JP3035627B2 - Electrostatic latent image developing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention supplies a non-magnetic one-component developer externally supplemented with an auxiliary agent as necessary to a rotatable developer carrier,
Carrying and transporting the developer on the surface of the developer carrier,
In a developing region where the latent image carrier and the developer carrier are opposed to each other, the electrostatic latent image formed on the latent image carrier is visualized by the developer carried on the developer carrier. The present invention relates to an electrostatic latent image developing method.

[Conventional technology]

An image forming apparatus such as an electronic copier, a printer or a facsimile that forms a latent image on a latent image carrier and visualizes the latent image with a developer to obtain a recorded image is a dry type using a powdery developer. Is widely used.

As such a powdery developer, a two-component developer having a toner and a carrier and a one-component developer without a carrier are known, and two-component development using the former two-component developer is known. In the method, although a relatively stable and good recorded image is obtained, deterioration of the carrier and fluctuation of the mixing ratio of the toner and the carrier are apt to occur, maintenance of the apparatus is complicated, and the structure of the entire apparatus is easily enlarged. Has disadvantages.

From such a viewpoint, a one-component developing method using a one-component developer which does not have the above-mentioned disadvantages has attracted attention. The one-component developer includes a toner composed of only a toner and a mixture of a toner and an auxiliary agent to which an auxiliary agent is added as necessary. As the toner, there are a magnetic toner in which magnetic powder is kneaded into each toner particle itself, and a non-magnetic toner containing no magnetic material.

Here, since the magnetic material is generally opaque, if a color image including full-color or multi-color is formed with a magnetic toner, the developed visible image becomes unclear and a vivid color image cannot be obtained. Therefore, it is desirable to adopt a one-component developing method using a non-magnetic toner especially for color development.

By the way, in a developing device employing a one-component developing method, a one-component developer is carried on a developer carrier and transported. In a developing region where the developer carrier and the latent image carrier are opposed to each other, The electrostatic latent image formed on the latent image carrier is visualized with a developer, but in order to form a high quality visible image of a predetermined density, a large amount of sufficiently charged toner must be applied to the developing area. The latent image needs to be conveyed and visualized with the toner.

When the magnetic toner is used, the above-described requirement can be satisfied relatively easily because the one-component developer can be carried on the developer carrier by using the magnetic force of a magnet provided in the developer carrier. Is possible.

However, when a non-magnetic one-component developer is used,
Since this cannot be carried on the developer carrying member by magnetic force, it is difficult to satisfy the above requirements. Various countermeasures against this have been proposed in the past. For example, JP-A-61-42672 discloses a developer carrier (developing roller).
A layer of a dielectric (insulator) is formed on the surface of the substrate, and a developer supply member such as a sponge roller is pressed against the layer to frictionally charge the two with different polarities. A method has been proposed in which a non-magnetic toner charged to a polarity is electrostatically attached to a dielectric and such a one-component developer is transported to a development area. However, even with this method, the strength of the electric field formed in the vicinity of the dielectric surface cannot be sufficiently increased, so that it is difficult to carry a large amount of toner on the surface of the developing roller, and the developing roller can be transported to the developing area. Insufficient amounts of the agent make it difficult to form a high-density visible image.

A configuration in which a non-magnetic toner is applied between the developing roller and the developer supply member in a direction in which the non-magnetic toner is electrostatically transferred to the developing roller is also known, but even if such a configuration is added, It is difficult to attach a sufficient amount of toner to the developing roller.

Examples of the toner supply member include a conductive foam of 10 ² to 10 ⁶ Ω · cm (JP-A-60-229057), an elastic body with a skin layer (JP-A-60-229060), and a fur brush. (Japanese Patent Application Laid-Open No. 61-42672) and the like, and as a developing roller, a metal body having an uneven surface (Japanese Patent Application Laid-Open No. 60-53976), an insulating coated roller body ( Japanese Unexamined Patent Publication No. Sho 55-46768 discloses a medium resistance coated roller (Japanese Unexamined Patent Publication No. 58-13278) and an electrode roller having an insulator and a conductive surface (Japanese Unexamined Patent Publication No. Sho 53-36245). .

