JPH07109524B2 - Developer for electrostatic image development and image forming method - Google Patents

Description

TECHNICAL FIELD The present invention relates to an image forming method having a step of developing an electrostatic latent image formed in an electrophotographic method, an electrostatic printing method or the like with a magnetic toner. .

[Prior Art] Conventionally, as a method for forming an electrostatic latent image, an analog method in which a document is irradiated with an exposure means such as a halogen lamp and reflected light is imaged on an electrostatic latent image holder, and a laser beam are used. , L
There is a digital system in which an ED light or the like is directly irradiated onto the electrostatic latent image holder to form a latent image.

A novel developing method using a one-component magnetic toner for developing these electrostatic latent images has been proposed, for example, in JP-A-55-18656 and JP-A-55-18659. 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 each other without contacting the latent image carrier. In the method, the insulating magnetic toner is transferred from the toner carrier to the latent image carrier to develop the electrostatic latent image.

At the time of development, an alternating voltage is applied between the toner carrier and the substrate conductor of the latent image carrier to reciprocate the toner between the toner carrier and the latent image carrier so that there is no background fog and gradation. And excellent development can be performed without thinning of the image edge portion. In this developing method, the toner is an insulator, so electrostatic transfer is easy.

As a method of forming the toner layer on the toner carrier, there is a method of using a coating blade at the outlet of the toner container.
For example, in the structure shown in FIG. 1, a blade 1a made of a magnetic material is provided at a position facing one magnetic pole N1 of a fixed magnet 4 incorporated in the toner carrier 2, and a magnetic force line between the magnetic pole and the magnetic blade is provided. The magnetic toner is erected along the edges of the magnetic toner, and the ears of the magnetic toner are cut at the edge portion of the blade tip to control the thickness of the toner layer by utilizing the action of the magnet (for example, JP-A-54-43037). See the bulletin).

In FIG. 1, 7 is a developing device containing a toner 10, 9 is a latent image holding member such as a photosensitive drum in an electrophotographic method or an insulating drum in an electrostatic recording method (hereinafter referred to as a photosensitive member or a photosensitive drum). ) Is shown.

The formation method is different between the analog latent image and the digital latent image, and the surface potential of the latent image suitable for development with respect to these latent images also differs. In the method of carrying out both the analog and digital development intended by the present invention, and especially in the method of performing both of them in one pass, there are many problems which have not been known so far.

The digital latent image is formed by charging the electrostatic latent image carrier and reducing 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, only one of the potentials needs to be developed. By the way, normal development is a case where toner is attached to the high potential portion (V _D portion) for development, and reverse development is a case where low potential portion is developed.

The case of regular development will be described below.

When the low potential portion is set to the bright portion potential (V _L ) and the high potential portion is set to the dark portion potential (V _D ), the _VL portion is visualized as a white image and the V _D portion is visualized as a black image. In this development, only the V _D portion needs to be developed, but when the V _L portion is developed, it appears as a fog. The _VL portion lowers the surface potential by an exposure means such as a laser spot, but in reality, the potential between the spots does not sufficiently decrease, and the surface potential of the _VL portion varies. Therefore, a portion having a high electric potential is generated in the _VL portion, and there is a possibility that the portion is developed and becomes a streaky fog to be visualized. On the other hand, the representation of the halftone in the digital latent image is represented by the number of dots and the line density. Therefore, it is not necessary to develop an intermediate potential and visualize a halftone.

To visualize the digital latent image with the developing method as described above, the gradation reproducibility of the intermediate potential does not pose a problem, and it is sufficiently developed in the vicinity of the V _D portion and in the low potential portion near the V _L portion. Magnetic toner that is not developed is required.

Curve of image density relative to the surface potential at the developing method using a conventional magnetic toner has a problem that the gradient is reduced in the vicinity of V _L portion and V _D portion (FIG. 2, see FIG. 3).

When developing a digital latent image, a portion with a high potential near the _VL portion is developed and the toner is left over. To avoid this, as shown in FIG. 2, the curve of the image density against the surface potential is plotted. It is necessary to use a developing method in which the developing conditions are set so that the slope of the image is increased and the influence of the density curve is not exerted. (Development method A.) On the other hand, the analog latent image is formed by charging the electrostatic latent image carrier and using the reflected light from the document as a light source to lower the surface potential according to the document density and set the potential contrast. It is what makes me.

When the low potential part is V _L , the high potential part is V _D , and the intermediate potential part is the intermediate tone potential (V _H ), the color image is in the V _L part, the black image is in the V _D part, and the half image is in the V _H part. It is visualized as a tone image.

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

To visualize the analog latent image by the developing method as described above, the gradation reproducibility of the intermediate potential is also important. Therefore, when developing an analog latent image, a developing method is used in which the developing conditions are set so that the gradient of the image density curve with respect to the surface potential is reduced and gradation is obtained as shown in FIG. (. And developing method B) for improving the tone reproducibility, the potential - V _L portion when the smaller inclination of the concentration, if it footing extends towards the V _D portion of the analog latent image, the V _L portion Fog is generally unlikely to occur because the reflected light is uniformly irradiated and the potential is constant.

However, when the developing method B is applied to the digital latent image, the trailing edge is generated near V _L of the potential-density gradient.
Fogging tends to occur in the _VL section.

On the other hand, when the developing method A is applied to an analog latent image, since the potential-density gradient is large, the density changes greatly even with a slight change in the potential, so that halftone reproduction becomes poor and halftone gradation cannot be obtained. .

Conventionally, 400 to 700 nm is required to form an analog latent image.
Since it is performed with visible light, a photosensitive drum having spectral sensitivity in this wavelength range is used.

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

It is difficult to produce a photosensitive drum that has both these spectral sensitivities and sufficient electrophotographic characteristics such as charging characteristics, residual potential, and dark decay. It has been difficult for a conventional image forming method to satisfactorily develop a latent image with the same image forming apparatus.

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

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

Still another object of the present invention is to provide a high image density in visualization of a digital latent image and an analog latent image, without fog,
An image forming method excellent in the expression of dots and lines and a developer for the image forming method are provided.

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

Required to create digital and analog latent images,
With uniform spectral sensitivity from white light to long wavelength light, it is possible to obtain a photosensitive drum with 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 capable of developing a digital latent image without fogging, developing an analog latent image with good gradation, and visualizing each latent image.

[Means and Actions for Solving the Problems] The present invention provides an organic photoconductor for electrophotography, which contains at least two or more charge generating substances and holds a digital electrostatic image and an analog electrostatic image, and a magnetic toner on the surface. The toner carrier to be carried is arranged in the developing section with a certain gap,
A developer used in an image forming method in which a magnetic toner is regulated to have a thickness smaller than the gap on a toner carrier and is conveyed to a developing unit to develop the magnetic toner, the magnetic toner having a particle diameter of 5 μm or less. Contains magnetic toner particles in an amount of 17-60% by number, 8-12.7
Magnetic toner particles having a particle size of μm are contained in an amount of 1 to 33% by number.
The present invention relates to a developer for developing an electrostatic charge image, comprising 2.0% by volume or less of magnetic toner particles having a particle size of not less than μm, and having a particle size distribution in which the volume average particle size of the magnetic toner is 4 to 10 μm.

