JPH02184861A - Image forming method - Google Patents

Abstract

PURPOSE:To prevent deterioration of image density due to lowering of triboelectrifiability of a toner, fogging, and occurrence of fringes by incorporating fine organic polymer particles coated the cores of the polymer particles with an ion conductive resin in a developer. CONSTITUTION:An electrostatic charge latent image formed on a photosensitive body 10 is developed 23 with a developer containing the fine organic polymer particles coated the cores of the polymer particles with the ion-conductive resin, the formed toner image is electrostatically transferred, and then, the photosensitive body 10 with the toner left on it is cleaned by a cleaning roller 51 and a cleaning blade 52, thus permitting the toner particles not to be adversely affected on triboelectrifiability by coating the fine organic polymer particles as a fluidizing agent with the ion conductive resin low in electric conductivity, and accordingly, deterioration of image density due to lowering of triboelectrifiability of the toner, fogging, and occurrence of fringed to be prevented.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention is directed to developing an electrostatic latent image formed on the surface of a latent image carrier in, for example, electrophotography, electrostatic recording, electrostatic printing, etc. The present invention relates to an image forming method.

[Technology background]

In general, in electrophotography, a latent image carrier (photoreceptor) having a photosensitive layer made of a photoconductive material is given a static charge of -, and then the surface of the photoreceptor is exposed to light. An electrostatic latent image corresponding to the document is formed, and this electrostatic latent image is developed by a developer conveyed to a developing area by a developer conveying carrier (sleeve) to form a toner image. This toner image is transferred to a transfer material such as paper and then fixed by heating, pressure, etc. to form a copy image. On the other hand, after the transfer process, the photoreceptor is neutralized, and then the residual developer after the transfer is cleaned, and then the photoreceptor is used for forming the next copy image.

In order to achieve good development through the above process, good charging efficiency of the toner and stable conveyance of the appropriate ft of toner to the development area by the sleeve are required, and for this purpose, the toner must have high fluidity. is necessary.

The charging efficiency depends on the distance from the toner material in the triboelectrification series of the material that becomes the frictional pair of the toner particles, the area of the frictional pair, or the number of frictional opportunities. Therefore, when a suitable friction pair is not available, such as in a one-component developer, toner particles are caused by friction between each other or the friction area of the toner particles located at approximately the same position in the triboelectrification series, or by friction with a sleeve, a developer stirring member, etc., which have little opportunity.

As a means to remedy such charging inefficiency or to improve charging efficiency, a fluidizing agent such as silicon oxide fine particles is added.

The shape of the fluidizing agent is fine particles that are close to spherical or cubic, and adhere to the surface of the toner particles and exert a colloidal effect.
In addition, the particles themselves are electrically charged and provide Coulomb repulsion between the toner particles, thereby increasing the fluidity of the toner particles and preventing agglomeration.

For negatively chargeable toner, silicon oxide fine particles, which are themselves negatively charged, are used, and in this case, they act as a fluidizing agent as well as a charging aid.

[Disadvantages of conventional technology]

In order for the fluidizing agent to exert its power, it must sit uniformly on the surface of the toner particles.

However, in reality, many silicon oxide particles do not sit sufficiently due to electrostatic repulsion between them and remain free.

In addition, the attachment force is unstable and it is easy to detach. or,
Part of the toner may aggregate on the surface.

Therefore, the function as a charging aid and fluidizing agent becomes insufficient, leading to a decrease in image density and unstable transportability.

Furthermore, free silicon oxide may film on the sleeve, causing image defects (fogging, fringing),
This may cause poor cleaning (black spots).

In the case of negatively charged toner, electrostatic repulsion with the toner is also applied, so the above-mentioned drawback becomes more pronounced.

On the other hand, residual toner remaining on the photoreceptor after the transfer process is
In order to stably form good copy images many times, it is necessary to perform good cleaning.

