JP3098595B2 - Non-magnetic one-component development method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-magnetic one-component developing method used for an electrophotographic copying machine, an electrophotographic printer and the like. US Pat. No. 2,297,691 describes electrophotography.
In general, a method described in Japanese Patent Application Laid-Open No. H10-26095 is known, which uses a photoconductive insulator (photosensitive drum or the like) and applies a uniform electrostatic charge on the photoconductive insulator by corona discharge or the like. To form an electrostatic latent image by irradiating a photo image on the photoconductive insulator by various means, and then visualize the latent image with a fine powder called toner, and, if necessary, paper. After the transfer of the toner image, the toner image is melted by pressurizing, heating, solvent vapor, light, or the like and fixed on paper or the like to obtain a printed matter. As a toner for developing these electrostatic latent images, a dispersion of a coloring agent such as a dye and carbon black in a binder resin composed of a natural or synthetic polymer substance is conventionally pulverized to about 1 to 30 μm. Particles were used.

Such a toner is usually used alone or mixed with a carrier substance (carrier) such as iron powder or glass beads and used for developing an electrostatic latent image. When the toner alone is used for development (non-magnetic one-component developing method), the toner is frictionally charged with the layer thickness regulating blade and each member in the developing device, and then transported by the developing roller, and is transferred onto the photoconductive insulator. A visible image is formed by contacting the latent image portion of the image.

[0003]

However, in such a conventional non-magnetic one-component developing method, the amount of toner adhered to a developer carrier is regulated by using a layer thickness regulating device. As the toner, a colorant or the like is dispersed in a resin such as styrene-acryl or the like, and a pulverized toner is used. The toner produced by the pulverization method has an irregular shape, and the shape of the toner has many sharp corners.

In the non-magnetic one-component developing method, the toner is charged instantly by strong friction with a layer thickness regulating blade, so that the pressure applied to the toner becomes extremely large. Due to this stress, the toner is crushed from an acute angle portion, and the generated fine powder easily slips through the layer thickness regulating blade, lowering the triboelectric charging efficiency, and lowering the toner charge amount, thereby lowering the print density and increasing the amount of uncharged toner. This causes a large problem that fog increases and print quality deteriorates.

SUMMARY OF THE INVENTION The present invention has been made in view of such conventional problems, and eliminates an acute angle portion of a toner shape, thereby preventing a decrease in charge amount and a decrease in print density, thereby prolonging a long time. It is an object of the present invention to provide a non-magnetic one-component developing method which has high print quality even when continuous printing is performed and does not cause an image change.

[0006]

In the non-magnetic one-component developing method, (1) the toner is not crushed due to the stress of the layer thickness regulating blade, and (2) the cleaning is surely performed without rubbing the blade with the cleaning blade. What is necessary is the above-mentioned characteristics.

As a method satisfying the above characteristics, (1) in order to prevent toner crushing due to stress of the layer thickness regulating blade, there is no acute angle portion in the toner shape;
To prevent the cleaning blade from slipping,
It is possible that the toner has an appropriate degree of deformation. In order to satisfy these characteristics, the inventors of the present invention, in the non-magnetic one-component developing method, (1) agglomerate the fine particles obtained by the emulsion polymerization method, fuse the interface of the fine particles, and form one toner. (2) The time for fusing the interface of the fine particles (hereinafter referred to as aging) is controlled, and the toner shape is in the range of Wader's degree of sphericity of 0.90 to 0.85. To As described above, the sharpness of the toner shape is eliminated, and the appropriate irregularity is imparted, so that the toner is not crushed by the stress of the layer thickness regulating blade. The present invention has led to the invention of a non-magnetic one-component developing method which does not cause any problem.

The Wardel's degree of sphericity described here is calculated by the following equation. Wardell's degree of sphericity = (diameter of a circle having the same area as the projected area of the particles) / (diameter of a circle circumscribing the projected surface of the particles) Next, a method of producing a toner by an emulsion polymerization particle aggregation method will be described.

