JP2005258458A - Image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming method capable of substantially extending life of developing agents while maintaining high resolution and high image quality, and providing a stable and high quality image over a long period of time. <P>SOLUTION: The image forming method uses two-component developers of a magnetic carrier and each toner of YMCBk. An image forming device comprises a photoreceptor, a developer support member that contains two or more magnets inside, a means for supplying developers to the support member, a developer return member that compresses the developers on the developer support member, and a bristle height restricting member that cuts bristles of a magnetic brush on the developer support member. Furthermore, the image forming device comprises a fixing device in which an image forming station corresponding to each color having a developing device equipped with developing poles in which the two or more magnets correspond to developing areas, and a cut pole that faces the upstream of the bristle height restricting member is disposed along a belt-like mobile object, and which fixes a toner image carried by the mobile object on a material to which the image is transferred. The image forming method uses the image forming device and forms the image. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming method such as an electrophotographic method or an electrostatic printing method in which an electric latent image is developed with a developer.

  Electrophotography is a light obtained by containing an inorganic photoconductive material such as selenium, zinc oxide or cadmium sulfide, or an organic photoconductive material such as anthracene or polyvinylcarbazole in a colorant resin as necessary. An electrostatic latent image is formed on a conductive layer or a photosensitive plate, the latent image is developed with a developer containing toner, transferred to a transfer sheet such as paper or sheet, and then solvent vapor, heating, and pressurization. Or it is fixed by heating, pressurizing or the like.

  In recent years, in copying machines using the above-described electrophotographic method, the development from mono-color copying to full-color copying is rapidly progressing, and two-color color copying machines and full-color copying machines have been studied, and their practical application is greatly increased. Has been made. For example, as described in Non-Patent Document 1 and Non-Patent Document 2, there are reports of achievement of color reproducibility and gradation reproducibility.

  However, it is not immediately contrasted with the actual product such as television, photographs, and color prints, and for those who are accustomed to color images processed beautifully than the actual product, the full-color electrophotographic image currently in practical use is , Not necessarily satisfying.

  Here, color image formation by full-color electrophotography generally reproduces all colors using the three primary colors yellow, magenta, and cyan. In this method, first, an electrostatic latent image is formed on the photoconductive layer through a color separation light transmission filter having a complementary color relationship with the color of the toner, and then the toner is passed through a development and transfer process. It is held on a support (transfer material). This process is sequentially performed a plurality of times, and the toner is superimposed on the same support while aligning the registration, and then a final full-color image is obtained by a single fixing.

  Here, in general, in the case where the developer is a so-called two-component development system comprising a toner and a carrier, the developer charges the toner to a required charge amount and charge polarity by friction with the carrier, The electrostatic latent image is developed using electrostatic attraction. Therefore, in order to obtain a good visible image, it is necessary that the toner has a good triboelectric chargeability determined mainly by the relationship with the carrier.

  In addition, for long-term use, how to prevent deterioration of the carrier and toner and improve durability is also an important point. If copying is performed for a long period of time, the carrier deteriorates due to adhered matter, surface alteration, etc., so that the ability to impart charge to the toner is weakened, and image defects such as toner scattering and fogging occur. Further, by rubbing with the carrier for a long period of time, additives such as a fluidity imparting agent on the toner surface may deteriorate, and the reproducibility of the image may be inferior. For such a problem of improving durability, many studies have been made on the material of the carrier itself or the toner itself, but it is also important to measure matching with the developing device.

  In general, in an electrophotographic method using a two-component developer, a developer in which a toner and a magnetic carrier are mixed is supplied onto a developing sleeve having a magnet disposed therein to form a magnetic brush, thereby forming an electrostatic latent image. A toner image is formed on the photosensitive plate by rubbing or bringing the magnetic brush close to an electrophotographic photosensitive plate (photosensitive drum) having On the other hand, the developer is formed in layers on the developing sleeve, and at this time, a developer that is regulated by a layer thickness regulating means using a magnetic blade or the like is known.

  FIG. 1 shows a conventional laser beam printer having four photosensitive drums. In this printer, four image forming stations each having an image forming unit around the photosensitive drum 4 are provided corresponding to the colors, and the toner image on the photosensitive drum formed at each image forming station is received. Then, the toner image is transferred to a transfer material conveyed by a belt-like moving body that moves to face the photosensitive drum, thereby forming a color image. That is, the photosensitive drums 4 (4M, 4C, 4Y, and 4K) that rotate in the directions of the arrows (clockwise) are arranged in the magenta, cyan, yellow, and black image forming stations, Pm, Pc, Py, and Pk, respectively. The Further, around each photosensitive drum, 4M, 4C, 4Y, and 4K, a corona charger 16 (16M, 16C, 16Y, and 16K), and a scanning optical device 17 (17M, 17C, 17Y, and 17K) as optical scanning means. Further, an image forming unit having a developing device 9 (9M, 9C, 9Y, 9K) and a cleaning device 18 (18M, 18C, 18Y, 18K) is disposed.

  Further, the transfer unit constituting one of the image forming units has a transfer belt 19a commonly used in each image forming station and a transfer charger 19 (19M, 19C, 19Y, 19K) for each drum. The formation of a full-color image is achieved by sequentially transferring the toner images of the respective colors formed on the photosensitive drum on the transfer material P supported on the transfer belt 19a. Note that the transfer material P is supplied from the paper feed cassette 20, and the transfer material P after the transfer process is separated and discharged to the tray 22 via the fixing device 21.

  The scanning optical devices 17M, 17C, 17Y, and 17K are not shown, but a laser light source (not shown), a rotating polygon mirror that scans the laser light from the laser light source, and the scanning beam to the photosensitive drum 4. It comprises an fθ lens that collects light on the surface generating line, a reflection mirror that changes the light beam, and a beam detection device that detects a specific position of the scanning beam.

  The developing device 9 (9M, 9C, 9Y, 9K) will be described. The developing device 9 disposed facing the photosensitive drum 4 includes, for example, a developer container 8 and a developer carrier as shown in FIG. A developing sleeve 3, a developer returning member 1 for regulating the developer reservoir 5, and a blade 2 as a developer head height regulating member. The interior of the developing device 9 is partitioned into a developing chamber 13 (first chamber) and a stirring chamber 14 (second chamber) by a partition wall 6 extending in the vertical direction, and an upper portion of the partition wall 6 is open. The developing chamber 13 and the stirring chamber 14 contain a two-component developer containing a non-magnetic toner and a magnetic carrier, and the developer remaining in the developing chamber 13 is collected on the stirring chamber 14 side.

  Screw type first and second developer agitating / conveying means 11 and 12 are disposed in the developing chamber 13 and the agitating chamber 14, respectively. The first agitating screw 11 agitates and conveys the developer in the developing chamber 13 to the developing sleeve 3, and the second agitating screw 12 controls the toner replenishing tank (see FIG. (Not shown), the toner supplied to the upstream side of the stirring screw 12 and the developer already in the stirring chamber 14 are stirred and conveyed to uniformize the toner concentration. The partition wall 6 is formed with a developer passage (not shown) for alternately communicating the developing chamber 13 and the stirring chamber 14 at the front and back ends in FIG. , 12 is configured such that the developer in the developing chamber 13 whose toner density is reduced due to the toner being consumed by the development is moved into the stirring chamber 14 from the other passage.

  The developing chamber 13 of the developing device 9 has an opening at a position corresponding to the developing area facing the photosensitive drum 4, and the developing sleeve 3 is rotatably disposed so as to be partially exposed to the opening. The developing sleeve 3 is made of a nonmagnetic material, and rotates in the direction of the arrow shown in the drawing operation. A magnet (magnet roller) 10 serving as a magnetic field generating means is fixed inside the developing sleeve 3. The developing sleeve 3 carries and conveys a two-component developer layer whose layer thickness is regulated by a blade 2 that cuts a magnetic brush to a predetermined head height to a developing area facing the photosensitive drum 4, and the developer is photosensitive in the developing area. The electrostatic latent image is developed by supplying it to the drum 4. At this time, in order to improve the developing efficiency, that is, the toner application rate to the electrostatic latent image, the developing sleeve 3 is applied with a developing bias in which an AC voltage is superimposed on a DC voltage, for example, from the power source 15. .

  With the above configuration, the developing device 9 holds the developer supplied to the surface of the developing sleeve 3 by the stirring screws 11 and 12 in a magnetic brush state by the magnetic force of the magnet roller 10, and rotates the developing sleeve 3. The amount of developer conveyed to the developing area after the magnetic brush is cut off by the developer return member 1 and the blade 2 as the developer spike height regulating member. To maintain fitness.

