JPH11282240A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an image forming device constituted so that an excellent image can be formed by suppressing the deterioration of non-magnetic one- component developer (toner, for example) and uniformly and properly electrify ing the non-magnetic one-component developer. SOLUTION: This laser printer is constituted so that the toner T is triboelectrified and carried to the surface of a photoreceptor drum 23 by rotating a developing roller 27 and a supply roller 28 at a position where they are mutually separated. That means, since the rollers 27 and 28 are not brought into contact with each other, the deterioration of the toner T can be excellently suppressed. Then, titanium oxide and silica are mixed and added to the toner T as additive. However, since the titanium oxide is provided with almost mediate electrifying property, the toner T is uniformly and properly electrified. Besides, the flowability of the toner T is enhanced by the silica.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for forming an image by transferring a developer to a recording medium, and more particularly, to an image forming apparatus for forming an image with a charged non-magnetic one-component developer. .

[0002]

2. Description of the Related Art Conventionally, an electrostatic latent image carrier such as a photosensitive drum on which an electrostatic latent image is formed on a surface thereof, and a developer such as toner are conveyed to the surface of the electrostatic latent image carrier. 2. Description of the Related Art There is known an image forming apparatus including a developing unit for developing the electrostatic latent image and a supply unit for supplying a developer to the developing unit. In this type of image forming apparatus, a developer is conveyed to the surface of the electrostatic latent image carrier by a supply unit and a developing unit, and the electrostatic latent image is developed by the developer. Subsequently, the developer is coated. An image is formed by transferring the image to a recording medium.

[0003] As the developer, a two-component developer containing a toner and a carrier and a one-component developer containing no carrier are known. In recent years, a one-component developer has been frequently used in place of a two-component developer because of easy maintenance and miniaturization of the image forming apparatus. In the case of a one-component developer, when a magnetic force is used to move the toner, the toner contains a magnetic material.
However, since the magnetic material is opaque, it is appropriate to use a non-magnetic developer especially in color development. Therefore, in recent years, a non-magnetic one-component developer has been generally used in a so-called electrophotographic image forming apparatus that forms an image by transferring a developer such as a toner onto a recording medium.

A non-magnetic one-component developer is positively or negatively charged by friction charging or the like, and develops the electrostatic latent image using electrostatic attraction. Further, as a configuration for transporting this kind of non-magnetic one-component developer to the surface of the electrostatic latent image carrier, a supply roller as a supply unit is configured by an elastic material such as a conductive sponge, and A configuration is known in which both rollers are simultaneously rotated while being in contact with a developing roller. When such a configuration is adopted, the non-magnetic one-component developer is rubbed between the developing roller and the supply roller, and as a result, the non-magnetic one-component developer is frictionally charged and conveyed by the developing roller. become able to.

[0005]

However, when the non-magnetic one-component developer is conveyed to the surface of the electrostatic latent image carrier by simultaneously rotating the two rollers while bringing the supply roller into contact with the developing roller, There is a possibility that the non-magnetic one-component developer sandwiched between the developing roller and the developing roller may be deteriorated. For example, the external additive may be embedded in the toner base particles.

In view of this, a configuration is conceivable in which a supply roller is constituted by a cylindrical member that rotates at a position separated from the developing roller, and the developing roller and the supply roller are simultaneously rotated. In this case, since the developing roller and the supply roller do not contact each other, the pressure applied to the non-magnetic one-component developer decreases,
The deterioration can be suppressed well.

[0007] In this case, however, the scraping ability of the non-magnetic one-component developer also decreases with the decrease in the pressure. That is, the non-magnetic one-component developer that has not adhered to the development despite being attached to the surface of the developing roller is not scraped off with the supply roller, and most of the developer remains on the surface of the developing roller. As described above, when insufficient scraping occurs, a sleeve ghost is likely to occur. The sleeve ghost refers to the Q / M (charge amount per unit mass) and M / A (mass per unit area) of the non-magnetic one-component developer on the developing roller after black solid printing, and white solid. Due to the remarkable difference in Q / M and M / A of the non-magnetic one-component developer on the developing roller after printing,
This is a phenomenon in which there is a difference in the density of the halftone under the black solid and under the white solid.

