JPH10319622A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device using a toner having excellent shape holding property so that the particles do not break even when mechanical stress is added in a developing machine. SOLUTION: This device is equipped with a developing machine 4 which regulates the carrying amt. of a developer on a developer carrier 42 by a regulating member 46 and which carries the developer to a developing region R facing to an electrostatic latent image carrier 1. The toner particles of the developer consist of fine particles produced by emulsion polymn. of a binder resin and a coloring agent. When the shape factor M1 of the toner is defined by I: M1=(π.dmax<2> /4A)×100, M1 satisfies the condition expressed by II: M1<=Mw/1000+115, wherein dmax is the max. diameter, A is the cross-sectional area of the toner, and Mw is the weight average mol.wt. of the binder resin. In order to obtain good cleaning property, M1 is preferably controlled to >=127.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus such as an electrophotographic copying machine, a laser printer, and a facsimile provided with a developing device for developing an electrostatic latent image with a dry developer. In particular, the present invention relates to an image forming apparatus using a toner manufactured by an emulsion polymerization method as a developer.

[0002]

2. Description of the Related Art In an image forming apparatus using an electrophotographic method or an electrostatic recording method, a method of visualizing image information via an electrostatic latent image is currently used in various fields. For example, in electrophotography, an electrostatic latent image is formed on a photoconductor by an exposure process following a charging process, the electrostatic latent image is visualized with a developer, and image information is reproduced through a transfer and fixing process. . The developer includes a one-component developer using a magnetic toner or a non-magnetic toner alone, and a two-component developer including a toner and a carrier. Toner is usually made of thermoplastic resin as pigment,
It is produced by a kneading and pulverizing method in which the mixture is melt-kneaded with a releasing agent such as a wax or a charge controlling agent as required, then finely pulverized, and further classified. If necessary, inorganic or organic fine particles may be added to the surface of the toner particles in order to improve fluidity and cleaning properties. In the ordinary kneading and pulverizing method, the shape and surface structure of the toner are indefinite, and vary slightly depending on the pulverizability of the material to be used and the conditions of the pulverizing process, but it is difficult to control the shape and surface structure of the toner. It is also difficult to narrow the particle size distribution of the toner.

In the case of amorphous toner, the adhesion area to the developing roll in a one-component developer and the adhesion area to a carrier in a two-component developer differ for each toner particle. Therefore, the ease of development is different. Since toners having different particle diameters have different charge amounts of one toner particle, developing easiness is different. Due to these differences, the easily developable toner is selectively developed and the hardly developable toner remains in the developing device, so that the developability changes with time. Also, in the transfer to the recording paper, similarly, since there is a toner that is easily transferred and a toner that is hardly transferred, image quality deterioration such as scattering of the toner is likely to occur. Further, when a toner is manufactured by internally adding a release agent such as a wax, the release agent may be exposed on the toner surface due to a combination with a thermoplastic resin. In particular, in the case of a combination of a resin, which is imparted with elasticity by a high molecular weight component and is hardly pulverized, and a brittle wax such as polyethylene, wax is often exposed on the toner surface. Exposure of the release agent is advantageous for the releasability at the time of fixing and cleaning of the toner remaining on the photoreceptor after transfer. However, since the release agent on the toner surface is easily moved by mechanical force, the development roll, Contamination of the photoreceptor and carrier is likely to occur, leading to a decrease in the reliability of the image forming apparatus.

As a solution to these problems, a resin dispersion in which resin particles of 1 μm or less are dispersed, a colorant and, if necessary, a colorant dispersion in which release agent particles are dispersed, are mixed. And after aggregating the release agent particles to a predetermined toner particle size, heating to the glass transition temperature or higher of the resin,
An emulsion polymerization method for obtaining a colored toner in which aggregates are fused and united has been proposed. In the emulsion polymerization method, the shape of the toner can be uniformly adjusted, and the particle size distribution can be narrowed. In addition, by controlling the conditions of fusion coalescence, from a raspberry shape with a large unevenness to a potato shape with a small unevenness,
Further, it can be controlled to a spherical shape. In addition, since the release agent particles can be confined inside, the release agent is not exposed on the toner surface. However, the Raspberry shape having a large degree of unevenness has a problem that the toner collapses when subjected to a mechanical stress in the developing device. On the other hand, the spherical toner passes through the blade with a cleaning device using an elastic rubber blade.Therefore, the toner remaining on the photoconductor after the transfer process and the patch formed on the photoconductor to control development conditions are removed. There is a problem that cleaning cannot be performed. Note that a patch refers to a development area formed on a photoconductor in order to measure the reflectance of light at a predetermined number of development steps and to control an optimal development density based on the reflectance.

