JPH04274250A - Developer - Google Patents

Abstract

PURPOSE:To provide a copy image that is faithful to an original in addition to no transfer slip. CONSTITUTION:This developer is one that consists of positive charging resin fine grains A, weak charging resin fine grains B and inorganic powder C added on a toner surface, and it is featured that each mean grain size of these resin fine grains A and B is 0.03-1.0mu, preferably a volume resistivity value after drying is 10<14>OMEGA.cm for the fine grain A and 10<7>-10<14>OMEGA.cm for the fine grain B, respectively.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention has a step in which a transfer device is brought into contact with an electrostatic latent image carrier through a transfer material, and the toner image on the electrostatic latent image carrier is transferred onto the transfer material. The present invention relates to a developer used in an image forming method.

0002

[Prior Art] A toner image formed on the surface of a latent image carrier is
In an image forming device that involves the process of electrostatically transferring onto a sheet-like transfer material, mainly paper, a latent image carrier that runs in an endless manner, such as a rotating cylinder or an endless belt, is used, and a bias is applied. A device configured to transfer the toner image on the latent image carrier side to the transfer material by pressing a transfer device against it and passing the transfer material between the two (for example, Japanese Patent Laid-Open No. 59-4
No. 6664) has been proposed.

Compared to transfer means using corona discharge, which has been widely used in the past, such a device is capable of carrying a latent image on a transfer material by adjusting the pressing force of a transfer roller against a latent image carrier. The adsorption area to the body can be expanded. Furthermore, since the transfer material is actively pressed and supported at the transfer site, there is less risk of synchronization caused by the transfer material conveyance means or transfer misalignment due to loops and curls existing in the transfer material. It is easy to meet demands such as shortening the conveyance path and reducing the diameter of the latent image carrier.

On the other hand, in a device that performs transfer by contact, since a transfer current is supplied from the contact portion, it is necessary to apply a certain amount of pressure to the transfer device. When contact pressure is applied, pressure is also applied to the toner image on the latent image carrier, which tends to cause aggregation.

Furthermore, when the surface of the latent image carrier is made of resin, close contact also occurs between the toner aggregates and the latent image carrier, inhibiting transfer to the transfer material, and in extreme cases,
A phenomenon in which the toner image is likely to be lost because areas with strong adhesion are not transferred at all is likely to occur.

[0006] This phenomenon becomes particularly noticeable in the line portion of 0.1 to 2 mm. This is because edge development occurs in the line portion, and a large amount of toner is deposited on the toner, which tends to cause aggregation due to pressure and cause defects due to transfer. At this time, the toner image formed becomes a copy in which an image is formed only on the outline, which is called "transfer void." Figures 5 to 8
shows an example of hollow transcription. FIGS. 5 and 7 are accurate copies, and if a transfer defect occurs, the result will be as shown in FIGS. 6 and 8, respectively.

[0007] "Transfer voids" become particularly noticeable on thick paper of 100 g/cm2 or more, on OHP films with high smoothness, and when copying the second side of double-sided copying. In the case of cardboard and OHP films, since the transfer material is thick, it is thought that the effect on the transfer electric field is small and that the pressure is strong and hollows are likely to occur.

When copying the second side of double-sided copying, when the transfer material passes through the fixing device during the formation of a fixed image on the first side, a release agent contained in the fixing device to prevent offset is attached to the transfer material, and the second side is It is thought that this prevents the toner from adhering to the transfer material during the transfer of the surface, making it more likely that hollow spots will occur.

As described above, in the case of a transfer device using an abutting member, although there are many advantages such as miniaturization and low power consumption, the conditions for the transfer material are severe.

