An aqueous solution containing ferrous hydroxide is prepared. Air is blown in while maintaining the pH of the prepared aqueous solution at pH 7 or more (preferably pH 8 to 14), and while the aqueous solution is heated to 70 ° C. or more, the oxidation reaction of ferrous hydroxide is carried out. First, a seed crystal serving as a core is generated.

Next, an aqueous solution containing about 1 equivalent of ferrous sulfate based on the amount of the alkali previously added is added to the slurry-like liquid containing the seed crystals. The reaction of ferrous hydroxide is promoted while blowing air while maintaining the pH of the solution at 6 to 14, and the magnetic iron oxide powder is grown around the seed crystal. The pH of the solution shifts to the acidic side as the oxidation reaction proceeds, but it is preferable that the pH of the solution is not less than 6. At the end of the oxidation reaction, adjust the pH of the solution, stir well so that the magnetic iron oxide becomes primary particles, add a coupling agent, mix and stir well, filter, dry, and lightly disintegrate after stirring. By doing so, a magnetically treated magnetic iron oxide powder is obtained. Or, after the end of the oxidation reaction, the iron oxide powder obtained by washing and filtration is redispersed in another aqueous medium without drying, and then the pH of the redispersed liquid is adjusted, and the mixture is sufficiently stirred. A coupling treatment may be performed by adding a silane coupling agent.

As the ferrous salt, iron sulfate which is generally produced as a by-product in the production of titanium sulfate, iron sulfate which is produced as a result of cleaning the surface of a steel sheet, and iron chloride and the like can be used. is there.

The method for producing magnetic iron oxide by the aqueous solution method generally uses an iron concentration of 0.5 to 2 mol / L from the viewpoint of preventing an increase in viscosity during the reaction and the solubility of iron sulfate. Generally, the lower the concentration of iron sulfate, the smaller the particle size of the product tends to be. Also, in the reaction, as the amount of air is larger and the reaction temperature is lower, the atomization is more likely.

By using the magnetic toner made of the hydrophobic magnetic powder thus produced, stable toner charging properties can be obtained, high transfer efficiency, high image quality and high stability can be achieved. Becomes

The magnetic toner of the present invention has a magnetic field of 79.6 kA.
/ M (1000 Oe) saturation magnetization of the toner in is required to be a magnetic toner is ^{10~50Am 2 / kg (emu / g} ). This is because by providing a magnetic force generating means in the developing device, it is possible to prevent the leakage of the magnetic toner, not only to improve the transportability or agitation of the magnetic toner, but also to make the magnetic force act on the magnetic toner carrier. By providing the magnetic force generating means, the recoverability of the transfer residual toner is further improved, and the magnetic toner forms spikes, thereby making it easy to prevent the toner from scattering.

However, the magnetic field of the magnetic toner was 79.6 kA /
If the magnetization intensity at m is less than 10 Am ² / kg, the above effects cannot be obtained, and when a magnetic force is applied to the magnetic toner carrier, the magnetic toner becomes unstable and the magnetic toner is charged. Image defects such as fogging, image density unevenness, and insufficient transfer of untransferred toner due to non-uniform application tend to occur.

On the other hand, the magnetic field of the magnetic toner was 79.6 kA / m
If the magnetization strength is larger than 50 Am ² / kg, when a magnetic force is applied to the magnetic toner, the magnetic toner significantly lowers its fluidity due to magnetic aggregation and developability is reduced, and the magnetic toner is easily damaged. , Toner deterioration becomes remarkable. Also, due to the magnetic aggregation of the magnetic toner,
The durability under high temperature and high humidity is inferior. Further, the transferability is also undesirably reduced due to a decrease in transfer residual toner.

Further, a developing and cleaning step, or
When used in an image forming method of a cleanerless system, the residual magnetization of the magnetic toner in a magnetic field of 79.6 kA / m (1000 Oe) is 0.5 to 6 Am.
^The magnetic toner is preferably ² / kg (emu / g). When the residual magnetization exceeds 6 Am ² / kg, the transfer residual toner magnetically aggregates and easily acts as an aggregate of the toner, and the photosensitive member surface is damaged by being rubbed between the charging member and the photosensitive member. This is not preferred. On the other hand, when the residual magnetization is less than 0.5 Am ² / kg, the transfer residual toner is liable to exist in a state of being scattered in each particle, and is difficult to be captured by the charging member, and as a result, it is difficult to be charged normally. It is not preferable because it may be lost. That is, since the magnetic toner has a preferable residual magnetization, the transfer residual toner is present in an appropriately aggregated state, so that the toner can be properly formed without damaging the photoconductor.

The intensity of magnetization (saturation magnetization, residual magnetization) of the magnetic toner can be arbitrarily changed depending on the amount of magnetic powder contained, the saturation magnetization and residual magnetization of the magnetic powder.

The saturation magnetization of the magnetic powder is 796 kM.
30 to 120 Am at A / m ^Two/ Kg
Is preferred.

In the present invention, the intensity of the saturation magnetization and the residual magnetization of the magnetic toner can be measured, for example, by using a vibration type magnetometer VSM P-1.
-10 (manufactured by Toei Kogyo Co., Ltd.). In the case of using the above device, measurement is performed at room temperature of 25 ° C. with an external magnetic field of 79.6 kA / m. Further, regarding the magnetic properties of the magnetic powder, the vibration type magnetometer VSM P-1-1
0 (manufactured by Toei Kogyo Co., Ltd.) at 25 ° C. and an external magnetic field of 796 kA / m.

The magnetic toner of the present invention contains a release agent for improving the fixability. The magnetic toner of the present invention contains the release agent in a total amount of 1 to 30% by mass based on the binder resin. Is preferred. More preferably, it is 3 to 25% by mass.
When the content of the release agent is less than 1% by mass, the effect of adding the release agent is not sufficient, and the effect of suppressing the offset is also insufficient. On the other hand, if it exceeds 30% by mass, the long-term storability deteriorates, the dispersibility of the magnetic toner material such as the release agent and the magnetic powder deteriorates, and the fluidity of the magnetic toner deteriorates and the image characteristics deteriorate. Leads to a decline. In addition, the release agent component also exudes, and the durability under high temperature and high humidity tends to be poor. Furthermore, in order to include a large amount of wax,
The shape of the magnetic toner tends to be distorted.

Generally, the toner image transferred onto the recording medium is thereafter fixed on the transfer material by energy such as heat and pressure, and a semi-permanent image is obtained. At this time, a hot roll type fixing is generally often used. As described above, a very high-definition image can be obtained by using a magnetic toner having a weight average particle diameter of 20 μm or less. The fibers enter the gaps between the fibers and receive insufficient heat from the heat fixing roller, so that low-temperature offset is likely to occur. However, in the magnetic toner of the present invention, it is possible to achieve both high image quality and fixability by including an appropriate amount of a release agent and controlling the release rate of iron and iron compounds as described above. Become.

The release agents usable in the magnetic toner of the present invention include petroleum waxes such as paraffin wax, microcrystalline wax and petrolactam and derivatives thereof, montan wax and derivatives thereof, and hydrocarbon waxes prepared by the Fischer-Tropsch method. Its derivatives,
Polyolefin wax represented by polyethylene and its derivatives, natural wax such as carnauba wax and candelilla wax and its derivatives, etc. The derivatives include oxides, block copolymers with vinyl monomers, and graft modified products. Furthermore, fatty acids such as higher aliphatic alcohols, stearic acid and palmitic acid, or compounds thereof, acid amide waxes, ester waxes, ketones, hydrogenated castor oil and derivatives thereof, vegetable waxes, animal waxes and the like can also be used.

Among these release agent components, those having an endothermic peak of 40 to 110 ° C. by differential thermal analysis, that is, a region of 40 to 110 ° C. at the time of temperature rise in a DSC curve measured by a differential scanning calorimeter. Those having a maximum endothermic peak are more preferable, and those having a maximum endothermic peak in the range of 50 to 100 ° C are more preferable. By having the maximum endothermic peak in the above temperature range, it greatly contributes to low-temperature fixing, and also effectively expresses the releasability.

When the maximum endothermic peak is less than 40 ° C., the self-cohesive force of the release agent component becomes weak, and as a result, the high-temperature offset resistance tends to deteriorate. In addition, exudation of the release agent is likely to occur, and the charge amount of the toner is reduced.
The durability under high temperature and high humidity tends to decrease. On the other hand, if the maximum endothermic peak exceeds 110 ° C., the fixing temperature becomes high, and low-temperature offset tends to occur, which is not preferable. Further, when the toner is directly obtained by a polymerization method by performing granulation / polymerization in an aqueous medium, if the maximum endothermic peak temperature is high,
Problems such as precipitation of the release agent component mainly occur during granulation, and the dispersibility of the release agent deteriorates, which is not preferable.

The endothermic amount and the maximum endothermic peak temperature of the release agent are measured according to “ASTM D3418-8”. For the measurement, for example, DSC- manufactured by PerkinElmer Co., Ltd.
7 is used. The temperature correction of the device detection unit uses the melting points of indium and zinc, and the heat quantity correction uses the heat of fusion of indium. An aluminum pan was used for the measurement sample, an empty pan was set as a control, and the sample was once heated to 200 ° C.
After removing the heat history by heating to a temperature of up to 10 ° C./min, a DSC curve measured when the temperature is raised in a temperature range of 30 to 200 ° C. again at a rate of 10 ° C./min is used. The same measurement was performed in Examples described later.

The magnetic toner of the present invention has a TH of magnetic toner.
In the molecular weight distribution measured by gel permeation chromatography (GPC) of the F-soluble component, the main peak preferably has a peak top in the molecular weight range of 5,000 to 50,000, more preferably 8,000 to 8,000.
It is in the range of 40000. If the peak top is less than 5000, there is a problem in the storage stability of the toner, and the toner tends to deteriorate significantly when a large number of printouts are performed. Conversely, when the peak top exceeds 50,000, a problem occurs in low-temperature fixability,
Due to a rapid increase in the viscosity of the droplet during polymerization, it may be difficult to make the average circularity of the toner 0.970 or more.

The measurement of the molecular weight of the resin component soluble in THF by GPC may be performed as follows. A solution obtained by dissolving the magnetic toner of the present invention in THF at room temperature for 24 hours is filtered through a solvent-resistant membrane filter having a pore diameter of 0.2 μm to obtain a sample solution, which is measured under the following conditions. In the preparation of the sample, the amount of THF is adjusted so that the concentration of the component soluble in THF is 0.4 to 0.6% by mass. Apparatus: High-speed GPC HLC8120 GPC (manufactured by Tosoh Corporation) Column: Shodex KF-801, 802, 80
7, 804, 805, 806, 807 (Showa Denko KK) Eluent: THF Flow rate: 1.0 ml / min Oven temperature: 40.0 ° C. Sample injection amount: 0.10 ml

In calculating the molecular weight of the sample,
Standard polystyrene resin (Tosoh Corporation TSK Standard Polystyrene F-850, F-450, F-28
8, F-128, F-80, F-40, F-20, F-
10, F-4, F-2, F-1, A-5000, A-2
500, A-1000, A-500).

The molecular weight of the magnetic toner can be arbitrarily changed depending on the binder resin to be used and the kneading conditions when the magnetic toner is produced by the pulverization method. In addition, in the polymerization method, it can be arbitrarily changed depending on the combination of the type and amount of the initiator and the crosslinking agent to be used. The adjustment can also be made by using a chain transfer agent or the like.

The magnetic toner of the present invention may contain a charge control agent for stabilizing the charge characteristics. As the charge control agent, a known charge control agent can be used. In particular, a charge control agent having a high charging speed and capable of stably maintaining a constant charge amount is preferable. Further, when the magnetic toner is produced by a direct polymerization method, a charge control agent having a low polymerization inhibitory property and having substantially no solubilized substance in an aqueous dispersion medium is particularly preferable.

Specific examples of the compound include a metal compound of an aromatic carboxylic acid such as salicylic acid, alkylsalicylic acid, dialkylsalicylic acid, naphthoic acid and dicarboxylic acid, a metal salt or metal salt of an azo dye or azo pigment as a negative charge control agent. Complex, a high molecular compound having a sulfonic acid or carboxylic acid group in a side chain, a boron compound, a urea compound,
Silicon compounds, calixarenes and the like can be mentioned. Examples of the positive charge control agent include a quaternary ammonium salt, a high molecular compound having the quaternary ammonium salt in a side chain, a guanidine compound, a nigrosine compound, and an imidazole compound.

As a method of incorporating the charge control agent into the toner, there are a method of adding the charge control agent inside the toner particles and a method of adding the charge control agent to the toner particles. The amount of these charge control agents used is determined by the method of manufacturing the magnetic toner including the type of the binder resin, the presence or absence of other additives, and the dispersion method,
Although it is not limited uniquely, when it is added internally, preferably 0.1 to 100 parts by mass of the binder resin.
It is used in an amount of 10 parts by mass, more preferably 0.1 to 5 parts by mass. In the case of external addition, the toner particles 10
The amount is preferably 0.005 to 1.0 part by mass, more preferably 0.01 to 0.3 part by mass with respect to 0 part by mass.

However, in the magnetic toner of the present invention, the addition of a charge control agent is not essential, and the charging process in the image forming process such as friction charging between the toner layer pressure regulating member and the magnetic toner carrier is actively used. By doing so, it is not always necessary to include a charge control agent in the magnetic toner.

Next, a method for producing a polymerized toner according to the present invention by a suspension polymerization method will be described. The polymerized toner according to the present invention generally contains a magnetic powder, a release agent, a plasticizer, a charge control agent, a cross-linking agent, a coloring agent, and the like in a toner composition, that is, a polymerizable monomer serving as a binder resin. Components necessary for the toner and other additives, for example, a polymer, a dispersant and the like are appropriately added, and a polymerizable monomer system uniformly dissolved or dispersed by a disperser or the like is used as a dispersion stabilizer. It can be manufactured by suspending in a contained aqueous medium.

In the production of the polymerized toner according to the present invention, the polymerizable monomers constituting the polymerizable monomer system include the following.

Examples of the polymerizable monomer include styrene monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, p-ethylstyrene, methyl acrylate, and acrylic. Ethyl acrylate, n-butyl acrylate, isobutyl acrylate, n-propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate and the like Acrylic esters, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, methacryl Phenyl, dimethylaminoethyl methacrylate, methacrylic acid esters other acrylonitrile such as diethylaminoethyl methacrylate,
Monomers such as methacrylonitrile and acrylamide are exemplified. These monomers can be used alone or as a mixture. Among the above-mentioned monomers, it is preferable to use styrene or a styrene derivative alone or in a mixture with another monomer from the viewpoint of the developing characteristics and durability of the toner.

In the production of the polymerized toner according to the present invention, polymerization may be carried out by adding a resin to the polymerizable monomer system.
For example, a monomer contains a hydrophilic functional group such as an amino group, a carboxylic acid group, a hydroxyl group, a sulfonic acid group, a glycidyl group, and a nitrile group that cannot be used because it dissolves in an aqueous suspension to cause emulsion polymerization due to water solubility. When it is desired to introduce the polymerizable monomer component into the toner particles, a random copolymer, a block copolymer, or a graft copolymer of these and a vinyl compound such as styrene or ethylene is formed into a copolymer. Or a polycondensate such as polyester or polyamide;
It can be used in the form of polyaddition polymers such as polyethers and polyimines. When such a high molecular polymer containing a polar functional group is coexisted in the toner particles, the above-mentioned wax component is phase-separated, the encapsulation becomes stronger, and a magnetic toner having good blocking resistance and developability can be obtained. it can.

[0192] Among these resins, when a polyester resin is contained in particular, the effect becomes great. This is for the following reason. Since the polyester resin contains many ester bonds, which are relatively polar functional groups, the polarity of the resin itself increases. Because of its polarity,
In the aqueous dispersion medium, the polyester tends to be unevenly distributed on the surface of the liquid droplets, and the polymerization proceeds while maintaining the state to become toner particles. Therefore, the uneven distribution of the polyester resin on the surface of the toner particles results in a uniform surface state and a uniform surface composition. As a result, the chargeability is uniform and the encapsulating property of the release agent is good. With this, very good developability can be obtained.

The polyester resin used in the present invention includes:
For example, in controlling the physical properties such as chargeability, durability and fixability of the magnetic toner, a saturated polyester resin,
It is possible to select and use an unsaturated polyester resin or both appropriately. As the polyester resin used in the present invention, a general resin composed of an alcohol component and an acid component can be used, and both components are exemplified below.

Examples of the alcohol component include ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, diethylene glycol, triethylene glycol,
1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 2-ethyl-1,3-hexanediol, cyclohexanedimethanol, butenediol, octenediol, cyclohexenedimethanol, hydrogenated bisphenol A, and a compound represented by the formula A bisphenol derivative represented by the formula (I); a hydrogenated product of the compound of the formula (I); a diol represented by the formula (II); or a diol of a hydrogenated product of the compound of the formula (II).

[0195]

Embedded image [Wherein, R is an ethylene or propylene group, and x,
y is an integer of 1 or more, respectively, and the average value of x + y is 2 to 10. ]

Embedded image

Examples of the divalent carboxylic acid include benzenedicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid, and phthalic anhydride or anhydrides thereof; alkyl dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and azelaic acid; Anhydrides and succinic acids or anhydrides further substituted with an alkyl or alkenyl group having 6 to 18 carbon atoms; fumaric acid, maleic acid, citraconic acid,
And unsaturated dicarboxylic acids such as itaconic acid or anhydrides thereof.

Further, glycerin, pentaerythritol, sorbit, sorbitan,
Polyhydric alcohols such as oxyalkylene ethers of novolak type phenol resins are mentioned, and as an acid component, trimellitic acid, pyromellitic acid, 1,2,3,4-butanetetracarboxylic acid, benzophenonetetracarboxylic acid and anhydrides thereof Polycarboxylic acid.

Among the above polyester resins, the above-mentioned alkylene oxide adduct of bisphenol A, which is excellent in charging characteristics and environmental stability and is well balanced in other electrophotographic characteristics, is preferably used. In the case of this compound, the average addition mole number of the alkylene oxide is preferably 2 to 10 from the viewpoint of the fixing property and the durability of the magnetic toner.

In the polyester resin used in the present invention, 45 to 55 mol% of all components are alcohol components.
Preferably, ~ 45 mol% is the acid component.

The polyester resin is present on the surface of the toner particles in the method for producing a magnetic toner of the present invention.
It preferably has an acid value of 1 to 50 mg KOH / g of resin. If the amount is less than 0.1 mg KOH / g of resin, the amount present on the toner surface tends to be absolutely insufficient.
If it exceeds mgKOH / g of resin, the chargeability of the toner may be adversely affected. Furthermore, in the present invention, 5-35 m
An acid value range of gKOH / g of resin is more preferred.

