JPH02191966A - Developer for electrostatic charge development and image forming method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an image forming method that includes a step of developing an electrostatic latent image formed in electrophotography, electrostatic printing, etc. using magnetic toner. .

[Prior Art] Conventionally, methods for forming electrostatic latent images include an analog method in which an original is irradiated with an exposure means such as a halogen lamp, and the reflected light is focused on an electrostatic latent image holder, and a laser beam method. ,
A digital method in which a latent image is formed by directly irradiating LED light or the like onto an electrostatic latent image holder.A novel developing method using a one-component magnetic toner for developing these electrostatic latent images is disclosed in, for example, JP-A-55-18656. This method has been proposed in Japanese Patent Application Laid-Open No. 55-28659. In this developing method, an insulating magnetic toner is uniformly applied onto a cylindrical toner carrier having a magnet inside, and the toner layer on the toner carrier is made to face the latent image carrier without coming into contact with it. In this method, an electrostatic latent image is developed by transferring an insulating magnetic toner from a toner carrier to a latent image carrier.

At the time of development, an alternating voltage is applied between the toner carrier and the substrate conductor of the latent image holder, and the toner is moved back and forth between the toner carrier and the latent image holder, thereby achieving uniform tonality and gradation. It has excellent reproduction and can perform good development without narrowing of the edges of the image. In this developing method, since the toner is an insulator, electrostatic transfer is easy.

As a method of forming a toner layer on a toner carrier, there is a method of using a coating blade at the outlet of a toner container.

For example, in the device shown in FIG. 1, a blade 1a made of a magnetic material is provided at a position facing one magnetic pole Nl of a fixed magnet 4 housed in a toner carrier 2, and the magnetic force lines between the magnetic pole and the magnetic blade are The thickness of the toner layer is regulated by making use of magnetic force by making spikes of magnetic toner stand along the edges and cutting the spikes of magnetic toner with the edge of the tip of the blade (for example, Japanese Patent Laid-Open No. 54-43037). (see official bulletin).

In FIG. 1, 7 is a developing device containing toner lO;
denotes a latent image carrier (hereinafter referred to as photoconductor or photoconductor drum) such as a photoconductor drum in electrophotography or an insulating drum in electrostatic recording.

Analog latent images and digital latent images are formed in different ways, and the surface potentials of the latent images that are appropriate for development are also different. The method of performing both analog and digital development as intended by the present invention, particularly the method of performing both in one bus, has many problems that were not known in the past.

A digital latent image is formed by charging an electrostatic latent image carrier and lowering the surface potential of the irradiated portion using a light source such as a laser beam to provide a potential contrast. In order to visualize this latent image, it is sufficient to develop only one of the potentials. By the way, normal development is when the toner is applied to the high potential area (VD area) and development is performed, and reversal development is when the low potential area is developed.

The case of regular development will be described below.

When development is performed with the low potential area set to the bright area potential (VL) and the high potential area set to the dark area potential (Vo), the VL area is visualized as a white image and the VD area is visualized as a black image. During this development, it is sufficient that only the VD area is developed, but if the VL area is developed, a fog appears. Although the surface potential of the VL portion is lowered by an exposure means such as a laser spot, in reality, the potential between the spots is not lowered sufficiently and variations occur in the surface potential of the VL portion. Therefore, there is a possibility that a high-potential area is generated in the part (1), and this area is developed and becomes visible as a sliver-like fog. On the other hand, halftones in a digital latent image are expressed by the number of dots and line density. Therefore, there is no need to develop intermediate potentials and visualize intermediate tones (halftones).

To visualize a digital latent image using the development method described above, the gradation reproducibility of the intermediate potential is not a problem, and the area near the Vo area is sufficiently developed, and the low potential area near the vL area is not developed. Requires magnetic toner.

In the conventional development method using magnetic toner, the curve of image density versus surface potential is VL and V. There was a problem in that the slope became smaller near the lower part (see Figures 2 and 3).

When developing a digital latent image, the areas with high potential near the VL area are developed and toner remains. To avoid this, the curve of image density versus surface potential is It was necessary to use a developing method in which the slope was increased and the developing conditions were set so as not to affect the density curve. (Development method A is used.) On the other hand, an analog latent image is formed by charging an electrostatic latent image carrier, using reflected light from the original as a light source, lowering the surface potential according to the density of the original, and setting the potential contrast. It is something that makes you

When developing is performed with the low potential area set to V5, the high potential area set to vo, and the intermediate potential area set to halftone potential (VH), the 16th section becomes a white image, the VD section becomes a black image, and the V□ section becomes an eight-tone image. Be visualized.

Since the visualization of intermediate tones is determined by the surface potential, it is necessary to develop each potential with good gradation.

In order to visualize an analog latent image using the above-mentioned developing method, the gradation reproducibility of the intermediate potential is also important.

Therefore, when developing an analog latent image, the slope of the image density curve with respect to the surface potential should be made small, as shown in Figure 3.
A developing method is used in which developing conditions are set so that gradation is obtained. (Development method B is used.) In order to improve the gradation reproducibility, if the gradient of potential-density is made smaller, the skirt will extend toward the VD area in the 16th part, but in the case of an analog latent image, the reflected light will be reflected in the 16th part. uniformly irradiated,
Since the potential is constant, fogging is generally less likely to occur.

However, when developing method B is applied to a digital latent image, there is a tendency for fogging to occur in the 16th part because a trailing occurs near VL of the potential-density slope.

On the other hand, when developing method A is applied to an analog latent image, since the potential-density slope is large, the density changes greatly with a slight change in potential, resulting in poor reproduction of halftones and halftone gradation. It disappears.

Conventionally, in order to form an analog latent image, 400 to 7
Since this is carried out using visible light of 00 nm, a photosensitive drum having spectral sensitivity in this wavelength range is used.

On the other hand, when forming a digital latent image using a light source such as a semiconductor laser, a photosensitive drum having spectral sensitivity in the infrared region around 800 nm is used.

It has both of these spectral sensitivities and charging characteristics.

It was difficult to produce a photosensitive drum with sufficient electrophotographic properties such as residual potential and dark decay, and there was no toner suitable for this purpose, so it was difficult to develop digital latent images and analog latent images successfully with the same image forming device. This has been difficult with conventional image forming methods.

[Problems to be Solved by the Invention] An object of the present invention is to provide an image forming method using a developing method using a one-component magnetic toner that solves the above-mentioned problems and visualizes a digital latent image and an analog latent image. A developer for an image forming method is provided.

Another object of the present invention is to provide an image forming method capable of simultaneously visualizing a digital latent image and an analog latent image, and a developer for the image forming method.

Furthermore, another object of the present invention is to achieve high image density and no fogging in the visualization of digital latent images and analog latent images.
An object of the present invention is to provide an image forming method that is excellent in expressing dots and lines, and a developer for the image forming method.

Still another object of the present invention is to provide an image forming method with excellent gradation in visualizing an analog latent image, and a developer for the image forming method.

necessary to form digital latent images and analog latent images.
It is possible to obtain a photosensitive drum with uniform spectral sensitivity from white light to long wavelength light, high sensitivity and excellent electrophotographic characteristics.
As a result, it has become possible to provide an image forming apparatus that incorporates the combined functions of both a copying machine and a laser printer. The present invention provides an image forming method that can develop a digital latent image without fogging, develop an analog latent image with good gradation, and make each latent image visible.

