JP3255482B2 - Toner for developing electrostatic latent images - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to electrophotography, electrostatic recording,
More specifically, the present invention relates to a toner used in an image forming method for developing an electrostatic latent image in electrostatic printing or the like. The present invention relates to a toner used in a developing method in which a toner is carried thereon with a thickness smaller than the above-mentioned interval, and the carried toner is caused to fly to an electrostatic latent image on an electrostatic latent image holding member and developed.

[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 holding member and visualizes the latent image with a developer to obtain a recorded image, a powdery image is formed. Dry developing devices using a developer are widely used.

As such a powdery developer, a two-component developer having a toner and a carrier and a one-component developer not containing a carrier are known, and the former two-component developer is used. In the two-component developing method, a relatively stable and good recorded image can be obtained, but the deterioration of the carrier and the fluctuation of the mixing ratio of the toner and the carrier are apt to occur, the maintenance of the apparatus is complicated, and the structure of the entire apparatus is large. It has a disadvantage that it is easy to change. Therefore, a one-component developing method using a one-component developer which does not have such a drawback has attracted attention. One-component developers include those composed of toner only and those to which an auxiliary agent is externally added as necessary.

In recent years, there has been an increasing demand for multi-color copying machines and printers such as two-color, multi-color and full-color printers, especially for copying machines and printers that are compact and inexpensive. As one means for reducing the size of the apparatus, superposition development of a multicolor toner on a latent image holding member (photoreceptor) has been proposed.

In the superposition development on the latent image holding member, a multi-color toner image is formed on the latent image holding member, so that the toner does not directly contact the toner image on the latent image holding member. The holder and the toner carrier are arranged at a fixed interval, the toner is carried on the toner carrier to a thickness smaller than the interval, and the carried toner flies to the electrostatic latent image on the latent image carrier. Development method (hereinafter referred to as non-contact development)
Is preferred. This contact development is described in JP-B-41-94.
No. 75, however, in order for toner to fly to an electrostatic latent image, toner particles must be reliably charged to a desired polarity individually, particles must be easily separated, and static The ability to fly easily in accordance with the electric field is an important condition for obtaining good image quality.

[0006] In order to achieve these conditions, an attempt has been made as a developing method to improve the flying property of the toner by applying an alternating electric field between the toner carrier and the electrostatic latent image. Further, as a toner suitable for non-contact development, a toner using silica as an external additive for toner (Japanese Patent Publication No. 63-42783).
Japanese Patent Application Laid-Open No. 60-87343 / 60-8734.
No. 7, each publication), and those in which the particle size distribution of toner is specified (JP-A-62-103675) are proposed.

[0007]

However, although these toners also have a local effect on the developing property, it is hard to say that the toner flying property is considered. Furthermore, in non-contact development, as in conventional contact development,
Even if a high-concentration copy image is obtained with unused toner, if toner agitation continues in the in-machine developing device such as long-term running, the fluidity of the toner itself deteriorates, and the electrostatic latent image holding member is removed from the toner carrier. It is known that the toner flies very poorly, leading to a decrease in image density and image deterioration.

Accordingly, the present invention has been made based on the above-mentioned technical background, and a developing method for developing a toner by causing toner on a toner carrier to fly onto an electrostatic latent image on an electrostatic latent image holder. It is an object of the present invention to provide a low-deterioration toner capable of providing a high-density, high-quality image for a long time.

[0009]

Means for Solving the Problems The present inventors have made intensive studies and found that the flying performance of a toner to an electrostatic latent image in non-contact development is greatly affected by the adhesion between toners. Thus, the present invention has been completed.

That is, according to the present invention, a latent image holding member for holding an electrostatic latent image on the surface thereof and a toner carrier are disposed opposite to each other with a certain gap provided in a developing section, and toner is transferred to the toner carrier. A toner having a thickness smaller than the gap, and a toner used in an image forming method for developing the toner by flying the toner on the surface of the latent image holding member in a developing unit, wherein the fixing resin and the colorant are used. It is composed of base particles as main components and an external additive, and has an adhesion of 10 g / cm due to vertical tensile fracture after applying a load of 1 kg / cm ^{2 to} the toner.
^A toner for developing an electrostatic latent image is provided, wherein the number is ² or less.