[0008] After printing a solid white, that is, when the non-magnetic one-component developer on the developing roller is hardly provided for development, if the supply roller does not scrape the same toner, the same toner is supplied to the developing again. Will be. At this time, if the charging property of the non-magnetic one-component developer is poor, the Q / M of the non-magnetic one-component developer that makes two turns on the developing roller becomes too high, or is newly supplied by the supply roller. Due to the non-magnetic one-component developer, the M / A on the developing roller becomes too high. If the Q / M after printing the solid white is too high than the Q / M after printing the solid black, the halftone image density becomes lower after the solid white and becomes higher after the solid black. . This state is called a sleeve positive ghost. If the M / A after printing the solid white is too high than the M / A after printing the solid black, the halftone image density becomes higher after the solid white and becomes darker after the solid black. Lower. This state is called a sleeve negative ghost.

Particularly, silica is an excellent external additive for improving the fluidity of the toner, but is strongly negatively charged. For this reason, when a positively chargeable one-component toner is used as the non-magnetic one-component developer, the rising of the charge of the non-magnetic one-component developer is delayed by external addition of silica. Non-magnetic 1
Since the component developer is mainly conveyed to the developing roller by the image force of the charge, the delay in the rise of the charge of the non-magnetic one-component developer is sufficient if the M / A on the developing roller makes one rotation. It appears as a phenomenon that it cannot be reached. Therefore, by printing solid white, the M / A on the developing roller rises as the non-magnetic one-component developer goes around the developing roller many times, and as a result, the above-mentioned sleeve negative ghost is reduced. Will happen.

When a negatively chargeable one-component toner is used as the non-magnetic one-component developer, the charge of the non-magnetic one-component developer tends to be too high by external addition of silica. Accordingly, the Q / M after white solid printing becomes too high. As a result, although not as remarkable as the sleeve negative ghost in the positively charged toner described above, a sleeve positive ghost occurs.

[0011] It has also been proposed to reduce the negative chargeability of the silica by a technique such as oil treatment and to make the silica more positively chargeable. Charge up occurs,
The above problem could not be sufficiently solved.

Accordingly, the present invention provides an image forming apparatus which can suppress deterioration of a non-magnetic one-component developer and uniformly and appropriately charge the non-magnetic one-component developer to form a good image. Made for the purpose of providing.

[0013]

Means for Solving the Problems and Effects of the Invention In order to achieve the above object, the invention according to claim 1 provides an electrostatic latent image carrier having a surface on which an electrostatic latent image is formed; Developing means for conveying the charged non-magnetic one-component developer to the surface of the electrostatic latent image carrier and developing the electrostatic latent image; and supplying means for supplying the non-magnetic one-component developer to the developing means. Wherein the non-magnetic one-component developer obtained by developing the electrostatic latent image is transferred to a recording medium to form an image.
The supply means rotates at a position separated from the developing means to supply the non-magnetic one-component developer to the developing means, and the closest distance to the developing means is 2 mm.
In addition, at least one of the external additives added to the non-magnetic one-component developer is a titanium oxide that has been subjected to a hydrophobic treatment.

According to the present invention, the supply unit rotates at a position separated from the developing unit to supply the non-magnetic one-component developer to the developing unit. Therefore, as described above, the deterioration of the non-magnetic one-component developer can be favorably suppressed. Further, in the present invention, since the closest distance between the supply means and the developing means is about 2 mm or less, the conveying force of the non-magnetic one-component developer is relatively secured.

Further, in the present invention, at least one of the external additives added to the non-magnetic one-component developer is a titanium oxide subjected to a hydrophobic treatment. Titanium oxide has a substantially neutral charging property, and uniformly and appropriately charges a non-magnetic one-component developer. Therefore, in the present invention, due to insufficient scraping,
The occurrence of sleeve negative ghost in a positively charged non-magnetic one-component developer and the occurrence of sleeve positive ghost in a negatively charged non-magnetic one-component developer can be favorably suppressed. The titanium oxide as an external additive has been subjected to a hydrophobic treatment. For this reason, it is possible to prevent the titanium oxide from absorbing water and adhering to other objects, thereby further improving the fluidity of the non-magnetic one-component developer. Therefore, the above-mentioned conveying force can be more favorably secured, and a better image can be formed. Therefore,
According to the present invention, the effect of suppressing deterioration of the non-magnetic one-component developer and forming a good image by uniformly and appropriately charging the non-magnetic one-component developer is obtained.

