JPH0546018A - Image forming method - Google Patents

Abstract

PURPOSE:To form an image which has good quality and is excellent in life time. CONSTITUTION:Developer obtained by associating at least particulates being polymerization monomer and polymer particles obtained by including and polymerizing colorant and releasing agent and mixing carrier in toner consisting of unfixed particles whose average particle sizes are 3-7mum is supplied to a developing area by rotating a sleeve 2 being a developer carrier incorporating a magnet M inside in a reverse direction to a latent image carrier and rotating the incorporated magnet M in the same direction as the latent image carrier.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method for non-contact development of an electrostatic latent image using a two-component developer.

[0002]

BACKGROUND OF THE INVENTION Developers used in dry development of electrostatic latent images include a one-component developer to which a magnetic toner is applied for toner image formation and a two-component developer to which a carrier and an electrostatic triboelectrifying resin toner are applied. is there.

Further, as a developing method, a non-contact developing method such as a contact developing method in which toner particles rub and contact the electrostatic latent image surface and a jumping method in which charged toner particles fly and seat on the electrostatic latent image surface by an electric field force are used. There is.

In most recent multicolor developing methods, a two-component developer that does not cause color turbidity and a non-contact developing method that does not damage the preceding seated toner image are mostly used in combination.

As a developing method, a way to obtain high image quality is to convey a uniform thin layer developer in which the constancy of the developer composition is kept to a developing region, a magnetic balance between carrier magnetism and a magnet built in a developer carrier, A wide range of conditions such as operating conditions, bias potentials in the developing area, alternating voltages, their combinations, balance between conditions, etc. must be optimally selected according to the design function of the copying machine. There is no.

Regarding the image quality, of course, various considerations for development are reserved from the viewpoint of the developer, and it is necessary to examine the composition of toner and carrier particles, the particle size of particles, the particle size distribution or rheology.

Further, the developer includes a fine grain additive to be dispersed and contained in the developer powder system for complementing various functions such as fluidity and chargeability. Mutual fusion between particles contained in the powder system, particularly small amount. Performance deterioration due to selective wear of developer particles due to adhesion of particles to large particles, filming on equipment wall, destruction by shearing force, pre-consumption from qualified particles, etc.,
Loss of service occurs.

On the other hand, the suspension polymerization of the toner or the particle morphology such as the core-shell structure of the carrier particles has also been studied, and attention has been paid to the advantages of the spherical particles such as fluidity, chargeability and morphological structure strength, and they are appropriate. Although the utility has been demonstrated, it has been known that, despite the advantage, spherical toner particles cause cleaning failure depending on the conditions.

In a multicolor image, since a slight difference in color tone is sensitively detected, color mixture due to poor cleaning is not preferable.

The problems listed above often occur synergistically and require a combinatorial solution.

[0011]

OBJECTS OF THE INVENTION It is an object of the present invention to address the aforementioned problems,
(1) A fine toner and a carrier are used to provide a high-quality image with good sharpness, and a high scraping effect in cleaning does not give a background fog. (2) A jumping developability is good and a latent image carrier of the carrier is provided. (3) to provide an image forming method by non-contact development in which the developing density is stable and the selective abrasion to the developer particles is not caused.

[0012]

The above object of the present invention is to further associate at least fine particles of a polymerizable monomer with polymer particles containing a colorant and a release agent and polymerize them to form an irregular average particle diameter of 3 to 7 μm.
The toner prepared by mixing the carrier with the toner composed of the particles is rotated by rotating the sleeve and the sleeve of the developer carrier having a magnet inside in the opposite direction to the latent image carrier and the built-in magnet in the same direction. It is achieved by an image forming method characterized in that the non-contact development is carried out by supplying it to a developing area.

In the embodiment of the present invention, (1) the developer carrier is a core-shell particle whose surface is coated with a charge control resin for adjusting and complementing the chargeability by using ferrite of 20 to 100 μm as a core particle. Preferably, (2) the magnetic flux density of the magnet contained in the developer transport body is in the range of 600 to 1500 gauss. Further, in (3) development, it is preferable to apply an alternating electric field between the developer carrier and the latent image carrier.

The present invention will be described in detail below.

The polymerized toner of the present invention has a novel shape obtained by utilizing the suspension polymerizability. That is, first, a composition containing a polymerizable monomer, a colorant, and a release agent is used to form fine primary particles, and the associated particles are obtained by further proceeding the polymerization. A polymerized toner having an irregular shape and having a particle size of 3 to 7 μm.