[0005]

In order to solve this problem, Japanese Patent Application Laid-Open No. 148926/1994 defines the shape factor S of toner as (perimeter) ² / (area × 4π) × 100. Then, the shape of the toner is grasped by distribution, and the ratio of the toner particles in which S is less than 116 and larger than 145 is 3
An image forming method using a developer whose content is 0% or less and whose sum is 40% or less is disclosed. In addition, a toner having a predetermined relationship between the shape factor S and a shape factor (distortion coefficient) defined by SF = [π × (maximum length) ² / (4 × area)] × 100 is disclosed in 61-279864
And Japanese Patent Application Laid-Open No. 1-185654. However, simply defining the shape factors S and SF disclosed in these publications does not always provide sufficient shape retention of the toner, and the toner collapses during the operation of the developing device. In some cases, problems such as spreading, adhesion of the toner to the developer carrier, and poor cleaning may occur. Therefore, an object of the present invention is to solve the above-mentioned problems, and to form an image using a toner having excellent shape retention without causing particles to collapse even by mechanical stress in a developing device. It is to provide a device. It is another object of the present invention to provide an image forming apparatus having excellent toner cleaning properties.

[0006]

Means for Solving the Problems The present inventors have intensively studied and studied to improve the shape retention of toner. As a result, the easiness of toner collapse not only depends on the shape factor but also depends on the shape factor. It has been found that it is also related to the molecular weight of the binder resin constituting the toner, and further, the finding that the shape factor Ml (SF) representing the flatness is preferable as the toner shape rather than the shape factor Pm (S) representing the degree of unevenness. I got it. When a toner satisfying a predetermined condition between the shape factor Ml and the molecular weight is used, the toner particles are not collapsed, and there is a possibility that the toner adheres to the developer carrier and cleaning failure occurs. As a result, the present inventors have found that a high quality image can be formed without any problem. That is, in the image forming apparatus of the present invention, the amount of the developer carried on the developer carrier is regulated by the developer regulating member so that a predetermined amount of the developer is opposed to the electrostatic latent image carrier. A developing device that transports the electrostatic latent image on the surface of the electrostatic latent image carrier with a developer by a potential difference between the electrostatic latent image carrier and the developer carrier. Is composed of fine particles manufactured by an emulsion polymerization method in which at least a binder resin and a colorant are united, and the shape factor Ml of the toner is represented by the formula (1), the shape factor Ml is represented by the following formula ( The condition represented by 2) is satisfied. Ml = (π · dmax ² / 4A) × 100 (1) Ml ≦ Mw / 1000 + 115 (2) where dmax: maximum diameter of toner A: cross-sectional area of toner Mw: weight average molecular weight of binder resin In order to ensure good cleaning performance, the toner preferably has a shape factor Ml of 127 or more.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
FIG. 1 is an explanatory diagram of an image forming apparatus shown as an example of the present invention. In FIG. 1, an image is formed by irradiating a light beam such as a laser beam corresponding to image information after the surface of an electrostatic latent image carrier 1 composed of a photosensitive drum rotating in the direction of an arrow is uniformly charged by a charger 2. The surface of the latent image carrier 1 is exposed by the writing means 3, and an electrostatic latent image is formed by an electrostatic potential difference. The electrostatic latent image is formed into a visible toner image by a developing device 4 containing a developer. This toner image is electrostatically transferred by the transfer charger 5 to the recording paper P supplied from the paper feed tray 6 at a predetermined timing. The recording paper P on which the toner image has been transferred is separated from the latent image carrier 1 by, for example, a separation charger 7, and then conveyed to a fixing device 8 to be fixed.
Emitted outside the machine. In the cleaning device 9, an elastic rubber blade 9a having a fixed end abutting on the downstream side in the rotation direction of the latent image carrier 1 and a free end abutting on the upstream side in the rotation direction of the latent image carrier 1 is provided. Have been. The blade 9a scrapes off toner remaining on the latent image carrier 1 after transfer and patches formed for controlling development conditions. Further, the residual charges on the latent image carrier 1 are removed by the neutralizer 10 to prepare for the next image forming process.

