JP3057101B2 - Image forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method applied to, for example, electrophotography, electrostatic recording, electrostatic printing, and the like.

[0002]

2. Description of the Related Art As a developing method using a magnetic toner having a high resistance, friction between toner particles and friction between the toner particles and a friction member such as a toner carrying carrier (hereinafter, appropriately referred to as a "developing sleeve") are used. There is known a method in which a toner is frictionally charged and developed by contacting the latent image carrier with the toner.
However, in this method, since the number of times of contact between the toner particles and the friction member is small, triboelectric charging tends to be insufficient, and there is a practical problem. Therefore, a method has been proposed in which the number of times of contact between the developing sleeve and the toner is increased by making the developing sleeve carry the magnetic toner extremely thinly. However, even in this technique, it is necessary to apply a large shearing force to the magnetic toner in order to form a thin magnetic toner layer, so that the magnetic toner constituents adhere to the developing sleeve and a filming phenomenon occurs. However, triboelectric charging becomes insufficient, and as a result, there has been a problem that the image density is reduced, toner is scattered, and fog is generated.

On the other hand, in order to form a thin toner layer, it is necessary that the fluidity of the toner is high, but in order to enhance the fluidity of the toner, it is effective to add and mix silica fine powder. is there. However, since the silica fine powder added and mixed is generally hard and fine, when the residual toner is cleaned by a cleaning blade pressed against the photosensitive member, the silica fine powder is sandwiched between the cleaning blade and the latent image carrier, There is a problem that the latent image carrier and the cleaning blade are damaged, and as a result, a high charge always remains in the damaged portion, toner adheres to the damaged portion, and this is transferred, and black spots occur on the image on the transfer material. . In order to solve this problem, inorganic fine particles having a larger particle size than silica fine powder (see JP-A-60-32060 and JP-A-53-81127) and organic fine particles (see JP-A-1-113767) There has been proposed a technique for adding manganese.

[0004]

However, Japanese Patent Application Laid-Open No. Sho 60-3
In the technique of adding inorganic fine particles as disclosed in Japanese Patent No. 2060 and JP-A-53-81127, the inorganic fine particles are hard, larger than the silica fine particles, and have an irregular shape. In addition, since the developing sleeve is worn away and the minute projections and depressions on the surface of the developing sleeve formed by the blasting process disappear, frictional charging with the toner becomes insufficient, resulting in a decrease in image density and fogging. There is. Also, in the cleaning step, there is a problem that the cleaning blade and the latent image carrier are damaged, and as a result, poor cleaning occurs due to black spots and slippage.

On the other hand, in the technique of adding organic fine particles as disclosed in JP-A-1-113767, the organic fine particles have a high resistance,
Because it is not hard enough, when forming a thin layer of toner on the developing sleeve, it electrostatically adheres to the surface of the developing sleeve and further adheres, and as a result, a stable thin layer cannot be formed,
There is a problem that uniform triboelectric charging cannot be performed, image density decreases, and fogging occurs. Also, in the cleaning step, the cleaning properties are low because the organic fine particles are not sufficiently hard, and if the pressing force of the cleaning blade is increased to increase the scraping force, the durability of the blade is significantly reduced, and the latent image carrying The organic fine particles are broken between the body and the blade, and are fixed to the latent image carrier, and as a result, black spots and black lines are generated, and sufficient cleaning properties cannot be obtained.

In order to enhance the cleaning performance, a cleaning roller made of an elastic material is disposed in pressure contact with the surface of the latent image carrier, and the cleaning roller is forcibly slid at a speed relative to the latent image carrier. Means for cleaning residual toner on the latent image carrier by rubbing has also been proposed. In this method, the adhered matter such as toner removed from the surface of the latent image carrier by the elastic roller mostly adheres to the surface of the elastic roller, is carried into the cleaning container, and is pressed by the scraper pressed against the surface of the elastic roller. It is scraped off the surface. However, this method has a problem that the surface of the elastic roller is damaged by the forced rubbing force, and the durability is remarkably reduced, particularly in the case of the magnetic toner. Further, the scraper pressed against the surface of the elastic roller is not perfect, and the toner removed from the surface of the latent image carrier leaks from between the elastic roller and the scraper, contaminating the inside of the image forming apparatus, or removing paper or the like. There is a problem that the image may be stained by dropping on the transfer material. On the other hand, forcible pressure contact damages the surface of the elastic roller, significantly lowers durability, and results in insufficient cleaning performance.

