JP3114020B2 - Color developer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic semiconductor (OPC).
An image carrier is used to form an image, and the image is transferred to a transfer material using a photoconductor (hereinafter referred to as an “OPC photoconductor”) composed of The present invention relates to a color developer used in an image forming method of forming an image by repeatedly using an image carrier after cleaning with a blade cleaning unit.

[0002]

2. Description of the Related Art In recent years, a large number of electrophotographic color image forming apparatuses such as color copying machines or printers using an OPC photosensitive member as an image carrier have been manufactured. Usually, such an image forming apparatus forms a latent image on an OPC photoreceptor by a normal electrophotographic process, develops the latent image with a developing device to form a toner image, and transfers the image to a transfer material. Transfer and a visible image is obtained. On the other hand, the residual toner on the image carrier is cleaned by a cleaning unit, and the image carrier is used repeatedly.

In particular, blade cleaning means having a structure in which a cleaning blade made of a rubber elastic material is pressed against an image carrier in a counter direction is widely used because it is very advantageous in terms of miniaturization and cost.

Generally, an OPC photoreceptor has a charge generation layer comprising a binder in which a charge generation material is dispersed on a conductive support,
The charge transporting layer is formed by laminating a charge transporting layer composed of a binder in which a charge transporting material is dispersed, and a phthalocyanine pigment, an anthrone pigment, an azo pigment, a pigment such as an indigo pigment, a dye such as a bilylium dye, Or a dye such as a cyanine dye, and a charge transporting material such as carbazoles such as pyrene and isopropylcarbazole, hydrazones, pyrazolines, oxasonyl compounds, thiazole compounds, triarylmethane compounds, and polyarylalkanes. Are used, and as the binder, polyarylate resin, polysulfone resin,
Polyamide resin, acrylic resin, acrylonitrile resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, phenol resin, epoxy resin, polyester resin, alkyd resin, polycarbonate, polyurethane, or a resin containing two or more of these resin repeating units Polymer resins such as styrene-butadiene copolymers, styrene-acrylonitrile copolymers, styrene-maleic acid copolymers and the like have been used.

As a result of many studies and experiments, the present inventors have found that when an OPC photosensitive member is used as an image bearing member, as shown in FIG. Was found to rise.

According to the results of research conducted by the present inventors, the cause of the increase in the coefficient of friction with the rise in the temperature of the image carrier is due to the temperature characteristics of the binder occupying most of the surface of the OPC photosensitive member. Turned out to be something.

For the purpose of lowering the coefficient of friction, for example,
Japanese Patent Application Laid-Open No. 3-31356 and the like have proposed means for providing a resin in which fluorine-based resin particles are dispersed in a photoreceptor surface layer. The above-described means certainly lowers the coefficient of friction, improves cleaning properties, is effective in abrasion and scratch resistance, but controls surface roughness by the degree of dispersion,
It was not always satisfactory, for example, when the printout was continued.

Further, when an image is formed by combining a plurality of developers having different surface properties, such as a magnetic toner and a non-magnetic toner, there is a difference in the slipping property or the shaving property of each toner with respect to a photoreceptor. At present, it is difficult to always keep the pressure contact state between the photosensitive member and the cleaning blade stably.

As a result of many research experiments, the present inventors have found that the photoconductor and the cleaning blade press-fit portion are 0.2 to 0.2 irrespective of the surface properties of the toner and the surface properties (surface roughness) of the photoconductor.
It was found that a good image and stable cleaning characteristics were obtained when a minute gap of 2.5 μm was present.

As a means for generating the above-mentioned gap between the photosensitive member and the cleaning blade pressing part, the surface roughness of the photosensitive member may be controlled. However, if the surface roughness of the photosensitive member is larger than 2.0 μm, the image quality is deteriorated. In particular, problems such as a reduction in highlight reproduction, roughness, and the like occur, and when the surface roughness is small, it becomes difficult to control the roughness.
In addition, depending on the degree of surface shaving, particularly when the above-mentioned gap is smaller than 0.2 μm, the pressure of the cleaning blade is too strong, and cleaning failure due to turning over of the blade occurs, and the surface roughness of the photoconductor is reduced. Sufficient cleaning characteristics have not always been achieved by the control means alone.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide a color developer which has solved the above-mentioned problems.