FIG. 2 shows an example of the developing device (4) in the present invention. In the figure, a developer carrier 42 is arranged at an opening of a developer container 41 so as to face the electrostatic latent image carrier 1, and the developer adhered to the surface by rotating in the direction of the arrow moves to the development region R. Conveyed. The minimum distance between the developing region R where the latent image carrier 1 and the developer carrier 42 are close to each other is 0.3 to 0.8 m.
m. The developer carrier 42 includes a rotatable developing sleeve 43 and a magnet roll 44 in which a plurality of magnetic poles are arranged along the peripheral surface.
Is fixed inside the carrier 42. Developing sleeve 4
When 3 rotates, the developer is attracted to the surface of the developer carrier 42 according to the magnetic field formed along the peripheral surface. At the lower part of the developer container 41, developer conveying and stirring means 45, 45 are arranged, and the developer supplied to the developer supply area by the conveying and stirring means 45 is transferred to the surface of the developer carrier 42 as described above. The developer is sucked and further regulated to a uniform thickness by the developer regulating member 46, and a predetermined amount is conveyed to the developing region R. The distance between the developer carrier 42 and the regulating member 46 is 0.4 to
It is set to about 0.9 mm. The developer in which the toner has been consumed in the developing region R is separated from the developer carrier 42 and is stirred and mixed with the developer in the container 41 by the developer conveying and stirring means 45. When the developer is a two-component developer,
The toner newly supplied by the toner supply means (not shown) and the developer in the container 41 are stirred to make the toner concentration uniform.

FIG. 3 shows the surface potential of the electrostatic latent image carrier 1 in the charging step, the exposing step, and the developing step. First,
The surface potential of the electrostatic latent image carrier 1 is uniformly charged by the charger 2 to the non-image portion potential Vh. Next, exposure is performed by the image writing unit 3, the surface potential (absolute value) of that portion is reduced to the image portion potential Vl, and an electrostatic latent image corresponding to image information is formed. Next, a bias voltage Vb is applied to the developer carrier 42 from the power supply 47, and the toner on the developing sleeve 43 adheres to the latent image carrier 1 due to a potential difference (development potential) from the image portion potential Vl. The latent image is visualized. At this time, a potential difference from the non-image portion potential Vh (cleaning potential)
This prevents toner from adhering to the non-image portion of the latent image carrier 1. The bias voltage Vb may be a superimposed voltage in which an AC component having a voltage of 0.5 to 2 kV _PP and a frequency of 1 to 10 kHz is superimposed on a DC component as necessary.

The toner used in the present invention comprises the following emulsifying polymers comprising a binder resin and a colorant as essential components and, if necessary, internal additives such as a release agent and a charge controlling agent. Manufactured legally. That is, the hetero-aggregation is advanced by mixing the binder resin dispersion containing the surfactant and the pigment (colorant) dispersion containing the same surfactant. When the aggregated particles grow to the diameter of the toner, the aggregated particles are heated to a temperature equal to or higher than the glass transition temperature (Tg) of the binder resin to fuse and aggregate the aggregates. In this emulsion polymerization method, the toner shape can be controlled from an irregular shape to a spherical shape by adjusting the heating conditions. The particles obtained by the above-mentioned coalescence treatment are then washed and dried to produce toner particles. The resin dispersion can contain up to 80% by weight of a binder resin, and the amount of the surfactant added to the binder resin is 3 to 20%.
It is preferably in the range of% by weight. The pigment dispersion is
A coloring agent is added to a surfactant aqueous solution of about 0.5 to 2% by weight.
It can be prepared by containing up to 0% by weight. Also,
The mixing ratio of the colorant to the binder resin varies depending on the type of the colorant, but is generally in the range of 3 to 15% by weight. As the surfactant to be added at the time of preparing the resin dispersion, the pigment dispersion, and the like, and producing the toner as required, anionic, cationic, and nonionic surfactants are appropriately used.

In the coagulation process, the dispersion is mixed in the presence of a coagulant, usually at 40 to 60 ° C. for 30 minutes to 3 hours. At this time, the larger the processing temperature and the longer the processing time, the larger the diameter of the aggregate. As the aggregating agent, an amphoteric surfactant alone or an anionic surfactant and a cationic surfactant are used in combination, and a surfactant having a different ionicity may be added to the above dispersion in advance, or the surfactant may be mixed at the time of mixing each dispersion. An ionic surfactant may be separately added so that the ionicity of the surfactant is different. In the subsequent coalescing process, the mixture containing the aggregates is heated to 80 to 110 ° C., which is equal to or higher than the above Tg. At this time, the higher the processing temperature and the longer the processing time, the more spherical the aggregate becomes. Although it depends on the type of the colorant, for example, 90 ° C. for 5 hours or 110 ° C.
If processed for 3 hours, it will be united in potato shape,
If the temperature is higher or the time is longer than the processing conditions, the shape becomes closer to a sphere, and if the temperature is lower or the time is shorter, a Raspberry toner can be obtained. The emulsion polymerization method is a method in which a binder resin dispersion, a pigment dispersion, a release agent dispersion, and the like are mixed as necessary to aggregate the toner components, and the aggregates in a uniform mixed state are united. Therefore, a uniform toner composition can be obtained. Also, 2 having different molecular weights
By using more than one kind of binder resin, the molecular weight distribution of the toner can be easily controlled.