In the present invention, physical properties are prepared by using two or more polyester resins in combination, or by modifying with, for example, a silicone or a fluoroalkyl group-containing compound as long as the physical properties of the obtained toner particles are not adversely affected. This is also preferably performed.

When a polymer having such a polar functional group is used, the average molecular weight is preferably 5,000 or more. 5,000 or less, especially 4,0
If it is less than 00, the present polymer tends to concentrate near the surface, so that adverse effects on developability, blocking resistance and the like are likely to occur, which is not preferable.

Further, a resin other than the above may be added to the monomer system for the purpose of improving the dispersibility and fixing property of the material, or the image characteristics, and the like.
Styrene such as polystyrene and polyvinyltoluene and its substituted homopolymer; styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene- Ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-dimethylaminoethyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-methacrylic Acid ethyl copolymer,
Styrene-butyl methacrylate copolymer, styrene-
Dimethylaminoethyl methacrylate copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-
Isoprene copolymer, styrene-maleic acid copolymer,
Styrene-based copolymers such as styrene-maleic acid ester copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyethylene, polypropylene, polyvinyl butyral, silicone resin, polyester resin, polyamide resin, epoxy resin, polyacrylic acid Resin, rosin, modified rosin, temper resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin and the like can be used alone or in combination. The addition amount of these resins is preferably 1 to 20 parts by mass based on 100 parts by mass of the polymerizable monomer. If the amount is less than 1 part by mass, the effect of addition is small, while if it is more than 20 parts by mass, it becomes difficult to design various physical properties of the polymerized toner.

Further, if a polymer having a molecular weight different from the molecular weight range of the toner particles obtained by polymerizing the polymerizable monomer is dissolved in the monomer and polymerized, a wide molecular weight distribution and offset resistance can be obtained. High magnetic toner can be obtained.

As the polymerization initiator used in the production of the polymerized toner related to the magnetic toner of the present invention, one having a half-life of 0.5 to 30 hours at the time of the polymerization reaction may be added to the polymerizable monomer in an amount of 0.5 to 30 hours. When the polymerization reaction is performed with an addition amount of 20 parts by mass, a polymer having a peak top of a main peak in a molecular weight of 5,000 to 50,000 in GPC can be obtained.

As the polymerization initiator used in the present invention,
There are conventionally known azo-based polymerization initiators and peroxide-based polymerization initiators. Examples of the azo-based polymerization initiator include 2,2′-azobis- (2,4-dimethylvaleronitrile) and 2,2 ′.
-Azobisisobutyronitrile, 1,1'-azobis (cyclohexane-1-carbonitrile), 2,2'-
Examples include azobis-4-methoxy-2,4-dimethylvaleronitrile, azobisisobutyronitrile, and the like. Examples of the peroxide-based polymerization initiator are t-butylperoxyacetate, t-butylperoxylaurate, and t-butylperoxylaurate. -Butyl peroxypivalate, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxyisobutyrate, t-butyl peroxy neodecanoate, t-hexyl peroxy acetate, t-hexyl par Oxylaurate, t-hexylperoxypivalate, t-hexylperoxy-2-ethylhexanoate, t-hexylperoxyisobutyrate, t-hexylperoxyneodecanoate, t-butylperoxybenzoate , Α, α'-bis (neodecanoylperoxy) diisopropylbenzene , Cumyl peroxy neodecanoate, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, 1,1,3,3-tetramethylbutyl peroxy neodecanoate, 1- Cyclohexyl-1-methylethylperoxy neodecanoate, 2,5-dimethyl-2,5-bis (2-ethylhexanoylperoxy) hexane, 1-cyclohexyl-
1-methylethylperoxy-2-ethylhexanoate, t-hexylperoxyisopropyl monocarbonate, t-butylperoxyisopropyl monocarbonate, t-butylperoxy-2-ethylhexyl monocarbonate, t-hexylperoxybenzoate,
2,5-dimethyl-2,5-bis (benzoylperoxy) hexane, t-butylperoxy-m-toluoylbenzoate, bis (t-butylperoxy) isophthalate, t-butylperoxymaleic acid, t
Peroxyesters such as -butylperoxy-3,5,5-trimethylhexanoate, 2,5-dimethyl-2,5-bis (m-toluoylperoxy) hexane;
Benzoyl peroxide, lauroyl peroxide, diacyl peroxide such as isobutyryl peroxide, diisopropyl peroxydicarbonate,
Peroxydicarbonates such as bis (4-t-butylcyclohexyl) peroxydicarbonate;
-Di-t-butylperoxycyclohexane, 1,1-
Di-t-hexylperoxycyclohexane, 1,1-
Peroxyketals such as di-t-butylperoxy-3,3,5-trimethylcyclohexane, 2,2-di-t-butylperoxybutane, di-t-butyl peroxide, dicumyl peroxide, t- Examples thereof include dialkyl peroxides such as butylcumyl peroxide, t-butylperoxyallyl monocarbonate, and the like. Two or more of these initiators can be used as needed.

When the magnetic toner of the present invention is produced by a polymerization method, it is important to adjust the melt viscosity by adding a crosslinking agent together with the above initiator in order to obtain a desired melt viscosity. As the crosslinking agent used in the present invention, a compound having two or more polymerizable double bonds is mainly used, for example, an aromatic divinyl compound such as divinylbenzene, divinylnaphthalene and the like; for example, ethylene glycol diacrylate Carboxylic acid esters having two double bonds, such as ethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate; divinylaniline, divinyl ether, divinyl sulfide,
A divinyl compound such as divinyl sulfone; and a compound having three or more vinyl groups are used alone or as a mixture. The addition amount needs to be adjusted depending on the type of the initiator and the cross-linking agent to be used and the reaction conditions. However, generally, 0.01 to 5 parts by mass is appropriate for the polymerizable monomer.

In the method for producing the magnetic toner of the present invention by a polymerization method, generally, the above-described toner composition such as the magnetic powder, polymerizable monomer, and release agent is appropriately added, and a homogenizer, a ball mill, and a colloid mill are added. The polymerizable monomer system uniformly dissolved or dispersed by a disperser such as an ultrasonic disperser is suspended in an aqueous medium containing a dispersion stabilizer. At this time, it is better to use a high-speed disperser such as a high-speed stirrer or an ultrasonic disperser to make the desired toner particle size at once.
The particle size of the obtained toner particles becomes sharp. As for the timing of the addition of the polymerization initiator, it may be added at the same time as the other additives are added to the polymerizable monomer, or may be mixed immediately before being suspended in the aqueous medium. Further, during or immediately after granulation, a polymerization initiator dissolved in a polymerizable monomer or a solvent can be added before starting the polymerization reaction.

After the granulation, stirring may be performed using an ordinary stirrer to such an extent that the particle state is maintained and the floating and settling of the particles are prevented.

When the magnetic toner of the present invention is produced by a polymerization method, known surfactants, organic dispersants and inorganic dispersants can be used as dispersion stabilizers. Above all, inorganic dispersants are unlikely to generate harmful ultrafine powder, and because of their steric hindrance, they have obtained dispersion stability, so that they do not easily lose stability even when the reaction temperature is changed, are easy to wash, and do not adversely affect the toner. Therefore, it can be preferably used. Examples of such inorganic dispersants include:
Polyvalent metal salts of phosphoric acid such as calcium phosphate, magnesium phosphate, aluminum phosphate and zinc phosphate; carbonates such as calcium carbonate and magnesium carbonate; inorganic salts such as calcium metasilicate, calcium sulfate and barium sulfate; calcium hydroxide; Examples include inorganic oxides such as magnesium, aluminum hydroxide, silica, bentonite, and alumina.

When these inorganic dispersants are used, they may be used as they are, but in order to obtain finer particles, it is preferable to use the inorganic dispersant particles formed in an aqueous medium. For example, in the case of calcium phosphate, a water-insoluble calcium phosphate can be produced by mixing an aqueous solution of sodium phosphate and an aqueous solution of calcium chloride under high-speed stirring, and more uniform and fine dispersion can be achieved. At this time,
At the same time, a water-soluble sodium chloride salt is produced as a by-product, but when the water-soluble salt is present in the aqueous medium, the dissolution of the polymerizable monomer in water is suppressed, and it is difficult to generate an ultrafine toner due to emulsion polymerization. It is more convenient. The inorganic dispersant can be almost completely removed by dissolving with an acid or alkali after completion of the polymerization.

It is preferable that these inorganic dispersants are used alone in an amount of 0.2 to 20 parts by mass with respect to 100 parts by mass of the polymerizable monomer. Since atomization may be somewhat insufficient, a surfactant of 0.001 to 0.1 part by mass may be used in combination.

Examples of the surfactant include sodium dodecylbenzene sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, sodium oleate, sodium laurate,
Examples thereof include sodium stearate and potassium stearate.

In the above polymerization step, the polymerization temperature was 40
The polymerization is carried out at a temperature of at least 50 ° C., generally from 50 to 90 ° C. When the polymerization is carried out in this temperature range, the release agent and waxes to be sealed inside are precipitated by phase separation, and the encapsulation becomes more complete. In order to consume the remaining polymerizable monomer, the reaction temperature should be 90 to 15 at the end of the polymerization reaction.
It is possible to increase to 0 ° C.

After the polymerization, the polymerization toner particles are filtered, washed and dried by known methods, and if necessary, mixed with inorganic fine powder and adhered to the surface, whereby the magnetic toner of the present invention can be obtained. In addition, it is also a desirable embodiment of the present invention to insert a classifying step into the manufacturing process and cut coarse or fine powder.

In a preferred embodiment of the present invention, the magnetic toner further comprises an inorganic fine powder having a number average primary particle size of 4 to 80 nm as a fluidizing agent. The inorganic fine powder is added to improve the fluidity of the magnetic toner and to make the toner particles uniform in charge. However, by adjusting the inorganic fine powder to a hydrophobic treatment, the charge amount of the magnetic toner is adjusted, and the environmental stability is improved. It is also a preferable embodiment to provide functions such as improvement.

The number average primary particle diameter of the inorganic fine powder is 80 nm
If the toner particles are larger than 80 nm or no inorganic fine powder having a size of 80 nm or less is added, the transfer residual toner easily adheres to the charging member when it adheres to the charging member, and obtains stable and good charging characteristics. Is difficult. Further, good fluidity of the magnetic toner cannot be obtained, and the charging of the toner particles tends to be non-uniform, so that problems such as an increase in fog, a decrease in image density, and toner scattering may not be avoided. When the number average primary particle size of the inorganic fine powder is smaller than 4 nm,
Agglomeration of inorganic fine powder is strengthened, and it is easy to behave as agglomerates with a wide particle size distribution with strong agglomeration that is not easy to disintegrate even by crushing treatment instead of primary particles, development of agglomerates, image carrier or magnetic toner carrier Image defects such as scratching the image. In order to make the charge distribution of the toner particles more uniform, the number average primary particle size of the inorganic fine powder is 6 to 35 n.
m is better.

In the present invention, the number-average primary particle size of the inorganic fine powder is measured by using a photograph of a magnetic toner enlarged by a scanning electron microscope and further using an elemental analysis means such as XMA attached to the scanning electron microscope. While contrasting the photograph of the magnetic toner mapped with the element contained in the inorganic fine powder, 100 or more primary particles of the inorganic fine powder attached or separated on the toner particle surface were measured, and the number-based It can be measured by obtaining the average primary particle size and the number average primary particle size.

The inorganic fine powder used in the present invention includes:
Silica, titanium oxide, alumina and the like can be used, and they may be used alone or in combination of two or more. As the silica, for example, both a so-called dry method produced by a vapor phase oxidation of a silicon halide or a dry silica called a fumed silica, and a so-called wet silica produced from water glass or the like can be used. Low silanol groups on the surface and inside the silica fine powder.
a ₂ O, towards less dry silica of manufacture residues of SO ₃ ^2-like. In the case of fumed silica, it is also possible to obtain a composite fine powder of silica and another metal oxide by using another metal halide such as aluminum chloride and titanium chloride together with a silicon halide in the production process. Is also included.

The addition amount of the inorganic fine powder having a number average primary particle size of 4 to 80 nm is preferably 0.1 to 3.0% by mass, and the addition amount is less than 0.1% by mass based on the toner particles. In this case, the effect is not sufficient, and when the content is 3.0% by mass or more, the fixing property tends to be deteriorated.

[0221] The content of the inorganic fine powder can be quantified by X-ray fluorescence analysis using a calibration curve prepared from a standard sample.

In the present invention, the inorganic fine powder is preferably subjected to a hydrophobizing treatment in view of characteristics under a high temperature and high humidity environment. When the inorganic fine powder added to the magnetic toner absorbs moisture, the charge amount of the toner particles is significantly reduced, and the toner is easily scattered.

Examples of the treating agent used in the hydrophobic treatment include silicone varnish, various modified silicone varnishes, silicone oil, various modified silicone oils, silane compounds, silane coupling agents, and other treating agents such as organosilicon compounds and organotitanium compounds. The treatment may be performed alone or in combination.

Among them, those treated with silicone oil are preferred, and those treated with silicone oil at the same time as the hydrophobization treatment of the inorganic fine powder with the silane compound, or after the treatment, can be used even in a high humidity environment. This is good for keeping the charge amount of the particles high and preventing toner scattering.

As a method for treating such an inorganic fine powder, for example, as a first step reaction, a silylation reaction is carried out with a silane compound to eliminate silanol groups by a chemical bond, and then, as a second step reaction, the surface is treated with silicone oil. A method of forming a hydrophobic thin film on the surface of the substrate can be exemplified.

The silicone oil has a viscosity at 25 ° C. of 10 to 200,000 mm ² / s, and more preferably 3,000 to 80,000 mm ² / s. If it is less than 10 mm ² / s, the inorganic fine powder has no stability, and the image quality tends to deteriorate due to heat and mechanical stress. If it exceeds 200,000 mm ² / s,
Uniform processing tends to be difficult.

As the silicone oil used, for example, dimethyl silicone oil, methylphenyl silicone oil, α-methylstyrene-modified silicone oil, chlorophenyl silicone oil, fluorine-modified silicone oil and the like are particularly preferable.

As a method of treating the inorganic fine powder with silicone oil, for example, the inorganic fine powder treated with the silane compound and the silicone oil may be directly mixed using a mixer such as a Henschel mixer, A method of spraying silicone oil on fine powder may be used. Alternatively, a method of dissolving or dispersing silicone oil in an appropriate solvent, adding an inorganic fine powder, mixing and removing the solvent may be employed. A method using a sprayer is more preferable because the formation of aggregates of the inorganic fine powder is relatively small.

The treatment amount of the silicone oil is 1 to 40 parts by mass, preferably 3 to 3 parts by mass, per 100 parts by mass of the inorganic fine powder.
5 parts by mass is good. If the amount of the silicone oil is too small, good hydrophobicity cannot be obtained, and if the amount is too large, problems such as fogging tend to occur.

[0230] The inorganic fine powder used in the present invention is preferably silica, alumina or titanium oxide in order to impart good fluidity to the magnetic toner, and among them, silica is particularly preferable. Furthermore, the specific surface area of the silica measured by the BET method by nitrogen adsorption of preferably those in 20~350m ² / g range, more preferably 25~300m ² /
g is even better.

The specific surface area of the inorganic fine powder is measured according to the BET method, for example, by adsorbing nitrogen gas on the sample surface using a specific surface area measuring device Autosorb 1 (manufactured by Yuasa Ionics) and using the BET multipoint method. , Can be calculated.

In the present invention, when silica is used as the inorganic fine powder, the release rate of silica is from 0.1% to 2.0%.
And more preferably 0.1% to 1.50%. The release rate of silica can be measured by the aforementioned particle analyzer, and the release rate of silica can be determined by the following equation.

(Equation 6)

As a specific measuring method, channel 1
Is a carbon atom, and a channel 2 is a silicon atom (measurement wavelength 28
8.160 nm, K factor uses recommended values).

The inventors of the present invention have studied and found that if the liberation rate of silica is less than 0.1%, fog increases and roughness tends to occur in the latter half of the multiple-sheet printing test, especially under high temperature and high humidity. . In general, in a high-temperature environment, embedding of an external additive tends to occur due to stress of a regulating member or the like, and after printing a large number of sheets, the fluidity of the magnetic toner becomes inferior to the initial state, and the above problem occurs. Conceivable. However, if the release rate of silica is 0.1% or more, such a problem hardly occurs. This is because if the silica is present in a certain free state, the fluidity of the toner becomes good, so that the embedding due to durability becomes difficult to occur, and even if the silica adhering to the toner particles due to stress occurs, It is considered that the free silica adheres to the surface of the toner particles so that the decrease in the fluidity of the magnetic toner is reduced.

On the other hand, if the liberation rate of silica is more than 2.00%, the free silica contaminates the charge control member, and undesirably increases fog. Further, in such a state, the charging uniformity of the magnetic toner is impaired, and the transfer efficiency is reduced.
For this reason, it is important that the release rate of silica is 0.1% to 2.0%.

Preferably, the magnetic toner of the present invention further comprises a conductive fine powder having a volume average particle diameter smaller than the weight average particle diameter of the magnetic toner. It is more preferable to have a conductive fine powder having a larger volume average particle diameter than the weight average particle diameter of the magnetic toner. This is because the developing property of the magnetic toner is improved by having the conductive fine powder, and a high image density can be obtained. Also,
When the release rate of the conductive fine powder is 5.0% to 50.0%, the effect becomes remarkable.

Although the reason is not clear, the presence of the free conductive fine powder together with the free magnetic powder suppresses the charge-up of the magnetic toner and makes the charging of the toner particles more uniform. We believe that this will improve developability. Furthermore, it is considered that the conductive fine powder attached to the toner particles behaves like a microcarrier, so that the developability is improved. Therefore, if the release rate of the conductive fine powder is less than 5.0%, this effect cannot be sufficiently obtained. On the other hand, if the release rate of the conductive fine powder is more than 50.0%, the uniformity of the adhesion of the conductive fine particles to the toner particles deteriorates, which is not preferable.

The release rate of the conductive fine powder can be measured by the aforementioned particle analyzer, and is determined by the following equation.

(Equation 7)

As a specific measuring method, channel 1
And the metal element of the conductive fine powder in channel 3 (the measurement wavelength varies depending on the type of the metal element. For example, when zinc oxide is used as the conductive fine particles, the measurement wavelength is 334.500 nm, K Use the recommended value for the factor).

When the magnetic toner of the present invention is applied to an image forming method utilizing development and cleaning, the conductive fine powder plays an important role.

Here, the behavior of the toner particles and the conductive fine powder during the image forming process when the conductive fine powder is externally added to the toner particles will be described.

