JPH04283776A - Image forming method - Google Patents

Abstract

PURPOSE:To obtain the image of high density and high quality for a long term by laminating two or more toner layers on the developer carrier stably and uniformly as to a developing for forming a large number of fine closed electric fields near the surface of a developer carrier. CONSTITUTION:The toner which is constituted of at least binding resin and colorant and also whose dielectric nonstant is <=4.0 is used. By selectively holding the charge on the surface of the developer carrier 10, a large number of fine clopsed electric fields is formed near the surface of the carrier 10, and one component system developer comstituted of the toner is supplied on the carrier 10, and the developer is carried on the surface of the carrier 10 by the fine closed electric field, and then, an electrostatic latent image is visualized by the carried developer.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention supplies a one-component developer to which an auxiliary agent is externally added as necessary to a rotationally driven developer carrier, and applies the developed material to the surface of the developer carrier. The electrostatic latent image formed on the latent image carrier is conveyed while supporting the developer, and the electrostatic latent image formed on the latent image carrier is transferred to the developing area where the latent image carrier and the developer carrier face each other. The present invention relates to an image forming method in which images are visualized using a developer.

0002

2. Description of the Related Art In image forming apparatuses such as electronic copying machines, printers, and facsimile machines, an electrostatic latent image is formed on a latent image carrier and visualized with a developer to obtain a recorded image.
Dry type developing devices that use powdered developer are widely used.

[0003] As such powder-like developers, two-component developers containing toner and a carrier and one-component developers that do not contain a carrier are known. Although the two-component development method can provide relatively stable and good recorded images, it is prone to carrier deterioration and fluctuations in the toner-to-carrier mixture ratio, and the equipment is complicated to maintain and manage, and the overall equipment structure is large. It has the disadvantage that it can easily become

From this point of view, a one-component development system using a one-component developer that does not have the above-mentioned drawbacks is attracting attention. One-component developer consists of only toner,
There are also those to which auxiliary agents are externally added as necessary. Furthermore, toners include magnetic toners in which magnetic powder is kneaded into each toner particle itself, and non-magnetic toners that do not contain magnetic material. Here, since magnetic materials are generally opaque,
When a color image including full color or multicolor is formed using magnetic toner, the developed visible image becomes unclear and a vivid color image cannot be obtained. Therefore, especially for color development, it is desirable to adopt a one-component development method using non-magnetic toner.

By the way, in a developing device employing a one-component development method, a one-component developer is carried on a developer carrier and transported, and the developer carrier and the latent image carrier face each other for development. In the area, the electrostatic latent image formed on the latent image carrier is visualized using a developer, but in order to form a high-quality visible image with a predetermined density, a large amount of sufficiently charged toner must be used. It is necessary to convey the latent image to a development area and visualize the latent image using the toner.

When magnetic toner is used, the one-component developer can be supported on the developer carrier using the magnetic force of a magnet installed inside the developer carrier, so the above requirements can be met relatively easily. It is possible to meet the requirements.

However, when a non-magnetic one-component developer is used, it is difficult to satisfy the above requirements because it cannot be supported on a developer carrier by magnetic force. Various countermeasures against this problem have been proposed in the past.
For example, Japanese Patent Laid-Open No. 61-42672 discloses that a dielectric (insulator) layer is laminated on the surface of a developer carrier (developing roller), and a developer supplying member made of a sponge roller, for example. are brought into pressure contact with each other, triboelectrically charging them to opposite polarities, and electrostatically attaching non-magnetic toner charged to the opposite polarity to the dielectric, and transporting the one-component developer to the development area. A method has been proposed. However, even with this method, it is not possible to sufficiently increase the strength of the electric field formed near the dielectric surface.
It is difficult to carry a large amount of toner on the surface of the developing roller, and the amount of developer that can be transported to the developing area is insufficient, making it difficult to form a high-density visible image.

[0008]Also, a configuration is known in which an electric field is applied between the developing roller and the developer supply member in a direction in which the non-magnetic toner electrostatically moves toward the developing roller. However, it is difficult to make a sufficient amount of toner adhere to the developing roller.