As the thermoplastic binder resin constituting the toner, the following monomer polymers are used. For example, styrenes such as styrene, p-chlorostyrene, α-methylstyrene, vinylnaphthalene, acrylic acid, methyl acrylate, ethyl acrylate, n-propyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, methacrylic acid , Methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate and the like, or vinyl esters thereof, and vinyl unsaturated nitriles such as acrylonitrile and methacrylonitrile Vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl isobutyl ether;
Vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone and vinyl isopropyl ketone; polymers such as olefins such as ethylene, propylene and butadiene; copolymers of the above two or more monomers; or mixtures of these polymers. Can be Further, polyester resin, urethane resin, polyamide resin, epoxy resin, cellulose resin, polyether resin (for example, polyoxyoctylene glycol, polyoxide decylene glycol, polyoxyoctadecylene glycol, ethylene oxide adduct of bisphenol A, Non-vinyl condensed resins such as the above-mentioned ester or ether derivatives), mixtures of these resins with the above-mentioned vinyl polymers or copolymers, and graft copolymers with vinyl polymers. In the case of a vinyl monomer, for example, a binder resin dispersion can be prepared by emulsion polymerization in an aqueous ionic surfactant solution. In the case of other resins, if the resin is soluble in an organic solvent such as ethyl acetate, acetone or tetrahydrofuran, the resin is dissolved in the organic solvent and an aqueous solution in which an ionic surfactant or a polymer electrolyte is dissolved, and a homogenizer or the like is used. The binder particles can be prepared by dispersing or dissolving the resin particles in water with the dispersing device described above, and then heating or reducing the pressure to evaporate the organic solvent.

[0013] Colorants for toner include carbon black, chrome yellow, Hansa yellow, benzidine yellow, slen yellow, quinoline yellow, permanent orange GTR, pyrazolone orange, vulcan orange, pyrazolone red, watch red, permanent red, and duPont oil. Red, Lisor Red, Lake Red C, Brilliant Carmine 3B, 6
B, rhodamine B lake, rose bengal, aniline blue, ultramarine blue, chaco oil blue, methylene blue chloride, phthalocyanine blue, phthalocyanine green, malachite green oxalate, and other pigments, acridine, azine, phthalocyanine, aniline black , Azo, azomethine, benzoquinone, anthraquinone, xanthene, dioxazine, thiazine, thiazole, indigo,
Thioindigo, polymethine, diphenylmethane,
Various dyes such as triphenylmethane dyes are exemplified.
One or more of these pigments and dyes can be used, and pigments and dyes may be used in combination.

When the toner component of the developer is a magnetic toner, a magnetic material such as ferrite, magnetite or a magnetic metal such as reduced iron, cobalt, nickel or manganese or an alloy thereof or a complex of ethylenediaminetetraacetic acid containing these metals. Is contained in the toner. The magnetic material can be used as a colorant, in which case all or part of the colorant is replaced by a magnetic material of the same color. As the internal additive, a release agent such as polyethylene wax, polypropylene wax, paraffin wax, and microcrystalline wax can be used in order to prevent occurrence of offset at the time of fixing. Also, charge control agents such as quaternary ammonium chloride, nigrosine dye, metal-containing complex dyes such as aluminum, iron and chromium, and triphenylmethane pigments can be used. Among these charge control agents, materials which are hardly soluble in water are preferably used from the viewpoints of controlling ionic strength affecting aggregation and stability at the time of integration and preventing wastewater contamination.

Among the surfactants used in the preparation of the dispersion and the production of the toner, the anionic surfactants include fatty acid metal salts such as potassium laurate, sodium oleate and castor oil fatty acid sodium, octyl sulfate, lauryl sulfate, and the like. Sulfates such as dilauryl ether sulfate and nonylphenyl ether sulfate, lauryl sulfonate, dodecyl (lauryl) benzene sulfonate, triisopropyl naphthalene sulfonate, dibutyl naphthalene sulfonate,
Sulfonates such as naphthalene sulfonate formalin condensate, lauric amide sulfonate, oleic amide sulfonate, etc., phosphates such as isopropyl phosphate, lauryl phosphate, nonylphenyl ether phosphate, disodium octyl sulfosuccinate, dioctyl sodium sulfosuccinate, sulfosuccinate And sulfosuccinates such as disodium lauryl acid and sodium lauryl polyoxyethylene sulfosuccinate. Examples of the cationic surfactant include amine salts such as laurylamine hydrochloride, stearylamine hydrochloride, stearylamine acetate, oleyl (cis-9-octadecenyl) amine acetate, stearylaminopropylamine acetate, lauryltrimethylammonium chloride, and the like. Dilauryldimethylammonium chloride, distearyldimethylammonium chloride, laurylbishydroxyethylmethylammonium chloride, oleylbispolyoxyethylenemethylammonium chloride, lauroylaminopropyldimethylethylammonium ethosulfate, lauroylaminopropyldimethylhydroxyethylammonium perchlorate, etc. And quaternary ammonium salts.

