JPH08190274A - Image forming method using two-component developer - Google Patents

Abstract

PURPOSE: To provide a method to obtain a good copy image with a two- component developer using a small particle toner without splashing a toner. CONSTITUTION: A two-component developer comprising a carrier and a small- size toner having 6-9μm volume average particle size is used. A replenisher toner and the carrier remaining after the toner is removed from the developer in an image forming device are mixed in a ball mill for 15 seconds to obtain the toner density controlled in the image forming device. In this process, the toner is mixed to obtain 7μC/g to 40μC/g absolute charge amt. or 2×10<-9> μC/one particle to 12×10<-9> μC/one particle absolute average charge amt., and then used for image forming (development).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method using a two-component developer in the fields of electrophotography and electrostatic recording.

[0002]

2. Description of the Related Art Conventionally, as disclosed in Japanese Patent Laid-Open No. 61-147261, methods for developing an electrostatic charge image by using toner are roughly classified into a so-called mixture of toner and carrier. A method using a two-component developer,
There is a method of using a one-component developer which is used alone as a toner without being mixed with a carrier.

Of these, the method using a two-component developer is
By stirring and rubbing the toner and the carrier, they are charged to different polarities, and the electrostatically charged image having the opposite polarity is visualized (developed) by the charged toner. Depending on the type of toner and carrier, There are a magnet brush method using an iron powder carrier, a cascade method using a bead carrier, a fur brush method, and the like. As the toner applied to these various developing methods, fine powder in which a colorant such as carbon black is dispersed in a binder resin made of a natural resin or a synthetic resin is used. For example, particles in which a colorant is dispersed in a binder resin such as polystyrene and finely pulverized to about 1 to 30 μm are used as toners. Further, a magnetic toner such as those containing a magnetic material such as magnetite is used as a magnetic toner.

In recent years, due to the demand for higher image quality in the market,
There is a demand for smaller toner particles. By reducing the toner particle size, image sharpness, gradation, graininess, and halftone uniformity are improved, but the side effect is that toner particles easily scatter in copiers and printers. ing. This development becomes remarkable especially when the volume average particle diameter of the toner is 9 μm or less. Further, this problem is caused by controlling the toner concentration in the developer by using a magnetic bridge type toner concentration sensor, reducing the amount of the developer for the purpose of downsizing a copying machine or a printer, At this time, it occurs remarkably when the toner density is set high in order to further improve the followability of the solid density.

It has been reported in JAPAN HARDCOPY '92 Proceedings (P93-96) that toner scattering is defined by the ratio q / d of the charge amount to the particle size. Further, JP-A-6-59507 reports that toner scattering can be prevented by defining the toner particle size, the toner manufacturing method, the hiding ratio of the toner particles on the carrier surface, and the like. However, in reality, the problem is not completely solved by simply defining the charge amount of the developer in the developing unit, and the problem is not solved only by the hiding rate on the carrier surface of the toner.

[0006]

DISCLOSURE OF THE INVENTION The first object of the present invention is to
Image sharpness, gradation, graininess,
An object of the present invention is to provide an image forming method using a two-component developer, which achieves both improvement of halftone uniformity and prevention of toner scattering. A second object of the present invention is to prevent toner scattering that occurs inside an image forming apparatus such as a copying machine or a printer that uses a toner having a small particle diameter, and in particular, to perform toner density control using a magnetic blit type toner sensor. An object of the present invention is to provide an image forming method using a two-component developer that prevents toner scattering in some cases. A third object of the present invention is to prevent the toner from scattering when the toner density is set high or the developer amount is reduced in order to improve the compactness of the machine and the followability of the solid at that time. An object of the present invention is to provide an image forming method using a component type developer.

[0007]

According to the present invention, the following image forming methods (1) to (7) are provided. (1) In an image forming method for developing an electrostatic latent image using a two-component developer composed of a toner and a carrier, a carrier that consumes toner in the development and contains substantially no toner, and a toner to be replenished are The toner concentration is controlled in the image forming apparatus, mixed so that the absolute value of the charge amount when mixed for 15 seconds by a ball mill is 7 μC / g to 40 μC / g, and the volume average particle diameter of the toner is set. To 6 to 9 μm.