Here, the fine primary particles are fine suspension particles having a substantially spherical diameter and containing components necessary for a toner, which are obtained by a suspension polymerization method. Basically, the polymerized toner of the present invention is one in which a large number of such fine primary particles are agglomerated and each particle is in an associated state, and in the surface layer portion of the particles, the polymerized and bonded aggregated particles, The shape thereof has an indefinite shape such as a Konpeito sugar shape or a grape tuft shape. The particle size of the associated particles is in the range of 3 to 7 μm. If the particle size is 3 μm or less, the stability of the charge amount is poor and fogging easily occurs, and if it is 7 μm or more, the resolution and sharpness deteriorate.

Next, the manufacturing method of the present invention will be described.

The polymerizable monomer used in the suspension polymerization in the present invention is preferably a monomer having an ethylenically unsaturated double bond, specifically, a styrene-based monomer,
Alternatively, an acrylic acid ester-based monomer is used.
Examples of the styrene-based monomer include styrene, vinyltoluene, ethylstyrene, p-chlorostyrene, pn-butylstyrene and the like, and preferably styrene or vinyltoluene is used. Examples of the acrylate-based monomer include ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, methyl acrylate, methyl methacrylate, propyl acrylate, propyl methacrylate and the like, preferably acrylic acid Butyl, butyl methacrylate or methyl methacrylate are used. These monomers may be used alone or in a mixture, and if necessary, N, N-dimethylaminoethyl methacrylate, N, N-diethylaminoethyl methacrylate, and a cationic cation such as vinylpyridine. Monomers or anionic monomers such as unsaturated fatty acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, and maleic anhydride, and unsaturated fatty acid anhydrides may be used in combination.

The colorant can be used without particular limitation as long as it has been used in conventional toners, and specifically, carbon black, iron oxide, zinc oxide, titanium oxide or the like can be used. .. The carbon black may be one that is usually used for toner such as channel black or furnace black, and has a particle size of 15 to 80.
It may be about mμ.

The addition amount thereof may be 1 to 10% by weight, preferably 3 to 7% by weight, based on the polymerizable monomer, and 1% by weight.
If it is less than 10%, the concentration is not sufficient, and if it exceeds 10 wt%, the concentration is not significantly improved, which is not economical.

Wax is used as the releasing agent, and is not particularly limited as long as it gives the toner releasability.
Examples thereof include waxes that are commonly used for toners such as polypropylene wax, polyethylene wax, and microcrystalline wax.

The amount added is 1 to 5% by weight, preferably 2 to 3% by weight, based on the polymerizable monomer. If it is less than 1 wt%, the releasability is insufficient and the offset tends to occur. Further, even if it exceeds 5 wt%, the releasability is not significantly improved, which is not preferable.

Further, a charge control agent such as nigrosine may be added.

In the present invention, the above various components are uniformly dispersed to carry out suspension polymerization. At this time, a crosslinking agent is added to the polymerizable monomer so that the polymer has a desired gelation rate. 0.1
~ 2 wt% may be added.

The gelling rate is based on the total resin content.
The content of resin insoluble in tetrahydrofuran is 50 wt% or less, preferably 45 wt% or less. Gelation rate
When it exceeds 50 wt%, the softening point of the obtained toner becomes too high, and a large amount of heat energy is required for fixing when the toner is used, which is not preferable.

As the cross-linking agent, those which are usually used may be used, for example, divinylbenzene, divinylnaphthalene, ethylene glycol dimethacrylate,
Compounds having two vinyl groups such as divinyl ether or 3 such as trimethylolpropane triacrylate
Examples thereof include compounds having a single vinyl group, and these may be used alone or as a mixture thereof.

Further, a polymerization initiator is added to the composition containing the polymerizable monomer. Any polymerization initiator may be used, for example, azobisisoptyronitrile, azobis-2,4-dimethylvaleronitrile and the like.

In the present invention, it is important to uniformly disperse and suspend these various components. To prepare such a uniform suspension, a polymerizable monomer, a colorant and an additive are mixed. In advance, under an atmosphere of an inert gas, a strong stirrer or disperser, for example, a homomixer, a homogenizer or a disperser, etc., and a rotation speed of 4000 to 10000 at 10 to 6
Achieved by vigorous dispersion for 0 minutes. The order of addition of various components at the time of preparing the suspension is not particularly limited, and may be added all at once or sequentially. Further, the temperature at the time of dispersion may be room temperature, slightly heating, or cooling, but when heating, the temperature is such that the decomposition temperature of the polymerization initiator is not reached, or the polymerization is performed. It is preferable to add only the initiator, cool it below the decomposition temperature after the end of dispersion, add it, and disperse again. Further, when heat is generated during the dispersion treatment, it is preferable to disperse while cooling, and in this case also, it is desirable to add the polymerization initiator just before the end of dispersion.