Examples of the nonionic surfactant include polyoxyethylene octyl ether, polyoxyethylene lauryl ether, polyoxypropylene lauryl ether,
Polyoxyalkylene ethers such as polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene octyl phenyl ether, and polyoxyethylene nonyl phenyl ether; polyoxyethylene laurate, polyoxypropylene laurate, polyoxyethylene stearate , Polyoxyalkylene esters such as polyoxyethylene oleate; N- (polyoxyethylene) laurylamine, N-
N- (polyoxyalkylene) such as (polyoxyethylene) stearylamine, N- (polyoxyethylene) oleylamine, N- (polyoxyethylene) amine derived from soybean oil, and N- (polyoxyethylene) amine derived from tallow
Amines; N, N-bis (polyoxyalkylene) amines; N, N-bis (polyoxyethylene) lauric amide, N, N-bis (polyoxyethylene)
N, N-bis (polyoxyalkylene) fatty acid amides such as stearic acid amide and N, N-bis (polyoxyethylene) oleic acid amide; N, N-bis (hydroxyethyl) lauric acid amide, N, N- Dialkanolamides such as bis (hydroxyethyl) stearic acid amide and N, N-bis (hydroxyethyl) oleic acid amide; alkylene oxide addition of alcohol derived from vegetable oils such as polyoxyethylene castor oil-derived ether and polyoxyethylene rapeseed oil-derived ether Addition of alkylene oxide to sorbitan fatty acid ester such as polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate And the like. One or more of the above surfactants may be used, and it is also effective to use a combination of an anionic surfactant and a nonionic surfactant or a combination of a cationic surfactant and a nonionic surfactant.
When an anionic surfactant and a cationic surfactant are used in combination, they also function as the coagulant.

As a means for dispersing the toner component, a general dispersing apparatus such as a rotary shearing homogenizer or a ball mill, a sand mill, or a dyno mill having a medium can be used. The toner used in the present invention has a chargeability,
An external additive may be added to improve powder fluidity, lubricity, and the like. For example, when adding by a wet method, an external additive such as silica, alumina, titania, calcium carbonate, magnesium carbonate, and tricalcium phosphate is added to a surfactant or a polymer acid such as poly (meth) acrylic acid or polyaryl. It can be dispersed using a dispersion stabilizer such as a polymer base such as an amine. Also, when adding by the dry method,
External additives such as inorganic fine particles such as silica, alumina, titania, and calcium carbonate, fine particles of fatty acid metal salts such as zinc stearate, vinyl resin such as polymethyl methacrylate, and fine resin particles such as polyester and silicone resin are dried. It can be added to the toner by shearing and used as a flow aid or a cleaning aid.

As the shape factor representing the shape of the toner, there are generally known Pm calculated from the circumference and the area when the toner is projected onto a plane, and Ml calculated from the maximum diameter and the area. Pm is defined by S described above, and represents the degree of unevenness of the toner. Ml is defined by the aforementioned SF, and represents the flatness of the toner. Both Pm and Ml are 100 in a true sphere, and the numerical value increases as the degree of unevenness or flatness increases.
According to the emulsion polymerization method, it is possible to control the shape of the toner from a raspberry shape having a large degree of unevenness to a potato shape having a small degree of unevenness, and further to a spherical shape. More specifically, the initial particle size in each dispersion is 1 μm or less,
While forming tertiary and higher order aggregates, for example, 0.1 μm
Particles of about 0.5 to 1.0 μm are secondary aggregated, and particles of 5 to 8 μm that finally become the toner diameter are aggregated to form particles of 2 to 3 μm to produce a toner. That is, particles having a diameter of about 1/4 to 1/2 of the toner diameter are aggregated. for that reason,
The Raspberry-shaped toner in which coalescence has not progressed much has a large flatness, and as the coalescence progresses, the shape gradually approaches a spherical shape. Therefore, the correlation with Ml representing the flatness increases once at the time of coalescence. Further, even if the shape factors are the same, the toner having a large weight average molecular weight Mw of the binder resin has a higher strength when united, so that a mechanical stress is applied to the toner having a smaller Mw of the binder resin. Sometimes it is hard to collapse. In the developing device, a large mechanical stress is generally applied to the toner when regulating the transport amount of the developer to the developer carrier.
For example, in the case of a one-component developer, since an elastic blade is brought into contact with a developer carrier at a predetermined linear pressure, a pressing force is applied when toner passes between the developer carrier and the blade. Also,
In the case of the two-component developer, a rigid blade is provided at a distance from the developer carrier so as to have a predetermined conveyance amount. Therefore, the developer forms a pool by the blade and receives a pressing force.