[0010] In recent years, as image forming apparatuses such as electrophotographic copying machines have become widespread, their uses have expanded to a wide variety.
The requirements for image quality are also becoming stricter. When copying images such as general documents and books, it is required to reproduce extremely finely and faithfully, without being crushed or cut off, even down to the minute characters. In particular, when the latent image on the photoreceptor of an image forming apparatus is a line image of 100 μm or less, fine line reproducibility is generally poor and the sharpness of the line image is still insufficient. Recently, in image forming devices such as electrophotographic printers that use digital image signals, the latent image is formed by a collection of dots in a fixed unit, and the dot density changes in solid areas, halftone areas, and light areas. It is expressed by. However, if the toner particles do not adhere to the dots faithfully and the toner particles protrude from the dots, the problem arises that the gradation of the toner image that corresponds to the ratio of dot densities in the black and white areas of the digital latent image cannot be obtained. There is a point. Furthermore, when improving resolution by reducing dot size to improve image quality, it becomes more difficult to reproduce latent images formed from minute dots, resulting in poor resolution, poor gradation, and poor sharpness. This tends to result in images lacking in detail.

Several developers have been proposed so far for the purpose of improving image quality.

[0012] JP-A-1-112253, JP-A-2
-284158 and other publications propose a small-diameter toner having a specific particle size distribution, but as the toner becomes smaller in diameter, it becomes more difficult to charge the toner surface uniformly, especially when the initial fine line image width (line width) There is a tendency for the lines to become thinner, and there is still room for improvement in terms of line width stability, especially as toners for printers.

[0013]

SUMMARY OF THE INVENTION An object of the present invention is to provide a developer which solves the above-mentioned problems.

[0014] An object of the present invention is to provide a developer capable of producing high-quality images that are faithful to latent images, regardless of the conditions of the transfer material, in an image forming method using pressure transfer such as a contact transfer method. It's about doing.

An object of the present invention is to provide a developer that does not have the phenomenon of "transfer voids" or can suppress the phenomenon.

[0016] An object of the present invention is to provide a developer that provides a high quality image without transfer voids even when a transfer material such as thick transfer paper is used.

An object of the present invention is to provide a developer which can provide good fine line reproducibility and stable line width from the initial stage.

[0018]

[Means and effects for solving the problems] The present invention provides positively chargeable resin fine particles (
A), for electrostatic image development, characterized in that weakly charging resin fine particles (B) and inorganic fine powder (C) having an average particle size of 0.03 to 1.0 μm are added to the surface of the toner particles. It is a developer.

The present inventors have developed a method of transferring a developed image on an electrostatic image carrier through a transfer material to a transfer material while bringing a transfer means into contact with the electrostatic image carrier by using the above-mentioned developer. It has been found that the apparatus can also produce images with stable line widths without transfer voids.

[0020] Resin fine particles (A) and (B) in the present invention
) has an average particle diameter of 0.03 to 1.0 μm, and outside this range, the effect on transfer voids is small, preferably 0.
．． 05 to 0.8 μm.

[0021] The average particle size of the resin particles is determined by randomly selecting 10,000 particles from an electron micrograph (×10,000) of the resin particles.
It is obtained by selecting 0 resin fine particle images and measuring their diameters.

[0022] Further, the volume resistivity value of the positively chargeable resin fine particles (A) after drying at 40°C is preferably 1014 Ω·cm or more, and the charge amount is preferably +50 μc/g to +300 μc/g. When the volume resistivity value is lower than 1014 Ω·cm or when the amount of charge is lower than +50 μc/g, the initial line width tends to become thinner. Also +300μ
If it is larger than c/g, the concentration tends to decrease.

It is preferable that the volume resistivity of the weakly chargeable resin particles (B) is in the range of 10 7 to 10 14 Ω·cm, and the amount of charge is in the range of +50 μc/g to −100 μc/g. When the volume resistivity value is less than 10 7 Ω·cm or the amount of charge is greater than −100 μc/g, a decrease in concentration is likely to occur.

40 of the weakly charged resin fine particles (B) of the present invention
Volume resistivity value after drying at ℃ is 107~1014Ω・cm
preferably 108 to 1013, more preferably 108 to 1013
Ω・cm is good. If a resistor having a resistance lower than 10<7>Ω·cm is used, the amount of charge of the developer is likely to be reduced, resulting in a decrease in image density. Furthermore, if a resistor with a resistivity higher than 1014 Ω·cm is used, the fluidity of the developer is deteriorated and image density unevenness is likely to occur.