Originally, a van der Waals force, a liquid bridging force, and the like strongly act between toner particles used in electrophotography. Therefore, at the time of actual use, a fluidity improver is added to the toner surface to reduce the interparticle force. Measures have been taken to mitigate this. However, by adding a fluidity improver to the toner,
Although the flying property of the toner to the latent image holding member is certainly improved, it is still insufficient to obtain a high-density, high-quality image. This is because the adhesive force between the toner particles on the toner carrier is not sufficiently reduced, and the adhesive force between the toner particles is larger than the electric field from the toner carrier to the electrostatic latent image. That is, if the adhesion force between the toners is large, the flying of the toner is suppressed, and the image density is reduced. In other words, if the toner has a small adhesive force between the toners, an image having a sufficient density can be obtained. In the present invention, the adhesion between the toners is regarded as a force required for the vertical tensile break, and the adhesion between the toners is defined, whereby the flying property of the toner to the electrostatic latent image is sufficiently improved.

The present inventors have obtained the present invention by using the breaking stress per unit area of a packed bed in which powder is pressed as the adhesive force between particles, that is, the strength of a particle aggregate. More specifically, the powder is filled in the two-divided cell shown in FIG.
Pressurize at Kg / cm ² . By fixing the lower cell and pulling the upper cell in the direction of compaction of the packed bed and measuring the stress F when the powder layer breaks, the adhesive force between the powders is obtained. Force).

In the toner of the present invention, 1 K
It is characterized in that the toner has a powder vertical tensile breaking force of 10 g / cm ² or less after a load of g / cm ² is applied.
When the vertical tensile breaking force is 10 g / cm ² or less, the electric field force of the electrostatic latent image becomes sufficiently large as compared with the adhesion force between the toner particles, and a sufficient amount of toner flies from the toner carrier, resulting in high density. Image can be obtained.

Incidentally, the toner generally used for electrophotography is deteriorated when used for a long time, and the image density and the image quality are lowered. This causes a stress of agitation in the developing machine due to long-term use, external additives distributed on the toner surface are buried in the toner, and the toners easily come into contact with each other,
This is because the adhesive force between the toners increases. In this case, since the toner base particles are exposed on the surface, the adhesive force of the base particles greatly affects the deterioration of the toner for a long time. That is, by using a toner having a small adhesive force of the toner base, there is a great effect on image density and image quality deterioration over long-term use. In particular, when the powder vertical tensile breaking force of the toner matrix is 15 g / cm ² or less, sufficient image density and image quality can be ensured even when the toner is used for a long period of time, which is very preferable. That is, when mechanical energy is applied to the toner,
Even when the externally added fluidity imparting agent is buried in the toner, the adhesive force between the toners is kept small, and the toner becomes high-density, high-quality toner with little image deterioration even for long-term running and storage.

[0015] The toner of the present invention comprises base particles mainly composed of a fixing resin and a colorant, and an external additive. As the fixing resin used in the present invention, all of those which have been used as a binder resin for a toner can be applied. Specifically, homopolymers of styrene such as polystyrene, polychlorostyrene, and polyvinyltoluene and substituted products thereof;
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 Coalesce, styrene / butyl methacrylate copolymer,
Styrene / α-chloromethyl methacrylate copolymer, styrene / acrylonitrile copolymer, styrene / vinyl methyl ether copolymer, styrene / vinyl methyl ketone copolymer, styrene / butadiene copolymer, styrene / isoprene copolymer , Styrene / acrylonitrile /
Styrene copolymers such as indene copolymer, styrene / maleic acid copolymer, styrene / maleic acid ester copolymer; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester , Polyvinyl butyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenol resin and the like.

However, since 80% to 95% of the main component of the toner is a resin, the selection of the adhesive force of the fixing resin greatly affects the adhesive force of the toner. That is, the smaller the adhesive force of the fixing resin itself, the smaller the adhesive force of the toner matrix,
This greatly affects the developability of the toner. Specifically, as the adhesive force of the resin, a powder vertical tensile breaking force measured as particles obtained by pulverizing a resin powder to a size of 15 μm or less is 15 g / c.
It is preferable to use a resin having an m ² or less. In particular, by using a styrene / butyl acrylate copolymer,
Adhesive force can be significantly reduced. If the amount of the styrene / butyl acrylate copolymer is at least 30% by weight, the effect of lowering the powder vertical tensile rupture strength of the toner is obtained.
When the content is 30% by weight or less, the effect of the resin used in combination with the powder vertical tensile breaking force increases, and the toner developability decreases.