[0009] As the toner supply member, 102~
106Ω・cm conductive foam (Japanese Patent Application Laid-Open No. 60-2290
No. 57), elastic body with skin layer (Japanese Patent Application Laid-Open No. 60-229
No. 060) and fur brush (Japanese Patent Laid-Open No. 61-426)
It has been proposed to use a metal body with an uneven surface (Japanese Patent Application Laid-Open No. 60-53976), an insulating coated roller body (Japanese Patent Laid-Open No. 55-46768), etc. as a developing roller. A medium-resistance coated roller (Japanese Patent Application Laid-Open No. 58-132768) and an electrode roller having an insulating surface and a conductive surface (Japanese Patent Application Laid-Open No. 53-36245) are disclosed.

Further, in a developing device using a non-magnetic one-component developer, JP-A-60-229057 uses a sponge roller, JP-A-62-229060 uses an elastic roller, and JP-A-61-52663 uses a sponge roller. Using a fur brush or the like, the toner is charged by frictional charging between the toner and the replenishing member, and the toner is electrostatically adhered to the developing roller by the friction in contact with the developing roller. The layer thickness regulating member is used to control the toner layer and develop the latent image on the photoreceptor. Various materials are used for the developing roller, such as insulating materials, medium resistance materials, and laminated materials.

According to the methods shown in these references, toner adhesion to the developing roller is achieved by friction between the toner replenishing member and the developing roller, but since the friction is caused by the member to which the toner is attached, sufficient charging is not achieved. is difficult to obtain, resulting in insufficient toner adhesion. The requirement for this large amount of deposition also makes one-component development difficult.

Furthermore, as shown in Japanese Patent Application Laid-Open No. 54-51841, after scraping off the one-component developer on the developing roller after passing through the developing area, the surface layer of the developing roller is coated with A technique has also been proposed in which a corona discharge is applied to apply an electric charge, and then non-magnetic toner is electrostatically and actively deposited on the developing roller using a developer supplying member. Also, the amount of developer carried on the surface of the developing roller cannot be increased, and a large amount of developer cannot be conveyed to the developing area.

As a method for solving these problems, the present inventors have previously developed a one-component system consisting of a non-magnetic toner to which an auxiliary agent is added externally to a rotatably driven developer carrier. A developer is supplied, the developer is carried on the surface of the carrier and transported, and a latent image is formed on the latent image carrier in a development area where the latent image carrier and the developer carrier face each other. In a developing method in which an electrostatic latent image is visualized by the developer carried on a developer carrier, electric charges are selectively retained on the surface of the developer carrier, so that the electrostatic latent image is visualized in the vicinity of the surface of the developer carrier. An image in which a large number of minute closed electric fields are formed, charged toner is attracted by the closed electric fields, developer is attached and carried on the surface of a developer carrier, and the electrostatic latent image is visualized by the carried developer. ``formation method'' was proposed.

[0014] In this method, since a large number of micro-closed electric fields (micro-fields) are formed near the surface of the developer carrier, the electric field strength can be significantly increased compared to the conventional method, and a large amount of sufficiently charged This method has many advantages, such as being able to carry toner on a developer carrier and transport it to a developing area.

[0015]

[Problems to be Solved by the Invention] However, according to subsequent research by the present inventors, it has been found that in the development method that forms a large number of minute closed electric fields (microfields) near the surface of the developer carrier as described above, If conventionally known toners are used as they are, it is difficult to always maintain a stable toner layer on the developer carrier with two or more layers, and the toner layer becomes thinner and the amount of toner to be developed decreases. This may cause the density of the image area to become low, the toner layer may become uneven, resulting in uneven development, and the density of the image area may become uneven, or the toner on the developer carrier may have opposite polarity. It has been found that toner adheres to non-image areas, causing problems such as fogging.

Therefore, an object of the present invention is to be able to stably and uniformly laminate toner in two or more layers on a developer carrier in the above-described image forming method, and to produce high-density, high-quality images over a long period of time. An object of the present invention is to provide an image forming method that can obtain images.

[0017]

[Means for Solving the Problem] As a result of extensive studies, the present inventors found that a toner containing a binder resin and a colorant and having a specific dielectric constant is suitable for the above purpose. The invention was completed.

That is, according to the present invention, by selectively retaining charges on the surface of the developer carrier, a large number of minute closed electric fields are formed near the surface of the developer carrier, and the developer carrier is A one-component developer consisting of toner to which an auxiliary agent is externally added as necessary is supplied onto the body, the developer is carried on the surface of the developer carrier by the minute closed electric field, and the carried developer causes static An image forming method for visualizing an electric latent image, characterized in that a toner comprising at least a binder resin and a colorant and having a dielectric constant of 4.0 or less is used. provided.

