JPH10293412A - Nonmagnetic unicomponent developer and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the nonmagnetic unicomponent developer and the image forming method capable of being reduced in the size and the space of an image forming apparatus without any retraction due to image quality by incorporating toner particles comprising a binder resin and a colorant data a charge controller, and specified fine ferrite particles and a fluidity enhancer. SOLUTION: The nonmagnetic unicomponent developer is prepared by melting and kneading the binder resin, the colorant, the charge controller, and the like, and pulverizing and classifying them to form fine toner particles, and as external additives, adding the fluidity enhancer and the fine ferrite particles represented by the formula in which each of (x) is a number of 0.01-0.3, preferably, 0.05-0.3. The Mn-Zn type ferrite particles have, preferably, octahedral forms, if not, when, for example, they are spherical forms, a grinding or polishing effect for scraping paper power derived from postal cards and the like on the photoreceptor is reduced and when they are aciculate forms, they are ready to be adsorbed into the photoreceptor and developing rollers, and both are undesirable from the points of staining the images. The developer has an average particle diameter, preferably, of 0.1-1.0 μm, especially, 0.3-0.7 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developer and an image forming method using an electrophotographic system used in printers, digital and analog copying machines, facsimile machines, and the like.

[0002]

2. Description of the Related Art In general, in an electrophotographic system, an organic photoconductive photoreceptor (usually an organic photoconductive photoreceptor having a photosensitive layer mainly composed of various photoconductive substances and a binder resin coated on a base made of metal such as aluminum or the like) is usually used. Is a photosensitive drum processed into a drum shape)
Forming an electrostatic latent electric latent image thereon by various means,
After developing the electrostatic latent image with a developer made of powder, and transferring the powder onto a substrate such as paper or film as necessary,
Fixing is performed by a method such as pressing and heating.

[0003]

In recent years, personalization,
2. Description of the Related Art In response to market demands for space saving and the like, miniaturization of electrophotographic devices such as copiers and printers tends to be promoted.
In order to reduce the size of these devices, it is desired to reduce the diameter of the photosensitive drum. As the photoconductor drum, an organic photoconductive photoconductor drum, in particular, a laminated organic photoconductor is mainly used. In general, the surface of the photoconductor drum is constantly polished vigorously by rubbing with a developer in a developing process and pressing by a cleaning member (a cleaning blade or the like) in contact with the cleaning process. The photosensitive layer is likely to be thinned with time. Since the electrical characteristics such as the surface potential of the photosensitive drum deteriorate due to the decrease in the thickness of the photosensitive layer, the resulting image has a problem that the image density is reduced. In particular, when an attempt is made to use a small-diameter photosensitive drum, the surface area of the photosensitive member is reduced, and the frequency of rubbing per surface is increased, so that the above-mentioned phenomenon of film reduction of the photosensitive member tends to be more apparent.

Therefore, in a stacked type organic photoconductive photosensitive drum, studies have been made to avoid the problem of film reduction of the photosensitive body and to improve the printing durability of the photosensitive body. For example, by adopting a polycarbonate resin as a resin constituting the surface layer of the drum photosensitive layer, the hardness and mechanical strength of the surface are increased, so that the film loss is reduced, and the printing durability tends to be improved. Therefore, as the laminated organic photoconductive photoreceptor drum, if a small-diameter drum constituted by using polycarbonate as a constituent resin on the surface is adopted,
This is effective because the above-described problem in a small-sized image forming apparatus is solved.

[0005] On the other hand, in these small personal type image forming apparatuses, other problems such as image defect, such as the dropout of characters and the occurrence of paper dust marks on the photoreceptor due to postcard passing, have become apparent. So, Japanese Patent Publication No. 63-58354
No. As described in Japanese and Japanese 62-258472 Patent Publication is done often be improved by externally added magnetic particles typified by magnetite (Fe ₃ O ₄₎ to the toner particles.

However, these magnetite particles are likely to adhere firmly to the photoreceptor drum having a polycarbonate resin as a surface layer, and appear as spot-like defects on an obtained image, thereby contaminating the image. The problem turned out to be new. As an effective countermeasure against this, at present, no very effective proposal has been found, and the image quality that is sufficiently satisfactory for practical use has not been obtained. In particular, there is no developer that satisfies image quality in combination with a photosensitive drum having a small diameter of 50 mm or less. This has been a limitation in reducing the diameter of the photoconductor and, consequently, the size of the apparatus.

