JPH1115300A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily obtain a high-quality output image by constituting a device so that the toner shape coefficient of one-component developer at a transfer time becomes smaller than that in a developing means. SOLUTION: This device is constituted so that the toner shape coefficient SF1 of the one-component developer at the transfer time becomes smaller than that in the developing means. Therefore, since the shape of toner used in the developing means is aspherical, the friction and rubbing of the toner can be facilitated differently from a case that spherical toner is used. Besides, a toner thin layer is easily formed on the surface of a developing blade and triboelectrification imparting property with respect to the toner is enhanced. By making the coefficient SF1 small and making the shape of the toner used for transfer spherical at the transfer time, transfer efficiency is enhanced and the middle omission of the transfer is prevented from occurring.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a latent image on an image carrier such as an electrophotographic photosensitive member or an electrostatic recording dielectric, visualizing the latent image, and transferring the latent image to a transfer-receiving medium. The present invention relates to an image forming apparatus for forming an image by using an image forming apparatus.

[0002]

2. Description of the Related Art As an output means of an external device such as a computer and a copying machine, an image forming apparatus using an electrophotographic method as shown in FIG. 6 has been conventionally proposed. First,
The drum-shaped electrophotographic photosensitive member 100 as a latent image carrier is generally charged uniformly by a primary charger 117. Next, light is irradiated from the exposure device 123 on the photoreceptor 100 in accordance with image information input from an external device to form a latent image. Thus, the photosensitive drum 1
The electrostatic latent image formed on the developing device 140
, Is reversely developed with a developer T having the same polarity as that of the primary charger 117 to be a visible image, that is, a toner image. Then, the formed toner image is transferred onto the transfer material P by the transfer charger 114. The material P to be transferred is the photosensitive member 100
The image is further separated, subsequently conveyed to the fixing device 126, and fixed to form a permanent image. On the other hand, the developer T on the photosensitive drum 100 remaining without being transferred by the transfer charger 114 is removed by the cleaning device 116. The photosensitive drum 100 from which the remaining developer has been removed in this way is again subjected to the next image forming process.

Here, the developing device indicated by 140 in FIG. 6 will be described in detail with reference to FIG. In recent years, a non-magnetic one-component developing method has been put to practical use as a simple color developing method. The developing device has a developing container 140a containing a toner T which is an insulating one-component developer. In this example, the toner T is a negatively-chargeable non-magnetic toner containing a pigment of any one of yellow, magenta, cyan, and black. A toner agitating member 106 is provided in the developing container 140a, and rotates in the direction of the arrow in the figure to convey the toner T toward the developing sleeve 102 and the developer supply roller 105.

The developing device 140 has a conductive cylindrical sleeve 102 made of a metal such as aluminum or stainless steel and having an outer diameter of about 16 mm. The developing device 140 is spaced apart from the opposing photosensitive drum 100 by a gap regulating member (not shown). It is kept and arranged. Further, a developer supply roller 105 made of urethane sponge is in contact with the developing sleeve 102. The developer supply roller 105 is connected to the developing sleeve 1.
02, the toner history (so-called ghost) on the developing sleeve 102 is removed by rotating the developing sleeve 102 at the same time.
The toner T is supplied onto the developing sleeve 102.

A developing blade 103 is abutted against the developing sleeve 102 as a toner amount regulating member, and regulates the thickness of the toner layer on the developing sleeve 102 to form a thin toner layer 10.
7, and defines the amount of toner to be conveyed to the development area (the drum-facing position). The amount of toner conveyed to the developing area depends on the amount of the developing blade 1
03 is determined by the contact pressure, the contact length, and the like. The developing blade 103 is a chip blade adhered or welded onto a thin metal plate 104 of phosphor bronze or stainless steel having a thickness of several hundred μm, and uniformly contacted with the developing sleeve 102 by the elasticity of the thin metal plate 104. Therefore, the contact condition of the developing blade 103 on the developing sleeve 102 is determined by the material, thickness, penetration amount, and set angle of the thin metal plate 104. The amount of toner transported as determined in this manner is usually specified to be about 0.3 to 1.0 mg / cm ² per unit area of the surface of the developing sleeve 102.

The toner conveyed to the developing area by the developing sleeve 102 rotates in the direction of the arrow from the developing sleeve 102 at the time of development due to a developing electric field generated by a developing power supply applied between the developing sleeve 102 and the photosensitive drum 100. Flying over the photosensitive drum 100, the photosensitive drum 10
The latent image adheres to the latent image on 0 and is visualized as a toner image.

Here, a description will be given of the toner T preferably used in a developing device using the above-described non-magnetic one-component developing method. Conventionally, as a method for manufacturing a toner,
After uniformly dispersing a resin, a release agent composed of a low softening point substance, a colorant, and a charge control agent using a pressure kneader, an extruder, or a media disperser, mechanically or under a jet stream to the target There is a method of producing a toner by a so-called pulverization method in which the particles are finely pulverized to a desired toner particle diameter after the collision, and further subjected to a classification step to sharpen the particle size distribution to obtain the toner. In addition to this,
No. 13945, a method of atomizing a molten mixture into air using a disk or a multi-fluid nozzle to obtain a spherical toner, Japanese Patent Publication No. 36-10231,
No. 9,53,856 and JP-A-59-61842, a method of directly producing a toner using a suspension polymerization method, a method of dissolving in a monomer and an insoluble polymer. A toner using a dispersion polymerization method of directly producing a toner using an aqueous organic solvent, or an emulsion polymerization method typified by a soap-free polymerization method of producing a toner by directly polymerizing in the presence of a water-soluble polar polymerization initiator. There is a manufacturing method.

In recent years, it has been found that the use of a toner having a spherical toner shape can improve the fluidity of the toner and the transfer efficiency during toner transfer. On the other hand, the following two methods are mainly used for producing spherical toner.
There is one. The surface of a conventional pulverized toner is subjected to a plastic sphering treatment by thermal stress or mechanical stress. It is produced by a polymerization method. As the spherical toner, the shape factor SF _{1 of the} toner is 100
140, is preferably used SF ₂ is 100 to 120. More preferably, SF ₁ is 100-13
0, SF ₂ good things of 100 to 115. SF ₁ and SF ₂ indicating the shape factor in the present invention are FE manufactured by Hitachi, Ltd.
-Using a SEM (S-800), 100 toner images were randomly sampled, and the image information was introduced into an Nireco image analyzer (Luzex3) via an interface, analyzed, and calculated by the following equation. Each is defined by the value obtained by the calculation.

