JPH0473585B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing method in electrophotography, electrostatic recording, etc., in which an electrical latent image formed is developed with an insulating toner that is triboelectrically charged to obtain a visible image. Regarding.

Conventionally, as an electrophotographic method, U.S. Patent No. 2297691
Specification of No. 42-23910 and Special Publication No. 1973
Many methods are known, as described in Japanese Patent No. 24748, etc., but in general, a photoconductive substance is used to form an electrical latent image on a photoreceptor by various means, and then the A latent image is developed using toner, and after the toner image is transferred to a transfer material such as paper as necessary, it is fixed by heat, pressure, solvent vapor, etc. to obtain a copy.

Furthermore, various developing methods are known in which an electrical latent image is visualized using toner. For example, U.S. Patent No.
The magnetic brush method described in specification No. 2874063,
A large number of development methods are known, such as the cascade development method described in No. 2,618,552, the powder cloud method, the fur brush development method, and the liquid development method described in No. 2,221,776.

Among these developing methods, in particular, a magnetic brush method using a developer mainly consisting of toner and carrier,
Cascade method, liquid development method, etc. are widely put into practical use. All of these methods are excellent methods in which good images can be obtained relatively stably, but on the other hand, they have common drawbacks associated with two-component developers, such as deterioration of the carrier and fluctuations in the mixing ratio of the toner and carrier.

In order to avoid such drawbacks, various development methods using a one-component developer made only of toner have been proposed, among which many methods are superior to methods using a developer made of magnetic toner particles.
US Pat. No. 3,909,258 proposes a developing method using an electrically conductive magnetic toner. This supports a conductive magnetic developer in a cylindrical conductive sleeve with magnetism inside.
This is brought into contact with an electrostatic image and developed.
At this time, in the developing section, a conductive path is formed by the toner particles between the recording medium surface and the sleeve surface, and through this conductive path, the sleeve conducts charges to the toner particles, causing a Coulomb force between the electrostatic image and the image area. The toner particles adhere to the image area and are developed.

This developing method using conductive magnetic toner is an excellent method that avoids the problems associated with conventional two-component developing methods, but on the other hand, because the toner is conductive, the developed image can be transferred from the recording medium to the final product such as plain paper. It has the disadvantage that it is difficult to electrostatically transfer it to a permanent support member.

As a developing method using a high-resistance magnetic toner that can be electrostatically transferred, JP-A-52-94140 discloses a developing method that utilizes dielectric polarization of toner particles. However, such a method has drawbacks such as an inherently slow development speed and an inability to obtain a developed image with sufficient density, making it difficult in practice.

Another developing method using high-resistance magnetic toner is a method in which the toner particles are triboelectrified by friction between the toner particles or friction between the toner particles and a sleeve, etc., and the toner particles are brought into contact with an electrostatic image holding member for development. It has been known. However, these methods have drawbacks such as the small number of times the toner particles come into contact with the friction member, which tends to result in insufficient triboelectric charging, and the Coulomb force between the charged toner particles and the sleeve increases, making them apt to aggregate on the sleeve. This makes it difficult to implement in practice.

The present applicant has previously proposed a new developing method that eliminates the above-mentioned drawbacks in Japanese Patent Application Laid-Open Nos. 54-43036 and 18656-1985. This involves applying a very thin layer of magnetic toner onto the sleeve, triboelectrically charging it, and then placing it in close proximity to the electrostatic image and developing it.

According to this method, by applying an extremely thin layer of magnetic toner onto the sleeve, the chances of contact between the sleeve and the toner are increased, and sufficient frictional electrification is possible. By moving the toner relative to each other, the toner particles are disaggregated and have sufficient friction with the sleeve, and by supporting the toner with magnetic force during development, background fog is prevented and excellent images are produced. That's what you get.

However, the performance of this method is largely affected by humidity conditions or the surface properties of the frictional charging member and the toner holding member. For example, in a state where the fluidity of the toner is reduced at high humidity, the agglomeration of the toner cannot be sufficiently dissolved by magnetic force, resulting in a decrease in toner transportability and image density.