That is, an object of the present invention is to provide a color developer which is hardly influenced by the environment such as temperature and humidity and has always stable cleaning characteristics.

A further object of the present invention is to provide a color developer which has high definition image characteristics excellent in highlight reproduction, fine line reproduction and the like, and has excellent durability stability.

[0014]

SUMMARY OF THE INVENTION According to the present invention, a latent image holding member comprising an organic photoreceptor containing 5 to 40% by weight of a fluororesin powder on the surface is used to develop a developed image with a developer. Forming the developed image on a transfer material, cleaning the residual developer on the latent image holding member with a counter blade cleaning unit, and repeatedly using the latent image holding member to form a color image. A color developer used in the method, wherein the developer contains at least colorant-containing resin particles and an external additive, and the external additive comprises at least i) an oxidizing agent having a particle diameter of 10 to 50 μm as a flow improver. A color developer containing 0.05 to 3% by weight of titanium or alumina; ii) 0.1 to 3% by weight of spherical fine particles having a weight average particle diameter of 0.2 to 2.5 μm. About.

That is, the present inventors have eagerly studied the cleaning performance and image characteristics of a color image forming method using an organic photoreceptor containing 5 to 40% by weight of a fluororesin powder on the surface as a latent image holding member. As a result of examination, it was found that at least the weight average particle size of 0.2 to 2.5 μm
It has been found that a toner containing spherical fine particles of m is extremely excellent in cleaning and image quality improvement in various environments and provides a good image.

The reason why the cleaning property is stable is as follows.
This is because excessive pressure contact between the surface of the organic photoreceptor and the cleaning blade is mitigated by the above-mentioned spherical fine particles serving as spacers, and appropriate friction characteristics can be obtained.

The spherical fine particles usable in the present invention include:
It is a true spherical shape or a shape without a sharp corner,
Any material having a weight average diameter of 0.2 to 2.5 μm may be used. Further, the starting materials, the production method, and the like are not limited at all.

If the spherical fine particles are smaller than 0.2 μm, the cleaning blade cannot follow the surface of the photoreceptor when the surface roughness of the photoreceptor is rough, so that the cleaning blade often slips through the cleaning blade, causing uneven charging when forming a latent image. Image degradation is likely to occur. On the other hand, if it is larger than 2.5μ, it is sufficiently cleaned by the cleaning blade,
It becomes difficult to collect at the blade edge, the spacer function is reduced, and the efficiency is reduced.

The spherical fine particles usable in the present invention include:
Inorganic oxides such as silicic acid fine powder, alumina fine powder, titanium oxide fine powder, zirconium oxide fine powder, magnesium oxide fine powder, and nitrides such as boron nitride fine powder, aluminum nitride fine powder, and carbon nitride fine powder. and so on.
In addition, inorganic resin particles such as silicone resin particles and the like can be mentioned.

Particularly suitable for the present invention are those in which 1
Silicone resin particles having a siloxane structure having two alkyl groups are preferred because they can sharpen the particle size distribution.
Further, as for the particle size distribution, it is desirable that 80% or more of the volume distribution is within ± 30% of the average particle size. Moreover, you may perform a surface treatment as needed. The addition amount is 0.05-3% by weight, preferably 0.1-2.
0% by weight is good.

The particle size distribution of the spherical fine particles of the present invention was measured with a particle analyzer CAPA500.

In the present invention, it is necessary to include a flow improver as an external additive in addition to the spherical fine particles. Alumina or titanium oxide is used as such a flow improver. Among them, titanium oxide having stable charging characteristics and high fluidity-imparting ability is suitable for the present invention.

Titanium oxide is charged to the same polarity as the toner when it rubs against iron powder, and the absolute value of the charge is 30 μC / g
The charging characteristics are hardly affected even when the temperature and humidity change.

When titanium oxide having such characteristics is externally added to the toner, the amount of charge of the color toner, which tends to be excessive under low humidity, is suppressed, and the amount of charge such as under high humidity or in the initial stage of toner rubbing is reduced. Even in a situation where shortage is likely to occur, the charging is hardly hindered, the rise is quick as a whole, and good charging characteristics with little fluctuation can be obtained.