[Means and effects for solving the problems] The present invention provides an organic photoreceptor for electrophotography that contains at least two or more charge-generating substances and holds digital and analog electrostatic images, and a toner that carries a magnetic toner on its surface. It is used in an image forming method in which magnetic toner is placed on the toner carrier with a certain gap in a developing section, and the magnetic toner is regulated to a thickness thinner than the gap on the toner carrier, and then conveyed to the developing section and developed. It is a developer,
The magnetic toner contains 12 to 60% by number of magnetic toner particles having a particle size of 5 μm or less, 1 to 33% by number of magnetic toner particles having a particle size of 8 to 12.7 μm, and 1 to 33% by number of magnetic toner particles having a particle size of 8 to 12.7 μm. The present invention relates to a developer for developing electrostatic images, which contains magnetic toner particles in an amount of 2.0% by volume or less and has a particle size distribution in which the volume average particle diameter of the magnetic toner is 4 to 10 μm.

The present invention provides an electrophotographic organic photoreceptor that contains at least two or more charge-generating substances and holds digital and analog electrostatic images, and a toner carrier that carries magnetic toner on its surface, with a certain gap formed between them in a developing section. In an image forming method in which magnetic toner is arranged on a toner carrier and regulated to have a thickness thinner than the gap, the magnetic toner is conveyed to a developing section and developed, wherein the magnetic toner has a particle size of 5 μm or less. 1 particle
Contains 2 to 60% by number, 1 to 33% by number of magnetic toner particles having a particle size of 8 to 12.7 μm, and 2.0% by volume or less of magnetic toner particles having a particle size of 16 μm or more. The present invention relates to an image forming method characterized in that the toner has a particle size distribution in which the volume average particle diameter is 4 to 10 μm.

The electrostatic image carrier according to the present invention is an organic photoconductive photoreceptor having a photosensitive layer containing at least a charge generating substance and a charge transporting substance on a conductive substrate, in which at least two kinds of compounds are used as charge generating substances. It is characterized by using a photoreceptor containing.

Compounds with spectral sensitivity in the visible light region (400 nm to 700 nm) and infrared region (70 Q nm to 90 (InII+
) and a compound with spectral sensitivity, and an organic photoconductive photoreceptor that uses a charge-transporting material whose ionization potential and electric potential match, and which has excellent sensitivity, residual potential, and charging characteristics. It can be used as an electrostatic image carrier with spectral sensitivity ranging from visible light to semiconductor laser light.

By using such an electrostatic image holder, it is possible to form an analog latent image using white reflected light from the document table and a digital latent image using a laser spot from a semiconductor laser or the like on the electrostatic image holder. can.

The compound having spectral sensitivity in the visible light region and the compound having spectral sensitivity in the infrared region are preferably mixed at a weight ratio of 5/1 to 115, preferably 371 to 1/3.

Examples of the charge generating substance include a combination of a bisazo pigment having an absorption peak on the short wavelength side and a bisazo pigment having an absorption peak on the long wavelength side.

Examples of bisazo pigments having an absorption peak on the short wavelength side include bisazo pigments having an oxadiazole ring as a central skeleton. For example, a bisazo compound having the following structural formula (1) may be mentioned.

R1: F, CI, Br, IR2: C
1(s, -C)+2(:)13...(1) As a bisazo pigment having an absorption peak on the long wavelength side, a bisazo pigment having a benzanthrone ring as a central skeleton or diphenyl-pyridine-2- Examples include bisazo pigments having ylamine as a central skeleton. Examples include bisazo pigments having the following structural formula (2) or (3).

As the charge transport substance, there is a triphenylamine compound having the following structural formula (4).

12 to 60% by number of magnetic toner particles with a particle size of 5 μm or less
containing magnetic toner particles with a particle size of 8 to 12,7 μm.
A magnetic toner containing 33% by number, 2.0% by volume or less of magnetic toner particles having a particle size of 16 μm or more, and a particle size distribution in which the volume average particle size of the magnetic toner is 4 to 10 μm is applied to the surface. The toner carriers to be carried are arranged with a certain gap in the developing section, and the magnetic toner is regulated to a thickness thinner than the gap on the toner carrier, and the magnetic toner is conveyed to the developing section.
By the developing method of developing the latent image, the digital latent image and analog latent image described above can be faithfully visualized, and a high-density image without fogging can be provided.

The magnetic toner according to the present invention can faithfully reproduce even the fine lines of the latent image formed on the photoreceptor,
It is also excellent in reproducing halftone dots and digital dot latent images, and can provide images with excellent gradation and resolution. Furthermore, even if you continue to copy or print out images, it will maintain high image quality, and even in the case of high-density images.
It is possible to perform good development with less toner consumption than conventional magnetic toners, and it has advantages in terms of economy and miniaturization of the copying machine or printer body.

The reason why such an effect is obtained in the magnetic toner according to the present invention is not necessarily clear, but it is presumed as follows.

One of the characteristics of the magnetic toner of the present invention is that magnetic toner particles having a particle size of 5 μm or less account for 12 to 60% by number. Conventionally, in magnetic toner, magnetic toner particles with a diameter of 5 μm or less are difficult to control the amount of charge, impair the fluidity of the magnetic toner, cause the toner to scatter and contaminate the machine, and are also components that cause image fogging. It was believed that it was necessary to actively reduce the number of

However, according to studies conducted by the present inventors, it has been found that magnetic toner particles of 5 μm or less are an essential component for forming high-quality images.

For example, changing the surface potential on the photoreceptor using a magnetic toner having a particle size distribution ranging from 0.5 μm to 30 μm,
Developing a latent image by changing the surface potential on the photoreceptor, from a large development potential contrast in which a large number of toner particles are easily developed, to a halftone, to a small development potential contrast in which only a few toner particles are developed,
When the developed toner particles on the photoreceptor were collected and the toner particle size distribution was measured, it was found that there were many magnetic toner particles with a diameter of 8 μm or less, and particularly a large number of magnetic toner particles with a diameter of 5 μI or less. When magnetic toner particles with a particle size of 5 μm or less, which is the most suitable for development, are smoothly supplied to develop the latent image on the photoreceptor, it is true to the latent image, does not protrude from the latent image, and has true reproducibility. It's a great way to change images.

One of the characteristics of the magnetic toner of the present invention is that the number of particles in the range of 8 to 12.7 μm is 1 to 33% by number. As mentioned above, this is related to the necessity of the presence of magnetic toner particles with a particle size of 5 μm or less. However, in the latent image itself, the electric field strength at the edges around the latent image is higher than at the center, so that the toner particles are thinner inside the latent image than at the edges.
Image density may appear thin. In particular, magnetic toner particles with a diameter of 5 μm or less have a strong tendency to do so. However, we found that toner particles in the range of 8-12.7 μm were
It has been found that this problem can be solved and the problem can be made even clearer by containing % by number to 33% by number. 8-1
This is thought to be because toner particles in the particle size range of 2.7 μm have a suitably controlled amount of charge compared to magnetic toner particles with a particle size of 5 μm or less, but the electric field strength is smaller than that at the edges of the latent image. A uniformly developed image is formed by supplying the toner particles to the inside to compensate for the lack of adhesion of the toner particles on the inside to the edges, resulting in a sharp image with high density and good resolution and gradation. is provided.

Further, it is preferable that the amount of magnetic toner particles having a particle size of 16 μm or more is 2.0% by volume or less, and is as small as possible.

The magnetic toner according to the present invention solves the conventional problems and can withstand the recent strict demands for high image quality by using a concept completely different from the conventional viewpoint.

The configuration of the present invention will be explained in more detail.

Magnetic toner particles with a particle size of 5 μm or less account for 17 to 17 of the total number of particles.
The content is preferably 60% by number, preferably 25 to 50% by number, and even more preferably 30 to 50% by number. If the number of magnetic toner particles with a particle size of 5 μm or less is less than 17%, there will be less effective magnetic toner particles for high image quality, and especially as the toner is used for continuous copying or printing, the effective magnetic toner particles will decrease. As the components decrease, the balance of the particle size distribution of the magnetic toner as shown in the present invention deteriorates, and the image quality gradually deteriorates.