Similarly, when magnetite particles are added to the toner, the developing roller is contaminated with magnetite because the magnetite particles adhere strongly to the surface of the developing roller in the non-magnetic one-component developing system. as a result,
It becomes difficult to form a uniform thin layer of developer on the developing roller,
Poor image uniformity and quality. SUMMARY OF THE INVENTION The present invention has been made in view of the above situation, and has been made in order to solve the problem. The object of the present invention is to reduce the size of the device and to reduce the problem of image quality caused by the miniaturization. No, specifically, there is no decrease in image density because the film loss of the photosensitive layer is small, and there is no occurrence of a hollow character,
There is no trace of paper dust on the photoreceptor due to postcard passing, no problem of image contamination due to adhesion of external additives to the photoreceptor, and good image uniformity in non-magnetic one-component development system Another object of the present invention is to provide a developer capable of obtaining high quality and an image forming method using the same.

[0008]

Means for Solving the Problems In order to achieve the above object, the present inventors have conducted intensive studies with the aim of developing a developer capable of obtaining good image quality even with a small-diameter photosensitive drum.
The present inventors have found a developer capable of obtaining good image quality even when using a photosensitive drum having a small diameter of not more than m, and have reached the present invention. That is, the gist of the present invention is characterized by containing at least toner particles containing a binder resin, a colorant, and a charge controlling agent, ferrite fine particles represented by the following general formula (1), and a fluidity improver. Non-magnetic one-component developer General formula (1) [(MnO) _x (FeO) _1-x ] · Fe ₂ O ₃ (where x represents a numerical value of 0.01 to 0.3), and
An image forming method for developing an electrostatic latent image formed on a photosensitive drum having a diameter of 50 mm or less with a developer, wherein the developer is the non-magnetic one-component developer described above. Be in the way.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The image forming method of the present invention is particularly useful for a small-diameter photosensitive drum. Examples of the photosensitive drum constituting the present invention include inorganic drums such as selenium, arsenic-selenium, selenium-tellurium, and amorphous silicon, and organic drums such as diazo compounds and dyes.

In order to reduce the size of the apparatus, a photoreceptor drum having a small diameter is desired. Usually, a diameter of 50 mm or less is adopted, and if a smaller diameter is desired, a size of 40 mm or less is adopted. The following sizes have also been proposed. However, as described above, with the conventional developer, the image quality deteriorates as the diameter of the photosensitive drum decreases, and although the apparatus itself achieves miniaturization, satisfactory results cannot be obtained in terms of image quality. In this regard, according to the image forming method of the present invention, a good image can be obtained with any of the small-diameter drums, and a small-sized apparatus having good performance can be realized.
In addition, if the diameter is further reduced, the difference from the conventional technology is remarkably exhibited.

Among the above-mentioned photosensitive drums, organic photosensitive drums are particularly preferred from the viewpoints of ease of manufacture, electrical and optical performance, cost, safety and the like. Among the organic photosensitive drums, a stacked organic photoconductive photosensitive drum having a charge generation layer and a charge transport layer (surface layer) is particularly preferable. Preferably, the binder resin constituting the surface layer is a polycarbonate resin.

On the other hand, the toner is a fine powder obtained by melting and kneading a binder resin, a colorant, a charge controlling agent, and other substances, pulverizing, and classifying. The developer according to the present invention has a specific structure for the toner particles. It consists of adding ferrite fine particles and a fluidity improver. Among the toner components,
As the binder resin, various known resins suitable for the toner can be used. For example, polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer Copolymer, styrene-maleic acid copolymer, styrene-acrylate copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-acrylic acid Octyl copolymer, styrene-phenyl acrylate copolymer, etc.), styrene-methacrylate copolymer (styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer) Coalescing,
Styrene-octyl methacrylate copolymer and styrene-phenyl methacrylate copolymer), styrene-α-
Styrene resins (homopolymers or copolymers containing styrene or styrene substituents) such as methyl chloroacrylate copolymer and styrene-acrylonitrile-acrylate copolymer, vinyl chloride resin, rosin-modified maleic acid resin, Phenolic resin, epoxy resin, saturated polyester resin, unsaturated polyester resin, low molecular weight polyethylene, low molecular weight polypropylene, ionomer resin, polyurethane resin, silicone resin, ketone resin,
Ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, xylene resin and polyvinyl butyral resin and the like, but particularly preferred resins to be used in the present invention, styrene resins, saturated or unsaturated polyester resins and Epoxy resins can be mentioned. Further, the above resins are not limited to being used alone, and two or more kinds can be used in combination. Furthermore, Japanese Patent Publication No. 50-23
No. 354, Japanese Unexamined Patent Publication No. 50-44836, etc.
Non-crosslinked binder resins described in JP-A-95-95 and JP-B-63-32180 can also be used.