The conductive fine powder contained in the magnetic toner is as follows:
During development of the electrostatic latent image on the image carrier in the developing step, an appropriate amount moves to the image carrier together with toner particles. The toner image on the image carrier is transferred to the recording medium in the transfer step. A part of the conductive fine powder on the image carrier also adheres to the recording medium side, but the rest remains adhered and held on the image carrier.
When a transfer is performed by applying a transfer bias having a polarity opposite to that of the magnetic toner, the magnetic toner is pulled toward the recording medium and actively transfers, but the conductive fine powder on the image carrier is conductive. As a result, the toner does not positively transfer to the recording medium side, and a part thereof adheres to the recording medium side but the rest remains adhered and held on the image carrier.

In the image forming method without using a cleaner, the untransferred toner remaining on the surface of the image carrier after the transfer and the above-mentioned residual conductive fine powder are transferred to the charging portion which is the contact portion between the image carrier and the contact charging member. It is carried as it is by the movement of the image carrier surface and adheres to and mixes with the contact charging member. Therefore, the contact charging of the image carrier is performed in a state where the conductive fine powder is interposed in the contact portion between the image carrier and the contact charging member.

Due to the presence of the conductive fine powder, when the amount of toner remaining after transfer to the contact charging member is small, regardless of the contamination due to the adhesion or mixing of the toner remaining after transfer, the fine contact property of the contact charging member to the image carrier is not affected. Therefore, the image bearing member can be favorably charged by the contact charging member.

The transfer residual toner adhering to and mixed into the contact charging member is uniformly charged to the same polarity as the charging bias by the charging bias applied from the charging member to the image carrier, and gradually becomes an image from the contact charging member. Exhaled on the carrier,
As the image carrier surface moves, it reaches the developing section, where it is developed and cleaned (collected) in the developing step.

Further, as the image formation is repeated, the conductive fine powder contained in the magnetic toner moves to the image carrier surface in the developing section, and is carried by the charging section via the transfer section by the movement of the image carrying surface. Since the conductive fine powder is continuously supplied to the charged part after being transported, even if the conductive fine powder is dropped or deteriorated due to dropping or the like in the charged part, it is prevented that the chargeability is reduced. And good chargeability is stably maintained.

For this reason, the release rate of the conductive fine powder was 5.0.
% To 50.0%. If the release rate of the conductive fine powder is less than 5.0%, the amount of the conductive fine powder held on the image carrier is reduced, and good chargeability cannot be obtained. When the release rate of the conductive fine powder is more than 50.0%, the amount of the conductive fine powder recovered by the developing and cleaning increases, and the conductive fine powder easily accumulates in the developing device. In addition, the chargeability and developability of the magnetic toner are deteriorated.

In order to promote the uniformity of the charge amount of the magnetic toner, the resistance of the conductive fine powder should be 1 × 10 ⁹ Ω.
cm or less is preferred. The resistance of the conductive fine powder is 1 × 10
^If it is larger than ⁹ Ωcm, the conductive fine powder is interposed in the contact area between the charging member and the image carrier and the charging area in the vicinity thereof, and the contact charging member is densely packed on the image carrier via the conductive fine powder. Even if good contact properties are maintained, it is difficult to obtain a charge promotion effect for obtaining good chargeability. In order to sufficiently bring out the charge promoting effect of the conductive fine powder and stably obtain good chargeability, the resistance of the conductive fine powder is limited by the resistance of the surface portion of the contact charging member or the contact portion with the image carrier. It is preferably smaller than.

Further, the resistance of the conductive fine powder is 1 × 10 ⁸
It is preferably at most Ωcm in order to overcome the charging inhibition due to the adhesion and mixing of the insulative transfer residual toner to the contact charging member and to perform better charging of the image carrier.

In the present invention, the content of the conductive fine powder in the whole magnetic toner is preferably 0.5 to 10% by mass. When the content of the conductive fine powder with respect to the entire magnetic toner is less than 0.5% by mass, the charging of the image carrier is overcome by overcoming the charge inhibition due to the adhesion and mixing of the insulating transfer residual toner to the contact charging member. A sufficient amount of conductive fine powder to perform well can not be interposed in the contact area between the charging member and the image carrier or in the vicinity of the charging area,
In some cases, the chargeability is reduced, resulting in poor charging. On the other hand, when the content is more than 10% by mass, the chargeability and developability of the magnetic toner in the developing section due to the excessive amount of the conductive fine powder collected by the developing and cleaning are reduced, and the image density is reduced. And toner scattering. The content of the conductive fine powder with respect to the entire magnetic toner is
It is preferably 0.5 to 5% by mass.

Specifically, the volume average particle diameter of the conductive fine powder is preferably 0.1 μm or more, and is preferably smaller than the weight average particle diameter of the magnetic toner. When the volume average particle diameter of the conductive fine powder is small, the content of the conductive fine powder with respect to the entire magnetic toner must be set small in order to prevent a decrease in the developing property. If the volume average particle size of the conductive fine powder is less than 0.1 μm, an effective amount of the conductive fine powder cannot be secured, and in the charging step, charging due to adhesion and mixing of the insulating transfer residual toner to the contact charging member. A sufficient amount of conductive fine powder to overcome the inhibition and make the charging of the image carrier good can not be interposed in the contact area between the charging member and the image carrier and the charging area in the vicinity thereof, Poor charging easily occurs.

When the volume average particle diameter of the conductive fine powder is larger than the weight average particle diameter of the magnetic toner, the conductive fine powder dropped from the charging member shields or diffuses the exposure for writing the electrostatic latent image, This may cause a defect of the electrostatic latent image and degrade the image quality. Further, when the volume average particle diameter of the conductive fine powder is large, the number of particles per unit weight is reduced. In order to continuously supply and interpose the conductive fine powder to the contact area between the charging member and the image carrier or in the vicinity of the charging area, the contact charging member is connected to the image carrier via the conductive fine powder. In order to maintain a close contact property and stably obtain good chargeability, the content of the conductive fine powder in the entire magnetic toner must be increased.
However, if the content of the conductive fine powder is too large, the chargeability and developability of the magnetic toner as a whole, particularly in a high-humidity environment, are reduced, resulting in a reduction in image density and toner scattering. From such a viewpoint, the volume average particle diameter of the conductive fine powder is preferably 5 μm or less.

The conductive fine powder is preferably a transparent, white or light-colored conductive fine powder, since the conductive fine powder transferred onto the recording medium is not conspicuous as fog. The conductive fine powder is preferably a transparent, white or light-colored conductive fine powder even in a sense that does not hinder the exposure in the electrostatic latent image forming step, and more preferably, the conductive fine powder has a transmittance to the exposure. Is preferably 30% or more.

In the present invention, the light transmittance of the conductive fine powder can be measured by the following procedure. The transmittance is measured with one layer of the conductive fine powder of a transparent film having an adhesive layer on one side fixed. The light is irradiated from the vertical direction of the sheet, and the light transmitted to the back of the film is collected and the amount of light is measured. The transmittance of the conductive fine powder is calculated as a net light amount from the light amount when only the film and the conductive fine powder are adhered. Actually, it can be measured using a 310T transmission densitometer manufactured by X-Rite.

In the measurement of the volume average particle diameter and the particle size distribution of the conductive fine powder in the present invention, for example, L
An S-230 type laser diffraction type particle size distribution analyzer having a liquid module attached thereto can be used, and the measurement range is preferably from 0.04 to 2000 μm. As a measuring method, a trace amount of a surfactant was added to 10 mL of pure water, and a 10 mg sample of a conductive fine powder was added thereto.
After dispersing for 10 minutes with an ultrasonic disperser (ultrasonic homogenizer), a method of measuring for 90 seconds and measuring once can be exemplified.

In the present invention, the method of adjusting the particle size and the particle size distribution of the conductive fine powder may be adjusted so that the primary particle of the conductive fine powder has a desired particle size and particle size distribution at the time of manufacturing. In addition to the setting method, a method of aggregating small primary particles, a method of pulverizing large primary particles or a method of classification can be used. Further, base particles having a desired particle size and particle size distribution ( In preparing the conductive fine powder, a method of attaching or fixing the conductive fine powder to part or all of the surface of the base material when attaching or fixing the conductive material, a desired particle size and particle size It is also possible to use a method using a conductive fine powder having a form in which a conductive component is dispersed in particles of distribution,
It is also possible to adjust the particle size and particle size distribution of the conductive fine powder by combining these methods.

When the particles of the conductive fine powder are constituted as an aggregate, the particle size is defined as the average particle size of the aggregate. There is no problem that the conductive fine powder exists not only in the state of primary particles but also in the state of aggregation of secondary particles. Regardless of the agglomerated state, the form is not limited as long as the agglomerate is interposed in the abutting portion between the charging member and the image carrier or in the charged area in the vicinity thereof and can realize the function of assisting or promoting charging.

In the present invention, the resistance of the conductive fine powder can be measured and normalized by a so-called tablet method. More specifically, a powder sample of about 0.5 g was placed in a cylinder having a bottom area of 2.26 cm ² and 15 k
Simultaneously with the pressurization of g, a voltage of 100 V is applied to measure the resistance value, and then normalized to calculate the specific resistance.

Examples of the conductive fine powder in the present invention include fine carbon powder such as carbon black and graphite; fine metal powder such as copper, gold, silver, aluminum and nickel; zinc oxide, titanium oxide, tin oxide and aluminum oxide. , Indium oxide, silicon oxide, magnesium oxide,
Metal oxides such as barium oxide, molybdenum oxide, and tungsten oxide; metal compounds such as molybdenum sulfide, cadmium sulfide, and potassium titanate, or composite oxides of these are used by adjusting the particle size and particle size distribution as necessary. it can. Among these, the conductive fine powder is preferably non-magnetic, and inorganic oxide fine powder such as zinc oxide, tin oxide and titanium oxide is particularly preferable.

For the purpose of controlling the resistance value of the conductive inorganic oxide, a metal oxide doped with an element such as antimony or aluminum, a fine powder having a conductive material on its surface, or the like can be used. For example, titanium oxide fine powder surface-treated with tin oxide / antimony, stannic oxide fine powder doped with antimony, or stannic oxide fine powder.

As commercially available conductive titanium oxide fine powder treated with tin oxide / antimony, for example, EC-300
(Titanium Industry Co., Ltd.), ET-300, HJ-1, H
I-2 (above, Ishihara Sangyo Co., Ltd.), WP (Mitsubishi Materials Corporation) and the like.

Commercially available antimony-doped conductive tin oxides include, for example, T-1 (Mitsubishi Materials Corporation) and SN-100P (Ishihara Sangyo Co., Ltd.). S (Japan Chemical Industry Co., Ltd.).

The magnetic toner of the present invention further has a primary particle size of more than 30 nm (preferably having a specific surface area of less than 50 m ² / g), more preferably a primary particle size of 50 nm or more (preferably) for the purpose of improving the cleaning property. Has a specific surface area of 3
It is also a preferred embodiment to further add inorganic or organic particles having a spherical shape (less than 0 m ² / g). For example, spherical silica particles, spherical polymethylsilsesquioxane particles, spherical resin particles and the like are preferably used.

The magnetic toner used in the present invention may further contain other additives, for example, lubricant powders such as Teflon (registered trademark) powder, zinc stearate powder, polyvinylidene fluoride powder, etc., within a range that does not substantially adversely affect the toner. Or a polishing agent such as cerium oxide powder, silicon carbide powder, strontium titanate powder, or a fluidity imparting agent such as titanium oxide powder, aluminum oxide powder, an anti-caking agent,
Further, organic fine particles and inorganic fine particles of opposite polarity can be used in a small amount as a developing property improver. These additives can be used after the surface is subjected to a hydrophobic treatment.

The method of externally adding the fine powder to the magnetic toner is performed by mixing and stirring the magnetic particles (toner particles or magnetic toner) and the fine powder. Specific examples include mechanofusion, an I-type mill, a hybridizer, a turbo mill, and a Henschel mixer, and it is particularly preferable to use a Henschel mixer from the viewpoint of preventing generation of coarse particles.

Further, in order to adjust the release rate of the fine particles, it is preferable to adjust the temperature at the time of external addition, the external addition strength, the external addition time, and the like. When a Henschel mixer is used as an example, the temperature in the tank at the time of external addition is preferably 50 ° C. or less. If the temperature is higher than this, the external additive is rapidly embedded by heat and coarse particles are generated, which is not preferable. The peripheral speed of the blade of the Henschel mixer is preferably from 10 to 80 m / sec from the viewpoint of adjusting the release rate of the external additive. Note that the above-described adjustment of the release rate can be applied to the adjustment of the release rate of the inorganic fine powder and the conductive fine powder described above.

Since the magnetic toner of the present invention has excellent durability, low fog and high transferability, it is suitably used in an image forming method using a contact charging step, and is also used in a cleanerless image forming method. And these forms of use are also part of the present invention.

In the image forming method including the contact charging step, the key technique is to reduce the magnetic toner which is not transferred and goes to the charging step, that is, the transfer residual toner and the fog toner. By using the magnetic toner of the present invention having the performance as described above,
It is possible to obtain an image having excellent environmental stability over a long period of time.

In the cleaner-less image forming method, the transfer residual toner passes through the charging step and is collected in the developing device in the developing step. However, such a toner having poor transferability has poor chargeability. Since the amount is large, the toner is accumulated in the developing device together with the durability, and the image characteristics are easily deteriorated. Further, since the toner having poor transferability has a large amount of residual toner after transfer, uniform charging is hindered in the charging step, and it is difficult to obtain a good image. In particular, this tendency is strong in toner having poor durability, which is not preferable.

However, since the magnetic toner of the present invention has good image characteristics and durability, it can maintain high image quality stably for a long period of time even when used in a cleanerless image forming method. Thus, the image forming method of the present invention is achieved. Hereinafter, the image forming method of the present invention will be described.

The image forming method of the present invention includes a charging step, an electrostatic latent image forming step, a developing step, and a transferring step, wherein the magnetic toner of the present invention is used in the developing step. Further, the charging step is characterized in that the image carrier is charged by applying a voltage to a charging member that forms a contact portion with the image carrier and makes contact with the image carrier. Next, embodiments of the image forming method of the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto.

FIG. 1 shows an example of an image forming apparatus for realizing the image forming method of the present invention. In FIG. 1, a primary charging roller 117, a developing device 140, a transfer roller 114, a cleaner 116, a register roller 124, and the like, which are charging members, are provided around a photoreceptor 100 as an image carrier.

The photosensitive member 100 is charged to -700 V by the primary charging roller 117 (the applied voltage is an AC voltage-
2.0 kVpp (Vpp: peak-to-peak potential), DC voltage-
700 Vdc).

Then, the laser beam 123 is irradiated on the photoconductor 100 by the laser beam scanner 121,
00 is exposed, and an electrostatic latent image is formed on the photoconductor 100.

The electrostatic latent image on the photoreceptor 100 is
Is developed with a one-component magnetic toner, and is transferred onto a recording medium by a transfer roller 114 that is in contact with the photoconductor via the recording medium.

The recording medium P having the toner image thereon is conveyed to a fixing device 126 by a conveyor belt 125 or the like and is fixed on the recording medium P. Further, the toner partially left on the photoconductor is cleaned by the cleaner 116.

As shown in FIG. 2, the developing device 140 is provided near the photosensitive member 100 and has a cylindrical magnetic toner carrier 102 (hereinafter referred to as a “developing sleeve”) made of a nonmagnetic metal such as aluminum or stainless steel. Is disposed, and the photosensitive member 1
The gap between the sleeve 00 and the developing sleeve 102 is maintained at approximately 230 μm by a sleeve / photoconductor gap holding member (not shown) or the like. This gap can be changed if necessary. In the developing sleeve 102, a magnet roller 104 is fixed and disposed concentrically with the developing sleeve 102. However, the developing sleeve 102 is rotatable.

The magnet roller 104 is provided with a plurality of magnetic poles as shown, S1 is for development, N1 is for controlling the coating amount of magnetic toner, S2 is for taking in / conveying magnetic toner, and N2 is for preventing blowing out of magnetic toner. Affects.
An elastic blade 103 is provided as a member that regulates the amount of magnetic toner adhered and conveyed to the developing sleeve 102, and the amount of magnetic toner conveyed to the developing area is controlled by the contact pressure of the elastic blade 103 against the developing sleeve 102. Is done. In the developing area, the photosensitive member 100 and the developing sleeve 1
A developing bias of a DC voltage or an AC voltage is applied between the developing roller 102 and O.sub.02, and the toner on the developing sleeve 102 flies on the photoconductor 100 according to the electrostatic latent image to become a visible image.

In the image forming method of the present invention, the developing step is an image having a developing / cleaning step or a cleaner-less step also serving as a cleaning step for collecting the magnetic toner remaining on the photoreceptor after transferring the toner image onto the transfer material. Preferred image formation is possible even with the formation method.

In the image forming method of the present invention, in the charging step, it is preferable that the conductive fine powder is interposed in at least one of the contact portion between the charging member and the image carrier and the vicinity thereof. In the image forming method of the present invention, as means for interposing a conductive fine powder in the contact portion and the vicinity thereof,
For example, charging means used in the image forming method of the present invention,
A conductive fine powder supply means such as a hopper for supplying the conductive fine powder to the charging member can be exemplified.

Further, in the present invention, the conductive fine powder contained in the magnetic toner of the present invention can be used to interpose the conductive fine powder in the contact portion and the vicinity thereof.
That is, the conductive fine powder contained in the magnetic toner adheres to the image carrier in the developing process, and remains on the image carrier after the transfer process, and is conveyed to the contact portion and the vicinity thereof. Such a method of supplying the conductive fine powder is particularly effective in a developing and cleaning image forming method or a cleanerless image forming method, and is preferably used in the present invention.

In the charging step of the present invention, if the amount of the conductive fine powder present in the contact portion between the image carrier and the contact charging member is too small, the lubricating effect of the fine powder cannot be sufficiently obtained, and The friction between the body and the charging member is large, making it difficult to rotate the charging member with respect to the image carrier with a speed difference. That is, the driving torque becomes excessively large, and the surface of the charging member or the image bearing member is scraped if it is rotated forcibly. Further, the effect of increasing the chance of contact by the conductive fine powder may not be obtained, so that sufficient charging performance cannot be obtained. On the other hand, if the intervening amount is too large, the detachment of the conductive fine powder from the charging member is significantly increased, which may adversely affect image formation.

In the charging step of the present invention, the image carrier is charged in a state where 1 × 10 ³ / mm ² or more conductive fine powders are interposed in the contact portion between the charging member and the image carrier. Is preferred. More preferably, it is more than 10 ⁴ / mm ² .
If it is lower than 10 ³ / mm ² , sufficient lubricating effect and effect of increasing the chance of contact cannot be obtained as described above, and the charging performance tends to decrease. On the other hand, if it is lower than 10 ⁴ particles / mm ^2, there is a possibility that the charging performance may be reduced when the amount of residual toner is large.