According to the present invention, when the shape factor Ml of the toner represented by the following formula (1) satisfies the condition represented by the following formula (2), the toner particles are subjected to mechanical It does not crumble even under severe stress. In the expression, dmax indicates the maximum diameter of each toner, and A indicates the cross-sectional area of the same toner. Ml = (π · dmax ² / 4A) × 100 (1) Ml ≦ Mw / 1000 + 115 (2) Here, the shape factor Ml of the toner in the present invention is 10
In a state where about 0 toners do not overlap each other, the secondary projection images of the individual toners enlarged using an optical microscope are taken into an image analyzer (Luzex III: manufactured by Nicole) using a CCD camera, and the three The average value obtained from the measured values of dmax and A of the projected image according to the above equation (1) and obtained from about 300 toners in total. Incidentally, the relationship between the shape of the toner and the coefficient Ml is 120 or less for a spherical shape and 120 to 12 for a slightly distorted shape of a sphere.
5, 130-135 in potato shape, 13 in raspberry shape
8 to 150. The shape factor Ml of the toner manufactured by the ordinary kneading and pulverizing method is about 138 to 145.

The toner described above may be used as a magnetic one-component developer or a non-magnetic one-component developer without using a carrier, or may be used as a two-component developer using a carrier. In the case of a two-component developer, the carrier is not particularly limited, but an iron powder-based carrier, a ferrite-based carrier, a resin-coated ferrite-based carrier, a magnetic powder-dispersed carrier, or the like is used. Among them,
A carrier in which the resistance value is adjusted by coating a resin on ferrite particles is preferable. The particle size of the carrier is 20-1
It is preferably in the range of 00 μm. In the case of a two-component developer, the toner is generally mixed with the carrier at a ratio of 2 to 20% by weight, preferably 4 to 10% by weight. The present invention is not particularly limited as long as it is an image forming apparatus provided with a developing device that regulates the layer thickness of the developer on the developer carrier. For example, a normal mono-color image forming apparatus and a photosensitive drum The present invention is applied to a color image forming apparatus that carries a multi-toner image on one electrostatic latent image carrier, an intermediate transfer type color image forming apparatus, and the like. Further, as the developing method, a magnetic or non-magnetic one-component developing method, the above-described magnetic brush developing method of the magnet fixed type or the rotating type, or the like can be adopted.

[0021]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to the following Examples. (Image Forming Apparatus) FIG. 4 is a schematic view of an image forming apparatus for carrying out the present invention. Components having the same functions as in FIG. 1 are denoted by the same reference numerals. In FIG. 4, an electrostatic latent image carrier 1 composed of a photoconductive drum having a negatively charged organic photosensitive layer is arranged inside the main body of the image forming apparatus U. A platen glass 11 on which an original is placed is fitted on the upper surface of the image forming apparatus U main body. Below the platen glass 11, the reflected light of the document emitted from the light source is converged on the CCD, and the light beam L is rotated in the direction of the arrow through the image processing circuit, the optical writing control device, and the light beam writing device. The image writing means 3 for irradiating the surface of the latent image carrier 1 is arranged. At this time, an electrostatic latent image is formed on the latent image carrier 1 uniformly charged by the charger 2 due to a potential difference from an exposed portion. The surface potential when the electrostatic latent image is formed is -300 V in the image portion Vl and -700 V in the non-image portion Vh serving as the background.

Around the electrostatic latent image carrier 1, a developing device 4 shown in FIG. A transfer charger 5 for transferring the visualized toner image onto the recording paper P;
Charging device 7 for removing the toner from the surface of the latent image carrier 1, a cleaning device 9 for removing residual toner on the latent image carrier 1,
Further, a static elimination lamp 10 for removing residual charges on the surface of the latent image carrier 1 is sequentially arranged. An extractable paper feed tray 6 that accommodates recording paper P is disposed below the main body of the image forming apparatus U. The recording paper P is carried out by a pickup roller 12, and the latent image carrier 1 and the transfer charger 5 are transferred via a pair of upper and lower guide plates 13 in synchronization with the writing operation of the image writing means 3. The sheet is conveyed to the opposite transfer section. A guide plate 14, a fixing device 8, and a pair of discharge rollers 15 are sequentially arranged on the downstream side of the transfer section in the transport direction of the recording paper P. A paper output tray 16 is mounted outside the image forming apparatus U main body side. The recording paper P to which the unfixed toner image has been transferred by the transfer unit is conveyed along a guide plate 14, subjected to a fixing process in a fixing device 8, and then discharged from a discharge roller 15 to a discharge tray 16.