Conventionally, a cleaning device for carrying out a cleaning process has a cleaning blade placed in contact with a photoreceptor, but paper dust, rosin, talc, etc. generated from the transfer material, and corona inside the device are removed. It was extremely difficult to sufficiently scrape off discharge products and toner material foreign matter fused and fixed on the surface of the photoreceptor with a cleaning blade.For this reason, recently silicone rubber, urethane rubber, fluoride A cleaning roller made of an elastic material such as rubber is placed in pressure contact with the surface of the photoconductor, and the cleaning roller has a relative speed to the photoconductor to forcibly rub the surface of the photoconductor to remove residual toner on the photoconductor. A method of cleaning was proposed.

However, when the cleaning roller is placed in contact with the photoreceptor with enough pressure to scrape off the foreign matter, residual toner is deformed by the squeezing force in the contact area between the photoreceptor and the cleaning roller and melted onto the surface of the photoreceptor. A fusion phenomenon occurs.

In addition, in order to scrape off residual toner or foreign matter adhering to the surface of the cleaning roller, a school made of polyethylene film, phosphor bronze plate, etc. may be placed in contact with the cleaning roller, or since the cleaning roller is made of an elastic material, the surface of the roller may be removed. It is difficult to completely scrape off the deposits on the surface, and some of the residual toner or foreign matter that has been transferred from the photoconductor to the cleaning roller may slip through the scraper and return to the contact area between the cleaning roller and the photoconductor. The deformed adhesion is strengthened by the rough squeezing pressure, and when this cycle is repeated, the deformed residual toner eventually becomes firmly fused to the surface of the photoreceptor, resulting in severe cleaning failure.

In addition, in magnetic toner, magnetic powder is contained in the binder resin particles, but if this magnetic powder is exposed from the binder resin particles or exists in a free state, the photoreceptor and cleaning roller may be damaged. The magnetic powder is caught in the contact area of the cleaning roller, causing deep scratches on the surface of the photoreceptor or cleaning roller.

On the other hand, even in the case of a two-component developer, the carrier attached to the photoreceptor is caught in the contact area between the photoreceptor and the cleaning roller, causing scratches on the surface of the photoreceptor or the cleaning roller.

In order to solve the above problems, it has been proposed to add organic fine particles smaller than toner resin particles to developer toner. In the proposed developer, since organic fine particles smaller in diameter than toner resin particles coexist, the physical adhesion of the toner to the photoreceptor is weakened by the lubricating action of the small-diameter organic fine particles due to the colloid effect. Therefore,
In a cleaning device that uses both a cleaning roller placed in contact with the photoconductor and a cleaning blade placed downstream of the cleaning roller in contact with the photoconductor, even if the pressure of the cleaning roller against the photoconductor is reduced during the cleaning process, residual It is possible to remove toner well, and even in the final cleaning process, a considerable amount of residual toner is removed by the cleaning roller, and the physical adhesion of residual toner is weak. Even if the pressure of the blade against the photoreceptor is reduced, residual toner can be removed satisfactorily. As a result, residual toner can be effectively cleaned without damaging the photoreceptor or cleaning blade.

In addition, since the organic fine particles provide appropriate polishing performance, foreign matter such as toner substances or paper dust attached to the surface of the photoreceptor can be removed by polishing, which also improves cleaning performance. can be achieved.

However, the addition of organic fine particles causes the toner to lose its original chargeability, leading to a decrease in image density due to the decrease in the chargeability of the toner, and to the occurrence of fogging and fringes.

In addition, when subjected to mechanical load from the stirring system in the developing device, organic fine particles are detached from the toner surface, causing image stains due to filming on the sleeve, and furthermore, the charge amount distribution of the toner becomes unstable and the image density decreases. Deterioration, fogging, and fringing occur.

Furthermore, the cleaning performance in the above process is degraded, and cleaning defects such as dark spots and horizontal streaks occur.

[Purpose of the invention]

In view of the above-mentioned circumstances, an object of the present invention is to provide an image forming method that maintains good toner transportability, transferability, and cleaningability to ensure high image density and long life of the photoreceptor.