The amount of the conductive fine powder present in the contact portion and the amount of the conductive fine powder present on the image carrier in the latent image forming step can be measured directly from the contact surface between the charging member and the image carrier. Desirably, when a speed difference is provided between the surface of the charging member forming the contact portion and the surface of the image carrier, most of the particles present on the image carrier before contacting the charging member are reversed. In the present invention, the amount of particles on the surface of the charging member immediately before reaching the contact surface portion is defined as the intervening amount since the charging member is peeled off by the charging member that comes into contact with the moving member.

More specifically, the rotation of the image carrier and the charging member (for example, a roller member) is stopped in a state where no charging bias is applied, and the surfaces of the image carrier and the roller member are cleaned with a video microscope (for example, OVM1000 manufactured by OLYMPUS).
N) and a digital still recorder (for example, DELTAS
(SR-3100). The roller member is brought into contact with the slide glass under the same conditions as the roller member is brought into contact with the image carrier, and the contact surface is photographed from a rear surface of the slide glass with a video microscope at ten or more locations using a 1000 × objective lens. In order to separate individual particles from the obtained digital image, binarization processing is performed with a certain threshold value, and the number of regions where particles are present is measured using desired image processing software. In addition, the abundance on the image carrier is measured by photographing the image carrier with the same video microscope and performing the same processing.

In the image forming method of the present invention, in particular, the cleaner-less image forming method, the charging member has an elasticity in providing a contact portion for interposing conductive fine powder between the charging member and the image carrier. It is preferable that the conductive member is electrically conductive in order to charge the image carrier by applying a voltage to the charging member. Therefore, the charging member is constituted by a roller member which is a conductive elastic roller, a magnetic brush charging member having a magnetic brush portion in which magnetic particles are magnetically constrained, and the magnetic brush portion is brought into contact with a photoreceptor, or a conductive fiber. Preferably, the brush member is a brush member.

Further, in the image forming method of the present invention, the fact that the charging member has flexibility is an opportunity for the conductive fine powder to come into contact with the image carrier at the contact portion between the charging member and the image carrier. Is preferable in that high contact property can be obtained and direct injection charging property can be improved.

That is, the charging member comes into close contact with the image carrier through the conductive fine powder, and the conductive fine powder present at the contact portion between the charging member and the image carrier causes the surface of the image carrier to have no gap. By rubbing, the charging of the image carrier by the charging member is performed by stable and safe direct injection charging without using a discharge phenomenon due to the presence of the conductive fine powder, and high charging which cannot be obtained by conventional roller charging or the like. Efficiency is obtained, and a potential substantially equal to the voltage applied to the charging member can be given to the image carrier.

Further, in the image forming method of the present invention, in the charging step, the surface of the charging member forming the contact portion and the surface of the image bearing member move the image bearing member while moving with a relative speed difference. Preferably, it is a step of charging. According to such a charging step, the chance that the conductive fine powder comes into contact with the image carrier in the contact portion can be increased remarkably, higher contact properties can be obtained, and direct injection charging properties can be improved. It is preferable and preferable in terms of improvement.

Further, by interposing conductive fine powder at the contact portion between the charging member and the image carrier, the lubricating effect (friction reducing effect) of the conductive fine powder causes the contact between the charging member and the image carrier. Thus, it is possible to provide a speed difference without significantly increasing the torque and remarkably shaving the surface of the charging member and the image carrier.

In order to temporarily collect and level the transfer residual toner on the image carrier carried to the abutting portion by the charging member, the charging step in the present invention comprises the steps of: It is preferable to charge the image carrier while the surfaces of the image carriers move in opposite directions. For example, it is desirable that the charging member be driven to rotate, and that the rotation direction be rotated in a direction opposite to the moving direction of the surface of the image carrier at the contact portion. That is, the toner remaining after transfer on the image carrier is once separated and charged by rotating in the reverse direction,
Advantageously, direct injection charging can be performed.

Although the charging member can be moved in the same direction as the moving direction of the surface of the image carrier to have a speed difference, the chargeability of the direct injection charging depends on the peripheral speed of the image carrier and the peripheral speed of the charging member. In order to obtain the same peripheral speed ratio as in the reverse direction, the rotation speed of the charging member in the forward direction is larger than that in the reverse direction. This is advantageous.

As a configuration for providing a speed difference, the charging member can be driven to rotate to provide a speed difference between the image carrier and the charging member. The peripheral speed ratio described here can be expressed by the following equation.

## EQU8 ## Peripheral speed ratio (%) = (charging member peripheral speed / image carrier peripheral speed) × 100

In order to temporarily recover the transfer residual toner on the image carrier to the charging member and to carry the conductive fine powder to perform the direct injection charging, the charging member is preferably flexible. More preferably, it is rotatable. As such a charging member, a roller member having conductivity and elasticity, a conductive brush member, and the like can be preferably exemplified as described above.

In the present invention, the roller member used as the charging member preferably has an Asker C hardness of 50 degrees or less. If the hardness is too low, the shape will not be stable and the contact with the image carrier will be poor, and furthermore, the surface of the roller member will be shaved by interposing conductive fine powder in the contact portion between the charging member and the image carrier. Or a tendency to be damaged, and stable chargeability cannot be obtained. On the other hand, if the hardness is too high, not only is it impossible to secure a charging contact portion with the image carrier, but also the microscopic contact with the surface of the image carrier tends to deteriorate. Further, a preferred range is 25 to 50 degrees in Asker C hardness.

The roller member used in the present invention can be produced, for example, by forming a rubber or foam medium resistance layer as a flexible member on a cored bar. The medium resistance layer is formulated with a resin (eg, urethane), conductive particles (eg, carbon black), a sulfide agent, a foaming agent, and the like, and is formed in a roller shape on a cored bar. Thereafter, if necessary, the roller member can be manufactured by cutting and polishing the surface to adjust the shape.

In the present invention, the roller member has at least a dent on its surface having an average cell diameter of 5 to 300 μm in terms of sphere, and the porosity of the surface of the roller member having the dent as a void portion. Is preferably from 15 to 90% in order to interpose conductive fine powder on the surface of the roller member.

When the average cell diameter on the surface of the roller member is smaller than 5 μm, the supply of the conductive fine powder becomes insufficient,
When the average particle diameter exceeds μm, the supply of the conductive fine powder becomes excessive and the charging potential of the image carrier becomes non-uniform. On the other hand, if the porosity is less than 15%, the supply of the conductive fine powder is insufficient, and if it exceeds 90%, the supply of the conductive fine powder becomes excessive, and in any case, the charging potential of the image carrier becomes uneven. Is not preferred.

It is important that the roller member has elasticity so as to obtain a sufficient contact state with the member to be charged and, at the same time, functions as an electrode having a resistance low enough to charge the moving member to be charged. On the other hand, it is necessary to prevent voltage leakage when a defect site such as a pinhole is present in the member to be charged. When a photoreceptor is used as the image carrier, in order to obtain sufficient chargeability and leakage resistance, the charging member used in the charging step in the present invention has a volume resistance of 1 × 10 ³ to 1 ×.
The resistance is preferably 10 ⁸ Ωcm, more preferably the volume resistance is 1 × 10 ⁴ to 1 × 10 ⁷ Ωcm.

The volume resistance value of the roller member is set such that 100 V is applied between the core metal and the aluminum drum while the roller is pressed against a cylindrical aluminum drum having a diameter of 30 mm so that a total pressure of 1 kg is applied to the core metal of the roller. It can be measured by applying and measuring.

The material of the roller member is not limited to an elastic foam, and the material of the elastic material may be adjusted to resistance to ethylene-propylene-diene polyethylene, urethane, butadiene acrylonitrile rubber, silicone rubber, isoprene rubber, or the like. For this purpose, a rubber material in which a conductive substance such as carbon black or a metal oxide is dispersed, or a foamed material thereof can be used. It is also possible to adjust the resistance by using an ion conductive material without dispersing the conductive particles or in combination with the conductive particles.

[0302] Examples of the core metal used for the roller member include aluminum and SUS.

The roller member is disposed so as to be pressed against a member to be charged as an image carrier with a predetermined pressing force against elasticity to form a contact portion between the roller member and the image carrier. The width of the abutting portion is not particularly limited, but is preferably 1 mm or more, more preferably 2 mm or more in order to obtain a stable and close adhesion between the roller member and the image carrier.

In the charging step of the present invention, a brush member having conductivity can be suitably used as the charging member. Examples of the brush member as the charging member include a charging brush in which resistance is adjusted by dispersing a conductive material in generally used fibers.

As the fibers, generally known fibers can be used, for example, nylon, acrylic, rayon, polycarbonate, polyester and the like.
As the conductive material, generally known conductive materials can be used, for example, conductive metals such as nickel, iron, aluminum, gold, and silver, or iron oxide, zinc oxide, tin oxide, antimony oxide, titanium oxide, and the like. And a conductive powder such as carbon black. In addition, these conductive materials may be subjected to a surface treatment for the purpose of hydrophobicity and resistance adjustment as required. At the time of use, it is selected and used in consideration of dispersibility with fibers and productivity.

When a brush member is used as the charging member, there are a fixed type and a rotatable roll type. As the roll-shaped charging brush, for example, a tape in which conductive fibers are piled may be spirally wound around a metal core to form a roll-shaped brush member. The conductive fiber has a fiber thickness of 1 to 20 denier (fiber diameter of 10 to 5).
The length of the brush fiber is 1 to 15 mm,
A brush density of 10,000 to 300,000 brushes per square inch (about 1.5 × 10 ^{7 to} 4.5 × 10 ⁸ brushes per square meter) is preferably used.

It is preferable to use a brush member having the highest possible brush density, and it is also preferable to make one fiber from several to several hundreds of fine fibers. For example, 30
It is also possible to bundle 50 fine fibers of 300 denier, such as 0 denier / 50 filament, and to implant them as one fiber. However, in the present invention,
The charging point of direct injection charging is determined mainly by the contact density between the charging member and the image carrier and the density of conductive fine powder in the vicinity thereof. The range has been widened.

As the core metal used for the brush member, those similar to those used for the roller member can be used.

As the material of the brush member, for example, conductive rayon fibers REC-B, REC-B manufactured by Unitika Ltd. may be used.
C, REC-M1, REC-M10, S manufactured by Toray Industries, Inc.
A-7, Thunderon manufactured by Nippon Silk Co., Ltd., Bertron manufactured by Kanebo Co., Ltd., Clacarbo manufactured by Kuraray Co., Ltd., a product obtained by dispersing carbon in rayon, Robal manufactured by Mitsubishi Rayon Co., Ltd. REC-B, RE in terms of stability
Particularly preferred are CC, REC-M1, and REC-M10.

In the charging step in the image forming method of the present invention, in addition to the roller type (charging roller) as the primary charging roller in FIG. A contact portion is formed and brought into contact with a conductive charging member (contact charging member / contact charger) such as a magnetic brush type or a blade type (charging blade), and a predetermined charging bias is applied to the contact charging member. And a contact charging device for charging the photoreceptor surface to a predetermined polarity and potential. The charging step using these contact charging members has the effects of eliminating the need for high voltage and reducing the generation of ozone.

As a preferable process condition when the charging roller is used as shown in FIG. 1, the contact pressure of the roller member is 4.9 to 490 N / m (5 to 500 g / cm) and the DC voltage or the DC voltage is reduced. A superimposed AC voltage is used. When a voltage obtained by superimposing an AC voltage on a DC voltage is used, an AC voltage = 0.5 to 5 kVpp and an AC frequency = 50
５5 kHz, DC voltage = ± 0.2〜 ± 5 kV are preferred.

In the case where an AC voltage is used as described above, the charging step in the present invention is performed by applying 2 × Vth
(Vth: discharge start voltage when DC voltage is applied) (V)
It is preferable to apply a voltage obtained by superimposing an AC voltage having a peak-to-peak voltage of less than a DC voltage.

If the peak voltage of the AC voltage applied to the DC voltage is not less than 2 × Vth, the potential on the image carrier may become unstable, which is not preferable. As an AC voltage when applying a bias in which an AC voltage is superimposed on a DC voltage, the AC voltage more preferably has a peak voltage less than Vth. Thereby, the image carrier can be charged without a substantial discharge phenomenon.

As a waveform of the AC voltage used in the charging step, a sine wave, a rectangular wave, a triangular wave, or the like can be appropriately used. Alternatively, a pulse wave formed by periodically turning on / off a DC power supply may be used. As described above, as the waveform of the AC voltage, a bias whose voltage value periodically changes can be used.

Next, in the image forming method of the present invention, an image carrier which is a member to be charged in the charging step will be described.

In the image forming method of the present invention, the image carrier is preferably a photoconductor using a photoconductive substance, and preferably has a surface layer.

One more preferred embodiment of the image bearing member used in the present invention will be described below. In the present invention,
The volume resistance value of the outermost surface layer of the image carrier is 1 × 10 ⁹ to 1 × 1.
A value of 0 ¹⁴ Ωcm is preferred in order to give better chargeability to the image bearing member. In the charging method by direct injection of electric charges, the electric charges can be transferred more efficiently by lowering the resistance on the side of the image carrier which is the object to be charged. For this purpose, the volume resistance value of the outermost surface layer of the image carrier is preferably 1 × 10 ¹⁴ Ωcm or less. On the other hand, in order to hold the electrostatic latent image as the image carrier for a certain period of time, the volume resistance value of the outermost surface layer is 1 × 10 ⁹
It is preferably and preferably Ωcm or more.

Further, since the outermost layer of the image carrier has a volume resistivity of 1 × 10 ⁹ to 1 × 10 ¹⁴ Ωcm, sufficient chargeability can be provided even in an apparatus having a high process speed. preferable.

The method of measuring the volume resistivity of the outermost surface layer of the image carrier according to the present invention is based on the same composition as the outermost surface layer of the image carrier on a polyethylene terephthalate (PET) film having gold deposited on the surface. Is prepared by applying a voltage of 100 V at 23 ° C. and a 65% environment using a volume resistance measuring device (for example, 4140B pA MATER manufactured by Hewlett-Packard Co.).

In the present invention, in order to adjust the volume resistance of the outermost surface layer of the image carrier, the outermost surface layer is
It is preferable that the resin layer is a resin layer in which at least conductive particles made of a metal oxide are dispersed.

Examples of the conductive particles include metals, metal oxides, etc., preferably, zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide, bismuth oxide, tin oxide coating, titanium oxide, and tin coating. There are ultrafine particles such as indium oxide, antimony-coated tin oxide, and zirconium oxide. These may be used alone or in combination of two or more.

Generally, when conductive particles are dispersed in the outermost surface layer, it is necessary that the particle size of the particles is smaller than the wavelength of the incident light in order to prevent scattering of the incident light by the dispersed particles. The particle size of the conductive particles dispersed in the layer is preferably 0.5 μm or less. Further, the content of the conductive particles in the outermost surface layer is 2% based on the total weight of the outermost surface layer.
It is preferably from 90 to 90% by mass, more preferably from 5 to 80% by mass. The thickness of the outermost surface layer is preferably from 0.1 to 10 μm, more preferably from 1 to 7 μm.

In the image forming method of the present invention, various image carriers can be suitably used. For example, when a protective film mainly composed of a resin is provided on an inorganic photoreceptor such as selenium or amorphous silicon, or The charge transport layer of the function-separated type organic image carrier may have a surface layer composed of a charge transport material and a resin, or may further have a protective layer provided thereon to form the outermost surface layer.

It is preferable to impart releasability to the outermost surface layer of the image bearing member in order to further improve the transferability of the magnetic toner and the durability of the image bearing member. The contact angle of water on the surface of the image carrier used is preferably 85 degrees or more. More preferably, the contact angle is 90 degrees or more.

The contact angle of the surface of the photoreceptor with water can be made 85 ° or more by means described later, and the transferability of the toner and the durability of the photoreceptor can be further improved. Preferably, the contact angle with water is 90 degrees or more.

The contact angle is measured by a drop-type contact angle meter (for example, a contact angle meter CA-X of Kyowa Interface Science Co., Ltd.).
Where the free surface of water is in contact with the image carrier, and is defined by the angle between the liquid surface and the surface of the image carrier (the angle inside the liquid).

The above measurement is performed at room temperature (about 25 ° C.). The same measurement was performed in Examples described later.

As means for imparting the above-mentioned releasability to the surface of the image carrier, (1) a resin having a low surface energy is used for the resin constituting the film, and (2) water-repellency and lipophilicity are imparted. And (3) dispersing a material having a high mold release property into a powdery state.

As an example of (1), this can be achieved by introducing a fluorine-containing group, a silicone-containing group and the like into the structure of the resin. As (2), a surfactant or the like may be used as an additive. As (3), a compound containing a fluorine atom, that is, polytetrafluoroethylene, polyvinylidene fluoride,
And carbon fluoride.

[0330] Among these means, the means (3) is more preferable. That is, the outermost surface layer of the image carrier is a resin layer in which at least one or more lubricant fine particles selected from fluorine-based resin particles, silicone-based resin particles, and polyolefin-based resin particles are dispersed. This is one preferable mode in the formation method. Among the above lubricant fine particles, a method of dispersing a releasable powder of fluororesin particles such as a fluororesin in the outermost surface layer is preferable, and it is particularly preferable to use polytetrafluoroethylene.

In order to incorporate the above lubricant fine particles into the surface of the image bearing member, a layer in which the fine particles are dispersed in a binder resin is provided on the outermost surface of the image bearing member, or a layer mainly composed of resin is used. If an image carrier such as an organic photoreceptor is used, the powder may be dispersed in the uppermost layer without providing a new surface layer. The amount of addition is preferably 1 to 60% by mass, more preferably 2 to 50% by mass, based on the total weight of the surface layer. If the amount is less than 1% by mass, the effect of improving the transferability of the magnetic toner and the durability of the image carrier is insufficient, and
Exceeding the range is not preferred because the strength of the film is reduced or the amount of light incident on the image carrier is significantly reduced.

The image forming method of the present invention is a direct charging method in which the charging means contacts the charging member to the image carrier, and is preferable in that generation of ozone is small. Since the load on the surface of the image carrier is larger than that of a method using corona discharge or the like, the above-described configuration has a remarkable improvement effect in terms of the life of the image carrier, and is one of the preferable application forms.

As the image bearing member used in the present invention, as described above, various conventionally known image bearing members can be used, and the conductive member and the conductive member are formed on the conductive member. An image carrier having a photosensitive layer is used. As the photosensitive layer, a photosensitive layer formed by laminating a plurality of layers having various functions such as a charge generation layer, a charge transport layer, and a surface layer (protective layer) for protecting the surface of the image carrier is used. I can do it.