The softening point of the toner binder resin is preferably 100 to 160 ° C. as measured by a flow tester method. If the softening point is less than 100 ° C., stains during fixing (so-called “hot offset” phenomenon) are likely to occur, and if it exceeds 160 ° C., the fixing strength tends to deteriorate. Further, the glass transition temperature of the binder resin is preferably such that the transition temperature (inflection point) measured by a differential thermal analyzer is 50 ° C. or more. When the glass transition temperature is lower than 50 ° C., thermal stability during long-term storage is poor, causing aggregation and solidification of the toner, which is problematic in use.

The colorant is not particularly limited as long as it is conventionally used, and any suitable pigment or dye can be used. For example, titanium oxide, zinc white, alumina white, calcium carbonate, navy blue, iron black, carbon black, phthalocyanine blue, phthalocyanine green, Hansa yellow G, rhodamine dye, chrome yellow, quinacridone, benzidine yellow, rose bengal, triallyl Methane dyes, anthraquinone dyes, monoazo and disazo dyes and the like are used alone or in an appropriate mixture according to the color of the corresponding developer. The content of the colorant may be an amount sufficient to color the developer so that a visible image can be formed by development, and is, for example, 3 to 20 parts by weight based on 100 parts by weight of the binder resin. Is preferred.

Regarding the charge polarity of the developer, a method of controlling the charge depending on the composition of the binder resin to be used may be considered.
Usually, various known charge control agents are added as a component of the developer. Examples of the charge control agent for obtaining a positively chargeable toner include various nigrosine compounds, and quaternary grades described in JP-B-1-54694, JP-B1-54695, and JP-B1-54696. Ammonium salt compounds, triphenylmethane compounds described in JP-A-51-455, JP-B-63-57787, JP-B-2-501506, etc .; JP-A-3-119364; Examples thereof include imidazole derivatives and metal complexes of imidazoles described in JP-A-202856 and JP-A-3-2177851. Among these, a positively chargeable toner containing at least one selected from a nigrosine compound, a quaternary ammonium salt compound and a triphenylmethane compound is preferable. As a method of incorporating the charge control agent into the toner, there are a method of adding the charge control agent inside the toner and a method of externally adding the same. When internally added, the amount of these compounds used is
Usually, 0.05 parts with respect to 100 parts by weight of the binder resin.
It is used in the range of from 20 to 20 parts by weight, preferably from 0.1 to 10 parts by weight. When externally added, the amount is preferably 0.01 to 10 parts by weight based on 100 parts by weight of the resin. Within the above addition range, the internal addition and the external addition of the charge control agent may be performed in combination.

In addition, as an auxiliary agent which can be internally added to the toner for the purpose of improving thermal characteristics and physical characteristics, known ones can be used. For example, polyalkylene wax, paraffin wax, higher fatty acid, Fatty acid amide, metal soap and the like. The amount of the binder resin is 100
0.1 to 10 parts by weight based on parts by weight is preferred. As a method for producing the toner, the above components may be mixed, kneaded with a kneader or the like, cooled, pulverized, and classified.

The developer according to the present invention contains ferrite fine particles represented by the following general formula (1) and a fluidity improver independently of toner particles (as a so-called ordinary external additive). And

General formula (1) [(MnO) _x (FeO) _1-x ] · Fe ₂ O ₃ (where x represents a numerical value of 0.01 to 0.3) x is preferably 0.05 ０．３0.3.

The shape of the Mn ferrite represented by the general formula (1) is preferably octahedral. In such a case, the particles may be subjected to a de-squaring process by a known method as long as the shape of the octahedron is not impaired. When the particle diameter is not octahedral, for example, in the case of a spherical shape, the polishing effect of scraping paper dust marks on the photoreceptor by postcard passing is small, and in the case of a needle shape, it is easily attracted to the photoreceptor and the developing roller There is a problem,
Either case is not preferable because image contamination occurs.

The average particle size is 0.1 to 1.0 μm.
m is preferable, and especially 0.3 to 0.7 is more preferable.
When the particle diameter is smaller than the above range, the particles are easily adsorbed on the photoconductor, and when the particle diameter is larger, streak-like scratches are generated on the photoconductor. The average particle diameter was measured as a cumulative 50% diameter by measuring the particle size distribution of 300 or more particles by observation with a scanning electron microscope.