[Structure and effects of the invention]

The object of the present invention described above is to develop an electrostatic latent image on a photoreceptor with a developer, and after electrostatically transferring the generated toner image,
In an image forming method in which toner remaining on a photoreceptor is cleaned using a cleaning roller and a cleaning blade, the developer contains organic polymer fine particles having a fine particle attached polymer core coated with an ion conductive resin. This is achieved by an image forming method characterized by:

In the present invention, since the organic polymer fine particles of the fluidizing agent are coated with the ion conductive resin having low electrical resistance, there is no adverse effect on the triboelectric charging property (Q/M) of the toner particles. In addition, the toner particles stably sit on the surface of the toner particles due to Coulomb force, and are less likely to come off, so a stable flow effect can be provided. Even if it separates, there will be no change in the amount of triboelectric charge on the toner. Therefore, a well-balanced band TL amount, uniform charge amount distribution, and stable conveyance are maintained, development is stable, images with high maximum density are produced, fogging and fringing are prevented, and developer life is maintained. is also longer.

Furthermore, due to the stable roller action, no scratches occur on the photoreceptor surface due to cleaning, and a good cleaning effect is maintained.

In order to impart electrical conductivity to the resin, a method is adopted in which conductive materials such as metal powder, carbon black, etc. are dispersed in the resin matrix, or an ionic conductive factor is introduced into the resin molecules.

The ion conductive resin according to the present invention has an ion conductive functional group introduced into the main chain or side chain of a polymer. In the present invention, the functional group is a carboxy group, a sulfo group, a sulfoester group, a phospho group, etc., and these functional groups have a monovalent cation such as sodium, potassium, or ammonium as a counter ion.

Specific examples of the resin include polyacrylates, polymethacrylates, styrene-maleic acid copolymer salts, and polystyrene sulfonic acid polymers. In addition, "Gosef Eimer 8 640 (styrenic resin)" (
There are commercially available products such as those manufactured by Nippon Gosei Kagaku Kogyo Co., Ltd.

Most of these resins are water-soluble, and a preferable level of conductivity is a surface resistivity in the range of 10 6 to 10 cm. When it is less than 10'ΩcLll, toner transfer failure occurs, and when it exceeds 10’Ωcm, the toner charge amount (Q/M) tends to fluctuate and the maximum density (Dmax) becomes unstable.

As a method for coating organic polymer fine particles with the ion conductive resin according to the present invention, a dipping method or the like is used.

As for the amount of coating, aim for an amount that can uniformly cover the entire surface of the organic polymer fine particles, and aim for a coating amount of 0. O1~3, Ovt%
, preferably 0.1-2. Qvt%.

Organic polymer fine particles have a smaller diameter than toner particles, and are, for example, secondary particles (particles separated into individual unit particles).
It is preferable that the average diameter is 0.01 to 5 μm, and particularly preferably about 0.1 to 2 μm. When the average diameter of the organic polymer fine particles is too large, the fluidity of the toner decreases, leading to insufficient transportability of the toner to the development area, which tends to cause a decrease in image density.

On the other hand, if the average diameter of the organic polymer fine particles is too small, sufficient leaning properties cannot be obtained.

The proportion of organic polymer fine particles is 0.01 to 3% of the total toner.
vt% is preferred, particularly 0.1 to 2 vt%.

If the proportion of the organic polymer fine particles is too small, the fluidity of the toner decreases, leading to insufficient transportability of the toner to the developing area, which tends to cause a decrease in image density, and also makes it impossible to obtain sufficient leaning properties.

Furthermore, when the proportion of organic polymer fine particles is excessive, triboelectric charging of the toner is inhibited.

The organic substance for forming the core of the organic polymer fine particles is not particularly limited, and vinyl polymers are preferred because they are relatively hard. Vinyl polymers can be produced by various polymerization methods such as emulsion polymerization and suspension polymerization, but emulsion polymerization is preferred because it can effectively produce small-diameter, spherical organic particles. In particular, in systems where the monomer itself for obtaining the vinyl polymer has an emulsifying effect, it is preferable to obtain the vinyl polymer by emulsion polymerization without using an emulsifier.

Examples of the vinyl polymer include acrylic polymers, styrene polymers, vinyl group-containing fluororesins, and among them, acrylic polymers are preferred.