Note that the closest distance between the supply means and the developing means is such that if the distance between the supply means and the developing means is only one layer of the non-magnetic one-component developer, the distance between the non-magnetic one-component developer and the non-magnetic one-component developer is smaller. Deterioration can be sufficiently suppressed. In order to better prevent the deterioration of the non-magnetic one-component developer and to further ensure the above-described conveying force and scraping ability, it is more preferable that the closest distance be 0.1 to 0.5 mm.

According to a second aspect of the present invention, in addition to the first aspect, the amount of the external additive added to the non-magnetic one-component developer is about 0.5% by weight or more of the titanium oxide. , Wherein the amount of other external additives is about 0.8% by weight or less. The effect of adding titanium oxide to a non-magnetic one-component developer as an external additive is as follows. The amount of titanium oxide added is about 0.5% by weight or more, and the amount of other external additives is about
It becomes more remarkable when the content is not more than% by weight. That is, with such an addition amount, the effect of titanium oxide is sufficiently ensured, and the effect is not offset by other external additives. In the present invention, since the addition amount of titanium oxide and other external additives is set in the above range, the above-mentioned effect by titanium oxide appears more remarkably, and the non-magnetic one-component developer can be charged more uniformly and appropriately. it can. Therefore, in the present invention, in addition to the effect of the first aspect, an effect is obtained that the non-magnetic one-component developer can be more uniformly and appropriately charged to form a better image.

According to a third aspect of the present invention, in addition to the constitution of the second aspect, the other external additive is silica, and the addition amount of the titanium oxide is about 0.5 to 1.3% by weight. Is about 0.4 to 0.8% by weight. Silica is an excellent external additive that improves the fluidity of a non-magnetic one-component developer, as described above. Further, silica is more effective when added to the non-magnetic one-component developer in an amount of about 0.4% by weight or more, and improves the fluidity. Further, it is possible to favorably prevent the occurrence of black solid blurring or the like due to the shortage of the conveying force. Further, in the present invention, by adding titanium oxide as an external additive, it is possible to offset the influence of negatively charged silica.

As described above, in order to ensure the effect of improving the fluidity by the addition of silica, and to favorably offset the influence of the negative charging of silica, the amount of silica added is about 0.4 to 0.8% by weight. About 0.5 to 1.3% by weight of titanium oxide
It is desirable to add. That is, if the added amount of silica is larger than the above value or the added amount of titanium oxide is smaller than the above value, the influence due to the negative charging of the silica appears, and the added amount of silica is smaller than the above value or the titanium oxide is added. If the addition amount is larger than the above value, the effect of improving the fluidity by adding silica is not sufficiently exhibited.

In the present invention, since the addition amounts of silica and titanium oxide are set within the above ranges, the non-magnetic one-component developer is uniformly and appropriately charged by the titanium oxide, and its fluidity is sufficiently ensured by the silica. be able to. Therefore, in the present invention, in addition to the effect of the invention described in claim 2, there is an effect that the fluidity of the non-magnetic one-component developer can be further improved and a better image can be formed. If silica is also subjected to a hydrophobic treatment, it prevents the silica from absorbing moisture and adhering to other objects, and the non-magnetic one
The fluidity of the component developer can be further improved. Therefore, in this case, a better image can be formed.

According to a fourth aspect of the present invention, in addition to the configuration according to any one of the first to third aspects, the supply means has a cylindrical shape and rotates around its central axis. In the present invention, since the supply means has a cylindrical shape, the non-magnetic one-component developer adheres to the surface of the supply means by the image force. If the supply means is rotated around the central axis in this state, the above-described conveying force can be satisfactorily secured even when the supply means and the developing means are separated from each other. Therefore,
In the present invention, in addition to the effects of the invention according to any one of claims 1 to 3, there is an effect that the non-magnetic one-component developer can be transported more favorably to form a better image. . If the supply means is made of a conductive material such as a metal, the above-mentioned image power is further enhanced, and an even better image can be formed.