If it exceeds 60% by number, magnetic toner particles tend to aggregate with each other, resulting in toner agglomerates with a particle size larger than the original particle size.
This results in rough image quality, lowers resolution, and increases the difference in density between the edges and the interior of the latent image, which tends to result in a hollow image.

The number of particles in the range of 8 to 12.7 μm is preferably 1 to 33% by number, preferably 8 to 20% by number.

When the amount is more than 33% by number, image quality deteriorates and more development than necessary (too much toner is applied) occurs, leading to an increase in toner consumption. On the other hand, if it is less than 1% by number, it becomes difficult to obtain high image density.

The amount of magnetic toner particles having a particle size of 16 μm or more is preferably 2.0% by volume or less, more preferably 1.0% by volume or less, and still more preferably 0.5% by volume or less.

If the amount is more than 2.0% by volume, it not only hinders fine line reproduction, but also causes coarse toner particles of 16 μm or more to protrude on the thin layer surface of toner particles developed on the photoreceptor during transfer. This makes the delicate state of close contact between the photoreceptor and the transfer paper via the toner layer irregular, causing fluctuations in transfer conditions and causing a defective transfer image. The volume average diameter of the magnetic toner is 4 to 10 .mu.m, preferably 4 to 9 .mu.m, and this value cannot be considered in isolation from the above-mentioned components. When the volume average particle diameter is less than 4 μm, in applications such as graphic images where the image area ratio is high, the amount of toner applied on the transfer paper is small, which tends to cause problems such as low image density. This is considered to be due to the same reason as the reason why the density inside the edge portion of the latent image decreases as described above. If the volume average particle diameter exceeds 10 .mu.m, the resolution will not be good, and even if copying is good at the beginning, image quality will tend to deteriorate with continued use.

FIG. 4 shows the slope of the image density with respect to the surface potential obtained by the developing method using a magnetic toner having a specific particle size distribution, which is a feature of the present invention.

As is clear from FIG. 4, since it has an appropriate slope, the analog latent image can be visualized faithfully in accordance with the potential, so that it is possible to obtain an image with gradation in halftone reproduction. There is good cutting from the vL section to the VI section, and there is no fogging even in the digital latent image. The cutting from the vH part to the VI) part is good, sufficient image density can be obtained in analog latent images and digital latent images, and density unevenness does not occur. As described later, the magnetic toner having a specific particle size distribution as in the present invention adheres well to the latent image, and it adheres uniformly, and a certain amount of magnetic toner is developed depending on the potential of the latent image. From vL to VH% In addition, it is possible to obtain an image with a sharp transition from vo to VD, no fog, high image density, and excellent halftone gradation reproducibility.

The magnetic toner used in the development step preferably has development characteristics that satisfy the conditions shown in FIG. 4 in terms of the relationship between the potential of the latent image and the image density.

Specifically, the difference (VL-H) between the latent image potential at which fogging can be visually confirmed and the latent image potential until the image density reaches 0.2.
100 V or less (tear') ; Image density is 0.2~
In the range of 0.8, the amount of change in image density (DH) per 10 V of latent image potential difference is less than 0.11 (preferably 0.10
latent image potential of image density 1.2 and image density of image density 1.3 or more (or maximum image density of image density 1.2 or more);
The difference (V, -O) from the latent image potential until it reaches is too
v or less: Latent image potential that allows visual fogging and image density of 1.3
The difference (VL-D) from the latent image potential until reaching the above image density (or the highest image density with an image density of 1.2 or more) is 400 V or less (more preferably 350 V or less, particularly preferably 300 V or less) It is preferable that a developing means having a magnetic toner satisfies the following development characteristics.

In the present invention, the latent image potential (Vo) of the black image area has an absolute value of 550 to 750V (preferably 600 to 700V).
) is preferred.

The measuring device is a Coulter counter TA-II type (
(manufactured by Coulter Inc.), an interface that outputs number distribution 1 volume distribution (manufactured by Nikkaki) and a Cx-1 personal computer (manufactured by Canon) are connected, and the electrolyte is 1% NaCJ using primary sodium chloride. ! Prepare an aqueous solution. As a measurement method, 100 to 150 ml of the above electrolytic aqueous solution was used.
0.1 to 5 mR of a surfactant (preferably an alkylbenzene sulfonate) as a dispersant is added to the solution, and 2 to 20 mg of a measurement sample is added thereto. The electrolytic solution in which the sample was suspended was dispersed for about 1 to 3 minutes using an ultrasonic disperser, and then dispersed using the Coulter Counter T^-If type using a 100 μ aperture as an aperture.
The particle size distribution of 40μ particles was measured and the value according to the present invention was determined.

Examples of the binder resin used in the magnetic toner according to the present invention include the following toner binder resins when a heated pressure roller fixing device having an oil coating device is used.

For example, monopolymers of styrene and its substituted products such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene; styrene-p-chlorostyrene copolymers, styrene-vinyltoluene copolymers, styrene-vinylnaphthalene copolymers , styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-methyl chloromethacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl Styrenic copolymers such as ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer; polyvinyl chloride, phenol Resin, natural modified phenolic resin, natural resin modified maleic acid resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin, polyester resin, polyurethane, polyamide resin, furan resin, epoxy resin, xylene resin, polyvinyl butyral, terpene resin, Coumarone indene resin and petroleum-based resin can be used.

In the heated pressurized roller runner method, in which little oil is applied, the so-called offset phenomenon, in which a part of the toner image on the toner image support member is transferred to the roller, and the adhesion of the toner to the toner image support member are important issues. be. Toners that are fixed with less thermal energy usually tend to block or cake during storage or in a developing device, so these problems must also be taken into consideration. The physical properties of the binder resin in the toner are most significantly involved in these phenomena. Furthermore, according to the research of the present inventors, when the content of magnetic material in toner is reduced,
At the time of fixing, the adhesion of the toner to the toner image supporting member is improved, but offset is more likely to occur, and blocking or caking is also more likely to occur. In the present invention, when using a heated pressure roller fixing method in which little oil is applied, the selection of the binder resin is more important.

Preferred binder resins include crosslinked styrenic copolymers and crosslinked polyesters.

Comonomers for the styrene monomer in the styrene copolymer include acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate,
Monocarbons with double bonds such as octyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, acrylonitrile, methacrinitrile, acrylamide Acids or substituted products thereof: dicarboxylic acids with double bonds such as maleic acid, butyl maleate, methyl maleate, dimethyl maleate, and substituted products thereof; vinyl esters such as vinyl chloride, vinyl acetate, vinyl benzoate ; Ethylene olefins such as ethylene, propylene, and butylene; Vinyl ketones such as vinyl methyl ketone and vinyl hexyl ketone; Vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, and vinyl isobutyl ether. These vinyls! One or more #mers are used.

As the crosslinking agent, a compound having two or more polymerizable double bonds is mainly used. Aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene, etc.; Carboxylic acid esters with two double bonds such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, and 1,3-butanediol dimethacrylate; divinylaniline, divinyl dimethacrylate, etc. Examples include divinyl compounds such as vinyl ether, divinyl sulfide, and divinyl sulfone; and compounds having three or more vinyl groups. These crosslinking agents may be used alone or as a mixture. The crosslinking agent is 0.01 per 100 parts by weight of
It is preferred to use ~5 parts by weight.