According to the present invention, an organic photoconductor for electrophotography, which contains at least two or more charge generating substances and holds a digital electrostatic image and an analog electrostatic image, and a toner carrier having a magnetic toner on its surface are fixed in a developing section. With a gap of
In an image forming method in which magnetic toner is regulated to have a thickness smaller than the gap on a toner carrier and is conveyed to a developing unit for development, the magnetic toner contains magnetic toner particles having a particle size of 5 μm or less in an amount of 17 to 60 μm. % To 33% by weight of magnetic toner particles having a particle diameter of 8 to 12.7 μm, and 2.0% by volume or less of magnetic toner particles having a particle diameter of 16 μm or more. Has a particle size distribution of 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 conductor substrate, and at least two compounds as the charge generating substance. It is characterized in that a photoreceptor containing is used.

The ionization potential and the electrical potential are matched with the charge generating substance formed by the compound having the spectral sensitivity in the visible light region (400 nm to 700 nm) and the compound having the spectral sensitivity in the infrared region (700 nm to 900 nm), and the sensitivity is improved. An organic photoconductive photoreceptor using a charge transport material having excellent residual potential and charging characteristics can be used as an electrostatic charge image carrier having spectral sensitivity from visible light to semiconductor laser light.

By using such an electrostatic charge image carrier, an electrostatic latent image carrier can be formed with an analog latent image by white reflected light from a document table and a digital latent image by a laser spot from a semiconductor laser or the like. it can.

The compound having a spectral sensitivity in the visible light region and the compound having a spectral sensitivity in the infrared region have a weight ratio of 5/1 to 1/5, preferably
It is better to mix in a ratio of 3/1 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 the bisazo pigment having an absorption peak on the short wavelength side include a bisazo pigment having an oxadiazole ring as a central skeleton. For example, a bisazo compound having the following structural formula (1) may be mentioned.

Examples of the disazo pigment having an absorption peak on the long wavelength side include a bisazo pigment having a benzanthrone ring as a central skeleton or a bisazo pigment having diphenyl-pyridin-2-ylamine as a central skeleton. For example, a bisazo-based pigment having the following structural formula (2) or (3) may be mentioned.

Examples of the charge transport material include triphenylamine compounds having the following structural formula (4).

Contains 17-60% by number of magnetic toner particles having a particle size of 5 μm or less, 1-33% by number of magnetic toner particles having a particle size of 8-12.7 μm, and 2.0 volume of magnetic toner particles having a particle size of 16 μm or more. % Or less, and the volume average particle diameter of the magnetic toner is 4 to 10
A magnetic toner having a particle size distribution of μm is arranged on the surface of the toner carrier with a constant gap in the developing section, and the magnetic toner is regulated on the toner carrier to a thickness smaller than the gap. By a developing method in which the latent image is developed by being conveyed to a developing unit, the above-described digital latent image and analog latent image are faithfully visualized and a high-density image without fog 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 photoconductor.
It is also excellent in the reproduction of dot latent images such as halftone dots and digital images, and can provide images with excellent gradation and resolution. In addition, high image quality can be maintained even when copying or printing is continued, and even in the case of high-density images, good development can be performed with less toner consumption than conventional magnetic toner, which is economical. Also, it has an advantage in downsizing of the copying machine or the printer body.

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

One feature of the magnetic toner of the present invention is that the magnetic toner particles having a particle size of 5 μm or less account for 17 to 60% by number. Conventionally, magnetic toner particles having a particle size of 5 μm or less are difficult to control the charge amount, impair the fluidity of the magnetic toner, scatter toner and stain the machine, and further cause fogging of an image. As a result, it was considered necessary to actively reduce the amount.

However, according to the study by the present inventors, it was found that magnetic toner particles having a particle size of 5 μm or less are an essential component for forming a high quality image.

For example, by using a magnetic toner having a particle size distribution ranging from 0.5 μm to 30 μm, the surface potential on the photoconductor is changed, and a large development potential contrast, in which a large number of toner particles are easily developed, to a halftone, and a very small amount The latent image with the surface potential changed on the photoconductor is developed up to a small development potential contrast where only the toner particles are developed, and the developed toner particles on the photoconductor are collected and the toner particle size distribution is measured to be 8 μm or less. It was found that there are many magnetic toner particles, especially many magnetic toner particles of 5 μm or less. When magnetic toner particles having a particle size of 5 μm or less, which is most suitable for development, are smoothly supplied to the development of the latent image on the photoconductor, it is faithful to the latent image and does not protrude from the latent image, and truly reproducible. Excellent images can be obtained.

One feature 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. This is related to the necessity of the presence of magnetic toner particles having a particle size of 5 μm or less, as described above, and the magnetic toner particles having a particle size of 5 μm or less have the ability to exactly cover the latent image and faithfully reproduce it. However, in the latent image itself, the electric field strength of the peripheral edge portion is higher than that of the central portion, so that the inside of the latent image may have thinner toner particles than the edge portion, and the image density may appear thin. In particular, the magnetic toner particles of 5 μm or less have a strong tendency. However, the present inventors have found that the number of toner particles in the range of 8 to 12.7 μm is 1% to 33%.
It has been found that by containing a number%, this problem can be solved and further improved. It is considered that the toner particles in the range of 8 to 12.7 μm have an appropriately controlled charge amount with respect to the magnetic toner particles of 5 μm or less in particle size. It is supplied to a small inside to compensate for the small amount of toner particles inside the edge, and a uniform developed image is formed. As a result, a sharp image with excellent resolution and gradation at high density is formed. Is provided.

For magnetic toner particles having a particle size of 16 μm or more,
It is preferably 2.0% by volume or less and as small as possible.

By a completely different concept from the conventional viewpoint, the magnetic toner according to the present invention solves the conventional problems and is able to withstand the recent demand for high image quality.

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

Magnetic toner particles with a particle size of 5 μm or less are 17-60 of the total number of particles.
%, Preferably 25 to 50% by number, more preferably 30 to 50% by number. If less than 17% by number of magnetic toner particles having a particle size of 5 μm or less, there are few magnetic toner particles that are effective for high image quality. In particular, as the toner is used by continuing copying or printing out, effective magnetic toner particles are obtained. The components are decreased, the balance of the particle size distribution of the magnetic toner as shown in the present invention is deteriorated, and the image quality is gradually deteriorated. If it exceeds 60% by number, magnetic toner particles are likely to aggregate with each other, resulting in toner lumps having a particle size larger than the original particle size, resulting in rough image quality and reduced resolution, and the edge portion of the latent image and inside The density difference between the two becomes large, and the image tends to be transparent.

The particles in the range of 8 to 12.7 μm are preferably 1-33% by number, and more preferably 8-20% by number. When it is more than 33% by number, the image quality is deteriorated, and more than necessary development (toner excess) occurs, resulting in an increase in toner consumption.
On the other hand, if it is less than 1% by number, it becomes difficult to obtain a high image density.