On the other hand, means using a cleaning roller provided with a magnet has been proposed (JP-A-55-98776).
JP-A-57-172381, JP-A-61-84675). According to this means, the durability of the cleaning roller can be improved, and the drop or scattering of the magnetic toner can be prevented. However, there is a problem that the cleaning property is not sufficient because the cleaning roller depends on the polishing action of only the magnetic toner particles. In order to improve this point, a method has been proposed in which inorganic fine particles having a diameter smaller than that of the toner particles are added to the magnetic toner, and this is carried on a cleaning roller to form a magnetic toner layer, thereby enhancing the polishing action in cleaning. I have. But,
In this technique, the inorganic fine particles functioning as a cleaning aid added to the toner do not strongly adhere to the toner particles in order to sufficiently exhibit the polishing action.
It exists in a slightly liberated state. Further, since the diameter is smaller and the specific gravity is larger than the toner particles, every time the cleaning roller rotates, the inorganic fine particles released from the magnetic toner are scattered by the centrifugal force, and the inside of the image forming apparatus, particularly, the transfer electrode and the separation electrode are separated. The wire or the like is contaminated, the transfer current becomes unstable, transfer unevenness or transfer drop occurs, the image quality is significantly reduced, and image unevenness or image drop occurs. Further, the copy image may fall on a transfer material such as paper and stain the copy image.
Further, since the inorganic fine particles are hard and amorphous, the abrasiveness becomes excessive, and therefore the surface of the latent image carrier is damaged,
There is a problem that black spots occur on the image. On the other hand, the toner to which organic fine particles are added has insufficient polishing power,
There is a problem that cleaning failure easily occurs and the characteristics of the photoreceptor deteriorate early. As a result, image defects such as image unevenness and image loss occur.

An object of the present invention is to stably form a good image free from defective cleaning and uneven transfer in an image forming method using a cleaning device having a cleaning roller having a magnet and a cleaning blade. It is an object of the present invention to provide an image forming method capable of performing the above.

[0009]

In order to achieve the above object, an image forming method according to the present invention comprises an electrostatic latent image on a latent image carrier.
Developing with a magnetic toner; and
Transferring the toner image on the latent image carrier to a transfer material,
Clear the residual toner remaining on the latent image carrier without being transferred.
The image forming method including the step of cleaning.
In the cleaning step, the magnetic toner layer carried on the surface
Magnets arranged opposite to contact the latent image carrier
Cleaning roller with a cleaning roller
Clearing contact with the latent image carrier on the downstream side of the roller
Cleaning blade having a cleaning blade.
And at least a resin as the magnetic toner.
Colored particles containing a magnetic substance and on the surface of resin particles
Containing composite fine particles to which inorganic fine particles are fixed.
Characterized by using a magnetic toner.

[0010]

In the above-described image forming method, since the inorganic fine particles are present on the surface of the composite fine particles, the composite fine particles have an appropriate resistance value and do not selectively adhere to the developing sleeve. Further, since the inorganic fine particles on the surface of the composite fine particles are hard and fine, the entire composite fine particles have an appropriate hardness and the shape has no corners, so that the developing sleeve is not rapidly worn. Furthermore, since the fluidity of the toner is improved due to the presence of the inorganic fine particles on the surface of the composite fine particles, the surface of the developing sleeve is always maintained in a clean state even when forming images many times, and a sufficient amount of triboelectric charge is applied to the toner. give.
As a result, a stable image density is always obtained, and no fogging occurs. Further, since the composite fine particles are present on the colored particles or between the colored particles, the filming of the toner constituent substance to the developing sleeve due to the shearing force applied to the toner when forming the thin layer is also prevented. Further, since the inorganic fine particles on the surface of the composite fine particles are hard and fine, the entire composite fine particles have an appropriate hardness, and since there is no corner in shape,
Cleaning performance is also improved.

[0011] Then, a cleaning roller having a magnet, a cleaning device comprising a cleaning blade Te image forming method odor using, for composite particles formed by fixing the inorganic fine particles on the surface of the resin particles,
The surface of the composite fine particles has an appropriate hardness and exhibits an appropriate polishing property. In addition, since the fixed inorganic fine particles are minute, the surface of the latent image carrier is hardly damaged. Furthermore, the specific gravity of the composite fine particles is close to that of the colored particles, and the composite fine particles are not scattered by the centrifugal force, and neither contamination in the image forming apparatus nor contamination of the image occurs. Further, the toner is uniformly dispersed in the magnetic toner layer on the cleaning roller, and the cleaning property is improved.

Hereinafter, the present invention will be described by way of specific examples. The composite fine particles used in the present invention are obtained by fixing inorganic fine particles to the surface of resin particles. The average particle diameter of the resin particles constituting the composite fine particles is preferably 0.1 to 7.0 μm from the viewpoint of improving the cleaning property and the stability of the triboelectric charging property.
In particular, 0.2 to 5.0 μm is preferable. The average particle diameter of the resin particles refers to a volume-based average particle diameter measured by a laser diffraction particle size distribution analyzer “HELOS” (manufactured by SYMPATEC) equipped with a wet disperser. However, before measurement, several 10 mg of resin particles were added to water together with a surfactant.
Disperse in 50 ml and then ultrasonic homogenizer (output 1
Pre-dispersion was performed for 1 to 10 minutes while paying attention to re-aggregation due to heat generation at 50 W).

The resin material of the resin particles is not particularly limited, and various resins are used. Specific examples include acrylic resins, styrene resins, styrene / acrylic copolymer resins, fluorine resins, silicone resins, olefin polymers, olefin copolymer resins, and the like.

The primary average particle diameter of the inorganic fine particles fixed to the surface of the resin particles is preferably 0.01 to 1 μm, particularly preferably 0.1 to 1 μm, from the viewpoint of improving the cleaning property and the fixing property.
01 to 0.5 μm is preferred. Here, the primary average particle diameter of the inorganic fine particles is a number average particle diameter measured by image analysis observed with a scanning electron microscope. Examples of the inorganic material constituting the inorganic fine particles include silicon oxide, aluminum oxide, titanium oxide, zinc oxide, zirconia, chromium oxide, cerium oxide, tungsten oxide, antimony oxide, copper oxide, tin oxide, tellurium oxide, manganese oxide, and oxide. Boron, barium titanate, aluminum titanate,
Examples include oxides such as magnesium titanate, calcium titanate, and strontium titanate; carbides such as silicon carbide, tungsten carbide, boron carbide, and titanium carbide; and nitrides such as silicon nitride, titanium nitride, and boron nitride.