In FIG. 2 described above, a developer container 41 is filled with a two-component developer described later, and a developer carrier 42 that is partially exposed at a portion that opens to face the latent image carrier 1. Are arranged at a minimum distance of 0.4 mm from the latent image carrier 1. The developer carrier 42 includes a stainless steel developing sleeve 43 having an outer diameter of 30 mm and a magnet roll 44 fixed inside the developing sleeve 43. Surface roughness R of developing sleeve 43
z is 6 μm, and the magnet roll 44 has magnets of five poles arranged along the peripheral surface. The magnet forms a magnetic pattern in which S poles and N poles are alternately arranged along the peripheral surface.
2 can be adsorbed on the surface. The developer adsorbed on the surface of the developer carrier 42 by the transport stirring means 45 is regulated by the rotation of the developing sleeve 43 to a uniform thickness when passing through a gap with the developer regulating member 46, and a predetermined amount is maintained. It is transported to the developing area R. The restricting member 46 is formed of a rigid thin plate in which a 0.4 mm thick magnetic stainless steel plate is stuck to a 1.2 mm thick nonmagnetic stainless steel plate with its ends aligned. The distance between the latent image carrier 1 and the regulating member 46 is 0.7 mm.
Is set to A bias voltage Vb of −560 V is applied to the developing sleeve 43 from the DC power supply 47 during development. By applying this voltage, the toner of the two-component developer adheres to the latent image carrier 1 based on the developing potential of 260 V,
The electrostatic latent image is visualized.

Examples of the production of a toner, a carrier and a two-component developer are shown below, where "parts" indicating the composition ratio means "parts by weight". Production of Toner No. 1 (Resin Dispersion A) Polymerizable Composition Styrene 350 parts N-butyl acrylate 42 parts Acrylic acid 8 parts Dodecyl mercaptan 16 parts Carbon tetrabromide 4 parts Surfactant aqueous solution Nonionic surfactant (Nonipol 85 8 parts Anionic surfactant (Neogen SC: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 10 parts Ion-exchanged water 582 parts 420 parts of a styrene solution of the above polymerizable composition was added to 600 parts of a surfactant aqueous solution in a flask. Mix for 10 minutes and disperse,
Emulsified, 50 parts of ion-exchanged water in which 3.5 parts of ammonium persulfate were dissolved was added. Then, the content was heated to 70 ° C. in an oil bath while stirring the content under a nitrogen gas atmosphere, and the emulsion was maintained at the same temperature for 6 hours to continue the emulsion polymerization.
After cooling to room temperature, a resin dispersion A was prepared.

The obtained styrene-n-butyl acrylate-
For the acrylic acid copolymer, use a particle size analyzer (LA-70
0: manufactured by Horiba, Ltd.)
The volume average particle size (hereinafter simply referred to as the average particle size) is 130 n
m. Further, in order to measure the Mw and Tg of the copolymer, a part of the resin dispersion A was fractionated,
The mixture was allowed to stand on an oven maintained at 0 ° C. to remove unreacted polymerization components, dodecyl mercaptan, and water in the polymerizable composition. The solid content of the copolymer obtained by evaporating the liquid component was measured by gel permeation chromatography (HLC-8120GPC: manufactured by Tosoh Corporation) to find that the copolymer had a Mw of 21,000 and a Tg measuring instrument. (DSC-50: manufactured by Shimadzu Corporation)
The Tg was 56 ° C. in minutes. (Pigment dispersion liquid A) Phthalocyanine pigment (PV Fast Blue) 60 parts Anionic surfactant (Ionnet D-2: manufactured by Sanyo Chemical Co., Ltd.) 2 parts Ion-exchanged water 300 parts Dispersing device for the above composition (Ultra Turrax T50:
IKA Co., Ltd.) and the dispersed particles have an average particle size of 1
A 60 nm pigment dispersion A was prepared.

Resin Dispersion A 240 parts Pigment Dispersion A 40 parts Cationic surfactant (Sanisol B50: manufactured by Kao Corporation) 5 parts Ion-exchanged water 300 parts Next, the above composition is charged into a round stainless steel flask. In the flask, the dispersion treatment was carried out by the above dispersing apparatus. The obtained dispersion was heated to 47 ° C. in an oil bath with stirring, and kept at the same temperature for 2.5 hours. At this time, when the particles in the dispersion were observed with an optical microscope, it was confirmed that aggregated particles of about 6.9 μm had been formed. Next, 6 parts of the above surfactant (Neogen SC) was additionally added, the mixture was heated to 94 ° C. with stirring, and kept at the same temperature for 5 hours. Thereafter, the dispersion was cooled to room temperature at a rate of 10 ° C./min, and the solid content was filtered, washed with ion-exchanged water, and then dried in a vacuum dryer at 40 ° C. for 10 hours. About the obtained cyan toner, the particle diameter was measured by the particle diameter measuring device.
It was 7.0 μm, and the shape factor Ml calculated according to the above-mentioned measuring method was 133.