The magnetic toner particles having a particle diameter of 16 μm or more are preferably 2.0% by volume or less, more preferably 1.0% by volume or less, further preferably 0.5% by volume or less. 2.0% by volume
If the amount is larger, it not only hinders the reproduction of fine lines, but also during transfer, coarse toner particles of 16 μm or more are prominently present on the thin layer surface of the toner particles developed on the photoconductor, so that the toner layer is not transferred. The delicate contact state between the photoconductor and the transfer paper is made irregular, which causes fluctuations in the transfer conditions, which causes a defective transfer image. The volume average diameter of the magnetic toner is 4 to 10 μm, preferably 4 to 9 μm
Therefore, this value cannot be considered in isolation from the above-mentioned components. Volume average particle size 4 μm
If it is less than the above, the problem that the toner amount on the transfer paper is small and the image density is low is likely to occur in the use such as a graphic image having a high image area ratio. It is considered that this is due to the same reason as the reason why the internal density is lowered with respect to the edge portion in the latent image described above. Volume average particle size 10μ
If it exceeds m, the resolution is not good in the case of m, and the quality of the image is likely to be deteriorated if the use is continued at the beginning of copying at best.

The inclination of the image density with respect to the surface potential obtained by the developing method using the magnetic toner having a specific particle size distribution, which is a feature of the present invention, is as shown in FIG.

As is apparent from FIG. 4, since the analog latent image is faithfully visualized in accordance with the potential because it has an appropriate inclination, it is possible to obtain an image having gradation in halftone reproduction. There is a good break from V _L to V _H, and fog does not occur even in a digital latent image. The disconnection from V _H to V _{D is} also good, sufficient image density can be obtained in analog latent images and digital latent images, and density unevenness does not occur. As will be described later, the magnetic toner having a specific particle size distribution as in the present invention has good adhesiveness to a latent image and is evenly applied, and a constant magnetic toner is developed according to the potential of the latent image. From V _L
V _H, also good sharpness of change from V _H to V _D, a high image density without fogging it is possible to obtain a good image tone reproduction of halftone.

It is preferable that the magnetic toner used in the developing step has developing characteristics satisfying the conditions as shown in FIG. 4 in relation to the potential of the latent image and the image density.

Specifically, the difference (V _LH ) between the latent image potential at which fogging can be visually confirmed and the latent image potential until the image density reaches 0.2 is 100 V.
The following: In the image density range of 0.2 to 0.8, the change amount (D _H ) of the image density per latent image potential difference of 10 V is less than 0.11 (preferably 0.10).
The difference (V _HD ) between the latent image potential of image density 1.2 and the latent image potential until the image density of 1.3 or more (or the maximum image density of 1.2 or more) is reached is 100 V or less. The difference (V _LD ) between the latent image potential at which fogging can be visually confirmed and the latent image potential until the image density reaches 1.3 or higher (or the maximum image density of 1.2 or higher) is 400 V or less. It is preferable that the developing means having the magnetic toner satisfy the developing characteristics of (more preferably 350 V or less, particularly preferably 300 V or less).

In the present invention, the latent image potential (V _D ) of the black image portion is preferably 550 to 750 V (preferably 600 to 700 V) in absolute value.

A Coulter Counter TA-II type (manufactured by Coulter) is used as a measuring device, an interface (manufactured by Nikkaki) and a CX-1 personal computer (manufactured by Canon) for outputting number distribution and volume distribution are connected, and the electrolytic solution is 1 Prepare a 1% NaCl aqueous solution using graded sodium chloride. As a measuring method, a surfactant (preferably alkylbenzene sulfonate) is used as a dispersant in 100 to 150 ml of the electrolytic aqueous solution.
Add 0.1 to 5 ml, and further add 2 to 20 mg of the measurement sample. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and by the Coulter Counter TA-II type,
Using a 100 μ aperture as an aperture, the particle size distribution of particles of 2 to 40 μ was measured based on the number, and the value according to the present invention was obtained.

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

For example, polystyrene, a homopolymer of styrene such as polystyrene, poly-p-chlorostyrene, polyvinyltoluene and a substitution product thereof; a styrene-p-chlorostyrene copolymer, a styrene-vinyltoluene copolymer, a styrene-vinylnaphthalene copolymer. , Styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl Styrene-based 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 modification Enol 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 , Petroleum resins can be used.

In the heating and pressure roller fixing method in which the oil is hardly applied, the so-called offset phenomenon in which a part of the toner image on the toner image supporting member is transferred to the roller and the adhesion of the toner to the toner image supporting member are important problems. is there. Toners that fix with less heat energy usually tend to be blocked or caked during storage or in a developing device, so these problems must be taken into consideration at the same time. The physical properties of the binder resin in the toner are most important in these phenomena. Further, according to the research by the present inventors, when the content of the magnetic substance in the toner is reduced,
The adhesion of the toner to the toner image supporting member at the time of fixing is improved, but offset is likely to occur, and blocking or caking is likely to occur. In the present invention, when the heating and pressure roller fixing method in which the oil is hardly applied is used, the selection of the binder resin is more important. Preferred binder resins include cross-linked styrenic copolymers or cross-linked polyesters.

As a comonomer for the styrene monomer of the styrene-based copolymer, 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, methacrylonitrile, acrylamide. Acids or substituted products thereof; dicarboxylic acids having a double bond such as maleic acid, butyl maleate, methyl maleate and bumethyl maleate and substituted products thereof; vinyl esters such as vinyl chloride, vinyl acetate and vinyl benzoate. Ethylene olefins such as ethylene, propylene and butylene; Vinyl ketones such as vinyl methyl ketone and vinyl hexyl ketone; Vinyl vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl isobutyl ether Ethers; and the like. These vinyl monomers are used alone or in combination of two or more.

Here, as the cross-linking agent, a compound having two or more polymerizable double bonds is mainly used. Aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; carboxylic acid esters having two double bonds such as ethylene glycol diacrylate, ethylene glycol dimethacrylate and 1,3-butanediol dimethacrylate; divinylaniline, divinylaniline Examples thereof include divinyl compounds such as vinyl ether, divinyl sulfide and divinyl sulfone; and compounds having 3 or more vinyl groups. These crosslinking agents may be used alone or as a mixture. The crosslinking agent is preferably used in an amount of 0.01 to 5 parts by weight per 100 parts by weight of the monomer.