The above-mentioned composite fine particles are constituted by fixing inorganic fine particles on the surface of resin particles. Here, the fixing means that the inorganic fine particles are not simply adhered to the resin particles by electrostatic force, but the inorganic fine particles are fixed. The state in which the length of the portion of the fine particles embedded in the resin particles is 5 to 95%. Such a state can be confirmed by observing the surface of the composite fine particles with a transmission electron microscope or the like.

In fixing the inorganic fine particles to the surface of the resin particles, it is preferable to first make the resin particles spherical, and then to fix the inorganic fine particles to the surface of the resin particles. This is because when the resin particles are spherical, the inorganic fine particles are uniformly fixed, and the release of the inorganic fine particles is effectively prevented. As means for spheroidizing resin particles,
A method in which resin particles are melted once by heat and then spray granulation, a method in which the hot-melted resin particles are jetted into water to form spheres, and spherical resin particles are synthesized by suspension polymerization or emulsion polymerization And the like.

Means for fixing the inorganic fine particles to the surface of the resin particles include a method of mixing the inorganic fine particles and the resin particles and then applying heat, and a so-called mechanochemical method of mechanically fixing the inorganic fine particles to the surface of the resin particles. Method or the like can be used. Specifically, the resin particles and the inorganic fine particles are mixed, and the mixture is stirred and mixed by a Henschel mixer, a V-type mixer, a turbular mixer, etc., and the inorganic fine particles are attached to the surface of the resin particles by electrostatic force. A method in which the resin particles to which the fine particles are attached are introduced into a heat treatment device such as a nitro atomizer or a spray drier, and heat is applied to soften the surface of the resin particles to fix the inorganic fine particles to the surface. After attaching the inorganic fine particles, the impact type pulverizer is modified to fix the inorganic fine particles on the surface of the resin particles using a device capable of imparting mechanical energy, for example, an ong mill, a free mill, a hybridizer, etc. And the like.

In obtaining the composite fine particles, the compounding amount of the inorganic fine particles with respect to the resin particles may be an amount capable of uniformly covering the surface of the resin particles. Specifically, although it depends on the specific gravity of the inorganic fine particles, it is usually 5 to the resin particles.
The inorganic fine particles are used in a proportion of -100% by weight, preferably 5-80% by weight. If the proportion of the inorganic fine particles is too small, the cleaning property tends to decrease, and if the proportion of the inorganic fine particles is too large, the inorganic fine particles are easily released.

The colored particles constituting the toner contain a binder resin, a magnetic substance, and other additives, and the average particle size is usually in the range of 1 to 30 μm. Examples of the resin constituting the colored particles include a polyester resin, a styrene resin, an acrylic resin, a styrene-acryl copolymer resin, and an epoxy resin. As the magnetic material constituting the colored particles, particles such as ferrite and magnetite having an average particle size of 0.1 to 2 μm are used. The addition amount of the magnetic substance is usually in the range of 20 to 70% by weight of the colored particles excluding external additives such as composite fine particles. Other additives include, for example, charge control agents such as salicylic acid derivatives, and fixability improving agents such as low molecular weight polyolefins.

From the viewpoint of improving the fluidity of the magnetic toner, the magnetic toner may be formed by adding and mixing inorganic fine particles from the outside to the mixture of the colored particles and the composite fine particles. As such inorganic fine particles, particularly, silica fine particles which have been subjected to a hydrophobic treatment with a silane coupling agent, a titanium coupling agent or the like are preferable.

The addition amount of the composite fine particles is preferably from 0.01 to 5.0% by weight, particularly preferably from 0.01 to 2.0% by weight based on the colored particles, from the viewpoint of enhancing the cleaning property and not inhibiting the triboelectric charging property.
% By weight is preferred.

Next, an image forming method for developing with a thin magnetic toner layer will be described. Developing Step A thin magnetic toner layer is formed on the toner carrier using the magnetic toner, and an electrostatic latent image on the latent image carrier is developed with the thin magnetic toner layer. The thickness of the magnetic toner layer in the developing region is preferably 2000 μm or less, more preferably 1000 μm or less, and particularly preferably about 10 to 500 μm. At the time of development, it is preferable to apply an AC bias voltage to the toner transporting carrier to cause an oscillating electric field to act on the development area. The gap Dsd between the latent image carrier and the toner transport carrier in the development area (hereinafter, also referred to as "development gap") is preferably about 50 to 2000 μm. The toner transport carrier for transporting the thin magnetic toner layer to the development area is not particularly limited, but has, for example, a plurality of magnetic poles in a cylindrical developing sleeve on which the magnetic toner layer is carried. A structure having a magnetic roll is used. The means for forming a thin magnetic toner layer on the toner carrying carrier is not particularly limited. For example, means for arranging a regulating blade with its tip approaching the surface of the toner carrying carrier, Means for elastically pressing and contacting the surface of the carrier, means for placing a cylindrical metal body in contact with the surface of the toner carrying carrier, means for disposing a thin magnetic plate on the surface of the toner carrying carrier, and the like are used. be able to. In the case where an elastic plate is used, it is preferable that the elastic plate be pressed against the toner transporting carrier so that the leading end faces upstream in the rotation direction of the toner transporting carrier. By making the magnetic toner layer carried on the toner carrying carrier a thin layer, the development gap Dsd
And the bias voltage required for forming an oscillating electric field can be reduced, so that toner scattering is reduced and the occurrence of leak discharge and the like based on the bias voltage from the surface of the developing sleeve is achieved. This has the advantage of preventing Also, by reducing the development gap Dsd, the electric field intensity formed in the development area by the electrostatic latent image formed on the latent image carrier increases, and as a result,
It is possible to satisfactorily develop even subtle changes in gradation and fine patterns.