Further, in this high humidity environment, the frictional charging property between the toner holding member and the toner is significantly reduced compared to a normal humidity environment, and image quality is likely to be disturbed. That is, depending on the material of the toner holding member or the combination with the toner, toner that can only obtain a weak charge due to contact friction is attached to areas other than the electrostatic latent image during development. During so-called fogging and transfer, weak toner adhesion to the transfer material occurs due to the low charge amount of the toner. This weak toner adhesion to the transfer material is caused by the collapse of the air layer, which is a minute gap created by the fixing roll, the transfer material, and the transferred toner on it, when the transfer material enters the fixing roll. This may cause image quality deterioration.

Furthermore, in low humidity, ram tends to occur in the toner coating layer on the toner holding member due to non-uniform charging between the toner holding member and the toner. Differences occur in the performance of the toner due to the number of times of friction on the friction charging member, etc., and for example, when A-4 originals are continuously copied and then changed to B-4 originals, the toner is not used for development until then. The image density decreases in the widened area, or when a high-density solid image is produced, the image density immediately after new toner is replenished onto the sleeve where there is almost no toner consumed as a result of development. Problems such as the so-called ghost phenomenon which deteriorates remain.

In order to improve the above problems, the present inventors
As a result of various investigations into triboelectric charging members, toner holding members, and toner materials, we have found that coating the surfaces of triboelectric charging members and toner holding members with a certain type of resin significantly improves the surface properties. It was very successful. however,
The results have not yet fully satisfied all of the characteristics required of a developing device (frictional charging properties, toner retention, uniformity of toner coating layer, durability of coating layer, stain resistance, etc.).

The object of the present invention is to provide a development method that overcomes the above-mentioned drawbacks.

Another object of the present invention is to provide a developing method that minimizes deterioration of image quality in a high humidity environment.

Still another object of the present invention is to provide a developing method with high durability and stability, whose performance does not change even after repeated copying.

A further object of the invention is to provide uniform triboelectric properties;
An object of the present invention is to provide a developing method that enables uniform application of toner to a carrier.

Specifically, the present invention provides a method for developing an electrical latent image using a triboelectrically charged insulating toner, in which at least the surface of a member that imparts a triboelectric charge to the insulating toner is provided with the following formula: A member containing zinc oxide fine powder containing aluminum oxide or vinyl silane-treated silica fine powder having a charge amount of A developing method characterized by developing.

1/40<|B|/|A|<1/2, |A|>|
B | (In the formula, A indicates the amount of charge of the insulating toner, and B
represents the amount of charge of fine zinc oxide powder containing aluminum oxide or fine silica powder treated with vinyl silane. ) regarding.

The method of the present invention will be explained below with reference to the drawings.

FIG. 1 shows a schematic configuration of an example of a copying device or a recording device to which the developing method according to the present invention can be applied, but the present invention is not limited thereto.

1 corresponds to an electrostatic image holder, and is a photosensitive drum containing a photoelectrostatic layer, and can be used with or without a photostatic layer on the surface. Things are also possible. 2 is a well-known photosensitive charging device; 3 is a document image or a light image;
Alternatively, it is a light image irradiation device that projects a light beam modulated by an image signal. As a result, an electrostatic image is formed on the photoreceptor 1. A developing device 4 has a developer carrier 4a, and forms a toner particle visual image in accordance with the electrostatic image on the photoreceptor 1.
5 is a device for transferring the toner image onto a transfer material 6. Incidentally, in order to improve the transferability, the visible image may be charged in advance by corona discharge or the like before transfer. Furthermore, it is also possible to adopt a so-called electrostatic image transfer method in which the electrostatic image on the photoreceptor 1 is temporarily transferred to another image carrier, and then converted into a visible image by the developing device 4. Reference numeral 7 denotes a fixing device for fixing the toner image on the transfer target member 6, which is composed of at least two rollers having pressure or heating pressure means. Reference numeral 8 denotes a cleaning device for cleaning and removing residual toner on the photoreceptor 1 after transfer, so that the photoreceptor 1 can be reused.