The toner of the present invention preferably contains a release agent. In this case, as the release agent to be used, all of those which have been used as a release agent for toner can be used, but in addition to synthetic waxes such as low molecular weight polyethylene and polypropylene, candelilla wax, carna Uba wax, rice wax, wood wax,
Vegetable waxes such as jojoba oil; animal waxes such as beeswax, lanolin, and spermaceti; montan wax;
Mineral waxes such as ozokerite; hardened castor oil,
Fatty waxes such as hydroxystearic acid, fatty acid amide, phenol fatty acid ester and the like can be mentioned.

However, the release agent in the toner tends to be unevenly distributed on the toner surface, and greatly contributes to the toner adhesion. That is, the smaller the adhesive force of the release agent itself, the smaller the adhesive force of the toner matrix, which greatly affects the toner developability. Specifically, as the adhesive force of the release agent, the one having a powder vertical tensile breaking force of 25 g / cm ² or less measured as particles obtained by crushing the release agent powder to a size of 15 μm or less is used. preferable.

As the colorant used in the toner of the present invention, all of conventionally used pigments and dyes are applied. Specifically, ultramarine, nigrosine dye, aniline blue, calco oil blue, Dupont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, phthalocyanine green, rhodamine 6C lake, quinacridone, benzidine yellow, malachite green, hansa yellow G, malachite Examples include green hexalate, oil black, azo oil black, rose bengal, monoazo dyes and pigments, disazo dyes and pigments, and trisazo dyes and pigments.

In the toner of the present invention, it is effective to add a charge controlling agent to control the polarity. Examples of the charge control agent in this case include nigrosine, quaternary ammonium salts, metal-containing azo dyes, and complex compounds of salicylic acid.

In the toner of the present invention, the external additive (fluidity imparting agent) to be added and mixed is, for example, a lubricant such as Teflon or zinc stearate, or a polishing agent such as cerium oxide or silicon carbide; Examples include a conductivity-imparting agent such as carbon black and tin oxide, a fixing aid such as low-molecular-weight polyolefin and wax, and, for example, colloidal silica, aluminum oxide, and titanium oxide. The amount of addition is 0.1% by weight to 1% based on the toner.
0% by weight, preferably 0.2% to 5% by weight.

The average particle diameter of the toner of the present invention is 7 μm.
When the particle size is from m to 13 μ, it is possible to ensure the flying property of the toner. When the average particle size is smaller than 7 μm,
Adhesive force between toner particles, particularly liquid bridging force between the particles is increased, so that detachment of the toner from the toner carrier is suppressed, and flying to the electrostatic latent image is suppressed. On the other hand, when it is larger than 13 μm, the image clarity deteriorates (image blur and bleeding occur).

The toner of the present invention is effectively applied to a non-contact developing system, in which a high-density, high-quality image is formed for a long period of time. This toner is applied to all of the non-contact development methods. Hereinafter, a number of minute closed electric fields are formed near the surface of the toner carrier, and the toner carried on the toner carrier is transferred onto the latent image holder. A case where the present invention is applied to an image forming method of flying will be described in detail.

FIG. 2 shows an outline of a typical developing device useful for carrying out the image forming method, focusing on the toner carrier. In FIG. 2, the toner 60 of the present invention contained in the toner tank 70 is forcibly brought to a toner supply member (such as a sponge roller or a fur brush) 40 by a stirring blade (toner supply unit auxiliary member) 50 and 6
0 is supplied to the toner supply member 40. On the other hand, the toner carrier (developing roller) 20 that has completed the development rotates in the direction of the arrow, and the toner supply member (sponge roller) 40
To the contact area. The toner supply member 40 rotates in the opposite direction to the toner carrier 20, and the toner carrier 20 and the toner 60 are rotated.
Is charged to cause the toner 60 to adhere to the toner carrier 20. Further, the toner carrier 20 rotates, and the toner adhered on the toner carrier 20 is stabilized in thickness while being controlled by the toner layer thickness regulating member (elastic blade) 30, and reaches the developing area 80. In the development area 80, the latent image is developed by non-contact development. Here, a DC voltage or the like is applied to the toner carrier 20 and the toner supply member 40, and an electric field is applied in a direction to hold the toner 60 on the toner carrier 20, thereby causing the toner to fly to portions other than the electrostatic latent image portion. And an optimal image can be controlled.