In a developing apparatus using a non-magnetic one-component developer, a sponge roller is disclosed in JP-A-60-229057, an elastic roller is disclosed in JP-A-62-222960, and a developing roller is disclosed in JP-A-61-52663.
In the publication, a fur brush or the like is used to apply electric charge to the toner by frictional charging between the toner and the replenishing member, and further, by friction in contact with the developing roller, electrostatically attaches the toner to the developing roller. The latent image on the photosensitive member is developed by controlling the toner layer using a layer thickness regulating member such as a blade. As the material of the developing roller, various materials such as an insulating material, a medium-resistance material, and a laminated material are used.

According to the methods described in these references, toner is adhered to the developing roller by frictional charging between the toner replenishing member and the developing roller. And toner adhesion is insufficient. The following describes the optimal amount of adhesion and the amount of charge in the non-magnetic one-component developing system.

For black and white, the charge amount is important, and it is generally 10 to
20 μC / g. If the value is smaller than this value, the image quality such as background smear and sharpness is inferior. Regarding the coating weight, although the adhesion amount on the developing roller is 0.1 to 0.3 mg / cm ^2, the transfer paper is required 0.4~0.5mg / cm ^2, the speed of the developing roller of the photosensitive body speed 3 to 4 times, the amount of adhered toner is covered. However,
For the rotation of the developing roller 3 to 4 times, "from the rear end of toner"
That is, when the solid portion is developed, a phenomenon that the density at the rear end of the image becomes high occurs. In order to prevent this phenomenon, the speed of the developing roller should be close to the speed of the photoconductor. That is, the number of rotations must be reduced by increasing the amount of adhesion on the developing roller.

On the other hand, in the color toner, the color characteristics are small in degree of coloring in comparison with black toner, and when you try to improve the "from toner rear", further more 0.8~1.2mg / cm ² compared to the black toner
Is required on the developing roller. Also, regarding the charge amount, in order to obtain a stable image, 5 to 20 μm
A value of C / g (preferably 10-15 μC / g) is desired.

As a method for solving these problems, the present inventors have previously described "a one-component developer composed of a non-magnetic toner externally supplemented with an auxiliary agent as needed on a rotatable developer carrier." The developer is carried on the surface of the carrier, and is conveyed. The electrostatic latent image formed on the latent image carrier is developed in a developing area where the latent image carrier and the developer carrier face each other. In a developing method of visualizing an image with the developer carried on a developer carrier, a plurality of minute particles are formed in the vicinity of the surface of the carrier by selectively holding electric charges on the surface of the developer carrier. An image forming method in which a closed electric field is formed, the charged toner is sucked by the closed electric field, the developer is adhered to and supported on the surface of the developer carrier, and the electrostatic latent image is visualized by the carried developer. Suggested.

According to such a method, a large number of minute closed electric fields (microfields) are formed in the vicinity of the surface of the developer carrying member, so that the electric field intensity can be significantly increased as compared with the related art.
It has many advantages such that a large amount of charged non-magnetic toner can be carried on a developer carrier and transported to a development area.

[Problems to be solved by the invention]

An object of the present invention is to form a plurality of microfields in the vicinity of the surface of the developer carrying member, and a method for developing an electrostatic latent image in a developing area after holding the toner on the carrier by the microfields. In the developing area, the surface of the developer carrier and the surface of the electrostatic latent image can be maintained and maintained at a constant distance between the surface of the developer carrier and the surface of the electrostatic latent image carrier. A developing method in which a multi-layer thin layer of toner is formed on the surface of the developer carrying member by contacting the surface of the electrostatic latent image carrier, and as a result, a high-quality image is obtained, and of course, the development density unevenness does not occur. To provide.

