JP4230325B2 - Non-magnetic one-component developing device and image forming apparatus - Google Patents

Description

  The present invention relates to a non-magnetic one-component developing device used for image formation by an electrophotographic process such as a copying machine, a facsimile machine, and a printer, and to an image forming apparatus using the same.

In an image forming apparatus that forms a latent image on an image carrier (hereinafter referred to as a photoreceptor) and visualizes the latent image with a developer, a one-component developer from the viewpoint of downsizing and cost reduction of the developing device A developing device using is advantageous. Particularly for colorization, it is advantageous to use a non-magnetic one-component developer because of its high transparency.
2. Description of the Related Art Conventionally, as a developing device using a one-component developer (hereinafter referred to as toner), a cylindrical developer carrier made of metal that carries a toner on its surface and transports it along a predetermined circulation path including a development region. (Hereinafter referred to as a developing roller), a storing means for storing toner, a toner supply member that contacts the developing roller and supplies the toner stored in the developer storing means to the developing roller, and a developing roller that has passed through the supplying means It is known that the above toner is made into a uniform thin layer with a blade and used for development. The surface of the developing roller has been regarded as an essential technique for providing fine irregularities so that the toner can be uniformly and uniformly conveyed on the outer peripheral surface of the developing roller. At this time, as a method of giving fine irregularities to the outer peripheral surface of the developing roller surface, a sandpaper method in which the surface is rubbed with sandpaper, an etching method in which roughening is performed by chemical treatment using a solvent, spherical or polygonal (indefinite) particles A blasting method in which a large number of fine irregularities are formed by spraying the material at a constant pressure and a method combining these are proposed and practiced. Recently, a resin film layer containing a conductive pigment is provided on the surface of the developing roller to improve image quality. The toner supply member is made of a conductive sponge roller or brush roller, and is used for charging and transporting toner.

However, this type of developing device that has been put to practical use in the above configuration has the following drawbacks.
There are problems such as a ghost image (history phenomenon) that occurs when the toner on the developing roller is not efficiently supplied and peeled off, and a decrease in image density due to toner adhesion (filming) to the developing roller in long-term image forming. It was.
As these factors, the contact pressure between the developing roller and the toner supply member, the peripheral speed of the supply member at the contact portion between the toner supply member and the developing roller, etc. are increased. 1, the contact pressure between the developing roller and the toner supply member is P (20 ≦ Pg / cm ≦ 65), the peripheral speed ratio of the developing roller to the supply member is S (S = 1.1), and the ten-point average of the surface of the developing roller A configuration that satisfies the relationship of P + 70S−3.5R ≧ 90 is proposed, where the roughness Rz is R (5 ≦ RμmRz ≦ 15).
However, since the contact pressure between the developing roller and the supply member is as high as 20 to 65 g / cm, it has not yet been possible to prevent a decrease in image density due to toner adhering to the developing roller during long-term use.

JP 2000-098732 A

  The present invention has been made in view of the above-mentioned problems, and it is possible to prevent deterioration of image quality by stabilizing the toner adhesion amount on the photosensitive member at all times regardless of the initial time and the aging, and thereby developing the developer. Efficient supply and separation of toner on the carrier eliminates the history phenomenon that ghost images occur, and does not cause toner sticking to the developer carrier even during long-term image formation. It is an object of the present invention to provide a non-magnetic one-component developing device and an image forming apparatus that can prevent problems such as lowering.

In order to solve the above-mentioned problems, the present invention according to claim 1 is directed to forming an electrostatic latent image on a moving image carrier by image exposure using an image exposure apparatus, and forming the surface of the electrostatic latent image into a visible image. On the outer peripheral surface on which the developer is carried and conveyed on the image carrier, fine irregularities are formed by spraying spherical glass beads, and the surface has a roughness curve rough according to the measurement of JIS B0601. Non-magnetic one-component development comprising a developer carrying member having an Rz (10-point average roughness) of 15 to 30 μm and a supply member that contacts the developer carrying member and supplies the developer onto the developer carrying member In the apparatus, the contact pressure between the developer carrying member and the developer supply member is 0.3 to 0.8 g / cm.
According to a second aspect of the present invention, in the nonmagnetic one-component developing device according to the first aspect, the peripheral speed of the developer supply member is developed at a contact portion between the developer supply member and the developer carrier. The non-magnetic one-component developing device is characterized by being 1.4 to 1.8 times the peripheral speed of the agent carrier.