Next, the mechanism of toner adhesion to the toner carrier 20 of this type (electrode type) will be described. As an example of the toner carrier 20, for example, as shown in FIG. 3, a derivative portion and a conductive pair portion are mixed in a very small area on the surface thereof. The size of the area is
When the shape is circular, the diameter is 30 to 2000 μ
m, preferably small areas with a size of 100 to 400 μm, are dispersed randomly or according to certain regulations. As the area ratio, the area of the insulating portion is preferably in the range of 50 to 80%.

The toner adhesion is as follows. First, the toner carrier 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 toner carrier 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 toner carrier 20 electrostatically. At this time, the polarity of the toner is opposite to the charge of the photosensitive member, and the dielectric portion of the toner carrier 20 has the same polarity. At this time, the electric field on the toner carrier 20 becomes a microfield (closed electric field) as shown in FIG. 3, 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, the attached toner is strongly pulled toward the toner carrier 20 and is hardly separated.

The thickness of the toner layer is further controlled by the toner layer thickness regulating member 30, and reaches the developing zone 80. Toner carrier 20 and latent image carrier 10 in developing area 80
The toner on the toner carrier 20 flies to the surface of the latent image carrier 10 due to the electric field therebetween, and development is performed.

In order to prepare a toner carrier having a surface in which a derivative portion and a conductor portion are mixed in a small area, for example, first, a metal having a groove formed on the surface by iris knurling or the like is used. Prepare a roller, coat the grooved metal surface with, for example, fluororesin, cure and dry, then cut or polish the roller surface so that the conductive surface is mixed in a small area, and the conductive part area is Grind to 20% to 50%.

Needless to say, instead of the above-described toner carrier, a metal member subjected to a sandblast treatment or a metal member coated with a resin in a thin layer can be used.

The toner of the present invention is also used in a developing method in which a regulating member is provided by two-component magnetic brush development to perform non-contact development.

[0031]

The present invention will be described in more detail with reference to the following examples. Parts represent parts by weight.

Example 1 Fixing resin 86 parts of styrene / butyl methacrylate copolymer (Tg = 63 ° C.) Release agent Paraffin wax 3 parts Colorant carbon black 7 parts Charge control agent Zinc salicylate 4 parts

The mixture having the above composition was melt-kneaded, cooled, coarsely pulverized using a hammer mill, and then finely pulverized with an air jet type pulverizer. The obtained finely pulverized product was classified to obtain a toner base having an average particle size of 11 μm. Further, 1.5 parts of hydrophobic silica (HDK-2000 manufactured by Hoechst) was added to and mixed with 100 parts of the toner base to obtain a toner.

Next, the powder vertical tensile breaking force of the obtained toner was measured. The measurement was made by Shimadzu powder adhesion measuring device ED-2.
000H type was used. That is, 10 g of the above-mentioned toner is filled in a two-part cell having a cross-sectional area of 10 cm ² ,
g was applied under a constant pressure for 5 minutes to prepare a measurement sample, and the lower cell was fixed and the upper cell was pulled in the compaction direction of the packed layer using a powder adhesion measuring device manufactured by Shimadzu Corporation. When the stress F was measured, it was 9.5 g / cm ² . The powder vertical tensile rupture strength of the toner matrix was measured in the same manner, and was found to be 25 g / cm ² .

Further, with respect to the fixing resin and the releasing agent used in Example 1, the powder vertical tensile breaking force was measured. That is, first, the fixing resin was finely pulverized by a fine pulverizer using an air jet method. The obtained finely pulverized product was classified to obtain a fine resin powder having an average particle size of 11 μm. When the vertical tensile strength at break of the powder of the obtained resin fine powder was measured in the same manner as described above, it was 8.2 g / cm ² . Further, also for the release agent, when the powder vertical tensile breaking force was measured in the same manner as in the fixing resin, it was 27.1 / cm ² .

Example 2 Fixing resin Styrene / butyl methacrylate / 91 parts Ethylhexyl acrylate copolymer Coloring agent Carbon black 6 parts Charge control agent Zinc salicylate 3 parts

The mixture having the above composition was melt-kneaded, cooled, coarsely pulverized using a hammer mill, and then finely pulverized by a pulverizer using an air jet method. The obtained finely pulverized product was classified to obtain a toner base having an average particle size of 11 μm. Further, 1.3 parts of hydrophobic silica (HDK-2000 manufactured by Hoechst) was added to and mixed with 100 parts of the toner base to obtain a toner of Example 2. With respect to the obtained toner, the powder vertical tensile breaking force was measured in the same manner as in Example 1. Table 1 shows the results.

Example 3 Fixing resin Styrene / methyl acrylate copolymer 88 parts (Tg = 59 ° C.) Colorant carbon black 7 parts Charge control agent Zinc salicylate 5 parts

The mixture having the above composition was melt-kneaded, cooled, coarsely pulverized using a hammer mill, and then finely pulverized with a fine pulverizer using an air jet method. The obtained finely pulverized product was classified to obtain a toner base having an average particle size of 11 μm. Further, 1 part of hydrophobic silica (HDK-2000 manufactured by Hoechst) was added to and mixed with 100 parts of the toner base to obtain a toner of Example 3. Example 1 of the obtained toner
The powder vertical tensile breaking strength was measured in the same manner as described above. Table 1 shows the results.

Example 4 Fixing resin 84 parts of styrene / butyl acrylate copolymer (Tg = 62 ° C.) Release agent Low molecular weight polypropylene 5 parts Colorant carbon black 8 parts Charge control agent Zinc salicylate 3 parts

The mixture having the above composition was melt-kneaded, cooled, coarsely pulverized using a hammer mill, and then finely pulverized by an air jet type pulverizer. The obtained finely pulverized product was classified to obtain a toner base having an average particle size of 11 μm. Further, 1 part of hydrophobic silica (HDK-2000 manufactured by Hoechst) was added to and mixed with 100 parts of the toner base to obtain a toner of Example 4. Example 1 of the obtained toner
The powder vertical tensile breaking strength was measured in the same manner as described above. Table 1 shows the results.

Example 5 Fixing resin 87 parts of styrene / butyl methacrylate copolymer (Tg = 61 ° C.) Release agent Low molecular weight polypropylene 4 parts Coloring agent Copper phthalocyanine 5 parts Charge control agent 4 parts of zinc salicylate

The mixture having the above composition was melt-kneaded, cooled, coarsely pulverized using a hammer mill, and then finely pulverized by an air jet type pulverizer. The obtained finely pulverized product was classified to obtain a toner base having an average particle size of 13 μm. Further, 0.8 part of hydrophobic silica (HDK-2000 manufactured by Hoechst) was added to and mixed with 100 parts of the toner base to obtain a toner of Example 5. With respect to the obtained toner, the powder vertical tensile breaking force was measured in the same manner as in Example 1. Table 1 shows the results.

Example 6 Fixing resin 1 Styrene / butyl methacrylate copolymer 44 parts (Tg = 61 ° C.) Fixing resin 2 Polyester resin 44 parts (Tg = 61 ° C.) Release agent Carnauba wax 3 parts Colorant Pigment Red 5 parts Charge control agent zinc salicylate 4 parts

The mixture having the above composition was melt-kneaded, cooled, coarsely pulverized by using a hammer mill, and then finely pulverized by an air jet type pulverizer. The obtained finely pulverized product was classified to obtain a toner base having an average particle size of 9 μm. Further, 0.5 part of hydrophobic silica (HDK-2000 manufactured by Hoechst) was added to and mixed with 100 parts of the toner base to obtain a toner of Example 6. With respect to the obtained toner, the powder vertical tensile breaking force was measured in the same manner as in Example 1. Table 1 shows the results.

Example 7 Fixing resin 82 parts of styrene / butyl acrylate copolymer (Tg = 63.5 ° C.) Release agent Paraffin wax 6 parts Colorant carbon black 9 parts Charge control agent Zinc salicylate 8 parts

The mixture having the above composition was melt-kneaded, cooled, coarsely pulverized by using a hammer mill, and then finely pulverized by an air jet type pulverizer. The obtained finely pulverized product was classified to obtain a toner base having an average particle size of 11 μm. Further, 0.8 part of hydrophobic silica (HDK-2000 manufactured by Hoechst) was added to and mixed with 100 parts of the toner base to obtain a toner of Example 7. With respect to the obtained toner, the powder vertical tensile breaking force was measured in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 1 Fixing resin Polyester resin (Tg = 61 ° C.) 88 parts Release agent Paraffin wax 4 parts Colorant carbon black 9 parts Charge control agent Zinc salicylate 4 parts

The mixture having the above composition was melt-kneaded, cooled, coarsely pulverized by using a hammer mill, and then finely pulverized by an air jet type pulverizer. The obtained finely pulverized product was classified to obtain a toner base having an average particle size of 11 μm. Further, 1 part of hydrophobic silica (HDK-2000 manufactured by Hoechst) was added to and mixed with 100 parts of the toner base.
Was obtained. With respect to the obtained toner, the powder vertical tensile breaking force was measured in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 2 Fixing resin 1 Styrene / butyl acrylate copolymer 20 parts (Tg = 62 ° C.) Fixing resin 2 Polyester resin 72 parts (Tg = 61 ° C.) Coloring agent Copper phthalocyanine 5 parts Charge control agent Zinc salicylate 3 Department

The mixture having the above composition was melt-kneaded, cooled, coarsely pulverized by using a hammer mill, and then finely pulverized by an air jet type pulverizer. The obtained finely pulverized product was classified to obtain a toner base having an average particle size of 11 μm. Further, 0.8 part of hydrophobic silica (HDK-2000 manufactured by Hoechst) was added to and mixed with 100 parts of the toner base to obtain a toner of Comparative Example 2. With respect to the obtained toner, the powder vertical tensile breaking force was measured in the same manner as in Example 1. Table 1 shows the results.

[0052]

[Table 1]

(Evaluation) As shown in FIG. 3, a developing device provided with a toner carrier having a surface in which a dielectric portion and a conductor portion are mixed in a very small area on a surface and their area ratio is 50% was prepared. The above-described Examples 1 to 7 and Comparative Example 1
Each of the toners obtained in Steps (1) to (2) is attached, and a copying machine F manufactured by Ricoh Co., Ltd.
Image output was performed using T4450. Further, running was performed continuously for 2,000 sheets, and measurement of image output was performed again. The image density of the obtained image was measured with a Macbeth densitometer, and the deviation of a 1 mm thin line was visually observed.
It was evaluated on a scale (5 ... good, 1 ... poor). Table 2 shows the results. In addition, the fixability is a result of evaluating the dirt on the fixing roller after running the above 2,000 sheets on a scale of five levels.

[0054]

[Table 2]

[0055]

The toner for developing an electrostatic latent image according to the present invention comprises base particles mainly composed of a fixing resin and a colorant, and an external additive, and after applying a load of 1 kg / cm ^{2 to} the toner. Since the adhesive force due to vertical tensile rupture was 10 g / cm ² or less, the present invention relates to a developing method in which the toner on the toner carrier is caused to fly to the electrostatic latent image on the electrostatic latent image holder and developed. When the toner of the present invention is applied, the electric field force of the electrostatic latent image becomes sufficiently large compared with the adhesion force between the toner particles, a sufficient amount of toner flies from the toner carrier, and a high-density, high-quality image can be formed for a long period of time. Obtainable.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a powder adhesion measuring device used for measuring a powder vertical tensile breaking force of a toner or the like in the present invention.

FIG. 2 is a schematic view centering on a developer carrying portion showing an example of a developing device useful for performing an image forming method using a toner of the present invention.

FIG. 3 is a schematic diagram 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;

[Explanation of symbols]

 Reference Signs List 10 latent image holding member (photoreceptor) 20 toner carrying member 30 toner layer thickness regulating member (elastic blade) 40 toner supplying member (sponge roller) 50 stirring blade 60 toner 70 toner tank 80 developing area

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Satoshi Hasegawa 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) References JP-A-5-19529 (JP, A) JP-A Heisei JP-A-4-318560 (JP, A) JP-A-4-337738 (JP, A) JP-A-4-9863 (JP, A) JP-A-4-44054 (JP, A) JP-A-59-198470 (JP, A) A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 9/08

Claims (1)

(57) [Claims] 1. A developing device comprising: a latent image holding member for holding an electrostatic latent image on a surface thereof and a toner carrier; A toner used in an image forming method in which the toner is carried to a small thickness, and the carried toner is caused to fly on the surface of the latent image holding member in a developing unit to develop the toner, wherein the base particles mainly include a fixing resin and a colorant. And an external additive, wherein the toner has an adhesive force of 10 g / cm ² or less due to vertical tensile rupture after applying a load of 1 kg / cm ^{2 to} the toner. .