JPH04284462A - Image forming method - Google Patents

Abstract

PURPOSE:To obtain an image of high density and high quality by stably and uniformly laminating above two layer of a toner on a developer carrying member and by developing an electrostatic latent image. CONSTITUTION:Many micro-closed electrical field are formed in the vicinity of the surface of the carrying member by selectively holding a charge on the surface of the developer carrying member and an one component developer is supplied on the carrying member by the micro-closed electric field on the carrying member and deposited on the surface of the carrying member by the micro-closed electrical field and the electrostatic latent image on the latent image carrying member is made to the visible image by the developer. In this case, the developer contains phthalocyanine compound as negative polar control agent.

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 powdered developers, two-component developers containing toner and a carrier, and one-component developers that do not contain a carrier are known. The former two-component development method using a two-component developer can produce relatively stable and good recorded images, but on the other hand, it is prone to carrier deterioration and fluctuations in the toner and carrier mixing ratio, making it difficult to maintain and manage the equipment. However, this method has the disadvantage that it is complicated and the structure of the entire device tends to increase in size.

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. JP-A-58-132768), an electrode roller having an insulating surface and a conductive surface (JP-A-53-36245), and the like have been 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 documents, 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.

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, In this case, 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, resulting in low density in the image area. The toner layer may become non-uniform, resulting in uneven development or fogging.Furthermore, a filming phenomenon often occurs on the developer carrier, reducing the microfield effect and hindering development. It has been found that the amount of toner retained on the agent carrier decreases, causing problems such as difficulty in sufficiently developing toner onto the latent image carrier.

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-mentioned image forming method, and to form a film of toner on the developer carrier. An object of the present invention is to provide an image forming method that can control printing and obtain high-density, high-quality images over a long period of time.

[0017]

[Means for Solving the Problems] The image forming method of the present invention creates a minute closed electric field near the surface of the developing roller by selectively retaining electric charge on the surface of the developing roller, and the developer is carried on the developing roller. A one-component developer consisting of a toner containing at least a binder resin, a coloring agent, and a phthalocyanine compound as a charge control agent (negative polarity control agent), and optionally supplemented with an auxiliary agent, is placed on the body. supplying the developer to the surface of the developer carrier by the minute closed electric field;
The electrostatic latent image on the latent image carrier is visualized by the developer carried thereon.

[0018] The method of the present invention will be explained in more detail below. In the developing method of the present invention that forms a minute closed electric field (micro field), the toner layer on the developing roller is always stabilized by having two or more layers. In order to prevent the toner layer from becoming thinner, resulting in uneven development and fogging, a toner that always has stable charging characteristics is required. Therefore, it is effective to use the above-mentioned phthalocyanine compounds as the charge control agent (negative polarity control agent) used in the present invention.

Specific examples of this include (1) Phthalocyanine: C.I. I. Pigment Blue 16 C32H
18N8 (514)

[Chemical formula 1] (2) Magnesium phthalocyanine C32H16N
8Mg (536.3) (3) Chromium phthalocyanine C32H16N8Cr
(564) (4) Iron phthalocyanine C32H16N8Fe (567
．． 8) (5) Nickel phthalocyanine C32H16N8N
i (570.7) (6) Copper phthalocyanine: C.I. I. pigment blue 1
5 C32H16N8Cu (575.5) (7) Zinc phthalocyanine C32H16N8Zn (577.4
) (8) Gallium phthalocyanine C32H16N8C
lGa (617.2) (9) Lead phthalocyanine C32H16N8Pb (7
19.2) (10) Hexadecahydrophthalocyanine C32H
34N8 (530) (11) Hexadecahydromagnesium phthalocyanine C32H32N8Mg (552.3) (12) Hexadecahydronickel phthalocyanine C32H32
N8Ni (586.7) (13) Hexadecahydrocobalt phthalocyanine
C32H32N8Co (586.9) (14) Hexadecahydrocopper phthalocyanine C32
H32N8Cu (591.5) (15) Tetraphenylphthalocyanine C56H34N8 (818) (16
) Tetraphenylmanganese phthalocyanine C56H
32N8Mn (870.9) (17) Tetraphenylcobalt phthalocyanine C
56H32N8Co (874.9) (18) Tetraphenylpalladium phthalocyanine
C56H32N8Pd (922.4) (19) Tetraphenyltin phthalocyanine C56
H32N8Sn (934.7) (20) Tetraphenyl lead phthalocyanine C56H
32N8Pb (1023.2) (21) Tetrakis-t-butylphthalocyanine C
48H50N8(738) (22) Phthalocyanine [(SO3Na)4]: C.I. I
．． Acid Blue 249C32H18N8O12S4 (
834.4) (23) Mononitro copper phthalocyanine (24) Nitro copper phthalocyanine (25) Monocarboxy copper phthalocyanine (26) Dicarboxy copper phthalocyanine (27) Tricarboxy copper phthalocyanine (28) Tetracarboxy copper phthalocyanine (29) 2-carboxy -5-Nitrobenzamidomethyl copper phthalocyanine (30) 2-carboxybenzamidomethyl copper phthalocyanine (31) 4-carboxyphthalimidomethyl copper phthalocyanine (32) β-type copper phthalocyanine (33) α-type copper phthalocyanine (34) Monochloro copper phthalocyanine (35) ) Tetrachlorocopper phthalocyanine (36) Sulfonated copper phthalocyanine (37) Polychlorocopper phthalocyanine (38)