As the conductive substrate, metals such as aluminum and stainless steel, aluminum alloys, indium oxide
Cylindrical cylinders and films of plastic having a coating layer of a tin oxide alloy or the like, paper impregnated with conductive particles, plastic, plastic having a conductive polymer, and the like are used.

On these conductive substrates, the adhesiveness of the photosensitive layer is improved, the coating properties are improved, the substrate is protected, and defects are coated on the substrate.
An undercoat layer may be provided for the purpose of improving the charge injection property from the substrate and protecting the photosensitive layer against electrical destruction. The undercoat layer is polyvinyl alcohol, poly-N-vinyl imidazole, polyethylene oxide, ethyl cellulose, methyl cellulose, nitrocellulose, ethylene-acrylic acid copolymer, polyvinyl butyral, phenol resin, casein, polyamide, copolymerized nylon, glue,
It is formed of a material such as gelatin, polyurethane, and aluminum oxide. The film pressure is usually 0.1 to 10 μm,
Preferably it is about 0.1 to 3 μm.

The charge generation layer is composed of an azo pigment, a phthalocyanine pigment, an indigo pigment, a perylene pigment, a polycyclic quinone pigment, a squarylium dye, a pyrylium salt, a thiopyrylium salt, a triphenylmethane dye, selenium,
It is formed by dispersing a charge generating substance such as an inorganic substance such as amorphous silicon in a suitable binder and coating or vapor-depositing. The binder can be selected from a wide range of binder resins, for example, polycarbonate resin, polyester resin, polyvinyl butyral resin, polystyrene resin, acrylic resin, methacryl resin, phenol resin, silicone resin, epoxy resin, vinyl acetate resin, etc. Is mentioned. The amount of the binder contained in the charge generation layer is 80% by mass.
Hereinafter, it is preferably 0 to 40% by mass. The film pressure of the charge generation layer is preferably 5 μm or less, particularly preferably 0.05 to 2 μm.

The charge transport layer has a function of receiving charge carriers from the charge generation layer in the presence of an electric field and transporting them. The charge transporting layer is formed by dissolving a charge transporting substance in a solvent together with a binder resin if necessary, and applying the solution. The film pressure is generally 5 to 40 μm. As the charge transport material, biphenylene,
Anthracene, pyrene, polycyclic aromatic compounds having a structure such as phenanthrene, indole, carbazole, oxadiazole, nitrogen-containing cyclic compounds such as pyrazoline,
Hydrazone compounds, styryl compounds, selenium, selenium-
Tellurium, amorphous silicon, cadmium sulfide and the like.

Examples of the binder resin for dispersing these charge transport substances include polycarbonate resin, polyester resin, polymethacrylate, polystyrene resin, and the like.
Examples include resins such as acrylic resins and polyamide resins, and organic photoconductive polymers such as poly-N-vinylcarbazole and polyvinylanthracene.

A protective layer may be provided as a surface layer. As the resin of the protective layer, polyester, polycarbonate, acrylic resin, epoxy resin, phenol resin, or a curing agent of these resins is used alone or in combination of two or more.

The coating of the surface layer or the like can be carried out by spray coating, beam coating or permeation (dipping) coating of the resin dispersion.

In the present invention, it is preferable that the electrostatic latent image forming step of forming an electrostatic latent image on the charged surface of the image carrier is performed by image exposure means. The image exposure unit for forming an electrostatic latent image is not limited to a laser scanning exposure unit for forming a digital latent image, but may be a normal analog image exposure or another light emitting element such as an LED. It does not matter if an electrostatic latent image corresponding to image information can be formed, such as a combination of a light emitting element such as a fluorescent lamp and a liquid crystal shutter.

In the image forming method of the present invention, in order to obtain high image quality without fogging, a layer thickness smaller than the closest distance (between SD) between the magnetic toner carrier and the photosensitive member is provided on the magnetic toner carrier. Then, a magnetic toner is applied, and development is performed in a development step of performing development by applying an AC voltage. That is, a layer pressure regulating member that regulates the magnetic toner on the magnetic toner carrier is used so that the closest gap between the photoconductor and the magnetic toner carrier is wider than the toner layer thickness on the magnetic toner carrier. The fact that the layer pressure regulating member that regulates the magnetic toner on the magnetic toner carrier is regulated by the elastic member that is in contact with the magnetic toner carrier via the magnetic toner is particularly preferable from the viewpoint of uniformly charging the magnetic toner. preferable.

As described above, in the developing step in the image forming method of the present invention, 5 to 50 g
/ M ² is preferably formed. If the amount of toner on the magnetic toner carrier is less than 5 g / m ^2, it is difficult to obtain a sufficient image density, and the toner layer may become uneven due to excessive charging of the toner. If the amount of toner on the magnetic toner carrier is more than 50 g / m ² , toner scattering is likely to occur.

It is preferable that the magnetic toner carrier is installed facing the image carrier at a distance of 100 to 1000 μm. If the distance between the magnetic toner carrier and the image carrier is smaller than 100 μm, the change in the development characteristics of the magnetic toner with respect to the fluctuation of the distance becomes large, so that it is difficult to mass-produce an image forming apparatus satisfying stable image quality. Become. If the distance between the magnetic toner carrier and the image carrier is larger than 1000 μm, the ability of the magnetic toner to follow the latent image on the image carrier is reduced, so that image quality such as resolution is reduced and image density is reduced. Tend to invite. Preferably, the thickness is 120 to 500 μm.

In the image forming method of the present invention, in the developing step, an alternating electric field is applied as a developing bias to the magnetic toner carrier to transfer the toner to the electrostatic latent image on the image carrier to form a toner image. The applied developing bias may be a voltage obtained by superimposing an alternating electric field on a DC voltage.

As a waveform of the alternating electric field, a sine wave, a rectangular wave, a triangular wave, or the like can be used as appropriate. Alternatively, a pulse wave formed by periodically turning on / off a DC power supply may be used. As described above, as the waveform of the alternating electric field, a bias whose voltage value periodically changes can be used.

In the developing step of the present invention, at least a peak-to-peak electric field intensity of 3 × 10 ⁶ to 10 is applied between the magnetic toner carrier for carrying the toner and the image carrier.
It is preferable to apply an alternating electric field of × 10 ⁶ V / m and a frequency of 500 to 5000 Hz as a developing bias.

The electric field intensity due to the developing bias is 3 × 10⁶
If it is smaller than V / m, it will not work
Recovery of the transfer residual toner in the developing process
Good fog is likely to occur. Also, the developing bias
10 × 10 ⁶If it is larger than V / m,
Resolution due to crushing of fine lines due to too large developing power
Liable to cause deterioration of image quality due to deterioration of image quality and fog
Image defects due to leakage of the developing bias to the image carrier
Tends to occur.

If the frequency is lower than 500 Hz, the frequency of detachment of the magnetic toner from the latent image is reduced, and the recoverability of the transfer residual toner in the developing process is apt to decrease.
Image quality also tends to deteriorate. Also, if the frequency is 5000
If the frequency is higher than Hz, the amount of magnetic toner that can follow the change in the electric field decreases, so that the recoverability of the transfer residual toner decreases,
Developability tends to decrease.

The magnetic toner carrier used in the present invention is as follows.
A conductive cylinder (developing roller) formed of a metal or alloy such as aluminum or stainless steel is preferably used. The conductive cylinder may be formed of a resin composition having sufficient mechanical strength and conductivity, or a conductive rubber roller may be used. Further, the present invention is not limited to the cylindrical shape as described above, and may be in the form of an endless belt that is driven to rotate.

The surface roughness of the magnetic toner carrier used in the present invention is JIS center line average roughness (Ra) of 0.2.
It is preferably in the range of ~ 3.5 [mu] m. Ra is 0.
If it is less than 2 μm, the amount of charge on the magnetic toner carrier increases, and the developability tends to be insufficient. Ra is 3.5μ
When m exceeds m, the toner coat layer on the magnetic toner carrier becomes uneven, and the density tends to be uneven on the image. More preferably, it is preferably in the range of 0.5 to 3.0 μm.

In the present invention, the surface roughness Ra of the magnetic toner carrier is determined by the JIS surface roughness “JIS B 0601”.
And corresponds to the center line average roughness measured using a surface roughness measuring instrument (for example, Surfcoder SE-30H, manufactured by Kosaka Laboratory Co., Ltd.). Specifically, the measured length a is 2.5 m in the direction of the center line from the roughness curve.
m and extract the center line of this
When the axis and the direction of the vertical magnification are represented by the Y axis and the roughness curve is represented by y = f (x), the value obtained by the following equation is represented by micrometer (μm).

(Equation 9)

In order to adjust the surface roughness (Ra) of the magnetic toner carrier in the present invention to the above range, for example, the polishing state of the surface layer of the magnetic toner carrier is changed, or spherical carbon particles, carbon fine particles, graphite or the like is used. It becomes possible by a technique such as addition.

Furthermore, since the magnetic toner of the present invention has a high charging ability, it is desirable to control the total charge amount of the magnetic toner during development, and the surface of the magnetic toner carrier according to the present invention has conductive fine particles and fine particles. It is preferably covered with a resin layer in which a lubricant is dispersed.

The conductive fine particles contained in the coating layer of the magnetic toner carrier preferably have a resistance value of 0.5 Ωcm or less after being pressurized at 11.7 MPa (120 kg / cm ² ). The conductive fine particles are preferably carbon fine particles, a mixture of carbon fine particles and crystalline graphite, or crystalline graphite. The conductive fine particles preferably have a particle size of 0.005 to 10 μm.

Examples of the resin used for the resin layer include styrene resins, vinyl resins, polyethersulfone resins, polycarbonate resins, polyphenylene oxide resins, polyamide resins, fluororesins, cellulose resins, and acrylic resins. Thermoplastic resins such as epoxy resins, polyester resins, alkyd resins, phenol resins, melamine resins, polyurethane resins, urea resins, silicone resins, and polyimide resins can be used.

Among them, those having release properties such as silicone resin and fluorine resin, or polyether sulfone,
Polycarbonate, polyphenylene oxide, polyamide, phenolic resin, polyester, polyurethane,
Those having excellent mechanical properties such as styrene resins are more preferable. Particularly, a phenol resin is preferable.

It is preferable to use 3 to 20 parts by mass of the conductive fine particles per 10 parts by mass of the resin component from the viewpoint of imparting suitable conductivity.

When carbon fine particles and graphite particles are used in combination, it is preferable to use 1 to 50 parts by mass of carbon fine particles per 10 parts by mass of graphite. The volume resistivity of the resin layer of the magnetic toner carrier in which the conductive fine particles are dispersed is preferably 10 ^-6 to 10 ⁶ Ωcm.

In the present invention, the surface of the magnetic toner carrier that carries the magnetic toner may move in the same direction as the moving direction of the surface of the image carrier, or may move in the opposite direction. When the moving directions are the same, it is desirable that the ratio is at least 100% with respect to the moving speed of the image carrier. If it is less than 100%, the image quality tends to deteriorate. The higher the moving speed ratio, the larger the amount of toner supplied to the developing site, the more frequently toner is attached to and detached from the latent image, and unnecessary portions are scraped off and added to necessary portions repeatedly. As a result, an image faithful to the latent image can be obtained. Specifically, the moving speed of the magnetic toner carrier surface is 1.05 to 3.0 with respect to the moving speed of the image carrier surface.
Preferably, the speed is double.

Next, the contact transfer step preferably applied in the image forming method of the present invention will be specifically described. In the present invention, the recording medium that receives the transfer of the toner image from the image carrier may be an intermediate transfer member such as a transfer drum. When the recording medium is an intermediate transfer member, a toner image is obtained by transferring the intermediate transfer member to a transfer material such as paper again.

In the contact transfer step, the toner image is electrostatically transferred to the recording medium while the image carrier is in contact with the transfer member via the recording medium. It is preferably at least 9.9 N / m (3 g / cm), more preferably 19.6 N / m (20 g / cm).
That is all. When the linear pressure as the contact pressure is 2.9 N / m (3
g / cm) is not preferable because the conveyance of the recording medium and the occurrence of transfer failure are likely to occur.

As a transfer member in the contact transfer step, a transfer roller or a transfer belt is used. FIG. 3 shows an example of the configuration of the transfer roller. The transfer roller 34 includes at least a metal core 34a and a conductive elastic layer 34b,
The conductive elastic layer 34b is made of urethane or epichlorohydrin rubber in which a conductive material such as carbon is dispersed.
It is made of an elastic material of about ⁶ to 10 ¹⁰ Ωcm, and a transfer bias is applied by a transfer bias power supply 35.

The contact transfer method of the present invention is particularly effective in an image forming apparatus in which the surface of an image carrier is an organic compound. That is, when the organic compound forms the surface layer of the image carrier, the adhesive property with the binder resin contained in the toner particles is higher than that of other image carriers using an inorganic material, and the transfer property is higher. This is because it tends to decrease.

When the contact transfer method of the present invention is applied, the surface material of the image carrier used as the organic compound includes, for example, silicone resin, vinylidene chloride, ethylene-vinyl chloride, styrene-acrylonitrile, styrene-methyl Examples include methacrylate, styrene, polyethylene terephthalate, and polycarbonate, but are not limited thereto, and other monomers or copolymers and blends of the above-mentioned binder resins may be used.

The image forming method of the present invention to which the contact transfer method is applied is particularly effectively used for an image forming apparatus having a small-diameter image carrier having a diameter of 50 mm or less. That is, in the case of a small-diameter photosensitive member, the curvature for the same linear pressure is large, and the concentration of pressure in the contact portion is likely to occur. Although the same phenomenon is considered to occur in the belt-shaped image carrier, the present invention is also effective for an image forming apparatus having a radius of curvature of 25 mm or less at the transfer section.

In the image forming method of the present invention, in addition to the above-described steps, a fixing step of fixing a toner image on a recording medium and a pre-exposure step of erasing a latent image record on an image carrier after transfer are performed. For example, various steps can be used as needed.

The image forming apparatus for realizing the image forming method of the present invention is not particularly limited as long as the above-described steps and the like are realized.
Various configurations conventionally known can be used. For example, since a magnetic toner is used in the present invention, it is also possible to use a process cartridge in which an image carrier, developing means for realizing a developing step, and the like are integrally configured, and which is detachably mounted to the image forming apparatus main body. This is one of preferred configurations for suitably implementing the present invention.

[0369]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Production Examples and Examples, but this does not limit the present invention in any way. All parts in the following formulations are parts by mass.

(Production Example 1 of Surface-treated Magnetic Powder) An aqueous solution containing ferrous hydroxide was prepared by mixing 1.0 to 1.1 equivalents of a caustic soda solution with respect to iron ions in an aqueous ferrous sulfate solution. Was prepared. While maintaining the pH of the aqueous solution at about 9, air was blown therein to perform an oxidation reaction at 80 to 90 ° C. to prepare a slurry liquid for generating seed crystals.

Next, the slurry was added in an amount of 0.9 to 1.0 with respect to the initial alkali amount (sodium component of caustic soda).
After adding an aqueous solution of ferrous sulfate to 2 equivalents, the slurry solution is maintained at a pH of about 8 and the oxidation reaction is promoted while blowing air. The magnetic iron oxide particles generated after the oxidation reaction are washed, filtered and temporarily I took it out. At this time, a small amount of a water-containing sample was collected and the water content was measured. Next, after re-dispersing this water-containing sample in another aqueous medium without drying, the pH of the re-dispersed liquid was adjusted to about 6, and the silane coupling agent (n-C ₄ H ₁₃ Si (OC
3.0 parts by mass of H ₃ ) ₃ ) was added to 100 parts by mass of magnetic iron oxide (the amount of magnetic iron oxide was calculated as a value obtained by subtracting the water content from the water-containing sample), and a coupling treatment was performed.
The produced hydrophobic iron oxide particles were washed, filtered, and dried by a conventional method, and then a slightly aggregated particle was crushed to obtain a surface-treated magnetic powder 1. Table 1 shows the physical properties.

(Production Examples 2 to 6 of Surface-treated Magnetic Powder) Surface-treated magnetic powders 2 to 6 were produced in the same manner as in Production Example 1 of surface-treated magnetic powder except that the treatment amount of the silane coupling agent was adjusted. Obtained. Table 1 shows the physical properties.

(Production Examples 7 and 8 of Surface-treated Magnetic Powder) Except that the treatment amount of the silane coupling agent, the amount of the caustic soda solution to be added, and the reaction conditions were changed in Production Example 1 of the surface-treated magnetic powder. In the same manner as in Production Example 1 for surface-treated magnetic powder, surface-treated magnetic powders 7 and 8 were obtained. Table 1 shows the physical properties. (Production Example 9 of Surface-treated Magnetic Powder) The same as Production Example 1 of surface-treated magnetic powder except that zinc sulfate was used as a raw material in addition to ferrous sulfate in Production Example 1 of surface-treated magnetic powder. Thus, a surface-treated magnetic powder 9 was obtained. Table 1 shows the physical properties. (Production example 10 of surface-treated magnetic powder) The same as Production example 1 of surface-treated magnetic powder except that barium sulfate was used as a raw material in addition to ferrous sulfate in Production example 1 of surface-treated magnetic powder. Thus, a surface-treated magnetic powder 10 was obtained. Table 1 shows the physical properties.

[0374]

[Table 1]

(Conductive fine powder 1) Fine particle zinc oxide was subjected to air classification, and the volume average particle size was 2.9 μm, and 3.2% by volume was 0.5 μm or less in particle size distribution, and 0% by number was 5 μm or more.
Of white fine particles of zinc oxide (resistance: 1300 Ω · cm). This is referred to as conductive fine powder 1.

The conductive fine powder 1 was observed at a magnification of 3000 and 30,000 times with a scanning electron microscope.
It consisted of zinc oxide primary particles of 0.3 μm and aggregates of 1 to 5 μm.

Using a light source having a wavelength of 740 nm in accordance with an exposure light wavelength of 740 nm of a laser beam scanner used for image exposure in the image forming apparatus of the embodiment, the transmittance in this wavelength range was measured using a 310T transmission type manufactured by X-Rite. When measured using a densitometer, the transmittance of the conductive fine powder 1 was about 33%.

(Conductive Fine Powder 2) After removing coarse particles of aluminum borate surface-treated with tin oxide / antimony by air classification, and repeatedly dispersing and filtering in an aqueous system to remove fine particles, Average particle size 3.0 μm,
0.5 volume% or less in the particle size distribution is 0.5% by volume, 5μ
m or more was obtained as 1% by number of gray-white conductive particles (resistance 5
0 Ω · cm). This is referred to as conductive fine powder 2.

(Production of Magnetic Toner 1) Ion-exchanged water 70
It was charged 0.1M-Na ₃ PO ₄ aqueous solution 451g to 9 g 6
After heating to 0 ° C., a 1.0 M CaCl ₂ aqueous solution 67.
An aqueous medium containing Ca ₃ (PO ₄ ) ₂ was obtained by adding 7 g.