  According to a third aspect of the present invention, there is provided a latent image carrier, a charging unit that brings a charging member close to the surface of the latent image carrier, and a latent image forming unit that exposes the latent image carrier to form a latent image. An electric field is formed between the developing means for supplying a developer to the latent image on the surface of the latent image carrier to visualize it and a surface moving member that moves while contacting the latent image carrier. Transfer means for transferring a visible image formed on an image carrier onto a recording material sandwiched between the surface moving member or the surface moving member, and transfer residual toner remaining on the surface of the latent image carrier after transfer An image forming apparatus comprising: a cleaning unit that collects the toner from the latent image carrier; wherein the developing unit is the non-magnetic one-component developing unit according to claim 1.

  According to the present invention, the contact pressure between the developer carrier and the toner supply member is set to 0.3 to 0.8 g / cm, so that the toner is not clogged on the surface of the developer carrier and filming can be prevented. In addition, since the toner can be efficiently supplied to and peeled off from the developer carrying member, the toner adhesion amount on the developing roller can always be kept within a certain range regardless of the initial time. Accordingly, it is possible to provide a non-magnetic one-component developing device that can always perform good image formation without causing a ghost image or density reduction, and an image forming apparatus using the same.

Embodiments in which the present invention is applied to a developing device used in an image forming apparatus of an electrophotographic copying machine will be described below.
FIG. 1 is a cross-sectional view illustrating a schematic configuration of a developing device according to the present embodiment. The photosensitive drum 100 as an image carrier is rotated in the clockwise direction of the arrow at a peripheral speed of 200 mm / sec, for example. A developing device 101 is disposed on the right side of the photosensitive drum 100. Around the photosensitive drum 100, a well-known charging device, exposure optical system, transfer separation device, cleaning device, and static elimination device (all not shown) are disposed in order to perform the electrophotographic process. The developing device 101 of the present embodiment includes a casing 7 having an opening toward the surface of the photosensitive drum 100, and a developer carrying that is partially rotated from the opening and driven to rotate counterclockwise at a predetermined peripheral speed. A developing roller 1 as a body, a toner supply brush 3 as a developer supplying member that is rotationally driven in the clockwise direction of the arrow while being pressed against the right side portion of the developing roller 1, and a right side portion in the casing 7. Agitators 5 and 6 for supplying non-magnetic one-component developer (hereinafter referred to as toner) accommodated in a hopper portion as developer storage means to the surface of the supply brush 3 and stirring the toner in the hopper portion; A blade 2 as a developer regulating member for uniformizing the thickness of the toner layer on the developing roller 1 conveyed to the developing region that is opposed to the photosensitive drum 100 by the rotation of the roller 1; And a holder 8 which also serves as a top cover of the developing device 101 supports over de.

As shown in FIG. 1, the developing roller 1 is arranged so as to perform non-contact development facing the surface of the photosensitive drum 100 with a predetermined gap (0.15 mm) in the developing region, and the surface in the developing region. The moving direction is the same as that of the photosensitive drum 100, and the peripheral speed is substantially equal to the peripheral speed of the photosensitive drum 100, that is, in this example, about 220 mm / sec (photosensitive drum 100 peripheral speed: development). The peripheral speed of the roller is 1: 1.1).
The developing roller 1 of this embodiment is an aluminum cored bar having an outer diameter of φ20 mm, and the surface is roughened for the purpose of conveying the adhered toner. The bead blast particles (# 60) are sprayed at an air pressure of 4.5 kg / cm ² to roughen the surface roughness to Rz25 (10-point average roughness).

The supply brush 3 is composed of a brush roller having an outer diameter of φ16 mm (hair foot 3.5 mm) having a conductive nylon brush on a cored bar roller having an outer diameter of φ9 mm. As the conductive nylon brush layer, The resistance value is 10 ³ to 10 ⁸ Ωcm, the yarn thickness is ²⁰⁰ d / 96 f, the density is 144 K pieces / inch ² , and the charging polarity is positive (plus) charging. Then, the fabric in which the brush fibers are woven is obliquely wound and bonded around the core metal member with a pile interval (gap between the fabric and the fabric) of 0.5 or less. Further, the supply brush 3 is supported at a position where the supply brush 3 bites into the surface of the developing roller 1 by 1 mm, the contact pressure is 0.5 g / cm, and the surface is in contact with the developing roller 1 on the surface of the developing roller 1. It is driven so as to rotate in the forward direction moving in the same direction (reverse to the developing roller). The peripheral speed of the supply brush 3 is set to 1.6 times the peripheral speed of the developing roller 1, and is charged and charged. In the specific example of the present embodiment, the toner is negatively charged.