In the present invention, the dispersion time and the number of revolutions are adjusted and selected so that fine suspended particles can be obtained by occasionally observing with a microscope while performing vigorous stirring.

In the present invention, when polyvinyl alcohol having a saponification degree of 60 to 85% is used as a suspension stabilizer for obtaining such a suspension, the suspension is stabilized and the fine polymer particles described below are aggregated. It is highly preferable because it works effectively.

The suspension stabilizer polyvinyl alcohol used here may be partially etherified,
The residual ester moiety may be transesterified with a group other than an acetyl group, for example, a fatty acid residue containing a double bond such as acryloyl or methacryloyl, or a saturated fatty acid residue such as propyroyl or butyroyl, alone or in a mixture. What is important here is the range of the degree of saponification and the fact that it is water-soluble and is hardly affected by the substituents. The concentration of this aqueous suspension bath is preferably 0.05 to 4%, and the amount of the bath is preferably 1 to 10 times the amount of the suspension to be poured.

When the desired fine suspended particles are formed, suspension polymerization is carried out at 50 to 90 ° C. for 6 to 10 hours in an inert gas atmosphere, and a stirrer at that time is used to form fine suspended particles. The stirrer or disperser used may be used as it is, or
Suspension polymerization may be carried out by changing to a blade-type or anchor-type stirrer.

At that time, the spherical fine suspended particles gradually start to aggregate when the temperature is raised to a predetermined polymerization temperature, and several to several tens of fine particles are formed within 2 to 3 hours after the temperature is raised. It forms agglomerated Konpeito or grape tuft-shaped amorphous associated particles.

With further progress of the polymerization, the contact point of the associated particles is fused and the particle strength rises and the aggregate becomes stable as an aggregate.

In this way, when suspension polymerization is carried out at a polymerization temperature of 50 to 90 ° C. and a polymerization time of 6 to 10 hours, several to several tens of fine suspended particles are aggregated and polymerized, and this aggregate is formed. A polymer is obtained which forms one amorphous particle.

After the completion of the polymerization reaction, cooling, filtration, washing and drying are carried out, and further classification into a desired toner particle size gives the desired polymerized toner particles.

Iron, iron alloy or ferrite is used for the core of the carrier used in the present invention, preferably ferrite. If the ferrite core diameter is less than 20 μm, carrier filming occurs, and if it exceeds 100 μm, the toner transportability becomes poor and the image density becomes insufficient.

For the carrier shell, a styrene-acrylic resin, a fluorine resin, a silicone resin, or the like can be used alone or in combination. By covering the surface with the resin shell, it becomes possible to control the chargeability of the toner and the charge amount and charge polarity in relation to the charge control agent. Further, the high insulating property can prevent the carrier from filming on the photosensitive member in the alternating electric field.

In the developer of the present invention, various conventionally used auxiliary agents for improving the performance can be positively incorporated and used as long as the effects of the present invention are not impaired. For example, a charge control agent, an antioxidant, a fixing property improver, a lubricant or a fluidizing agent may be used in combination.

Inorganic fine particles are preferably used as a fluidizing agent in the developer of the present invention. Examples of such inorganic fine powder include silica fine powder, alumina, titanium oxide,
Barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, silica sand,
Clay, mica, wollastonite, diatomaceous earth, chromium oxide, cerium oxide, red iron oxide, antimony trioxide, magnesium oxide, zirconium oxide, barium sulfate, barium carbonate,
Calcium carbonate, silicon carbide, silicon nitride and the like can be mentioned, but silica fine powder is particularly preferable.

Further, in the present invention, when these inorganic fine particles are surface-treated with an amine-modified silicone compound, they are effective for positive charging property.

Regarding the particle size of such inorganic fine particles, the average particle size of the primary particles is preferably within the range of 3 mμ to 2 μm, particularly 5 to 500 mμ. Further, the specific surface area by the BET method is preferably 20 to 500 m ² / g. The content ratio of the inorganic fine particles is preferably 0.1 to 5 wt% of the toner, and particularly preferably 0.1 to 2 wt%.