Next, a developing process to which the present invention is applied will be explained. FIG. 2 shows a cross-sectional view of one embodiment of the development process. In the same figure, when the electrostatic image holding surface 1 moves in the direction of the arrow, the multipolar permanent magnet 9 is fixed so as not to rotate, so the surface contains the above-mentioned fine powder of the present invention, which is a developer carrier. By rotating the non-magnetic cylinder 4b having the coating layer in the same direction as the electrostatic image holding surface 1, the insulating magnetic toner 11 sent from the developer container 12 is applied onto the non-magnetic cylindrical surface, and the cylindrical surface is Due to the friction between the and toner particles,
Gives toner particles a charge of opposite polarity to the electrostatic image charge. Furthermore, by arranging the iron doctor blade 10 close to the cylindrical surface (with an interval of 50 μm to 500 μm) and facing one magnetic pole (S pole in the figure) of the multipolar permanent magnet 9, the thickness of the toner layer can be reduced. Regulate thinly (30μ to 300μ) and uniformly. This cylinder 4
By adjusting the rotational speed of b, the surface speed and preferably the internal speed of the developer layer are made to be substantially equal to or close to the speed of the electrostatic image holding surface. As the doctor blade 10, a permanent magnet may be used instead of iron to form an opposing magnet. Further, in the developing section, an alternating current bias may be applied between the developer carrier and the electrostatic image holding surface.

The fine powder used in the present invention is preferably zinc oxide containing aluminum oxide as a component, and the component ratio (weight%) of zinc oxide and aluminum oxide is preferably 90 to 99.8% and 0.01 to 10%, respectively. It is possible to use ratios of 95 to 99.8% and 0.01 to 5.00%. The particle size is 100mμ~
3000 mμ is appropriate. In addition to the above, colloidal silica treated with vinyl silane is suitable.

At this time, examples of vinylsilane compounds that can be applied to colloidal silica include vinyltrichlorosilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris(β-methoxyethoxy)silane, vinyltriacetoxysilane, γ
-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltris (2-
methoxyethoxy)silane, etc. The vinyl silane-treated colloidal silica used has a particle size of about several microns to about 100 microns.

In the present invention, a member that imparts a triboelectric charge to the insulating toner is a member that comes into contact with the toner and can impart or supplementally impart the electric charge necessary for development, such as a sleeve. A toner holding member, a toner layer thickness regulating member such as a doctor blade, a scraper member for removing residual toner on the sleeve after development, and other flexible members provided in contact with the toner for imparting a triboelectric charge. and so on.

These members that apply a frictional charge to the toner are:
Preferably used in the present invention are those in which a coating layer containing the fine powder of the present invention is formed on the surface of a substrate such as a metal such as aluminum, iron, or stainless steel, or an elastic body such as synthetic rubber, glass, or elastomer. .

As a method for forming the coating layer containing the fine powder of the present invention on the surface of the triboelectric charging member or toner carrier, acids such as acetic acid and phenol, lower alcohols such as methanol, ethanol, propanol, and butanol, or Halogenated hydrocarbons such as chloroform and trichlorobenzene, or monochlorobenzene, trichlorobenzene,
halogenated aromatic hydrocarbons such as, or water,
A binder resin that can be dissolved therein, such as an acrylic resin, an alkyd resin, a silicone resin, or a styrene resin, is added to a solvent selected from known solvents such as esters, aromatic hydrocarbons, and ketones.
The fine powder of the present invention is added and dissolved in an amount of 0.1 to 10.0% by weight, and then the fine powder of the present invention is suspended, and the triboelectric charging member is coated in the resulting suspension solution by a known coating method such as a dipping method.

The insulating toner to be applied to the present invention is composed of a binder resin and additives such as a colorant, a charge control agent, a fixing aid, and an anti-caking agent, and any known materials can be used.