According to a fifth aspect of the present invention, in addition to the configuration of any one of the first to third aspects, the supply means has a prismatic shape having a polygonal cross section, and rotates about a central axis thereof. And In the present invention, since the supply means has a prismatic shape having a polygonal cross section, by rotating the supply means around the central axis, the non-magnetic one-component developer is pushed in by the corners of the polygon. Can be transported. Therefore, in the present invention, in addition to the effects of the invention according to any one of claims 1 to 3, an effect that a better image can be formed by transporting the non-magnetic one-component developer more favorably. Occurs. In the case where the supply means has a pentagonal or hexagonal cross section, the pushing force can be satisfactorily secured while suppressing the fluctuation of the transport amount of the non-magnetic one-component developer. Therefore, in this case, an even better image can be formed.

[0023]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of main components of a laser printer as an image forming apparatus to which the present invention is applied, and FIG. 2 is a schematic sectional side view of the laser printer.

As shown in FIG. 1, the main body case 1 made of a synthetic resin in the laser printer is provided with a main frame 1a.
And a main cover 1b that covers the outer surface of the main frame 1a on four sides (front and rear and left and right sides). The main frame 1a and the main cover 1b are integrally formed by injection molding or the like.

A scanner unit 2 as an exposure unit, a process cartridge 3 as an image forming unit, a fixing unit 4 as a fixing unit, and a sheet feeding unit 5 are mounted on the main frame 1a from the top. The drive system unit 6 including the drive motor and the gear train includes:
It is inserted and fixed from below the main body case 1 into the storage recess 1d between the left inner surface of the main cover 1b in FIG. 1 and the left side of the main frame 1a adjacent thereto. Furthermore,
A top cover 7 as a synthetic resin body cover for covering the upper surfaces of the main frame 1a and the main cover body 1b has a hole 7a through which an operation panel 1c projecting upward to the right side of the main frame 1a penetrates. A hole 7b for penetrating the base of the paper unit 5 is provided. The base of the paper discharge tray 8 is attached to brackets 9 (only one is shown in FIG. 1) protruding from the left and right sides of the front end of the top cover 7 so as to be vertically swingable. 8 can be folded and covered on the upper surface side of the top cover 7.

In the feeder unit case 5a of the paper feed unit 5, recording papers P as recording media are set in a stacked state. As shown in FIG. 2, the leading end side of the recording paper P is pressed toward the paper feed roller 11 by a support plate 10 urged by a spring 10a in the feeder case 5a. Therefore, the recording paper P can be separated one by one and sent to the pair of upper and lower registration rollers 13 and 14 by the paper feed roller 11 and the separation pad 12 which are rotated by the power transmitted from the drive system unit 6. .

The process cartridge 3 forms an image with the toner T (FIG. 3) on the surface of the separated recording paper P fed by the registration rollers 13 and 14. Further, the fixing unit 4 heats the recording paper P on which the image of the toner T is formed by sandwiching the recording paper P between the heating roller 15 and the pressing roller 16 to fix the toner image on the recording paper P. A paper discharge unit including a paper discharge roller 17 and a pinch roller 18 disposed downstream in the case of the fixing unit 4 feeds the recording paper P on which the toner image has been fixed to a paper discharge tray 8.
To be discharged. The section from the paper feed roller 11 to the paper discharge section is a recording medium transport route. The paper feeding unit 5 is provided with a manual insertion opening 5b that opens diagonally upward, and a recording paper different from the recording paper P in the feeder unit case 5a is inserted into the recording medium transport route for printing. Have been able to.

An upper support plate 2a of the scanner unit 2 is provided with a bottom plate of the main frame 1a at a position below the process cartridge 3, which is disposed substantially at the center of the main frame 1a having a box shape with an open top in the main body case 1 in a plan view. It is fixed to a stay part integrally formed on the upper surface side of the part with screws or the like. And a scanner unit 2 as an exposure unit
A laser emitting unit (not shown), a polygon mirror 20, a lens 21,
The reflection mirror 22 and the like are arranged. The upper support plate 2a is provided with a glass plate 24 that covers a horizontally long scanner hole formed so as to extend along the axis of the photosensitive drum 23 as an electrostatic latent image carrier. The laser beam L emitted from the laser emitting section is reflected by the polygon mirror 20 and the reflecting mirror 2.
2. Irradiation is performed on the outer peripheral surface of the photosensitive drum 23 in the process cartridge 3 via the lens 21, the glass plate 24, and the like.