The measurement of the volume resistivity of fine resin particles in the present invention is carried out, for example, as follows.

First, a sample is molded into a tablet using a tablet molding device. First, approximately 0.3 g of the sample was placed in a tablet molding chamber, then a push rod was inserted into the tablet molding chamber, and the pressure was applied for 5 minutes at 250 kg/cm2 with a hydraulic pump to form a tablet with a diameter of approximately 13 m.
m, and a pellet-like tablet with a height of about 2 to 3 mm is molded.

Since the volume resistivity value is easily affected by the moisture adsorbed by the resin particles and the measurement environment, the tablets were dried in a dryer at 40°C for 18 hours and then immediately heated to 23.5°C and 65°C.
%RH environment using a resistance measuring device (HEWLETT PAKARD 16008A (RESISTIVITY CE)).
LL) or Yokogawa Hewlett-Packard (YOKOG)
Manufactured by AWA HEWLETT PAKARD) 43
29A high resistance meter (HIGHRESIST)
ANCE METER) etc.) to a voltage of 1000
The resistance value when V is applied is measured, and the volume specific resistance value ρ is determined by calculation.

[0028]ρ(Ω・cm)=R(Ω)×S(cm2)
/l (cm) S: Cross-sectional area of the sample l: Thickness of the sample The amount of charge on the resin fine particles used in the present invention is measured by the following method. That is, 0.2 g of resin fine particles and 200 to 300
Carrier iron powder that is not coated with resin and has a main particle size in the mesh (for example, EFV200/30 manufactured by Nippon Tetsuko Co., Ltd.)
0) 20.0g under the above environment, approximately 50c
．． c. Mix thoroughly (hold by hand and shake up and down approximately 125 times for approximately 20 seconds) in a wide-mouth polyethylene bottle with a lid having a volume of .

Next, as shown in FIG. 3, approximately 2.0 g of the mixture is placed in a metal measuring container 32 with a 400 mesh screen 33 at the bottom, and a metal lid 34 is placed. The weight of the entire measurement container 32 at this time is measured and is defined as W1 (g). Next, in the suction device 31 (at least the portion in contact with the measurement container 32 is an insulator), suction is performed from the suction port 37 and the air volume control valve 36 is adjusted to set the pressure of the vacuum gauge 35 to 250 mmHg. In this state, sufficient suction is performed for 5 minutes to remove the resin particles. The potential of the electrometer 39 at this time is assumed to be V (volt). Here, 38 is a capacitor, and the capacitance is C (μF). In addition, weigh the entire weight of the measurement container after suction W2 (
g). The amount of triboelectric charge (μc/g
) is calculated as shown below.

Tribocharge amount = CV/(W1-W2) In the present invention, the amount of the positively chargeable resin particles (A) added is preferably 0.01 to 1.0 parts by weight per 100 parts by weight of toner particles. 0.03 to 0.5 part by weight is preferred.

The amount of the weakly charged resin particles (B) added is preferably 0.05 to 2.0 parts by weight, particularly 0.1 to 1.0 parts by weight.
Parts by weight are preferred.

[0032] The resin fine particles described above are produced by emulsion polymerization, spray drying, or the like. Preferably styrene,
Resin particles having a glass transition point of 80° C. or higher obtained by copolymerizing components used in toner binder resins such as acrylic acid, methyl methacrylate, butyl acrylate, and 2-ethylhexyl acrylate by an emulsion polymerization method exhibit good effects.

It is also true that the surface may be cross-linked with divinylbenzene or the like, and the surface may be treated with a metal, metal oxide, pigment, dye, surfactant, etc. in order to adjust the volume resistivity and tribocharge amount. This is a preferred form of the invention.