[Means for solving the problem]

According to the present invention, the elastic surface layer of the developer carrying member has a conductive portion made of a conductive material and an insulator made of insulating particles distributed on the surface, and the conductive portion is rubbed by the toner supply member. By charging and selectively holding electric charges on the surface of the developer carrier, a number of minute closed electric fields are formed near the surface of the developer carrier, and on this developer carrier,
If necessary, a one-component developer composed of a toner to which an auxiliary agent is added is supplied by a toner supply member in contact with the developer carrier, and the developer is applied to the surface of the developer carrier by the minute closed electric field. An electrostatic latent image developing method for developing the electrostatic latent image by contacting the developer carrier and a latent image carrier for carrying an electrostatic latent image; Is made of a conductive elastomer, insulating particles are dispersed at least in the vicinity of the surface, and a part of the particles are exposed on the surface, and the volume average particle diameter of the toner used is exposed on the surface. To provide a method for developing an electrostatic latent image, wherein the average particle size of the insulating particles is 1/3 or less of the average particle size of the conductive particles, and the average particle size of the insulating particles exposed on the surface is 30 to 500 μm. The electrostatic latent image developing method To offer.

The development method of the present invention eliminates the need for precise gap maintenance and the like between a rigid latent image carrier such as a photoconductor provided with photoconductivity on a metal drum and a developer carrier, and is designed. The tolerance can be widened, and a multilayer thin layer of toner is formed on the surface of the developer carrying member. As a result, a high-quality image free from uneven development can be stably obtained.

 Hereinafter, such an electrostatic latent image developing method will be described.

FIG. 1 shows an outline of a typical developing device useful for carrying out this developing method, focusing on a developer carrier. In FIG. 1, the toner 60 contained in the toner tank 70 is
The toner is forcibly brought to a toner supply member (sponge roller, fur brush, etc.) 40 by a stirring blade (toner supply auxiliary member) 50, and the toner 60 is supplied to the toner supply member 40. On the other hand, the developer carrier (developing roller:
For example, 20φ) 20 rotates in the direction of the arrow (for example, 100 rpm)
Then, it reaches a contact portion with the toner supply member 40. The toner supply member 40 rotates in the opposite direction to the developer carrier 20 (for example, 67 rpm)
Then, the developer carrier 20 and the toner 60 are charged, and the toner 60 adheres to the developer carrier 20. Further, the developer carrier 20
Is rotated, and the toner adhered on the developer carrier 20 is stabilized in charge while being controlled in thickness by the toner layer thickness regulating member (elastic blade) 30, and reaches the developing region 80. In the developing area 80, the developer carrier 20 and the latent image carrier 10 are brought into rotational contact in the same direction on the surface thereof (rotation speed of the latent image carrier: for example, 120 rpm). The latent image is developed. Here, if necessary, the developer carrier 2
The optimum image can be controlled by applying a bias 90 such as DC, AC, DC superimposed AC, or pulse to the toner supply member 40. Further, the amount of deformation of the surface elastic layer on the surface of the developer carrier in the developing area is set to be 3/10 of the thickness of the elastic layer.
It is preferable that the setting is performed as follows in order to prevent the deformation of the entire developer carrying member from occurring and to suppress the generation of vibration due to contact.

Next, the developer carrier used in the present invention will be described. The developer carrier used in the present invention is, as described above,
A typical example of the structure is that a surface layer made of an elastic conductive material in which insulating particles are dispersed is formed on a conductive substrate. As the conductive material, a material of 10 ¹² Ω · cm or less, preferably 10 ⁸ Ω · cm or less is used. Specifically, a material obtained by adding a conductivity-imparting agent to a rubber material (elastomer) can be used. The following are specific examples of the rubber material.