[0009]

(Equation 1)

[0010] The shape factor SF ₁ of toner indicates the spherical degree, becomes 140 larger than, gradually amorphous the sphere. SF ₂ indicates the degree of unevenness, and if it is larger than 120, the unevenness on the toner surface becomes remarkable. Regarding the effect of the toner shape on the image characteristics, the toner transfer efficiency can be greatly improved by making the toner shape spherical. In the case of irregular-shaped toner such as pulverized toner, in roller transfer,
When the transfer roller pressure is high, the toner is mechanically pressed against the photoreceptor, resulting in poor transfer.
Are easily generated, but with the spherical toner, the "missing of characters" hardly occurs. As a method for obtaining such a spherical toner, a method for obtaining a polymerized toner is preferable. Among them, a fine particle toner having a spherical particle size distribution of 4 to 8 μm having a sharp particle size distribution can be obtained relatively easily under normal pressure. A suspension polymerization method under pressure or under pressure is particularly preferred.

That is, as a part of improving the image quality of electrophotography in recent years, it has been required to reduce the particle size of the toner. However, the energy required to pulverize the particles is proportional to the square of the toner particle size. Therefore, it is difficult to reduce the particle size of the toner by a pulverization method. On the other hand, in the polymerization method, toner particles are generated by using a chemical reaction, so that the particle size of the toner can be easily reduced, and a sharp particle size distribution can be easily obtained. Therefore, the spherical toner obtained by the polymerization method is suitable for high quality image formation.

Further, according to the suspension polymerization method, it is possible to encapsulate a substance having a low softening point. Specifically, the polarity of the material in the aqueous medium is set smaller for the low softening point substance than for the main monomer, and a small amount of a large polar resin or monomer is further added, so that the low softening point is reduced. A toner having a so-called core / shell structure in which a substance is coated with an outer shell resin is obtained. In a polymerized toner having such a core / shell structure, by using a low softening point substance as a core substance,
Heat fixation with a smaller amount of heat than before can be performed. Furthermore,
By using a highly releasable substance as the core substance, it is also possible to prevent toner from adhering to the fixing roller. This eliminates the need to apply a release agent such as silicone oil to the fixing device, thereby simplifying the configuration of the fixing device, and reducing the cost and maintenance of the fixing device.

Further, the toner surface is coated with an external additive,
By providing a minute gap between the toners or between the photoconductors, it is possible to further improve the fluidity of the polymerized toner and to improve the transfer efficiency to nearly 100%.
In that sense, the coverage of the external additive on the toner surface is 5 to 99%.
%, More preferably 10 to 99%. The external additive coverage on the toner surface was determined by Hitachi F
Using an E-SEM (S-800), 100 toner images are randomly sampled, and the image information is sent via an interface to an image analyzer (Luzex3) manufactured by Nireco.
, And is calculated by performing analysis.

The external additive used at this time preferably has a particle size of 1/3 or less of the weight average particle size of the toner particles from the viewpoint of durability when added to the toner. The particle size of the additive means an average particle size obtained by observing the surface of the toner particles with an electron microscope. As the external additive, for example, aluminum oxide, titanium oxide, strontium titanate, cerium oxide, magnesium oxide,
Metal oxides such as chromium oxide, tin oxide and zinc oxide; nitrides such as silicon nitride; carbides such as silicon carbide; metal salts such as calcium sulfate, barium sulfate and calcium carbonate; fatty acid metals such as zinc stearate and calcium stearate Salt, carbon black, silica and the like are used. These external additives are used in an amount of 0.01 to 100 parts by weight of the toner particles.
About 10 parts by weight is used, preferably 0.05 to 5 parts by weight.
Parts by weight are used. These external additives may be used alone or in combination. Each of which has been subjected to a hydrophobic treatment is more preferable.

To summarize the above, first, the following merits (1) and (2) can be obtained by using a spherical toner. (1) Improvement of transfer efficiency (2) Improvement of omission during transfer Further, by manufacturing the spherical toner by a polymerization method,
The following (3) and (4) can be performed. (3) Easy to reduce toner particle size (4) Sharp particle size distribution (sharp tribo distribution) Further, by giving the toner a core / shell structure by a suspension polymerization method as a polymerization method, (5) and (6) are achieved. (5) Simultaneous improvement of fixing performance and blocking resistance (6) Simplification of the oil applying member in the fixing unit by using a release agent for the core As a result, high image quality and low cost of the entire image forming apparatus are achieved. Is achieved.

[0016]

However, in a conventional one-component developing device using a one-component developer (hereinafter, simply referred to as a one-component developing device), image density and toner adhesion (fogging) to a non-image portion are considered. In order to obtain good developing characteristics such as toner scattering, it is necessary to uniformly rub the toner on the developing sleeve by the regulating member, and to form a stable toner thin layer by triboelectric charging. In a conventional developing device using a non-magnetic one-component developer, a non-magnetic developer supply member 105 is used.
Therefore, it is necessary to supply a new toner layer onto the developing sleeve after removing the toner on the developing sleeve 102 once and removing the past toner history. At this time, if the toner on the developing sleeve 102 cannot be completely peeled off, charge-up of the toner or image unevenness in halftone occurs, and the image quality is remarkably deteriorated. On the other hand, when a spherical toner such as the polymerized toner described above is used as a one-component developer, particularly, a non-magnetic one-component developer, the following problems occur.

First, since the spherical toner such as the above-mentioned polymerized toner has a spherical shape, the friction is small and slippery as compared with a pulverized toner having an irregular shape and many irregularities. Slip is removed and developer carrier 1
02 and a uniform thin toner layer (toner application amount 0.3-1.
0 mg / cm ² ). And
The developer regulating member 103 is not frictionally charged with the developing sleeve.
Does not adhere to the developing sleeve with a mirror image force, and scatters from the developing sleeve, contaminating the image forming apparatus or deteriorating the quality of an output image.

Second, since the spherical toner is spherical, the friction is small and easy to slip compared with the pulverized toner having an irregular shape and a lot of irregularities. Developing sleeve 1 by member 105
02 becomes difficult to mechanically peel off from above. Therefore, a residual toner layer is formed on the developing sleeve 102, and supply of new toner by the developer supply member 105 is hindered. For this reason, charge-up of the toner on the developing sleeve and a decrease in the amount of toner coating occur, and various image deteriorations are caused by coat unevenness and coat failure.

Third, since the spherical toner is spherical, there is a problem that the triboelectric charge is reduced. On the other hand, in a non-magnetic one-component developing device, in particular, unless sufficient tribo is given to the spherical toner, the amount of toner coating on the developing sleeve is reduced or becomes non-uniform, and the image density is reduced. As the image unevenness of the halftone image, the quality of the output image is significantly reduced.

Further, in the case of the polymerized toner having the core / shell structure described above, the above-mentioned merits exist, and although the low softening substance in the toner can lower the fixing temperature of the toner, Since the strength of the toner itself is reduced, it is necessary to bring the developing blade and the developer supply roller into contact with the developing sleeve with a low contact pressure, and the regulation of the developer performed when the toner thin layer is formed, Stripping off the toner on the developing sleeve has become more difficult. That is, although making the toner spherical has an advantage at the time of transfer, at the same time, the above-mentioned various problems occur at the time of development, which makes it difficult to optimize the entire image forming apparatus.

Accordingly, an object of the present invention is to achieve both the stable formation of a thin toner layer on the developing blade during development and the realization of stable tribo-attachment to toner and the achievement of high transfer efficiency during transfer. It is an object of the present invention to provide an image forming apparatus capable of easily obtaining a high-quality output image.
It is another object of the present invention to provide an image forming apparatus capable of easily obtaining a high-quality stable color output image in which the size of the apparatus is reduced and the toner is effectively used.

[0022]

The above object is achieved by the present invention described below. That is, the present invention provides an image carrier,
In an image forming apparatus including developing means for visualizing a latent image on an image carrier with a one-component developer and transfer means for transferring the visualized toner image on the image carrier to a material to be transferred, an image forming apparatus includes: toner shape factor SF ₁ of the one-component developer, an image forming apparatus characterized by being configured to be smaller than the toner shape factor SF ₁ in the developing unit.

[0023]

Next, the present invention will be specifically described with reference to preferred embodiments. The present inventors have conducted intensive studies to solve the above-mentioned problems of the prior art, and as a result, have developed a developing means for developing a latent image on an image carrier using a one-component developer, and a developing means for developing a latent image on the image carrier. an image forming apparatus comprising a transfer means for transferring a toner image, the toner shape factor SF ₁ of a one-component developer at the time of transfer, if configured to be smaller than the toner shape factor SF ₁ in the developing means, Since the shape of the toner used in the developing means is non-spherical, friction and rubbing of the toner can be facilitated unlike the case where spherical toner is used, and the thin toner layer on the surface of the developing blade can be formed. The formation is facilitated, and the triboelectricity of the toner is improved. On the other hand, the present inventors have found that, at the time of transfer, the toner shape factor SF ₁ is reduced and the shape of the toner used for transfer is made spherical, so that transfer efficiency can be improved and transfer dropout can be prevented. Reached.

In addition, at least two kinds of particles of a first external additive having the same polarity as the toner and a second external additive having the opposite polarity to the toner are externally added to the one-component developer. And the first external additive can improve the chargeability and fluidity of the toner, and separate the second external additive from the one-component developer by an electric field applied during development and transfer. It is possible to appropriately control the shape factor SF _{1 of the} toner by changing the shape of the one-component developer in the developing means and the shape of the one-component developer at the time of transfer. Was found. Thereby, the image forming apparatus of the present invention having the above-described configuration can be easily obtained.

Preferably, in the above case, if the area coverage α of the second external additive having a polarity opposite to that of the toner on the surface of the one-component developer is 50% or less, the one-component developer Can be stably charged to the original charging polarity, and both the image density and the non-image area fog can be improved.

Further, the weight mixing ratio of the first external additive to the developer is M ₁ , the weight mixing ratio of the second external additive to the developer is M ₂ , and the first external additive is triboelectrically charged. When the absolute value of the amount is Q ₁ , the absolute value of the triboelectric charge amount of the second external additive is Q ₂ , and the area coverage α of the second external additive on the one-component developer surface, Has a relationship of Q ₁ × M ₁ × α <Q ₂ × M ₂ , during development and transfer, the second external additive having the opposite polarity to that of the toner is favorably removed from the one-component developer. Therefore, the effect of the present invention described above can be further improved.

In the image forming apparatus of the present invention, the first external additive preferably has a primary particle size of 1 nm to 10 nm.
By using the second external additive having a primary particle size of 0.1 to 2 μm, good transferability is achieved by the presence of the first external additive. By using the external additive described above, it is possible to perform more favorable toner charging and toner regulation. That is, by using a second external additive having a large primary particle size of 0.1 to 2 μm, the toner shape factor SF ₁ can be increased in value and made non-spherical, Second during development / transfer
Can be easily separated. By setting the primary particle size of the first external additive to 1 nm to 100 nm, which is smaller than that of the second external additive, good transfer characteristics can be obtained.

Further, in the image forming apparatus of the present invention,
Before the external additive as described above is added to the shape of the one-component developer to be used, the shape factor SF1 is ₁₀₀ to ₁
30, SF ₂ is used which satisfies the 100-120, in the after addition of the first external additive and the second external additive, the shape factor SF ₁ is 130 to 170, SF ₂ is 120 to
By using the toner satisfying 160, it is possible to achieve high transfer efficiency and to perform stable toner charging property and toner regulation in the developing unit.

In the present invention, by using a one-component developer partly or wholly formed by a polymerization method, a toner having a small particle size and a sharp tribo distribution suitable for the present invention can be produced at low cost. And an economically useful image forming apparatus can be obtained. Further, at that time, if a part or the whole of the one-component developer is composed of a low softening point substance having a melting point of 40 to 90 ° C., it is possible to achieve both a reduction in fixing temperature and anti-blocking performance, Further, the amount of the release agent applied to the fixing roller can be reduced.

Further, in the image forming apparatus of the present invention,
By disposing the developer carrying member and the image carrying member facing each other with a certain developing gap, and forming an alternating electric field in the developing gap,
When the one-component developer having the above-described configuration and suitable for the present invention is reciprocated between the developer carrier and the image carrier (hereinafter, this is referred to as a jumping development method), the alternating electric field causes The second external additive having the opposite polarity can be effectively separated from the one-component developer during development. or,
At this time, the amplitude of the alternating electric field applied to the interval between the developer carrier and the image carrier is set to 2 kV / mm to 5 kV / mm, so that the second external additive having the opposite polarity to the toner can be one component. As a result, the transfer efficiency can be improved as a result of sufficient separation from the developer.

In the image forming apparatus of the present invention, the one-component developer remaining on the image carrier after the transfer is recovered by the developing means, whereby a one-component developing apparatus employing a cleanerless system is obtained. The apparatus can be reduced in size and the toner can be effectively used.

The method for measuring the triboelectric charge used in the present invention will be described below. FIG. 8 is an explanatory diagram of an apparatus for measuring a triboelectric charge amount of a toner. First, there is 500
Metal measuring container 42 with mesh screen 43
Into the metal lid 44.
do. At this time, as the two-component developer to be put in the container, one that is put in a polyethylene bottle having a volume of 50 to 100 ml and shaken by hand for about 10 to 40 seconds is used. Then, the entire measuring container 42 at this time is weighed and W ₁ (k
g). Next, in the suction device 41 (at least a portion in contact with the measurement container 42 is an insulator), the air is suctioned from the suction port 47 and the air volume control valve 46 is adjusted to reduce the pressure of the vacuum gauge 45 to 25.
It is 0 mmAq. In this state, suction is performed sufficiently, preferably for 2 minutes, to remove the resin by suction. Electrometer 49 at this time
Is V (volt). Here, reference numeral 48 denotes a capacitor whose capacity is C (F). In addition, the whole measurement container 42 after suction is weighed to be W ₂ (kg). The triboelectric charge of the toner is calculated by the following equation.

[0033]

(Equation 2)

[0034]

The present invention will be described below in more detail with reference to examples of the present invention. Embodiment 1 FIG. 1 shows an image forming apparatus of the present embodiment. First, a photosensitive drum 10 as an image carrier shown in FIG. 1 has a peripheral speed of 100 mm / sec. , And is set to a surface potential of −700 V by the primary charger 13. Then, on the photosensitive drum 10, the exposing means 1
Exposure corresponding to the document image is performed by 4 to form an electrostatic latent image. Here, the bright portion potential as the image portion is −15.
0V, and the potential of the dark portion, which is a non-image portion, is -700V. A developing device 40 is provided so as to face the photosensitive drum 10. The developing device 40 has a developing sleeve 3 for carrying a developer.
The photosensitive drum 10 is arranged with a gap of 250 μm. Then, the toner carried on the developing sleeve 3 is caused to fly by an electric field generated by the developing power supply 4, and the electrostatic latent image on the photosensitive drum 10 is converted into a toner image. Further, the toner image on the photosensitive drum formed as described above is
The toner image is transferred onto the transfer paper by the transfer charger 11, and then heated and pressed by fixing means (not shown) to be fixed on the transfer paper. At this time, the transfer charger 11 is controlled so that a corona discharge current of 60 μA flows to the drum side of the transfer paper, and a sufficient positive charge is applied to the back surface of the transfer paper. In addition, the photosensitive drum 10 is not transferred to the transfer sheet.
The toner remaining on the surface is peeled off from the surface of the photosensitive drum by the cleaning device 12 and removed.

Hereinafter, the developing device 40 used in the image forming apparatus of this embodiment will be described in detail. A toner stirring member 6 is provided in a developer container of the developing device 40.
The toner stirring member 6 rotates in the direction of the arrow in the figure, and conveys the toner in the developer container toward the developing sleeve 3 and the developer supply roller 5. The developing device 40 has, as a developing sleeve, a conductive cylindrical sleeve 3 made of aluminum and having a diameter of 16φ. The developing sleeve is separated from the opposing photosensitive drum 10 by a gap regulating member (not shown) at a distance of 250 μm. Is kept.

A developer supply roller 5 made of urethane sponge is in contact with the developing sleeve 3. The developer supply roller 5 has a diameter of 8 mm, and is in contact with the developing sleeve 3 at a penetration amount of 1 mm, as shown in FIG. 1, and has a peripheral speed in the counter direction with the developing sleeve 3 by a gear (not shown). 50 mm / sec. It is driven by. As described above, the developer supply roller 5 is
The developer supply roller 5 removes the toner history (a so-called ghost) on the developing sleeve 3 and supplies new toner onto the developing sleeve 3 at the same time. The developer supply roller 5 is made of open-cell sponge and has a low hardness of 20 ° in Asker C hardness. As the developer supply roller 5 is softer, the deterioration of the toner at the time of supplying or removing the toner can be suppressed.

The developing sleeve 3 is in contact with a developer regulating member 1 as a member for regulating the amount of toner. The developer regulating member 1 frictionally charges the toner carried on the developing sleeve 3 to form a toner having a polarity and a charge amount suitable for development, and forms a thin toner layer 7 on the developing sleeve 3. , Development area (drum facing position)
The amount of toner conveyed to the printer is regulated. Then, the toner conveyed to the developing area by the developing sleeve 3 is applied to a developing power source 4 applied to the developing sleeve 3 during development.
Is developed from the developing sleeve 3 onto the photosensitive drum 100 by the developing electric field generated between the photosensitive drum 100 and the latent image on the photosensitive drum 100.
The upper latent image is visualized as a toner image.

In the present embodiment, a spherical toner obtained by subjecting a pulverized toner produced by a pulverizing method to a spheroidizing process was used as a main component of a one-component developer mounted on an image forming apparatus having the above-described configuration. . The one-component developer used in the present embodiment is a negatively-chargeable non-magnetic one-component developer, and a spherical toner obtained by spheroidizing a pulverized toner by a method described later, a negatively-charged first external additive, The two external additives of the positively chargeable second external additive are externally added. Hereinafter, the one-component developer used in the present example will be described in detail.

In the method for producing the one-component developer of the present invention, a resin having a styrene-acryl copolymer as a main component is used as a binder resin, and a releasing agent which is a substance having a low softening point, a coloring agent, After adding carbon black as an agent and a metal complex salt of a monoazo dye as a charge control agent and uniformly dispersing them using a pressure kneader, an extruder or a media disperser, the target is mechanically or under a jet stream. And pulverized to a desired toner particle size, followed by plastic sphering. Then, through a classification process, the particle size distribution is sharpened to obtain a toner.

Specific examples of the apparatus for performing the plastic sphering process include “Hybridization System” by Nara Machinery Co., Ltd. and “Turbo Mill” by Turbo Kogyo Co., Ltd. A blade is mounted on the rotating plate, and when the rotating plate rotates at high speed, the toner in the circulating airflow collides with the blade rotating at high speed. At this time, the convex portion of the toner undergoes plastic deformation due to impact energy and is smoothed, and the toner as a whole undergoes a spherical shape change. In addition, as a means for spheroidizing at this time, in addition, the surface of the toner is melted and spheroidized by hot air using a spray dryer, or the surface is melted and spheroidized by dispersing the toner in a hot air flow. A method and the like have been proposed, and a spheroidized toner created by such a manufacturing method may be used in the present embodiment.

The developer used in this example was specifically manufactured as follows. First, according to the above manufacturing method, the toner has a mean particle diameter of 8 μm and a shape factor SF ₁ = 1 of the toner.
15. A spherical toner having an SF _{2 of} 110 was obtained. This spherical toner has a triboelectric charge of −38 μC according to the above-described measurement method.
/ G. When measuring the triboelectric charge, a particle size of 5
The external additive was added in 9.7 g of a 0 μm ferrite carrier.
After mixing 3 g and shaking 300 times in a polyethylene container, the measurement was performed.

In this embodiment, the spherical toner 1
1.5 wt% of a negatively chargeable external additive having the same polarity as that of the toner, and 0.8% of a positively chargeable external additive having a polarity opposite to that of the toner. Attached to each toner particle surface, as shown in FIG.
A non-spherical spherical toner was used. Toner shape factor of spherical toner T ₁ of the after externally added the two types of the external additive, SF ₁ = 150, and was SF ₂ = 135.

In the present embodiment, a hydrophobic silica having a specific surface area of 300 m ² / g and a primary particle size of 8 nm as measured by the BET method was used as a negatively chargeable external additive (first external additive). And the triboelectric charge was -110 [mu] C / g. The effect of the negatively chargeable external additive having the same polarity as that of the toner is to impart the effect of the conventional external additive to the toner, such as improvement of the chargeability of the toner and improvement of the fluidity of the toner. .

Further, a positively chargeable external additive (second external additive)
, PMMA particles having a primary particle size of 0.5 μm were added. The triboelectric charge of the positively chargeable external additive used in this example was +40 μC / g. The function of the positively chargeable external additive having a polarity opposite to that of the toner is as follows. By attaching particles having a primary particle diameter of 0.5 μm to the spherical toner, the toner shape is appropriately made non-spherical, and the slipperiness of the toner is controlled. To make it possible. As a result, the toner does not slip through the developing blade, and it is possible to obtain a good toner charge and a uniform thin toner layer. In addition, since the toner does not slip through the developer supply roller, charge-up of the toner on the developing sleeve is prevented, and image reproducibility is improved.

Here, the negatively chargeable external additive and the positively chargeable external additive on the surface of the toner T ₁ are schematically shown in FIG.
It exists as shown in FIG. In the present invention, at this time, by setting the coverage α of the positively chargeable external additive to 50% or less, the tribo of the entire toner including the external additive can be stably negatively charged. A good image with less fog can be obtained. According to the measurement method described above,
The external additive coating ratio of the spherical toner T ₁ surface used in this example, negatively charged external additive is 80%, the positive charging external additive was 22%.

Further, in the present invention, in order to enhance the effect of the positively chargeable external additive adhering to the toner surface, it is necessary to use FIG.
As shown in (a), even if a negatively chargeable external additive adheres to the surface of each particle of the positively chargeable external additive, the positively chargeable external additive itself preferably exhibits positive characteristics. In particular,
The absolute value of the triboelectric charge of the negatively chargeable external additive is Q ₁ , the external addition amount is M ₁ , the absolute value of the triboelectric charge of the positively chargeable external additive is Q ₂ ,
When the external additive amount M ₂ and the area coverage α of the positively chargeable external additive on the surface of the toner T ₁ are satisfied, the following condition is satisfied: Q ₁ × M ₁ × α <Q ₂ × M ₂ I do. This makes it possible to stably charge the positively chargeable external additive to a positive polarity, facilitate separation of the positive external additive during development / transfer, and stably obtain the effects of the present invention. Become.

Further, it has been found that it is preferable to use particles having a large particle size, which are not spherical but amorphous, as the positively chargeable external additive (second external additive). By doing so, it is possible to control the slipperiness of the toner even with a small external addition amount. Further, as described above, by setting the primary particle size of the positive external additive to 0.1 to 2 μm, the toner shape factor SF ₁ can be easily increased to be non-spherical, and at the time of development / transfer, The positive external additive was easily separated from the toner surface. As for the negatively chargeable external additive (first external additive), good transfer characteristics were achieved by using a primary particle having a primary particle diameter of 1 nm to 100 nm.