(2) In an image forming method for developing an electrostatic latent image by using a two-component type developer consisting of a toner and a carrier, a toner that consumes toner during the developing and does not substantially contain toner, and a toner that is replenished. And are set to toner concentrations controlled in the image forming apparatus, and the absolute value of the average charge amount when mixed for 15 seconds with a ball mill is 2 × 10 ₋₉ μC / unit to 12 × 10 ₋₉ μC / unit An image forming method comprising the steps of:

(3) In an image forming method for developing an electrostatic latent image using a two-component developer comprising a toner and a carrier, a toner that consumes toner during the development and a substantially toner-free carrier and a toner that is replenished And are set to the toner concentration controlled in the image forming apparatus, and the absolute value of the charge amount when mixed for 15 seconds by a ball mill is 7 μC / g to 40 μC /
g, the toner has a volume average particle diameter of 6 to 9 μm, and is mixed such that the relationship between the charging ability of the toner in the developer and the charging ability of the replenishment toner is represented by the following formula (I). Forming method.

## EQU1 ## −10 ≦ QA −QB ≦ 4 (μC / g) (I) (QA: The above-mentioned substantially toner-free carrier and the toner to be replenished are set to control toner concentrations, and a ball mill is used for 15 Absolute value of charge amount after second mixing, QB: Absolute value of charge amount when the carrier containing substantially no toner and the toner in the developer are set to control toner concentrations and mixed for 15 seconds with a ball mill. value.)

(4) An image forming method in which an electrostatic latent image is developed using a two-component developer composed of toner and carrier, and the toner concentration is controlled by measuring the magnetic permeability of the developer with a magnetic bridge type toner sensor. In the above, the charge amount when the carrier that consumes toner in the development and does not substantially contain toner and the toner that is replenished are set to the toner concentration controlled in the image forming apparatus and mixed by a ball mill for 15 seconds And the volume average particle diameter of the toner is adjusted to 6 to 9 μm. The image forming method is characterized in that the toner is mixed so that the absolute value thereof is 10 μC / g to 40 μC / g.

(5) Image formation in which an electrostatic latent image is developed using a two-component developer composed of toner and carrier, and the proportion of toner particles on the carrier surface at a controlled toner concentration is 20% or more. In the method, charging is performed when a carrier that consumes toner in the development and does not substantially contain toner and a toner to be replenished are set to a toner concentration controlled in an image forming apparatus and mixed for 15 seconds by a ball mill. An image forming method, characterized in that the toner is mixed so that the absolute value of the amount is 10 μC / g to 40 μC / g, and the volume average particle diameter of the toner is 6 to 9 μm.

(6) In an image forming method in which an electrostatic latent image is developed using a two-component developer composed of a toner and a carrier and a controlled toner density satisfies the following formula (II), the toner is used in the development. Of the carrier that consumes the toner and does not substantially contain the toner and the toner to be replenished are set to the toner concentrations controlled in the image forming apparatus, and the absolute value of the charge amount when mixed for 15 seconds by a ball mill is 10 μC / g. ~ 40 μC / g
And the volume average particle diameter of the toner is 6 to
An image forming method characterized in that the thickness is 9 μm.

Rc ³ ρc · a / rtρt · (rc + rt) ² · (100−a) ≧ 0.08 (II) (where, rc; carrier particle size, ρc; carrier true specific gravity, rt; toner particle Diameter, ρt; true specific gravity of toner, a; toner concentration (wt%).)

(7) In an image forming method in which an electrostatic latent image is developed using a two-component developer composed of toner and carrier, and the surface area of the carrier in one developing unit of the image forming apparatus is 15 m ² or less, The carrier that consumes toner in the development and does not substantially contain toner and the toner that is replenished are set to the toner concentration controlled in the image forming apparatus, and the absolute amount of charge when mixed for 15 seconds by a ball mill is set. An image forming method, characterized in that the toner is mixed so that the value is 10 μC / g to 40 μC / g, and the volume average particle diameter of the toner is 6 to 9 μm.

As a result of intensive studies on the above-mentioned mechanism of toner scattering, the present inventors have found that there are at least the following two generation patterns. When the carrier in the developer and the toner to be replenished have a low rise in charging and the replenishment toner cannot obtain an appropriate amount of charge in a short time. When the replenishment toner has a higher rise of charge than the toner in the developer, and the toner already in the developer is repelled.