More specifically, the magnet roller 10 in the conventional developing device as described above has a five-pole configuration, and the developer stirred by the developing chamber agitating screw 11 is first transported magnetic pole (pumping pole) for pumping. Restrained by the magnetic force of S ₂ , the developer sleeve 3 is conveyed to the developer reservoir 5 by the rotation of the developing sleeve 3. The developer raw material is regulated by the developer return member 1. In other words, in order to restrain the stable developer, the raw material is sufficiently restrained by the magnetic pole (cut pole) N ₂ having a magnetic flux density of a certain level or more, and the developer is transported while forming a magnetic brush. Next, the blade 2, that is, the head height regulating member 2 cuts off the magnetic brush to make the developer amount appropriate, and the developer is conveyed to the developing area by the conveying magnetic pole S ₁ . Further, a bias power source on which a DC electric field and / or an AC electric field is superimposed is applied to the developing sleeve 3 via the bias power source 15 provided on the image forming apparatus main body side at the developing pole N ₁ . As a result of the toner being moved toward the electrostatic latent image on the photosensitive drum 4, the electrostatic latent image is visualized as a toner image. At this time, in forming a high quality image, it is essential to stabilize the charge amount of the developer. Therefore, when a two-component developer is used, the charge amount is stabilized by the friction between the carrier and the toner in the stirring screws 11 and 12 and the developer reservoir 5. In addition, when a one-component developer is used, the charge amount is stabilized by the friction between the developing sleeve 3 and the head height regulating member 2 and the developer in the developer reservoir 5.

However, in the above-described conventional example, the developer pumped up by the magnetic restraining force from the pumping pole S ₂ in the developing device 9 is in the developer reservoir 5 formed by the developer return member 1 and the cut pole N ₂ . Therefore, there is a problem that the image quality is remarkably lowered when an image is formed over a long period of time. The reason is considered as follows.

  That is, the developer is compressed in the developer reservoir 5 and rubbed strongly with the developing sleeve 3 in order to stabilize the charge amount and stabilize the rising of the developer. As a result, when a two-component developer is used, the toner resin is fused to the carrier surface, so-called carrier spent, and silica or titanium oxide externally added to improve toner fluidity. As a result, the toner cannot be stably charged, resulting in toner scattering and fogging, and the overall image quality is significantly reduced. There was a drawback that it would.

  In addition, the conventional toner used in the apparatus as described above is generally obtained by melt-kneading a colorant composed of a dye or a pigment in a binder resin such as a thermoplastic resin and uniformly dispersing it. The finely pulverized product obtained by fine pulverization by a fine pulverizer is further classified by a classifier to produce a desired particle size. However, this manufacturing method can produce a very good toner, but has certain limitations, i.e., the range of toner materials that can be selected. For example, the resin colorant dispersion is required to be sufficiently brittle and capable of being finely pulverized by an economically possible production apparatus. However, if the resin colorant dispersion is made brittle in order to satisfy these requirements, when the dispersion is actually finely pulverized at high speed, the range of the particle size of the formed particles tends to be widened, especially relatively large. There arises a problem that fine particles are contained at a ratio. Further, the toner obtained from such a brittle material is easily subjected to further fine pulverization and powdering in a developing device such as a copying machine. In addition, it is difficult to completely disperse solid fine particles such as colorants in the resin, and depending on the degree of dispersion, fogging at the time of image formation, image density reduction, color mixing, or poor transparency Sufficient attention must be paid to the dispersion of the colorant. In addition, exposure of the colorant to the fracture surface of the pulverized particles may cause a change in development characteristics.

  On the other hand, in order to overcome the problems of the toner produced by the pulverization method, various polymerization method toners and production methods thereof, including suspension polymerization toners described in Patent Documents 1 to 3 and the like, have been proposed. ing. For example, in a suspension polymerization method toner, a polymerizable monomer, a colorant, a polymerization initiator, and, if necessary, a crosslinking agent, a charge control agent, and other additives are uniformly dissolved or dispersed in a single amount. After forming the body composition, the monomer composition is dispersed in a continuous phase containing a dispersion stabilizer, for example, an aqueous phase using an appropriate stirrer, and at the same time, a polymerization reaction is performed to obtain a desired composition. Toner particles having a particle size are obtained.

  In this method, since the pulverization step is not included at all, the toner does not need to be brittle, unlike the case of the pulverization method described above, and a soft material can be used as the resin, and the colorant on the particle surface can be used. There is an advantage that a toner having no uniform exposure and triboelectric chargeability can be obtained. Further, since the particle size distribution of the obtained toner is relatively sharp, the toner can be obtained in a high yield even if the classification step is omitted or classified. Furthermore, since a large amount of a low softening point substance can be encapsulated in the toner as a release agent, there is an advantage that the obtained toner has excellent offset resistance.

  As an example using a polymerized toner, Patent Document 4 describes that a secondary particle toner obtained by fusing primary polymerized particles is used, and Patent Document 5 describes a polymerized toner that transmits photoreceptor exposure light. Patent Document 6 discloses the use of a toner that defines the volume average diameter, number average diameter, toner charge amount, toner projected image area ratio, toner BET specific surface area, and the like. However, these have not solved all the practical problems.

  In particular, the polymerized toner prepared by suspension polymerization has a spherical shape, and the toner surface is in contact with carrier particles throughout compared to the irregular shaped toner, so that the toner deteriorates compared with the toner by the conventional pulverization method. It was easy and problematic. Further, when a low softening point substance is encapsulated in the toner in a large amount as a release agent for color toners, the low softening point substance is exposed on the surface, or the surface resin is plasticized by the low softening point substance. When this occurs, the external additive is easily embedded, which promotes toner deterioration.

  In addition, in recent years, demand for high definition and high image quality of copiers and printers has increased in the market, and in this technical field, attempts have been made to achieve high image quality by reducing the particle size of toner. Yes. However, as the particle size becomes smaller, the surface area per unit weight increases, and the amount of electric charge of the toner tends to increase, and the durability deterioration is further promoted.

  In the image forming apparatus having the configuration shown in FIG. 1 and having a plurality of image forming units, various problems different from those described above have occurred. In other words, this configuration has the advantage that the printing speed can be greatly increased because a full-color image can be formed on the recording material by a single movement. It could not be said that it was adapted to use. Therefore, recently, an attempt has been made to design an image forming unit, a fixing device, etc. in a small size, and to make the device as small as or less than that of a conventional device. Attempts have been made to reduce the size of the image forming unit by reducing or deleting the size. At this time, when the toner used in the conventional developing device is used, a large problem as described below occurs with respect to the downsizing of the apparatus.

  First, as for the cleaning process, blade cleaning, fur brush cleaning, roller cleaning, and the like are generally used. However, in either method, the residual toner is mechanically scraped or damped and discarded. The toner is collected in a toner container. On the other hand, in the development process using the conventional toner, the photosensitive member is worn and shortened due to the polishing effect of the toner existing between the cleaning member and the photosensitive drum.

  Also, conventional toner has a limit in transferability, and there is nearly 10% of residual toner after transfer, and in order to clean this, the pressure of the cleaning member must be increased to some extent, It contributed to wear. In addition, the increase in the number of revolutions by reducing the diameter of the photosensitive drum promotes wear of the photosensitive drum, shortens the service life, and requires frequent replacement of the photosensitive drum. It was difficult to realize.

  Further, as described above, when conventional toner is used, the toner remaining after the transfer is nearly 10%, so that there is a drawback that the cleaner device cannot be miniaturized. In particular, color toners need to be melted and fixed in order to ensure prevention of color mixing, but conventional toners have been difficult to contain a large amount of low softening point substances. For this reason, in order to prevent offset, it is necessary to apply a large amount of silicon oil to the fixing roller, and the size of the fixing device can be prevented from being reduced.

Japanese Patent Publication No. 36-010231 Japanese Patent Publication No. 43-010799 Japanese Patent Publication No. 51-014895 JP 05-019662 A Japanese Patent Laid-Open No. 04-296766 Japanese Patent Laid-Open No. 05-188637 “Journal of the Electrophotographic Society” vol.25, No.1 (1983) “Journal of the Electrophotographic Society” vol.25, No.1, P52 (1986)

Accordingly, an object of the present invention is to propose an image forming method that solves the above-described problems.
That is, an object of the present invention is to provide an image forming method capable of significantly extending the life of a developer while maintaining high definition and high image quality and obtaining a stable and high quality image over a long period of time.
Another object of the present invention is to provide an image forming method having a small size and high-speed printing performance.
Furthermore, another object of the present invention is to provide an image forming method in which high temperature offset is prevented without applying a release agent such as oil to a fixing roller.