When using a pressure fixing method, it is possible to use a binder resin for pressure fixing toner, such as polyethylene, polypropylene, polymethylene, polyurethane elastomer,
Examples include ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, ionomer resin, styrene-butadiene copolymer, styrene-isoprene copolymer, linear saturated polyester, and paraffin.

In the magnetic toner of the present invention, it is preferable to use a charge control agent by blending it into the toner particles (internally adding it) or mixing it with the toner particles (externally adding it). The charge control agent makes it possible to optimally control the amount of charge depending on the developing system, and in particular, in the present invention, it is possible to further stabilize the balance between particle size distribution and charge. Examples of positive charge control agents include nigrosine and nigrosine modifications using fatty acid metal salts; quaternary ammonium salts such as tributylbenzylammonium-1-hydroxy-4-naphthosulfonate and tetrabutylammonium tetrafluoroborate;
dibutyltin oxide, dioctyltin oxide,
Examples include diorganotin oxides such as dicyclohexyltin oxide; diorganotin borates such as dibutyltinborate, dioctyltinborate, and dicyclohexyltinborate. These can be used alone or in combination of two or more. Among these, charge control agents such as nigrosine compounds and quaternary ammonium salts are particularly preferably used.

General formula [wherein R, represents H or C) 13, R2 and R
3 is a substituted or unsubstituted alkyl group (preferably C0
~C4) is shown. ] A monopolymer of 1,000 yen expressed by the following or a copolymer with a polymerizable monomer such as styrene, acrylic ester, or methacrylic ester as described above can be used as the positive charge control agent.

In this case, these charge control agents also function as (all or part of) a binder resin.

The above-mentioned charge control agent (one that does not function as a binder resin) is preferably used in the form of fine particles. In this case, the number average particle size of this charge control agent is specifically:
The thickness is preferably 4 μm or less (more preferably 3 μm or less).

When internally added to the toner, such a charge control agent is added in an amount of 0.1 to 20 parts by weight (or even 0.1 to 20 parts by weight) per 100 parts by weight of the binder resin.
．． 2 to 10 parts by weight) is preferably used.

Various additives may be added internally or externally to the 6n toner according to the present invention, if necessary. As the colorant, conventionally known dyes and pigments can be used, and usually 0.5 to 20 parts by weight may be used per 100 parts by weight of the binder resin. Other additives include, for example, lubricants such as zinc stearate; abrasives such as cerium oxide, silicon carbide; flow agents such as colloidal silica, aluminum oxide, or anti-caking agents such as carbon black, tin oxide, etc. There are conductivity imparting agents.

In order to improve the mold releasability during hot roll fixing, waxy substances such as low molecular weight polyethylene, low molecular weight polypropylene, microcrystalline wax, carnano (wax, Sasol wax, paraffin wax, etc.) are mixed with 0.0% based on the binder resin. Adding about 5 to 5 wt% to the magnetic toner is also one of the preferred embodiments of the present invention.

Further, the magnetic toner according to the present invention may contain a magnetic material, which may also serve as q90% of the colorant.

The magnetic materials contained in the magnetic toner of the present invention include iron oxides such as magnetite, γ-iron oxide, ferrite, and iron-rich ferrite; metals such as iron, co-metal, and nickel, or these metals and aluminum; cobalt, copper,
Examples include alloys with metals such as lead, magnesium, tin, zinc, antimony, beryllium, bismuth, cadmium, calcium, manganese, selenium, titanium, tungsten, ) (nadium) and mixtures thereof.

These ferromagnetic materials preferably have an average particle diameter of about 0.1 to 1 μm, preferably about 0.1 to 0.5 μm, and the amount to be contained in the magnetic toner is 100% by weight of the G-magnetic component. 60 to 120 parts by weight, preferably resin component 1
00 parts by weight, it is 65 to 110 parts by weight.

To prepare the magnetic toner for developing electrostatic images according to the present invention, magnetic powder, vinyl or non-vinyl thermoplastic resin, pigment or dye as a coloring agent, charge control agent, and other additives are used as necessary. etc. are sufficiently mixed using a mixer such as a ball mill, and then melted, kneaded, and kneaded using a heat kneader such as a heated roll, kneader, or extruder to disperse or dissolve the pigment or dye in the resin. The magnetic toner according to the present invention can be obtained by performing pulverization and strict classification after cooling and solidification.

Another method is to obtain a toner by dispersing constituent materials in a binder resin solution and then spray-drying; or by emulsifying and suspending a predetermined material by mixing the monomers that should constitute the binder resin. A polymerization toner manufacturing method in which a toner is obtained by polymerizing the liquid after it is made into a liquid; or a method in which a predetermined material is contained in the core material, the shell material, or both in a so-called microcapsule toner consisting of a core material and a shell material. The following methods can be applied.

The magnetic toner according to the present invention has an absolute value of triboelectric charge of 5 to 5.
It is preferable to have a triboelectric charging property of 20 μc/g (preferably 7 to 15 μc/g).

The triboelectric properties of magnetic toner are 50-60% at 25°C.
10g of magnetic toner left in R11 environment and 2
Main grain size (200 to 300 mesh (tiller))
Carrier iron powder (e.g., Nippon Iron Powder Co., Ltd. E
FV200/300) in a polyethylene container with a capacity of approximately 200 cm under the above-mentioned environment (by hand and shaking it up and down approximately 50 times), and then passed through a 400 mesh screen. The determination is made by measuring the amount of triboelectric charge of the magnetic toner using an ordinary blow-off method using an aluminum group cell.

The true density of the magnetic toner according to the present invention is 1.45 to 1.70.
87 cm', more preferably 1
．． It is 50 to 1.65 g/cm3. Within this range, the magnetic toner of the present invention having a specific particle size distribution is most effective in terms of high image quality and durability stability.

When the true density of the magnetic toner is less than 1.45, the weight of the magnetic toner particles themselves is too light, which tends to cause reversal fog, crushing of thin lines due to excessive coverage of toner particles, scattering, and deterioration of resolution. True density of magnetic toner1.
If it is higher than 70, the image density will be distorted and the image will lack sharpness such as broken thin lines, and the magnetic force will also be relatively large, so the toner spikes will tend to become long or branched. When the image is developed, it tends to disrupt the image quality and result in a rough image.

The true density of magnetic toner can be measured by several methods, but in the present invention, when measuring fine powder, the following method is adopted as an accurate and simple method.

A stainless steel cylinder with an inner diameter of 10+ nm and a length of about 5 cm, a disk (A) with an outer diameter of about 10 mm and a height of 5 mm that can be inserted tightly into the cylinder, and an outer diameter of about 10 mm and a length of about 8 cm.
Prepare the piston (B). At the bottom of the cylinder is a disk (
A), then about 1 g of the sample to be measured, and gently push the piston (B). A force of 400 kg/cm2 was applied to this using a hydraulic press, and the product was compressed for 5 minutes and taken out. Weigh the compressed sample fi (wg)
Diameter of sample compressed with simicrometer (Dcm)
, the height (L cm) is measured, and the true density is calculated by the following formula.

In order to obtain even better development characteristics, the magnetic toner of the present invention has a residual magnetization Or of 1 to 5 emu/g%, preferably 2 to 4.5 emu/g, and a saturation magnetization 01 of 20 to 4.5 emu/g.
It is preferable that the magnetic field is 40 emu/g and the coercive force Hc satisfies the magnetic properties of 40 to 100 nisted (6°).