[0034] The inorganic fine powder (C) used in the present invention is
Specific surface area due to nitrogen adsorption measured by BET method is 70-3
00 m2/g gives good results.

As the inorganic fine powder (C), negatively charged hydrophobic silica fine powder is particularly preferred.

The hydrophobic inorganic fine powder used in the present invention preferably has a triboelectric charge of -100 .mu.c/g to -300 .mu.c/g. Triboelectric charge is -100
If it is less than .mu.c/g, the amount of triboelectric charge of the developer itself decreases, resulting in a decrease in humidity characteristics. -300μc/g
If a material exceeding
This will impair the durability characteristics. Furthermore, if the powder is finer than 300m2/g, it has no effect when added to the developer, and if it is coarser than 70m2/g, there is a high probability that it will exist as a free substance, which may cause black spots due to uneven accumulation of inorganic fine powder or aggregates. easy.

The tribo value of the negatively charged inorganic fine powder is measured in the same manner as the tribo value of the resin fine particles.

Among the inorganic fine powders used in the present invention, particularly preferred are dry silica produced by vapor phase oxidation of silicon halogen compounds or dry silica called fumed silica, and water glass. Both so-called wet silica can be used, but there are few silanol groups on the surface and inside the silica fine powder, and Na
Pry-processed silica free of production residues such as 2O, SO32-, etc. is preferable.

In addition, in the case of dry silica, it is also possible to obtain a composite fine powder of silica and other metal oxides by using other metal halide compounds such as aluminum chloride or titanium chloride together with silicon halide compounds in the manufacturing process. and includes them as well.

The particle size is 0.0 as the average primary particle size.
It is desirable to use fine silica powder within the range of 0.01 to 2 μm, particularly preferably within the range of 0.002 to 0.2 μm.

The inorganic fine powder used in the present invention is preferably hydrophobic, and the hydrophobic treatment agent is preferably at least a silicon compound having an organosiloxane unit such as silicone oil or silicone varnish.

[0042] The silicone oil used in the treatment of the fine powder used in the present invention has the general formula

[0043]

[Chemical 1] Examples include dimethyl silicone oil, alkyl-modified silicone oil, α-methylstyrene-modified silicone oil, chlorphenyl silicone oil, fluorine-modified silicone oil, etc., but are not limited to the above. .

The silicone oil preferably has a viscosity of 50 to 1000 centistokes at 25°C. 5
If it is less than 0 centistokes, part of the charge will be exerted due to the addition of heat, and the charging characteristics will deteriorate. Furthermore, if the particle size exceeds 1000 centistokes, handling becomes difficult. As a method for silicone oil treatment, known techniques can be used. For example, silicic acid fine powder and silicone oil are mixed using a mixer. Spray silicone oil into the silicic acid fine powder using a sprayer. Alternatively, silicone oil may be dissolved in a solvent and then silicic acid fine powder may be mixed therein, but the method is not limited thereto.

[0045] As the silicon varnish for treating fine silicic acid powder used in the present invention, known materials can be used.

For example, KR-25 manufactured by Shin-Etsu Silicone Co., Ltd.
1, KP-112, etc., but are not limited thereto.

As a method for silicone varnish treatment, the same known techniques as for oil treatment can be used. The above-mentioned treated silicic acid fine powder (hereinafter referred to as treated silica) exhibits an effect when the amount is 0.1 to 1.6 parts by weight, particularly preferably 0.3 to 1.6 parts by weight, based on 100 parts by weight of toner. It has excellent stability when added. If the amount is less than 0.1 part by weight, no effect will be observed, and if it exceeds 1.6 parts by weight, problems with development and fixing will occur, which is not preferable.

A part of the silicon compound having organosiloxane units treated on the surface of the inorganic fine powder is transferred onto the electrostatic image carrier, and has the effect of further facilitating the cleaning of the free dye-based charge control agent.

[0049] The degree of hydrophobicity of the inorganic fine powder in the present invention is as follows:
Use the values measured by the following method. Of course, other measurement methods can also be applied while referring to the measurement method of the present invention.