As shown in FIGS. 2 and 3, the process cartridge 3 includes a photosensitive drum 23 and a transfer roller 25 in contact with the upper surface thereof, and a developing means disposed upstream of the photosensitive drum 23 in the sheet feeding direction. Developing roller 27,
And a developing device having a supply roller 28 as a supply means disposed further upstream thereof, a toner cartridge 29 which is detachably mountable to a developer supply section, that is, a process cartridge 3 disposed further upstream thereof, and a photosensitive device. Cleaning roller 3 arranged downstream of drum 23
It consists of 0 mag. The process cartridge 3 is formed into a cartridge by incorporating these components into a case 34 made of synthetic resin.
a is detachably attached to a. Note that the photosensitive drum 23, the developing roller 27, and the supply roller 28 all rotate clockwise in FIG.

Process cartridge 3 and fixing unit 4
A charge removing lamp 30a for removing charges from the photosensitive drum 23 is provided between the discharge lamps 30a and 30b. Further, a charger 26 is provided below the photosensitive drum 23. The charger 26 is a well-known scorotron type charger for positive charging including a discharge wire 26a made of tungsten or the like and a grid electrode 26b, and is provided integrally on the upper support plate 2a of the scanner unit 2.

The outer peripheral surface of the photosensitive drum 23 has a charger 26
The electrostatic latent image is formed by scanning the laser beam L modulated according to the image information by the scanner unit 2 on the photosensitive layer charged by (1). That is, the scanner unit 2 corresponds to an electrostatic latent image forming unit. As shown in the enlarged view of FIG. 3, the toner T as the developer stored in the toner cartridge 29 is agitated by the agitator 31 and released, and then is supplied to the outer periphery of the developing roller 27 via the supply roller 28. The thickness of the layer on the outer peripheral surface of the developing roller 27 is regulated by the layer thickness regulating blade 32. The electrostatic latent image on the photosensitive drum 23 is visualized (developed) by the attachment of the toner T from the developing roller 27. The configuration of the toner T, the developing mechanism, and the like will be described later in detail.

An image (toner image) formed on the photosensitive drum 23 by the toner T is formed on a recording sheet passing between the transfer roller 25 to which a transfer bias having a potential opposite to the potential of the photosensitive drum 23 is applied and the photosensitive drum 23. The toner image is transferred to P to form a toner image. Then, after the toner T remaining on the photosensitive drum 23 is temporarily collected by the cleaning roller 30, the toner T is returned to the photosensitive drum 23 at a predetermined timing, and is collected in the process cartridge 3 by the developing roller 27.

The upper support plate 2a of the scanner unit 2
(FIG. 2), a toner sensor 33 projecting upward is provided, and the toner sensor 33 including a pair of a light emitting unit and a light receiving unit is attached to the toner cartridge 2 of the process cartridge 3.
9, the presence or absence of the toner T in the toner cartridge 29 can be detected.

Returning to FIG. 2, a storage section 36 for storing a cooling fan 35 and a storage section 36 for recording paper P are provided on the lower surface side of the continuous portion between the front section of the main frame 1a and the front section of the main cover 1b. A ventilation duct 37 extending in the left-right direction perpendicular to the passing direction is formed to communicate with each other. And ventilation duct 3
7, the upper plate 37a is formed in a downward V-shaped cross section, and the upper plate 37a is located between the process cartridge 3 and the fixing unit 4 so that the heat generated from the heating roller 15 in the fixing unit 4 causes the process. It shuts off so that it is not directly transmitted to the cartridge 3 side.

The cooling air generated by the cooling fan 35 passes through the inside of the ventilation duct 37 and along the lower surface of one side of the main frame 1a to cool the power supply unit 39 and the drive motor of the drive system unit 6, while cooling the drive motor. The cooling air is blown out from a plurality of slit holes opened on the side of the process cartridge 3 in the face plate portion 37 a, and the cooling air passes through the space between the process cartridge 3 and the fixing unit 4 and rises.
The air is exhausted out of the apparatus through exhaust holes 40 (FIG. 1) formed in a plurality of holes.