In the present invention, by using a toner that is composed of at least a binder resin and a colored resin and has a dielectric constant of 2.8 or less, two or more layers are formed on the developer carrier.
It is possible to layer toner stably and uniformly, and it is possible to obtain high-density, high-quality images over a long period of time. If a toner with a dielectric constant value higher than 4.0 is used, the toner holding power by the microfield will be weakened, toner layer formation will be poor, and uneven image density and toner fogging on the background will likely occur. Become.

As the binder resin used in the toner used in the present invention, all binder resins conventionally used as binder resins for toners can be used. Specifically, monopolymers of styrene and its substituted products such as polystyrene, polychlorostyrene, and polyvinyltoluene; styrene/
p-chlorostyrene copolymer, styrene/propylene copolymer, styrene/vinyltoluene copolymer, styrene/vinylnaphthalene copolymer, styrene/methyl acrylate copolymer, styrene/ethyl acrylate copolymer,
Styrene/butyl acrylate copolymer, styrene/octyl acrylate copolymer, styrene/methyl methacrylate copolymer, styrene/ethyl methacrylate copolymer,
Styrene/butyl methacrylate copolymer, styrene/α
- Methyl chlormethacrylate copolymer, styrene/acrylonitrile copolymer, styrene/vinyl methyl ether copolymer, styrene/vinyl ethyl ether copolymer, styrene/vinyl methyl ketone copolymer, styrene/
butadiene copolymer, styrene/isoprene copolymer,
Styrenic copolymers such as styrene/acrylonitrile/indene copolymer, styrene/maleic acid copolymer, styrene/maleic acid ester copolymer; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene , polypropylene, polyester, polyvinyl butyral butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, paraffin wax, etc. These can be used alone or in combination of two or more. Note that among these, it is advantageous to use polystyrene, styrene resin, and epoxy resin.

[0021] Furthermore, as the colorant used in the toner used in the present invention, all pigments and dyes conventionally used as colorants for toners can be used. Specifically, carbon black, lamp black, iron black, ultramarine blue, nigrosine dye, aniline blue, calco oil blue,
DuPont Oil Red, Quinoline Yellow, Methylene Blue Chloride, Phthalocyanine Blue, Phthalocyanine Green, Hansa Yellow G, Rhodamine 6C Lake,
chrome yellow, quinacridone, benzidine yellow,
Examples include malachite green, malachite green hexalate, oil black, azo oil black, rose bengal, monoazo dyes and pigments, disazo dyes and pigments, trisazo dyes and pigments, and mixtures thereof.

[0022] In the toner of the present invention, it is effective to add a charge control agent to impart charge. Examples of charge control agents in this case include nigrosine dyes, quaternary ammonium salts, basic dyes, and amino group-containing polymers that impart positive polarity to the toner, and those that impart negative polarity to the toner. , chromium-containing monoazo dyes, chlorine-containing organic dyes, metal salts of salicylic acid and salicylic acid derivatives, etc., but are not limited to these.

Furthermore, in the toner used in the present invention,
In order to provide mold release properties, in addition to synthetic waxes such as low molecular weight polyethylene and polypropylene, vegetable waxes such as candelilla wax, carnauba wax, rice wax, tree wax, and jojoba oil; beeswax, lanolin, and whale oil are used. It can contain animal waxes such as wax; mineral waxes such as montan wax and ozokerite; oil-based waxes such as hydrogenated castor oil, hydroxystearic acid, fatty acid amides, and phenol fatty acid esters.

In addition to the above-mentioned binder resin, colorant, etc., the toner used in the present invention may contain various plasticizers ( It is also possible to add auxiliary agents such as dibutyl phthalate, dioctyl phthalate, etc.), resistance adjusters (tin oxide, lead oxide, antimony oxide, etc.). Furthermore, in the present invention, after producing toner particles (5 to 20 μm), T
Adding fine powders such as iO2, Al2O3, SiO2,
It is also effective to modify the fluidity of the toner by coating the toner particle surface with these, or to add zinc stearate, phthalic acid, etc. to reduce the deterioration of the photoreceptor.