In the present invention I, inorganic fine particles may be used in combination as a fluidizing agent. For practical purposes, the average diameter of the primary particles of the inorganic fine particles is preferably 2 μm or less, and particularly preferably 1 μm or less.

The amount of inorganic fine particles added is 0.05 to 2.0% of the total toner. O
W [% is preferred, particularly 0.1-1.0 wt% is preferred.

The constituent materials of the inorganic fine particles are not particularly limited; for example, oxides such as Lika, titanium oxide, aluminum oxide l4, and zirconium oxide; nitrides such as silicon nitride and boron nitride; silicon carbide, aluminum carbide, titanium carbide, etc. Carbides and others may be mentioned. These inorganic fine particles may be surface-treated.

In particular, Rica fine particles or surface-treated Rica fine particles are preferred. As the surface treatment agent, for example, a silane coupling agent, a titanium coupling agent, etc. can be used. The surface-treated phosphor particles have high stability against environmental changes such as temperature and humidity, so that the environmental dependence of the triboelectric charging property of the toner can be controlled to be small.

The organic polymer fine particles having an ion-conductive resin coating layer according to the present invention are used by being added to and mixed with toner powder and allowed to sit on the toner particles. Specifically, it is preferable to mix the toner particles and the organic polymer fine particles using a mixing device such as a V-type blender, so that the organic polymer fine particles sit on the surface of the toner particles.

! -ner particles are particles in which, for example, a magnetic substance, a colorant, an offset prevention agent, a charge control agent, etc. are contained in a binder resin.

The binder resin for the toner is not particularly limited, and various resins can be used. Specifically, examples thereof include sujishin resin, acrylic resin, styrene-acrylic copolymer resin, epoxy resin, polyester resin, and the like. These resins may be used in combination.

The styrene-acrylic copolymer resin used as the binder resin is a resin made of a copolymer of a styrene monomer and an acrylic monomer.

Examples of magnetic substances include substances that are strongly magnetized in the direction of a magnetic field, such as metals or alloys that exhibit ferromagnetism such as iron, ferrite, and magnetite, such as iron, nickel, and cobalt, or compounds containing these elements. be able to. The average particle size of the magnetic material is 0.1-1 μm. The content ratio of the magnetic material is 20 to 80 wt%, especially 30 to 70 wt% of the whole toner when it is used as a -component developer.
Preferably, it is wt%.

Examples of colorants include carbon black, chrome yellow, DuPont oil red, quinoline yellow, phthalonanine blue, malachite green offsalate,
Examples include lamp blanks.

Examples of the offset preventing agent include low softening point polyolefins, high melting point paraffin waxes, silicone varnishes, fatty acid esters or partial oxides thereof, fatty acid amide compounds, higher alcohols, and the like.

Examples of the charge control agent include metal complex dyes, nigrone dyes, ammonium salt compounds, and the like.

Next, each step of the image forming method of the present invention will be specifically explained.

(Developing process) A single-component developer or a two-component developer having a specific toner as described above is carried on a sleeve in a layered manner, and this is conveyed to a developing area, where the static image formed on the surface of the photoreceptor is removed. Develop the electrolatent image.

The sleeve can be composed of, for example, a cylindrical sleeve on which a developer layer is supported, and a magnet body having a plurality of magnetic poles arranged inside the sleeve, and the rotation of the sleeve and/or the magnet body causes The developer layer on the sleeve is transported to a development area.

The thickness of the developer layer supported on the sleeve is controlled by a regulation blade provided upstream of the development area of the sleeve to regulate the thickness of the developer layer in order to maintain even and uniform development. It is preferable to trim the length to a certain level. The regulating blade is made of magnetic or non-magnetic material.

In the developing region, a DC voltage or a voltage obtained by superimposing an AC voltage on a DC voltage can be used as a bias voltage, if necessary. The DC voltage can prevent toner particles from adhering to the background area other than the electrostatic latent image area, and the AC voltage can improve the adhesion of toner to the electrostatic latent image.

(Transfer process) A transfer device that generates corona discharge is placed so as to face the photoconductor through the transfer body, and the surface of the photoconductor is transferred using an electrostatic transfer method that applies direct current corona discharge to the transfer body from the back side. The toner carried on the transfer member is transferred to the surface of the transfer member.