Next, the toner image developing mechanism will be described. First, the toner T accommodated in the toner cartridge 29 is prepared by adding a well-known colorant such as carbon black and a known colorant such as carbon black or the like to styrene-acrylic resin formed in a spherical shape by suspension polymerization. 9μ average particle size after adding charge control agent
m of toner base particles. Such a toner T
Is known as a positively chargeable non-magnetic one-component developer. The toner T is configured by adding silica and titanium oxide as external additives to the surface of the toner base particles. Further, silica is subjected to a hydrophobic treatment with hexamethyldisilazane, and titanium oxide is subjected to a hydrophobic treatment with aluminum and silicone oil. Titanium oxide as a large external additive has an average particle size of 40 nm, and silica as a small external additive has an average particle size of 10 nm.

The supply roller 28 is made of a metal such as SUS or nickel-plated iron and has a smooth cylindrical surface, and the distance d from the developing roller 27 is constant at 0.5 mm. Further, the developing roller 27 is formed in a cylindrical shape using silicon rubber as a base material, and further includes a fine particle of carbon, and a coat layer of a resin or rubber material containing fluorine on the surface.

For this reason, when the supply roller 28 and the developing roller 27 rotate in the above direction at positions separated from each other, and the toner T rubs between the two, the toner T is positively triboelectrically charged. The developing roller 27 has a cylindrical shape with a smooth surface, and the positively charged toner T adheres to the surface of the developing roller 27 by a mirror image force. Similarly, the supply roller 28 also has a smooth cylindrical surface made of metal, so that the toner T adheres to the surface of the supply roller 28 by a mirror image force.

Therefore, the supply roller 28 and the developing roller 2
7, the toner T can be easily and satisfactorily charged positively by friction and transported to the surface of the photosensitive drum 23. Further, the toner T adhered to the surface of the developing roller 27
At the same time, the excess toner T is scraped off by the layer pressure regulating blade 32, and at the same time, the charge of the toner T remaining on the surface of the developing roller 27 is further increased and conveyed to the surface of the photosensitive drum 23. The base of the developing roller 27 does not necessarily have to be made of silicone rubber, but may be made of, for example, urethane rubber.

The photosensitive drum 23 is made of polycarbonate or the like. For example, a photoconductive layer in which a photoconductive resin is dispersed in polycarbonate is formed on the outer peripheral portion of a grounded aluminum cylindrical sleeve. . Therefore, at the opposing portion between the developing roller 27 and the photosensitive drum 23, the positively charged toner T is applied to the positive latent (positively charged) electrostatic latent image formed on the photosensitive drum 23 by the reversal developing method. It can be developed. Then, the toner image thus developed is transferred to the transfer roller 25 as described above.
The desired image can be formed on the recording paper P by transferring the image to the recording paper P at a position facing the recording paper P.

In the laser printer thus configured, the developing roller 27 and the supply roller 28 rotate at positions separated from each other, thereby frictionally charging the toner T and transporting the toner T to the surface of the photosensitive drum 23. . That is, since the developing roller 27 and the supply roller 28 are not in contact with each other, the deterioration of the toner T can be favorably suppressed. In addition, the toner T is a suspension polymerization toner having a very spherical shape. Further, the hydrophobically treated silica having an average particle diameter of 10 nm and the titanium oxide which has been subjected to a hydrophobic treatment having an average particle diameter of 40 nm are mixed and externally added. It is added as an agent. For this reason,
The toner T has extremely excellent fluidity. Furthermore, the distance d between the developing roller 27 and the supply roller 28 is relatively small (0.5 mm) (wider than one layer of the toner T).
8 has the above-mentioned column shape. For this reason, even with the configuration of the laser printer itself, the conveyance force of the toner T is extremely well secured. Therefore, in the present laser printer, it is possible to suppress the deterioration of the toner T and to convey the toner T satisfactorily and frictionally charge the toner T, thereby forming an extremely good image.

The suspension polymerization toner is known to have a high transfer efficiency and to form an extremely high-quality image, but to have a low mechanical strength. Further, when the average particle size is 3
An external additive of 0 nm or less enhances the fluidity of the non-magnetic one-component developer to enable extremely high-quality image formation, but is known to be easily embedded in toner base particles when pressure is applied. Have been. On the other hand, in the present laser printer, as described above, the developing roller 27 and the supply roller 2
By rotating at positions separated from each other, breakage of toner T and embedding of external additives can be favorably suppressed. For this reason, even when the above-mentioned suspension polymerization toner is used as the toner T, the toner T exhibits sufficient durability, and even if an external additive (silica) having an average particle diameter of 30 nm or less is added, Embedding can be suppressed well.