Further, the ferrite fine particles according to the present invention have a saturation magnetization of 85 at a measurement magnetic field of 2 k Oe.
It is preferably at most emu / g. When the saturation magnetization is larger than the above range, aggregation of fine particles due to magnetic attraction tends to occur in the developer in continuous actual shooting or the like. It is not preferable because it strongly adheres to the developing roller in the magnetic one-component developing method and causes fatal image contamination. In general, the ferrite fine particles according to the present invention have a lower value of saturation magnetization than magnetite (Fe ₃ O ₄ ) fine particles having the same shape and the same particle diameter, so that the aggregation of the particles is hardly caused essentially. Therefore, adsorption to the developing roller in the photosensitive member surface and the non-magnetic one-component developing system is relatively alleviated, and image contamination tends to be suppressed. Note that commercially available BH
A tracer was used.

In the present invention, it is essential to add a fluidity improver in combination. When the fluidity of the toner particles is insufficient, the aggregation of the toner particles becomes intense. As a result, the aggregation of the magnetic fine particles is likely to occur, and the adsorption of these aggregates to the photoreceptor is deteriorated. This phenomenon causes fatal image contamination particularly in a small-diameter drum having a high frequency of surface rubbing.

As the fluidity improver, any known fluidity improver may be used. In particular, silicon oxide, titanium oxide,
Fine particles of metal oxide such as aluminum oxide are preferred. These metal oxides have an average primary particle diameter of 5-1.
The thickness is preferably 00 nm, and is preferably subjected to a hydrophobizing treatment with various hydrophobizing agents. In particular, silicon oxide fine particles which have been subjected to a hydrophobic treatment with dimethyldichlorosilane, hexamethyldisilazane, a silicone compound or the like are more preferable.

The amount of the additive fine particles used is 0.1 to 5 parts by weight of the ferrite fine particles represented by the general formula (1) and 0.01 to 5 parts by weight of the fluidity improver per 100 parts by weight of the toner particles. It is preferred to contain 2.0 parts by weight. The average particle diameter of the toner is preferably 5 to 20 μm. Is also applicable.

[0025]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the scope of the invention. In the following Examples and Comparative Examples, “parts” simply means “parts by weight”.

Example 1 Styrene resin 100 parts (Monomer weight ratio: styrene / n-butyl acrylate = 82/18) Nigrosine dye charge control agent 1 part (Bontron N-04, manufactured by Orient Chemical Company) Carbon black 7 parts ( Mitsubishi Carbon Black MA100S, manufactured by Mitsubishi Chemical Corporation) Polypropylene 4 parts (NP505, manufactured by Mitsui Petrochemical Industries, Ltd.)

The above components are mixed, kneaded, pulverized and classified.
As a result, a positively chargeable black toner having an average of 11 μm was obtained. this
[(MnO)_0.1(FeO)
_0.9] ・ Fe_TwoO _ThreeFerrite fine particles represented by
Body shape, average particle size about 0.5 μm, saturation magnetization 81 emu
/ G) and hydrophobized silicon dioxide (trade name A)
Erosil R972, manufactured by Nippon Aerosil Co., Ltd., average primary particles
0.3 part with a Henschel mixer
Processed.

Next, using this developer, a photosensitive drum having a surface layer resin of polycarbonate resin having a diameter of 3
A real-world test was performed with a commercially available copying machine evaluation apparatus using a 0 mm laminated organic photoconductor. The toner for replenishment used in the actual test was of the same composition as the toner used for the developer. The actual shooting environment is 25 ° C and 50% RH
I went in. In addition, as the actual copying method, first, 200 sheets of government-made postcards were continuously copied to confirm the transferability, and then, 9800 sheets of continuous copying were performed on ordinary copy paper to confirm the durability (total developer). 10,000).

As a result, it was possible to obtain a good image quality without missing or unevenness in the image. Also, no trace of paper dust was generated due to the postcard passing on the photoreceptor. Also,
The image density after 10,000 copies was also sufficiently high, almost comparable to the initial state. In addition, it was found that there was no problem with other image quality, and the image had good durability. further,
No image contamination was caused by the adhesion of the toner additive. It should be noted that the situation of the film thickness reduction of the photosensitive drum after the actual copying of 10,000 sheets was extremely slight, and it was found that there was no practical problem.

Comparative Example 1 The procedure of Example 1 was repeated except that the ferrite particles used in Example 1 were replaced with magnetite particles (the shape and average particle diameter were the same as the ferrite powder of Example 1 and the saturation magnetization was 91 emu / g). A developer was prepared in exactly the same manner as in No. 1 and the actual image was evaluated. As a result, no omission in the image and no occurrence of paper dust were observed in postcard passing, but 3000 real continuous images were taken.
After 4,000 sheets, spot-like image defects began to appear on the image, and the tendency of the defects to increase with the number of actual shots was recognized, indicating a problem in practice. At this time, adhesion of the magnetite fine particles was observed on the photoreceptor.