As described above, the image forming method of the present invention forms a large number of minute closed electric fields near the surface of the developer carrier by selectively retaining charges on the surface of the developer carrier. , A one-component developer consisting of toner to which an adjuvant is externally added as necessary is supplied onto this developer carrier, and the developer is supported on the surface of the developer carrier by the minute closed electric field. An electrostatic latent image is visualized by a supported developer.

The image forming method of the present invention will be explained below. FIG. 1 shows an outline of a typical developing device useful for carrying out this image forming method, centering on the developer carrier section. In FIG. 1, the toner 60 contained in the toner tank 70 is transferred to a toner supply member (such as a sponge roller or a fur brush) by a stirring blade (toner supply auxiliary member) 50.
40 , the toner 60 is supplied to the toner supply member 40 . On the other hand, the developer carrier (developing roller) 20 that has completed the development rotates in the direction of the arrow (for example, 40
0 rpm) and reaches the contact portion with the toner supply member 40. The toner supply member 40 rotates in the opposite direction to the developer carrier 20, charges the developer carrier 20 and the toner 60, and causes the toner 60 to adhere to the developer carrier 20. Further, the developer carrier 20 rotates, and the toner adhering to the developer carrier 20 is removed by the toner layer thickness regulating member (elastic blade) 3.
0, the charging is stabilized while the thickness is controlled, and the developing area 80 is reached. In the development area 80, the latent image is developed by contact or non-contact development. Here, if necessary, direct current may be applied to the developer carrier 20 and the toner supply member 40.
An optimal image can be controlled by applying bias voltages such as alternating current, direct current superimposed alternating current, and pulses.

Next, the mechanism of toner adhesion to this type (electrode type) developer carrier 20 will be explained. As an example of the developer carrier 20, as shown in FIG. 2, for example, the developer carrier 20 is configured such that a dielectric portion and a conductive portion coexist in a small area on its surface. Regarding the size of the area, when the shape is circular, minute areas having a diameter of 30 to 2000 μm, preferably 100 to 400 μm are distributed randomly or according to a certain rule. The area ratio is preferably in the range of 50 to 80% of the area of the dielectric portion.

Toner adhesion is as follows. First, the developer carrier 20 that has completed development rotates in the direction of the arrow and comes into contact with the toner supply member 40 . The remaining toner in the non-image area that has not been developed is mechanically and electrically scraped off by the toner supply member 40, and the dielectric portion is charged by friction. At this time, the charges on the developer carrier 20 and the toner due to the previous development are made constant and initialized by friction. Next, the toner carried by the supply member 40 is charged by friction and electrostatically adheres to the dielectric portion of the developer carrier 20 . At this time, the polarity of the toner is opposite to the charge on the photoreceptor, and the dielectric portion of the developer carrier 20 is of the same polarity. The electric field on the developer carrier 20 at this time becomes a microfield (closed electric field) as shown in FIG. 2, and becomes an electric field with a large electric field gradient, making it possible to adhere the toner in multiple layers. Furthermore, since the adhered toner is in a closed electric field, it is strongly attracted to the developer carrier 20 side and becomes difficult to separate.

The thickness of this toner layer is further controlled by a toner layer thickness regulating member 30, and the toner layer reaches the development area 80. The developer carrier 20 and the electrostatic latent image carrier (
The electric field between the photoconductors 10 has a large electrode effect, and the toner on the developer carrier 20 easily adheres to the electrostatic latent image carrier 10, thereby performing development.

Although many types of developing device parts can be used, Table 1 shows the preferred materials based on their releasability with toner and durability.

[0031]

Next, the method for producing the developer carrier used in the present invention will be explained. For example, the following method is adopted. (i) First, a metal roller whose surface is grooved is manufactured. As the groove processing method, a method such as fleur-de-lis knurling is used. The grooves have a pitch of 0.1 to 0.5 mm and are formed at an angle of about 45 degrees with respect to the longitudinal direction of the roller. [See FIG. 3(a)] (ii) Next, the grooved metal surface is coated with, for example, a fluororesin (Lumiflon LF200; manufactured by Asahi Glass Co., Ltd.), and cured and dried at 100° C. for about 30 minutes. The coating thickness should be such that the grooves are completely filled. [See FIG. 3(b)] (iii) Next, the surface of the roller is cut or polished so that the conductive surface is mixed in a small area, and the conductive area is reduced to 20 to 50%. [
See; Figure 3(c)]

[0033] In addition to the above-mentioned method, the conductive rubber material having recesses on its surface may be formed by molding, and the recesses may be filled with an insulating material and polished. be able to.