Further, since excellent external additives such as silica and titanium oxide are added to the toner T in a mixture of those having a large average particle size and those having a small average particle size, a small external additive (silica) is used. Can be more favorably suppressed. That is, a large external additive having an average particle diameter of 30 nm or more prevents the other toner base particles 95 from directly contacting the small external additive 93 like the external additive 91 illustrated in FIG. The embedding of the external additive 93 in the toner base particles 95 is suppressed. Thus, in this laser printer,
Due to the close synergistic effect between the characteristics of the toner T, which is made of a suspension polymerized toner and to which the above-mentioned external additive is added, and the above-mentioned structure of the laser printer itself, the fluidity of the toner T, and consequently the above-mentioned conveying force, is improved. It is possible to stably form an extremely high-quality image by ensuring extremely good quality.

Further, titanium oxide as an external additive has a substantially neutral charging property, and charges the toner T uniformly and appropriately. For this reason, in the present invention, the occurrence of sleeve negative ghost due to insufficient scraping can be favorably suppressed. Next, the amounts of silica and titanium oxide added as external additives were variously changed, and an appropriate range thereof was estimated. Table 1 shows the experimental results.

[0045]

[Table 1]

As shown in Table 1, in toner G to which only 0.3% by weight of titanium oxide was added and in toner F to which 1.0% by weight of negatively chargeable silica was added, the negatively chargeable silica was used. As a result, the rise of toner charge was delayed, and the M / A on the developing roller was higher in solid white printing than in solid black printing, resulting in sleeve negative ghost. Further, toner H containing only 0.5% by weight of titanium oxide and toner E containing 0.8% by weight of silica were added.
However, a slight sleeve negative ghost occurred. on the other hand,
Toners A and B containing only 0.2% by weight or less of silica having a high fluidity improving effect (0% by weight and 0.2% by weight, respectively)
% By weight), black solid blurring due to insufficient fluidity of the toner occurs, and the toner L containing 1.3% by weight of titanium oxide is added.
However, black solid fading slightly occurred due to insufficient fluidity.

On the other hand, the toners C, D, I, J and K containing 0.4 to 0.6% by weight of silica and 0.7 to 1.1% by weight of titanium oxide are all good. Printing results were obtained. According to the above experimental results, about 0.4 to 0.8% by weight of silica (preferably 0.4 to 0.6%) was used as an external additive.
% By weight) and about 0.5 to 1.3% by weight (preferably 0.7 to 1.1% by weight) of titanium oxide.
It was found that a very good image could be formed. This is because, by setting the amounts of silica and titanium oxide added to the above values, the effect of the silica negatively charged is well offset by the titanium oxide while ensuring the fluidity improving effect of the silica addition, This is considered to be because the effect of titanium oxide which makes uniform and appropriate can be well expressed.

The distance d between the developing roller 27 and the supply roller 28 can be set to various values as long as it is about 2 mm or less. However, if the distance d is more than one layer of the toner, the deterioration can be sufficiently suppressed. In order to properly prevent the toner T from deteriorating and to ensure the above-mentioned conveyance force, it is preferable that the distance d is 0.1 to 0.5 mm. Further, in each of the toners A to L, the effect of titanium oxide for uniformly and appropriately charging the toner was exhibited to some extent. That is, even when any of the toners A to L is used, the present laser printer can suppress deterioration of the toner and uniformly and appropriately charge the toner as compared with the conventional laser printer to form a good image. Was.

FIG. 4 is an enlarged view showing the structure of a process cartridge 3 according to another embodiment. In the process cartridge 3 of the laser printer illustrated in FIG. 4, a supply roller 128 formed of a regular hexagonal prism made of a synthetic resin such as ABS is used instead of the supply roller 28. In this laser printer, the closest distance d between the supply roller 128 and the developing roller 27 was 0.5 mm. Even in the laser printer configured as described above, since the developing roller 27 and the supply roller 128 rotate at positions separated from each other, the deterioration of the toner T can be prevented well. Further, since the supply roller 128 has a closest distance to the developing roller 27 of less than 2 mm and has a prismatic shape, the toner T can be conveyed in such a manner that the toner T is pushed in by a hexagonal corner. In addition, the toner T has excellent fluidity as described above. For this reason, the conveying force and the frictional force applied to the toner T are very well secured.