When the pressure fixing method is used, it is possible to use a binder resin for pressure fixing toner, such as polyethylene, polypropylene, polymethylene, polyurethane elastomer,
There are 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 in the toner particles (internal addition) or in the mixture with the toner particles (external addition). The charge control agent makes it possible to optimally control the charge amount according to the developing system, and particularly in the present invention, it is possible to further stabilize the balance between the particle size distribution and the charge. Examples of the positive charge control agent include nigrosine and a modified product of nigrosine with a fatty acid metal salt; quaternary aluminium salts such as tributylbenzylammonium-1-hydroxy-4-naphthosulfonate, tetrabutylaluminium tetrafluoroborate; dibutyltin oxide, dioctyl. Examples thereof include diorgano tin oxides such as tin oxide and dicyclohexyl tin oxide; diorgano tin borates such as dibutyl tin borate, dioctyl tin borate and dicyclohexyl tin borate. 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 [In the formula, R ₁ represents H or CH ₃ , and R ₂ and R ₃ represent a substituted or unsubstituted alkyl group (preferably C _{1 to} C ₄ ). ] A monomeric monomer represented by the following formula; or a copolymer with a polymerizable monomer such as styrene, acrylic acid ester and methacrylic acid ester as described above can be used as a positive charge control agent. In this case, these charge control agents also function as (all or part of) the binder resin.

It is preferable to use the above-mentioned charge control agent (which does not function as a binder resin) in the form of fine particles. In this case, the number average particle diameter of the charge control agent is, specifically,
It is preferably 4 μm or less (further, 3 μm or less).

When internally added to the toner, such a charge control agent is preferably used in an amount of 0.1 to 20 parts by weight (more preferably 0.2 to 10 parts by weight) with respect to 100 parts by weight of the binder resin.

The magnetic toner according to the present invention may be internally or externally mixed with various additives, 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 with respect to 100 parts by weight of the binder resin. Other additives include, for example, lubricants such as zinc stearate; abrasives such as cerium oxide and silicon carbide;
Examples include flowability-imparting agents or anti-caking agents such as colloidal silica and aluminum oxide; conductivity-imparting agents such as carbon black and tin oxide.

Low molecular weight polyethylene, low molecular weight polypropylene, microcrystalline wax, carnauba wax, zazol wax, for the purpose of improving releasability at the time of heat roll fixing.
It is also one of the preferred embodiments of the present invention to add a wax-like substance such as paraffin wax to the magnetic toner in an amount of about 0.5 to 5 wt% based on the binder resin.

Further, the magnetic toner according to the present invention may also serve as a colorant, but contains a magnetic material. The magnetic material contained in the magnetic toner of the present invention includes magnetite, γ
-Iron oxides such as iron oxides, ferrites, iron-rich ferrites; metals such as iron, cobalt, nickel or these metals and aluminum, cobalt, copper, lead, magnesium, tin, zinc, antimony, beryllium, bismuth,
Cadmium, calcium, manganese, selenium, titanium,
Examples include alloys with metals such as tungsten and vanadium, and mixtures thereof.

These ferromagnetic materials have an average particle size of 0.1 to 1 μm, preferably 0.1 to 0.5 μm. The amount contained in the magnetic toner is 60 to 120 per 100 parts by weight of the resin component.
Parts by weight, preferably 65 to 110 parts by weight per 100 parts by weight of the resin component.

To prepare the magnetic toner for developing an electrostatic charge image according to the present invention, magnetic powder and a vinyl-based or non-vinyl-based thermoplastic resin, a pigment or dye as a colorant, a charge control agent, and other additives as required. And the like are sufficiently mixed by a mixer such as a ball mill, and then heated, kneaded, melted, kneaded and kneaded using a heat kneader such as an extruder to disperse or dissolve the pigment or dye in the resin, The magnetic toner according to the present invention can be obtained by crushing and solidifying 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 an emulsified suspension prepared by mixing a predetermined material with a monomer that constitutes the binder resin. And a polymerization method in which the toner is polymerized to obtain a toner; or a so-called microcapsule toner including a core material and a shell material, a method in which a core material or a shell material, or both of them contain a predetermined material; Can be applied.

The magnetic toner according to the present invention has an absolute value of triboelectric charge of 5 to
It preferably has triboelectrification characteristics such as 20 μc / g (preferably 7 to 15 μc / g).

The triboelectrification characteristics of the magnetic toner have the main particle size (200 mesh pass to 300 mesh on) in 10g of magnetic toner and 200 to 300 mesh (Taylor) which are left in the environment of 25 ° C and 50 to 60% RH. , 90 g of carrier iron powder not coated with resin (for example, EFV200 / 300 manufactured by Nippon Iron and Powder Co.) and a polyethylene container having a volume of about 200 c.c. It is determined by measuring the triboelectric charge of the magnetic toner by a conventional blow-off method using an aluminum cell having a 400-mesh screen, which is mixed by shaking about 50 times up and down).

The true density of the magnetic toner according to the present invention is preferably 1.45 to 1.70 g / cm ³ , more preferably 1.50 to 1.65 g / cm 3.
^{Is 3} . In this range, the magnetic toner having a specific particle size distribution of the present invention can exert the most effect in terms of high image quality and durability stability. True density of magnetic toner is 1.45
If it is smaller, the weight of the magnetic toner particles themselves is too light, so that reversal fog and crushing or skipping of fine lines due to excessive toner particle sticking and deterioration of resolution are likely to occur.
If the true density of the magnetic toner is larger than 1.70, the image density will be thin and the image will lack sharpness such as broken fine lines, and the magnetic force will also be relatively large, so the ears of the toner will easily become long or branched. In this case, when the latent image is developed, the image quality is disturbed and the image tends to be rough.

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

A cylinder made of stainless steel with an inner diameter of 10 mm and a length of about 5 cm, and a disc with an outer diameter of about 10 mm and a height of 5 mm that can be inserted into the cylinder (A).
Prepare a piston (B) with an outer diameter of about 10 mm and a length of about 8 cm. Put the disk (A) in the bottom of the cylinder, then put about 1 g of the measurement sample, and gently push the piston (B).
A force of 400 kg / cm ² is applied to this with a hydraulic press, and what is compressed for 5 minutes is taken out. The weight of this compressed sample is weighed (wg), the diameter (Dcm) and height (Lcm) of the compressed sample are measured with a micrometer, and the true density is calculated by the following formula.

In order to obtain even better developing characteristics, the magnetic toner of the present invention has a residual magnetization σ _{r of 1} to 5 emu / g, preferably 2 to 4.5 e.
It is preferable that the magnetic properties are mu / g, the saturation magnetization σ _s is 20 to 40 emu / g, and the coercive force H _C is 40 to 100 oersted ( _e ). May be mixed internally added or externally added silica fine powder in the magnetic toner according to (both measured magnetic field is 1K _e) the present invention, it is preferable to mix external addition. A magnetic toner having a particle size distribution as a feature of the present invention has a larger specific surface area than conventional toners.
When the magnetic toner particles are brought into contact with the surface of a cylindrical conductive sleeve having a magnetic field generating means therein due to triboelectrification, the number of contact between the toner particle surface and the sleeve is larger than that of the conventional magnetic toner, and Particle wear is likely to occur. When the magnetic toner according to the present invention is combined with the silica fine powder, the silica fine powder is present between the toner particles and the surface of the sleeve, so that the wear is remarkably reduced. This makes it possible to extend the life of the magnetic toner, maintain stable chargeability, and provide a developer having a magnetic toner that is more excellent in long-term use.