In the present invention, by adding a positively chargeable external additive, the shape factor SF ₁ of the toner is increased, and the toner is made non-spherical, so that good toner coatability during development is obtained. At the same time, by optimizing the jumping development method, as shown in FIG. 2B, the toner forming the toner image obtained by developing the latent image on the photosensitive drum is used to remove the positively chargeable external additive from the toner. by separating from, the lower the value of the toner shape factor SF ₁ during transfer spheronized, improvement of transfer efficiency, may improve the prevention of dropout during the transfer.

For this reason, in the present embodiment, the developing bias is applied to the developing sleeve 3 by 1.5 kV from the developing power source.
_pp , by applying an AC voltage having a frequency of 2 kHz and a DC voltage of -500 V, a 250 μm
The toner is caused to fly to the electrostatic latent image on the photosensitive drum facing the photoconductive drum with a gap of m, thereby forming a toner image.

[0050] As shown in FIG. 3 (a), the image portions V _L on the photosensitive drum 10 and the developing sleeve 3 by the alternating electric field according to the jumping developing method, in between the non-image portion V _d, toner - metastasis and By causing the reverse transition, the positively chargeable external additive (second external additive) is effectively separated from the negatively chargeable toner surface and collected on the developing sleeve 3 or the non-image portion. This is because the toner that has once adhered to the image portion on the photosensitive drum 10 can be caused to fly again to the developing sleeve 3 side by applying an appropriate alternating electric field, so that the positively chargeable external additive can be used. It is considered that the chance of separating the agent from the toner surface is increased, and the agent can be more reliably separated. Also, according to this jumping development, the normally charged negative polarity toner produces an appropriate edge effect on the image area, so that a sharp edge sharpness and a halftone image which is a latent image close to the non-image area are obtained. The reproducibility is improved, and the positive polarity toner can be collected in the developing sleeve 3.
The occurrence of fog in the non-image area can be reduced as compared with the developing method.

FIG. 3 (b) shows a DC-free DC voltage.
The bias conceptual diagram of the developing method is as follows. The potential of the developing sleeve is V _dc = −500 V, and the potential of the image portion on the photosensitive member is _VL.
= -150 V and the potential of the non-image portion is V _d = -700 V, the normally charged negative toner adheres to the image portion of the latent image on the photosensitive drum to form a toner image. However, since the toner does not reciprocate due to a strong electric field as shown in FIG. 3A, the positively chargeable external additive cannot be sufficiently removed from the toner once adhered to the drum. Further, the positively charged toner having the opposite polarity adheres to the non-image area, easily forms so-called image fog, and deteriorates image quality.

[0052] Here, the amplitude of the alternating electric field relationship of SF ₁ and the transfer efficiency of the developer will be described using as a developing electric field in the present invention. Here, assuming that the developing electric field amplitude A is a peak-to-peak AC voltage V _pp of the developing power source and the distance between the developing sleeve and the photosensitive drum is SD, the following relationship is obtained. A = V _pp / 2SD

As shown in FIG. 4, the DC developing method (FIG.
(Where the amplitude of the developing electric field is 0 kV / mm), the shape factor of the toner on the drum after development and before transfer is SF ₁ = 150
And was substantially the same as the toner in the developing device. As a result, the transfer efficiency was only 77%. On the other hand, as can be seen from FIG. 4, by forming an alternating electric field in the developing gap and making the developing electric field amplitude 2 kV / mm or more, the positively chargeable external additive is separated from the toner surface, and the toner before transfer is transferred. the shape factor SF ₁ was reduced to 130 or less. as a result,
The transfer efficiency was improved to 95% because the toner was transferred after being made into a sphere (see the graph indicated by x in the figure). At this time, if the amplitude of the developing electric field is 5 kV / mm or more, a leak occurs depending on the latent image condition. Therefore, it is desirable that the amplitude of the developing electric field be 2 kV / mm or more and 5 kV / mm or less.

Here, the spherical toner used in the present invention has a shape factor SF ₁ of 100 to 13 before external addition.
0, SF ₂ is in the range of 100 to 120, and a first external additive and a second shape factor SF ₁ after the external additive is externally added is 130 to 170, the range of SF ₂ are 120 to 160 When using the spherical toner having a developing electric field amplitude in the above range, it was possible to achieve both toner coating and transfer efficiency during development.

That is, by configuring as in this embodiment,
In the developing means of the image forming apparatus, the toner shape coefficient S
Since the value of F ₁ becomes larger non sphering toner, it is possible to facilitate the friction and rubbing of the toner, the toner thin layer formed is easily made, and triboelectric charge-imparting ability can be improved with the toner in the developing blade Therefore, the toner remaining on the developing sleeve of the toner supply member can be reliably removed. On the other hand, during transfer of the toner image formed on the photosensitive drum, that the toner is sphered by lowering the toner shape factor SF _1, occurs at the time of transfer, improvement in transfer efficiency, to improve the prevention of dropout during transfer It becomes possible.

Embodiment 2 The image forming apparatus of this embodiment is a cleanerless type image forming apparatus, and a polymer toner having a core / shell structure, which is a one-component developer, is applied to the image forming apparatus.
Hereinafter, it will be described in more detail with reference to FIG. The configuration of this embodiment is basically similar to that of the first embodiment,
As shown in FIG. 5, there is no cleaning device for collecting the residual toner on the photosensitive drum 10 after the transfer, and the residual toner is negatively charged by the primary charger 13 and then collected by the developing unit. It is a cleanerless system.
Therefore, the cleanerless system has the advantages that the size of the image forming apparatus can be reduced and the toner can be effectively used. However, in the cleanerless system, when a large amount of toner remaining on the photosensitive drum 10 is present, the photosensitive drum 1 is not used in the next image forming process.
In some cases, an image failure may occur due to a charging failure or exposure failure of 0. Therefore, in order to obtain a stable cleanerless system, it is desired to increase the transfer efficiency to nearly 100%.

In the present embodiment, when the one-component developer to be used is manufactured, the above-mentioned suspension polymerization method capable of easily obtaining the spherical toner capable of obtaining high transfer efficiency is used. At the same time, the toner particle diameter distribution is sharpened to achieve high definition of the image, and the toner is provided with a core / shell structure by a suspension polymerization method, thereby improving the fixing property. Achieved compatibility of blocking resistance. Furthermore, by using a release agent for the core at this time, the oil application member in the fixing section of the conventional apparatus can be simplified.