Styrene 90 parts 2-Ethylhexyl acrylate 10 parts Crosslinking agent: triethylene glycol dimethacrylate 1.0 part Saturated polyester resin 5 parts Load control agent (salicylic acid-based metal compound) 1 part Surface-treated magnetic powder 1 85 parts The above formulation was uniformly dispersed and mixed using an attritor (Mitsui Miike Kakoki Co., Ltd.). The monomer composition was heated to 60 ° C., and 12 parts of an ester wax (80 ° C., the maximum endothermic peak in DSC) was added, mixed and dissolved, and the polymerization initiator 2,2′-azobisisopropane was added thereto. Butyronitrile 5
Parts by weight were dissolved.

The above-mentioned polymerizable monomer system was charged into the above-mentioned aqueous medium, and a TK homomixer (Tokusai Kika Kogyo Co., Ltd.) at 10,000 rpm at 60 ° C. under an N ₂ atmosphere.
The mixture was stirred for 5 minutes and granulated. Thereafter, the mixture was reacted at 60 ° C. for 1 hour while stirring with a paddle stirring blade. After that, the liquid temperature was 80 ° C.
Then, stirring was further continued for 9 hours. After the completion of the reaction, distillation was performed. Thereafter, the suspension was cooled, hydrochloric acid was added to dissolve the dispersant, and the mixture was filtered, washed with water and dried to obtain black particles 1 having a weight average particle size of 6.9 μm.

[0382] 100 parts of the black particles and a primary particle size of 9n
m of silica is treated with hexamethyldisilazane, then treated with silicone oil, and the BET value after the treatment is 200 m
1.2 parts of ² / g hydrophobic silica fine powder, 1 conductive fine powder
Using a Henschel mixer (Mitsui Miike Kakoki Co., Ltd.) for 3 minutes at a peripheral speed of the stirring blade of 40 m / sec, magnetic toner 1 was prepared. Table 2 shows the physical properties of Magnetic Toner 1.

(Production of Magnetic Toner 2) A magnetic toner 2 was obtained in the same manner as in the production example of the magnetic toner 1, except that the polymerization initiator was changed to 4 parts by mass. Table 2 shows the physical properties of Magnetic Toner 2.

(Production of Magnetic Toner 3) A magnetic toner 3 was obtained in the same manner as in the production example of the magnetic toner 1, except that the polymerization initiator was changed to 4 parts by mass and the crosslinking agent was changed to 1.5 parts by mass. Table 2 shows the physical properties of Magnetic Toner 3.

(Production of Magnetic Toner 4)
Magnetic toner 4 was obtained in the same manner as in the production example of magnetic toner 1, except that the parts by mass and the crosslinking agent were changed to 0.1 parts by mass. Table 2 shows the physical properties of Magnetic Toner 4.

(Production of Magnetic Toner 5) The same procedure as in Production Example of Magnetic Toner 1 was carried out except that the polymerization initiator was changed to 3 parts by mass and the crosslinking agent was changed to 1.5 parts by mass, and the temperature was not increased during the reaction. Thus, magnetic toner 5 was obtained. Table 2 shows the physical properties of Magnetic Toner 5.

(Production of Magnetic Toner 6) A magnetic toner 6 was obtained in the same manner as in the production example of the magnetic toner 1, except that the polymerization initiator was changed to 9 parts by mass and the crosslinking agent was changed to 0.07 parts by mass. Table 2 shows the physical properties of the magnetic toner 6.

(Production of Magnetic Toner 7)
Magnetic toner 7 was obtained in the same manner as in the production example of magnetic toner 1, except that 5 parts by mass and the crosslinking agent were changed to 1.7 parts by mass, and the temperature was not increased during the reaction. Table 2 shows the physical properties of Magnetic Toner 7.

(Production of Magnetic Toner 8) A magnetic toner 8 was obtained in the same manner as in the production example of the magnetic toner 1 except that the surface-treated magnetic powder 2 was used and the conductive fine powder 1 was not used.
Table 2 shows the physical properties of the magnetic toner 8.

(Production of Magnetic Toner 9) A magnetic toner 9 was obtained in the same manner as in the production example of the magnetic toner 1 except that the surface-treated magnetic powder 3 was used and the conductive fine powder 1 was not used.
Table 2 shows the physical properties of the magnetic toner 9.

(Production of Magnetic Toner 10) A magnetic toner 10 was obtained in the same manner as in the production example of the magnetic toner 1 except that the surface-treated magnetic powder 4 was used and the conductive fine powder 1 was not used. Table 2 shows the physical properties of the magnetic toner 10.

(Production of Magnetic Toner 11) A magnetic toner 11 was obtained in the same manner as in the production example of the magnetic toner 1 except that the surface-treated magnetic powder 5 was used and the conductive fine powder 1 was not used. Table 2 shows the physical properties of the magnetic toner 11.

(Production of Magnetic Toner 12) A magnetic toner 12 was obtained in the same manner as in the production example of the magnetic toner 1 except that the surface-treated magnetic powder 7 was used and the conductive fine powder 1 was not used. Table 2 shows the physical properties of the magnetic toner 12.

(Production of Magnetic Toner 13) A magnetic toner 13 was obtained in the same manner as in the production example of the magnetic toner 1 except that the surface-treated magnetic powder 8 was used and the conductive fine powder 1 was not used. Table 2 shows the physical properties of the magnetic toner 13.

(Production of Magnetic Toner 14) A magnetic toner 14 was obtained in the same manner as in the production example of the magnetic toner 1 except that the surface-treated magnetic powder 6 was used and the conductive fine powder 1 was not used. Table 2 shows the physical properties of the magnetic toner 14.

(Production of Magnetic Toner 15) Ion-exchanged water 7
After adding 451 g of a 0.1 M Na ₃ PO ₄ aqueous solution to 09 g and heating to 60 ° C., a 1.0 M CaCl ₂ aqueous solution 6 was added.
7.7 g was added to obtain an aqueous medium containing Ca ₃ (PO ₄ ) ₂ .

Styrene 85 parts n-butyl acrylate 15 parts Crosslinking agent: divinylnaphthalene 0.5 parts Saturated polyester resin 20 parts Negative charge control agent (boron metal compound) 1 part Surface-treated magnetic powder 1 80 parts The mixture was uniformly dispersed and mixed using a lighter (Mitsui Miike Kakoki Co., Ltd.). The monomer composition was heated to 60 ° C., and 5 parts of paraffin wax (maximum endothermic peak in DSC: 60 ° C.) was added thereto, mixed and dissolved, and the polymerization initiator 2,2′-azobisisopropane was added thereto. Butyronitrile 5
Parts by weight were dissolved.

The above-mentioned polymerizable monomer system was charged into the above-mentioned aqueous medium, and the mixture was heated at 10,000 rpm at 60 ° C. under a N ₂ atmosphere at 10,000 rpm using a TK homomixer (Tokiki Kika Kogyo Co., Ltd.).
The mixture was stirred for 5 minutes and granulated. Thereafter, the mixture was reacted at 60 ° C. for 5 hours while stirring with a paddle stirring blade.

Next, 20.0 parts by mass of styrene, 2,2 ′
0.4 parts by mass of azobisisobutyronitrile and 0.03 parts by mass of sodium lauryl sulfate were added to 80 parts by mass of water, and dispersed using an ultrasonic homogenizer to obtain a water emulsion.

This was dropped into the above-mentioned magnetic toner particle dispersion and was attached to the particles. Thereafter, the mixture was stirred under a nitrogen atmosphere and reacted at 85 ° C. for 10 hours. After the completion of the reaction, distillation was performed. Thereafter, the suspension was cooled, hydrochloric acid was added to dissolve the dispersant, and the suspension was filtered, washed with water, and dried to obtain black particles having a weight average particle diameter of 7.3 μm.

The black particles (100 parts) had a primary particle size of 9 nm.
Silica is treated with hexamethyldisilazane, then treated with silicone oil, and the BET value after the treatment is 200 m ^2.
The magnetic toner 15 was prepared by mixing 1.2 parts / g of hydrophobic silica fine powder with a Henschel mixer (Mitsui Miike Kakoki Co., Ltd.) for 3 minutes at a peripheral speed of the stirring blade of 40 m / sec. Table 2 shows the physical properties of the magnetic toner 15.

(Production of Magnetic Toner 16) In preparing an aqueous medium, 10 g of calcium carbonate was added to 1200 g of ion-exchanged water.
Was finely dispersed and a magnetic toner 16 was obtained in the same manner as in the production example of the magnetic toner 1 except that the conductive fine powder 1 was not used. Table 2 shows the physical properties of the magnetic toner 16.

(Production of Magnetic Toner 17) A magnetic toner 17 was obtained in the same manner as in the production example of the magnetic toner 1 except that the surface-treated magnetic powder 9 was used. Table 2 shows the physical properties of the magnetic toner 17.

(Production of Magnetic Toner 18) A magnetic toner 18 was obtained in the same manner as in the production example of the magnetic toner 1 except that the surface-treated magnetic powder 10 was used. Table 2 shows the physical properties of the magnetic toner 18.
Shown in

[0405]

[Table 2]

The magnetic field of each magnetic toner was 79.6 k.
The saturation magnetization intensity at A / m is 24 to 26 A
m ² / kg. The residual magnetization of the magnetic toners 1 to 16 at a magnetic field of 79.6 kA / m is ^{2 to 4} Am ^2.
/ Kg, and the residual magnetization of the magnetic toner 17 is 0.4 A
m ² / kg, the residual magnetization of the magnetic toner 18 is 7 Am ² / k
g.

[Example 1] <Production of photoconductor 1> As a photoconductor, Al having a diameter of 30 mm was used.
A cylinder was used as a substrate. Then, layers having the structure shown in FIG. 4 and those shown below were sequentially laminated by dip coating to prepare a photoreceptor 1. (1) Conductive coating layer: Mainly composed of tin oxide and titanium oxide powder dispersed in a phenol resin. 15μ thickness
m. (2) Undercoat layer: mainly composed of modified nylon and copolymerized nylon. The film thickness is 0.6 μm. (3) Charge generation layer: mainly composed of an azo pigment having absorption in a long wavelength region dispersed in butyral resin. Thickness 0.6
μm. (4) Charge transport layer: mainly composed of a hole-transporting triphenylamine compound dissolved in a polycarbonate resin (molecular weight 20,000 according to Ostwald viscosity method) at a mass ratio of 8:10, and further a polytetrafluoroethylene powder ( Particle size 0.2
μm) was added at 10% by mass based on the total solid content, and the mixture was uniformly dispersed. 25 μm thick. The contact angle with water was 95 degrees. The contact angle was measured using pure water, and the apparatus used was a contact angle meter CA-X of Kyowa Interface Science Co., Ltd.

<Image Forming Apparatus> As the image forming apparatus, L
BP-1760 was modified to use the same one as in the above embodiment shown in FIG. Photoreceptor 10 as image carrier
For 0, the above-mentioned photoreceptor 1 was used.

A primary charging roller (rubber roller charger) 117 in which conductive carbon is dispersed and coated with a nylon resin as a charging member is brought into contact with the photosensitive member (contact pressure: 60 g).
/ Cm), DC voltage -680Vdc and AC voltage 2.0k
A bias on which Vpp is superimposed is applied to uniformly charge the photosensitive member. Following charging, an electrostatic latent image is formed by exposing the image portion with a laser beam. At this time, the dark part potential Vd = -680 V and the light part potential VL = -150 V.

The gap between the photosensitive drum and the developing sleeve is 23
0 μm, and as a magnetic toner carrier, a layer thickness of about 7 μm having the following configuration and a JIS center line average roughness (Ra) of 1.0 were formed on a 16 mm diameter aluminum cylinder having a blasted surface.
Using the developing sleeve 102 on which a resin layer of μm is formed,
A urethane blade having a developing magnetic pole of 85 mT (850 gauss) and a thickness of 1.0 mm and a free length of 0.5 mm as a toner regulating member was brought into contact with a linear pressure of 34.3 N / m (35 g / cm).・ Phenol resin 100 parts by mass ・ Graphite (particle size: about 7 μm) 90 parts by mass ・ Carbon black 10 parts by mass

Next, a DC voltage Vd is used as a developing bias.
c = −450 V, 5.22 × 1 as a superposed alternating electric field
0 ⁶ V / m, was used in the frequency 2400 Hz. The peripheral speed of the developing sleeve is the peripheral speed of the photoconductor (198 mm / s).
ec) in the forward direction at a speed of 110% (218 m
m / sec).

The transfer roller 114 may be a transfer roller as shown in FIG. 3 (made of ethylene-propylene rubber in which conductive carbon is dispersed, and has a volume resistivity of 10 ^{8 of} a conductive elastic layer).
Ωcm, surface rubber hardness 24 °, diameter 20 mm, contact pressure 5
9 N / m (60 g / cm)) was made equal to the peripheral speed (94 mm / sec) of the photosensitive member in the direction A in FIG. 3, and the transfer bias was DC 1.5 kV.

[0413] As a fixing method, a fixing roller having a surface layer made of a fluorine-based resin and a pressure roller,
6 was used. The diameter of the roller was 30 mm, the fixing temperature was 220 ° C., and the nip width was 8 mm.

Using Magnetic Toner 1, under a normal temperature and normal humidity environment (25 ° C., 60% RH), an image forming test of 5000 sheets was performed with an image pattern consisting of only vertical lines having a printing rate of 2%. Note that 80 g / m ² paper was used as a recording medium. Further, after the initial image formation, a halftone image was obtained using 105 g paper, and the fixing property was evaluated. As a result, the magnetic toner 1 exhibited high transferability in the initial stage, and obtained a good image without any omission or ghost during transfer. The fixing property was also good, and no offset occurred. Table 3 shows the evaluation results.

The evaluation items described in the examples and comparative examples of the present invention and the criteria thereof are described below.

<Measurement of Amount of Frictional Charge of Toner on Developing Sleeve> The amount of triboelectric charge of the toner on the developing sleeve is obtained by using a suction type Faraday gauge method. In this suction type Faraday gauge method, the outer cylinder is pressed against the surface of the developing sleeve to suck toner on a certain area on the developing sleeve,
The weight of the sucked toner can be calculated from the increase in the weight of the filter collected in the filter of the inner cylinder. At the same time, by measuring the amount of electric charge accumulated in the inner cylinder electrostatically shielded from the outside, the amount of triboelectric charge of the toner on the developing sleeve can be obtained.

<Image Density> The image density was measured by forming a solid image portion and measuring the solid image with a Macbeth reflection densitometer (manufactured by Macbeth).

<Image Quality> The image quality determination criteria are based on comprehensive evaluation of image uniformity and fine line reproducibility. In addition,
The uniformity of the image is determined based on the uniformity of the solid black image and the halftone image. A: A clear image with excellent fine line reproducibility and image uniformity. B: A good image, although the reproducibility of fine lines and the uniformity of the image are slightly inferior. C: Practical image quality without any problem. D: Fine line reproducibility and image uniformity are poor, and the image is not preferable for practical use.

<Fog on Photoconductor> Fog on the photoconductor was measured using REFLECTMETER MODEL TC-6DS manufactured by Tokyo Denshoku Co., Ltd. The filter used was a green filter, and the fog on the photoreceptor was calculated by the following equation.

(Equation 10)

The criteria for determining fog on the photoreceptor are as follows. A: Very good (less than 2.0%) B: Good (more than 2.0% and less than 4.0%) C: Normal (more than 4.0% and less than 6.0%) D: Bad (6. 0% or more)

<Fixing Property> The fixing property was evaluated by applying a load of 50 g / cm ² , rubbing the fixed image five times with soft thin paper, and reducing the image density before and after rubbing (%). A: less than 10% B: 10% or more and less than 20% C: 20% or more and less than 30% D: 30% or more

<Offset Resistance> The offset resistance was evaluated by the degree of stain on the image and the back of the paper after the durability test. A: No stain is generated. B: Stain is slightly observed. C: Some stains are observed. D: Remarkable dirt is generated.

[Examples 2 to 9] Image output tests and durability evaluations were performed under the same conditions as in Example 1 using magnetic toners 2, 3 and 8 to 13 as toners. As a result, there was no problem in the initial image characteristics, and no problem was found in any case up to 5000 sheets. Table 3 shows the results.

[Comparative Example 1] Magnetic toner 4 was used as toner.
And an image formation test and durability evaluation were performed in the same image forming method as in Example 1. As a result, the image density, the chargeability, and the fog of the photoreceptor deteriorated. This is presumably because the melt viscosity of the toner was low, and the release rate of iron and iron compounds changed due to durability. In addition, the offset resistance also deteriorated. Table 3 shows the results.

[Comparative Example 2] Magnetic toner 5 was used as toner.
And an image formation test and durability evaluation were performed in the same image forming method as in Example 1. As a result, no problems occurred in the image density, the charging property, and the fogging of the photoreceptor, but the fixing property deteriorated. This is probably because the melt viscosity of the toner is high. Table 3 shows the results.

[Comparative Example 3] Magnetic toner 6 was used as toner.
And an image formation test and durability evaluation were performed in the same image forming method as in Example 1. As a result, the image density, the chargeability, and the fog of the photoreceptor deteriorated. This is presumably because the melt viscosity of the toner was low, and the release rate of iron and iron compounds changed due to durability. In addition, the offset resistance was significantly deteriorated. Table 3 shows the results.

[Comparative Example 4] Magnetic toner 7 was used as toner.
And an image formation test and durability evaluation were performed in the same image forming method as in Example 1. As a result, no problem occurred in the image density, the charging property, and the fog of the photosensitive member, but the fixing property and the offset resistance were deteriorated. This is probably because the wax in the toner could not function sufficiently because the melt viscosity of the toner was high. Table 3 shows the results.

[Comparative Example 5] Magnetic toner 1 was used as the toner.
Using No. 4, an image formation test and durability evaluation were performed in the same image forming method as in Example 1. As a result, image quality,
The chargeability and fog of the photoreceptor were poor. This is thought to be due to the high release rate of iron and iron compounds. In addition, the fixing property was slightly deteriorated. Table 3 shows the results.

[Comparative Example 6] Magnetic toner 1 was used as toner.
Using No. 5, an image formation test and durability evaluation were performed by the same image forming method as in Example 1. As a result, image quality,
Photoreceptor fog is slightly bad. Image quality declined due to charge-up during durability. This is probably because the toner has a low release rate of iron and iron compounds. In addition, the fixing property was slightly deteriorated. Table 3 shows the results.

[Comparative Example 7] Magnetic toner 1 was used as toner.
Using No. 6, an image formation test and durability evaluation were performed in the same image forming method as in Example 1. As a result, image quality,
Photoreceptor fog was bad. This is considered because the circularity of the toner is low and the weight average particle diameter / number average particle diameter is high. Table 3 shows the results.