Examples of the fixability improver include polyolefin, fatty acid metal salt, fatty acid ester and fatty acid ester wax, partially saponified fatty acid ester, higher fatty acid, higher alcohol, liquid or solid paraffin wax, polyamide wax, polyhydric alcohol. Ester, silicone wax, aliphatic fluorocarbon, etc. can be used. Especially softening point (ring and ball method JIS K2531)
A wax having a temperature of 60 to 150 ° C. is preferable.

As the charge control agent, conventionally known charge control agents can be used, and examples thereof include nigrosine dyes and metal-containing dyes.

Further, as an embodiment of the present invention, if primary and secondary antioxidants are used in combination as antioxidants, good results can be obtained. The primary antioxidant is one that inactivates radicals in the radical chain reaction of oxidation to prevent the progress of oxidation, and a phenol-based or amine-based compound has its effect, and a secondary antioxidant. Means that the generated peroxide is decomposed, and a phosphorus compound or a sulfur compound is selected.

The primary and secondary antioxidants are used in combination, and the use of two or more of these exhibits a significant synergistic effect.

The developer according to the present invention is used for developing the electrostatic image formed in the electrophotographic copying machine, and the obtained toner image is fixed by the upper heating roller fixing device electrostatically transferred onto the transfer paper. A copy image is obtained.

Next, the magnet built in the developer carrier in the developing process according to the present invention is made of Sr,
It is preferable to use ferrite such as Pb or Ba.

The magnetic flux density is preferably 600 to 1500 gauss. If it is less than 600 gauss, the carrier has a small binding force and slips on the sleeve and is not transported. If it exceeds 1500 gauss, the force between the carriers becomes large, the toner is easily crushed to half, and the spent on the carrier increases.

There is no particular limitation on the method of forming a thin layer of the developer layer which is fed to the developing area. A magnetic blade, an elastic plate, a magnetic rod, etc. may be used arbitrarily.

FIG. 1 shows an example of an apparatus used for carrying out the method of the present invention. In this example, a metallic rotary sleeve 2 is arranged so as to face the outer peripheral surface of a rotary drum type photoreceptor 1 which constitutes a latent image carrier, and the sleeve 2 is composed of a magnetic carrier and toner. A developer tank 3 for supplying the component developer P is provided, and the sleeve 2 is rotated in the opposite direction to the photoconductor 1 so as to move in the same direction as the photoconductor 1 in the developing area D. The charged developer P is supplied onto the sleeve 2 and conveyed by utilizing the action of the magnet body M, and the charged developer layer formed on the outer peripheral surface of the sleeve 2 which is regulated by the developer amount regulating member 4 is
The sleeve 2 and the photoconductor 1 are carried into a developing area D where they are opposed to each other, and in this development area D, the electrostatic charge image supported by the photoconductor 1 is developed by developing means of a non-contact developing system. Here, as the developing means by the non-contact developing method, a positive or negative DC bias voltage of about 100 to 300 V is applied as necessary in order to invalidate the background potential other than the image portion of the electrostatic image in development. Means to apply or voltage 100V to 2KV, frequency 100Hz to 5KH
Means for applying an oscillating voltage of z (eg US Pat.
Or JP-A-55-18656). B in the figure is this bias power supply. The closest distance between the surface of the photosensitive member 1 and the toner layer is usually set to 1 mm or less.

In the example of FIG. 1, the rotation direction of the sleeve 2 is such that the traveling direction in the developing area D is opposite to that of the photoconductor 1, the magnet body M is in the same direction, and the speed of the sleeve 2 is the photoconductor. It is preferable that it is equal to or more than the body 1.

This charged developer layer is then carried into the developing area D, where the toner T flies while facing the photoconductor 1 and adheres to the electrostatic charge on the photoconductor 1 by electrostatic attraction. As a result, the electrostatic image is developed.

Thus, in the present invention, as described above,
It is preferable that the toner carried into the developing area D has a sufficiently large amount of charge, and that the charged developer on the sleeve 2 is in the form of a layer having a uniform thickness and the size of the gap between this and the photoreceptor 1. Since the range is restricted, the electrostatic charge image on the photoconductor 1 can be reliably and easily developed, and eventually a good visible image can be stably formed.

Further, since the required charging of the developer can be carried out at a high speed, the developing means has a high frequency voltage higher than the conventional one, for example, a voltage of 0 to 2 KV and a frequency of 50 Hz to 50 KH.
By using a high frequency voltage of about z, high speed development can be sufficiently realized.

The toner of the two-component developer to which the method of the present invention is applied is required to have a charge retention ability, and therefore the toner T has a specific resistance of 10 ¹⁰ Ω · cm or more. preferable. Further, it is preferable that the normal particle size is within the range of 0.1 to 100 μm in view of the conditions in the developing step.