In order to exhibit the above-mentioned effects, the particle size must be 1
0.1 to 3% by weight, preferably 0.2 to 2% by weight of the titanium oxide fine particles in the range of 0 to 50 mμ with respect to the toner.
It is good to add. If the particle size is larger than 50 μm or if it is added in excess of 3% by weight, the dispersion will be insufficient or the toner will be released from the toner, which not only impairs the effect but also causes adverse effects. Further, when the particle size is 10
When the amount is less than mμ or the amount added is less than 0.1% by weight, the charge control and the fluidity become insufficient due to a shortage of the absolute amount or embedding in the toner.

Further, for the purpose of adjusting the charging characteristics and making the particles hydrophobic, a surface treatment can be performed within a range that does not impair the characteristics of titanium oxide. 10% hydrophobicity for hydrophobic treatment
A good range is up to 70%. If it is less than 10%, the effect of the hydrophobic treatment cannot be obtained. If it is 70% or more, the charging characteristics deteriorate and the fluidity decreases.

The raw material and production method of titanium oxide that can be used in the present invention are not particularly limited, and any one may be used as long as it satisfies the characteristics described above. As a method that can be easily obtained, a method produced by a gas phase thermal decomposition reaction of a volatile titanium alkoxide is preferable. However, it is not limited to this.

Conventionally, titanium oxide is added to the toner as described in JP-A-48-47345, and as a polishing agent in JP-A-52-19535 and JP-A-56-19535.
In JP-128956, a metal oxide such as titanium oxide is used as a fluidizing agent. JP-A-58-185405
In Japanese Patent Application Laid-Open No. 58-216252, positive chargeability is imparted to a toner by using surface-treated fine titanium oxide particles. Further, Japanese Patent Application Laid-Open Nos. 58-1157 and 60
In JP-B-136755 and the like, when the hydrophobically treated silica is used as an external additive in a combined system with the hydrophobically treated silica, the silica is used for the purpose of suppressing the charge amount of the silica which is likely to become excessive. On the other hand, in the present invention, the charge characteristics of the color toner particles themselves are controlled to reduce the difference in charge amount due to temperature and humidity, and the toner is used as a material that imparts sufficient fluidity. Are different.

If necessary, a fatty acid metal salt as a lubricant, for example, zinc stearate, aluminum stearate or the like, or a fine powder of a fluorine-containing polymer, for example, polytetrafluoroethylene polyvinylidene fluoride or the like, and tetrafluoroethylene-vinylidene fluoride A fine powder of a ride copolymer or a conductivity imparting agent such as tin oxide or zinc oxide may be added.

As the binder used in the colorant-containing resin particles of the present invention, various material resins conventionally known as electrophotographic toner binder resins are used. For example, styrene-based copolymers such as polystyrene, styrene-butadiene copolymer and styrene-acrylic copolymer, and ethylene-based copolymers such as polyethylene, ethylene-vinyl acetate copolymer and ethylene-vinyl alcohol copolymer Phenolic resin, epoxy resin, acrylic phthalate resin, polyamide resin, polyester resin, maleic acid resin and the like. In addition, the production method of any resin is not particularly limited.

When the polyester resin is used among these resins, the effect of the present invention is remarkable. That is, the polyester resin has excellent fixability and is suitable for a color toner.

In particular,

[0033]

Embedded image (Wherein R is an ethylene or propylene group, x, y
Is an integer of 1 or more, respectively, and the average value of x + y is 2 to 10. A) a carboxylic acid component comprising a divalent or higher carboxylic acid or an acid anhydride thereof or a lower alkyl ester thereof (for example, fumaric acid, maleic acid, maleic anhydride, phthalic acid) Acid, terephthalic acid, trimellitic acid, pyromellitic acid, etc.) are more preferred because they have sharp melting properties.

As the coloring agent, known dyes and pigments, for example, phthalocyanine blue, induslen blue, peacock blue, permanent red, lake red, rhodamine lake, Hanza yellow, permanent yellow, benzidine yellow and the like can be used widely. The content thereof is 12 parts by weight or less, preferably 0.5 to 9 parts by weight with respect to 100 parts by weight of the binder resin so as to reflect the light transmittance of the OHP film sensitively.