In order to prevent the toner scattering due to the above mechanism, it is necessary to regulate the rising of the charge between the replenishment toner and the carrier in the developer. In the past, there was discussion about the amount of charge on the developer, but with regard to toner scattering, it is important how quickly the uncharged toner becomes charged immediately after the toner is replenished. I knew if there was. Specifically, when the volume average particle diameter of the toner is 6 to 9 μm, the carrier in which the toner is removed from the developer in the image forming apparatus (the toner is consumed by visualizing the electrostatic latent image to substantially consume the toner). Carriers not included) and toner to be replenished are set to toner concentrations controlled in the image forming apparatus, and absolute value of charge amount when mixed for 15 seconds by a ball mill must be 7 μC / g or more. Is. The toner scattering can be regulated by the charge amount of one toner. In this case, the carrier in which the toner has been removed from the developer in the image forming apparatus and the toner to be replenished are set to the toner concentration controlled in the image forming apparatus, and the average charge amount when mixed for 15 seconds with a ball mill is set. The absolute value of is required to be 2 × 10 ₋₉ C / piece or more.

The toner scattering in this pattern occurs remarkably when the toner density is set high or the developer amount is decreased, which is because the surface area of the carrier that the replenished toner particles can occupy for charging. It is thought that it is small. Therefore, it is appropriate to express the toner concentration as the toner particle coverage on the surface of the carrier and the developer amount as the surface area amount of the carrier in the developing unit. As a result of examination, when the charge amount is 10 μC / g or less, the coverage of toner particles on the carrier surface exceeds 20%, and the surface area of the carrier in the developing unit is 15 m ² or less, the toner scattering occurs. Rapidly deteriorated, and not only the toner was scattered inside the machine, but the image appeared as a background stain. Under these process conditions, it is important that the charge amount is 10 μC / g or more.

Here, the coverage rate of the toner particles on the carrier surface may be directly observed with an electron microscope or the like, or may be calculated from the carrier surface area and the toner particle diameter obtained by a BET specific surface area meter. Also, the toner particle coverage on the carrier surface is 2
The condition of 0% or more can be simply represented by the following formula (II).

Rc ³ ρc · a / rtρt · (rc + rt) ² · (100−a) ≧ 0.08 (II) (where, rc; carrier particle size, ρc; carrier true specific gravity, rt; toner particle Diameter, ρt; true specific gravity of toner, a; toner concentration (wt%).)

Further, it has been found that the toner scattering in the above pattern is remarkable when the toner concentration in the developer is controlled by using a magnetic bridge type toner concentration sensor. As is well known, this sensor detects the bulk density of the developer with magnetic permeability. When the toner having a low rising of charging is replenished, a very small amount of toner particles not having a sufficient electric charge enters the developer gap, so that the decrease in the bulk density corresponding to the toner replenishment does not occur. for that reason,
The toner density is slightly higher. When the toner concentration becomes higher, the carrier surface required for charging the toner to be replenished next becomes smaller. Then, among the replenished toners, the toner particles that do not have a sufficient charge and enter the developer gap increase. The toner density becomes higher. By repeating this, the weakly charged toner increases and toner scattering occurs.

On the other hand, in the case of toner scattering by the above-mentioned mechanism, the surface condition of the toner changes due to heat and force in the developing unit or when the initial developer is prepared, and the toner charging ability in the developer is lowered. Or when the charging ability of the replenishment toner is higher than that of the toner in the developer due to variation in the amount of charge between toner lots. In order to prevent toner scattering in this pattern, it is necessary to satisfy the relationship of the following formula (III).

[Formula 3] QA-QB ≤ 4 (μC / g) (III) (where QA is "the carrier from which the toner has been removed from the developer and the toner to be replenished are set to a control toner concentration, and mixed for 15 seconds with a ball mill. QB is the absolute value of the charge amount when the carrier after removing the toner from the developer and the toner in the developer are set to a controlled toner concentration and mixed for 15 seconds with a ball mill. In addition, the absolute value of the charge amount exceeds 40 μC / g, or 12 ×
If it exceeds 10 ₋₉ μC / piece, a problem occurs that a sufficient image density cannot be obtained. Furthermore, the difference between QA and QB is 10μ
If it exceeds C / g, there is a problem that the image quality changes remarkably when the toner is switched.

From the above, in a general use environment,
The absolute value of the charge amount when mixed for 15 seconds with a ball mill is 7μ.
C / g to 40 μC / g and the volume average particle diameter of the toner is 6 to 9 μm, or the absolute value of the average charge amount when mixed for 15 seconds in a ball mill is 2 × 10 ₋₉ μC / piece 12 × 10 ₋₉ μC / piece, and the following formula (I)
It is important to satisfy

[Equation 1] −10 ≦ QA − QB ≦ 4 (μC / g) (I)

Further, when the toner density is set high or the developer amount is decreased, and when the toner density control is a magnetic bridge type toner sensor, the ball mill is used for 15
The absolute value of the charge amount when mixed for 10 seconds is 10 μC / g to 40 μ
C / g is important.