[Case 2] (39)

[Chemical formula 3] (40)

[C4] etc.

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.

[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, and trisazo dyes and pigments.

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 and fat 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, additives other than the above-mentioned binder resin, colorant, auxiliary agent, etc. can also be mixed into the toner of the present invention, if necessary. Examples of such additives include fluidizing agents such as colloidal silica, titanium oxide, and aluminum oxide.

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.

[0025] This image forming method 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. Figure 1
, the toner 6 contained in the toner tank 70
0 is a toner supply member (sponge roller, fur brush, etc.) 4 by a stirring blade (toner supply auxiliary member) 50.
0, the toner 60 is forcibly brought to the toner supply member 4
0. On the other hand, the developer carrier (
The developing roller) 20 rotates in the direction of the arrow (for example, 400
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 a toner layer thickness regulating member (elastic blade) 30.
The charging is stabilized while the thickness is controlled, and the developing area 80
reach. In the development area 80, the latent image is developed by contact or non-contact development. Here, if necessary, a bias voltage such as direct current, alternating current, direct current superimposed alternating current, pulse, etc. is applied to the developer carrier 20 and the toner supply member 40.
Optimal images can be controlled.

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. The size of the area is
If the shape is circular, the diameter is 30 to 2000 μm
, preferably 100 to 400 μm in size, are dispersed 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 micro field (closed electric field) as shown in FIG.
This creates an electric field with a large electric field gradient, making it possible to adhere toner in multiple layers. In addition, since the attached toner is in a closed electric field, it is strongly attracted to the developer carrier 20 side.
It becomes difficult to leave.

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. In the electric field between the developer carrier 20 and the electrostatic latent image carrier (photoreceptor) 10 in the development area 80, the electrode effect increases,
The toner on the developer carrier 20 forms an electric field that easily adheres to the electrostatic latent image carrier 10, and development is performed.

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

[0030]

[Table 1]

Next, the method for producing the developer carrier used in the present invention will be explained. For example, the following method is employed. (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 a silicone resin and cured and dried. The coating thickness should be such that the grooves are completely filled. [See; Figure 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 20 to 5.
Cut it down to 0%. [See; Figure 3(c)]

003
2] In addition to the above-mentioned methods, various methods can be used to create the conductive rubber material using various materials, such as molding a conductive rubber material with recesses on its surface, filling the recesses with an insulating material, and polishing. Can be done.

However, in this development method in which a large number of minute closed electric fields (microfields) are formed near the surface of the developer carrier, the toner layer on the developer carrier must always be stabilized by having two or more layers. The toner layer becomes thinner, the amount of toner developed decreases, and the density of the image area becomes low, and the toner layer becomes uneven, resulting in uneven development and the density of the image area becomes uneven. or fog may occur. Additionally, when a filming phenomenon occurs on the developer carrier, filming is formed on the developer carrier, reducing the microfield effect.
The amount of toner held on the developer carrier decreases, making it difficult to sufficiently develop toner onto the latent image carrier.

However, when a toner containing a negative charge control agent made of the above-mentioned phthalocyanine compound is used, pulverization of the toner on the developer carrier is suppressed;
As a result, filming on the developer carrier is suppressed, so a sufficient microfield effect is exhibited, and the method of the present invention makes it possible to obtain high-density, high-quality images over a long period of time.

[0035]

[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

8 parts Charge control agent (1)
) compound
Two parts of the mixture having the above composition were melt-kneaded, cooled, and 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 about 11 μm. A negatively chargeable toner was obtained by adding and mixing 0.2 parts of colloidal silica to 100 parts of the present particles.

Next, a developing roller [FIG. 3(a)] having a cross section as shown in FIG. 3(c) (a dielectric portion and a conductive portion of epoxy-modified silicone resin are mixed in a minute area,
A developing device (with an area ratio of 50%)
A partially modified developing section of Ricoh FT4200 was prepared, the toner was installed in the developing device, and an image was produced (a selenium-based photoreceptor was used, +800 V
(Development was carried out by applying a charging potential of ), and a clear image with high image density and no background stain was obtained. Furthermore, 5 consecutive
Even after running 000 sheets, no toner was filmed on the developing roller, and a clear image was maintained.

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

Part 5 Colorant Carbon black

8 parts Charge control agent (2)
) compound
Two parts of the mixture having the above composition were melt-kneaded, cooled, and 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 about 12 μm. A negatively chargeable toner was obtained by adding and mixing 0.3 parts of titanium oxide to 100 parts of the present particles. Next, when an image was produced in the same manner as in Example 1, similar results were obtained.

Example 3 Binder resin Styrene/acrylic copolymer 95 parts
Mold release agent Low molecular weight polypropylene

Part 5 Colorant Carbon black

8 parts Charge control agent (6)
) compound
Three parts of the mixture having the above composition were melt-kneaded, cooled, and coarsely ground using a hammer mill, and then finely ground using an air jet type pulverizer. The resulting finely pulverized product was classified to have an average particle size of about 11 μm. A negatively chargeable toner was obtained by adding and mixing 0.2 parts of colloidal silica to 100 parts of the present particles. Next, Example 1
When I created an image in the same manner as above, I obtained similar results.

Example 4 Binder resin Styrene/acrylic copolymer 95 parts
Mold release agent Low molecular weight polypropylene

Part 5 Colorant Carbon black

8 parts Charge control agent (2)
9) Compound
Three parts of the mixture having the above composition were melt-kneaded, cooled, and 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 about 12 μm. A negatively chargeable toner was obtained by adding and mixing 0.3 parts of titanium oxide to 100 parts of the present particles. Next, when an image was produced in the same manner as in Example 1, similar results were obtained.

Example 5 Binder resin Styrene-acrylic polymer 95 parts Mold release agent Low molecular weight polypropylene
Part 5 Colorant Carbon black
8 parts Charge control agent Compound (35) above
Three parts of the mixture having the above composition were melt-kneaded, cooled, and coarsely ground using a hammer mill, and then finely ground using an air jet type pulverizer. The resulting finely pulverized product was classified to have an average particle size of 11 μm. A negatively chargeable toner was obtained by adding and mixing 0.2 parts of colloidal silica to 100 parts of the present particles. Next, when an image was produced in the same manner as in Example 1, similar results were obtained.

Example 6 Binder resin Styrene-acrylic copolymer 95 parts
Mold release agent Low molecular weight polypropylene
Part 5 Colorant Carbon black
8 parts Charge control agent Compound of the above (38)
Three parts of the mixture having the above composition were melt-kneaded, cooled, and 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 about 12 μm. A negatively chargeable toner was obtained by adding and mixing 0.3 parts of titanium oxide to 100 parts of the present particles. Next, when an image was produced in the same manner as in Example 1, similar results were obtained.

Example 7 Binder resin Styrene-acrylic copolymer 95 parts
Mold release agent Low molecular weight polypropylene
Part 5 Colorant Carbon black
8 parts Charge control agent Compound of the above (39)
Three parts of the mixture having the above composition were melt-kneaded, cooled, and coarsely ground using a hammer mill, and then finely ground using an air jet type pulverizer. The resulting finely pulverized product was classified to have an average particle size of about 11 μm. A negatively chargeable toner was obtained by adding and mixing 0.2 parts of colloidal silica to 100 parts of the present particles. Next, when an image was produced in the same manner as in Example 1, similar results were obtained.

Example 8 Binder resin Styrene-acrylic copolymer 95 parts
Mold release agent Low molecular weight polypropylene
Part 5 Colorant Carbon black
8 parts Charge control agent Compound of the above (40)
Three parts of the mixture having the above composition were melt-kneaded, cooled, and 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 about 12 μm. A negatively chargeable toner was obtained by adding and mixing 0.3 parts of titanium oxide to 100 parts of the present particles. Next, when an image was produced in the same manner as in Example 1, similar results were obtained.

Comparative Example A comparative toner was prepared in the same manner as in Example 1 except that no charge control agent was added, and an image was produced in the same manner as in Example 1. , a high-density image was not obtained, and some background staining was observed.

[0046]

According to the image forming method of the present invention, two or more layers of toner can be stably and uniformly laminated on a developer carrier, and toner filming on the developer carrier can be suppressed. High-density, high-quality images 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 holding charges on the surface of the developing roller, a minute closed electric field is formed near the surface of the developing roller, and at least a binder resin and a colorant are formed on the developer carrier. A one-component developer consisting of a toner containing a phthalocyanine compound as a charge control agent and externally added with an auxiliary agent if necessary is supplied, and the developer is transferred to the surface of the developer carrier by the minute closed electric field. An image forming method characterized in that an electrostatic latent image on a latent image carrier is visualized by the developer carried on the latent image carrier.