Transfer Step The toner image on the latent image carrier obtained by development is transferred to a transfer material such as paper. In this transfer step, an electrostatic transfer method can be preferably used. Specifically, for example, a transfer device for generating a DC corona discharge is disposed so as to face the latent image carrier via the transfer material, and a DC corona discharge is caused to act on the transfer material from the back side of the transfer material. The toner carried on the surface of the body is transferred to the surface of the transfer material.

Cleaning Step The cleaning means is not particularly limited. For example, a cleaning device having a cleaning blade in contact with the surface of the latent image carrier is used. According to this cleaning device, the surface of the latent image carrier is rubbed by the cleaning blade, so that the residual toner not transferred but remaining on the latent image carrier is scraped off.
In the preceding stage of the cleaning step, it is preferable to add a charge elimination step for eliminating the charge on the surface of the latent image carrier in order to facilitate the cleaning. This static elimination step can be performed by, for example, a static eliminator that generates an AC corona discharge.

Fixing Step The transfer material on which the toner image has been transferred in the transferring step is subjected to a fixing process by a heating fixing device or a pressure fixing device or the like.
Thus, a fixed image is formed.

FIG. 1 is an explanatory view showing an example of an image forming apparatus which can be used for carrying out this image forming method.
In the figure, 1 is a latent image carrier, 2 is a charger, 3 is an exposure optical system, 4 is a developing device, 5 is a discharge lamp, 6 is a transfer electrode, 7 is a separation electrode, 8 is a discharge electrode, and 9 is a discharge electrode. Fixing device, 10 is a cleaning device, 25 is a cleaning blade, 11
Denotes a platen. This apparatus is of a type in which an exposure optical system 3 is fixedly arranged and a document table 11 is moved. The surface of the latent image carrier 1 is uniformly charged by the charger 2, and the charged surface of the latent image carrier 1 is exposed to an original by the exposure optical system 3 to correspond to the original on the latent image carrier 1. A formed electrostatic latent image is formed. This electrostatic latent image is developed by the developing device 4 to form a toner image. The toner image thus obtained is discharged by the discharge lamp 5 so as to be easily transferred, and then transferred to the transfer paper 12 by the transfer electrode 6. The transfer paper 12 is separated from the latent image carrier 1 by the separation electrode 7, undergoes a fixing process in the fixing device 9, and forms a fixed image. On the other hand, the latent image carrier 1 is
After that, the residual toner remaining on the latent image carrier 1 without being transferred by the cleaning device 10 is scraped off.

FIG. 2 shows the details of the developing device 4. In FIG. 1, reference numeral 13 denotes a developing sleeve, and reference numeral 14 denotes a magnetic roll. The developing sleeve 13 and the magnetic roll 14 constitute a toner carrier. The magnetic roll 14 has a configuration in which N poles and S poles are alternately arranged along the circumference. 15 is a thin layer forming member, 16 is a first stirring member, 17
Is a second stirring member, 18 is a toner supply container, 19 is a toner supply roller, 20 is a reservoir for developer, 21 is a bias power supply, and 22 is a development area. The first stirring member 16
The second stirring member 17 has a structure in which the stirring regions are rotated so as to overlap each other without colliding in opposite directions as indicated by arrows. In this developing device, the developer in the developer reservoir 20 is sufficiently stirred and mixed by the stirring members 16 and 17, and is transported by the developing sleeve 13 rotating in the direction of the arrow and the magnetic roll 14 rotating in the opposite direction. The developer is a developing sleeve 13
Attached to the surface.

On the surface of the developing sleeve 13, a plate-like thin layer forming member 15 made of an elastic body is pressed and held on one side close to the tip. The thickness of the magnetic toner layer conveyed to the developing area 22 is regulated by the thin layer forming member 15 to be a thin layer. The magnetic toner layer thinned by the thin layer forming member 15 opposes the electrostatic latent image formed on the latent image carrier 1 rotating in the direction of the arrow, preferably with a small gap, so to speak. The electrostatic latent image on the latent image carrier 1 is conveyed to the developing area 22 in a non-contact state, and is subjected to the action of the oscillating electric field by the bias power supply 21, in the developing area 22 by the thin magnetic toner layer. The toner is developed and a toner image is formed. The thickness of the thin magnetic toner layer formed on the developing sleeve is, for example, “Nikon Profile Projector” (manufactured by Nippon Kogaku Co., Ltd.).
The thickness of the magnetic toner layer can be determined by comparing the position of the image projected on the screen of the developing sleeve with the position of the image projected on the screen with the thin magnetic toner layer formed on the developing sleeve. .