Pour 100 ml of ion-exchanged water and 0.1 g of sample into a 200 ml sealed separatory funnel, and shake at 90 rpm with a shaker (Turbula shaker mixer T2C type).
Shake for 10 minutes under the following conditions. After shaking and allowing to stand for 10 minutes to separate the inorganic powder layer and water layer, the lower water layer was
Collect 30 ml, put it in a 10 mm cell, and measure the transmittance at a wavelength of 500 nm using blank ion-exchanged water that does not contain silica fine powder as a reference, and use the transmittance value as the degree of hydrophobicity of the inorganic fine powder. It is.

The degree of hydrophobicity of the hydrophobic inorganic fine powder in the present invention is preferably 60% or more, more preferably 90% or more. If the degree of hydrophobicity is less than 60%, it is difficult to obtain a high-quality image due to moisture adsorption of the inorganic fine powder under high humidity.

The contact pressure used in the present invention is preferably 3 g/cm or more in terms of linear pressure. Line pressure is calculated using the following formula.

(Linear pressure) [g/cm] = (Total pressure applied to the transfer material) [g] ÷ (Length of contact) [cm] If the contact pressure is less than 3 g/cm, transfer is not possible. This is undesirable because it causes blurring in the conveyance of the material and transfer defects due to insufficient transfer current. Particularly preferably 20 g/cm or more (more preferably 25 to 8
0g/cm).

Examples of transfer devices using the developer of the present invention include a transfer roller as shown in FIG. 1 or a transfer belt as shown in FIG. FIG. 1 is a schematic side view of the main parts of a typical image forming apparatus of this type, and the illustrated apparatus has a cylindrical latent image carrier 1 ( A conductive transfer roller 2 is disposed in contact with a photoreceptor (hereinafter referred to as a photoreceptor 1).

In FIGS. 1 and 2, a primary charger for uniformly charging the surface of the photoreceptor 1, which is an electrostatic image carrier, is provided with an image-modulated laser beam on the charging surface. Or an exposure section for projecting a light image such as light reflected from a document and attenuating the potential of the relevant part to form an electrostatic latent image, a developing device, and for removing residual toner remaining on the surface of the photoreceptor after transfer. A cleaner and other members necessary for image formation are provided, but these are omitted.

The transfer roller 2 has a core bar 2a and a conductive elastic layer 2b, and the conductive elastic layer 2b is made of polyurethane resin or ethylene-propylene-diene terpolymer in which a conductive material such as carbon is dispersed. It is made of an elastic material such as (EPDM) having a volume resistance of 10 6 to 10 10 Ω·cm. A bias is applied to the core metal 2a by a constant voltage power supply 8. The bias condition is a current value of 0.1 to 50 μA.
, voltage (absolute value) 100 to 5000V (preferably 50
0-4000V) is preferred.

FIG. 2 shows the present invention applied to a transfer belt. The transfer belt 9 is supported and driven by a conductive roller 10. Pressure is generally applied to the transfer roller by applying pressure to the end bearing of the core bar 2a.

The present invention is particularly effective for image forming apparatuses in which the surface of the electrostatic image carrier is made of an organic compound such as resin.

[0059] When the organic compound forms the surface layer,
It easily adheres to the binder resin contained in the toner, and especially when the same material is used, chemical bonding tends to occur at the contact point between the toner and the surface of the photoreceptor, which has the problem of reducing transferability. Because there is.

The surface material of the electrostatic image carrier used in the present invention includes silicone resin, vinylidene chloride resin, ethylene-vinylidene chloride resin, styrene-acrylonitrile copolymer, styrene-methyl methacrylate copolymer, and styrene. Examples include polyethylene terephthalate resin, polycarbonate resin, etc., but the present invention is not limited thereto, and copolymerization, blending, etc. of other monomers or exemplified resins can also be used.

[0061] The present invention is applicable when the diameter of the photoreceptor 1 is 50 mm or less (
(more preferably 40 mm or less, for example 25 to 35 mm)
This is particularly effective for image forming apparatuses having photosensitive drums.