(Cleaning process) Using a cleaning device that uses both a cleaning roller placed in contact with the photoconductor and a cleaning blade placed in contact with the photoconductor on the downstream side, residual toner remaining on the photoconductor without being transferred is removed. Clean.

Specifically, residual toner remaining on the photoreceptor without being transferred is first cleaned by a rotating cleaning roller in a soft state on the photoreceptor.

Then, residual toner not removed by the cleaning roller is further cleaned by a cleaning blade.

It is preferable that the cleaning roller be placed so that it makes light contact with the photoconductor, and in the contact area, it is preferable that the cleaning roller forcefully rubs the contact surface with a relative speed to the photoconductor. They may also be rotated at high speeds in the same direction.

Further, it is preferable that a scraper for scraping off residual toner adhering to the cleaning roller is disposed in contact with the cleaning roller.

In addition, in order to facilitate cleaning, it is preferable to add a static electricity removal process to remove static electricity from the surface of the photoreceptor in the oil film in this cleaning process. This static elimination step can be performed, for example, using a static eliminator that generates AC corona discharge.

In the cleaning step, the developer according to the present invention is extremely effective in increasing the cleaning effect.

(Fixing process) The transfer material onto which the toner image has been transferred in the transfer process is subjected to a fixing process using a heat fixing device, a pressure fixing device, etc.
A fixed image is formed by contact.

FIG. 1 is an explanatory diagram showing an example of an image forming apparatus that can be used in the image forming method of the present invention. In the figure, IO is a photoreceptor, 21 is a charger, 22 is an exposure optical system,
23 is a developing device, 25 is a static elimination lamp, 26 is a transfer electrode,
27 is a separation electrode, 28 is a static elimination electrode, 29 is a fixing device, 40
50 is a document table, and 50 is a cleaning device. This apparatus is of a type in which the exposure optical system 22 is fixedly arranged and the document table 40 is moved.

The surface of the photoreceptor IO is uniformly charged by the charger 21,
The surface of the charged photoreceptor 1O is exposed to the original by the exposure optical system 22, and an electrostatic latent image corresponding to the original is formed on the photoreceptor 1O. This electrostatic latent image is developed by a developing device 23 to form a toner image.

After the toner image thus obtained is neutralized by the static eliminating lamp 25 and is in a state where it can be easily transferred, the toner image is transferred to the transfer electrode 2.
6, the image is transferred onto the transfer paper P. Transfer paper P is separated electrode 2
It is separated from the photoconductor IO by 7 and subjected to fixing processing by a fixing device 29 to form a fixed image.

On the other hand, the photoreceptor lO is neutralized by the static eliminating electrode 28, and residual toner is scraped off by the cleaning device 50.

The cleaning device 50 in this example includes a cleaning roller 51 and a cleaning blade 52 disposed downstream thereof, and a scraper 53 is disposed at the cleaning effect 51.

The cleaning blade 52 is made of an elastic material such as hard urethane rubber with a thickness of 1 to 3 mo+, and has a length substantially corresponding to the width of the photoreceptor IO (in the direction perpendicular to the plane of the paper in FIG. 1). , is held switchably between a pressure contact position and a pressure release position by a blade holder (not shown).

The cleaning roller 51 has an outer diameter of 5 to 25 ai1, for example.
The surface of one metal cylindrical body is coated with an elastic body such as urethane comb, silicone rubber, sponge-like urethane rubber, or fluorine rubber having a thickness of about 1 to 5III11. The cleaning roller 51 is supported by a support member (not shown) on the upstream side of the cleaning blade 52 so as to be lightly pressed against the surface of the photoreceptor 10 . The cleaning roller 51 may be a driven roller that rotates as the photoreceptor 10 rotates, or a drive roller that is forcibly rotated so that the rotation direction at the contact portion with the photoreceptor IO is in the same direction. It is preferable that this is the case, and it is particularly preferable that the photoreceptor iQ be forcibly rubbed at a relative speed.