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

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

SiCl ₄ + 2H ₂ + O ₂ → SiO ₂ + 4HCl In this manufacturing process, for example, aluminum chloride or
It is also possible to obtain a composite fine powder of silica and another metal oxide by using another metal halogen compound such as titanium chloride together with a silicon halogen compound, and these are also included.

Examples of commercially available silica fine powder produced by vapor phase oxidation of a silicon halogen compound used in the present invention include those commercially available under the following trade names.

AEROSIL 130 (Nippon Aerosil Co., Ltd.) 200 300 380 OX50 TT600 MOX80 MOX170 COK84 Ca-O-SiL M-5 (CABOTO Co.) MS-7 MS-75 HS-5 EH-5 Wacker HDK N 20 V15 (WACKER-CHEMIE) GMBH) N20E T30 T40 D-C Fine Silica (Dow Corning Co.) Fransol (Fransil) On the other hand, there are various conventionally known methods for producing the silica fine powder used in the present invention by a wet method. Applicable.
For example, the decomposition of sodium silicate with an acid and the general reaction formula are shown below.

Na ₂ O ・ XSiO ₂ + HCl + H ₂ O → SiO ₂・ nH ₂ O + NaCl Other decomposition of sodium silicate with ammonia salts or alkali salts, decomposition of sodium silicate with acid after generating alkaline earth metal silicate There are a method of making silicic acid, a method of making a sodium silicate solution into silicic acid by an ion exchange resin, a method of using natural silicic acid or a silicate, and the like.

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

Examples of commercially available silicic acid fine powders synthesized by the wet method include those commercially available under the following trade names.

Carplex Shionogi Nepseal Nippon Silica Tokseal, Fineseal Tokuyama Soda Vita Seal Takihi Shilton, Shirnex Mizusawa Chemical Starsil Kamijima Chemical Himedir Ehime Pharmaceutical Syroid Fuji Debison Chemical Hi-sil Pittsburgh Plate Glass.Co (Pittsburgh Plate Glass) Durosil (Durosir) Ultorasil (Ultraseal) Fiillstoff-Gesellschaft Marquart Manosil (Manosir) Hardman and Holden Hoesch (Hesch) Chemische Fabrik Hoesch K-G (Hemische Fabrik Hesshe) ) Sil-Stone Stoner Rubber Co. Nalco Nalco Chem. Co. Quso Philodelphia Quartz Co. Ladelphia Quartz Imsil Illinois Minerals Co. Calcium Silikat Chemische Fabrik Hoesch.K-G Calsil Fiillstoff-Gesellschaft Marquart Quartz ) Fortafil Imperial Chemical Industries.Ltd. (Imperial Chemical Industries) Microcal (Microcal) Joseph Crodfiels & Sons Ltd. (Joseph Crossfield and Sons) Vulkasil (Vulkasil) Farbenfabriken Bryer, A.-G. (Buyer) Tufknit Durham Chemicals.Ltd. (Durham Chemicals) Silmos Shiraishi Kogyo Starex Kamishima Chemical Fricosil Polywood Manure Of the above silica fine powders, the BET method is used. Specific surface area by the boss was nitrogen adsorption in the range of 30 m ² / g or more (especially 50 to 400 m ² / g) gives good results. 0.01 to 8 parts by weight of silica fine powder, preferably 0.1 to 100 parts by weight of magnetic toner.
It is recommended to use 1-5 parts by weight.

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

As a method for obtaining the positively chargeable silica fine powder, the above-mentioned untreated silica fine powder is used and at least one nitrogen atom is contained in the side chain.
There is a method of treating with a silicone oil having three or more organo groups, a method of treating with a nitrogen-containing silane coupling agent, or a method of treating with both of them.

In the present invention, the positively chargeable silica is one having a positive triboelectric charge with respect to the iron powder carrier when measured by the blow-off method.

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

(In the formula, R ₁ represents hydrogen, an alkyl group, an aryl group or an alkoxy group, R ₂ represents an alkylene group or a phenylene group, R ₃ and R ₄ represent hydrogen, an alkyl group or an aryl group, and R ₅ Represents a nitrogen-containing heterocyclic group) The alkyl group, aryl group, alkylene group, and phenylene group may have an organo group having a nitrogen atom, and may be substituted with halogen or the like within a range not impairing the charging property. It may have a group. Silicone oil is silica 100
It is preferable to use 0.1 to 100 parts by weight based on parts by weight.

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

R _m —Si—Y _n (R represents an alkoxy group or halogen, Y represents an amino group or an organo group having at least one nitrogen atom, and m and n are integers of 1 to 3 and m + n
= 4. ) Examples of the organo group having at least one nitrogen atom 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. As the nitrogen-containing heterocyclic group, there are an unsaturated heterocyclic group and a saturated heterocyclic group, and known ones can be applied. Examples of the unsaturated heterocyclic group include the following.

Examples of the saturated heterocyclic group include the followings.

The heterocyclic group used in the present invention is preferably a 5-membered ring or a 6-membered ring in view of stability.

Examples of such treating agents include aminopropyltrimethoxysilane, aminopropyltriethoxysilane, dimethylaminopropyltrimethoxysilane, diethylaminopropyltrimethoxysilane, dipropylaminopropyltrimethoxysilane, dibutylaminopropyltrimethoxysilane, mono Butylaminopropyltrimethoxysilane, dioctylaminopropyltrimethoxysilane, dibutylaminopropyldimethoxysilane, dibutylaminopropylmonomethoxysilane, dimethylaminophenyltriethoxysilane, trimethoxysilyl-γ
-Propylphenylamine, trimethoxysilyl-γ-
There is propylbenzylamine. Further, as the nitrogen-containing heterocycle, those having the above-mentioned structure can be used, and examples of such a compound include trimethoxysilyl-γ-propylpiperidine, trimethoxysilyl-γ-propylmorpholine, trimethoxysilyl-γ-propyl. I have imidazole. The nitrogen-containing silane coupling agent is preferably used in an amount of 0.1 to 100 parts by weight based on 100 parts by weight of silica.

The applied amount of these treated positively charged silica fine powders is
The effect is exhibited when the amount is 0.01 to 8 parts by weight with respect to 100 parts by weight of the positively chargeable magnetic toner, and particularly preferably, the positive chargeability having excellent stability is exhibited when 0.1 to 5 parts by weight is added. With respect to the addition form, to describe a preferred embodiment, it is preferable that 0.1 to 3 parts by weight of the treated silica fine powder is attached to the surface of the toner particles with respect to 100 parts by weight of the positively chargeable magnetic toner. The untreated silica fine powder described above can also be used in the same application amount.

The silica fine powder used in the present invention may be treated with a silane coupling agent or a treating agent such as an organic silicon compound for the purpose of hydrophobizing, if necessary. Examples of such a treating agent include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allylphenyldichlorosilane, and benzyldimethylchlorosilane, Brommethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane,
Chlormethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilylacrylate, vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1,3-divinyltetramemethyl Disiloxane, 1,3-diphenyltetramethyldisiloxane, and dimethylpolysiloxane having 2 to 12 siloxane units per molecule and each terminally located unit containing a Si-bonded hydroxyl group. There is. These one
Used as a seed or a mixture of two or more kinds. The above-mentioned hydrophobic treatment agent is preferably used in an amount of 0.1 to 100 parts by weight per 100 parts by weight of silica.