Diene rubbers such as styrene-butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), nitrile-butadiene rubber (NBR), nitrile-isoprene rubber (NIR), chloroprene rubber (CR); butyl rubber (IIR) ), Olefin rubbers such as ethylene-propylene rubber (EPM, EPDM) and chlorosulfonated polyethylene (CSM); ether rubbers such as epichlorohydrin rubber (CHR, CHC); other silicone rubbers, fluorine rubbers, acrylic rubbers, urethane rubbers And elastomer materials such as thermoplastic elastomers such as styrene, olefin, polyvinyl chloride, urethane, polyester, polyamide, fluorine and chlorinated polyethylene.

Further, as the conductivity-imparting agent, metal powders such as Ni and Cu;
Carbon black such as furnace black, lamp black, thermal black, acetylene black and channel black; conductive oxide such as tin oxide, zinc oxide, molybdenum oxide, antimony oxide and potassium titanate; plating on titanium oxide and mica Electroless plated material; examples include inorganic fillers such as graphite, metal fibers, and carbon fibers, and surfactants.

Further, an organic ion conductor in which metal ions are coordinated to a polymer matrix such as polyethylene oxide or polysiloxane can also be used.

On the other hand, as the insulating particle material, one having 10 ¹³ Ω · cm or more, preferably 10 ¹⁴ Ω · cm or more is used. Moreover,
According to the study of the present inventors, it has been found that the particle size of the insulating particles exposed on the surface of the developer carrying member greatly affects the developing property. That is, when the volume average particle diameter (usually 7 to 20 μm) of the toner used for development exceeds 1/3 of the average particle diameter of the insulating particles exposed on the surface of the developer carrier. However, it is impossible to form a multilayer thin layer of toner on the surface of the developer carrying member. This is presumably because, when the toner particle diameter is larger than the magnitude of the closed electric field on the surface of the developer carrier, the toner suction force to the developer carrier acts. However, if the volume average particle diameter of the toner used is 1/3 or less of the particle diameter of the insulating particles exposed on the surface of the developer carrier, a good multilayer thin layer of the toner is formed on the surface of the developer carrier. Are formed, and a high-quality image can be stably obtained.

The average particle size of the insulating particles exposed on the surface of the developer carrying member is preferably in the range of 30 to 500 μm, particularly preferably 50 to 500 μm. This is because the magnitude of the minute closed electric field formed on the surface of the developer carrier rapidly decreases when the diameter of the insulating particles is less than 30 μm, and the function of retaining the toner is not provided. Conversely, if the diameter of the insulating particles exceeds 500 μm, the difference between the toner-adhered portion and the non-adhered portion is identified in the solid portion of the image, and a uniform solid image cannot be obtained.

It should be noted that the insulating particles may be of a regular shape or of an irregular shape. It is excellent in that it does not separate from the material.

Specific examples of these materials include alumina, beryllia, magnesia, silicon nitride, boron nitride, mullite,
Inorganic particles such as steatite, forsterite, zircon, cordierite, epoxy resin, fluorine resin,
Organic particles such as a silicone resin, an acrylic resin, a polyamide resin, a polystyrene resin, a phenol resin, a melamine resin, and a polyethylene resin are exemplified.

It is preferable to use an elastomer as the insulating particles. As the elastomer in this case, the same materials as those exemplified as the elastomer used for the conductive elastomer are used. In order to produce insulating elastomer particles, after freezing the elastomer with dry ice or the like, pulverizing and pulverizing, a method of pulverizing and pulverizing with a grinder, forming an aqueous emulsion using a surfactant or the like, A known method such as a curing method is employed.

In addition, as the elastomer used for the conductive material and the insulating particles, silicone rubber is particularly preferable from the viewpoints of low hardness, environmental resistance, releasability, and the like.

The amount of the insulating particles added to the conductive material is appropriately selected in the range of 10 to 200 parts by weight based on 100 parts by weight of the conductive material. The surface insulation area of the developer carrier is 50-80%
Is preferable, and the amount of the insulating particles to be added is appropriately adjusted so as to be within this range after the preparation of the carrier.