As described above, silica and titanium oxide are added to the toner T as external additives, and the same operations and effects as those of the above-described embodiment are produced. Also, the appropriate addition amounts of silica and titanium oxide fall within the substantially same range as in the above embodiment. Note that the supply roller 128 may be formed in a prismatic shape having another polygonal cross section. However, in the case of a triangular prism or a square prism, a significant change occurs in the transport amount of the toner T. Further, in the case of a heptagon or more, the pushing force is reduced. Therefore, it is desirable that the supply roller 128 is configured as a pentagonal or hexagonal prism. Further, in the case of constituting a heptagon prism or more, it is desirable to constitute it from a conductive substance such as a metal so that the mirror image works well.

It should be noted that the present invention is not limited to the above-described embodiment, and can be implemented in various forms without departing from the gist of the present invention. For example, in the above embodiment, the average particle size of the toner base particles is 9 μm, but may be changed in the range of 6 μm to 10 μm. Further, in the above embodiment, the average particle diameter of silica and titanium oxide,
The average particle size of silica was set to 10 nm and 40 nm, respectively.
Within the above range, even if various changes are made, the same operation / effect and experimental results can be obtained. Further, as an external additive, in addition to the above,
Various external additives such as alumina and zinc oxide can be used, and three or more types of external additives including titanium oxide may be added.

Further, in the present invention, the layer pressure regulating blade 32 is not formed by bending a SUS leaf spring as in the embodiment, but by using a leaf spring provided with a soft elastic material such as silicone rubber. The present invention can be similarly applied to an image forming apparatus. Further, the present invention is similarly applied to an image forming apparatus using a non-magnetic one-component developer other than the suspension polymerization toner, for example, an image forming apparatus using another polymerization toner obtained by emulsion polymerization or the like. can do. Even when the toner T has such a configuration, relatively good fluidity can be obtained, and similar effects can be obtained although the toner T is slightly inferior. Further, the present invention is not limited to a laser printer, but can be similarly applied to an apparatus for forming an image by an electrophotographic method using a non-magnetic one-component developer, such as a facsimile and a copying machine.

[Brief description of the drawings]

FIG. 1 is a perspective view of main components of a laser printer according to an embodiment.

FIG. 2 is a schematic side sectional view of the laser printer.

FIG. 3 is an enlarged view illustrating a configuration of the process cartridge.

FIG. 4 is an enlarged view illustrating a configuration of a process cartridge according to another embodiment.

FIG. 5 is an explanatory diagram showing the effect of mixing and adding large and small external additives.

[Explanation of symbols]

2. Scanner unit 3. Process cartridge
4: fixing unit 5: paper feed unit 6: drive system unit 23
… Photosensitive drum 26… charger 27… developing roller 2
8, 128 supply roller 29 toner cartridge P recording paper T
toner

Claims (5)

[Claims] An electrostatic latent image carrier having an electrostatic latent image formed on a surface thereof; and a non-magnetic one-component developer charged on the surface of the electrostatic latent image carrier. Developing means for developing the latent image; and supplying means for supplying the non-magnetic one-component developer to the developing means. The non-magnetic one-component developer having developed the electrostatic latent image is provided on a recording medium. An image forming apparatus for forming an image by transferring the non-magnetic one-component developer to the developing unit by rotating at a position separated from the developing unit; 2mm closest to
An image forming apparatus according to the above, wherein at least one of the external additives added to the non-magnetic one-component developer is titanium oxide subjected to a hydrophobic treatment. 2. The amount of the external additive added to the non-magnetic one-component developer is about 0.5% by weight or more of the titanium oxide,
2. The image forming apparatus according to claim 1, wherein the amount of other external additives is about 0.8% by weight or less. 3. The method according to claim 1, wherein the other external additive is silica, and the addition amount of the titanium oxide is about 0.5 to 1.3% by weight, and the addition amount of the silica is about 0.4 to 0.8% by weight. 3. The image forming apparatus according to claim 2, wherein: 4. The image forming apparatus according to claim 1, wherein said supply means has a cylindrical shape, and rotates around a central axis thereof. 5. The image forming apparatus according to claim 1, wherein the supply unit has a prism shape having a polygonal cross section, and rotates around a central axis thereof.