Comparative Example 2 A developer was prepared in exactly the same manner as in Example 1 except that the hydrophobized silicon dioxide fine particles used in Example 1 were not added, and an actual printing evaluation was performed. As a result, image contamination and deterioration in image quality due to the adhesion of the magnetic powder to the photosensitive member and the developing roller began to occur on about 5,000 sheets.

Example 2 In Example 1, a modified machine of a commercial copying machine using a laminated organic photoconductor having a diameter of 24 mm, in which the resin of the surface layer of the photosensitive drum was a polycarbonate resin, was used as an apparatus for evaluating a real image. The evaluation was performed in exactly the same manner as in Example 1, except for using it. As a result, there was no omission or unevenness in the image, and no generation of paper dust trace due to postcard passing on the photoreceptor was observed. Further, it was found that the image density after 10000 sheets was sufficiently high and the image had good durability. Further, image contamination due to the adhesion of the toner additive to the photosensitive drum and the developing roller,
No deterioration in image quality occurred.

Example 3 In the toner composition of Example 1, a nigrosine dye charge control agent was replaced with a quaternary ammonium salt compound (trade name: Bontron P)
51, Orient Chemical Co., Ltd.), and a toner was prepared in the same manner as in Example 1 and evaluated for actual printing. As a result, in each of the copying machines, there was no omission or unevenness in the image, and no generation of paper dust marks due to postcard passing on the photoreceptor was observed. Further, it was found that the image density after 10000 sheets was sufficiently high and the image had good durability. Further, no image contamination or deterioration in image quality due to the adhesion of the toner additive to the photosensitive drum and the developing roller occurred.

Example 4 In the toner composition of Example 1, a nigrosine dye charge controlling agent was replaced with a triphenylmethane compound (COPY BLU).
E, manufactured by Hoechst Co., Ltd.), and a toner was prepared in the same manner as in Example 1 and evaluated for actual printing.
As a result, in each of the copying machines, there was no omission or unevenness in the image, and no generation of paper dust marks due to postcard passing on the photoreceptor was observed. Further, it was found that the image density after 10000 sheets was sufficiently high and the image had good durability. Further, no image contamination or deterioration in image quality due to the adhesion of the toner additive to the photosensitive drum and the developing roller occurred.

[0035]

According to the present invention, it is possible to reduce the size and space of the apparatus without any restrictions due to the image quality. In particular, the problem that tends to occur when the diameter of the photosensitive drum is reduced can be easily improved. Specifically, the photosensitive drum has the following effects, and therefore has a great industrial value. 1. 1. No decrease in image density 2. No missing image 3. There is no trace of paper dust due to postcard passing. 4. No image contamination due to adhesion of external additives to photoconductor No image non-uniformity and quality deterioration due to external additives adhering to the developing roller

──────────────────────────────────────────────────続 き Continued on front page (51) Int.Cl. ⁶ Identification code FI G03G 9/08 371 374

Claims (7)

[Claims] 1. A non-magnetic toner comprising: toner particles containing at least a binder resin, a colorant, and a charge controlling agent; ferrite fine particles represented by the following general formula (1); and a fluidity improver. Component developer. General formula (1) [(MnO) _x (FeO) _1-x ] · Fe ₂ O ₃ (where x represents a numerical value of 0.01 to 0.3) 2. The non-magnetic one-component developer according to claim 1, wherein the ferrite fine particles have an octahedral particle shape. 3. The ferrite fine particles have an average particle diameter of 0.1.
The non-magnetic one-component developer according to claim 1 or 2, wherein the non-magnetic one-component developer has a thickness of from 1.0 to 1.0 µm. 4. The non-magnetic one-component developer according to claim 1, wherein the ferrite fine particles have a saturation magnetization of 85 emu / g or less at a measurement magnetic field of 2 kOe. 5. The method according to claim 1, wherein the charge control agent comprises at least one selected from quaternary ammonium salt compounds, nigrosine compounds and triphenylmethane compounds. Non-magnetic one-component developer. 6. An image forming method for developing an electrostatic latent image formed on a photosensitive drum having a diameter of not more than 50 mm with a developer, wherein the developer is according to any one of claims 1 to 5. An image forming method comprising a non-magnetic one-component developer. 7. The image forming method according to claim 6, wherein the diameter of the photosensitive drum is 40 mm or less.