The toner according to the present invention may contain a charge control agent in order to stabilize the charge characteristics. At that time, a colorless or light-colored charge control agent that does not affect the color tone of the toner is preferable. In the present invention, when a negatively charged developer is used, the present invention becomes more effective. In this case, as the negatively charge controlling agent, for example, a metal complex of an alkyl-substituted salicylic acid (for example, a chromium complex of di-tert-butylsalicylic acid or Organometallic complexes such as zinc complex).
When the negative charge control agent is blended in the toner, the binder resin 10
0.1 to 10 parts by weight, preferably 0.1 to 10 parts by weight, based on 0 parts by weight.
It is preferable to add 5 to 8 parts by weight.

When the toner of the present invention is used as a two-component developer, the magnetic particles used in the present invention include, for example, surface-oxidized or unoxidized iron, nickel, copper, zinc, and the like.
Metals such as cobalt, manganese, chromium, rare earths, and alloys or oxides thereof, and ferrites can be used. In addition, there is no particular limitation on the manufacturing method.

In the present invention, the surface of the magnetic particles is coated with a resin or the like. The method includes dissolving or suspending a coating material such as a resin in a solvent, applying the coating material, and attaching the coating material to the magnetic particles. Any conventionally known method, such as a method of simply mixing with a powder, can be applied. In order to stabilize the coating layer, it is preferable that the coating material be dissolved in a solvent.

The material for coating the surface of the magnetic particles varies depending on the toner material. For example, an aminoacrylate resin, an acrylic resin, or a copolymer of such a resin with a styrene resin is preferable. As the negatively charged resin, silicone resin, polyester resin,
Polytetrafluoroethylene, monochlorotrifluoroethylene polymer, polyvinylidene fluoride and the like are located on the negative side in the charging series and are suitable, but are not necessarily limited thereto. Most suitable for the present invention are acrylic resins or copolymers of these resins and styrene resins.

The most suitable material for the magnetic particles used in the present invention has a composition of 98% or more of Cu—Zn—Fe (composition ratio (5-20) :( 5-20) :( 30-80)). Ferrite particles which are easy to smoothen the surface, have a stable charge-imparting ability, and can stably coat.

The coating amount of the above compound may be appropriately determined so that the charge imparting property of the magnetic particles satisfies the above-mentioned conditions, but generally the total amount of the compound is 0.1 to 3 with respect to the magnetic particles of the present invention.
0% by weight (preferably 0.3 to 20% by weight).

The weight average particle size of these magnetic particles is 35 to 6
It preferably has a size of 5 μm, preferably 40-60 μm. Further, the weight distribution is 2 to 6% when the weight distribution is 26 μm or less, and 5% to 25% when the weight distribution is between 35 μm and 43 μm.
%, And when 74 μm or more is 2% or less, a good image can be maintained.

In the present invention, when the mixing ratio of the above-mentioned magnetic particles and toner particles is 2 to 9% by weight, preferably 3 to 8% by weight as the toner concentration in the developer, usually good results are obtained. can get. If the toner density is less than 2.0%, the image density is low and cannot be used practically. If the toner density is more than 9%, fog and scattering inside the machine are increased, and the useful life of the developer is shortened.

In order to prepare the colorant-containing resin particles according to the present invention, a thermoplastic resin may be sufficiently mixed with a pigment or dye as a colorant, a charge control agent, and other additives, if necessary, using a mixer such as a ball mill. After mixing, heat roll, kneader, melt using a hot kneader such as extruder,
The pigments or dyes are dispersed or dissolved in the resin mixed with each other by kneading and kneading, and after cooling and solidification, pulverization and strict classification are performed to obtain the colorant-containing resin particles according to the present invention. I can do it.

[0044]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples. "Parts" means parts by weight.

Example 1 Polyester resin obtained by condensation of propoxylated bisphenol and fumaric acid 100 parts Phthalocyanine pigment 4 parts Di-tert-butylsalicylic acid chromium complex 2 parts 2 were sufficiently premixed with a Henschel mixer, and biaxially mixed. The mixture was melt-kneaded with a type extruder, cooled, coarsely pulverized to about 1 to 2 mm using a hammer mill, and then finely pulverized by an air jet type pulverizer. Further, the obtained finely pulverized product was classified by a multi-segment classification device, and 2 to 10 μm was selected so as to have the particle size distribution of the present invention, thereby obtaining colorant-containing resin particles.

0.5 parts of titanium oxide fine powder (BET 125 m ^{2 /} g) having a particle diameter of 20 μm and 0.5 parts of spherical silicone resin particles having an average particle diameter of 0.8 μm having a methyl group are added to the colorant-containing resin particles. To obtain a cyan toner.
A developer was prepared with the toner, Cu-Zn-Fe-based ferrite particles surface-coated with a styrene-methyl methacrylate copolymer, and a toner concentration of 5%.

Using this developer, a photosensitive member of a commercially available color copying machine (CLC500, manufactured by Canon Inc.) contains 10 parts of polytetrafluoroethylene powder (Rublon L-2, manufactured by Daikin Industries, Ltd.). The image was formed by changing the organic photoreceptor (surface roughness: about 1.6 μm) having polycarbonate on the surface layer. The development conditions were: development contrast 350 V at 20 ° C./10%, development contrast 3 at 23 ° C./65%.
20V, development contrast 270V under 30 ° C / 80%
In each case, 10,000 sheets were printed.

As a result, no cleaning failure occurred, the image density was extremely stable at 1.46 to 1.55, and a very clear image without roughness was obtained.

Examples 2 to 5 and Comparative Examples 1 to 4 Tables 1 and 2 show Examples and Comparative Examples in which the spherical fine particles and the flow improver in Example 1 were variously changed.

Embodiment 6 In Embodiment 1, the developing device was modified so as to have the structure shown in FIG. 2, and non-magnetic one-component development was performed by using the toner of Embodiment 1.
Tables 1 and 2 also show the results of 000 images.

At this time, a sleeve (coat layer thickness: 10 μm) coated with a phenol resin in which 40 parts of crystalline graphite was dispersed was used for the surface of the developer carrier 2, and 4 was a urethane sponge roller and a developer application blade. 5 is in contact with the developer carrier at a linear pressure of 50 g / mm.

The developing conditions were such that the gap between the developer carrier and the latent image holder was 300 μm, and a developing bias in which an alternating electric field of 20 KHz and 1.8 KVpp was superimposed was applied.

[0053]

[Table 1]

[0054]

[Table 2]

[0055]

According to the present invention, as a color toner used in an image forming apparatus having a specific latent image holding member, various spherical fine particles and a specific flow improver are contained as external additives, so that various kinds of toners can be used. It is possible to provide an image forming method which is excellent in cleaning properties in an environment and can obtain high-quality image characteristics which are not affected by temperature and humidity.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a surface temperature of a latent image holding member and a friction coefficient of the surface.

FIG. 2 illustrates a partial configuration example of an image forming apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image holder 2 Developer carrier 3 Developer 4 Roller 5 Developer coating blade 6 Power supply

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A 1-234859 (JP, A) JP-A 63-311356 (JP, A) JP-A 64-76057 (JP, A) JP-A 62 52564 (JP, A) JP-A-64-49052 (JP, A) JP-A-1-100563 (JP, A) JP-A-3-48862 (JP, A) JP-A-2-55367 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 9/08

Claims (5)

(57) [Claims] 1. A latent image holding member comprising an organic photoreceptor containing 5 to 40% by weight of a fluororesin powder on a surface thereof,
A developed image is formed with a developer, and the developed image is transferred to a transfer material. On the other hand, the residual developed image on the latent image holding member is cleaned by a counter blade cleaning means, and the latent image holding member is repeatedly used. In a color developer used in an image forming method for forming a color image, the developer contains at least a colorant-containing resin particle and an external additive, and the external additive comprises at least a flow improver and a weight average particle. Diameter 0.2-2.
A color developer containing 5 μm spherical fine particles. 2. The color developer according to claim 1, wherein the spherical fine particles are a silicon-containing compound represented by fine silica powder and silicone resin particles. 3. The color developer according to claim 1, wherein the spherical fine particles are silicone resin particles having a siloxane structure having one alkyl group at a silicon atom. 4. The color developer according to claim 1, wherein the flow improver is titanium oxide or alumina. 5. The method according to claim 1, wherein the flow improver has a particle size of 10 to 200 μm.
Absolute value of charge amount when rubbed with iron powder at 30 μc / g
The color developer according to claim 1, which is the following titanium oxide.