[0058] The polymerized toner T ₂ will be described with reference to the embodiment below. The toner T ₂ in this example is a toner manufactured by a suspension polymerization method, and was obtained as follows. First, 0.1 M-N was added to 710 g of ion-exchanged water.
450 g of an aqueous solution of a ₃ PO ₄ was added, and the mixture was heated to 60 ° C., and then, using a TK homomixer (manufactured by Tokushu Kika Kogyo),
The mixture was stirred at 12,000 rpm. 1.0M-C
68 g of an aCl ₂ aqueous solution was gradually added to obtain an aqueous medium containing Ca ₃ (PO ₄ ) ₂ .

Next, the following formulation was heated to 60 ° C.
12,0 using a homomixer (manufactured by Tokushu Kika Kogyo)
It was uniformly dissolved and dispersed at 00 rpm. (Monomer) Styrene 165 g n-butyl acrylate 15 g (charge control agent) salicylic acid metal compound 3 g (polar resin) saturated polyester (acid value 14, peak molecular weight: 8,000) 10 g (colorant) carbon black 10 g (release agent) 15 g of ester wax (melting point 70 ° C)

Next, 2,2 ′, which is a polymerization initiator, is added thereto.
-Azobis (2,4-dimethylvaleronitrile) 10 g
Was dissolved to prepare a polymerizable monomer composition. The above polymerizable monomer composition was charged into the aqueous medium obtained above,
Under a N ₂ atmosphere at ℃ 1 with a TK homomixer
The mixture was stirred at 000 rpm for 10 minutes to granulate the polymerizable monomer composition. Then, while stirring with paddle stirring blades, 8
The temperature was raised to 0 ° C., and the reaction was performed for 10 hours.

After the completion of the polymerization reaction, the remaining monomer was distilled off under reduced pressure. After cooling, hydrochloric acid was added to dissolve the calcium phosphate, followed by filtration, washing with water and drying to give a weight average diameter of about 7.5.
μm sharp colored suspension particles were obtained. Polymerization shape of the toner T ₂ are used in this embodiment obtained in this way,
A spherical polymerized toner having shape factors SF ₁ = 110 and SF ₂ = 109 was obtained. Further, the frictional charge amount of the toner T ₂ are -30
μC / g.

Here, when the surface portion of the toner is formed by a polymerization method, pre-toner (monomer composition) particles are present in a dispersion medium and necessary portions are formed by a polymerization reaction. Is considerably smoothed, so that the slipperiness of the toner is very high. Therefore, it is difficult to regulate the toner applied on the developing blade to a uniform toner layer and a uniform charge amount (hereinafter, simply referred to as regulation and charging).
Further, if the polymerized toner has a core / shell structure, the above-mentioned advantages can be obtained. However, since the low-softening substance in the toner lowers the strength of the toner itself, the developing blade and the developer supply roller are low. It is necessary to contact the developing sleeve with the contact pressure, which makes it more difficult to regulate and peel off the developing sleeve, and to perform cleaning with a blade.

Accordingly, the polymerized toner T ₂ used in this embodiment is replaced with the polymerized toner T ₂ 100 obtained as described above.
1.8 parts by weight of a negatively chargeable external additive having the same polarity as that of the toner and 0.8% of a positively chargeable external additive having a polarity opposite to that of the toner are added to the parts by weight. Add
As in the case of Example 1, these external additives are adhered to the surfaces of the respective toner particles. Here, a hydrophobic external silica having a specific surface area according to the BET method of 300 m ² / g and a primary particle size of 8 nm was used as the first external additive having a negative chargeability, and the triboelectric charge measured by a blow-off method. Is -1
It was 10 μC / g. The effect of the addition of the negatively chargeable external additive having the same polarity as that of the toner is to impart the effect of the conventional external additive such as improvement of toner chargeability and toner fluidity to the toner. .

On the other hand, in this embodiment, as the second external additive having a positive chargeability, melamine having an average particle size of 1 μm was used.
Formaldehyde resin particles were added. The triboelectric charge of the positively chargeable external additive in this example was +55 μC / g. A toner and opposite polarity as the effect of the addition of the positive charge external additive, a slip of the control of the toner in the same manner as in Example 1, by increasing the toner shape factor SF ₁ in the developing device nonspherical Thus, regulation of toner and stabilization of charging in the developing blade and easy removal of residual toner on the developing sleeve in the developer supply roller are facilitated. Further, in this embodiment, the toner T ₂ on the photosensitive drum is developed by developing on the photosensitive drum under a predetermined alternating electric field.
A good transfer characteristic is obtained by removing the positively chargeable external additive from the mixture and making the mixture spherical.

In this embodiment, by increasing the particle size of the positively chargeable external additive and increasing the triboelectric charge amount, even if the value of SF ₁ and SF ₂ is close to 100, even in the case of the polymerized toner T ₂ , 1 of the spherical toner T ₁ has become possible to control the same manner slipperiness. Further, since the area coverage α of the positively chargeable external additive with respect to the toner surface used in this embodiment is 14%, the amount of the positively charged reversal toner is very small, and a stable toner tribo is obtained even in long-term durability. Was. Absolute value Q ₁ of the triboelectric charge amount of the negatively chargeable external additive, the external additive amount M ₁ , absolute value of the triboelectric charge amount of the positively chargeable external additive Q ₂ , external additive amount M ₂ , positive chargeable external additive Coverage α of toner in toner T ₁ surface
In order to satisfy the condition of Q ₁ × M ₁ × α <Q ₂ × M ₂ , the positively chargeable external additive is stably charged to the positive polarity, and the positive external additive during development / transfer is charged. Separation is facilitated, the toner shape factor is reduced at the time of transfer, and the toner is made spherical to improve transfer efficiency.