[0062] In the case of a small-diameter photosensitive drum, the curvature is large even if the linear pressure is the same, so pressure tends to concentrate at the contact portion. It is thought that the same phenomenon occurs with belt-shaped photoreceptors, and it is also effective for image forming apparatuses having belt-shaped photoreceptors with a curvature of 25 mm or less at the transfer section.

In the present invention, as the binder resin for the magnetic toner, monopolymers of styrene and its substituted products such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene; styrene-p-chlorostyrene copolymers, styrene- Propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer,
Styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-methyl chloromethacrylate copolymer,
Styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinylethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene- Styrenic copolymers such as acrylonitrile-indene copolymers; polyvinyl chloride;
Polyvinyl acetate, polyethylene, polypropylene, silicone resin, polyester, epoxy resin, polyvinyl butyral, rosin, modified rosin, terpene resin, phenolic resin, xylene resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorine Examples include chemically paraffin and paraffin wax. These may be used alone or in combination.

[0064] Among these resins, styrene-acrylic copolymers are preferably used in the present invention.
Especially styrene-n-butyl acrylate (St-nBA)
Copolymer, styrene-n-butyl methacrylate (St-
nBMA) copolymer, styrene-n-butyl acrylate-2-ethylhexyl methacrylate (St-nBA-2
EHMA) copolymers and the like are preferably used.

As the coloring material that can be added to the magnetic toner of the present invention, conventionally known carbon black, copper phthalocyanine, iron black, etc. can be used.

The magnetic toner according to the present invention contains a magnetic material. The contained magnetic substance is a substance that is magnetized when placed in a magnetic field, such as powder of ferromagnetic metal such as iron, cobalt, or nickel, or magnetite, γ-Fe2
Alloys and compounds such as O3 and ferrite can be used.

These magnetic fine particles preferably have a BET specific surface area of 1 to 20 m 2 /g, particularly 2.5 to 12 m 2 /g, and a Mohs hardness of 5 to 7, as determined by the nitrogen adsorption method. The content of this magnetic powder is 10% of the binder resin.
It is preferably 70 to 120 parts by weight relative to 0 parts by weight.

The toner of the present invention may contain a charge control agent if necessary, and a negative charge control agent such as a metal complex salt of a monoazo dye, a metal complex salt of salicylic acid, alkyl salicylic acid, dialkyl salicylic acid, or naphthoic acid is used. .

The developer of the present invention may further contain other additives, such as lubricants such as Teflon or zinc stearate, fixing aids (such as low molecular weight polyethylene), or A metal oxide such as tin oxide may be added as a conductivity imparting agent.

[0070] In manufacturing the toner according to the present invention,
It can be obtained by thoroughly kneading the constituent materials using a thermal kneader such as a hot roll, kneader, or extruder, followed by mechanical crushing and classification, or by dispersing the materials in a binder resin solution and then spray drying. Alternatively, various methods can be applied, such as a polymerization method and a toner production method in which a monomer to constitute a binder resin is mixed with a predetermined material to form an emulsified suspension and then polymerized to obtain a toner.

Further, with reference to FIG. 4, an image forming method and apparatus using the developer of the present invention will be explained.

The surface of the photoreceptor is negatively charged by the primary charger 402, and a digital latent image is formed by image scanning through exposure 405 with laser light, and the magnetic blade 4
The latent image is reversely developed using a one-component magnetic developer 410 of a developing device 409 equipped with a developing sleeve 404 containing magnets 11 and 11 and a magnet. In the developing section, an alternating bias, a pulse bias, and/or a DC bias is applied between the conductive base of the photosensitive drum 1 and the developing sleeve 404 by a bias applying means 412 . When the transfer paper P is conveyed and reaches the transfer section, the roller transfer means 2 charges the transfer paper P from the back side (the opposite side to the photosensitive drum side) with the voltage application means 8, thereby forming a developed image on the surface of the photosensitive drum. (toner image) is electrostatically transferred onto transfer paper P. The transfer paper P separated from the photosensitive drum 1 is transferred to a heating and pressure roller fixing device 407.
A fixing process is performed to fix the toner image on the transfer paper P.