The above object is achieved by the present invention described below. That is, the present invention
1. An image forming method for forming an image using a two-component developer having magnetic carrier particles and magenta toner, cyan toner, yellow toner and black toner, and a photoreceptor A developer carrying body provided opposite to the photoconductor, and provided with a plurality of magnets therein, for transporting and supplying the developer to the development area, and a developer on the developer carrying body. At least a supply means, a developer returning member that compresses the developer carried on the developer carrier, and a head height regulating member that cuts the magnetic brush formed on the developer carrier to a predetermined ear height. Further, the plurality of magnets in the developer carrying body corresponds to each of the above colors having a developing pole corresponding to at least a developing zone and a developing device having a cut pole facing upstream of the head height regulating member. Image forming station An image forming apparatus that is installed along the belt-like moving body and further includes at least a fixing device for heating and pressure-fixing the toner image conveyed by the belt-like moving body on the transfer material; and An image forming method comprising forming an image under conditions satisfying at least the following (1) to (6): (1) When the magnetic flux density of the cut pole is A (Gauss), the magnetic flux density of the developer pole is B (Gauss), and the diameter of the developer carrier is d (mm),
300 ≦ A ≦ 900
600 ≦ B ≦ 1200
16 ≦ d ≦ 22
So that they have the following relationship:
0.05 ≦ {A / (B × √d)} ≦ 0.23
(2) The developer has a porosity of 45 to 60%.
(3) The toner shape factor SF-1 is 100 to 140, and SF-2 is 100 to 140.
(4) The toner contains 5 to 40 parts by mass of a low softening point substance having a melting point of 40 to 100 ° C. with respect to 100 parts by mass of the resin.
(5) The magnetic carrier particles are magnetic carrier particles in which the surface of a core material in which a ferrite core material or a magnetic material is dispersed in a resin is coated with a coating resin.
(6) The ratio of the specific surface area S1 measured by the air permeation method and the specific surface area S2 calculated by the following formula (1), in which the magnetic carrier particles have a 50% average particle diameter (D50) of 15 to 45 μm. S1 / S2 is the following relationship: 1.4 ≦ S1 / S2 ≦ 1.7
S2 = (6 / ρD50) × 10 ⁴ (where ρ = specific gravity of carrier) Magnetic carrier particles having (1).
2. 2. The image forming method according to 1 above, wherein a part or the whole of the toner is formed by a polymerization method.
3. The weight average particle diameter of the toner is 3.5 to 7.5 μm and the toner having a particle diameter of 5.04 μm or less is more than 25% by number, and the toner having a particle diameter of 4 μm or less is 5% by number or more and 8 μm. 3. The image forming method according to 1 or 2 above, wherein the toner having a particle size of 30% by volume or less and the toner having a particle size of 10.08 μm or more are contained by 6% by volume or less.
4). The magnetic carrier particles have a 50% average particle diameter (D50) of 15 to 45 μm, and a ratio S1 / S2 between the specific surface area S1 measured by the air permeation method and the specific surface area S2 calculated by the following formula (1) 4. The image forming method as described in any one of 1 to 3 above, wherein the magnetic carrier particles have the following relationship.
1.2 ≦ S1 / S2 ≦ 2.0
S2 = (6 / ρD50) × 10 ⁴ (where ρ = specific gravity of carrier) (1)
5). 5. The image forming method as described in any one of 1 to 4 above, wherein the magnetic flux density of the developing pole is 600 gauss or more.

  As a result of intensive studies to solve the problems of the prior art, the present inventors have investigated the prevention of durability deterioration of the developer and the stability of the developer layer on the developing sleeve in the two-component development method, Ascertained that the magnetic flux density of the magnetic pole for use and the porosity of the developer are closely related, the present invention has been achieved.

According to the present invention, there is provided an image forming method capable of significantly extending the life of a developer while maintaining high definition and high image quality and obtaining a stable and high quality image over a long period of time.
Furthermore, according to the present invention, there is provided an image forming method which has a small and high-speed printing performance and prevents high temperature offset without applying a release agent such as oil to a fixing roller.

Next, the present invention will be described in more detail with reference to preferred embodiments.
An example of the developing device used in the present invention will be described with reference to FIG. First, the developer in the developing chamber 13, carrying the magnetic pole of the magnet (magnet roller) 10 which is incorporated in the developing sleeve 3, i.e. pumped by the action of the pole S _2, carried on the developing sleeve 3. The developer carried and transported by the developing sleeve 3 is compressed by the developer returning member 1 that regulates the developer reservoir 5, and the layer pressure is regulated by the blade 2 that cuts to a predetermined head height, so that the development area is controlled. It is conveyed to. The developer remaining undeveloped in the development zone is conveyed again to the developing chamber 13 by the developing sleeve 3 and scraped off from the developing sleeve 3 into the developing chamber 13 by the repulsive magnetic poles S ₃ and S ₂ . Collected.

On the other hand, the first stirring and carrying means, i.e., stirred transported developer with the rotation of the stirring screw 11, at repelling pole S _3, S ₂ of one side of the magnetic pole S _2, is pumped to the developing sleeve 3.

The developer is formed by a magnetic field from the cut pole N ₂ , acts in the center direction of the developing sleeve 3, and has a magnetic restraint force determined according to the amount of developer regulated by the developer returning member 1, and the developing sleeve 3 is conveyed to the blade 2 by a conveying force acting in the rotational direction 3. Then, the developer is compressed by the developer returning member 1 that regulates the formation of the developer reservoir 5, and the layer thickness is regulated by the blade 2, and is conveyed to the development area. At this time, the image quality of the developer deteriorates due to the deterioration of the developer when image formation is performed over a long period of time due to the compressive force between the developers and the rubbing force between the surfaces of the developing sleeve 3. Therefore, in the present invention, the magnetic flux density is optimized. At that time, the sleeve diameter was changed and the effect on the deterioration was taken into consideration, and optimization was performed at the same time.

As a result of this examination, the magnetic flux density of the cut pole N ₂ located upstream of the blade 2 is A (Gauss), the magnetic flux density of the development pole N ₁ is B (Gauss), and the diameter of the developer carrier is d (mm). When
0.05 ≦ {A / (B × √d)} ≦ 0.23
In this case, it was found that there is an effect on image deterioration. That is, if it is larger than this range, the developer is strongly compressed and rubbed in the developer reservoir 5 formed between the cut pole N ₂ and the blade 2, so that image deterioration occurs, and if it is smaller, the head is cut off. The regulation at the position is unstable, and it is not possible to secure good spikes. Therefore, the stability of the developer layer at the development position is lost, and image defects such as unevenness occur. Further, when high image quality is particularly required, it is preferable to set the following range.
0.10 ≦ {A / (B × √d)} ≦ 0.20

  Regarding the sleeve diameter, if the sleeve 3 is a small diameter sleeve, the number of times the developer passes through the panning position increases. Therefore, compared with the case of the large diameter sleeve, the magnetic flux density of the cut pole is larger than the development pole. Need to be relatively small. As a result of producing and examining several types of sleeves having different diameters, the present inventors have reached the conclusion that image deterioration can be prevented by keeping the development pole, cut pole, and sleeve diameter within the above ranges. .

In the image forming method of the present invention, it has been found that the magnetic flux density of the developing pole N ₁ is preferably 600 gauss or more. This is because if it is less than 600 gauss, high image quality cannot be achieved and the image has poor highlight reproducibility.
As described above, the present inventors have intensively studied and found that the configuration of the developing device having the above configuration is effective for image deterioration. Further, the change in the void ratio of the developer used at that time It became clear that the effect was influenced by.

As described above, the developer carried and transported by the developing sleeve 3 is compressed by the magnetic restraining force of the cut pole N ₂ facing the ear cutting position from the supply position of the developer to the developing sleeve 3, and the developing sleeve. However, it is necessary to control the developer porosity in the range of 45 to 60% in order to stabilize the developer and the developer layer under the above-mentioned developer setting conditions. Judged to be essential. That is, if the developer porosity is less than 45%, even if the magnetic flux density is optimized under the above conditions, the developer is strongly packed by the magnetic restraint force of the cut pole N ₂ and the share is increased. Due to the rubbing, the developer deteriorates and the image deteriorates. Further, if the porosity is larger than 60%, the developer becomes bulky. Therefore, the magnetic restraint force of the cut pole N ₂ cannot sufficiently restrain and compress the developer. The agent layer becomes unstable, developer unevenness on the developing sleeve 3 and the like occur, and the image deteriorates.

  As a method for controlling the porosity of the developer, it is necessary to adapt the surface property of the carrier, the shape and surface property of the toner, the bulk density of the external additive, and the like in an appropriate combination. For example, there is a method of changing the porosity by changing the mixing ratio of toner and carrier particles, but it is basically set to a toner concentration corresponding to the specific surface area of the carrier particles. As the number of contacts increases, toner deterioration becomes severe. On the other hand, when the contact number is increased, toner scattering or the like occurs, which is not preferable as a method of changing the void ratio.

  There is also a method of changing the porosity only by the addition amount of the external additive, but the addition amount is determined by adjusting the fluidity of the toner and the balance of the charging performance. If this is done, adverse effects such as toner scattering, segregation of external additives, and deterioration of developability increase, which is not preferable.

There is also a method of changing the void ratio by adjusting the toner particle diameter. However, since the toner particle diameter is closely related to the image quality and the charge amount, it is preferable to change only for the purpose of changing the void ratio. Absent.
Here, the influence of the toner particle size will be described in detail below. First, in order to achieve the provision of a high-definition and high-quality image having the effect of the present invention, 25 toners having a weight average particle diameter of 3.5 to 7.5 μm and a particle diameter of 5.04 μm or less. 5% or more of a toner having a particle size of 4 μm or less, 30% by volume or less of a toner having a particle size of 8 μm or more, and 6 toners having a particle size of 10.08 μm or more. It is preferable to contain it by volume% or less.