In this embodiment, the same developing conditions as in Embodiment 1 (developing gap distance 250 μm, AC voltage 1.5 kV _pp
(2 kHz), an appropriate alternating electric field is applied to the toner, so that the latent image on the photosensitive drum is sufficiently developed and the positively chargeable external additive is removed from the toner on the photosensitive drum. In this embodiment, the polymerization toner T ₂ in the developing device is used.
Is the shape factor SF ₁ of the polymerized toner T ₂ on the photosensitive drum image portion after development and before transfer, while the shape factor S ₁ is 145.
F ₁ = 113 and the transfer efficiency was 98%. or,
A small amount of the inverted toner charged to the opposite polarity can be returned to the developing sleeve side by the alternating electric field, as in the first embodiment, to prevent image fog.

Therefore, the image forming apparatus of the present embodiment stably coats the polymerized toner on the developing sleeve and transfers the image even though the non-magnetic one-component developing apparatus having a simple structure is used. In some cases, the transfer efficiency can be improved, so that the toner can be easily collected in the developing unit in the cleanerless system, and an image forming apparatus that realizes a stable cleanerless system without causing image defects for a long period of time is provided. As a result, downsizing of the apparatus and effective use of toner are achieved.

[0068]

As described above, according to the present invention,
Formation of a stable thin toner layer on the developing blade at the time of development, and realization of stable tribo application to the toner,
An image forming apparatus that achieves both high transfer efficiency at the time of transfer and easily obtains a high-quality output image is provided. Further, according to the present invention, there is provided an image forming apparatus capable of easily obtaining a high-quality stable color output image in which the size of the apparatus is reduced and the toner is effectively used.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment.

FIG. 2 is a conceptual diagram illustrating a surface state of a developer used in the present invention. (A) is before development and (b) is after development.

FIG. 3 is a conceptual diagram of a developing bias in the image forming apparatus of FIG.

FIG. 4 is a diagram illustrating a relationship between a developing electric field amplitude, a developer shape, and transfer efficiency.

FIG. 5 is a schematic configuration diagram of an image forming apparatus according to a second embodiment.

FIG. 6 is a schematic configuration diagram of a conventional electrophotographic apparatus.

FIG. 7 is a schematic configuration diagram of a conventional developing device.

FIG. 8 is a schematic configuration diagram of a frictional charge amount measuring device.

[Explanation of symbols]

T ₁ : spherical toner T ₂ : polymerized toner 1: developer regulating member 2: thin metal plate 3: developing sleeve 4: developing power supply 5: developer supply roller 6: developer agitator 7: toner thin layer 10: photosensitive drum 11 : Transfer charger 12: Cleaning device 40: Developing device 41: Suction device 42: Measurement container 43: Conductive screen 44: Lid 45: Vacuum gauge 46: Air flow control valve 47: Suction port 48: Condenser 49: Electrometer 100: Photosensitive drum 102: Developing sleeve 103: Developing blade 104: Thin metal plate 105: Developer supply roller 106: Toner stirring member 107: Toner thin layer 114: Transfer charger 116: Cleaning device 117: Primary charger 123: Exposure device 126: Fixing device 140: developing device 140a: developing container T: developer (toner) P: transfer material

Claims (12)

[Claims] An image carrier, a developing unit for visualizing a latent image on the image carrier with a one-component developer, and a transfer unit for transferring the visualized toner image on the image carrier to a material to be transferred. An image forming apparatus provided with the image forming apparatus, wherein the toner shape factor SF ₁ of the one-component developer at the time of transfer is configured to be smaller than the toner shape factor SF ₁ in the developing unit. apparatus. 2. The one-component developer according to claim 1, wherein at least two kinds of particles of a first external additive having the same polarity as the toner and a second external additive having the opposite polarity to the toner are externally added. Item 2. The image forming apparatus according to Item 1. 3. The image forming apparatus according to claim 2, wherein the area coverage α of the second external additive on the surface of the one-component developer is 50% or less. 4. The weight ratio of the first external additive to one-component developer is M ₁ , the weight ratio of the second external additive to one-component developer is M ₂ , and the first external additive is M 1. Triboelectric charge (C / k
g) is defined as Q ₁ , and the triboelectric charge (C /
When the absolute value of (kg) is Q ₂ and the area coverage of the second external additive on the surface of the one-component developer is α, they are configured to satisfy the following formula: The image forming apparatus according to claim 2 or 3. Q ₁ × M ₁ × α <Q ₂ × M ₂ 5. The primary external additive particles having a primary particle size of 1 nm or more.
100 nm, the primary particle size of the second external additive is 0.1 to 2 μm
The image forming apparatus according to claim 2, wherein 6. one-component developer, the previous shape factor SF ₁ is externally added is 100 to 130, a SF ₂ 100 to 120, the first external additive and a second external additive Shape factor SF ₁ ′ after external addition is 130-170, SF ₂ ′ is 120-
The image forming apparatus according to claim 2, wherein the number is within a range of 160. 7. The image forming apparatus according to claim 2, wherein a part or the whole of the one-component developer is formed by a polymerization method. 8. A part or all of the one-component developer is made of a low softening point substance, and the melting point of the low softening point substance is 40 to 9.
The image forming apparatus according to claim 1, wherein the temperature is 0 ° C. 9. 9. A developing device in which a developing means supplies a one-component developer to a container containing the one-component developer and supplies the one-component developer to an electrostatic latent image formed on an image carrier by rotating in a predetermined direction to visualize the electrostatic latent image. A developer carrier, and disposed opposite to the developer carrier;
A developer supply member for applying the one-component developer onto the developer carrier, and a pressure supply member provided downstream of the developer supply member in the rotation direction of the developer carrier, in pressure contact with the developer carrier; 9. The image forming apparatus according to claim 1, further comprising a developer regulating member for regulating an amount of the developer on the developer carrying member and uniformly applying the developer. 10. A developer carrying member is disposed opposite to the image carrying member with a certain developing gap, and an alternating electric field is formed in the developing gap so that a one-component developer is transferred to the developer carrying member and the image carrying member. The image forming apparatus according to claim 9, wherein the image forming apparatus reciprocates between the two. 11. The amplitude of the alternating electric field is 2 kV / mm to 5 k.
The image forming apparatus according to claim 10, wherein V / mm is set. 12. The image forming apparatus according to claim 9, wherein the developing unit further collects the remaining one-component developer on the image carrier after the transfer.