(In both cases, the measured magnetic field is IKO.) Fine silica powder may be added internally or externally to the magnetic toner of the present invention, but it is more preferable to mix it externally. In a magnetic toner having a particle size distribution as a feature of the present invention,
The specific surface area is larger than that of conventional toners. When magnetic toner particles are brought into contact with the surface of a cylindrical conductive sleeve having a magnetic field generating means inside for frictional IF electricity, the number of times the toner particle surface contacts the sleeve increases compared to conventional magnetic toner. Toner particles are more likely to wear out. When the magnetic toner according to the present invention is combined with fine silica powder, wear is significantly reduced due to the presence of the fine silica powder between the toner particles and the sleeve surface. As a result, the life of the magnetic toner can be extended, and stable charging properties can also be maintained, making it possible to obtain a developer having a magnetic toner that is more excellent in long-term use.

As the silica fine powder, both silica fine powder produced by a dry method and a wet method can be used, but from the viewpoint of filming resistance and durability, it is preferable to use a silica fine powder produced by a dry method.

The dry method mentioned here is a method for producing fine silica powder produced by vapor phase oxidation of a silicon halide compound. For example, this method utilizes the thermal decomposition oxidation reaction of silicon tetrachloride gas in oxygen and hydrogen, and the basic reaction formula is as follows.

5iC1'4+ 2 B□+02→5i(h+48Cρ
In this manufacturing process, for example, aluminum chloride or
It is also possible to obtain a composite fine powder of silica and other metal oxides by using other metal halide compounds such as titanium chloride together with the silicon halide compound, and these are also included.

Commercially available fine silica powder produced by vapor phase oxidation of a silicon halogen compound used in the present invention includes, for example, those commercially available under the following trade names.

AERO5IL 130 (Japan Aerosil Co., Ltd.) 200 x50 T600 0X80 OX170 CO to 84 Ca-0-5iL
M-5 (f; ABOTOGo, Inc.)
MS-7S-5 H-5 Wacker HDK N 20
V 15 (CKER-CHEM to W
IE GMBH) N20ED-CF
ine 5ilica (Dow Corning, Inc.) Fransol (Fransi 1, Inc.) On the other hand, various conventionally known methods can be applied to the method of producing the silica fine powder used in the present invention by a wet method.

For example, the general reaction formula for the decomposition of sodium silicate with an acid is shown below.

Na, (lXsi02+1(Cffi+1(20-e
sio2・nH2O+NaC1) In addition, decomposition of sodium silicate with ammonia salts or alkali salts,
A method in which an alkaline earth metal silicate is generated from sodium silicate and then decomposed with an acid to form silicic acid, a method in which a sodium silicate solution is converted into silicic acid using an ion exchange resin,
There are methods that use natural silicic acid or silicates.

The silica fine powder referred to herein can be any of anhydrous silicon dioxide (silica) and other silicates such as aluminum silicate, sodium silicate, potassium silicate, magnesium silicate, and zinc silicate.

Commercially available fine silicic acid powders synthesized by a wet method include those sold under the following trade names, for example.

Carplex Shionogi & Co. Neve Seal Nippon Silica Toku Seal, Fine Seal Tokuyama Soda Vita
Seal Multi-wood Fertilizer, Silnex Mizusawa Chemical Star
SIL KAMIJIMA CHEMICAL HI
Medicines Lloyd Ehime Yakuhin Fuji Davison Chemical H4-5il (Hiseal) Pittsburgh Plate Glass, G
.

(Pittsburgh Plate Glass) Durosll ()'Urosil) Llltorasil (Ultra Seal) Fiil
lstoff-Gesellschaft Marq
uart Manosil Hardman and tlolden 11oesch Chemische Fabrlk Hoesch
Ni-G (Hiemische Fabrik Herras)
Sil-5tone Stone
r Rubber Co, (stoner rubber) Nalco (Nalco) Nalco (:hem, C.

(Narcochemical) Quso (shoes) Philadelphia Quartz (Philadelphia Go.

Rion) Imsil 1111nols Minerals Co.

(Illinois Mineral) Calcium 5ilikat (Calcium Silicate) Chemische Fabrik Hoe
sch, ni-G (Hiemische Fabrik Herrsch) Calsil (Calsil) Fiillstoff-Gesellschaft
Marquard Fortafil Imperia
l Che+n1cal Industries, L
td.

(Imperial Chemical Industries) Microcal Joseph Crosfields & 5on
s Ltd.

(Joseph Crossfield Samp) And Vulkasil Farbenfabriken Bryer, A
,-G.

(Falpen Fabricen Bayer) Tufknit
(Toughknit) Durham Chemicals, Ltd.

(Durham Chemicals) Among the silica fine powders mentioned above, the specific surface area due to nitrogen adsorption measured by the BET method is 3011127 g or more (especially 50-4
00 m2/g) gives good results. Magnetic toner 1oo! ! Silica fine powder is 0 for the total amount.
．． 0.01 to 8 parts by weight, preferably 0.1 to 5 parts by weight.

When used as a positively charged magnetic toner like the magnetic toner according to the present invention, positively charged silica fine powder is used rather than negatively charged silica fine powder added to prevent toner wear. It is preferable to use it because it does not impair charging stability.

As a method for obtaining positively chargeable silica fine powder, the above-mentioned untreated silica fine powder is added with at least one nitrogen atom in the side chain.
There is a method of treatment with a silicone oil having more than one organo group, a method of treatment with a nitrogen-containing silane coupling agent, or a method of treatment with both.

In the present invention, positively charged silica refers to silica that has a positive tribocharge relative to the iron powder carrier when measured by a blow-off method.

As the silicone oil having a nitrogen atom in the side chain used in the treatment of silica fine powder, a silicone oil having at least a partial structure represented by the following formula can be used.

(In the formula, R1 represents hydrogen, an alkyl group, an aryl group, or an alkoxy group, R2 represents an alkylene group or a phenylene group, R5 and R4 represent hydrogen, an alkyl group, or an aryl group, and R5 represents a nitrogen-containing heterocyclic ring. group) The above alkyl group, aryl group, alkylene group.

The phenylene group may have an organo group having a nitrogen atom, and may also have a substituent such as a halogen within a range that does not impair chargeability. The silicone oil is preferably used in an amount of 0.1 to 100 parts by weight per 100 parts by weight of silica.

The nitrogen-containing silane coupling agent used in the present invention generally has a structure represented by the following formula.

R1, l-5t-Y.

(R represents an alkoxy group or a halogen, Y represents an amino group or an organo group having at least one nitrogen atom, m and n are integers of 1 to 3, and m+n
=4. ) Examples of the organo group having one or more nitrogen atoms include an amino group having an organic group as a substituent, a nitrogen-containing heterocyclic group, or a group having a nitrogen-containing heterocyclic group.Nitrogen-containing heterocyclic group Examples of the unsaturated heterocyclic group include unsaturated heterocyclic groups and saturated heterocyclic groups, and known ones are applicable. Examples of the unsaturated heterocyclic group include the following.

Examples of the saturated heterocyclic group include the following.

The heterocyclic group used in the present invention is preferably a five-membered ring or a six-membered ring in consideration of stability.

Examples of such treatment agents include aminopropyltrimethoxysilane, aminopropyltriethoxysilane, dimethylaminopropyltrimethoxysilane, diethylaminopropyltrimethoxysilane, dipropylaminopropyltrimethoxysilane, dibutylaminopropyltrimethoxysilane. , monobutylaminopropyltrimethoxysilane, dioctylaminopropyltrimethoxysilane, dibutylaminopropyldimethoxysilane, dibutylaminopropylmonomethoxysilane, dimethylaminophenyltriethoxysilane, trimethoxysilyl-γ
-Propylphenylamine, trimethoxysilyl-γ-
There is propylbenzylamine. Further, as the nitrogen-containing heterocycle, those having the structure described above can be used, and examples of such compounds include trimethoxysilyl-γ-propylpiperidine, trimethoxysilyl-γ-propylmorpholine, trimethoxysilyl-γ-propyl There is imidazole. The nitrogen-containing silane coupling agent is preferably used in an amount of 0.1 to 100 parts by weight per ioo parts by weight of silica.