The toner has a weight average particle diameter in the range of 5 to 15 μm. The reason is that if the thickness is 5 μm or less, the adhesion to the developing roller 1 is strong and the developability is lowered, and even if developed, the weight is small and the image density is low, so it is difficult to obtain a high-quality image. On the contrary, it is easy to develop, and it is easy to generate as a background stain on the non-image portion of the image.
In addition, the toner is manufactured by melt-mixing a colorant and pulverizing a thermoplastic resin. As the thermoplastic resin, polyester resin, styrene-acrylic resin or the like is used. As the colorant, any quinacridone pigment, azo pigment, or perylene pigment can be used. The blade 2 is a polyurethane rubber having a thickness of 2 mm, and is disposed so as to contact the developing roller 1 with a contact pressure of about 10 g / cm. The toner layer on the developing roller 1 that has passed through the toner supply brush 3 is rubbed uniformly with the blade 2 in contact with the developing roller 1 to be a uniform thin layer. It is conveyed to the development area by rotation. At this time, in the development area, an optimum development bias is applied by a non-contact development method, and development is performed while the surface of the development roller 1 and the surface of the photosensitive drum 100 move at substantially constant speed. The agitators 5 and 6 supply the toner stored in the hopper to the surface of the toner supply brush 3 and agitate the stored toner. The toner supply brush 3 depends on the shape of the hopper and the fluidity and weight of the toner. If supply to the surface is possible, it may be omitted.

Hereinafter, the description up to the present embodiment will be described together with the examination results.
(1) Contact pressure between developing roller and supply roller The surface of the developing roller is blasted using glass beads # 60 (abrasive equivalent number JIS-R6001) particle size of 300 μm and roughened to Rz 25 ± 3 μm. The ten-point average roughness Rz, which is a roughness measurement method, is measured by a measurement method based on JIS-B0601, and represents the roughness of the roughness curve.
The inventor first swung the surface roughness Rz of the developing roller and confirmed how much surface roughness was necessary to supply sufficient toner for development. A developing roller having a Rz of 2.5 to 40 was prototyped and an initial check was performed. The surface roughness of the developing roller at this time is performed by sandblasting (indefinite particles, material alumina, particle size unknown), and the supply member is a conductive soft foamed resin material, a so-called sponge roller (the number of bubbles of cells 80 / Inch).
As a result, when Rz is 15 or less, the amount of toner transport is small and supply is insufficient, resulting in a thin density that cannot satisfy the specified image density. When Rz is higher than 30 μm, the blade pressure in the roller axis direction is not uniform. (The chance of contact with the blade is reduced), and the toner thin layer cannot be made uniform, resulting in uneven density, the toner charge amount is significantly reduced, fogging occurs on the image, and dot reproducibility is poor. . Therefore, it was confirmed that there was no initial image deterioration when the roughness on the surface of the developing roller was Rz 15 to 30 μm.

Therefore, running (paper passing confirmation) was performed with a developing roller of Rz25. However, the image density began to decrease after 5000 sheets were printed. The cause was that the toner was clogged in the supply sponge roller and the supply to the developing roller was gradually reduced. Therefore, the inventor measured the contact pressure between the developing roller and the supply sponge roller and found that it was 28-30 g / cm. It is thought that if the contact pressure of the supply sponge roller is lowered (by varying the amount of bite), toner clogging of the supply sponge roller can be prevented, so that the contact pressure is reduced to about 15 g / cm (the amount of bite 0.5) and running is performed again. It was. However, although the number of prints increased from the previous time, the image density decreased again after the 10000 prints.
However, lowering the contact pressure further (e.g., biting amount of 0.3) results in insufficient toner supply from the beginning, and the contact pressure is also related to the outside diameter accuracy (φ16 ± 0.3) of the sponge roller. Since there is concern about problems such as lack of stability, the combination of the developing roller and the supply sponge roller is abandoned, and the contact pressure is extremely low (contact pressure 0.5 g / cm, biting amount 1.0). I changed to and resumed running.

However, the density has decreased again after the printing of 40,000 sheets. As a result of the cause analysis, it was confirmed that the toner is fixed to the fine recesses on the surface of the developing roller. Considering that the current surface shape (fine concavo-convex by sandblasting) has a strong restraining force to hold the toner, investigation of blast particles was started to determine whether there is a surface shape in which the toner does not sink into the fine recesses of the developing roller.
Blasting particles (abrasives) that roughen the surface of the developing roller are commercially available from spherical shapes, cylindrical shapes, polygonal shapes, and a variety of particle sizes. , Deburring). Of these, if the surface is roughened with spherical particles, the toner will not be caught and the toner will not be entrapped, and it will be possible to supply and remove the toner efficiently, blasting with spherical particles and observing the surface did. The particles at that time are resin-based (phenol), glass-based (glass), and metal-based (stainless steel, steel).
Resin-based phenol particles have a soft roller base (aluminum), so even if the blast pressure and the distance to the workpiece are reduced, Rz is low (5 or less), and the toner can be transported to a roughness. There wasn't. Next, the developing roller surface was blasted with metallic spherical particles (stainless beads, steel beads). However, neither the stainless beads nor the steel beads were able to obtain spherical fine irregularities. It was confirmed that polygonal particles were mixed in spherical particles at a rate of 20%. Therefore, the target spherical surface shape could not be transferred and abandoned.