[0034]

[Examples] The present invention will be explained in more detail with reference to Examples below. Note that parts represent parts by weight.

Example 1 Binder resin Styrene/acrylic copolymer 95 parts
Mold release agent Low molecular weight polypropylene

Part 5 Colorant Carbon black

Part 5 Charge control agent Salicylic acid derivative zinc salt
4th part

The mixture having the above composition was melt-kneaded using a hot roll mill, cooled, and then coarsely ground using a hammer mill, and then finely ground using an air jet type pulverizer. The obtained finely pulverized product was classified to have an average particle size of 11 μm. For 100 parts of this particle, Si
A toner was obtained by adding and mixing 0.5 part of O2 fine powder. The dielectric constant of this toner was 2.73.

Next, a developing roller [FIG. 3(a)] having a cross section as shown in FIG. 3(c) (a dielectric portion and a conductive portion are mixed in a minute area, and the size of the area is 100 μm) A developing device as shown in FIG. 1 equipped with a micro-area (with a microscopic area of 100% and an area ratio of 50%) was prepared, and the toner was loaded into the developing device.

Subsequently, when the developing roller and the photoreceptor were rotated at a constant speed to perform reversal development, a clear image with high image density and no background stains or fog was obtained. [The charged part of the photoreceptor is -800 (V), the exposed part is -100
(V), and toner is developed in the exposed area. ]Furthermore,
Even under high temperature and high humidity conditions, images with no abnormalities were obtained. Furthermore, the images after 3,000 consecutive prints were no different from the initial images.

Comparative Example A toner was produced in the same manner as in Example 1, except that 15 parts of carbon black as a colorant was added. The dielectric constant of the obtained toner was 4.07.
Met.

When an image was produced using the obtained toner in the same manner as in Example 1, the image density was low and density unevenness was observed in some places.

Example 2 Binder resin Styrene/acrylic copolymer 95 parts
Mold release agent Low molecular weight polypropylene

Part 5 Coloring agent Phthalocyanine blue
Part 5 Charge control agent Salicylic acid derivative zinc salt
5th part

A mixture having the above composition was treated in the same manner as in Example 1 to obtain particles with an average particle size of 11 μm. 0.5 parts of TiO2 fine powder per 100 parts of this particle
A toner was obtained by adding and mixing a portion. The dielectric constant of this toner is 2
．． It was 74.

When an image was produced using the obtained toner in the same manner as in Example 1, a clear image with high image density and no background stain or fog was obtained. Furthermore, images without abnormalities were obtained even under high temperature and high humidity conditions. Furthermore, the images after 3,000 consecutive prints were no different from the initial images.

[0044]

Effects of the Invention In the image forming method of the present invention, since the toner is composed of a binder resin and a colorant and has a dielectric constant of 4.0 or less, the surface of the developer carrier is In a development method that creates many small closed electric fields in the vicinity, two or more layers of toner can be stably and uniformly stacked on the developer carrier, resulting in high-density, high-quality images that can be obtained over a long period of time. .

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view centered on a developer carrier portion showing an example of a developing device that forms a microfield electric field on a developer carrier useful for carrying out the present invention.

2 is a schematic cross-sectional view for explaining a state in which a closed electric field is generated by a microfield on a developer carrier in the apparatus shown in FIG. 1; FIG.

3A to 3C are schematic cross-sectional views showing the surface state of a developer carrier used in the developing device of the type shown in FIG. 1 during the manufacturing process.

[Explanation of symbols]

10 Electrostatic latent image carrier 20 Toner conveyance member 30 Toner layer thickness regulating member 40 Toner supply member 50 Stirring blade 60 Toner 70 Toner tank 80 Development area

Claims (1)

[Claims] Claim 1: By selectively retaining charges on the surface of the developer carrier, a large number of minute closed electric fields are formed near the surface of the developer carrier, and as required, Accordingly, a one-component developer consisting of a toner externally added with an adjuvant is supplied, the developer is carried on the surface of the developer carrier by the minute closed electric field, and the electrostatic latent image is made visible by the carried developer. In the image forming method, as a toner,
An image forming method comprising using a binder resin and a colorant having a dielectric constant of 4.0 or less.