The thin layer forming member 15 can be formed of, for example, a magnetic or non-magnetic metal, metal compound, plastic, rubber, or the like, one end of which is fixed by a fixing member. Preferably, the thickness is uniform. Specifically, the thickness is preferably from 10 to 500 μm. This thin layer forming member 15
On one side close to the leading end, the magnetic toner is elastically pressed against the developing sleeve 13 and the magnetic toner is conveyed little by little between the thin layer forming member 15 and the developing sleeve 13 so that the transport amount of the magnetic toner is regulated. You. Impurities, aggregates, and the like in the magnetic toner are removed by the thin layer forming member 15 into the developing region 22.
Therefore, the magnetic toner layer conveyed to the developing area 22 is a thin layer having a uniform and stable thickness. Further, the amount of the magnetic toner conveyed to the developing area 22 can be sufficiently controlled by changing the pressing force and the contact angle of the thin layer forming member 15 against the developing sleeve 13.

In this image forming method, since the magnetic toner layer formed on the developing sleeve 13 is made thin, the developing gap Dsd between the latent image carrier 1 and the developing sleeve 13 can be considerably reduced. Yes, the development by the so-called non-contact development method can be sufficiently performed. When the developing gap Dsd is reduced in this manner, the developing region 2
Since the electric field strength of the developing sleeve 2 becomes large, the developing sleeve 1
Even if the bias voltage applied to 3 is reduced, sufficient development can be performed, and as a result, there is an advantage that leakage of bias voltage and the like are reduced. Furthermore, since the contrast of the electrostatic latent image is increased, the resolution or image quality of the image obtained by development is generally improved.

In the cleaning device 10, a cleaning blade 25 made of an elastic material such as hard urethane rubber having a thickness of 1 to 3 mm is provided. The cleaning blade 25 has a length substantially corresponding to the width of the latent image carrier 1 (in the direction perpendicular to the plane of FIG. 1), and is moved by a blade holder (not shown).
It is held so as to be switchable between a pressure contact position and a pressure release position. Although not shown, the cleaning blade 2
A cleaning roller may be disposed in contact with the latent image carrier 1 on the upstream side of the cleaning roller 5 as needed.

Next, an image forming method in which a cleaning process is performed by a cleaning device having a cleaning roller having a magnet and a cleaning blade will be described.

FIG. 3 is an explanatory diagram of this cleaning device. The cleaning device 10 includes a cleaning blade 25 and a cleaning roller 23 having a surface provided with a magnet. 27 is a scraper, 28 is a pressure spring of the cleaning blade 25, and 26 is a toner conveying screw. The cleaning blade 25 is made of urethane rubber, and is located downstream of the cleaning roller 23.
That is, the latent image carrier 1 is disposed in contact with the latent image carrier 1 on the downstream side in the rotation direction. Cleaning roller 2
3, a magnetic toner layer 24 is carried on the surface of the latent image carrier 1 by the magnetic force of a magnet.
The cleaning roller 23 is arranged opposite to the latent image carrier 1 so as to contact the latent image carrier 1. The cleaning roller 23 is
The latent image carrier 1 may rotate in a forward or reverse direction with respect to the rotation direction.

The toner remaining on the latent image carrier 1 without being transferred is first polished by the magnetic toner layer 24, collected and collected. Next, the remaining toner is scraped off by the cleaning blade 25 and collected by the cleaning roller 23. The toner collected by the cleaning roller 23 is scraped off by a predetermined amount from the surface of the cleaning roller 23 by the scraper 27, and is conveyed to the toner conveying screw 26.

The cleaning roller 23 is manufactured by adhering a ferrite magnet or the like to the surface of aluminum or the like, or by mixing the ferrite magnet powder with a binder resin such as nylon and injection molding. Also, the cleaning roller 23
It may be a cylindrical rod itself made of a magnetic material. From the viewpoint of efficiently cleaning the residual toner on the latent image carrier 1, the magnetic force on the surface of the cleaning roller 23 is 300.
Preferably it is in the range of ~ 1000 Gauss. Magnetic force is 300
If it is less than Gauss, the cleaning effect is not sufficiently exhibited, while if it exceeds 1000 Gauss, scraping of the toner by the scraper 27 becomes difficult.

The magnetic toner used in this cleaning device is a magnetic toner containing colored particles containing at least a resin and a magnetic substance, and composite fine particles having inorganic fine particles fixed on the surface of the resin particles. Usually, the same magnetic toner as that used in the developing device 4 is used.

In this image forming method, the electrostatic latent image on the latent image carrier is developed with magnetic toner, and the toner image on the latent image carrier obtained by the development is transferred to a transfer material.
This toner image is fixed to form a fixed image. On the other hand, the residual toner remaining on the latent image carrier without being transferred is shown in FIG.
Cleaning is performed using a cleaning device such as
In the cleaning process, a brush of magnetic toner is formed on the surface of the cleaning roller, so that the presence of the composite fine particles contained in the magnetic toner provides an appropriate polishing action and improves the cleaning property.