[0057]

EXAMPLES The present invention will be described in detail with reference to examples.

Example 1 In order to produce the toner according to the present invention by the suspension polymerization method, the required amount of colorant, polyolefin wax, non-polyolefin wax and other additives are first added to the polymerizable monomer. After stirring well using a sand stirrer or the like to disperse the polymerizable composition, and further adding a polymerization initiator,
It is added to an aqueous suspension medium containing a suspension stabilizer, dispersed and suspended using a high speed stirrer, and the polymerization reaction is allowed to proceed under appropriate temperature conditions. The polymerizable composition suspended as fine oil droplets in the medium is polymerized and solidified as it is to obtain spherical resin particles containing a colorant, a wax and the like. The size of the obtained resin particles is determined by the dispersed state of the suspended polymerizable composition.

Polymer particles having a particle size of 1.2 μm as described above were then added to a suspension by adding a polymerization initiator, and the particles were allowed to associate with each other to obtain a toner having irregularly-shaped associated particles having an average particle size of 5.4 μm.

The carrier is Cu-Zn ferrite (average grain size 2
The surface was coated with styrene-butyl acrylate copolymer particles by mechanical impact. These were mixed and used as a developer. Electronic copier Konica 8028
(Konica Corporation) was used for image drawing. The magnet structure in the carrier of the developing device was changed to integrate and magnetize the magnetic flux density to 800 gauss. The developer transport sleeve was rotated in the opposite direction to the photoconductor (latent image carrier), and the magnet was rotated in the same direction.

Example 2 A preferred method for producing the toner of the present invention is shown below. To the emulsion of a polymer having an acidic polar group or a basic polar group obtained by emulsion polymerization, a required amount of a colorant powder and an optional charge control agent are added and mixed to uniformly disperse the mixture, and when the mixture is continuously stirred, the polymer having a polar group is dispersed. The primary particles of the coalesced particles and the colorant particles gradually aggregate and grow. Such a dispersion is further aggregated to grow into associated particles having an average particle size of 5.3 μm.

The carrier is Cu-Mg ferrite and has an average particle size of 45.
μm.

The styrene-acrylic copolymer was dissolved in toluene and sprayed onto the surface of the particles. U-Bix3035
A practical test was performed using (manufactured by Konica Corporation). However, the developing device was modified to rotate simultaneously.

The magnetic flux density of the magnet was 800 gauss.

Comparative Example (1) A toner having an average particle size of 9 μm and a carrier having an average particle size of 120 μm were used, and only the surface sleeve of the carrier was rotated in the opposite direction.

Others were the same as in Example 1.

Comparative Example (2) A toner having an average particle size of 2 μm and a carrier having an average particle size of 19 μm were used.

The same as Example 2 except that U-Bix3035 was used without changing the developing unit.

Comparative Example (3) Same as Example 1 except that the magnetic flux density of the magnet was 500 gauss.

Comparative Example (4) Same as Example 1 except that the magnetic flux density of the magnet was 1800 gauss.

The characteristics of the above Examples and Comparative Examples were checked, and the results are shown in Table 1.

[0072]

[Table 1]

[0073]

As an image quality, an image having a high copy density, no development unevenness, and good sharpness can be obtained, and an image having a large resistance to filming of carrier on a photosensitive member and fogging occurrence in a repeated use. The forming method can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a configuration of a developing portion of an example of a developing device used in the present invention.

[Explanation of reference numerals] 1 photoconductor 2 sleeve 3 developer tank 4 developer amount regulating member V AC power supply P two-component developer D development area M magnet body B bias power supply

Claims (4)

[Claims] 1. A toner comprising at least finely divided particles of a polymerizable monomer, polymer particles containing a colorant and a release agent, and polymerized to form a carrier having a particle size of 3 to 7 μm as an irregular carrier. To the developing area by rotating the sleeve and the sleeve of the developer carrier having a magnet inside thereof in the direction opposite to the latent image carrier and the built-in magnet in the same direction. An image forming method comprising performing non-contact development. 2. The image forming method according to claim 1, wherein the carrier of the developer is coated with ferrite having a particle size of 20 to 100 μm as core particles and a charge control resin as a shell shell. 3. The image forming method according to claim 1, wherein the magnetic flux density of the magnet contained in the developer transport body is 600 to 1500 gauss. 4. The image forming method according to claim 1, wherein an alternating electric field is applied between the developer carrier and the latent image carrier.