The production method is described in Patent Publication 63-28117.
The details will be briefly described in 2, 63-282749 and the like. First, preliminary dispersion of a monomer, a colorant, and the like is performed. Then, the preliminarily dispersed monomer mixture is added to an aqueous solution mixture containing an emulsifier, and the mixture is stirred to produce emulsified fine particles. Here, a polymerization initiator is added, and the mixture is heated to perform a radical polymerization reaction. The polymerization is carried out at a temperature of 50 ° C. or higher, generally 70 to 90 ° C. In this step, fine particles having an average particle size of 1 to 3 μm are obtained. Next, a salting-out agent was added while stirring the liquid in which the polymer was dispersed to aggregate fine particles,
Further, by heating at a temperature equal to or higher than the glass transition point of the resin while continuing stirring, the particles are fused together (aging).
A toner having an average particle size of 5 to 20 μm is obtained.

After the aging, the product is recovered by a suitable method such as washing, filtration and decantation to obtain an emulsion polymerized particle aggregation method toner. The monomer used in the present invention is not limited to styrene-acryl, but may be any monomer having one ethylenically unsaturated bond in one molecule. For example, styrene, o-methylstyrene, m-
Methylstyrene, p-methylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene,
3,4-dichlorostyrene, p-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert-butylstyrene, pn-nonylstyrene, pn-octylstyrene,
Styrene and its derivatives such as pn-hexylstyrene and pn-dodecylstyrene; ethylenically unsaturated monoolefins such as ethylene, propylene, butylene and isobutylene; vinyl halide such as vinyl chloride, vinylidene chloride, vinyl bromide and vinyl fluoride , Vinyl acetate, vinyl propionate, vinyl esters such as vinyl benzoylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, Α-methylene fatty acid monocarboxylic acid esters such as 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, and diethylaminoethyl methacrylate;
Acrylic esters such as methyl acrylate, ethyl acrylate, n-butyl acrylate and isobutyl acrylate; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl isobutyl ether; vinyl methyl ketone, vinyl hexyl ketone and methyl iso Vinyl ketones such as propenyl ketone, N-vinyl pyrrole,
Examples include n-vinyl compounds such as N-vinylcarbazole, N-vinylindole, and N-vinylpyrrolidone, and acrylic or methacrylic acid derivatives such as vinylnaphthalenes, acrylonitrile, methacrylonitrile, and acrylamide. These can be used alone or as a mixture.

As the emulsifier, a known emulsifier, for example, a soap, a cationic activator, an anionic activator, a fluorine activator and the like can be used. Generally, these emulsifiers are used in an amount of 0.01 to 1% by weight relative to water (more preferably 0.1 to 1% by weight).
-0.5% by weight). Next, as the polymerization initiator, known thermal polymerization initiators, for example, persulfates such as potassium persulfate, azobisisobutyronitrile, benzoyl peroxide, methyl ethyl ketone passoxide, isopropyl peroxycarbonate, etc. Polymerization can also be carried out using a redox initiator. Generally, the amount of the polymerization initiator used is generally about 0.01 to 10% (more preferably 0.05 to 5% by weight) of the weight of the polymerizable mixture.

As the coloring agent, known pigments and dyes can be used. For example, black pigments include channel black and furnace black, and coloring pigments include cadmium yellow, pyrazolone red, phthalocyanine blue B, phthalocyanine green, and the like. As the dye, C.I. I Direct Red 1, C.I. I Direct Blue 1 and others.

Further, additives such as a charge control agent and a fluidity modifier may be added to the toner raw material components as required.

[0014]

As a result of intensive studies, it was found that the toner produced by the emulsified fine particle agglomeration method had a Wardel sphericity of 0.90 to 0.85.
In this manner, the toner is not crushed by the stress of the layer thickness regulating blade, and the high printing quality can be maintained for a long period of time by exhibiting better cleaning properties. This is because (1) the toner surface is not crushed by the layer-thickness regulating blade because there is no acute-angled portion, and (2) the toner shape is not a true sphere but has a certain degree of irregularity. It is considered that the contact area between the cleaning blade and the cleaning blade becomes large and the cleaning blade completely collects the cleaning blade.