The charge amount described so far is 60 mm in diameter.
50 g of the carrier obtained by removing the toner from the developer in the apparatus and the amount of replenishment toner having the toner density controlled in the image forming apparatus are charged into the ball mill of No. 1 and the ball mill is operated at 10
After rotating at 0 rpm for 15 seconds, the developer consisting of toner and carrier was taken out from the ball mill and measured with a blow-off charge amount measuring device.

In the present invention, the materials used for both the toner and the carrier are not particularly limited, and all known materials can be used. Examples of the binder resin used in the present invention include polymers of styrene and its substitution products such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene; styrene-p-chlorostyrene copolymers, styrene-propylene copolymers. , Styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-
Ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer,
Styrene-methylmethacrylate copolymer, styrene-ethylmethacrylate copolymer, styrene-butylmethacrylate copolymer, styrene-α-chloromethylmethacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinylmethyl Styrene-based copolymers such as ketone copolymers, styrene-butadiene copolymers, styrene-isoprene copolymers, styrene-acrylonitrile-indene copolymers, styrene-maleic acid copolymers, styrene-maleic acid ester copolymers Combined; polymethylmethacrylate, polybutylmethacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene,
Polyester, epoxy resin, epoxy polyol resin, polyurethane, polyamide, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, Paraffin wax and the like can be used, and they can be used alone or in combination.

As the colorant, all known dyes and pigments can be used. For example, carbon black, nigrosine dye, iron black, naphthol yellow S, Hansa yellow (1
0G, 5G, G), cadmium yellow, yellow iron oxide, ocher, yellow lead, titanium yellow, polyazo yellow, oil yellow, Hansa yellow (GR, A, RN, R), pigment yellow L, benzidine yellow ( G, G
R), Permanent Yellow (NCG), Balkan Fast Yellow (5G, R), Tartrazine Lake, Quinoline Yellow Lake, Anthrazan Yellow BGL, Isoindolinone Yellow, Bengala, Reedan, Lead Vermillion, Cadmium Red, Kad Muum Mercury Red, Antimon Zhu, Permanent Red 4R, Para Red, Phi Sae Red, Parachlor Ortho Nitroaniline Red, Resor Fast Scarlet G, Brilliant Fast Scarlet, Brilliant Carnmin BS, Permanent Red (F2R, F4R, FRL, FRL)
L, F4RH), Fast Scarlet VD, Belkan Fast Rubin B, Brilliant Scarlet G, Resor Rubin GX, Permanent Red F5R, Brilliant Carmine 6B, Pigment Scarlet 3B, Bordeaux 5B, Toluisin Maroon, Permanent Bordeaux F.
2K, Helio Bordeaux BL, Bordeaux 10B, Bon Maroon Lights, Bon Maroon Medium, Eosin Lake,
Rhodamine Lake B, Rhodamine Lake Y, Alizarin Lake, Thioindigo Red B, Thioindigo Maroon, Oil Red, Quinacridone Red, Pyrazolone Red, Polyazo Red, Chrome Vermilion, Benzidine Orange, Perinone Orange, Oil Orange, Cobalt Blue, Cerulean Blue. , Alkali Blue Lake, Peacock Blue Lake, Victoria Blue Lake, Metal-Free Phthalocyanine Blue, Phthalocyanine Blue, Fast Sky Blue, Indanthrene Blue (R
S, BC), indigo, ultramarine, navy blue, anthraquinone blue, fast violet B, methyl violet lake, cobalt purple, manganese purple, dioxane violet, anthraquinone violet, chrome green, zinc green, chromium oxide, pyridian, emerald green, pigment green. B, naphthol green B, green gold, acid green lake, malachite green lake, phthalocyanine green, anthraquinone green, titanium oxide, zinc oxide, lithobon and mixtures thereof can be used. The amount used is generally 0.1 to 50 parts by weight with respect to 100 parts by weight of the binder resin.

The toner of the present invention may contain a charge control agent, if necessary. All known charge control agents can be used, for example, nigrosine dyes, triphenylmethane dyes, chromium-containing metal complex dyes, molybdic acid chelate pigments, rhodamine dyes, alkoxy amines, quaternary ammonium salts (fluorine modified (Including quaternary ammonium salts), alkylamides, phosphorus alone or compounds,
Examples include simple substances or compounds of tungsten, fluorine-based activators, salicylic acid metal salts, and salicylic acid derivative metal salts. If desired, a plurality of these charge control agents may be used in combination.