The application amount of these treated positively charged silica fine powders is
0.01 to 100 parts by weight of positively charged magnetic toner
The effect is exhibited when the amount is 8 parts by weight, particularly preferably 0.1
When added in an amount of up to 5 parts by weight, it exhibits positive chargeability with poor stability. Regarding the form of addition, the preferred form is 0.1 to 100 parts by weight of positively charged magnetic toner.
It is preferable that 3 parts by weight of the treated silica fine powder be attached to the surface of the toner particles. The untreated fine silica powder described above can also be used in similar dosages.

The silica fine powder used in the present invention may be treated with a silane coupling agent or a treatment agent such as an organosilicon compound for the purpose of hydrophobization, if necessary. Examples of such treatment agents include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allyl phenyldichlorosilane, and benzyldimethylchlorosilane. , bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane,
Chlormethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilylacrylate, vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyljethoxysilane, hexamethyldisiloxane, 1,3-divinyltetramethyldisilane siloxane, l,3-diphenyltetramethyldisiloxane,
and dimethylpolysiloxane, which has 2 to 12 siloxane units per molecule and contains one Si-bonded hydroxyl group in each unit located at the end. One or two of these f! Used in mixtures of 11 or more. The above-mentioned hydrophobizing agent is based on 100 parts by weight of silica,
It is preferable to use 0.1 to 100 parts by weight.

In the magnetic 1-ner according to the present invention, fine powder of a fluorine-containing polymer may be added internally or externally. Examples of the fluorine-containing polymer fine powder include fine powder of polytetrafluoroethylene, polyvinylidene fluoride, and tetrafluoroethylene-vinylidene fluoride copolymer. In particular, polyvinylidene fluoride fine powder is preferred in terms of fluidity and polishability. The amount added to the toner is O,QL ~2. Q wt%, especially Q, 02~
1. Q wt% is preferred.

In particular, in magnetic toners in which fine silica powder is mixed with the above-mentioned fine powders and externally added, the state of the silica attached to the toner is stabilized, and the attached silica is released from the toner, although the reason is not clear. The effect on toner abrasion and sleeve staining does not decrease, and it is possible to further increase charging stability.

An example of a specific apparatus that can be used to carry out the developing step in the present invention is shown in FIG.

The magnetic toner according to the present invention is preferably applied to a method of developing a latent image while flying the toner from a toner carrier such as a cylindrical sleeve to a latent image carrier such as a photoreceptor. The magnetic toner is given a triboelectric charge mainly through contact with the sleeve surface, and is applied in a thin layer onto the sleeve surface.

The thickness of the thin layer of magnetic toner is formed to be thinner than the gap between the photoreceptor and the sleeve in the development area. When developing a latent image on the photoreceptor, it is preferable to apply an alternating electric field between the photoreceptor and the sleeve and cause the magnetic toner having triboelectric charges to fly from the sleeve to the photoreceptor.

Examples of the alternating electric field include a pulsed electric field, an alternating current bias, or a combination of an alternating current and a direct current bias.

In the developing device shown in FIG. 5, for example, the non-magnetic sleeve 2-1, which is the toner carrier according to the present invention, has a diameter of 50 m/m.
Using m stainless steel sleeve (StlS 304),
Magnetic pole of magnet 4 in sleeve N, = 850 Gauss, N2 = 500 Gauss, S, = 650 Gauss, 52
= 500 gauss, the blade la is made of iron, which is a magnetic material, and the gap between the blade 1a and the sleeve 2-1 is 250 gauss.
μ, the toner 10 uses a magnetic toner bias power supply 11 according to the present invention in which DC is superimposed on AC, and Vp
p=1200V, f=800()12), D
An example is an apparatus in which C=+100W. Another example is one in which the shortest distance between the sleeve 2 and the latent image holder 9 is set to 300μ.

In the image forming method of the present invention, by using a toner carrier that carries magnetic toner on its surface, the surface of the toner carrier is made into a rough surface with a specific unevenness by sandblasting with irregularly shaped particles. A good toner coating state can always be maintained over a long period of time with no unevenness on the surface of the toner carrier. The target surface is one in which numerous minute incisions or protrusions are formed in random directions over the entire surface of the toner carrier.

However, in a developing device using a toner carrier having such a specific surface condition, depending on the applied magnetic toner, the toner or components in the toner may adhere to the surface, causing contamination on the surface of the toner carrier. As a result, a decrease in the density of the initial image may occur.

This is because components in the toner adhere to the slopes of the convex portions and concave portions of the surface of the toner carrier, resulting in insufficient charging of the magnetic toner particles and a decrease in the amount of charge in the toner layer.

A good way to prevent or reduce contamination of the magnetic toner carrier is to make the surface of the toner carrier smoother.

In the magnetic toner carrier of the developing method according to the present invention,
When the surface has a specific unevenness formed by a plurality of spherical trace depressions, toner components are difficult to adhere to the surface, and contamination can be prevented or reduced over a long period of time, and the magnetic toner can be transferred to the toner carrier. It was also excellent in its ability to coat surfaces uniformly with toner.

A toner carrier having such a surface shape is also excellent in triboelectric charging ability, and can fully bring out the triboelectric charging ability of the magnetic toner according to the present invention and stabilize the charging property.

Therefore, the followability of the electrostatic latent image to the potential is further improved, and a fine-grained and moist image with excellent gradation for halftones can be obtained.

The sharpness of the potential-concentration curve to the vL portion is also improved, and it is more effective against fogging.

The toner carrier is hereinafter referred to as a sleeve.

A blasting method using regular particles can be used to obtain a sleeve surface having an uneven surface formed by a plurality of spherical trace depressions.

As the regular particles, for example, rigid spheres made of metals such as stainless steel, aluminum, steel, nickel, and brass, or rigid spheres such as ceramics, plastics, and glass beads having a specific particle size can be used. By blasting the sleeve surface using regular particles having a specific particle size, it is possible to form a plurality of spherical trace depressions with approximately the same diameter R.

The diameter R of the plurality of spherical trace depressions on the sleeve surface is 20 to 2
507zm is preferable, more preferably 30-200μ
m, and if the diameter R is less than 20 μm, there is a tendency for contamination by components in the magnetic toner to increase; conversely, if the diameter R is more than 250 μm, the uniformity of the toner coat on the sleeve tends to decrease. It is in.

Therefore, it is preferable that the regular particles used during the blasting treatment of the sleeve surface have a diameter of 20 to 250 μm.

Furthermore, the pitch P of unevenness on the sleeve surface and the surface roughness d
The surface of the sleeve was measured using a micro surface roughness meter (sold by Koita Research Institute, etc.), and the surface roughness d was based on JIS 10-point average roughness (RZ) rJIS B 0601J.

As shown in Figure 6, the straight line parallel to the average line of the section cut out by the standard length I from the cross-sectional curve passes through the third peak from the highest one, and the one that passes through the bottom of the third valley from the deepest one. The distance between two straight lines is expressed in micrometers (μl11), and the reference length It is assumed to be 0.25 mm.

Pitch P is a standard length of 0.25 mm, where the height of the convex part is 0.1μ or more with respect to the concave parts on both sides, which is counted as one peak.
It is calculated as follows based on the number of mountains in .