[Embodiment 10] The magnetic toner of the present invention is also applicable to a cleanerless image forming method or a developing and cleaning (collecting) image forming method. Hereinafter, the image forming method of the present invention will be described with reference to specific examples, but the present invention is not limited thereto.

<Production of Photoreceptor 2> The photoreceptor is a photoreceptor using an organic photoconductive substance for negative charging, and has a base made of an aluminum cylinder having a diameter of 30 mm. A layer having the structure shown in FIG. 5 and the structure shown below was successively laminated by dip coating thereon, to thereby produce a photoreceptor 2. (1) The first layer is a conductive layer, and is a conductive particle-dispersed resin layer having a thickness of about 20 μm, which is provided to smooth defects of the aluminum substrate and to prevent the occurrence of moire due to reflection by laser exposure. (Mainly one in which tin oxide and titanium oxide powders are dispersed in a phenol resin). (2) The second layer is a positive charge injection preventing layer (undercoat layer),
It serves to prevent the positive charge injected from the aluminum support from canceling the negative charge charged on the surface of the photoreceptor, and has a medium resistance of about 1 μm and a resistance adjusted to about 10 ⁶ Ωcm by methoxymethylated nylon. Layer. (3) The third layer is a charge generation layer, which is a layer having a thickness of about 0.3 μm in which a disazo pigment is dispersed in butyral resin, and generates a positive and negative charge pair by receiving laser exposure. (4) The fourth layer is a charge transport layer, a layer having a thickness of about 25 μm in which a hydrazone compound is dispersed in a polycarbonate resin, and is a P-type semiconductor. Therefore, the negative charges charged on the photoreceptor surface cannot move through this layer, and only the positive charges generated in the charge generation layer can be transported to the photoreceptor surface. (5) The fifth layer is a charge injection layer, in which a photo-curable acrylic resin is made of conductive tin oxide ultrafine particles and has a particle size of about 0.25 μm.
Are dispersed. Specifically, tin oxide particles (conductive particles) having a particle diameter of about 0.03 μm (conductive particles) doped with antimony and having a low resistance are 100% by mass with respect to the resin, and 2% by weight of ethylene tetrafluoride resin particles.
0% by mass, and 1.2% by mass of a dispersant.
The coating liquid thus prepared was applied to a thickness of about 2.5 μm by a spray coating method, and was cured by light irradiation to form a charge injection layer. The resistance of the surface of the obtained photoreceptor is 5 × 10
^The contact angle of water on the photoreceptor surface was ¹² Ωcm.

<Production of Charging Member> Diameter 6 mm, length 26
A 4mm SUS roller is used as a core metal, and a medium-resistance urethane foam layer containing urethane resin, carbon black as conductive particles, a sulfide agent, a foaming agent, etc. is formed on the core metal in a roller shape, and further cut and polished. A charging roller having a diameter of 12 mm and a length of 234 mm, which is a flexible member, was prepared with its shape and surface properties adjusted. The obtained charging roller has a resistance of 10 ⁵
Ωcm, and the hardness was 30 degrees in Asker C hardness. When the surface of the charging roller was observed with a scanning electron microscope, the average cell diameter was about 100 μm, and the porosity was 60%.

<Image Forming Apparatus> FIG. 6 is a schematic structural diagram of an example of an image forming apparatus according to the present invention. The image forming apparatus used in the tenth embodiment is a laser printer (recording apparatus) of a developing and cleaning process (cleanerless system) using a transfer type electrophotographic process. It has a process cartridge from which a cleaning unit having a cleaning member such as a cleaning blade is removed, uses magnetic toner 1 as magnetic toner, and is arranged so that the toner layer on the magnetic toner carrier and the image carrier are not in contact with each other. This is an example of non-contact development performed. As a fixing method, a fixing device 26 of a type in which heating and pressure are fixed by a heater via a film was used. The pressure roller used has a surface layer of a fluororesin, and the diameter of the roller is 30 mm.
The fixing temperature was set at 230 ° C., and the nip width was set at 6 mm.

(1) Overall Schematic Configuration of Printer In this embodiment, a rotating drum type OPC photosensitive member 21 using the photosensitive member 2 as an image carrier is 198 mm / sec in the X direction of the arrow.
It is driven to rotate at a peripheral speed (process speed) of c.

The charging roller 22, which is the charging member as a contact charging member, is disposed so as to be pressed against the photosensitive member 21 with a predetermined pressing force against elasticity. n is the photoreceptor 21
And a contact portion of the charging roller 22. In this example, the charging roller 22 is rotationally driven at a peripheral speed of 100% in the facing direction (the direction of the arrow Y) at the contact portion n which is the contact surface with the photoconductor 21. That is, the surface of the charging roller 22 as a contact charging member has a speed difference from the surface of the photoconductor 21. Further, the amount of application is approximately 1 × 1 on the surface of the charging roller 22.
0 ⁴ / mm ² was coated with the conductive fine powder 1 to be uniform in.

Further, a DC voltage of -700 V was applied as a charging bias from a charging bias applying power source to the core metal 22a of the charging roller 22. In this embodiment, the surface of the photoconductor 21 is uniformly charged by a direct injection charging method to a potential (−680 V) substantially equal to the voltage applied to the charging roller 22. This will be described later.

Reference numeral 23 denotes a laser beam scanner (exposure device) including a laser diode, a polygon mirror, and the like. This laser beam scanner outputs a laser beam whose intensity is modulated in accordance with a time-series electric digital pixel signal of target image information, and scans and exposes the uniformly charged surface of the photoconductor 21 with the laser beam. By this scanning exposure L, an electrostatic latent image corresponding to the target image information is formed on the surface of the rotating photoconductor 21.

Reference numeral 24 denotes a developing device. The electrostatic latent image on the surface of the photoconductor 21 is developed as a toner image by this developing device. The developing device 24 of the present embodiment is a non-contact type reversal developing device using the magnetic toner 1 used in Embodiment 1 as the magnetic toner. A conductive fine powder 1 is externally added to the magnetic toner 1.

The gap between the photosensitive drum 21 and the developing sleeve 24a is 230 μm, and the magnetic toner carrier 24a is formed on a 16 mm diameter aluminum cylinder whose surface is blasted, and has the following JIS center line average roughness (Ra).
A developing sleeve having a 1.0 μm resin layer (layer thickness: about 7 μm) was used, a magnet roll having a developing magnetic pole of 85 mT (850 gauss) was included, and a 1.0 mm thick elastic blade 24 c serving as a magnetic toner layer regulating member was used. And a 0.5 mm free length urethane blade at 34.3 N / m (3
(5 g / cm).・ Phenol resin 100 parts by mass ・ Graphite (particle size: about 7 μm) 90 parts by mass ・ Carbon black 10 parts by mass

Further, in the developing section a (developing area) which is a portion facing the photoconductor 21, a circumferential direction of 120% of the peripheral speed of the photoconductor 21 in the forward direction (direction of arrow W) with respect to the rotation direction of the photoconductor 21 Rotate at high speed. The elastic blade 2 is attached to the developing sleeve 24a.
4c coats the magnetic toner in a thin layer. The layer thickness of the magnetic toner with respect to the developing sleeve 24a is regulated by the elastic blade 24c, and an electric charge is applied. At this time, the amount of magnetic toner coated on the developing sleeve 24a is 15 g /
m ² .

The magnetic toner coated on the developing sleeve 24a is conveyed by the rotation of the developing sleeve 24a to the developing section a which is the opposing portion of the photosensitive member 21 and the developing sleeve 24a. A developing bias voltage is applied to the developing sleeve 24a from a developing bias applying power source. The developing bias voltage is a DC voltage of -450 V, a frequency of 1800 Hz,
Using a superposed alternating electric field of 5.22 × 10 ⁶ V / m, one-component jumping development was performed between the developing sleeve 24a and the photoconductor 21a.

The transfer roller 25 of medium resistance as a contact transfer means is pressed against the photosensitive member 21 with a linear pressure of 98 N / m (100 g / cm) to form a transfer nip b. A transfer material P as a recording medium is supplied to the transfer nip b from a paper supply unit (not shown) at a predetermined timing, and a predetermined transfer bias voltage is applied to a transfer roller 25 from a transfer bias application power supply. Then, the toner image on the photoconductor 21 side is sequentially transferred to the surface of the transfer material P fed to the transfer nip portion b.

In this example, the roller resistance value is 5 × 10 ⁸ Ωcm
The transfer was performed by applying a DC voltage of +3000 V. That is, the transfer material (recording medium) P introduced into the transfer nip portion b is conveyed by nipping the transfer nip portion b, and the toner images formed and carried on the surface of the photoreceptor 21 on the surface thereof are sequentially electrostatically charged. It is transferred by force and pressing force.

Reference numeral 26 denotes a fixing device such as a heat fixing method. The transfer material P fed to the transfer nip portion b and having received the transfer of the toner image on the photoconductor 21 is separated from the surface of the photoconductor 1 and introduced into the fixing device 26, where the toner image is fixed and the image is formed. It is discharged out of the apparatus as a formed product (print, copy).

In the printer of this embodiment, the cleaning unit is removed, and the transfer residual toner remaining on the surface of the photoconductor 21 after the transfer of the toner image to the transfer material P is not removed by the cleaner, and the rotation of the photoconductor 21 is performed. Accordingly, the developer reaches the developing unit a via the charging unit n, and is developed and cleaned (collected) in the developing unit 24.

A process cartridge 27 is detachable from the printer main body. In the printer of the present embodiment, the three process devices of the photoreceptor 21, the charging roller 22, and the developing device 24 are collectively configured as a process cartridge that is detachable from the printer main body. The combination of the process devices to be formed into the process cartridge is not limited to the above, and is optional. Reference numeral 28 denotes a process cartridge attachment / detachment / holding member.

(2) Behavior of the conductive fine powder in this embodiment The conductive fine powder mixed with the magnetic toner in the developing device 24 is developed by the developing device 24 into a toner image of the electrostatic latent image on the photosensitive member 21 side. At the same time, an appropriate amount moves to the photoconductor 21 side together with toner.

The toner image on the photoreceptor 21 is attracted to the transfer material P, which is a recording medium, by the influence of the transfer bias in the transfer portion b and is positively transferred. Due to the nature, it does not positively transfer to the transfer material P side, and remains substantially adhered and held on the photoconductor 21.

In this embodiment, since the image forming apparatus has no cleaning step, the transfer residual toner remaining on the surface of the photoreceptor 21 after the transfer and the above-mentioned residual conductive fine powder are in contact with the photoreceptor 21 and the contact charging member. Is carried as it is by the movement of the surface of the photoconductor 21 to the charging portion n which is a contact portion of the charging roller 22, and adheres or mixes with the charging roller 22. Therefore, direct injection charging of the photoconductor 21 is performed in a state where the conductive fine powder is present at the contact portion n between the photoconductor 21 and the charging roller 22.

Since the presence of the conductive fine powder can maintain the close contact property and contact resistance of the charging roller 22 with the photoreceptor 21 even when toner adheres or mixes with the charging roller 22, To charge the photoconductor 21 directly.

That is, the charging roller 22 comes into close contact with the photoconductor 21 via the conductive fine powder, and the conductive fine powder existing on the mutual contact surface between the charging roller 22 and the photoconductor 21 cleans the surface of the photoconductor 21. By rubbing without gaps, the charging of the photoreceptor 21 by the charging roller 22 becomes stable and safe by direct injection charging without using a discharge phenomenon due to the presence of the conductive fine powder, and can be obtained by conventional roller charging or the like. Thus, a high charging efficiency can be obtained, and a potential substantially equal to the voltage applied to the charging roller 22 can be given to the photoconductor 21.

The transfer residual toner adhering to or mixed in the charging roller 22 is gradually discharged from the charging roller 22 onto the photosensitive member 21 and moves to the developing section as the photosensitive member 21 moves, and is developed and cleaned (collected) by the developing means. ) Is done.

In the development and cleaning, the photosensitive member 2 is transferred after the transfer.
The toner remaining on 1 is developed during a subsequent image forming process, that is, the photosensitive member is continuously charged and exposed to form a latent image, and at the time of developing the latent image, a fogging bias of a developing device, The fogging potential difference Vback, which is the potential difference between the DC voltage applied to the container and the surface potential of the photosensitive member, is collected. In the case of the reversal development as in the printer in this embodiment, the development and cleaning is performed by an electric field for collecting the toner from the dark portion potential of the photoconductor by the developing bias to the developing sleeve and a toner from the developing sleeve to the bright portion potential of the photoconductor. Is caused by the action of an electric field that causes

[0455] Also, by operating the image forming apparatus,
The conductive fine powder mixed into the magnetic toner of the developing device 24 moves to the surface of the photoreceptor 21 in the developing section a, is carried to the charging section n via the transfer section b by the movement of the image bearing surface, and is charged by the charging section n. n
Since the new conductive fine powder is continuously supplied to the charging portion n, it is possible to prevent the conductive fine powder from being reduced due to falling off or the like or to be deteriorated when the charging is performed. As a result, good chargeability is stably maintained.

Thus, in the image forming apparatus of the contact charging system, the transfer system, and the toner recycling process, the simple charging roller 22 is used as the contact charging member, and the charging roller 22 is kept low regardless of the contamination by the transfer residual toner. Ozone-less direct injection charging can be stably maintained over a long period of time with an applied voltage, uniform charging properties can be provided, and there is no obstacle due to ozone products, poor charging, etc., simple configuration, low cost It is possible to obtain a simple image forming apparatus.

In addition, as described above, the conductive fine powder must have an electric resistance value of 1 × 10 ⁹ Ωcm or less in order not to impair the chargeability. Therefore, in the case of using a contact developing device in which the magnetic toner directly contacts the photoconductor 21 in the developing unit a, the charge is injected into the photoconductor 21 by the developing bias through the conductive fine powder in the developing agent, and the image fogging is performed. Will occur.

However, in this embodiment, since the developing device is a non-contact type developing device, a good image can be obtained without a developing bias being injected into the photosensitive member 21. In addition, since charge injection to the photoconductor 21 does not occur in the developing unit a,
It is possible to provide a high potential difference between the developing sleeve 24a and the photoconductor 21 such as an AC bias, and the conductive fine powder is easily developed uniformly, and the conductive fine powder is uniformly applied to the surface of the photoconductor 21; Uniform contact can be made at the charging section, good charging properties can be obtained, and good images can be obtained.

The contact surface n between the charging roller 22 and the photosensitive member 21
With the conductive fine powder interposed therebetween, it is possible to easily and effectively provide a speed difference between the charging roller 22 and the photoconductor 21 due to the lubricating effect (friction reducing effect) of the conductive fine powder. .

By providing a speed difference between the charging roller 22 and the photosensitive member 21, the chance of contact of the conductive fine powder with the photosensitive member 21 at the mutual contact surface n between the charging roller 22 and the photosensitive member 21 is greatly increased. As a result, a high contact property can be obtained, and good direct injection charging can be achieved.

In the present embodiment, the charging roller 22 is driven to rotate, and the rotation direction thereof is configured to rotate in the direction opposite to the moving direction of the surface of the photosensitive member 21, so that the photosensitive member carried to the charging section n An effect of temporarily collecting the transfer residual toner on the charging roller 21 to the charging roller 22 and leveling the toner is obtained. That is, it is possible to perform direct injection charging by dominating the transfer residual toner on the photoconductor 21 once by rotating in the reverse direction and performing charging.

Further, in this embodiment, a suitable amount of conductive fine powder is interposed in the contact portion n between the photosensitive drum 21 as an image carrier and the charging roller 22 as a contact charging member, so that the conductive fine powder is used. Charge roller 22 due to lubrication effect
It is easy to reduce the friction between the photosensitive drum 21 and the photosensitive drum 21 and to rotate the charging roller 22 to rotate the photosensitive drum 21 with a speed difference. That is, the driving torque is reduced, and the surfaces of the charging roller 22 and the photosensitive drum 21 can be prevented from being scraped or damaged. Further, sufficient charging performance can be obtained by increasing the contact chance by the particles. In addition, there is no adverse effect on image formation due to the conductive fine powder falling off the charging roller 22.

(3) Evaluation In this example, an image forming test was performed using the magnetic toner 1 under a normal temperature and normal humidity environment (25 ° C., 60% RH). For the photoreceptor, the volume resistance of the outermost layer is 5 × 10 ¹² Ω
cm of the above photoreceptor 2 and a transfer material of 80 g /
Using the paper m ^2. In the initial image characteristics, no fog due to poor charging was observed, and a good image density with high resolution was obtained. At this time, the photoreceptor potential after the direct injection charging was -680 V with respect to the applied charging bias of -700 V. Next, durability was evaluated using an image pattern consisting of only vertical lines having a printing rate of 2%. As a result, image defects caused by poor charging do not occur until after printing 5,000 sheets,
Good direct injection chargeability was obtained.

The potential of the photoreceptor after direct injection charging after printing 5,000 sheets is -655 V with respect to the applied charging bias of -700 V, and the chargeability from the initial stage is reduced by 25%.
V, which was slight, and no deterioration in image quality due to a decrease in chargeability was observed. Table 3 shows the obtained results. In addition,
The evaluation items and evaluation criteria are the same as in Example 1. The amount of the conductive fine powder in the contact portion between the image bearing member and the contact charging member was measured by the method described above.
0 was ^five.

Example 11 In Example 10, the same evaluation was performed using the magnetic toner 17, and no fog due to poor charging was observed in the initial image characteristics, and high resolution was obtained. Good image density was obtained. At this time, the photoreceptor potential after direct injection charging is equal to the applied charging bias minus
It was -680V with respect to 700V. Next, the printing rate 2
The durability was evaluated using an image pattern consisting of only% vertical lines. As a result, some fog occurred after printing 5,000 sheets. The amount of the conductive fine powder in the contact portion between the image carrier and the contact charging member was 2 × 10 ⁵ when measured by the above-described method.

[Example 12] In Example 10, the same evaluation was performed using the magnetic toner 18. In the initial image characteristics, no fog caused by poor charging was observed, and the resolution was high. Good image density was obtained. At this time, the photoconductor potential after the direct injection charging is equal to the applied charging bias minus.
It was -680V against 700V. Next, the printing rate 2
The durability was evaluated using an image pattern consisting of only% vertical lines. As a result, image defects due to scratches on the photoreceptor occurred after printing 5,000 sheets, although the level was not a problem in practical use. The amount of the conductive fine powder in the contact portion between the image carrier and the contact charging member was 2 × 10 ⁵ when measured by the above-described method.