The amount of the charge control agent used in the present invention is determined by the type of binder resin, the presence or absence of additives used as necessary, and the toner production method including the dispersion method, and is uniquely limited. However, it is preferably 0.1 to 1 with respect to 100 parts by weight of the binder resin.
It is used in the range of 0 parts by weight, preferably in the range of 2 to 5 parts by weight. If the amount is less than 0.1 parts by weight, the negative charging of the toner is insufficient, which is not practical. On the other hand, if the amount exceeds 10 parts by weight, the chargeability of the toner is too large, and the electrostatic attraction with the carrier increases, resulting in a decrease in the fluidity of the developer and a decrease in the image density.

Other additives include colloidal silica, hydrophobic silica, fatty acid metal salts (zinc stearate, aluminum stearate, etc.), metal oxides (titanium oxide, aluminum oxide, tin oxide, antimony oxide, etc.). , Fluoropolymer and the like, and an appropriate amount thereof may be contained.

Further, the toner of the present invention may further contain a magnetic material and be used as a magnetic toner. The magnetic material contained in the magnetic toner of the present invention includes magnetite, hematite, iron oxide such as ferrite, metals such as iron, cobalt, nickel, or aluminum of these metals,
Examples thereof include alloys of metals such as cobalt, copper, lead, magnesium, tin, zinc, antimony, beryllium, bismuth, cadmium, calcium, manganese, selenium, titanium, tungsten and vanadium, and mixtures thereof. It is desirable that these ferromagnetic materials have an average particle size of about 0.1 to 2 μm. The amount contained in the toner is about 20 to 200 parts by weight, and particularly preferably 100 parts by weight of resin component to 100 parts by weight of resin component. 40-150 for a part
Parts by weight.

As the carrier used in the present invention, iron powder, ferrite, glass beads and the like are the same as conventional ones.
These carriers may be coated with resin. The resin used in this case is polyfluorocarbon, polyvinyl chloride, polyvinylidene chloride, phenol resin, polyvinyl acetal, silicone resin and the like.

Generally, a suitable mixing ratio of the toner and the carrier is about 0.5 to 6.0 parts by weight of the toner with respect to 100 parts by weight of the carrier.

[0031]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. All parts are parts by weight. First, some production examples of the toner and the carrier according to the present invention will be shown below.

(Toner Production Example 1) Styrene-n-butyl acrylate copolymer (copolymerization ratio 83/17) 90 parts (Mn = 12000, Mw / Mn = 24, Tg = 54 ° C.) carbon black 10 parts Chromium-containing azo Dye (Bontron S34, Orient Chemical Co., Ltd.) 2 parts Polypropylene wax (Sun Wax 660P, Sanyo Kasei Co., Ltd.) 2 parts were mixed with a mixer and then melt-kneaded with a two-roll mill. The kneaded product was rolled and cooled, and then pulverized and classified to obtain four types of toner having a volume average particle diameter of 9.5 μm, 8.5 μm, 7.5 μm and 6.5 μm. Furthermore, hydrophobic silica (R97
2. Made by Nippon Aerosil Co., Ltd.) 0.3 wt%, 0.4 wt%,
5 wt% and 0.6 wt% were added, and mixed toner samples A1 to A4 were obtained with a mixer. The true specific gravity of the toner was 1.3.

(Toner Production Example 2) Styrene-n-butyl acrylate copolymer (copolymerization ratio 83/17) 90 parts (Mn = 12000, Mw / Mn = 24, Tg = 54 ° C.) carbon black 10 parts phenol derivative (Bontron E89, manufactured by Orient Chemical Co., Ltd.) 2 parts Polypropylene wax (Sun Wax 660P, manufactured by Sanyo Chemical Co., Ltd.) 2 parts was mixed with a mixer and then melt-kneaded with a two-roll mill. Toner 4 having a volume average particle size of 9.5 μm, 8.5 μm, 7.5 μm, 6.5 μm
A seed toner was obtained. Furthermore, hydrophobic silica (R972,
Made by Nippon Aerosil Co., Ltd.) 0.3wt%, 0.4wt%, 0.5wt respectively
%, 0.6 wt% added and mixed with a mixer Sample B
1 to B4 were obtained. The true specific gravity of the toner was 1.3.

(Toner Production Example 3) Styrene-n-butyl acrylate copolymer (copolymerization ratio 83/17) 90 parts (Mn = 12000, Mw / Mn = 24, Tg = 54 ° C.) carbon black 10 parts phenol derivative (Bontron E89, manufactured by Orient Chemical Co., Ltd.) 0.5 part Polypropylene wax (Sun Wax 660P, manufactured by Sanyo Chemical Co., Ltd.) 2 parts was mixed with a mixer and then melt-kneaded with a two-roll mill. Toner 4 having a volume average particle size of 9.5 μm, 8.5 μm, 7.5 μm, 6.5 μm
A seed toner was obtained. Furthermore, hydrophobic silica (R972,
Made by Nippon Aerosil Co., Ltd.) 0.3wt%, 0.4wt%, 0.5wt respectively
%, 0.6 wt% was added and mixed with a mixer Sample Toner C
1 to C4 were obtained. The true specific gravity of the toner was 1.3.

(Production Example 1 of carrier) Silicon resin solution (KR50, manufactured by Shin-Etsu Chemical Co., Ltd.) 100 parts Carbon black (manufactured by Cabot, BP2000) 3 parts Toluene 100 parts A mixture was dispersed for 30 minutes with a homomixer to form a coating layer. A forming liquid was prepared. This coating layer forming liquid has an average particle size of 50
A carrier A was obtained in which a coating layer was formed on the surface of 1000 parts of spherical ferrite having a diameter of μm using a fluidized bed type coating apparatus. The true specific gravity of Carrier A was 5.0.

(Production Example 2 of carrier) Silicon resin solution (KR50, manufactured by Shin-Etsu Chemical Co., Ltd.) 100 parts Carbon black (manufactured by Cabot, BP2000) 3 parts Toluene 100 parts A mixture was dispersed for 30 minutes with a homomixer to form a coating layer. A forming liquid was prepared. The coating layer-forming liquid has an average particle size of 80
A carrier B having a coating layer formed on the surface of 1000 parts of spherical ferrite having a diameter of μm by using a fluidized bed type coating apparatus was obtained. The true specific gravity of Carrier B was 5.0.

Example 1 The two-component developer having a toner concentration of 6 wt% was prepared by mixing the toner A3 and the carrier A shown in the production example. This developer was put in an experimental machine in which the developing part of a copying machine (Imagio 320) manufactured by Ricoh Co., Ltd. was improved to cope with a small amount of developer, and the toner for replenishment was evaluated using A3 which was the same as that used for preparing the developer. Here, the amount of developer is 100 g, and the density control in the imager 320 is a method in which a toner pattern is formed on the photoconductor and the density is controlled from the amount of development. The run evaluation results are summarized in Table 1. Here, the toner coverage is calculated from an electron micrograph. Toner scattering in the experimental machine was carried out by visual observation after extracting the developing portion after continuously copying 1000 sheets. In addition, 1000 pieces of background stains were visually observed and judged.
Q / M in Table 1 is the charge amount of the developer at 1000 sheets, QA
Is the absolute value of the charge amount when the toner removed from the developer and the toner to be replenished and the toner to be replenished are set to a controlled toner concentration and mixed for 15 seconds in a ball mill, and QA 'is a value obtained by converting QA per toner. . The toner density is a value calculated by the following formula (IV).

## EQU4 ## rc ³ ρc · a / rtρt · (rc + rt) ² · (100−a) (IV) (rc, pc, rt, pt, and a are the same as the above formula (II)). ) For QB, set the carrier in which the toner is removed from the developer and the toner in the developer to the control toner concentration,
It is the absolute value of the charge amount when mixed for seconds. Here, in particular, the share in the developing section and the share at the time of creating the developer are not applied, and since the toner for creating the developer and the replenishment toner are exactly the same, the toner charging ability QA in the developer and the charge of the replenishment toner are charged. The abilities QB can be considered equal.

Example 2 The toner A3 shown in the manufacturing example and the carrier A were mixed to prepare a two-component developer having a toner concentration of 6 wt%. This developer is put in an experiment machine with a modified development unit of a Ricoh copier (Imagio 320), and the same A as in the preparation of toner developer for replenishment
3 was used for evaluation. Here, the developing section was further improved to control the toner density with a magnetic bridge type toner sensor. As a result, even when 1,000 sheets were passed, no toner scattering occurred in the experimental machine, and no problem occurred even with 10,000 sheets.

Example 3 Toner B3 shown in the production example and carrier A were mixed to prepare a two-component developer having a toner concentration of 6 wt%. This developer was put into an experimental machine in which the developing section of a Ricoh copying machine (Imagio 320) was improved, and the toner for replenishment was evaluated using A2. Here, the developing section was further improved to control the toner density with a magnetic bridge type toner sensor. Even if 1,000 sheets were passed, no toner scattering occurred in the experimental machine, and no problem occurred even after 10,000 sheets. 100
When QA and QB were measured using the developer at the time of passing 0 sheets, QA was 7.8 μC / g and QB was 10.7 μC / g.

Examples 4 to 14 The toner and carrier shown in the production examples were combined and the same evaluation as in Example 1 was performed. Here, in Example 6, the toner concentration was set to 2.5 wt%. Further, in Example 7, the developing portion was changed and the amount of developer was 400 g, and in Example 11, the amount of developer was 400 g and the toner concentration was 2.5 wt%. The results are summarized in Table 1. In Example 11, the toner was good without scattering of toner, but a decrease in the image density in the solid portion was observed during continuous copying.

Comparative Example 1 The toner B3 shown in the production example and the carrier A were mixed to prepare a two-component developer having a toner concentration of 6 wt%. This developer was put in an experiment machine of the copying machine (Imagio 320) manufactured by Ricoh Co., Ltd. with an improved developing part, and the toner for replenishment was evaluated using B3 which was the same as used in the developer preparation. As a result, the toner was scattered when the developing portion was taken out and observed after passing 1000 sheets.

Comparative Example 2 The toner B3 shown in the production example and the carrier A were mixed to prepare a two-component type developer having a toner concentration of 6 wt%. This developer was put in an experiment machine of the copying machine (Imagio 320) manufactured by Ricoh Co., Ltd. with an improved developing part, and the toner for replenishment was evaluated using B3 which was the same as used in the developer preparation. Here, the developing section was further improved to control the toner density with a magnetic bridge type toner sensor. As a result, the toner density did not change significantly after passing 1,000 sheets, but toner scattering was observed in the experimental machine. Also, the toner density is 10w for 10,000 sheets.
It increased to t%, the toner scattering in the experimental machine was very large,
Background stains were also found on the image.

Comparative Example 3 The same developer as in Example 11 was placed in an experimental machine of the copying machine (Imagio 320) manufactured by Ricoh Co., Ltd. with an improved developing section, and the toner for replenishment was evaluated using A2. When the developing portion was taken out and observed after passing 1000 sheets, a large amount of toner scattering was observed. QA and QB were measured using the developer after passing 1000 sheets. QA was 10.8 μC / g and QB was 6.7 μC.
It was / g.

Comparative Example 4 The same developer as in Example 13 was placed in an experimental machine of the copying machine (Imagio 320) manufactured by Ricoh Co., Ltd. with an improved developing section, and the toner for replenishment was evaluated as A2. When the developing portion was taken out and observed after passing 1000 sheets, no toner scattering was observed. The toner for replenishment was changed to C2 and the evaluation was continued. After 1000 sheets were passed after the change, when the developing portion was taken out and observed, almost no toner scattering was observed, but the image gradually became thick and image dust was generated. QA and QB were measured using the developer at that time.
Was 6.7 μC / g and QB was 10.8 μC / g.

Comparative Examples 5 to 10 The same evaluation as in Example 1 was carried out by combining the toner and the carrier shown in the production example. The results are summarized in Table 1.

[0046]

[Table 1- (1)]

[0047]

[Table 1- (2)] (Note) ○ in the column of toner scattering and background stain indicates that they were generated or not observed. In the image grainens, ◯ means good and Δ means normal.

[0048]

According to the present invention, it is possible to prevent toner scattering in an image forming apparatus such as a copying machine or a printer which uses a toner having a volume average particle diameter of 9 μm or less in order to improve image quality. Sharpness and gradation, graininess (graininess), and halftone uniformity can be improved. Furthermore, a sufficient image density can be obtained, and it is possible to prevent a change in image density due to toner replenishment. In particular, it is possible to prevent toner scattering when controlling the toner concentration using the magnetic blit method toner sensor. In addition, the toner concentration is set high in order to reduce the size of the machine and increase the followability of solid at that time. It is possible to prevent the toner from scattering when the amount of the developer is reduced.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akio Matsui 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. (72) Masami Tomita 1-3-6 Nakamagome, Ota-ku, Tokyo Stocks Inside Ricoh Company (72) Inventor Takahisa Kato 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh Company (72) Minoru Masuda 1-3-6 Nakamagome, Tokyo Ota-ku Stock Company Ricoh ( 72) Inventor Satomi Suzuki 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd.