In the magnetic toner 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 powders of polytetrafluoroethylene, polyvinylidene fluoride and tetrafluoroethylene-vinylidene fluoride copolymer. Particularly, fine powder of polyvinylidene fluoride is preferable in terms of fluidity and polishing property. The addition amount to the toner is preferably 0.01 to 2.0% by weight, particularly preferably 0.02 to 1.0% by weight.

In particular, in the magnetic toner in which silica fine powder and the above fine powder are externally added and mixed, the reason is not clear, but stabilizes the existence state of silica attached to the toner, and the attached silica is released from the toner, The effects on toner abrasion and sleeve stain are not reduced, and the charging stability can be further increased.

An example of a specific apparatus that can be used for carrying 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 causing the toner to fly from a toner carrier such as a cylindrical sleeve to a latent image carrier such as a photoconductor. The magnetic toner is applied with a triboelectric charge mainly by contact with the surface of the sleeve, and is applied in a thin layer on the surface of the sleeve.
The thin layer of magnetic toner is formed thinner than the gap between the photoreceptor and the sleeve in the developing area. When developing the latent image on the photoconductor, it is preferable that magnetic toner having triboelectric charge is flown from the sleeve to the photoconductor while applying an alternating electric field between the photoconductor and the sleeve.

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

In the developing device of FIG. 5, for example, a stainless sleeve 2 (SUS304) having a diameter of 50 m / m is used as the non-magnetic sleeve 2-1 which is a toner carrier according to the present invention, and the magnetic pole N ₁ of the magnet 4 in the sleeve is N ₁ = 850 gauss. , N ₂ = 500 gauss, S ₁ =
650 gauss, S ₂ = 500 gauss, iron 1 which is a magnetic material is used for the blade 1a, and the gap between the blade 1a and the sleeve 2-1 is
250 μ, toner 10 is a magnetic toner according to the present invention, bias power supply 11 is AC and DC superimposed, and V _PP = 1
An example is a device with 200V, f = 800 (Hz), DC = + 100W. The shortest distance between the sleeve 2 and the latent image carrier 9 is 300
The one set as μ can be mentioned.

In the toner carrier carrying the magnetic toner on the surface in the image forming method of the present invention, the toner carrier surface is sandblasted by the irregular particles, by using the one having a rough surface of a specific uneven state, It is possible to maintain a good toner coat state for a long period of time without even and uniform unevenness on the surface of the toner carrier. The target surface is a mode in which the surface of the toner carrying member is formed over the entire area and innumerable fine cuts or projections are formed in random directions.

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

This is because the components in the toner adhere to the slopes and the recesses of the convex portions on the surface of the toner carrier, which results in poor charging of the magnetic toner particles and a decrease in the charge amount of the toner layer.

As a method for preventing or reducing the contamination of the magnetic toner carrier, it is preferable 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 specific irregularities formed by a plurality of spherical trace dents, it becomes difficult for the toner component to adhere to the surface, and contamination can be prevented or reduced over a long period of time. It was also excellent in the ability to coat the toner uniformly.

The toner carrier having such a surface shape is also excellent in triboelectricity imparting ability, and the triboelectric charging ability of the magnetic toner according to the present invention can be sufficiently brought out to stabilize the chargeability.

Therefore, the ability of the electrostatic latent image to follow the potential is further improved, the gradation of halftone is excellent, and a fine and moist image is obtained. The potential-concentration curve to the V _L portion is also cut off more effectively, and it is more effective against fogging.

The toner carrier is hereinafter referred to as a sleeve.

As a method of obtaining a sleeve surface state having a surface having irregularities formed by a plurality of spherical trace depressions, a blast treatment method using regular particles can be used. As the regular particles, for example, stainless steel having a specific particle diameter, aluminum,
Hard spheres made of metal such as steel, nickel, brass or hard spheres such as ceramics, plastics, glass beads can be used. By blasting the surface of the sleeve with the regular particles having a specific particle diameter, it is possible to form a plurality of spherical trace depressions having substantially the same diameter R.

Diameter R of multiple spherical dents on the sleeve surface is 20-250
μm is preferable, more preferably 30 to 200 μm,
If the diameter R is 20 μm or less, the contamination by the components in the magnetic toner tends to increase, and conversely, if the diameter R is 250 μm or more, the uniformity of the toner coat on the sleeve tends to deteriorate. Therefore, the fixed particles used for the blast treatment of the sleeve surface also preferably have a diameter of 20 to 250 μm. Further, the pitch P of the irregularities on the surface of the sleeve and the surface roughness d are measured by using a fine surface roughness meter (Kosaka Research Institute, etc.) on the surface of the sleeve, and the surface roughness d is JIS 10-point average roughness ( RZ) According to "JIS B0601".

As shown in FIG. 6, a straight line parallel to the average line of the reference length l extracted from the sectional curve passes through the third peak from the highest and the third bottom from the deep, The distance between two straight lines is expressed in micrometers (μm), and the reference length is 1 = 0.25 mm. The pitch P is such that the convex portions are 0.1 μm or more higher than the concave portions on both sides, and are counted as one mountain.
It is calculated as follows.

[250 (μ)] / [number of peaks (μ) included in 250 (μ)] The pitch P of the irregularities on the sleeve surface is preferably 2 to 100 μ, more preferably 10 to 80 μm, and P is less than 2 μ. In that case, the contamination of the sleeve by the components in the magnetic toner tends to increase, and conversely, in the case where P exceeds 100 μ, the uniformity of the toner coat on the sleeve tends to decrease. The surface roughness d of the irregularities on the sleeve surface is preferably 0.1 to 5 μm, more preferably 0.5 to 4 μm, and d is 5
If it exceeds μm, in the system in which an alternating voltage is applied between the sleeve and the latent image holder to fly the magnetic toner from the sleeve side to the latent image surface for development, the electric field is concentrated on the uneven portion. Then, the image tends to be disturbed, and conversely d is 0.
If it is less than 1 μm, the uniformity of the toner coat on the sleeve tends to deteriorate.

An example of a specific apparatus that can be used for carrying out the image forming method of the present invention is shown in FIG.

A process of forming an electrostatic latent image on the photoconductor 30 will be described. After charging the photoconductor 30 with the primary charger 29, the original 21 is irradiated with a halogen lamp or a fluorescent lamp 24, and the reflected light I _A is imaged on the photoconductor 30 by the lens group 26 and the reflection mirror 25, and an analog latent image is formed. Form an image. An electric signal output from a keyboard or an external device or image information obtained from a document is processed by an image processing unit 39, and the electric signal is input to a laser scanner 27, and a laser beam I _D is irradiated onto the photoconductor 30. Illuminate to form a digital latent image.