[250 (μ)] / [Number of peaks included in 250 (μ) (μ) The pitch P of the unevenness on the surface of one sleeve is 2 to 10
0 μm is preferable, and more preferably 10 to 80 μm. If P is less than 2 μm, sleeve contamination due to components in the magnetic toner tends to increase. Conversely, if P exceeds 100 μm, contamination on the sleeve tends to increase. The uniformity of the toner coat tends to decrease. Surface roughness d of unevenness on sleeve surface
is preferably 0.1 to 5 μm, more preferably 0.5 to 5 μm.
4 μm, and when d exceeds 5 μm, in a method of developing by applying an alternating voltage between the sleeve and the latent image holder to cause the magnetic toner to fly from the sleeve side to the latent image surface, The electric field tends to concentrate on the uneven portions, causing image disturbance. Conversely, if d is less than 0.1 μ, the uniformity of the toner coat on the sleeve tends to decrease.

FIG. 7 shows an example of a specific apparatus that can be used to carry out the image forming method of the present invention.

The process of forming an electrostatic latent image on the photoreceptor 30 will be explained. −
After the photoreceptor 30 is charged by the charger 29, the original 21
is irradiated with a halogen lamp or fluorescent lamp 24, and the reflected light IA is imaged on the photoreceptor 30 by the lens group 26 and the reflection mirror 25 to form an analog latent image. An electrical signal output from a keyboard, an external device, or image information obtained from a document is processed by an image processing section 39, and the electrical signal is input to a laser scanner 27, and a laser beam I is generated. is irradiated onto the photoreceptor 30 to form a digital latent image.

The latent images formed in this way are simultaneously developed in the developing device 31 using the above-described developing process, and are visualized. Photoreceptor 3
The toner image formed on the toner image is transferred to a transfer material 38 by a transfer charger 35, and then the transfer material 38 is separated from the photoreceptor 30 and fixed by a fixing device 37 to obtain an image.

The photoreceptor 30 is cleaned of residual toner after transfer in a cleaner section 33 and is neutralized by a pre-exposure lamp 28, and is used repeatedly.

[Example] The present invention will be specifically explained below using examples.

All parts in the following formulations are parts by weight.

111 The image forming apparatus used for image formation will be described with reference to FIG.

The photosensitive drum 30 used will be explained. 75% tin oxide containing 10% antimony oxide compared to titanium oxide
% of the conductive powder coated with 100 parts of resol type phenolic resin, 30 parts of methanol, and 100 parts of methyl cellosolve, and the paint was thoroughly dispersed with a ball mill in an 80φ x 380mm aluminum cylinder. Dip coating onto a certain substrate, 140℃
, and was heated and cured for 30 minutes to form a 20 μm conductive undercoat layer. On top of this, polyamide resin [quaternary nylon (6-6B
-610-12) 11 parts and 3 parts of 8-nylon resin (methoxymethylated 6-nylon, methoxylation rate approximately 30%) were dissolved in a solvent consisting of 50 parts of methanol and 40 parts of butanol, and a coating solution was applied by dip coating. An intermediate layer having a thickness of 0.5 μm was provided. 2.5 parts of the disazo pigment represented by formula (1) and i and o parts of the disazo pigment represented by formula (5) Polyvinylbenzal resin... (1) ([n = 85,000. 80)
2 parts and 100 parts of cyclohexanone were dispersed for 2 hours in a sand mill using 1φ glass beads. Add 40 to 80 parts of tetrahydrofuran and 4 parts of methyl ethyl ketone to this dispersion.
Add 0 to 80 parts as appropriate to dilute to make a coating solution, apply it on the intermediate layer and dry at 80°C for 10 minutes to obtain 250 mg/IQ.
A charge generation layer having a thickness calculated by weight of 2 was formed.

Next, bisphenol Z type car recarbonate resin (Mn
22,000), dispersed in a stainless steel ball mill for 50 hours with 5 parts of polytetrafluoroethylene powder, 40 parts of monochlorobenzene, and 15 parts of THF as fluorine-containing resin powder, and charge transport was added to the resulting dispersion. A solution containing 10 parts of the stilbene compound shown in formula (6) (hereinafter referred to as the blank) as a substance was applied onto the charge generation layer and heated at 120°C.
The mixture was dried with hot air for 1 hour to form a charge transport layer with a thickness of 25 μm.

The thus obtained photoreceptor 3o was mounted on an image forming apparatus.

The spectral sensitivity of this photoreceptor is shown in FIG. The measurement was carried out using Vapor Analyzer 5P-428 (newly manufactured by Kawaguchi Electric Co., Ltd.). The laser scanner 27 uses a 78-on [11 semiconductor laser to scan 254-
It was set to have the scanning line density of DPI.

The potential of the VD section is set to -700V by the primary charger 29, and the amount of reflected light of the halogen lamp irradiation light from the white part of the document is set to 1.51) ux-sec, and the potential of the VL section is set to -200V.
It was set to be V. Laser output 1.2μJ/c
m' was set so that the average potential of the vL portion was 1200 . Through the above steps, an analog latent image and a digital latent image can be formed on the photoreceptor 30.

The developing conditions will be explained with reference to FIG.

The magnetic toner is applied in a thin layer onto the surface of the stainless steel cylindrical sleeve 2 via the magnetic blade 1a.
The gap between the blade 1a and the blade 1a was set to about 250 μm, and a toner layer with a thickness of about 90 μm was formed. The sleeve 2 has a fixed magnet 4 as a magnetic field generating means, and a magnetic field 100 is generated near the sleeve surface in the developing area adjacent to the photosensitive drum 9 provided with the organic photoconductive layer having the aforementioned negatively charged latent image.
The fixed magnet 4 forms 0 Gauss. The closest distance between the photosensitive drum 9 and the sleeve 2 rotating in the direction of the arrow is approximately 30
It was set to 0μI. Between the photosensitive drum 9 and the sleeve 2, an AC bar i'7 of 2000Hz/1350Vp,
and a DC bias of 250 μm were applied in combination.

Toner carrier is stainless steel sleeve (s11s304)
Using #300 carborundum as irregularly shaped particles, the surface was sprayed with a nozzle diameter of 7φ and a distance of 111100m+n
, air pressure 4 kg/cm2. Blasting was performed for 2 minutes.

The above-described latent image was visualized using the above-described developing device, and the toner image on the photoreceptor 30 was transferred onto a transfer material and fixed, thereby obtaining an image.

Next, the image evaluation method according to the present invention will be described.

In analog images, fine line reproducibility was measured using the following method. Using an image of an original document with thin lines exactly 100 μm in width as a copy under appropriate copying conditions as a sample for measurement, we used a Luzex 450 Particle Analyzer as the measuring device to measure the line width using an indicator from the enlarged monitor image. I do. At this time, since the line width measurement position has irregularities in the width direction of the fine line image of the toner, the average line width of the irregularities is taken as the measurement point. From this, the value (%) of fine line reproducibility is calculated using the following formula.

The resolution was measured by the following method. A pattern consisting of 5 thin lines with equal line width and spacing, 2.8.3.2.3.6.4.0.4.5.5.0 within 1 ma+
゜Create an original image that appears to have 5.8.8.3.7.1 or 8.0 lines. Observe with a magnifying glass the image obtained by copying the original document with line images of 1Ofi type under appropriate copying conditions, and calculate the resolution value by calculating the number of images (wood/mm) in which fine lines are clearly separated. do.

The larger this number, the higher the resolution.

Line representation and resolution of digital images were measured using the following method.

1 dot, 1 space line (101]tLm) is 5
A laser was used to create a latent image on the photoreceptor, and the resulting image was used as a measurement sample. The resolution is this 5 trees/
Evaluation was made based on aV line resolution.

Also, the line expression is a line with 1 dot and 2 spaces (1
00 μm) formed into a four-tree tree, the value is calculated using the following formula in the same manner as in the case of analog images.