[0038]

EXAMPLES Hereinafter, more specific examples will be described, but the present invention is not limited to these examples. In the following, “parts” means “parts by weight”.

Production Example of Composite Fine Particles The resin particles shown in Table 1 below and the inorganic fine particles shown in Table 2 are sufficiently stirred and mixed by a V-type blender containing a medium in a combination and an amount shown in Table 3 below. After the inorganic fine particles are adhered to the surface of the resin particles by electrostatic force, the mixture is charged into a “Hybridizer” (manufactured by Nara Machinery Co., Ltd.) to give an impact force to the mixture, and the inorganic fine particles adhere to the surface of the resin particles. The prepared composite fine particles were produced. Each of the obtained composite fine particles, by surface observation with an electron microscope and observation with a transmission electron microscope, shows that the inorganic fine particles adhered to the surface of the resin powder by electrostatic force are embedded and retained in the surface of the resin powder. It was found that the condition had been met.

[0040]

[Table 1]

[0041]

[Table 2]

[0042]

[Table 3]

Magnetic Toner 1 60 parts of binder resin (styrene / acrylic copolymer resin (styrene / butyl acrylate = 80/20)), 40 parts of magnetite, 3 parts of polypropylene, and charge control agent (salicylic acid derivative) 1 part, melt kneading, pulverizing after cooling,
After classification, magnetic colored particles 1 having an average particle size of 11.5 μm were obtained.
0.2% by weight of hydrophobic silica fine powder (primary average particle size = 7 nm) and 0.5% by weight of composite fine particles A were added to the magnetic colored particles 1 and mixed with a Henschel mixer to obtain a magnetic toner 1. .

Magnetic Toner 2 A magnetic toner 2 was obtained in the same manner as the magnetic toner 1 except that the composite fine particles A were changed to the composite fine particles B and the ratio was changed to 0.8% by weight.

Magnetic Toner 3 A magnetic toner 3 was obtained in the same manner as the magnetic toner 1 except that the composite fine particles A were changed to the composite fine particles C and the ratio was changed to 1.5% by weight.

Comparative Magnetic Toner 1 Comparative magnetic toner 1 was prepared in the same manner as magnetic toner 1, except that the composite fine particles A were changed to aluminum oxide fine powder (primary average particle size = 1.0 μm) and the ratio was changed to 3.0% by weight. Toner 1 was obtained.

Comparative Magnetic Toner 2 Comparative magnetic toner 1 was prepared in the same manner as in magnetic toner 1 except that the composite fine particles A were changed to polymethyl methacrylate fine particles (primary average particle size = 0.8 μm) and the ratio was changed to 0.6% by weight. Toner 2 was obtained.

Magnetic toner 4 67 parts of binder resin (polyester resin) and magnetite 30
Part, 2 parts of polypropylene, and 1 part of a charge control agent (salicylic acid derivative) were melt-kneaded, cooled, pulverized, and classified to obtain magnetic colored particles 4 having an average particle diameter of 12.0 μm. The magnetic colored particles 4 are provided with hydrophobic silica fine powder (primary average particle size = 12).
nm) and 0.4% by weight of the composite fine particles A were added, and mixed with a Henschel mixer to obtain a magnetic toner 4.

Magnetic toner 5 50 parts of binder resin (styrene / acrylic copolymer resin (styrene / butyl acrylate = 85/15)), 50 parts of magnetite, 4 parts of polypropylene, charge control agent (salicylic acid derivative) 1 part, melt kneading, pulverizing after cooling,
After classification, magnetic colored particles 5 having an average particle size of 10.0 μm were obtained.
0.6% by weight of hydrophobic silica fine powder (primary average particle size = 7 nm) and 1.0% by weight of composite fine particles A were added to the magnetic colored particles 5 and mixed with a Henschel mixer to obtain a magnetic toner 5. .

Magnetic Toner 6 A magnetic toner 6 was obtained in the same manner as the magnetic toner 4 except that the composite fine particles A were changed to the composite fine particles B and the ratio was changed to 1.0% by weight.

Magnetic Toner 7 A magnetic toner 7 was obtained in the same manner as the magnetic toner 5 except that the composite fine particles A were changed to the composite fine particles C and the ratio was changed to 0.4% by weight.

Comparative Magnetic Toner 3 In the magnetic toner 4, the composite fine particles A were changed to cerium oxide (primary average particle size = 1.5 μm), and the ratio was 2.0.
Comparative magnetic toner 3 was obtained in the same manner except that the content was changed to wt%.

Comparative Magnetic Toner 4 In the magnetic toner 5, the composite fine particles B were replaced with titanium oxide (1
(Secondary average particle size = 0.5 μm), and Comparative Magnetic Toner 4 was obtained in the same manner except that the ratio was changed to 1.0% by weight.

Comparative Magnetic Toner 5 Comparative magnetic toner 5 was prepared in the same manner as magnetic toner 5 except that composite fine particles A were changed to polymethyl methacrylate fine particles (primary average particle size = 1.5 μm) and the ratio was changed to 1.0% by weight. 5 was obtained.

Example 1 Using a magnetic toner 1, an electrostatic charge image formed on a photoreceptor is developed to form a toner image, the toner image is transferred to a transfer material, and the transferred toner image is fixed. An actual image test was performed to form a copy image by performing an image forming process including a step of cleaning the toner remaining on the photoconductor after transfer with a cleaning blade. The main conditions in the live-action test are as follows. Latent image carrier A selenium-tellurium photoconductor was used.