[0015]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to Examples, but it should not be construed that the invention is limited thereto. First,
An electrophotographic recording apparatus for performing the non-magnetic one-component developing method of the present invention will be described.

In FIG. 1, storage means 2 for developer 1
A roller-shaped developer collecting unit 4 having a plastic material adhered to the surface thereof is provided between the developer carrier 3 and the developer carrier 3 which transports the developer 1 along a predetermined circulation path including a developing area. Body 3
It is provided so as to come into contact with. And the developer carrier 3
A bias voltage (hereinafter referred to as a collection bias) is applied between the developer 1 and the developer collection unit 4 in a direction from the developer carrier 3 toward the developer collection unit 4.
This is because the mechanical and electrical history on the developer carrier 3 is stably and surely eliminated by performing not only mechanical recovery by contact but also electrical recovery by a recovery bias. . Therefore, the developer 1 stored in the storage unit 2 is newly supplied to the developer carrier 3 while being in contact with the developer carrier 3, and the developer is charged by mechanical friction. A layer is formed on the developer carrying member 3, the layer thickness is regulated to a desired thickness by a layer thickness regulating blade 5, and the layer is conveyed to a development area to perform development.

Reference numeral 6 denotes a latent image carrier, which conveys the latent image formed on the surface to the developing section and conveys the formed developer image to a position where the image is transferred to recording paper. This latent image carrier 6
A photoconductor (organic photoconductor, selenium photoconductor, amorphous silicon photoconductor, or the like) or an insulator that is a photoconductive material can be used depending on the latent image forming method. The developer carrier 3 used here is formed of porous polyurethane having pores of 3 to 20 μm so that toner of about 10 μm does not enter. In our experiments, the porous state
It was confirmed that, even in the continuous bubble state, when the pore size was set to 20 μm or less, the toners supported each other in the pores and did not enter. When the pores have a size of 20 μm or more, the intrusion of toner can be prevented by forming a single cell. However, the distance between the latent image and the conductor (in this case, the sponge itself) is large in the concave portion, and the toner in that portion has a developing bias. , And a low density portion corresponding to the concave portion of the sponge appears on the print. Therefore, the pore size is desirably 20 μm or less. The volume resistance of the sponge is 10 ⁴ to
When the electric resistance value is desirably in the range of 10 ¹⁰ Ωcm, a large current flows into the layer thickness regulating blade 5 to generate Joule heat and burn the developer carrier 3. The surface hardness of the developer carrier was set to 50 ° or less by an Asker C hardness meter. Example 1 Monomer Styrene (manufactured by Wako Pure Chemical) 90 parts by weight Butyl acrylate (manufactured by Wako Pure Chemical) 10 parts by weight n-butyl methacrylate (manufactured by Wako Pure Chemical) 5 parts by weight Colorant carbon black (150T, manufactured by Degussa) 2 Parts by weight Azochrome dye (S: 34, manufactured by Orient) 2 parts by weight Emulsifier Neogen SC (manufactured by Daiichi Kogyo Seiyaku) 0.2 parts by weight Thermal polymerization initiator benzoyl peroxide 0.2 parts by weight Salting-out agent 10% saline 0.05 parts by weight External additive Hydrophobic silica H-2000 (manufactured by Hoechst) 0.5 parts by weight Disperser (manufactured by Yamato Scientific Co., Ltd.)
The mixture was stirred for 3 minutes to prepare a monomer mixture. Next, this monomer mixture was put into 500 parts by weight of distilled water to which a polymerization initiator and an emulsifier had been added, and stirred at room temperature (20 ° C.) for 3 minutes using a disperser (4,000 rpm). Thereafter, the disperser was changed to a three-one motor and heated to 60 ° C. while stirring at 100 rpm to completely polymerize the monomer mixture. Next, a salting-out agent was added dropwise to the resulting fine particles dispersed in water, heated to 100 ° C., and ripened under a microscope until the toner had a Wardel sphericity of 0.90. Here, the spherical degree of Wardell was calculated by arbitrarily selecting 100 toners from a micrograph and measuring the diameters of a circle circumscribing the toner and a circle having the same area as the toner by visual measurement. Next, the toner dispersed in water was centrifuged and separated by filtration. This toner was repeatedly washed with water until ph became 8 or less to obtain a toner. To this toner, 0.5 parts by weight of hydrophobic silica was added as a fluidity modifier.

200 g of the toner is applied to the above-mentioned apparatus (20 sheets /
), And a continuous printing test was performed to examine the print quality, the particle size distribution of the toner on the developer carrying member, and the change in cleaning performance. As a result, even after continuous printing of 100,000 sheets, there was no problem in print quality, toner particle size distribution, and cleaning property. Example 2 Emulsified fine particles were prepared in the same manner as in Example 1, and after addition of a salting-out agent, the mixture was heated to 100 ° C. and aged until the Wardel sphericity was 0.85. Example 1
The same process as described above is performed to produce a toner.
A continuous printing test of 100,000 sheets was performed.

As a result, there was no problem in print quality, toner particle size distribution, and cleaning property even after the test. Comparative Example 1 Binder resin Styrene acrylic resin (Tg = 60 ° C., softening point = 140 ° C.) 95 parts by weight Colorant carbon black (150T, manufactured by Degussa) 2 parts by weight Azochrome dye (S: 34, manufactured by Orient) 2 parts by weight Part External additive Hydrophobic silica (H-2000, manufactured by Hoechst) 0.5 part by weight After mixing the binder resin and the coloring agent, they are melt-kneaded, and the obtained resin mass is roughly pulverized by a rotoplex, and then jet-milled. (PJM crusher, manufactured by Nippon Pneumatic Industries)
Then, the pulverized product was classified with an air classifier (manufactured by Alpine) to obtain a toner having a Wardel sphericity of 0.64. To this toner, 0.5 parts by weight of hydrophobic silica was added as a fluidity modifier to prepare a developer, and a continuous printing test of 100,000 sheets was performed using the above apparatus.

As a result, "smearing" occurred in the printed sample after the test, the fog increased, and the printing quality was greatly reduced as compared with the initial stage. In addition, the amount of fine powder having a particle size of 5 μm or less increased, the particle size distribution became broad, and a toner layer that was not cleaned was formed on the drum. Comparative Example 2 Emulsified fine particles were prepared in the same manner as in Example 1, and after adding a salting-out agent, the mixture was heated to 100 ° C. and aged until the Wardel sphericity was 0.78. Example 1
The same process as described above is performed to produce a toner.
A continuous printing test of 100,000 sheets was performed.

As a result, "smearing" occurred in the printed sample after the test, the fog increased, and the printing quality was greatly reduced as compared with the initial stage. In addition, the amount of fine powder having a particle size of 5 μm or less increased, the particle size distribution became broad, and a toner layer that was not cleaned was formed on the drum. Comparative Example 3 Emulsified fine particles were prepared in the same manner as in Example 1, and after adding a salting-out agent, the mixture was heated to 100 ° C. and aged until the Wardell's sphericity reached 0.96. Example 1
A toner was prepared by performing the same treatment as described above, and a printing test was performed using the above-described apparatus.

[0022]

As described above, according to the present invention, it is possible to maintain good printing quality for a long period of time without deteriorating the printing characteristics even in continuous printing, having good charging characteristics and cleaning properties. Can be.

[Brief description of the drawings]

FIG. 1 shows an electrophotographic recording apparatus.

[Explanation of symbols]

 1: developer 2: storage means 3: developer carrier 4: developer recovery means 5: layer thickness regulating blade 6: latent image carrier

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-220358 (JP, A) JP-A-63-235956 (JP, A)

Claims (1)

(57) [Claims] 1. A non-magnetic one-component developing method in which a developer conveyed by a developer carrier to a latent image carrier is frictionally charged by a layer thickness regulating member and development is performed while regulating a layer thickness. As a developer, obtained by emulsion polymerization particle aggregation method,
A non-magnetic one-component developing method using a toner having a Wardel sphericity of 0.90 to 0.85.