The magnetic toner was prepared as follows.

The dot expression was measured by the method shown below. 1
A checkered latent image consisting of dots, 2 dots, 3 dots, and 4 dots was formed on a photoreceptor using a laser, and the resulting image was used as a measurement sample.

This sample is observed with a magnifying glass (30 times), and the number of dots in the image taken to clearly confirm the checkered pattern is expressed as a dot representation. The smaller this number is, the better the dot representation is.

In the image formation test, we made it possible to obtain digital and analog images simultaneously using the following method. A solid black area was provided in the original document, and a digital latent image was formed using a laser on the solid black area formed on the photoreceptor. The analog latent image and digital latent image thus obtained were developed and visualized to obtain an image having an analog part and a digital part.

After thoroughly mixing the above materials in a blender, they were kneaded in a twin-screw kneading extruder set at 150°C.

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 is strictly classified and removed at the same time to remove ultrafine powder and coarse powder using a multi-division classification device (elbow jet classifier manufactured by Tamu Mining Co., Ltd.) that utilizes the Coanda effect, resulting in positively charged black fine powder (magnetic toner). Table 1 shows the particle size distribution of this magnetic toner.

To 100 parts of the obtained black fine powder magnetic toner was added 0.0% of positively charged hydrophobic dry silica (BET specific surface area 2oam2/g).
6 parts were added and mixed in a Henschel mixer.

This magnetic toner was put into the above-mentioned image forming apparatus and an image reproduction test was carried out. This test was repeated 5000 times, and the results are shown in Table 2 for the analog image portion and Table 3 for the digital image portion.

As is clear from these tables, good images with no fogging were obtained in both the analog and digital sections, and the line expression, halftone dot expression, and gradation were also excellent. FIG. 9 shows the relationship between the surface potential of the drum and the image density. This uses a gray scale to adjust the illuminance of a halogen lamp, places various charges on the drum, and measures the surface potential of that area. Then, each potential was developed and the image density was determined.

Examples 2 and 3 Instead of the magnetic toner used in Example 1, a positively charged magnetic toner having a particle size distribution as shown in Table 1 was produced by changing the amount of magnetic material added and controlling the pulverization and classification conditions. An image reproduction test was carried out in the same manner as in Example 1 except for the use. The results are shown in Tables 2 and 3, and clear images were obtained for both analog and digital images.

15.1 Table 1 shows the particle size distribution of positively charged magnetic toner obtained using the above materials in the same manner as in Example 1.

Furthermore, as in Example 1, positively charged hydrophobic silica was externally added.

An image printing test was conducted using the same image forming apparatus as in Example 1, except that the magnetic toner carrier sleeve shown below was used.

The surface of the stainless steel sleeve (SO5304) was sprayed using glass beads with a diameter of 80% or more of 53 to 62 μm as regular particles, and a spray nozzle with a diameter of 7φ and a length of 111 mm.
+nm.

Blasting was performed under the conditions of air pressure of 4 kg/cm for 2.2 minutes, and the diameter R of the plurality of spherical trace depressions was 53 to 62.
Irregularities of μm were formed. The pitch P of the unevenness on the surface of this sleeve was 33μ, and the surface roughness d was 2.0μ.

The results are shown in Tables 2 and 3.

As is clear from this table, images with high density and no fogging were obtained, and the image quality was also excellent.

Examples 5 and 6 Using the raw materials used in Example 4, the amount of magnetic material.

An imaging test was carried out in the same manner as in Example 4, except that a positive-Iff' electromagnetic toner having a particle size distribution as shown in Table 1 was used by controlling the fine pulverization and classification conditions. The results are shown in Tables 2 and 3. Both analog and digital images were of excellent quality.

Comparative Example 1 In the magnetic toner used in Example 1, 60% of magnetic iron oxide was added.
Magnetic toners having particle size distributions shown in Table 1 were obtained in the same manner using the same materials except for the above. Furthermore, positively charged hydrophobic dry silica (BET 2
0.00 m'/g) was added and mixed using a Henschel mixer. This magnetic toner was subjected to the same image reproduction test as in Example 1, and the results are shown in Tables 2 and 3.

Line expression, dot expression, and resolution were poor, and there was fog in the digital image area, and halftones were rough in the analog image area.

Comparative Examples 2 to 4 Example 4 was used except that the coarsely crushed products obtained in Examples 1 to 6 were used, and a toner having a particle size distribution as shown in Table 1 was used by controlling the fine pulverization and classification conditions. A similar image reproduction test was conducted.

The results are shown in Tables 2 and 3.

In Comparative Example 2, fogging in the digital section, In Comparative Example 3, lines and dots were crushed due to excessive application. In Comparative Example 4, there was fog; A good image could not be obtained.

Comparative Example 5 The following photosensitive drums were installed in the image forming apparatus of Example 4. A photosensitive drum was prepared in the same manner as in Example 4 except that the compound represented by formula (1) was removed. The magnetic toner used in Example 4 was charged into this image forming apparatus, and an image reproduction test was conducted. The results are shown in Tables 2 and 3.

The sensitivity of the analog section was not high enough to obtain a good image, but there were no problems with the digital section.

The physical properties of Examples 1 to 6 and Comparative Examples 1 to 4 described above are shown in Table 4, and the development characteristics are shown in Table 5.

(Left below) A latent image was developed in the same manner as in Example 1, except that a photosensitive drum was produced using bisazo pigment (3) instead of bisazo pigment (5). Good results similar to those in Example 1 were obtained.

[Brief explanation of the drawing]

FIG. 1 shows a cross-sectional view of a developing device using a magnetic blade, FIGS. 2, 3, and 4 show explanatory diagrams of the relationship between image density and potential on the surface of the photoreceptor, and FIG. , shows a schematic explanatory diagram of a developing device according to the present invention, FIG. 6 shows a schematic explanatory diagram of the definition of surface roughness and pitch, and FIG. 7 shows a schematic explanatory diagram of an image forming apparatus according to the present invention, FIG. 8 shows the spectral sensitivity of the photosensitive drum according to the present invention, and FIG. 9 shows a graph plotting the relationship between image density and surface potential of the photosensitive drum obtained in the image forming apparatus according to the present invention.

Claims (2)

[Claims] (1) A certain gap is provided between an electrophotographic organic photoreceptor that contains at least two or more charge-generating substances and holds digital and analog electrostatic images, and a toner carrier that carries magnetic toner on its surface in a developing section. A developer used in an image forming method in which magnetic toner is arranged on a toner carrier to a thickness thinner than the gap and transported to a developing section for development, and the magnetic toner has a thickness of 5 μm or less. Contains 12 to 60% by number of magnetic toner particles with a particle size of 8 to 12.7 μm.
Contains 1 to 33% by number of magnetic toner particles with a particle size of 16
A developer for electrostatic image development, characterized in that it contains 2.0% by volume or less of magnetic toner particles having a particle size of .mu.m or more, and has a particle size distribution in which the volume average particle diameter of the magnetic toner is 4 to 10 .mu.m. (2) A certain gap is provided between the electrophotographic organic photoreceptor containing at least two or more charge-generating substances and holding digital and analog electrostatic images and the toner carrier carrying magnetic toner on its surface in the developing section. In an image forming method in which magnetic toner is arranged on a toner carrier to a thickness thinner than the gap and transported to a developing section for development, the magnetic toner is magnetic toner particles having a particle size of 5 μm or less. 12～
60% by number, 1 to 33% by number of magnetic toner particles with a particle size of 8 to 12.7 μm, and 2.0% by volume or less of magnetic toner particles with a particle size of 16 μm or more. An image forming method characterized by having a particle size distribution having a volume average particle diameter of 4 to 10 μm.