Developing Unit The developing unit for a one-component developer shown in FIG. 1 was used. The thin layer forming member is an elastic blade made of non-magnetic urethane rubber. Toner conveyance carrier is one in which the surface roughness R _Z subjected to blast treatment is provided with an aluminum developing sleeve 2 [mu] m. The gap (developing gap) Dsd between the developing sleeve and the photosensitive member was set to 0.25 mm, and the gap Hcut between the elastic blade and the developing sleeve was set to 0.10 mm. The thickness of the magnetic toner layer conveyed to the developing area was 150 μm. An alternating electric field (voltage: 1500 V _PP , frequency: 2 kHz) and a DC bias voltage (250 V) were applied to the development area. The surface roughness R _Z refers to a ten-point average roughness specified in JIS B0601-1982, and a measuring device used was a surface roughness tester “SE-30H” manufactured by Kosaka Laboratory. The measurement was performed using a contact-type measuring method using a stylus of a diamond needle. In this method, the movement of the stylus according to the surface roughness is detected by the contact and movement of the stylus with the surface of the object to be measured, and this is electrically amplified to determine the surface roughness.

Cleaning Apparatus An apparatus equipped with a cleaning blade was used. Environmental conditions The temperature is 25 ° C and the relative humidity is 60%. 100,000 copies.

The following items were evaluated by the actual photographing test described above. The results are shown in Tables 4 to 6 below. (1) Image density Observation of the copied image by visual observation, ○ indicates that the image density is sufficient, △ indicates that the image density is slightly low but at a practical level, and 場合 indicates that the image density is low and poses a problem in practice. Is indicated by x. (2) Fog The copy image was visually observed, and the case where there was no fog was evaluated as ○, the case where there was some fog but at a practical level was rated as Δ, and the case where there was a lot of fog and there was a problem in practice was rated as x. (3) Amount of triboelectric charge After each copy and after 100,000 copies, the developing unit is taken out, the magnetic toner particles on the surface of the developing sleeve are separated by air, and a charge amount distribution measuring device “E
It was dropped on a "Spurt Analyzer" (manufactured by Hosokawa Micron Corporation) to measure the charge amount.

(4) Abrasion State of Developing Sleeve Surface The surface roughness R _Z of the developing sleeve after the end of the actual shooting test was measured and evaluated. The surface roughness R _Z is JIS B0601-19
The ten-point average roughness specified in 82, measured using a surface roughness tester "SE-30H" (manufactured by Kosaka Laboratories) and employing a contact-type measuring method with a diamond stylus. . (5) Deposits on the surface of the developing sleeve The surface of the developing sleeve after the actual test was observed and evaluated. If an adhering substance is found, the adhering substance on the surface of the developing sleeve is scraped off with a KBr tablet, and “FT-
IR, 1720X type "(manufactured by PerkinElmer Co., Ltd.), and it was determined whether or not the attached matter was resin particles.

(6) Cleaning Property The surface of the photoreceptor immediately after being cleaned and cleaned by the cleaning blade was visually observed, and a judgment was made based on the presence or absence of a substance adhering to the surface of the photoreceptor. The case where almost no deposits were observed was rated as “O”, the case where slight deposits were observed but was at a practical level was rated as “Δ”, and the case where many deposits were observed and which had a practical problem was rated as “x”. (7) Black spots and black lines The copy image is visually observed to check for the presence of black spots and black lines. △ indicates that there was no practical problem, and × indicates that there were many black spots or black lines and had a practical problem.

(8) Causes of Black Spots or Black Lines Black Spots or Black Lines Caused by Deposits on the Photoconductor The surface of the photoconductor after being cleaned by the cleaning blade is visually observed, and the debris is generated. If so, it was confirmed whether or not a black spot and a black line had occurred in the image portion corresponding to that part. Black spots and black lines due to scratches on the photoreceptor Visually observe the surface of the photoreceptor, and if any scratches occur, determine whether black spots and black lines have occurred on the image portion corresponding to that site. confirmed. Black spots and black lines caused by scratches on the cleaning blade Observe the cleaning blade with an optical microscope. If the blade is damaged, check whether black spots and black lines have occurred on the image corresponding to the site. I checked.

Example 2 An actual photographing test was performed in the same manner as in Example 1 except that the magnetic toner 1 was changed to the magnetic toner 2, and the evaluation was performed in the same manner. The thickness of the magnetic toner layer transported to the developing area was 150 μm.

Example 3 In the same manner as in Example 1, except that the magnetic toner 1 was changed to the magnetic toner 3, the development gap Dsd was set to 0.10 mm, Hcut was set to 0.10 mm, and no alternating electric field was applied. A test was performed and evaluated in the same manner. The thickness of the magnetic toner layer transported to the developing area was 200 μm.

Comparative Example 1 An actual photographing test was performed in the same manner as in Example 1 except that the magnetic toner 1 was changed to the comparative magnetic toner 1, and evaluation was performed in the same manner. The thickness of the magnetic toner layer conveyed to the developing area was 180 μm.