The one-component developer remaining on the photosensitive drum after the transfer process is removed by a cleaning device 408 having a cleaning blade. After cleaning, the photosensitive drum 1 is neutralized by erase exposure 406, and the process starting with the charging process by the primary charger 402 is repeated again.

The electrostatic image carrier (photosensitive drum) has a photosensitive layer and a conductive substrate, and moves in the direction of the arrow. A non-magnetic cylindrical developing sleeve 404 serving as a toner carrier rotates in the developing section so as to move in the same direction as the surface of the electrostatic image holder. Inside the nonmagnetic cylindrical sleeve 404, a multipolar permanent magnet (magnet roll) serving as a magnetic field generating means is arranged so as not to rotate. A one-component insulating magnetic developer 410 in the developing device 409 is applied onto a non-magnetic cylindrical surface, and the toner particles are given, for example, a negative triboelectric charge by friction between the surface of the sleeve 404 and the toner particles. Further, an elastic blade 411 made of an elastic material such as silicone rubber or urethane rubber is brought into contact with the cylindrical surface to control the thickness of the developer layer thinly (30 μm to 300 μm) and uniformly, thereby controlling the electrostatic charge image in the developing section. A developer layer thinner than the gap between the holder 1 and the developing sleeve 404 is formed so that they are not in contact with each other. By adjusting the rotational speed of the developing sleeve 404, the sleeve surface speed is made to be substantially equal to or close to the speed of the electrostatic image holding surface. Instead of iron, a permanent magnet may be used as the blade 411 to form opposing magnetic poles. In the developing section, an alternating current bias or a pulse bias may be applied by bias means 412 between the developing sleeve 404 and the electrostatic image holding surface. This AC bias has f of 200 to 4,000H.
It is sufficient if z and Vpp are 500 to 3,000V.

When the toner particles are transferred in the developing area, the toner particles are transferred to the electrostatic image side by the action of the electrostatic force of the electrostatic image holding surface and the alternating current bias or pulse bias.

[0076]

[Examples] The present invention will be specifically explained below using Examples, but these are not intended to limit the invention in any way. All parts in the following formulations are parts by weight.

Example 1 Styrene/butyl acrylate/divinylbenzene copolymer 100 parts (copolymerization weight ratio 8
4/15.5/0.5, weight average molecular weight 250,000) magnetite (average particle size 0.2 μm)
100 parts low molecular weight ethylene-propylene copolymer
Part 3 Chromium complex of monoazo dye

Mix 1 part of the above ingredients well in a blender, then heat to 130°C.
The mixture was kneaded using a twin-screw kneading extruder set at . At this time, if the set temperature is too high, the magnetic toner will tend to fog. The obtained kneaded material was cooled and coarsely pulverized using a cutter mill, and then finely pulverized using a pulverizer using a jet stream.
The obtained finely pulverized powder was classified using a fixed wall type wind classifier to produce classified powder. Furthermore, the obtained classified powder was strictly classified and removed at the same time to remove ultra-fine powder and coarse powder using a multi-division classification device (Elbowjet classifier manufactured by Nippon Steel Mining Co., Ltd.) that utilizes the Coanda effect, resulting in a weight average particle size of 6.8 μm. An insulating magnetic toner (I) was obtained. The obtained magnetic toner (I) was negatively charged by friction against the iron powder carrier.

Fine resin particles (A), fine resin particles (B), and fine inorganic powder (C) were added to the negatively chargeable insulating magnetic toner and mixed in a Henschel mixer to obtain a one-component negatively chargeable developer. .

Table 1 shows the physical properties of the resin fine particles (A), Table 2 shows the physical properties of the resin fine particles (B), Table 3 shows the physical properties of the inorganic fine powder (C), Table 4 shows the composition of the developer, and Table 5 shows the evaluation results. shows.