  The toner having such a particle size can faithfully reproduce the latent image formed on the photoconductor, and is excellent in the reproducibility of minute dot latent images such as halftone dots and digital images. An image with excellent gradation and resolution in the highlight portion is provided. The reason for this is not necessarily clear, but is estimated as follows. In the toner used in the present invention, it is particularly preferable that toner having a particle diameter of 4 μm or less is 5% by number or more. Conventionally, the presence of particles of 4 μm or less in toner has been difficult to control the charge amount, or has been required to be actively reduced as a component that impairs the fluidity of the toner and causes toner scattering to contaminate the machine. It was. However, according to the study by the present inventors, it has been found that a certain amount of toner of about 4 μm is necessary in order to form a high quality image. For example, a toner containing a fluidity improver having a particle size distribution ranging from 0.5 μm to 30 μm and a two-component developer having a carrier are used, and a large number of toners are easily developed by changing the surface potential on the photoreceptor. The latent images with different latent image potentials on the photosensitive member were developed from those having a large development potential contrast to halftones and further to small minute dot latent images in which very little toner was developed. The developed toner on the photoreceptor was collected and the particle size distribution was measured. As a result, it was found that there are many toner particles of 7.5 μm or less, and in particular, there are many particles of about 4 μm on the latent image of minute dots. That is, when toner having a particle diameter of about 4 μm is smoothly supplied to the development of the latent image on the photoreceptor, an image that is faithful to the electrostatic latent image and does not protrude from the latent image and is truly excellent in reproducibility. Is obtained.

  More specifically, if the number of toner particles having a particle diameter of 4 μm or less is less than 5% by number, there are few toner particles effective for high image quality, and particularly effective as the toner is used by continuing to copy or print out. There is a risk that the toner particle component is reduced, the balance of the particle size distribution of the toner preferably used in the present invention is deteriorated, and the image quality is gradually lowered. In addition, when an image is formed using an irregular toner prepared by a normal pulverization method using a conventional image forming apparatus, 15% by number or more of toner particles having a particle diameter of 4 μm or less are contained in the toner. Although the degree is necessary, according to the image forming apparatus used in the present invention, if the number of toner particles having a particle diameter of 4 μm or less is 5% by number or more, high image quality can be maintained.

  Further, the toner preferably contains particles of 8 μm or more in an amount of 30% by volume or less, more preferably 25% by volume or less. If it exceeds 30% by volume, the image quality deteriorates, and more than necessary development, that is, excessive toner loading occurs, leading to an increase in toner consumption. Further, by continuing to copy or print out, the balance of the particle size distribution of the toner also deteriorates, and the image quality may be deteriorated.

  Furthermore, for the purpose of further improving the effect of the present invention and improving the chargeability and fluidity of the toner, more than 25% by number of particles of 5.04 μm or less and 6 volumes of particles of 10.08 μm or more are used. % Or less, preferably 4% by volume or less.

  By using the toner having the particle size distribution as described above in the image forming method of the present invention, a high quality image can be obtained, and the effects of the present invention can be maximized. That is, as described above, the surface area per unit weight of the toner having a small particle diameter tends to increase, and the amount of electric charge of the toner tends to increase, and the durability deterioration tends to occur. The formation method suppresses the occurrence of the above problems, and provides a high-definition and high-quality image without changing the quality for a long time.

  As described above, since the toner particle size greatly affects the image quality and the charge amount, if the toner particle size is greatly changed in order to change the void ratio, the image quality is deteriorated or the charge amount is excessively increased. Inviting situations are likely to occur. Therefore, the porosity needs to be adjusted appropriately according to changes in the shape and particle size of the toner and changes in the surface properties and particle size of the carrier.

Hereinafter, methods for measuring various physical property values used in the present invention will be described.
A method for measuring the porosity in the present invention will be described. First, using a container attached to a powder tester manufactured by Hosokawa Micron Co., Ltd., the loose apparent density of the developer is measured according to the procedure of the instruction manual of the powder tester. Next, an AccuPick 1330 manufactured by Shimadzu Corporation was used, and the toner was filled into a measurement cell of 10 cm ³ up to about the eighth minute of the container while being tapped very lightly, and then in a vacuum dryer set at 40 ° C. After drying for a period of time, the weight is measured and then inserted into the main body. After purging the helium gas at a filling pressure of 134.45 KPa 10 times, the filling pressure is 134.45 KPa and the equilibrium pressure is 0.0345 KPa. The value was determined and the true density was determined. And the porosity was computed by the following formula.
Porosity = 1-Loose apparent density / true density

The particle size distribution of the toner can be measured by various methods. In the present invention, the particle size distribution was performed using a Coulter counter. As a measuring device, a Coulter counter TA-II type (manufactured by Coulter Co.) was used, and an interface (manufactured by Nikka) and a CX-1 personal computer (manufactured by Canon) that output number distribution and volume distribution were connected to the electrolyte. Use 1% NaCl aqueous solution prepared with primary sodium chloride.
As a specific measurement method, 0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant to 100 to 150 ml of an aqueous electrolytic solution, and 2 to 20 mg of a measurement sample is further added. Next, the electrolytic solution in which the sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and then the volume and number of toners are adjusted by using the Coulter Counter TA-II with a 100 μm aperture as an aperture. Measurements were made to calculate the volume distribution and number distribution of particles of 2 to 40 μm. Then, the weight-based weight average particle diameter d ₄ determined from the volume distribution (the median value of each channel is the representative value for each channel) and the weight-based coarse powder amount determined from the volume distribution (according to the present invention) 8.0 μm or more and 10.08 μm or more), and the number-based fine powder numbers (4.0 μm or less, 5.04 μm or less) obtained from the number distribution, respectively.

As described above, in the present invention, the magnetic flux density of the cut pole N ₂ and the development pole N ₁ facing the upstream of the blade 2 is optimized, and the porosity of the developer is optimized. Thus, the life of the developer is extended while maintaining high definition and high image quality.

Further, in the image forming method of the present invention, by adopting a toner having a toner shape factor SF-1 of 100 to 180 and SF-2 of 100 to 140, there is an effect on the deterioration of the developer. Become big. SF-1 and SF-2 indicating shape factors used in the present invention are FE-SEM (S-800) manufactured by Hitachi, Ltd., 100 toner images are randomly sampled, and the image information is interfaced. Are introduced into an image analysis apparatus (Luxex 3) manufactured by Nicole Inc. and analyzed, and values obtained from the following equations are defined as shape factors SF-1 and SF-2, respectively, in the present invention.
SF-1 = {(MXLNG) ² / AREA} × (π / 4) × 100
SF-2 = (PERI / AREA) × (1 / 4π) × 100
(Where AREA = projected area of toner image, MXLNG = absolute maximum length of toner image, PERI = perimeter of toner image)
That is, the toner shape factor SF-1 indicates the degree of sphericity, and when it is larger than 140, the shape gradually changes from spherical to indefinite. SF-2 indicates the degree of unevenness, and when it is larger than 120, the unevenness of the toner surface becomes remarkable.

  The advantages of controlling the shape factor of the toner as described above will be described below. First, since the contact area with the photosensitive drum is reduced, the adhesive force is reduced, and transfer can be performed with high efficiency. FIG. 3 shows the correlation between the transfer efficiency and the shape factors SF-1 and SF-2. From this figure, the smaller the shape factor, the higher the transfer efficiency. As a result, the transfer residual toner collected in the cleaning machine 18 becomes extremely small, and the size of the cleaning device can be reduced. Furthermore, when the design is such that the cleaning device is eliminated, it is necessary to reduce the amount of residual toner to a very small amount. Therefore, in this case, it is more preferable to set the value of SF-1 to 100 to 140 and SF-2 to 100 to 120.

  As a second effect, by using toner that is spherical, smooth, and has a uniform surface, the charge of the toner after being transferred to the transfer material is constant, and when the process proceeds to the next image forming unit, the previous time The transferred toner is electrostatically peeled off from the photosensitive drum at the current image forming portion, and the retransfer phenomenon can be prevented. As a result, the toner on the transfer material is not disturbed, and a high-quality image can be obtained.

  Third, a small-diameter photosensitive drum can be used. That is, by making the shape factor spherical and smoothing the surface, it is possible to reduce the frictional force between the photosensitive drum and the cleaner member, thereby preventing the photosensitive drum from being worn. It can also be used with other photosensitive drums.

  FIG. 4 shows the correlation between the shape factors SF-1 and SF-2 and the lubricity. The lubricity was measured by applying a toner on glass, placing urethane rubber on which a 300 g weight was placed, and measuring the load that began to move when pulled from the lateral direction. From this figure, it is clear that the smaller the shape factor, the higher the lubricity. Even when a test was actually performed on the apparatus, the wear of the photosensitive drum was extremely small, and it was possible to achieve a long life of the photosensitive drum.

  In order to obtain the effect of improving the lubricity, the shape factor of the toner has been made spherical and the surface has been smoothed. However, the toner surface is in contact with carrier particles throughout compared to the irregular toner. However, since there is no escape space for additive substances such as external additives, toner deterioration is likely to occur compared to conventional toners, which is a problem. On the other hand, as described above, by using the image forming method of the present invention, it is possible to prevent toner deterioration, and while maintaining high definition and high image quality, high transfer efficiency, prevention of retransfer, and small diameter drum We were able to achieve recruitment.

  The toner used in the image forming method of the present invention may be manufactured by any manufacturing method, but a toner in which a part or all of the toner is formed by a polymerization method, rather than a conventional pulverization method. By using this, the effect of the present invention can be further enhanced. In particular, for a toner in which a portion on the toner surface is formed by a polymerization method, it is present as pre-toner (monomer composition) particles in a dispersion medium, and a necessary portion is generated by a polymerization reaction. It is possible to obtain a smoothed one.

Toner particle size distribution control and particle size control can be done by changing the type and amount of the water-insoluble inorganic salt or protective colloid dispersant, mechanical conditions such as rotor peripheral speed, number of passes, etc. By controlling the stirring conditions such as the shape of the stirring blades, the container shape, or the solid content concentration in the aqueous solution, the predetermined toner of the present invention can be obtained.
Further, the toner used in the present invention is a toner containing 5 to 40 parts by mass of a low softening point substance having a melting point of 40 to 100 ° C. with respect to the binder resin. When a toner that contains a low softening point substance is employed, the effect of the image forming method of the present invention is increased. That is, in this way, by including a large amount of a low softening point substance in the toner, a releasability when melting and mixing several colors of toner, which has conventionally been indispensable in the case of full-color printing, is provided. This eliminates the need for silicone oil applied to the fixing roller.

  In this case, the low softening point substance that can be used in the present invention is preferably a compound having a melting point principal maximum peak value measured in accordance with ASTM D3418-8 of 40 to 100 ° C. When the maximum peak is less than 40 ° C., the self-aggregation force of the low softening point substance becomes weak, and as a result, the high temperature offset property becomes weak, which is not preferable. On the other hand, when the maximum peak exceeds 100 ° C., in the case of obtaining a toner by a direct polymerization method, granulation and polymerization are carried out in an aqueous system. Therefore, if the temperature of the maximum peak value is high, the softening is mainly reduced during granulation. This is not preferable because spot substances are precipitated and hinder the suspension system.

  For example, DSC-7 manufactured by Perkin Elmer is used for measuring the maximum peak temperature of the melting point in the present invention. The temperature correction of the device detection unit uses the melting points of indium and zinc, and the correction of heat uses the heat of fusion of indium. The sample was measured using an aluminum pan, an empty pan was set as a control, and the heating rate was 10 ° C./min. The measurement was performed.

  Specific examples of the low softening point material that can be used in the present invention include, for example, paraffin wax, polyolefin wax, Fischer tropish wax, amide wax, higher fatty acid, ester wax, and derivatives or grafts / blocks thereof. A compound etc. can be utilized. Such a low softening point substance is preferably added to the toner in a proportion of 5 to 40 parts by weight with respect to the binder resin. If the addition is less than 5 parts by weight, the releasability is insufficient and offset occurs, which is not preferable. On the other hand, when the amount exceeds 40 parts by weight, a large amount of low softening point substances may appear on the surface, which easily causes carrier contamination, toner deterioration, photoreceptor contamination, and the like. Further, when a toner is prepared by a polymerization method, toner particles tend to coalesce at the time of granulation, and a toner having a wide particle size distribution is easily generated.

  As a specific method for encapsulating the low softening point substance as described above, a conventional raw material is not impossible even by a method obtained by melting, kneading, and pulverizing, but it can be encapsulated in a large amount. It is preferable to carry out by a polymerization method that can reduce the exposure of the low softening point material to the surface. For example, by setting the polarity of the material in the aqueous medium to be lower for the low softening point substance than for the main monomer, and by adding a small amount of a highly polar resin or monomer, the low softening point A toner in which a substance is encapsulated can be easily obtained.

  However, when a large amount of low softening point material is encapsulated in the toner, there may be adverse effects such as exposure of the low softening point material to the surface or softening of the toner surface due to plasticization of the low softening point material. In this case, however, the external additive is easily embedded, resulting in the promotion of toner deterioration. However, toner degradation can be prevented by using the image forming method of the present invention, and the above-described advantages can be obtained.

Furthermore, in the present invention, when a small-diameter carrier is used, the effect is great. In particular, the carrier preferably applied to the present invention has a 50% average particle diameter (D50) of 15 to 45 μm, a specific surface area S1 measured by an air permeation method, and a specific surface area S2 calculated by the following formula (1). The ratio with
1.2 ≦ S1 / S2 ≦ 2.0
S2 = (6 / ρD50) × 10 ⁴ (ρ = specific gravity of carrier)
Is a career. The carrier is a carrier having a small average particle diameter and a certain degree of irregularities on the surface. For this reason, the toner transportability is also good, and the rise of the triboelectric chargeability with the toner is preferably improved.

  In the carrier used in the present invention, the ratio of the specific surface area S1 measured by the air permeation method and the specific surface area S2 calculated by the formula (1) is 1.2 ≦ S1 / S2 ≦ 2.0. However, it is more preferably 1.3 to 1.8, and still more preferably 1.4 to 1.7. When S1 / S2 is smaller than 1.2, the surface of the carrier becomes smooth and the toner transportability is lowered. As a result, toner scattering, fogging, image unevenness and the like occur. On the other hand, if S1 / S2 is greater than 2.0, the unevenness of the carrier surface becomes too large, and the carrier surface tends to become non-uniform when it is treated with a resin or the like. In addition, toner scattering occurs and carrier adhesion easily occurs.

In using the carrier as described above, it is important to control the porosity of the developer within the range of 45 to 60% as described above. By reducing the diameter of the carrier, the contact point between the toner and the carrier increases, and it becomes a severe direction against the toner deterioration. However, by applying the image forming method of the present invention, the toner transportability and the frictional charging from the beginning. Therefore, a high-definition and high-quality copy can be obtained.
In addition, as a measuring method of the particle size distribution of the carrier, an SRA type of a micro track particle size analyzer (Nikkiso Co., Ltd.) was used for the measuring device, and measurement was performed with a range setting of 0.7 to 125 μm.

  As described above, the configuration of the present invention significantly increases the life of the developer while maintaining high definition and high image quality, and has a small and high-speed printing performance while obtaining a stable and high-quality image over a long period of time. In addition, the image forming method prevents high temperature offset without applying a release agent such as oil to the fixing roller.

  The method for producing the toner used in the present invention is not particularly limited, but a method for directly producing toner using a suspension polymerization method, or an aqueous system that is soluble in monomers and insoluble in the resulting polymer. Use a dispersion polymerization method that directly produces toner using an organic solvent, or an emulsion polymerization method typified by a soap-free polymerization method that produces a toner by direct polymerization in the presence of a water-soluble polar polymerization initiator. Is possible.

  As the resin constituting the toner used in the present invention, generally used styrene- (meth) acrylic copolymer, polyester resin, epoxy resin, styrene A butadiene copolymer monomer is preferably used. Specifically, styrene monomers such as styrene, o (m-, p-)-methylstyrene, m (p-)-ethylstyrene; methyl (meth) acrylate, ethyl (meth) acrylate, ( Meth) propyl acrylate, butyl (meth) acrylate, octyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, behenyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (Meth) acrylate monomers such as dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate; ene monomers such as butadiene, isoprene, cyclohexene, (meth) acrylonitrile and acrylamide Is preferably used.

  These may be used alone or in general, so that the theoretical glass transition temperature (Tg) described in Polymer Handbook 2nd edition (plan) -P139-192 (manufactured by John Wiley & Sons) is 40 to 75 ° C. It is used by mixing the body appropriately. When the theoretical glass transition temperature is less than 40 ° C., there are problems in terms of the storage stability of the toner and the durability stability of the developer. On the other hand, when it exceeds 75 ° C., the fixing point is increased. In the case of toner, color mixing of toners of each color is insufficient and color reproducibility is poor, and transparency of the OHP image is remarkably lowered, which is not preferable from the viewpoint of high image quality.

  The molecular weight of the binder resin is measured by GPC (gel permeation chromatography). As a specific GPC measurement method, a toner is previously extracted with a Soxhlet extractor for 20 hours with a toluene solvent, and then toluene is distilled off with a rotary evaporator. Further, the low softening point substance is dissolved. The shell resin is a sample obtained by adding an organic solvent that cannot be dissolved, such as chloroform, and thoroughly washing, and then filtering the solution soluble in THF (tetrahydrofuran) with a solvent-resistant membrane filter having a pore size of 0.3 μm. The column structure can connect A-801, 802, 803, 804, 805, 806, and 807 manufactured by Showa Denko, and the molecular weight distribution can be measured using a standard polystyrene resin calibration curve. The number average molecular weight (Mn) of the obtained resin component is 5,000 to 1,000,000, and the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 2 It is preferable in the present invention to use a resin exhibiting ~ 100.

 In the present invention, when a toner having a core / shell structure is produced, it is particularly preferable to add a polar resin in addition to the outer shell resin in order to encapsulate the low softening point substance in the outer shell resin. . As the polar resin used in that case, a copolymer of styrene and (meth) acrylic acid, a maleic acid copolymer, a saturated polyester resin, an epoxy resin, or the like is preferably used. As the polar resin, an outer shell resin or one having no unsaturated group capable of reacting with a monomer in the molecule is particularly preferably used. If a polar resin having an unsaturated group is included, a crosslinking reaction occurs with the monomer that forms the outer shell resin layer. This is disadvantageous for the color mixture of, and is not preferable.

  In the present invention, an outermost resin layer may be further provided on the surface of the toner. The glass transition temperature of the outermost shell resin layer is designed to be higher than the glass transition temperature of the outer shell resin layer in order to further improve the blocking resistance, and is further crosslinked to the extent that the fixing property is not impaired. It is preferable. The outermost shell resin layer preferably contains a polar resin or a charge control agent in order to improve chargeability.

The method for providing the outermost shell layer is not particularly limited, and examples thereof include the following methods.
(1) In the latter half of the polymerization reaction or after completion, if necessary, a monomer in which a polar resin, a charge control agent, a cross-linking agent, etc. are dissolved and dispersed is added to the reaction system and adsorbed on the polymer particles. Addition and polymerization.
(2) If necessary, emulsion-polymerized particles or soap-free polymerized particles composed of monomers containing a polar resin, a charge control agent, a cross-linking agent, etc. are added to the reaction system and aggregated on the surface of the polymerized particles. A method of fixing by heat or the like.
(3) A method in which emulsion-polymerized particles or soap-free polymerized particles composed of monomers containing a polar resin, a charge control agent, a cross-linking agent, and the like are mechanically fixed to the toner particle surface in a dry manner as required.

As the colorant constituting the toner used in the present invention, for example, as a black colorant, carbon black, a magnetic material, and a toner that is toned in black using a yellow / magenta / cyan colorant as shown below are used. Used.
As the yellow colorant, compounds represented by condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, and allylamide compounds are used. Specifically, C.I. I. Pigment Yellow 12, 13, 14, 15, 17, 62, 74, 83, 93, 94, 95, 109, 110, 111, 128, 129, 147, 168, etc. are preferably used.

  As the magenta colorant, condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinones, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, and perylene compounds are used. Specifically, C.I. I. Pigment Red 2, 3, 5, 6, 7, 23, 48: 2, 48: 3, 48: 4, 57: 1, 81: 1, 122, 146, 166, 169, 177, 184, 185, 202, 206, 220, 221, 254 and the like are preferably used.

  As the cyan colorant, copper phthalocyanine compounds and derivatives thereof, anthraquinone compounds, basic dye lake compounds, and the like are used. Specifically, C.I. I. Pigment Blue 1, 7, 15, 15: 1, 15: 2, 15: 3, 15: 4, 60, 62, 66 and the like are preferably used.

  These colorants can be used alone or in combination and further in the form of a solid solution. In the case of a color toner, the colorant used in the present invention is selected from the viewpoints of hue angle, saturation, brightness, weather resistance, OHP transparency, and dispersibility in the toner. Moreover, the addition amount of a coloring agent is used by adding 1 to 20 parts by weight with respect to 100 parts by weight of the resin. When a magnetic material is used as the black colorant, 40 to 150 parts by weight are added to 100 parts by weight of the resin, unlike other colorants.

  The external additive used in the present invention preferably has a particle size of 1/10 or less of the weight average particle size of the toner particles from the viewpoint of durability when added to the toner. Here, the particle size of the additive means the average particle size obtained by observing the surface of the toner particles with an electron microscope. Examples of the external additive that can be used in the present invention include aluminum oxide, titanium oxide, strontium titanate, cerium oxide, magnesium oxide, chromium oxide, tin oxide, zinc oxide, and other metal oxides such as silicon nitride. Examples thereof include carbides such as nitride and silicon carbide, metal salts such as calcium sulfate, barium sulfate, and calcium carbonate, fatty acid metal salts such as zinc stearate and calcium stearate, carbon black, and silica.

  These external additives are preferably used in an amount of 0.01 to 10 parts by weight, more preferably 0.05 to 5 parts by weight, based on 100 parts by weight of the toner particles. These external additives may be used alone or in combination. Furthermore, it is more preferable to use those that have been hydrophobized.

  As the charge control agent used in the present invention, any conventionally known charge control agent can be used. However, in the case of a color toner, in particular, the toner is colorless and has a high charging speed and a stable charge amount. It is preferable to use a charge control agent that can be maintained. Specific examples of the negative compound include salicylic acid, naphthoic acid, dicarboxylic acid metal compound, sulfonic acid, polymer compound having carboxylic acid in the side chain, boron compound, urea compound, silicon compound, calix Arene and the like are preferably used. As the positive system, for example, a quaternary ammonium salt, a polymer compound having the quaternary ammonium salt in the side chain, a guanidine compound, an imidazole compound, or the like is preferably used. In addition, it is preferable that the addition amount of these charge control agents shall be 0.5-10 weight part with respect to 100 weight part of resin.

  Next, the magnetic carrier used by being mixed with the toner obtained as described above in the present invention will be described. A carrier that is well adapted to the present invention is preferably one in which an electrically insulating resin is used as the surface coating resin on the carrier surface, but this coating resin is appropriately selected depending on the toner material and the carrier core material. The In the present invention, in order to improve the adhesion to the surface of the carrier core material, at least one kind of monomer selected from at least acrylic acid (or its ester) monomer and methacrylic acid (or its ester) monomer is used. It is preferable to contain a monomer.

  Examples of the carrier resin monomer for the carrier core material that can be used in the present invention include styrene monomers such as styrene monomer, chlorostyrene monomer, α-methylstyrene monomer, styrene-chlorostyrene monomer, acrylic Examples of the monomers include acrylate monomers (methyl acrylate monomers, ethyl acrylate monomers, butyl acrylate monomers, octyl acrylate monomers, phenyl acrylate monomers, 2-ethylhexyl acrylate monomers), and methacrylate esters. And monomers (methyl methacrylate monomer, ethyl methacrylate monomer, butyl methacrylate monomer, phenyl methacrylate monomer) and the like.

  The carrier core material (magnetic particles) used in the present invention includes, for example, surface oxidized or unoxidized iron, nickel, copper, zinc, cobalt, manganese, chromium, rare earth metals, and alloys or oxides thereof. Or a core material in which a magnetic material is dispersed in a resin can be used. Moreover, there is no special restriction | limiting as the manufacturing method.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.
First, developers A to K were prepared.
Developer A
To 710 g of ion-exchanged water, 450 g of a 0.1M Na ₃ PO ₄ aqueous solution was added, heated to 60 ° C., and then stirred at 12000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo). To this, 68 g of 1.0 M CaCl ₂ aqueous solution was gradually added to obtain an aqueous medium containing Ca ₃ (PO ₄ ) ₂ .
・ Monomer Styrene 165g
n-Butyl acrylate 35g
-Colorant C.I. I. Pigment Blue 15: 3 15g
・ Charge control agent Salicylic acid metal compound 3g
-Polar resin saturated polyester (acid value, peak molecular weight 8000) 10 g
・ Release agent Ester wax (melting point 70 ℃) 50g
On the other hand, the prescription was heated to 60 ° C., and uniformly dissolved and dispersed at 12000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo). Into this, 10 g of a polymerization initiator 2,2′-azobis (2,4-dimethylvaleronitrile) was dissolved to prepare a polymerizable monomer composition.

The polymerizable monomer composition is put into an aqueous medium containing the above Ca ₃ (PO ₄ ) ₂ and stirred at 10,000 rpm for 10 minutes with a TK homomixer in an N ₂ atmosphere at 60 ° C. The polymerizable monomer composition was granulated. Then, while stirring with a paddle stirring blade, the temperature was raised to 80 ° C. and reacted for 10 hours. After completion of the polymerization reaction, the remaining monomer was distilled off under reduced pressure, and after cooling, hydrochloric acid was added to dissolve calcium phosphate. Then, after filtration, washing and drying, those having a weight average particle size of 6.4 μm and 4 μm or less are 22.2% by number, those having a particle size of 5.04 μm or less are 48.0% by number, and 8 μm. Colored suspended particles having a particle size of 4.0% by volume and 0.7% by volume of particles having a particle size of 10.08 μm or more were obtained. When the shape factor was measured, it was SF-1 = 111 and SF-2 = 109.
To the obtained toner composition, 1.5 wt% of hydrophobic titania having a specific surface area by BET method of 100 m ² / g was externally added. For this toner 7 parts by weight, 50% average particle diameter (D50) = 35.5μm, a ^{S1 = 533m 2 / g, S2} = 365m 2 /g,S1/S2=1.46 ferrite carriers silicone coat A developer A was prepared by mixing 93 parts by weight. The porosity of this developer was 49%.

Developer B
To 710 g of ion-exchanged water, 450 g of a 0.1M Na ₃ PO ₄ aqueous solution was added, heated to 60 ° C., and then stirred at 12000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo). To this, 68 g of 1.0 M CaCl ₂ aqueous solution was gradually added to obtain an aqueous medium containing Ca ₃ (PO ₄ ) ₂ .
・ Monomer Styrene 165g
n-Butyl acrylate 35g
・ Colorant Carbon Black 15g
・ Charge control agent Salicylic acid metal compound 5g
Polar resin saturated polyester (acid value 14, peak molecular weight 8000) 10 g
-Release agent Paraffin wax (melting point 60 ° C) 30g
On the other hand, the prescription was heated to 60 ° C., and uniformly dissolved and dispersed at 12000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo). Into this, 10 g of a polymerization initiator 2,2′-azobis (2,4-dimethylvaleronitrile) was dissolved to prepare a polymerizable monomer composition.

The polymerizable monomer composition is put into an aqueous medium containing Ca ₃ (PO ₄ ) ₂ and stirred at 10000 rpm for 20 minutes in a TK homomixer at 60 ° C. under N ₂ atmosphere to polymerize. The reactive monomer composition was granulated. Then, while stirring with a paddle stirring blade, the temperature was raised to 80 ° C. and reacted for 10 hours. After completion of the polymerization reaction, the residual monomer was distilled off under reduced pressure under the same conditions as Developer A, and after cooling, hydrochloric acid was added to dissolve calcium phosphate. Then, after filtration, washing and drying, those having a weight average diameter of 7.0 μm and a particle diameter of 4 μm or less are 15.1% by number, those having a particle diameter of 5.04 μm or less are 33.5% by number, and 8 μm. Colored suspended particles having a particle size of 23.3% by volume and 1.9% by volume of particles having a particle size of 10.08 μm or more were obtained. When the shape was measured, they were SF-1 = 112 and SF-2 = 111.
To this toner composition, 2.0 wt% of hydrophobic silica having a specific surface area by the BET method of 200 m ² / g was added. To 7 parts by weight of the toner, 93 parts by weight of the carrier similar to the toner A was mixed to obtain a developer B. The porosity of this developer was 53%.

Developer C
To 710 g of ion-exchanged water, 450 g of a 0.1M Na ₃ PO ₄ aqueous solution was added, heated to 60 ° C., and then stirred at 12000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo). To this, 68 g of 1.0 M CaCl ₂ aqueous solution was gradually added to obtain an aqueous medium containing Ca ₃ (PO ₄ ) ₂ .
・ Monomer-Styrene 165g
n-Butyl acrylate 35g
-Colorant C.I. I. Pigment Blue 15: 3 15g
・ Charge control agent Salicylic acid metal compound 3g
Polar resin saturated polyester (acid value 14, peak molecular weight 8000) 10 g
On the other hand, the prescription was heated to 60 ° C., and uniformly dissolved and dispersed at 12000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo). Into this, 10 g of a polymerization initiator 2,2′-azobis (2,4-dimethylvaleronitrile) was dissolved to prepare a polymerizable monomer composition.

The polymerizable monomer composition is put into an aqueous medium containing Ca ₃ (PO ₄ ) ₂ and stirred at 10000 rpm for 10 minutes in a TK homomixer at 60 ° C. in an N ₂ atmosphere to polymerize. The reactive monomer composition was granulated. Then, while stirring with a paddle stirring blade, the temperature was raised to 80 ° C. and reacted for 10 hours. After completion of the polymerization reaction, the residual monomer is distilled off under reduced pressure under the same conditions as in Developer A. After cooling, hydrochloric acid is added to dissolve calcium phosphate, followed by filtration, washing with water, and drying. 20.8% by number of particles having a particle size of .8 μm and 4 μm or less, 39.2% by number of particles having a particle size of 5.04 μm or less, 18.5% by volume and 10.08 μm of particles having a particle size of 8 μm or more. Sharp colored suspended particles having a particle size of 1.7% by volume were obtained.
To this toner composition, 1.5 wt% of hydrophobic silica having a specific surface area by the BET method of 200 m ² / g was added. To 7 parts by weight of the toner, 93 parts by weight of the carrier similar to the toner A was mixed to obtain a developer C. The porosity of this developer was 50%.

Developer D
To 97.0 wt% of the toner composition similar to Developer A, 3.0 wt% of colloidal silica having a specific surface area by the BET method of 380 m ² / g was added. For this toner 7 parts by weight, 50% average particle diameter (D50) = 36.3μm, a ^{S1 = 630m 2 / g, S2} = 359m 2 /g,S1/S2=1.75 ferrite carriers silicone coat A developer D was prepared by mixing 93 parts by weight. The porosity of this developer was 61%.

Developer E
1.0 wt% of hydrophobic silica having a specific surface area of 90 m ² / g by BET method was added to 99.0 wt% of the toner composition similar to Developer A. For this toner 7 parts by weight, 50% average particle diameter (D50) = 36.0μm, a ^{S1 = 445m 2 / g, S2} = 362m 2 /g,S1/S2=1.23 ferrite carriers silicone coat A developer E was prepared by mixing 93 parts by weight. The porosity of this developer was 42%.

Developer F
To the same toner 5 parts by weight of the developer A, 50% average particle diameter (D50) = 51.2μm, the ^{S1 = 380m 2 / g, S2} = 249m 2 /g,S1/S2=1.53 acrylic coating A developer F was prepared by mixing 97 parts by weight of the ferrite carrier. The porosity of this developer was 42%.

Developer G
To 97.5 wt% of the same toner composition as Developer A, 2.5 wt% of colloidal silica having a specific surface area of 380 m ² / g by the BET method was added. To 8 parts by weight of this toner, 50% average particle diameter (D50) = 36.8μm, S1 = 716m 2 / g, S2 = 354m 2 /g,S1/S2=2.02 silicone coated ferrite carrier Was mixed with 97 parts by weight to obtain developer G. The porosity of this developer was 62%.

Developer H
Using the same method and raw materials as Developer A, 2.3% by weight of particles having a weight average particle diameter of 9.8 μm and 4 μm or less, and 11.6 pieces having a particle diameter of 5.04 μm or less. %, Particles having a particle diameter of 8 μm or more were 88.5% by volume, and particles having a particle diameter of 10.08 μm or more were 28.2% by volume. When this shape factor was measured, SF-1 = 112 and SF-2 = 110.
To the obtained toner composition, 1.2 wt% of hydrophobic titania having a specific surface area by BET method of 100 m ² / g was externally added. Furthermore, with respect to the toner 5 parts by weight, 50% average particle diameter (D50) = 35.5μm, S1 = 533m 2 / g, S2 = 365m 2 /g,S1/S2=1.46 silicone coated ferrite A developer H was prepared by mixing 95 parts by weight of the carrier. The porosity of this developer was 47%.

Developer I
To 710 g of ion-exchanged water, 450 g of a 0.1M Na ₃ PO ₄ aqueous solution was added, heated to 60 ° C., and then stirred at 12000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo). To this, 68 g of 1.0 M CaCl ₂ aqueous solution was gradually added to obtain an aqueous medium containing Ca ₃ (PO ₄ ) ₂ .
・ Monomer Styrene 165g
n-Butyl acrylate 35g
・ Colorant Carbon Black 15g
・ Charge control agent Salicylic acid metal compound 3g
Polar resin saturated polyester (acid value 14, peak molecular weight 8000) 10 g
・ Release agent Paraffin wax (melting point 60 ° C) 50g
On the other hand, the prescription was heated to 60 ° C., and uniformly dissolved and dispersed at 12000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo). Into this, 10 g of a polymerization initiator 2,2′-azobis (2,4-dimethylvaleronitrile) was dissolved to prepare a polymerizable monomer composition.

The polymerizable monomer composition is put into an aqueous medium containing Ca ₃ (PO ₄ ) ₂ and stirred at 10000 rpm for 10 minutes in a TK homomixer at 60 ° C. in an N ₂ atmosphere to polymerize. The reactive monomer composition was granulated. Then, while stirring with a paddle stirring blade, the temperature was raised to 80 ° C. and reacted for 10 hours. After completion of the polymerization reaction, the residual monomer was distilled off under reduced pressure. After cooling, hydrochloric acid was added to dissolve calcium phosphate, and sharp colored suspended particles having a weight average particle diameter of 1.0 μm were obtained. It was then heated to 60 ° C., adjusted to pH 7 and further heated to 90 ° C. and kept at this temperature for 2 hours. Then, after filtration, washing and drying, those having a weight average particle size of 6.5 μm, 4 μm or less are 23.2% by number, those having a particle size of 5.04 μm or less are 43.5% by number, Agglomerated particles having a particle diameter of 8 μm or more were 17.2% by volume and those having a particle diameter of 10.08 μm or more were 0.9% by volume. When the shape factor was measured, they were SF-1 = 122 and SF-2 = 128.
To this toner composition, 2.0 wt% of hydrophobic silica having a specific surface area by the BET method of 200 m ² / g was added. To 7 parts by weight of the toner, 93 parts by weight of the carrier similar to the toner A was mixed to obtain developer I. The porosity of this developer was 55%.

Developer J
A four-necked flask was charged with 180 parts by weight of nitrogen-substituted water and 20 parts by weight of a 0.20 wt% aqueous solution of polyvinyl alcohol, and then 77 parts by weight of styrene and 22 parts by weight of acrylic acid-n-butyl benzoyl peroxide 1.4. Part by weight and 0.2 part by weight of divinylbenzene were added and stirred to obtain a suspension. Then, after replacing the inside of the flask with nitrogen, the temperature was raised to 80 ° C., and the polymerization temperature was maintained at the same temperature for 10 hours.
The obtained polymer was washed with water and then dried in a reduced pressure environment while maintaining the temperature at 65 ° C. to obtain a resin. 88 wt% of the resin, 2 wt% of the metal-containing azo dye, 7 wt% of carbon black, and 3 wt% of low molecular weight polypropylene are mixed by a fixed tank dry mixer, and the biaxial extrusion is performed while the vent port is connected to a suction pump and sucked. Melt kneading was carried out with a machine.

This melt-kneaded product was roughly crushed with a hammer mill to obtain a 1 mm mesh pass toner composition coarsely pulverized product. Further, this coarsely crushed material is pulverized to a volume average diameter of 20 to 30 μm by a mechanical pulverizer, and then pulverized by a jet mill using collision between particles in a swirling flow. After modifying the toner composition by mechanical and mechanical shearing force, the toner composition is classified by a multi-stage split classifier, and the weight average diameter is 6.9 μm, and the particle diameter is 4 μm or less, 19.6% by number; A toner composition having a particle size of 04 μm or less having a particle size of 38.9%, a particle size of 8 μm or more being 22.1% by volume, and a toner composition having a particle size of 10.08 μm or more being 1.9% by volume was obtained. . When the shape factor was measured, it was SF-1 = 148 and SF-2 = 135.
To this toner composition, 2.0 wt% of hydrophobic silica having a specific surface area by BET method of 100 m ² / g was added. The developer J was prepared by mixing 93 parts by weight of the same carrier as that of the toner A with 3 parts by weight of the toner. The porosity of this developer was 54%.

Developer K
After adding 180 parts by weight of nitrogen-substituted water and 20 parts by weight of a 0.2 wt% aqueous solution of polyvinyl alcohol to a four-necked flask, 77 parts by weight of styrene and 22 parts by weight of acrylate-n-butyl benzoyl peroxide 2 parts by weight and 0.2 parts by weight of divinylbenzene were added and stirred to obtain a suspension. Then, after replacing the inside of the flask with nitrogen, the temperature was raised to 80 ° C., and the polymerization temperature was maintained at the same temperature for 10 hours. The polymer was washed with water and dried at 45 ° C. and normal pressure to obtain a resin.
55 wt% of the resin, 40 wt% of 0.1 μm magnetic material, 1 wt% of the metal-containing azo dye, 3 wt% of carbon black, and 1 wt% of low molecular weight polypropylene were mixed by a fixed tank type dry mixer, and then by a twin screw extruder. Melt kneading was performed.

This melt-kneaded product was roughly crushed with a hammer mill to obtain a 1 mm mesh pass toner composition coarsely pulverized product. Furthermore, after this coarsely crushed material is pulverized to a volume average diameter of 20 to 30 μm by a mechanical pulverizer, the crushed material is finely pulverized using an air-type pulverizer equipped with a collision plate, and multistage classification is performed. The weight average particle size is 7.3 μm, the particle size of 4 μm or less is 14.1% by number, the particle size of 5.04 μm or less is 32.1% by number, and the particle size is 8 μm or more. A toner composition having an average particle diameter of 6.8 μm was obtained. When the shape factor was measured, they were SF-1 = 191 and SF-2 = 161.
To this toner composition, 1.2 wt% of hydrophobic titania having a specific surface area by BET method of 100 m ² / g was externally added. To 7 parts by weight of the toner, 93 parts by weight of the carrier similar to the developer A was mixed to obtain a developer K. The porosity of this developer was 59%.

Examples 1-7 and Comparative Examples 1-10
Using these developers, for the magnet roller 10 in the developing device of FIG. 1, seven types of magnet magnets 10 of a to g having different magnetic flux densities of the developing pole N ₁ and the cut pole N ₂ are prepared. The developer transportability in the developing device 9, the stability of the developer layer on the developing sleeve 3, and after 50,000 copies were made in A4 size, the printing ratio was 10%, and image deterioration was observed in the replenishment experiment after toner consumption. . Further, a live-action test was conducted until the photosensitive drum was worn out and reached the end of its life. Furthermore, the number of sheets until the 100 cc waste toner box became full and replaced, and the retransfer performance were evaluated. As the image forming apparatus, the fixing step 21 uses a fluorine soft roller as the fixing roller and a silicon roller as the pressure roller, and is a fixing apparatus having no oil application function other than the web for removing roller dirt. The photosensitive drums 4M, 4C, 4Y, and 4K use organic photoconductive layers and have a protective layer on the surface and have a diameter of 30 mm. The cleaner sections 18M to K have urethane blades and photosensitive member charging. Image portions were exposed using a corona charger as means 16M-K, a conductive brush as transfer means 19M-K, and a semiconductor laser as image exposure means 17M, 17C, 17Y, 17K.

  Table 1 shows the conditions of Examples 1 to 7 and Comparative Examples 1 to 10, and Table 2 shows the evaluation results. Here, the image deterioration was performed by evaluating the roughness of the highlight image area, the maximum density, the density stability, and the like.

The stability of the developer layer is the presence or absence of irregularities due to poor conveyance of the developer, and the retransfer performance is whether the toner on the first color transfer material is peeled off by retransfer in the second color development. confirmed. The anti-offset property was determined as to whether or not an offset occurred in the image after fixing. All of these were evaluated as Δ or higher in the practical range, ○ was good, and ◎ was judged to be even better. The drum life is 50,000 sheets or more, and the waste toner box life is 20,000 sheets or more.
From the above evaluation, an overall evaluation was made and an evaluation was made. The overall evaluation Δ or higher was within the practical range, ○ was good, and ◎ was further good.

  The present invention relates to an image forming method such as an electrophotographic method or an electrostatic printing method in which an electric latent image is developed with a developer.

1 is a schematic configuration diagram of an example of an image forming apparatus. FIG. 2 is a cross-sectional view of an example of a developing device used in the image forming apparatus in FIG. 1. It is the figure which showed the correlation of transfer efficiency and a shape factor. It is the figure which showed correlation with SF-1, SF-2, and lubricity.

Explanation of symbols

1: Developer return member 2: Hot height regulating member 3: Developer carrier (developing sleeve)
4, 4M, 4C, 4Y, 4K: Image carrier (photosensitive drum)
5: Developer reservoir 6: Partition 8: Developer container 9, 9M, 9C, 9Y, 9K: Developing device 10: Magnet (magnet roller)
11, 12: Developer stirring and conveying means (stirring screw)
13: Development chamber (first chamber)
14: Stirring chamber (second chamber)
15: Bias power supply 16, 16M, 16C, 16Y, 16K: Corona chargers 17, 17M, 17C, 17Y, 17K: Scanning optical devices 18, 18M, 18C, 18Y, 18K: Cleaning devices 19, 19M, 19C, 19Y, 19K: Transfer charger 19a: Transfer belt 21: Fixing device

Claims (5)

An image forming method for forming an image using a two-component developer having magnetic carrier particles and magenta toner, cyan toner, yellow toner and black toner, and a photoreceptor A developer carrying body provided opposite to the photoconductor, and provided with a plurality of magnets therein, for transporting and supplying the developer to the development area, and a developer on the developer carrying body. At least a supply means, a developer returning member that compresses the developer carried on the developer carrier, and a head height regulating member that cuts the magnetic brush formed on the developer carrier to a predetermined ear height. Further, the plurality of magnets in the developer carrying body corresponds to each of the above colors having a developing pole corresponding to at least a developing zone and a developing device having a cut pole facing upstream of the head height regulating member. Image forming station An image forming apparatus that is installed along the belt-like moving body and further includes at least a fixing device for heating and pressure-fixing the toner image conveyed by the belt-like moving body on the transfer material; and An image forming method comprising forming an image under conditions satisfying at least the following (1) to (6):
(1) When the magnetic flux density of the cut pole is A (Gauss), the magnetic flux density of the developer pole is B (Gauss), and the diameter of the developer carrier is d (mm),
300 ≦ A ≦ 900
600 ≦ B ≦ 1200
16 ≦ d ≦ 22
And
These have the following relationship.
0.05 ≦ {A / (B × √d)} ≦ 0.23
(2) The developer has a porosity of 45 to 60%.
(3) The toner shape factor SF-1 is 100 to 140, and SF-2 is 100 to 140.
(4) The toner contains 5 to 40 parts by mass of a low softening point substance having a melting point of 40 to 100 ° C. with respect to 100 parts by mass of the resin.
(5) The magnetic carrier particles are magnetic carrier particles in which the surface of a core material in which a ferrite core material or a magnetic material is dispersed in a resin is coated with a coating resin.
(6) The ratio of the specific surface area S1 measured by the air permeation method and the specific surface area S2 calculated by the following formula (1), in which the magnetic carrier particles have a 50% average particle diameter (D50) of 15 to 45 μm. S1 / S2 is the following relationship: 1.4 ≦ S1 / S2 ≦ 1.7
S2 = (6 / ρD50) × 10 ⁴ (where ρ = specific gravity of carrier) (1)
Magnetic carrier particles having   The image forming method according to claim 1, wherein part or all of the toner is formed by a polymerization method.   The weight average particle diameter of the toner is 3.5 to 7.5 μm and the toner having a particle diameter of 5.04 μm or less is more than 25% by number, and the toner having a particle diameter of 4 μm or less is 5% by number or more and 8 μm. 3. The image formation according to claim 1, wherein the toner having a particle size of 30% by volume or less and a toner having a particle size of 10.08 μm or more is 6% by volume or less. Method. The magnetic carrier particles have a 50% average particle diameter (D50) of 15 to 45 μm, and a ratio S1 / S2 between the specific surface area S1 measured by the air permeation method and the specific surface area S2 calculated by the following formula (1) 4. The image forming method according to claim 1, wherein the magnetic carrier particles have the following relationship. 5.
1.2 ≦ S1 / S2 ≦ 2.0
S2 = (6 / ρD50) × 10 ⁴ (where ρ = specific gravity of carrier) (1) The image forming method according to claim 1, wherein a magnetic flux density of the developing pole is 600 gauss or more.

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