Comparative Example 2 An actual photographing test was performed in the same manner as in Example 1 except that the magnetic toner 1 was changed to the comparative magnetic toner 2, and evaluation was performed in the same manner. The thickness of the magnetic toner layer transported to the developing area was 150 μm.

[0066]

[Table 4]

[0067]

[Table 5]

[0068]

[Table 6]

Example 4 Using a magnetic toner 4, a selenium photoreceptor, a developing device for a one-component developer, and a magnet having a predetermined amount of magnetic toner applied to the surface in advance were provided. A prototype of an electrophotographic copying machine having a cleaning device having a configuration shown in FIG. 3 having a cleaning roller and a cleaning blade rotating in the forward direction with respect to the rotation direction of 10 ° C. and a relative humidity at which cleaning failure easily occurs. A real image test was conducted to form a copy image up to 200,000 times under 15% environmental conditions, and the following items were evaluated. The results are as shown in Tables 7 and 8 below.

(1) Cleaning Property Evaluation was performed in the same manner as in Example 1. (2) Damage to Photoreceptor The surface of the photoreceptor was visually observed to check for damage. (3) Black spot and black line Evaluation was performed in the same manner as in Example 1. (4) Scattering of external additives The inside of the electrophotographic copying machine and the copy image were visually observed. When the scattering of the external additives was hardly observed, it was evaluated as ○. In addition, the case where the scattering of the external additive was recognized a lot and there was a problem in practice was evaluated as x. (5) Image unevenness The copy image is visually observed, and the case where the image unevenness is hardly recognized is ○, the case where the image unevenness is slightly observed but is at a practical level is Δ, and the image unevenness is often observed and there is a problem in practical use. The case was evaluated as x. (6) Image dropout A copy image is visually observed, and when the image dropout is scarcely observed, the image dropout is slightly observed but is at a practical level. The case was evaluated as x.

Examples 5 to 7 In the same manner as in Example 4, except that the magnetic toner 4 was changed to the magnetic toners 5 to 7, actual photographing tests were performed in the same manner.
evaluated.

Comparative Examples 5 to 7 Actual shooting tests were performed and evaluated in the same manner as in Example 4, except that the magnetic toner 4 was changed to Comparative Magnetic Toners 3 to 5, respectively.

[0073]

[Table 7]

[0074]

[Table 8]

Example 8 A selenium photoreceptor using the magnetic toner 1, the developing device used in Example 1, and a magnet having a predetermined amount of magnetic toner applied to the surface thereof in advance were used. A prototype of an electrophotographic copying machine including a cleaning device having a configuration shown in FIG. 3 having a cleaning roller and a cleaning blade rotating in a forward direction with respect to the rotation direction.
Developing conditions were the same as in Example 1, temperature 10 ° C, relative humidity
A live-action test was performed to form a copy image up to 200,000 times under 15% environmental conditions. The surface of the developing sleeve and the photoreceptor can be kept clean during the formation of 200,000 copy images. As a result, high density and image defects such as fog, image unevenness, image dropout, and scattering of external additives occur. There was nothing. In addition, the cleaning property was maintained well, and no black spots and black lines were generated. That is, a high-density and high-quality image was obtained over a long period of time.

[0076]

As described above in detail, according to the present invention, a stable thin magnetic toner layer can be formed, and a good image can be stably formed without a cleaning failure. Thus, in an image forming method using a cleaning device having a cleaning roller having a magnet and a cleaning blade, it is possible to stably form a good image without cleaning failure and transfer unevenness.

[Brief description of the drawings]

FIG. 1 is a schematic view of an example of an image forming apparatus that can be used in the image forming method of the present invention.

FIG. 2 is a schematic view of an example of a developing device that can be used in the image forming method of the present invention.

FIG. 3 is a schematic view of an example of a cleaning device that can be used in the image forming method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Latent image carrier 2 Charger 3 Exposure optical system 4 Developing device 5 Lamp for static elimination 6 Transfer electrode 7 Separation electrode 8 Static elimination electrode 9 Fixing device 10 Cleaning device 11 Original table 12 Transfer paper 13 Developing sleeve 14 Magnetic roll 15 Thin layer formation Member 16 First stirring member 17 Second stirring member 18 Toner supply container 19 Toner supply roller 20 Developer pool 21 Bias power supply 22 Developing area 23 Cleaning roller 24 Magnetic toner layer 25 Cleaning blade 26 Toner transport screw 27 Scraper 28 Crimping spring

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-64-91143 (JP, A) JP-A-2-298954 (JP, A) JP-A-2-137715 (JP, A) (58) Investigation Field (Int.Cl. ⁷ , DB name) G03G 9/08 G03G 21/00

Claims (1)

(57) [Claims] An electrostatic latent image on a latent image carrier is converted into a magnetic toner.
Developing step and on the latent image carrier obtained by development
Transferring the toner image to the transfer material
A process for cleaning the residual toner remaining on the image carrier
In the image forming method, the cleaning step includes the step of:
The magnet is disposed opposite to the layer so that the layer contacts the latent image carrier.
Cleaning roller with net and this cleaning
In contact with the latent image carrier on the downstream side of the roller
Cleaning device having a cleaning blade
The magnetic toner contains at least a resin and a magnetic material.
Colored particles and inorganic fine particles on the surface of the resin particles
Magnetic toner containing composite fine particles fixed thereto
An image forming method characterized by using: