JPH1020546A - toner - Google Patents

Abstract

(57) [Problem] To provide a toner capable of suppressing generation of agglomerates by stirring in a developing machine and obtaining a high-quality image for a long period of time. SOLUTION: By selectively holding electric charges on the surface of a developing roller, a large number of minute closed electric fields are formed in the vicinity of the developing roller, and a non-magnetic one-component developer is supplied onto the developing roller. A toner for use in an image forming method in which the developer is carried on the surface of a developing roller by the micro-closed electric field, and an electrostatic latent image is visualized by the carried developer. Fine particles having a volume average particle size of 0.05 μm or less and resin fine particles having a volume average particle size of 0.1 to 2.0 μm are externally added as adjuvants. The absolute value of Q / M to be measured is 2 to 30 μc / g.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a latent image bearing member for supplying a non-magnetic one-component developer to a rotationally driven developing roller and carrying the developer on the surface of the developing roller. And a developing roller in which the electrostatic latent image formed on the latent image carrier is visualized by the developer carried on the developing roller in a developing region where the developing roller is opposed to the developing roller. Things.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electronic copying machine, a printer or a facsimile, which forms an electrostatic latent image on a latent image carrier and visualizes the electrostatic latent image with a developer to obtain a recorded image, a powdery image is formed. Dry developing apparatuses using the above-mentioned developer are 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. The agent provides relatively stable and good recorded images, but tends to cause deterioration of the carrier and fluctuation of the mixing ratio of the toner and the carrier, which makes the maintenance and management of the apparatus 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 toner obtained by externally adding an auxiliary agent as needed and mixing the toner and the auxiliary agent. 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 a magnetic material is generally opaque, if a color image including full-color or multi-color is formed with a magnetic toner, a 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 a color image. By the way, in a developing device employing a one-component developing method, a one-component developer is carried on a developing roller and conveyed. In a developing region where the developing roller and the latent image carrier face each other, the latent image carrier is The electrostatic latent image formed on the surface 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 is conveyed to the developing area, and the toner is It is necessary to visualize the latent image by using.

In the case where a magnetic toner is used, the one-component developer can be carried on the developing roller by utilizing the magnetic force of a magnet provided in the developing roller. Is possible. However, when a non-magnetic one-component developer is used, it cannot be carried on the developing roller by magnetic force, so that it is difficult to satisfy the above-mentioned requirements. Various countermeasures against this have been conventionally proposed. For example, Japanese Patent Application Laid-Open No. Sho 61-42672 discloses a method in which a layer of a dielectric (recording material) is formed on the surface of a developing roller. A developer supply member composed of a non-magnetic toner having a polarity opposite to that of the dielectric material, and a non-magnetic toner charged to a polarity opposite to that of the dielectric material is electrostatically attached to the dielectric material. There has been proposed a method of transporting an agent to a developing 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.

Further, between the developing roller and the developer supply member,
A configuration for applying an electric field in a direction in which the non-magnetic toner electrostatically moves to the developing roller side is also known. However, even if such a configuration is added, it is not possible to attach a sufficient amount of toner to the developing roller. difficult. Further, as the toner supply member, 10
^{2 ~10 6 Ω} · cm conductive foam (JP 60-229
057), an elastic body with a skin layer (JP-A-60-22)
No. 9060) and fur brush (JP-A-61-42).
No. 672) and the like, and as a developing roller, a metal body having irregularities on the surface (JP-A-60-53977), an insulating-coated roller body (JP-A-55-46768). Japanese Patent Application Laid-Open No. SHO 53-36245), a medium-resistance coated roller (JP-A-58-13278), and an electrode roller having an insulator and a conductive surface (JP-A-53-36245).

On the other hand, in a developing apparatus using a non-magnetic one-component developer, a sponge roller is disclosed in Japanese Patent Application Laid-Open No. 60-229957, an elastic roller is used in Japanese Patent Application Laid-Open No. 62-229060, and a developing device is disclosed in Japanese Patent Application Laid-Open No. 61-52663. Using a fur brush or the like, a charge is applied to the toner by frictional charging between the toner and the replenishing member, and the toner is electrostatically attached to the developing roller by friction in contact with the developing roller. The latent image on the photoconductor is developed by controlling the toner layer using the layer thickness regulating member. 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 method disclosed in these documents, toner is adhered to the developing roller by friction between the toner replenishing member and the developing roller. Is difficult to obtain, resulting in insufficient toner adhesion. When comparing the color toner with the black toner, in order to obtain the required density, the black toner has an adhesion amount of about 0.4 to 0.5 mg / cm ² , whereas the color toner has 1.5-
Twice the amount of adhesion is required. The need for a large amount of this adhesion also makes non-magnetic one-component development difficult.
Further, as shown in JP-A-54-51841, the one-component developer on the developing roller after passing through the developing area is scraped off, and the surface layer of the developing roller is corona-deposited. A technique has been proposed in which a discharge is performed to impart a charge, and then a non-magnetic toner is positively and electrostatically adhered to a developing roller by a developer supply member. The amount of developer carried on the surface cannot be increased, and a large amount of developer cannot be transported to the development area.

As a method for solving these problems, the present inventors have previously described a one-component developer comprising a non-magnetic toner in which an auxiliary agent is externally added to a rotationally driven developing roller. Is supplied, and the developer is carried on the surface of the developing roller and conveyed. The electrostatic latent image formed on the latent image carrier is developed in a developing area where the latent image carrier and the developing roller face each other. In the developing method of visualizing the image with the developer carried on the developing roller, a plurality of minute closed electric fields are formed in the vicinity of the developing roller surface by selectively holding electric charges on the surface of the developing roller body. Then, the charged toner is sucked by the closed electric field, the developer is adhered to the surface of the developing roller and carried, and an electrostatic latent image is visualized by the carried developer.

According to this invention, since a large number of minute closed electric fields (microfields) are formed near the surface of the developing roller, the intensity of the electric field can be remarkably increased as compared with the prior art, and a large amount of a sufficiently charged non-electric field can be obtained. It has many advantages such that the magnetic toner can be carried on the developing roller and transported to the developing area. However, according to the subsequent study by the present inventors, in a developing method for forming such a minute closed electric field (microfield), when a conventionally known toner is directly used, stirring in a developing machine is performed. It has been found that aggregates increase, causing a decrease in the density of the image portion when copying a large number of sheets, an uneven toner layer to cause image unevenness, and fogging.

Further, the applicant of the present invention can stably and uniformly laminate two or more layers on a developing roller, suppress filming on the developing roller, and provide a high-density, high-quality image for a long period of time. What can be achieved is that “containing at least a binder resin and a colorant, and having a volume resistivity of 10.2 to 11.8 (log Ωcm), and an absolute value of Q / M of the toner by a suction method on a developing roller. A large number of minute closed electric fields are formed in the vicinity of the surface of the developing roller by selectively holding electric charges on the surface of the developing roller, which is 2 to 30, preferably 5 to 20 (μc / g). Then, on this developing roller, if necessary, provide a non-magnetic one-component developer composed of a toner externally added with an auxiliary agent, and carry the developer on the developing roller surface by the minute closed electric field, "A toner used in an image forming method for visualizing an electrostatic latent image using the carried developer" has been proposed (Japanese Patent Application Laid-Open No. H4-240659). According to this toner, the above-described effects can be obtained, but further improvement is required in terms of reduction in ID (image density) based on deterioration of the toner due to long-term image output.

[0011]

SUMMARY OF THE INVENTION The present invention has been made on the basis of the above-mentioned technical background. Can give you a quality image,
Therefore, by selectively holding electric charges on the surface of the developing roller, a large number of minute closed electric fields are formed in the vicinity of the surface of the developing roller. An object of the present invention is to provide a toner which can be suitably used in an image forming method in which the developer is carried on the surface of a developing roller by a closed electric field and the electrostatic latent image is visualized by the carried developer.

The present inventors have conducted intensive studies and as a result, have found that they contain a binder resin and a colorant, and have a volume average particle size of 0.0
Inorganic fine powder of 5 μm or less and volume average particle size of 0.1 to 2.
The present invention was completed by finding that a toner in which the charge relationship between the toner and the resin fine particles was defined by adding externally fine resin particles of 0 μm was suitable for the above purpose.

That is, according to the present invention, by selectively holding electric charges on the surface of the developing roller, a large number of minute closed electric fields are formed in the vicinity of the developing roller. A toner for use in an image forming method for supplying a system developer, causing the developer to be carried on the surface of a developing roller by the minute closed electric field, and visualizing an electrostatic latent image with the carried developer. Contains at least a binder resin and a colorant, and has a volume average particle size of 0.05 μ as an auxiliary agent.
m or less inorganic fine powder and a volume average particle size of 0.1 to 2.0 μm
m is externally added, and the absolute value of Q / M measured by a suction method on the developing roller of the toner is 2 to 30.
μc / g, preferably 5 to 20 μc / g. Here, the Q / M of the resin particles externally added is 200 to 400 μc / g,
It is preferably from 250 to 350 μc / g, and more preferably has the same charging polarity as the toner. Also,
The aggregation degree of this toner is 2 to 20%, preferably 5 to 20%.
~ 15%.

[0014]

According to the study of the present inventors, an inorganic fine powder and a resin fine particle are added as an auxiliary agent to a toner and the relationship between the toner and the resin fine particle is defined to stir the inside of the developing machine. Prevents the embedding of inorganic fine powder on the toner surface that may occur at the same time, suppresses the increase of toner aggregates, enables uniform and stable development of toner particles, and reduces the decrease in density in the image area when copying many sheets. It was found that

[0015] Q / measured by blow-off method of resin fine particles
If the absolute value of M is less than 200 μc / g, the electrical adhesion to the toner will be small, and the resin fine particles will be separated from the toner surface by stirring in the developing machine, and the increase of aggregates cannot be suppressed. On the other hand, if the value is more than 400 μc / g, the charge is too high, so that the aggregates of the resin fine particles themselves are generated and white spots or the like are generated on the image. If the Q / M measured by the blow-off method of the fine resin particles is not the same polarity as the Q / M of the toner, the dispersion of the fine resin particles in the toner is poor. Further, it also affects the Q / M measured by the suction method on the developing roller, and causes problems on the image such as image unevenness and white spots.

The toner of the present invention is used in a copying machine, a facsimile or a printer equipped with the above-described developing process, and has a Q / M of less than 2 μc / g as measured by a suction method on a toner developing roller. In this case, dust and the like are generated. On the other hand, when the density is larger than 30 μc / g, image unevenness, white spots and the like occur.

Furthermore, the addition of the fine resin particles must not adversely affect the degree of aggregation of the toner. If the agglomeration degree of the toner is smaller than 2, the toner scatters in the image machine, and if it is larger than 20, the replenishing property to the developing roller is reduced, and the density is reduced due to the reduced flying property.

The toner of the present invention is externally added with an auxiliary of inorganic fine powder and resin fine particles for the purpose of improving fluidity. As the inorganic fine powder, for example, Si whose surface is hydrophobized
Examples include inorganic oxides such as O ₂ and TiO ₂ , inorganic fine particles of SiC, and metal soap of zinc stearate. Examples of the resin fine particles include a copolymer of a substantially spherical alkyl acrylate or alkyl methacrylate and a styrene monomer.

The binder resin used in the toner of the present invention comprises:
All of those that have been used as binders for toners can be applied. Specifically, styrene such as polystyrene, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-butadiene copolymer, etc. Starting with resin, saturated polyester resin, unsaturated polyester resin, epoxy resin,
Examples thereof include a phenol resin, a maleic acid resin, a cumaronic acid resin, a chlorinated paraffin, a xylene resin, a vinyl chloride resin, polypropylene, and polyethylene. It goes without saying that two or more of these binder resins may be used as a mixture as appropriate. Among these, the use of polystyrene, styrene resin and epoxy resin is advantageous.

The toner of the present invention contains a colorant. As the colorant used in the toner of the present invention, all pigments and dyes conventionally used as colorants for toner are applied. Specifically, carbon black, lamp black, iron black, ultramarine, 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,
Examples include quinacridone, benzidine yellow, malachite green, malachite green hexalate, oil black, azo oil black, rose bengal, monoazo dyes, disazo dyes, trisazo dyes and mixtures thereof.

The toner of the present invention may contain a charge control agent and a release agent, if necessary. As the charge control agent, there are nigrosine dyes, quaternary ammonium salts, basic dyes, amino acid-containing polymers and the like for imparting positive polarity to the toner, and chromium-containing monoazo dyes for imparting negative polarity. Chlorinated organic dyes, metal salts of salicylic acid derivatives, and the like.

Examples of the release agent include synthetic waxes such as low molecular weight polyethylene and polypropylene, and vegetable waxes such as candelilla wax, carnauba wax, rice wax, wood wax and hoboba oil; beeswax, lanolin, Animal waxes such as whale wax; mineral waxes such as montan wax and ozokerite; hydrogenated castor oil, hydroxystearic acid, fatty acid amide,
Fatty waxes such as phenol fatty acid esters are exemplified.

In addition to the above components, the toner of the present invention may contain various plasticizers (dibutyl phthalate, phthalate, etc.) for the purpose of adjusting the thermal, electrical and physical properties of the toner as required.
It is also possible to add an auxiliary agent such as dioctyl phthalate or the like, a resistance adjusting agent (such as tin oxide, lead oxide or antimony oxide).

The toner of the present invention forms a large number of minute electric fields close to the surface of the developing roller by selectively retaining electric charges on the surface of the developing roller. A non-magnetic one-component developer composed of a toner externally added with an auxiliary agent is supplied, and the developer is carried on the surface of the developing roller by the minute electric field, and the electrostatic latent image is visualized by the carried developer. This is useful in an image forming method that performs

Next, the image forming method will be described. FIG. 1 shows an outline of a typical developing device useful for carrying out this image forming method, focusing on a developing roller portion. FIG.
In the above, the toner 60 of the present invention contained in the toner tank 70 is forcibly brought to the toner supply member (such as a sponge roller or a fur brush) 40 by the stirring blade (toner supply auxiliary member) 50, and the toner 60 is It is supplied to the supply member 40. On the other hand, the developing roller 20 that has completed the development rotates in the direction of the arrow (for example, 400 rpm).
Then, it reaches a contact portion with the toner supply member (sponge roller) 40. The toner supply member 40 rotates in a direction opposite to that of the developing roller 20 (for example, at 300 rpm), charges the developing roller 20 and the toner 60, and places the toner 60 on the developing roller 20.
To adhere. Further, the developing roller 20 rotates, and the toner adhered on the developing roller 20 is stabilized by the toner layer thickness regulating member (elastic blade) 30 while controlling the thickness, and reaches the developing region 80. In the development area 80, the latent image is developed by contact or non-contact development. Here, if necessary, a bias such as direct current, alternating current, direct current superimposed alternating current, or pulse can be applied to the developing roller 20 and the toner supply member 40 to control an optimum image.

Next, the mechanism of toner adhesion to the developing roller 20 of this type (electrode type) will be described. As an example of the developing roller 20, for example, as shown in FIG. 3, the surface of the developing roller 20 is configured such that a dielectric portion and a conductor portion are mixed in a very small area. As for the size of the area, assuming that the shape is a circle, a small area having a diameter of 10 to 500 μm is dispersed randomly or according to a certain rule. As the area ratio, the area of the insulating part is 20 to 60.
% Is preferred.

The toner adhesion is as follows. First, the developing roller 20 that has completed the development rotates in the direction of the arrow and comes into contact with the toner supply member 40. Here, the remaining toner in the non-image portion 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 charge of the developing roller 20 and the toner by the previous development is fixed by friction and initialized. Next, the toner carried by the supply member 40 is charged by friction and adheres to the dielectric portion of the developing roller 20 electrostatically. At this time, the polarity of the toner is opposite to that of the photoconductor charge, and the dielectric portion of the developing roller 20 has the same polarity.
At this time, the electric field on the developing roller 20 becomes a microfield (closed electric field) as shown in FIG. 2 and becomes an electric field having a large electric field gradient, so that the toner can be adhered in multiple layers. Further, since the attached toner has a closed electric field, it is strongly pulled toward the developing roller 20 and is hard to be separated. This toner layer further includes a toner layer thickness regulating member 3.
The toner layer thickness is controlled by 0, and the toner in the developing area 80 becomes an electric field which easily adheres to the photoreceptor, and the development is performed.

Although many kinds of parts can be used for the developing device, Table 1 shows only materials that are preferable from the viewpoint of releasability from toner and durability.

[0029]

[Table 1]

In order to produce a developing roller having a surface in which a dielectric portion and a conductor portion are mixed in a small area, for example, first, a groove is formed on the surface by iris red processing or the like. A metal roller is manufactured (in this case, grooves are formed at a pitch of 0.1 to 0.5 mm, and are processed at an angle of about 45 ° with respect to the longitudinal direction of the roller) [see FIG.
(A)] Then, 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 applied thickness is such that the grooves are completely filled). (See FIG. 3)
(B)] Subsequently, the surface of the roller is cut or polished so that the conductive surfaces are mixed in a small area, and the conductive area is reduced to 20 to 60% [see FIG. 3 (c)].
Is adopted.

In the developing method in which a microfield electric field is formed on the developing roller, when a conventionally known toner is employed as it is, agglomerates increase due to agitation in the developing machine, and the image area at the time of copying many sheets is increased. May occur, or the toner layer may become non-uniform, resulting in image unevenness or fogging. When the toner of the present invention is used, an increase in aggregates due to agitation in the developing machine is suppressed, so that a high-density and high-quality image can be obtained even when copying a large number of sheets.

[0032]

The present invention will be described in more detail with reference to the following examples. Parts represent parts by weight, and the average particle size is represented by a volume average particle size measured by a scanning electron microscope.

In the present invention, the measurement of the toner Q / M by the suction method on the developing roller was performed as follows. The toner adhering to the developing roller is sucked through a Faraday cage (not shown) having a filter layer on the outlet side, and Q / M is calculated based on the weight and charge amount of the toner trapped in the Faraday cage. In addition, Q /
M is an amorphous reduced iron powder TEFV-200 / 300 (manufactured by Nippon Iron Powder), and a sample obtained by mixing with a ball mill at a ratio of 0.5 part of resin particles to 100 parts of iron powder and triboelectrically charging is generally used. Blow-off method manufactured by Toshiba Chemical Corporation: T
It measured by B-200.

In the present invention, the measurement of the degree of aggregation was as follows. Use the Hosokawa Micron powder tester to set accessories on the shaking table according to the following procedure. (A) Bipro chute (B) Packing (C) Space ring (D) Screen (3 types) Top>Middle> Bottom (E) Osae bar Next, fix with the knob nut and operate the shaking table. The measurement conditions are as follows. The sieve opening is (upper) 150 μm The sieve opening is (middle) 75 μm The sieve opening is (lower) 45 μm Amplitude scale 1 mm Sampling amount 10 g Vibration time 30 seconds After measurement, the cohesion degree is determined from the following calculation. The sum of the above three calculated values is defined as the degree of aggregation (%).

Example 1 Binder resin Styrene-acrylic copolymer 95 parts Release agent Low molecular weight polypropylene 5 parts Colorant carbon black 10 parts Charge control agent Salicylic acid derivative zinc salt 4 parts The mixture having the above composition was melt-kneaded. The powder was ground using a hammer mill and then finely ground by an air jet method.
The obtained finely pulverized particles were classified to have an average particle size of 11 μm.
The following composition was mixed with 100 parts of the particles to obtain Toner 1 of the present invention. Inorganic fine powder Silica fine powder 0.7 part Resin fine particles Styrene-methacrylic acid copolymer 1.0 part The Q / M of the resin fine particles is -330 [mu] c / g.

Example 2 Binder resin Polyester resin 95 parts Release agent Carnauba wax 5 parts Coloring agent Metal-containing azo dye 10 parts Charge control agent Salicylic acid derivative zinc salt 4 parts Inorganic fine powder Silica fine powder 1.0 part Resin Using 1.0 part of fine particles of polymethyl methacrylate, processing was carried out by the method shown in Example 1 to obtain an average particle diameter of 9.0.
μm of the toner 2 of the present invention was obtained. The Q of the resin fine particles
/ M is -250 μc / g.

Example 3 Binder resin Polyester resin 95 parts Release agent Carnauba wax 5 parts Coloring agent Nigrosine 10 parts Charge control agent Quaternary ammonium salt, 4 parts (Orient Chemical Industries, Bontron P-51) Inorganic Fine powder Silica fine powder 1.0 part Resin fine particles Polymethyl methacrylate 1.0 part was processed by the method shown in Example 1, and the average particle diameter was 9.0.
μm of the toner 3 of the present invention was obtained. The Q of the resin fine particles
/ M is +350 μc / g.

Comparative Example 1 A comparative toner 1 was prepared in the same manner as in Example 1 except that carbon black was changed from 10 parts to 3 parts as a coloring agent, and a salicylic acid derivative zinc salt was changed from 4 parts to 10 parts as a charge controlling agent. I got

Comparative Example 2 10 to 20 parts of carbon black as a coloring agent, and 4 parts to 0.1 part of a zinc salt of a salicylic acid derivative as a charge controlling agent.
A trial production was performed in the same manner as in Example 1 except that the amount was changed to 5 parts, and Comparative Toner 2 was obtained.

Comparative Example 3 A comparative toner 3 was obtained in the same manner as in Example 1, except that the Q / M of the resin fine particles was changed to -450 μc / g.

Comparative Example 4 A comparative toner 4 was obtained by trial production in the same manner as in Example 1 except that the Q / M of the resin fine particles was -120 μc / g.

Comparative Example 5 A comparative toner 5 was obtained in the same manner as in Example 1, except that the Q / M of the fine resin particles was +350 μc / g.

COMPARATIVE EXAMPLE 6 From 1.0 part to 2.5 parts of fine silica powder as inorganic fine particles.
Part, polymethyl methacrylate 1.0 as resin fine particles
A trial production was performed in the same manner as in Example 1 except that the styrene-methacrylic acid copolymer was changed from 0.5 part to 0.5 part, respectively, to obtain Comparative Toner 6.

Comparative Example 7 As fine inorganic particles, silica fine powder was added in an amount of 1.0 part to 0.1 part.
Comparative toner 7 was obtained in the same manner as in Example 1, except that the styrene-methacrylic acid copolymer was changed to 2.0 parts as the resin fine particles.

A developing device provided with a developing roller having a cross section as shown in FIG. 3 was prepared, and ten kinds of toner samples (toners 1 to 3 of the present invention) obtained by the above-described method were installed in the developing device.
Each of the comparative toners 1 to 7) was mounted, and an image was formed. Table 2 shows the results. Further, with the toner of the present invention, a clear image having a high image density and no fog was obtained, and the image density did not decrease even after 4000 copies.

[0046]

[Table 2]

[0047]

The toner of the present invention suppresses the generation of agglomerates by stirring in the developing machine, and can provide an image having a stable image density even when copying a large number of sheets.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an example of a developing device in which a microfield electric field is formed on a developing roller useful for carrying out the present invention, focusing on a developing roller unit.

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

FIGS. 3A, 3B, and 3C are schematic cross-sectional views showing surface states in a process of manufacturing a developing roller used in a developing device of the type shown in FIG.

[Explanation of symbols]

 Reference Signs List 10 electrostatic latent image carrier 20 toner transport member 30 toner layer thickness regulating member 40 toner supply member 50 stirring blade 60 toner 70 toner tank 80 development area

Claims (4)

[Claims] An electric charge is selectively held on the surface of a developing roller to form a large number of minute closed electric fields in the vicinity of the developing roller, and a non-magnetic one-component developer is supplied onto the developing roller. A toner that is used in an image forming method in which the developer is carried on the surface of a developing roller by the minute closed electric field, and an electrostatic latent image is visualized by the carried developer, wherein the toner is at least a binder resin. An inorganic fine powder having a volume average particle size of 0.05 μm or less and a resin fine particle having a volume average particle size of 0.1 to 2.0 μm are externally added as a supplement, containing a colorant. A toner having an absolute value of Q / M measured from 2 to 30 μc / g. 2. An absolute value of Q / M of a resin fine particle used as an external additive to the toner by a blow-off method is 200.
2. The toner according to claim 1, wherein the toner concentration is from 400 to 400 [mu] c / g. 3. The toner according to claim 1, wherein Q / M of resin fine particles used as an external additive in the toner measured by a blow-off method has the same polarity as the toner. 4. The toner according to claim 1, wherein the value of the degree of aggregation of the toner is 2 to 20%.