The cleaning roller 51 also has the function of conveying the remaining particles scraped by the cleaning blade 52 and falling toward the scraper 53. That is, the cleaning roller 51 causes the residual toner scraped by the cleaning blade 52 to fall toward the cleaning roller 51, or the residual toner that has fallen due to the rotation of the cleaning roller 51 to be removed one after another by the scraper 53.
Since the residual toner is conveyed to the cleaning blade 152, there is no problem that the residual toner remains at a position directly below the cleaning blade 152.

The scraper 53 is made of a thin layer of material such as polyethylene terephthalate. This scraper 53
As a result, residual toner on the cleaning roller 51 is scraped off.

〔Example〕

Examples of the present invention will be specifically described below, and the present invention is not limited to these Examples.

Example 1 (1) Creation of organic polymer fine particles coated with ionic resin
Organic polymer fine particles (produced component: polymethyl methacrylate, -order particle average particle size: 0.4 μa+) are dispersed in a methanol solution in which m; manufactured by Nippon Gosei Kagaku Kogyo Co., Ltd.) is dissolved. Next, the methanol solvent is evaporated, and the ion conductive resin is fixed to and coated on the fine particles.

(2) Preparation and evaluation of developer Polyester resin 60 parts by weight Magnetite 35 parts by weight Low molecular weight polypropylene 3 parts by weight Salicylic acid derivative 2 parts by weight The above raw materials were mixed, kneaded, crushed, and classified to have an average particle size of 11.
Toner particle powder of 5 μm was obtained.

Q
, 4wt%, and hydrophobic silica fine powder (R-812 manufactured by Nippon Anilozil Co., Ltd.) were added and mixed in an amount of 6wL% to obtain a -component developer.

Using the -component developer, the apparatus is equipped with a cleaning device having the same structure as shown in FIG. 1, which includes a photoreceptor made of an organic photoconductive photoreceptor, a developing device for the -component developer, a cleaning roller, and a cleaning blade. With an electrophotographic copying machine,
5 under the environmental conditions of temperature 20''C and relative humidity 55%.
We conducted 0,000 live-action tests.

The conveyance and transferability of the image agent that achieves this formation is good, and the image density is 1.
．． 25, and an image with good gradation without fogging or fringing was stably obtained. Also, toner scattering, black spots,
There were no image defects such as horizontal lines or streaks caused by the marks of the cleaning blade, and no damage to the photoreceptor, and the durability was good.

Comparative Example (1) In the production of the developer of Example, organic polymer fine particles without any treatment (main component polymethyl methacrylate) were used instead of organic polymer fine particles coated with ion conductive resin.
A comparative developer was obtained in the same manner except that the average diameter of the secondary particles was 0.4 μm.

When this comparison developer was used as a one-component developer and an actual photographing test was conducted in the same manner as in the example, the image density decreased to 1.15 after 10,000 times, and fogging occurred. Further, after 20,000 times, horizontal lines due to the marks of the cleaning blade appeared in the copied image, and after that, black spots started to appear and gradually increased.

The results of Examples and Comparative Examples are summarized in a vestibule.

table FIG. 2 is an explanatory diagram showing an example of an image forming apparatus that can be used.

IO...Photoreceptor 21...Charger 22...
・Exposure optical system 23...Developer 25...Static elimination lamp 26...Transfer electrode 27...Separation electrode
28...Static elimination electrode 29...Fixing device 40...Document table 50...Cleaning device 51...Cleaning roller 52...Cleaning blade 53...Scraper In the embodiment of the present invention, the toner Dmax, which is an index of the quality of conveyance performance and transferability, is a high density, and there is no decrease in density due to the Covey number, and development is stable. In addition, the fog level is low, and the increase in copying is also small. The cleaning rate is also good, and there are no scratches on the photoreceptor.

[Brief explanation of the drawing]

Claims (1)

[Claims] In an image forming method in which an electrostatic latent image on a photoreceptor is developed with a developer, the generated toner image is electrostatically transferred, and then the toner remaining on the photoreceptor is cleaned using a cleaning roller and a cleaning blade. . An image forming method, wherein the developer contains organic polymer fine particles having a fine organic polymer core coated with an ion-conductive resin.