Next, a method for manufacturing the developer carrying member used in the present invention will be described. FIG. 2 shows a typical configuration example (an enlarged partial cross-sectional view of the surface) of the surface of the developer carrying member used in the present invention.
The developer carrier having the surface shown in FIG. 2 is obtained by adding the insulating particles to the conductive material based on a normal dispersion method such as ball milling or kneading, and then subjecting the mixed material to injection molding. , Extrusion, spray coating, dipping, etc., by forming on a conductive substrate typified by a metal roller such as SUS, iron, Al, etc., and then polishing to make the surface smooth It is an example.

Note that a primer can be used to improve the adhesion between the conductive material and the conductive substrate. In this case, the primer is preferably conductive.

In addition to the structure example of the developer carrier described above, as a method of forming a microfield near the surface of the developer carrier, the surface of the developer carrier is configured to be insulative, and a uniform minute charge pattern is directly applied. There is also a way to do
The insulating surface layer may be made of an elastic rubber material.

When developing while rotating the developer carrier and the latent image carrier in the same direction and at substantially the same speed as shown in FIG. 1, compression set (JIS K6301) as the developer carrier is required.
) Is preferably 25% or less. As a result, a sufficient amount of toner can be carried and conveyed on the developer carrying member, and at the same time, the occurrence of vibration due to the contact rotation between the two carrying members can be suppressed, and there is no development density unevenness. Has advantages.

〔The invention's effect〕

Since the developing method of the present invention has the above-described structure, the design top surface is designed to maintain and maintain a constant distance between the surface of the developer carrier and the surface of the electrostatic latent image carrier in the developing area. In addition to requiring no special means, the method produces a large micro-closed electric field on the surface of the developer carrier, and forms a stable multilayer thin layer of toner. As a result, a high-quality image can be stably obtained. Can be.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view centering on a developer carrying portion showing an example of a developing device in which a microfield electric field is formed on a developer carrying member useful for carrying out the present invention. Also,
FIG. 2 is a schematic partial sectional view of the surface of the developer carrier used in the present invention. 10 electrostatic latent image carrier, 20 developer carrier, 30 toner layer thickness regulating member, 40 toner supply member, 50 stirring blade, 60 toner, 70 toner tank , 80: developing area, 90: bias.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yuichi Ueno 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company, Ltd. (72) Inventor Yasuo Hirano 1-3-6 Nakamagome, Ota-ku, Tokyo (56) References JP-A-55-62469 (JP, A) JP-A-60-70457 (JP, A) JP-A-63-106768 (JP, A) (58) Fields investigated Int.Cl. ⁷ , DB name) G03G 15/08-15/09

Claims (2)

(57) [Claims] An elastic surface layer of a developer carrying member has a conductive portion made of a conductive material and an insulator made of insulating particles distributed on the surface, and the conductive portion is formed by a toner supply member. By triboelectrically charging and selectively holding electric charge on the surface of the developer carrier, a number of minute closed electric fields are formed near the surface of the developer carrier, and on this developer carrier,
If necessary, a one-component developer composed of a toner to which an auxiliary agent is added is supplied by a toner supply member in contact with the developer carrier, and the developer is applied to the surface of the developer carrier by the minute closed electric field. An electrostatic latent image developing method for developing the electrostatic latent image by contacting the developer carrier with a latent image carrier carrying an electrostatic latent image; Is made of a conductive elastomer, insulating particles are dispersed at least in the vicinity of the surface, and some of the particles are exposed on the surface, and the volume average particle diameter of the toner used is exposed on the surface. An electrostatic latent image developing method, wherein the average diameter of the insulating particles is 1/3 or less. 2. An electrostatic latent image developing method according to claim 1, wherein said insulating particles exposed on said surface have an average particle size of 30 to 500 μm.