The latent image thus formed is simultaneously developed by the developing device 31 using the above-described developing process to visualize it. The toner image formed on the photoconductor 30 is transferred to the transfer material 38 by the transfer separation charger 35.
After the transfer, the transfer material 38 is separated from the photoconductor 30 and fixed by the fixing device 37 to obtain an image. The photoconductor 30 is cleaned of residual toner after transfer by the cleaner unit 33, and is discharged by the pre-exposure lamp 28 for repeated use.

[Examples] The present invention will be specifically described below with reference to Examples. All parts in the following formulations are parts by weight.

Example 1 An image forming apparatus used for image formation will be described with reference to FIG.

The used photosensitive drum 30 will be described. 100 parts of conductive powder coated with tin oxide containing 10% of antimony oxide to 75% of titanium oxide, 100 parts of resol type phenol resin, 30 parts of methanol, 100 parts of methyl cellosolve
In addition to the above solution, a coating material sufficiently dispersed by a ball mill was dip-coated on a substrate which was an aluminum cylinder of 80φ × 360 mm, and heat-cured at 140 ° C. for 30 minutes to form a conductive undercoat layer of 20 μm. Polyamide resin [4 elements-
Nylon (6-66-610-12)] 1 part and 8-nylon resin (methoxymethylated 6 nylon, methoxylation rate approx.
A coating solution obtained by dissolving 3 parts of 30%) in 50 parts of methanol and 40 parts of butanol was applied by dip coating to form an intermediate layer having a thickness of 0.5 μm. 2.5 parts of the disazo pigment represented by the formula (1) and 1.0 part of the disazo pigment represented by the formula (5) Polyvinyl benzal resin (N = 85,000, degree of benzal 80) 2 parts and 100 parts of cyclohexanone were dispersed for 2 hours by a side mill using 1φ glass beads. This dispersion liquid 40 to 80 parts of tetrahydrofuran and 40 to 80 parts of methyl ethyl ketone are appropriately added to dilute to obtain a coating liquid, which is applied on the intermediate layer and then at 80 ° C.
After drying for 10 minutes, a charge generation layer having a film thickness of 250 mg / m ² in terms of weight was formed.

Next, bisphenol Z type polycarbonate resin (n2
2,000) 10 parts, polytetrafluoroethylene powder 5 parts as fluororesin powder, monochlorobenzene 40 parts and TH
Disperse with F15 part in a stainless steel ball mill for 50 hours,
10 parts of the stilbene compound represented by the formula (6) as a charge transport substance was added to the resulting dispersion. Was dissolved on the charge generation layer and dried by hot air at 120 ° C. for 1 hour to form a charge transport layer having a thickness of 25 μm.

The photoconductor 30 thus obtained was mounted on the image forming apparatus.

The spectral sensitivity of this photoconductor is shown in FIG. A paper analyzer SP-428 (manufactured by Kawaguchi Electric Co., Ltd.) was used for the measurement.
The laser scanner 27 uses a semiconductor laser of 780 nm and is set so that the spot diameter is 100 μm on the photoconductor and the scanning line density is 254-DPI.

The primary charger 29 sets the potential of the V _D part to −700 V and sets the amount of reflected light I _A of the halogen lamp irradiation light from the white part of the document to 1.5 lux · se.
As c, the potential of the _VL section was set to −200V. The laser output was set to 1.2 μJ / cm ^{2 and} the average potential of the V _L portion was set to −200V. Through the above steps, an analog latent image and a digital latent image can be formed on the photoconductor 30.

The developing conditions will be described with reference to FIG.

The magnetic toner is applied in a thin layer on the surface of the stainless steel cylindrical sleeve 2 via the magnetic blade 1a, and the gap between the sleeve 2 and the blade 1a is set to about 250 μm, and the thickness is about 90 μm.
m toner layer was formed. The sleeve 2 has a fixed magnet 4 as a magnetic field generating means, and a magnetic field of 1000 gauss is fixed near the surface of the sleeve in the developing area adjacent to the photosensitive drum 9 provided with the above-mentioned organic photoconductive layer having a negatively chargeable latent image. 4 is formed. The closest distance between the photosensitive drum 9 rotating in the direction of the arrow and the sleeve 2 was set to about 300 μm. AC bias between the photosensitive drum 9 and the sleeve 2.
2000Hz / 1350V _PP and DC bias 250V were applied synergistically.

For the toner carrier, use the surface of a stainless steel sleeve (SUS304) and use # 300 carborundum as irregular particles.
The blast treatment was performed under the conditions of a spray nozzle diameter of 7φ, a distance of 100 mm, an air pressure of 4 kg / cm ² , and 2 minutes.

After the latent image is visualized using the developing device as described above, the toner image on the photoconductor 30 is transferred onto the transfer material and fixed,
I got an image.

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

The fine line reproducibility in the analog image was measured by the following method. An original document with a fine line of 100 μm width was copied under appropriate copying conditions as a measurement sample, and the line width was measured by an indicator from the enlarged monitor image using the Luzex 450 particle analyzer as the measurement device. I do. At this time, since the measurement position of the line width has unevenness in the width direction of the thin line image of the toner, the average line width of the unevenness is used as the measurement point. From this, the fine line reproducibility value (%) is calculated by the following formula.

The resolution was measured by the following method. A pattern consisting of 5 fine lines with the same line width and spacing, with a space of 1 mm
2.8,3.2,3.6,4.0,4.5,5.0,5.6,6.3,7.1 or 8.0 Make an original image that is drawn to be. An image obtained by copying an original document containing these 10 types of line images under appropriate copying conditions is observed with a magnifying glass, and the number of images (lines / mm) in which fine lines are clearly separated gives the resolution value. To do.

The larger this number is, the higher the resolution is.

Line representation and resolution in digital images were measured by the following methods.

An image obtained by forming a latent image on the photoconductor with a laser so that five 1 dot, 1 space lines (100 μm) were formed was used as a measurement sample. The resolution was evaluated by the resolution of the line of 5 lines / mm. In addition, the line expression is calculated by the following formula in the same manner as in the case of an analog image from four lines of 1 dot and 2 spaces (100 μm) formed.

The dot expression was measured by the following method. An image obtained by forming a checkered latent image composed of 1 dot, 2 dots, 3 dots, and 4 dots on a photoconductor with a laser was used as a measurement sample. Observe this sample with a magnifying glass (30x) and use the number of dots in the image that clearly shows the checkerboard pattern as the dot expression. The smaller this number is, the better the dot expression is.

In the image forming test, a digital image and an analog image were simultaneously obtained by the following method. A solid black portion was provided in the original document, and a digital latent image was formed by a laser on the solid black portion formed on the photoconductor. The analog latent image and the digital latent image thus obtained were developed and visualized to obtain an image having an analog portion and a digital portion.

The magnetic toner was prepared as follows.

After thoroughly mixing the above materials with a blender, they were kneaded with a twin-screw kneading extruder set at 150 ° C. After cooling the obtained kneaded product and coarsely pulverizing it with a cutter mill, it was finely pulverized with a fine pulverizer using a jet stream, and the obtained fine pulverized powder was classified with a fixed wall type air classifier. A classified powder was produced. Furthermore, the ultra fine powder and coarse powder are strictly removed at the same time with a multi-division classifier (Elvojot classifier manufactured by Nittetsu Mining Co., Ltd.) using the Coanda effect to positively charge black fine powder (magnetic powder). Toner). The particle size distribution of this magnetic toner is shown in Table 1.

To 100 parts of the obtained black fine powder magnetic toner, 0.6 part of positively charged hydrophobic dry silica (BET specific surface area 200 m ^{2 /} g) was added and mixed with a Henschel mixer.

The magnetic toner was put into the above-mentioned image forming apparatus and an image output test was conducted. The results of repeating this test 5000 times are shown in Table 2 for the analog image part and in Table 3 for the digital image part.

As is apparent from these tables, good images were obtained without fogging in both the analog part and the digital part, and line expression, halftone dot expression, and gradation were excellent. The relationship between the surface potential of the drum and the image density is shown in FIG. In this method, the illuminance of a halogen lamp is adjusted using a gray scale, various charges are placed on the drum, and the surface potential of that portion is measured. Then, each potential was developed to determine the image density.

Examples 2 and 3 Instead of the magnetic toner used in Example 1, a positively chargeable magnetic toner having a particle size distribution as shown in Table 1 was obtained by changing the addition amount of the magnetic material and controlling the finely pulverizing and classifying conditions. An image production test was conducted in the same manner as in Example 1 except that the test was conducted. The results are shown in Tables 2 and 3, and clear images were obtained for both analog and digital images.

Example 4 Table 1 shows the particle size distribution of the positively chargeable magnetic toner obtained by using the above materials in the same manner as in Example 1.

Further, in the same manner as in Example 1, positively charged hydrophobic silica was externally added.

In the image forming apparatus of Example 1, an image forming test was conducted with the same apparatus except that the sleeve of the magnetic toner carrying member shown below was used.

The surface of the stainless steel sleeve (SUS304) uses 80% or more glass beads with a diameter of 53 to 62 μm as regular particles.
Blasting was performed under the conditions of a blowing nozzle diameter of 7φ distance of 100 mm and an air pressure of 4 kg / cm ² for 2 minutes to form irregularities in which the diameter R of a plurality of spherical trace dents was 53 to 62 μm. The pitch P of the irregularities on the sleeve surface is 33 μ, and the surface roughness d is
It was 2.0μ.

The results are shown in Tables 2 and 3.

As is apparent from this table, an image with high density without fog was obtained and the image quality was excellent.

Examples 5 and 6 Implementation was carried out except that the raw materials used in Example 4 were used and a positively chargeable magnetic toner having a particle size distribution as shown in Table 1 was used by controlling the amount of magnetic material and finely pulverized and classified conditions. An image drawing test was conducted in the same manner as in Example 4. The results are shown in Tables 2 and 3. Both analog and digital images had excellent image quality.

Comparative Example 1 A magnetic toner having the particle size distribution shown in Table 1 was obtained in the same manner by using the same material as the magnetic toner used in Example 1 except that the magnetic iron oxide was 60 parts. Furthermore, 100 parts of this magnetic toner is loaded with positively charged hydrophobic dry silica (BET200m ² / g)
0.4 parts was added and mixed with a Henschel mixer. This magnetic toner was subjected to the same image forming test as in Example 1 and the result was
It is shown in Table 3 and Table 3.

Inferior in line expression, dot expression, and resolution, fog was seen in the digital image part, and halftone was rusty in the analog image part.

Comparative Examples 2 to 4 Example 4 was repeated 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 fine pulverization and classification conditions. A similar drawing test was conducted.

The results are shown in Tables 2 and 3.

In Comparative Example 2, fogging in the digital part, in Comparative Example 3, lines and dots were crushed due to excessive sticking, and in Comparative Example 4, fogging, a good image was not obtained.

Comparative Example 5 In the image forming apparatus of Example 4, the following photosensitive drums were mounted. A photosensitive drum was prepared in the same manner as in Example 4, except that the compound represented by the formula (1) was omitted. Tables 2 and 3 show the results of an image output test in which the magnetic toner used in Example 4 was placed in this image forming apparatus.

The sensitivity of the analog part was not taken and a good image was not obtained, but there was no problem in the digital part.

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

Example 7 A latent image was developed in the same manner as in Example 1 except that a photosensitive drum was produced using the bisazo pigment (3) instead of the bisazo pigment (5). Good results were obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a developing device using a magnetic blade, FIGS. 2, 3, and 4 are explanatory views of the relationship between the image density and the potential of the surface of the photoconductor, and FIG. FIG. 6 is a schematic explanatory view of a developing device according to the present invention, FIG. 6 is a definition explanatory view of surface roughness and pitch, and FIG. 7 is a schematic explanatory view of an image forming device according to the present invention. FIG. 8 shows the spectral sensitivity of the photosensitive drum according to the present invention, and FIG. 9 is a graph plotting the relationship between the image density and the surface potential of the photosensitive drum obtained by the image forming apparatus according to the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masatsugu Fujiwara 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Kiichiro Sakashita 3-30-2 Shimomaruko, Ota-ku, Tokyo Kya Non-Co. Ltd. (56) Reference JP-A-58-129437 (JP, A) JP-A-51-3244 (JP, A) JP-A-54-72054 (JP, A) JP-A-55-120046 (JP , A) JP 59-86063 (JP, A) JP 60-196066 (JP, A) JP 55-120057 (JP, A) JP 59-33459 (JP, A) JP 61-166553 (JP, A)

Claims (2)

[Claims] 1. An electrophotographic organic photoreceptor for holding a digital electrostatic image and an analog electrostatic image containing at least two or more charge generating substances, and a toner carrier carrying a magnetic toner on its surface in a developing section. A developer used in an image forming method in which a magnetic toner is disposed on a toner carrier with a thickness smaller than the gap and is conveyed to a developing unit to develop the magnetic toner, the magnetic toner being disposed with a constant gap. The toner contains 17 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 12.7 μm, 2.0% by volume or less of magnetic toner particles having a particle size of 16 μm or more, and a volume average particle size of magnetic toner of 4 to 10 μm A developer for developing an electrostatic charge image, which has a distribution. 2. An organic photoconductor for electrophotography, which contains at least two or more charge generating substances and holds a digital electrostatic image and an analog electrostatic image, and a toner carrier having a magnetic toner on its surface in a developing section. In an image forming method in which a magnetic toner is arranged on a toner carrier with a thickness smaller than the gap and is conveyed to a developing section for development, the magnetic toner has a particle size of 5 μm or less. Diameter magnetic toner particles of 17 to 60% by number, magnetic particle diameter of 8 to 12.7 μm of 1 to 33% by weight, magnetic toner particles of 16 μm or more at 2.0 volume% or less The magnetic toner has a particle size distribution in which the volume average particle size of the magnetic toner is 4 to 10 μm.