Finally, confirmation with glass beads was performed. The result was good, and spherical fine irregularities were transferred on the surface of the developing roller. Incidentally, the glass beads had a spherical shape of 98% or more.
By making the surface shape of the developing roller into spherical fine irregularities, the toner on the developing roller rotates and slides smoothly, so that supply and peeling can be performed efficiently, and toner sticking (filming) is also prevented. I was able to do it.
Next, the contact pressure between the toner supply brush and the developing roller was optimized. As for the method for changing the contact pressure, the amount of biting into the developing roller of the toner supply brush was changed in the same manner as the sponge roller in the previous period. As a result, the contact pressure range of 0.3 to 0.8 g / cm was optimal. When the contact pressure is less than 0.3 g / cm (biting amount 0.5), the toner is insufficiently supplied and the normal image density cannot be satisfied, and 0.8 g / cm (biting amount 1.5). ), The toner supply brush is likely to be wrinkled, resulting in a difference in toner supply and density unevenness in the sub-scanning direction.
The contact pressure P between the toner supply brush and the developing roller is measured by sandwiching a high quality paper (Ricoh T6200) having a thickness of 95 μm and a width of 5 cm between the contact portions of the developing roller and the toner supply brush, and the pulling force F of the paper F (G) was measured and substituted for the contact pressure at P = F / 5 (g / cm).

(2) Toner supply brush peripheral speed at the contact portion of the toner supply brush with the developer carrier The peripheral speed of the toner supply brush was optimized with respect to the peripheral speed of the developer carrier. If the peripheral speed ratio is less than 1.4, the toner is insufficiently supplied and the normal image density cannot be satisfied. If the peripheral speed ratio exceeds 1.8, the conveyed toner is scraped off and the supply is insufficient. As a result, the normal image density could not be satisfied.
Reflecting the above (1) and (2), paper passing confirmation was performed. Even when the number of sheets exceeded 90,000, no problem occurred, and a good image was always provided.
2 and 3 show curves showing the same roughness after sandblasting and blasting with glass beads. It can be seen that the glass beads are smoother.
FIG. 4 is an image of the surface roughened by glass bead blasting taken with a microscope, and it can be clearly seen that the spherical shape of the glass beads is transferred.
FIG. 5 is a sample roughened with steel beads, and it can be clearly seen that the spherical shape is not transferred at all.
4 and 5, the surface roughness was Rz = 17 μm for both, and used as comparative samples.

1 is a cross-sectional view illustrating a schematic configuration of a developing device according to an embodiment. It is a figure which shows Rz17micrometer roughness curve by a sandblasting process. It is a figure which shows Rz17micrometer roughness curve which carried out the blast process with the glass bead. It is the image which image | photographed the surface roughened by glass bead blasting with the microscope. It is the image which image | photographed the surface roughened with the steel bead with the microscope.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Photosensitive drum 101 Developing apparatus 1 Developing roller 2 Blade 3 Toner supply brush 4 Film 5, 6 Agitator 7 Casing 8 Holder

Claims (3)

An outer peripheral surface that forms an electrostatic latent image on the moving image carrier by image exposure using an image exposure device, carries the developer on the surface, and conveys and develops the electrostatic latent image on the image carrier. On top, fine irregularities are formed by spraying spherical glass beads, and the surface of the developer is Rz (10 point average roughness) 15-30 μm with a roughness curve conforming to the measurement of JIS B0601 A non-magnetic one-component developing device comprising a body and a supply member that contacts the developer carrier and supplies the developer onto the developer carrier.
A nonmagnetic one-component developing device, wherein a contact pressure between the developer carrying member and the developer supply member is 0.3 to 0.8 g / cm. In the non-magnetic one-component developing device according to claim 1,
The peripheral speed of the developer supply member at the contact portion between the developer supply member and the developer carrier is 1.4 to 1.8 times the peripheral speed of the developer carrier. Magnetic one-component developing device. A latent image carrier, a charging unit that brings a charging member close to the surface of the latent image carrier, a latent image forming unit that exposes the latent image carrier to form a latent image, and a latent image on the surface of the latent image carrier. An electric field is formed between the developing means for supplying a developer to the surface to make a visible image and the surface moving member that moves on the surface while being in contact with the latent image carrier, thereby forming a visible image formed on the latent image carrier. Transfer means for transferring an image onto a recording material sandwiched between the surface moving member or the surface moving member, and cleaning means for collecting transfer residual toner remaining on the surface of the latent image carrier after the transfer from the latent image carrier. In an image forming apparatus comprising:
3. The image forming apparatus according to claim 1, wherein the developing unit is the non-magnetic one-component developing device according to claim 1.

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