The obtained developer was transferred to a commercially available copying machine FC-5 (
Canon Inc.'s OPC laminated negatively charged photoreceptor, curvature separation type using a drum diameter of φ30) was modified for reversal development, and the modified machine incorporated a transfer device with a transfer roller as shown in Figure 1. I put it in. The conditions for the transfer roller are: surface rubber hardness of the transfer roller 27°, transfer current 1 μA, transfer voltage +2000V, contact pressure 50 [g/
cm]. The conductive elastic layer of the transfer roller was formed of EPDM in which conductive carbon was dispersed, and had a volume resistivity of 108 Ω·cm.

The primary charge is -700V, a gap is set so that the photosensitive drum and the developer layer on the developing drum (with magnet included) are not in contact with each other, and an AC bias (f=1,800Hz, VPP) is applied.
= 1,600V) and DC bias (VDC = -50
Image formation was performed while applying 0V) to the developing drum. The toner-fixed image produced and fixed by a heating and pressure roller was evaluated as follows. (1) Image density: Normal copying machine plain paper (75g/m2
) Evaluation was made by maintaining image density when 1,000 sheets were passed. ○ (Good): 1.35 or more △ (Acceptable): 1.0 to 1.34 × (Unacceptable): 1.0 or less (2) Transfer condition: 120 g/m2, which is a strict transfer condition
The paper was passed through thick paper and evaluated based on the state of hollow transfer. ○: Good (see FIG. 5) Δ: Practical ×: Poor (see FIG. 6) (3) Image quality: Toner scattering, roughness, etc. were visually evaluated. ○: Good △: Practical ×: Not practical (4) Thin line reproducibility: Evaluation was made based on the reproducibility of a latent image of a 100 μm wide horizontal line.

[0082]

[Table 1]

[0083]

[Table 2]

[0084]

[Table 3]

[0085]

[Table 4]

[0086]

[Table 5]

[0087]

As described above, according to the present invention, it is possible to stably provide accurate copied images for a long period of time with excellent fine line reproducibility and transfer conditions.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an example of a transfer device using the developer of the present invention.

FIG. 2 is a schematic diagram of an example of a transfer device using the developer of the present invention, which is different from FIG. 1;

FIG. 3 is an explanatory diagram of a triboelectric charge measuring device.

FIG. 4 is an explanatory diagram of an image forming method using the developer of the present invention.

FIG. 5 is a diagram showing an example of a copied image without transfer omissions.

FIG. 6 is a diagram illustrating an example of a copy image with missing transfer.

FIG. 7 is a diagram showing an example of a copied image without transfer omissions.

FIG. 8 is a diagram illustrating an example of a copy image in which transfer is missing.

[Explanation of symbols]

1 Photoreceptor 2 Transfer roller 2a Core metal 2b Conductive elastic layer 8 Constant voltage power supply 9 Transfer belt 10 Conductive roller 31 Suction machine 32 Measurement container 33 Conductive screen 34 Lid 35 Vacuum gauge 36 Air volume control valve 37 Suction port 38 Capacitor 39　Electrometer 402 Primary charger 404 Developing sleeve 405 Exposure 406 Erase exposure 407 Fuser 408 Cleaning device 409 Developing device 410 Developer 411 Blade 412 Bias application means

Claims (2)

[Claims] Claim 1: Positively chargeable resin fine particles (A) having an average particle size of 0.03 to 1.0 μm;
．． A developer characterized in that weakly charging fine resin particles (B) and inorganic fine powder (C) having a diameter of 0 μm are added to the surface of toner particles. 2. The positively chargeable resin fine particles (A) have a volume resistivity value of 1014 Ω·cm or more after drying at 40°C,
2. The developer according to claim 1, wherein the weakly charging resin fine particles (B) have a volume resistivity value of 107 to 1014 Ω·cm after drying at 40°C.