Claims (7)

[Claims] 1. An image forming method of developing an electrostatic latent image using a two-component developer comprising a toner and a carrier,
The carrier that consumes toner in the development and does not substantially contain toner and the toner that is replenished are set to the toner concentration controlled in the image forming apparatus, and the absolute amount of charge when mixed for 15 seconds by a ball mill is set. Value is 7 μC / g to 40 μC / g, and the volume average particle size of the toner is 6 to 9 μC.
An image forming method, wherein the image forming method is set to m. 2. An image forming method for developing an electrostatic latent image using a two-component developer comprising a toner and a carrier,
The carrier that consumes toner in the development and contains substantially no toner and the toner to be replenished are set to the toner concentration controlled in the image forming apparatus, and the average charge amount when mixed for 15 seconds with a ball mill is set. Absolute value is 2 × 10 _-9 μC / piece to 12
An image forming method, characterized in that the mixture is carried out so as to have a concentration of × 10 ₋₉ μC / piece. 3. An image forming method for developing an electrostatic latent image using a two-component developer comprising toner and carrier,
The carrier that consumes toner in the development and does not substantially contain toner and the toner that is replenished are set to the toner concentration controlled in the image forming apparatus, and the absolute amount of charge when mixed for 15 seconds by a ball mill is set. The value is 7 μC / g to 40 μC / g, the volume average particle diameter of the toner is 6 to 9 μm, and the relationship between the charging ability of the toner in the developer and the charging ability of the replenishment toner is expressed by the following formula (I).
An image forming method characterized by mixing as represented by. ## EQU1 ## −10 ≦ QA −QB ≦ 4 (μC / g) (I) (QA: The above-mentioned substantially toner-free carrier and the toner to be replenished are set to control toner concentrations, and a ball mill is used for 15 Absolute value of charge amount after second mixing, QB: Absolute value of charge amount when the carrier containing substantially no toner and the toner in the developer are set to control toner concentrations and mixed for 15 seconds with a ball mill. value.) 4. An image forming method in which an electrostatic latent image is developed using a two-component developer composed of toner and carrier, and toner concentration is controlled by measuring the magnetic permeability of the developer with a magnetic bridge type toner sensor. The carrier concentration that consumes toner in the development and does not substantially contain toner, and the toner to be replenished are set to the toner concentration controlled in the image forming apparatus, and the charge amount when mixed for 15 seconds with a ball mill is set. An image forming method characterized in that the toner is mixed so that the absolute value is 10 μC / g to 40 μC / g, and the volume average particle diameter of the toner is 6 to 9 μm. 5. An electrostatic latent image is developed using a two-component developer comprising a toner and a carrier, and the toner particle occupies 20% of the carrier surface at a controlled toner concentration.
In the image forming method as described above, the carrier that consumes toner in the development and does not substantially contain toner and the toner that is replenished are set to the toner density controlled in the image forming apparatus, and the ball mill is used for 15 seconds. Mix so that the absolute value of the charge amount when mixed is 10 μC / g to 40 μC / g,
An image forming method, characterized in that the volume average particle diameter of the toner is 6 to 9 μm. 6. An image forming method in which an electrostatic latent image is developed using a two-component type developer comprising a toner and a carrier, and the toner density to be controlled satisfies the following formula (II): The absolute value of the charge amount when the consumed toner substantially containing no toner and the toner to be replenished is set to the toner concentration controlled in the image forming apparatus and mixed for 15 seconds with a ball mill is 10 μC / g to 40 μC / g so that the volume average particle diameter of the toner is 6 to 9 μm.
An image forming method comprising: Rc ³ ρc · a / rtρt · (rc + rt) ² · (100−a) ≧ 0.08 (II) (where, rc; carrier particle size, ρc; carrier true specific gravity, rt; toner particle Diameter, ρt; true specific gravity of toner, a; toner concentration (wt%).) 7. An image forming method in which an electrostatic latent image is developed using a two-component developer comprising a toner and a carrier, and the surface area of the carrier in one developing unit of the image forming apparatus is 15 m ² or less. A carrier that consumes toner in development and contains substantially no toner, and toner to be replenished,
The absolute value of the charge amount when mixed for 15 seconds with a ball mill is set to 10 μm by setting the toner concentration controlled in the image forming apparatus.
An image forming method comprising mixing C / g to 40 μC / g so that the toner has a volume average particle diameter of 6 to 9 μm.