As the binder resin for the toner, monopolymers of styrene and its substituted products such as polystyrene, polyP-chlorostyrene, and polyvinyltoluene; styrene-P-chlorostyrene copolymers, styrene-propylene copolymers, and styrene-vinyl Toluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-
Ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer,
Styrene-butyl methacrylate copolymer, styrene-alpha chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-
Styrenic copolymers such as acrylonitrile-indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer; polymethacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polymethylethylene, Polypropylene, polyester, polyurethane, polyamide, epoxy resin, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenolic resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, Parafine wax and the like can be used alone or in combination.

Additives such as colorants, charge control agents, fixing aids, and anti-caking agents include carbon black, various dyes and pigments, and talc.

Furthermore, when used as a magnetic toner, the magnetic powder may include ferromagnetic elements and alloys and compounds containing these, such as magnetite,
It is sufficient to contain fine powder of substances conventionally known as magnetic materials, such as alloys and compounds of iron such as hematite and ferrite, cobalt, nickel, and manganese, and other ferromagnetic alloys. Hereinafter, the present invention will be explained in detail with reference to Examples.

Example 1 Alkyd resin 5 parts by weight aluminum oxide-containing zinc oxide fine powder (ZnO: Al ₂ O ₃ =
98.5:1.5%, component ratio) (average particle size 1650mμ)
20〃 A 50mmφ aluminum cylinder was immersed in a fine powder dispersed resin solution consisting of 500〃 methyl ethyl ketone, pulled up, and heated to 50℃ and 10mmHg.
This was dried in a vacuum dryer to obtain a cylinder containing fine powder on the surface, which was used as a developing sleeve.

On the other hand, an insulating layer made of polyester resin, CdS
The surface of the insulating layer of the photosensitive drum 1 made of a conductive substrate and a photosensitive layer consisting of acrylic resin and acrylic resin is uniformly charged by +6KV corona discharge at a drum surface speed of 110 mm/sec, and then the original image is irradiated simultaneously.
After performing a 7KV AC corona discharge, the entire surface is uniformly exposed to form an electrical latent image on the surface of the photoreceptor.
This latent image is formed on the sleeve 4 as shown in FIG.
b. Sleeve surface magnetic flux density 700 Gauss, sleeve rotating magnet roll 9 fixed (sleeve circumferential speed is the same as that of the drum, direction is opposite) with a distance between the ear cutting blade 10 and the sleeve surface of 0.2 mm. Set the distance between sleeve surfaces to 0.25mm,
70 parts by weight of styrene-butyl acrylate copolymer,
30 parts by weight of styrene-maleic acid copolymer, magnetic powder
Using an insulating magnetic developer consisting of 70 parts by weight and 2 parts by weight of a charge control agent, under high temperature and high humidity (35°C, 85% RH)
Then, the powder image was transferred while irradiating +7 KV direct current corona from the back side of the transfer paper and fixed by heating. Even under high humidity conditions, images with high image density and good fine line reproduction and no trailing were obtained. Furthermore, 2
The image after 10,000 copies had no deterioration in image quality and maintained its initial high image density. In addition, when the image was produced in almost the same way at low humidity (15℃, 10%),
Good images were obtained with very little decrease in image density. At this time, the charge amounts of the magnetic toner and the fine powder are -
They were 15.2 μc/g and +0.98 μc/g.

To measure the amount of charge by the blow-off method in the present invention, first, the test substance and iron powder having a particle size of 200/300 are sufficiently mixed at a ratio of 1:10. Then, 0.5-1.5 g of the mixture is precisely weighed, placed on a 100 mesh metal screen connected to an electrometer, and suctioned from below with a pressure of 25 _cmH2O . The amount of charge per unit weight is determined from the amount of toner separated and attracted at this time and the amount of charge indicated by the electrometer.

Example 2 100 parts by weight of zinc oxide, 20 parts by weight of styrene-butadiene copolymer, 40 parts by weight of n-butyl methacrylate, 120 parts by weight of toluene, 1% rose bengal.
A mixture consisting of 4 parts by weight of methanol solution was dispersed and mixed in a ball mill for 6 hours. This was applied to a 0.05 mm thick aluminum plate using a wire bar so that the dry coating thickness was 40 μm, and the solvent was evaporated with hot air. A zinc oxide-binder type photoreceptor was prepared. This photoreceptor was subjected to -6 KV corona discharge to uniformly charge the entire surface, and then an original image was irradiated to form an electrostatic latent image.