[0467]

[Table 3]

[0468]

The magnetic toner of the present invention contains at least toner particles having a binder resin, a release agent, and a magnetic powder, has a weight average particle diameter of 3 to 20 μm, and has a magnetic field of 79.6.
Magnetization intensity at kA / m is 10 to 50 Am ² / kg
The average circularity is 0.970 or more, the ratio of the weight average particle diameter to the number average particle diameter is 1.40 or less, and the free ratio of iron and iron compound is 0.0
5% to 3.00%, and the temperature at which the viscosity measured by a flow tester is 1.0 × 10 ⁵ Pa · s is 80 to 120.
° C and a temperature of 1.0 × 10 ⁴ Pa · s is 1
Since it is from 00 to 150 ° C., it has good fixability,
It is excellent in charge stability, has high image density even after long-term use, and can provide high-definition images.

Further, the magnetic toner of the present invention is
Viscosity of 1.0 × 10^FiveTemperature at which Pa · s
Is 80 to 110 ° C., and the viscosity is 1.0 ×
10 ^FourTemperature at which Pa · s is 100 to 140 ° C
To achieve a good balance between fixability and chargeability.
Is even more effective.

The magnetic toner of the present invention is excellent in reproducibility when the mode circularity is 0.99 or more and the ratio of the weight average particle diameter to the number average particle diameter is 1.35 or less. It is even more effective in obtaining high quality images.

Further, the magnetic toner of the present invention has a release rate of iron and an iron compound of 0.05% to 2.00%, more preferably 0.05% to 1.50%, and further preferably 0.1% to 1.50%.
When the content is from 0.05% to 1.00%, the charging uniformity of the magnetic toner is improved, and the effect of suppressing the roughness of the image is further improved.

Further, when the magnetic toner of the present invention contains a release agent in a total amount of 1 to 30% by mass based on the binder resin, it is more effective in achieving both high-quality image formation and fixability. It is.

Further, in the magnetic toner of the present invention, when the endothermic peak of the release agent by differential thermal analysis is 40 to 110 ° C., more preferably 50 to 100 ° C., the balance of the fixing property is further improved. It is effective.

Further, the magnetic toner of the present invention has a molecular weight of 50 in the molecular weight distribution measured by gel permeation chromatography of the THF-soluble portion of the magnetic toner.
If the peak top of the main peak exists in the range of 00 to 50,000, it is more effective in improving the stability and fixability of the magnetic toner, the uniformity of the shape and particle size distribution of the toner particles, and the like.

Further, the magnetic toner of the present invention has an inorganic fine powder on the surface of toner particles, and the number average primary particle diameter of the inorganic fine powder is 4 to 80 nm, and the inorganic fine powder is silica, titanium oxide, At least one selected from alumina, particularly silica, is more effective in improving the fluidity of the magnetic toner.

The magnetic toner of the present invention is preferably prepared by treating the inorganic fine powder with a hydrophobic treatment, more preferably at least a treatment with a silicone oil, and further preferably at least simultaneously with a treatment with a silane compound or thereafter. When treated with silicone oil, it is even more effective in maintaining the chargeability of the toner particles in a high humidity environment.

Further, in the magnetic toner of the present invention, the inorganic fine powder is silica, and the release rate of the silica is 0.1 to 2.0.
%, More preferably 0.1 to 1.5%, is more effective in maintaining good fluidity of the magnetic toner.

Further, when the magnetic toner of the present invention has conductive fine powder having a volume average particle size smaller than the weight average particle size of the magnetic toner on the surface of the toner particles, the developability of the magnetic toner is improved and the image density is improved. Is more effective in obtaining an image having a high image quality.

Further, in the magnetic toner of the present invention, the resistance of the conductive fine powder is 1 × 10 ⁹ Ωcm or less, more preferably 1 × 10 ⁹ Ωcm.
When the resistivity is 10 ⁸ Ωcm or less, it is more effective in improving the contact property at the contact portion between the image carrier and the charging member and realizing good charging.

Further, the magnetic toner of the present invention is more effective in improving the transportability to the above-mentioned contact portion if the conductive fine powder is non-magnetic.

Further, in the magnetic toner of the present invention, when the release rate of the conductive fine powder is 5.0 to 50.0%,
It is more effective in improving the developability of the magnetic toner and obtaining an image with a high image density.

Further, when the magnetic toner of the present invention has a volume average particle diameter of 0.05 to 0.40 μm, it is more effective in dispersing the magnetic powder in the toner particles well. It is.

Further, in the magnetic toner of the present invention, when the volume average variation coefficient is 35 or less in the particle size distribution of the magnetic powder, it is even more effective in uniforming the content of the magnetic powder between toner particles. It is effective.

Further, in the magnetic toner of the present invention, the magnetic powder is preferably subjected to a hydrophobic treatment with a coupling agent, and more preferably, the surface treatment is carried out by hydrolyzing the coupling agent in an aqueous medium. It is even more effective in obtaining the desired shape and surface condition of the toner particles.

The image forming method of the present invention includes a magnetic one-component developing system, a contact charging system, a contact transfer system, and a toner recycling process as a contact charging method using the magnetic toner of the present invention. In this case, since the performance of the magnetic toner does not deteriorate, a good image can be stably obtained over a long period of time even in repeated use.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of an image forming apparatus that performs an image forming method of the present invention.

FIG. 2 is a diagram showing an example of a developing device for one-component development used in the image forming apparatus shown in FIG.

FIG. 3 is a diagram illustrating an example of a contact transfer member used in an image forming apparatus for performing the image forming method of the present invention.

FIG. 4 is a diagram showing an example of an image carrier used in the image forming method of the present invention.

FIG. 5 is a diagram illustrating an example of a layer configuration of an image carrier used in the image forming method of the present invention.

FIG. 6 is a diagram illustrating another example of an image forming apparatus that performs the image forming method of the present invention.

[Explanation of symbols]

 Reference Signs List 11 aluminum base 12 conductive layer 13 positive charge injection preventing layer 14 charge generation layer 15 charge transport layer 16 charge injection layer 16a conductive particles (conductive filler) 21, 100 photoconductor (image carrier) 22 charging roller (charging member) 22a 34a Core metal 23, 121 Laser beam scanner 24, 140 Developing device 24a, 102 Developing sleeve (magnetic toner carrier) 24b, 141 Stirring member 24c, 103 Elastic blade 25, 34, 114 Transfer roller 26, 126 Fixing device 26a Heater 26b Fixing film 26c Pressure roller 27 Process cartridge 28 Cartridge holding member 34b Conductive elastic layer 35 Transfer bias power supply 104 Magnet roller 116 Cleaner 117 Primary charging roller (charging member) 123 Laser beam 124 Register roller 12 5 Conveyor belt P Recording medium

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) G03G 9/08 374 G03G 9/08 375 375 15/02 101 15/02 101 15/06 101 15/06 101 15/08 506A 15/08 506 9/08 101 507 302 15/08 507B (72) Inventor Tatehiko Chiba 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Michihisa Magome Ota-ku, Tokyo 3-30-2 Shimomaruko Canon Inc. (72) Inventor Keiji Kawamoto 3-30-2 Shimomaruko Shimomaruko, Ota-ku, Tokyo (72) Inventor Akira Hashimoto 3-30 Shimomaruko, Ota-ku, Tokyo No. 2 Canon Inc. (72) Inventor Takeshi Kaburagi 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term (reference) 2H003 BB11 CC05 CC06 DD03 2H005 AA02 AA03 AA06 AA08 AA15 AB02 CA12 CA14 CA26 CB02 CB07 CB13 DA07 DA09 EA01 EA02 EA03 EA05 EA06 EA07 EA10 FA06 2H0 68 AA05 AA06 AA08 BB03 BB31 BB32 CA37 FC01 FC08 FC15 2H073 BA03 BA13 BA43 CA02 2H077 AA37 AC16 AD06 AD36 BA07 EA13 EA16 GA03

Claims (53)

[Claims] 1. A toner having at least a binder resin, a release agent and toner particles having a magnetic powder, and having a weight average particle size of 3 to 2
A magnetic toner having a magnetic intensity of 10 to 50 Am ² / kg in a magnetic field of 79.6 kA / m, wherein the average circularity of the magnetic toner is 0.970 or more; The ratio of the weight average particle diameter to the diameter is 1.40 or less, the release rate of iron and iron compounds of the magnetic toner is 0.05% to 3.00%, and the viscosity of the magnetic toner measured by a flow tester. Is 1.0 ×
The temperature at which 10 ⁵ Pa · s is 80 to 120 ° C. and the temperature at which 1.0 × 10 ⁴ Pa · s is 100 to 150 ° C.
C. A magnetic toner characterized in that the temperature is C. 2. The temperature at which the viscosity of the magnetic toner measured by a flow tester is 1.0 × 10 ⁵ Pa · s is from 80 to 1
The magnetic toner according to claim 1, wherein the temperature is 10C. 3. A temperature at which the viscosity of the magnetic toner measured by a flow tester is 1.0 × 10 ⁴ Pa · s is from 100 to 100 ° C.
The magnetic toner according to claim 1, wherein the temperature is 140C. 4. The magnetic toner has a mode circularity of 0.9.
The magnetic toner according to claim 1, wherein the number is 9 or more. 5. The magnetic toner according to claim 1, wherein a ratio of a weight average particle diameter to a number average particle diameter of the magnetic toner is 1.35 or less. 6. The magnetic toner according to claim 1, wherein the magnetic toner has a release rate of iron and an iron compound of 0.05% to 2.00%. 7. The magnetic toner according to claim 1, wherein a release rate of iron and an iron compound of the magnetic toner is 0.05% to 1.50%. 8. The magnetic toner according to claim 1, wherein the magnetic toner has a release ratio of iron and an iron compound of 0.05% to 1.00%. 9. The magnetic toner according to claim 1, wherein the magnetic toner contains a release agent in a total amount of 1 to 30% by mass based on a binder resin. 10. The magnetic toner according to claim 1, wherein an endothermic peak of the release agent by differential thermal analysis is 40 to 110 ° C. 11. The magnetic toner according to claim 1, wherein an endothermic peak of the release agent by differential thermal analysis is 50 to 100 ° C. 12. The magnetic toner according to claim 1, wherein the magnetic toner has a TH.
In the molecular weight distribution measured by gel permeation chromatography of the F-soluble component, the molecular weight was 5,000 to 5,000.
The magnetic toner according to claim 1, wherein the main peak has a peak top in a range of 50,000. 13. The magnetic toner according to claim 1, wherein the magnetic toner has an inorganic fine powder on a surface of the toner particle, and a number average primary particle diameter of the inorganic fine powder is 4 to 80 nm. The magnetic toner according to claim 1. 14. The magnetic toner according to claim 13, wherein the inorganic fine powder is at least one or more inorganic fine powders selected from silica, titanium oxide, and alumina. 15. The magnetic toner according to claim 13, wherein the inorganic fine powder is silica. 16. The magnetic toner according to claim 13, wherein the inorganic fine powder has been subjected to a hydrophobic treatment. 17. The method according to claim 1, wherein the inorganic fine powder is treated with at least silicone oil.
17. The magnetic toner according to any one of 3 to 16, 18. The method according to claim 13, wherein the inorganic fine powder is treated with a silicone oil at least at the same time as the treatment with the silane compound.
18. The magnetic toner according to any one of 17. 19. The magnetic toner according to claim 15, wherein the inorganic fine powder is silica, and the liberation rate of the silica is 0.1 to 2.0%. . 20. The magnetic toner according to claim 15, wherein the inorganic fine powder is silica, and a liberation rate of the silica is 0.1 to 1.5%. . 21. The magnetic toner according to claim 1, wherein the surface of the toner particles has conductive fine powder having a volume average particle diameter smaller than a weight average particle diameter of the magnetic toner.
0. The magnetic toner according to any one of 0. 22. The resistance of the conductive fine powder is 1 × 10 ⁹
22. The magnetic toner according to claim 21, which has a value of? Cm or less. 23. The resistance of the conductive fine powder is 1 × 10 ⁸
22. The magnetic toner according to claim 21, which has a value of? Cm or less. 24. The magnetic toner according to claim 21, wherein the conductive fine powder is non-magnetic. 25. The release rate of the conductive fine powder is from 5.0 to 5.0.
The magnetic toner according to any one of claims 21 to 24, wherein the content is 50.0%. 26. The magnetic powder having a volume average particle size of 0.0
The thickness is 5 to 0.40 [mu] m.
6. The magnetic toner according to any one of 5. 27. The magnetic toner according to claim 1, wherein a volume average variation coefficient in the particle size distribution of the magnetic powder is 35 or less. 28. The magnetic powder according to claim 1, wherein the magnetic powder has been subjected to a hydrophobic treatment with a coupling agent.
8. The magnetic toner according to any one of items 7 to 7. 29. The magnetic toner according to claim 28, wherein the magnetic powder is subjected to a surface treatment by hydrolyzing a coupling agent in an aqueous medium. 30. The magnetic toner, wherein the magnetic field is 79.6 kA.
/ M is 0.5 to 6 Am ² / kg
The magnetic toner according to any one of claims 1 to 29, wherein: 31. A charging step of charging an image carrier, an electrostatic latent image forming step of writing image information as an electrostatic latent image on the charged image carrier, and an image carrier holding the electrostatic latent image on a surface. The developing unit is formed by arranging the toner and the magnetic toner carrier that carries the magnetic toner on the surface at a predetermined interval, and the magnetic toner is formed on the surface of the magnetic toner carrier to a thickness smaller than the interval. A developing step of forming the toner image by transferring the magnetic toner to the electrostatic latent image in the developing section to which the coating is applied and an alternating electric field is applied; and a transfer step of transferring the toner image to a recording medium. And
In an image forming method in which an image is repeatedly formed on an image carrier, the magnetic toner includes at least toner particles having a binder resin, a release agent, and a magnetic powder, and has a weight average particle diameter of 3
A magnetic toner having a magnetization intensity of 10 to 50 Am ² / kg in a magnetic field of 79.6 kA / m, an average circularity of 0.970 or more, and a weight-average particle size relative to the number-average particle size. The ratio of the diameters is 1.40 or less, the release rate of iron and iron compounds is 0.05 to 3.00%, and the viscosity measured by a flow tester is 1.0 × 10 ⁵ Pa.
Temperature at which s is 80 to 120 ° C. and 1.0 ×
A magnetic toner having a temperature of 10 ⁴ Pa · s of 100 to 150 ° C., wherein in the charging step, a voltage is applied to a charging member which is in contact with the image bearing member by forming a contact portion. An image forming method for charging an image carrier. 32. The image forming method according to claim 31, wherein the developing step also serves as a cleaning step of collecting the toner remaining on the image carrier after transferring the toner image onto a recording medium. . 33. The image forming method according to claim 31, wherein the magnetic toner used in the developing step is the magnetic toner according to any one of claims 2 to 30. 34. The method according to claim 31, wherein in the charging step, a conductive fine powder is interposed at least in a contact portion between the charging member and the image carrier and in the vicinity thereof.
34. The image forming method according to any one of items 33 to 33. 35. In the charging step, the image carrier is charged in a state where 1 × 10 ³ particles / mm ² or more of conductive fine powder is interposed in a contact portion between the charging member and the image carrier. The image forming method according to any one of claims 31 to 34, wherein the method is a process. 36. The charging step in which the surface of the charging member forming the contact portion and the surface of the image carrier are charged while moving with a relative speed difference. The image forming method according to any one of claims 31 to 35, wherein: 37. The image forming apparatus according to claim 31, wherein the charging step is a step of charging the image carrier while the surface of the charging member and the surface of the image carrier move in directions opposite to each other. Item. 38. The charging step, wherein the Asker C hardness is 5
4. A step of charging the image carrier by applying a voltage to a roller member at 0 degrees or less.
The image forming method according to any one of Items 1 to 37. 39. The charging step is a step of charging the image carrier by applying a voltage to the roller member, wherein the roller member has an average cell diameter of 5 to 3 in spherical form.
A porosity of at least 15 μm is provided on at least the surface of the roller member with the cavities being voids.
The image forming method according to any one of claims 31 to 38, wherein the ratio is 90%. 40. The charging step, wherein the volume resistance value is 1 × 10
The image forming method according to any one of claims 31 to 39, characterized in that by applying a voltage to the charging member ^{3 ~1} × 10 ^{8 Ωcm} is a step of charging the image bearing member. 41. The image forming apparatus according to claim 31, wherein the charging step is a step of charging the image carrier by applying a voltage to a conductive brush member as the charging member. The image forming method according to claim 1. 42. In the charging step, when a discharge starting voltage in applying a DC voltage is Vth, a DC voltage or an AC voltage having a peak-to-peak voltage of less than 2 × Vth (V) is superimposed on the DC voltage on the charging member. The image forming method according to any one of claims 31 to 41, wherein the step of applying an applied voltage charges the image carrier. 43. The charging step is a step of charging the image carrier by applying a voltage obtained by superimposing a DC voltage or an AC voltage having a peak-to-peak voltage less than Vth (V) on the DC voltage to the charging member. The image forming method according to any one of claims 31 to 42. 44. The image according to claim 31, wherein the outermost layer of the image carrier has a volume resistivity of 1 × 10 ⁹ to 1 × 10 ¹⁴ Ωcm. Forming method. 45. The image according to claim 31, wherein the outermost surface layer of the image bearing member is a resin layer in which conductive particles made of at least a metal oxide are dispersed. Forming method. 46. The image forming apparatus according to claim 31, wherein a contact angle of the surface of the image carrier with water is 85 degrees or more.
45. The image forming method according to any one of the items 45. 47. The outermost surface layer of the image carrier is a resin layer in which at least one or more lubricant fine particles selected from fluorine resin particles, silicone resin particles and polyolefin resin particles are dispersed. Claim 31
47. The image forming method according to any one of items 46 to 46. 48. The image forming method according to claim 31, wherein the image carrier is a photoconductor using a photoconductive substance. 49. The image forming method according to claim 31, wherein in the electrostatic latent image forming step, an electrostatic latent image is formed on the image carrier by image exposure. 50. The developing step is a step of forming a toner layer of 5 to 50 g / m ² on a magnetic toner carrier and transferring a magnetic toner from the toner layer to an image carrier to form a toner image. The image forming method according to any one of claims 31 to 49, wherein: 51. The image forming method according to claim 31, wherein in the developing step, the distance between the image carrier and the magnetic toner carrier is 100 to 1000 μm. 52. The developing step comprises applying at least an alternating electric field as a developing bias between the magnetic toner carrier and the image carrier to transfer the toner to an electrostatic latent image on the image carrier. The alternating electric field is a peak-to-peak electric field strength of 3 × 10 ⁶ to 10 × 1.
0 ⁶ V / m, the image forming method according to any one of claims 31 to 51, characterized in that the frequency 500～5000Hz. 53. The transfer step, wherein the transfer member is in contact with the image carrier via the recording medium during the transfer, and the toner image on the image carrier is transferred to the recording medium. The image forming method according to any one of claims 31 to 52.