Styrene resin 10 parts by weight Vinyltrichlorosilane-treated colloidal silica
A stainless steel cylinder with a diameter of 32 mm was immersed in a suspension solution of 50% toluene and 500% toluene, pulled up and dried to form a vinyl silane-treated colloidal silica coating layer.

The latent image was developed using this cylinder as a sleeve, fixed with a rotating sleeve magnet (sleeve circumferential speed was the same as that of the drum, but the direction of rotation was opposite), with a magnetic flux density on the sleeve surface of 700 Gauss and a distance between the ear cutting blade and the sleeve surface of 0.2 mm. Set the distance between the photosensitive drum surface and the sleeve surface to 0.25 mm, and
Styrene-butyl acrylate copolymer was tested by applying 200Hz, 600V AC and -150V DC bias.
90 parts by weight, 10 parts by weight of styrene-butyl acrylate-aminoethyl methacrylate copolymer, 60 parts by weight of magnetic powder
parts by weight, and 0.3 parts by weight of hydrophobic colloidal silica in a high temperature and high humidity environment (35℃, 85%
RH), then - from the back of the transfer paper.
Transfer the powder image while irradiating with 7KV DC corona,
Heat-fixed. The images obtained were as clear and high-resolution as those under normal humidity, and there was almost no trailing fog. At this time, the amount of charge of the magnetic toner used in Example 2 and the fine powder forming the coating layer on the stainless steel cylinder was +10.3 .mu.c/g and -1.34 .mu.c/g, respectively, according to the method described above.

Comparative Example 1 Images were produced under high temperature and high humidity in the same manner as in Example 1 except that the fine powder was aminosilane-treated colloidal silica, but the image quality was significantly deteriorated with trailing and fogging, making it impractical for practical use. The image was judged to be unacceptable. The amount of charge of the aminosilane-treated colloidal silica was +105.8 μc/g.

Comparative Example 2 Initial image formation was carried out under high temperature and high humidity in the same manner as in Example 2, except that the fine powder was polyvinylidene fluoride having a charge amount of -19.7 μc/g, and furthermore, a continuous durability test of 10,000 sheets was carried out. However, in terms of image quality, there was unevenness on the sleeve and severe trailing on the lines. The durability performance was also unsatisfactory, with a severe decrease in image density.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration diagram of an example of a copying device or a recording device. FIG. 2 is a sectional view of one embodiment of a developing process to which the present invention is applied. 1... Electrostatic image holder, 4... Developing device, 4a...
...Developer carrier, 4b...Nonmagnetic cylinder, 9...Multi-polar permanent magnet, 10...Doctor blade, 11...
...Magnetic toner.

Claims (1)

[Scope of Claims] 1. In a method of developing an electrical latent image using a triboelectrically charged insulating toner, at least the surface of a member that imparts a triboelectric charge to the insulating toner is charged as shown in the following formula. applying a triboelectric charge to the insulating toner with a member containing fine zinc oxide powder containing aluminum oxide or fine silica powder treated with vinyl silane, and developing an electrical latent image with the triboelectrically charged insulating toner; A developing method characterized by: 1/40<|B|/|A|<1/2, |A|>|
B | (In the formula, A indicates the amount of charge of the insulating toner, and B
represents the amount of charge of fine zinc oxide powder containing aluminum oxide or fine silica powder treated with vinyl silane. ) 2 The component ratio (weight%) of alumina oxide is 0.01 to 10
% range of the developing method according to claim 1. 3. The developing method according to claim 1, wherein the member that applies a frictional charge to the insulating toner is a developing sleeve. 4. The developing method according to claim 1, wherein the member that applies a triboelectric charge to the insulating toner is a toner layer thickness regulating member.