Production of Toner No. 2 (Resin Dispersion B) Polymerizable composition styrene 340 parts n-butyl acrylate 48 parts acrylic acid 12 parts dodecylmercaptan 13 parts carbon tetrabromide 4 parts A resin dispersion B was prepared in the same manner as in the preparation of the resin dispersion A except that the substitution was carried out. The average particle size of the obtained copolymer particles is 150 nm, and Mw is 26,000.
And the Tg was 58 ° C. Next, the resin dispersion B and the pigment dispersion A were mixed at the same ratio as that of the toner No. 1, heated to 48 ° C. in the same manner as described above, and kept at the same temperature for 1.5 hours. And 94 ° C. after additional addition of surfactant
A cyan toner was produced in the same manner as in the production of Toner No. 1 except that the holding time was changed to 7 hours. This toner No2
Was 6.3 μm, and Ml was 126.

Preparation of Toner No. 3 Toner No. 3 except that the holding time at 94 ° C. was 5 hours.
A cyan toner was produced in the same manner as in the production of No. 2. The average particle size of this toner No. 3 is 6.4 μm, and Ml is 13
It was 3. Production of Toner No. 4 Resin Dispersion B and Pigment Dispersion A in the Same Ratio as Toner No. 1
, And the holding time at 48 ° C was 40 minutes.
A cyan toner was produced in the same manner as in the production of Toner No. 2 except that the holding time at 4.5 hours was 4.5 hours. This toner
The average particle size of No4 was 5.3 μm, and Ml was 134. Production of Toner No. 5 (Pigment Dispersion B) Carbon Black (Mogal L: manufactured by Cabot) 50 parts Nonionic surfactant (NS-220: manufactured by NOF Corporation) 3 parts Ion-exchanged water 400 parts A dispersion treatment was performed by a dispersion device to prepare a pigment dispersion B having an average particle size of 250 nm. Next, the toner No.
Production of toner No. 2 except that the resin dispersion B and the pigment dispersion B were mixed at the same ratio as in Example 1, and the holding time at 48 ° C. was 2 hours and the holding time at 94 ° C. was 3.5 hours. A black toner was produced in the same manner as described above. The average particle size of this toner No. 5 was 6.6 μm, and Ml was 138.

Preparation of Toner No. 6 (Resin Dispersion C) Polymerizable composition 320 parts of styrene 60 parts of n-butyl acrylate 20 parts of acrylic acid 10 parts of dodecylmercaptan 10 parts of carbon tetrabromide 4 parts A resin dispersion C was prepared in the same manner as in the preparation of the resin dispersion A except that the substitution was carried out. The average particle size of the obtained copolymer particles is 150 nm, and Mw is 30,000.
And the Tg was 58 ° C. Next, the resin dispersion C and the pigment dispersion A were mixed at the same ratio as that of the toner No. 1, heated to 50 ° C. in the same manner as described above, and kept at the same temperature for 2.5 hours. Then, after additional addition of a surfactant, 92 ° C.
And kept at the same temperature for 4 hours.
A cyan toner was produced in the same manner as in the production of No. 1. The average particle size of this toner No. 6 is 7.0 μm, and Ml is 140
Met. Production of Toner No. 7 Resin Dispersion C and Pigment Dispersion B at the Same Ratio as Toner No. 1
And the holding time at 50 ° C. was 1.5 hours.
Except that the holding time at 3.5 ° C. was 3.5 hours.
A black toner was manufactured in the same manner as in the above. The average particle size of this toner No. 7 is 6.3 μm, and Ml is 144
Met.

Production of Toner No. 8 Resin dispersion A and pigment dispersion A at the same ratio as toner No. 1.
And a cyan toner was produced in the same manner as in the production of toner No. 1 except that the holding time at 47 ° C. was 2 hours and the holding time at 94 ° C. was 3 hours. The average particle size of this toner No. 8 was 6.7 μm, and Ml was 138. Production of Toner No. 9 Resin Dispersion B and Pigment Dispersion B at the Same Ratio as Toner No. 1
Was added, and the mixture was heated to 92 ° C. after addition of a surfactant, and kept at the same temperature for 3.5 hours.
A black toner was manufactured in the same manner as in the above. The average particle size of this toner No. 9 is 6.7 μm, and Ml is 142
Met. Production of Toner No. 10 Resin dispersion C and pigment dispersion A at the same ratio as toner No. 1
Except that the holding time at 92 ° C. was 3 hours.
A cyan toner was produced in the same manner as in the production of Toner No. 7. The average particle size of this toner No. 10 is 6.4 μm,
Ml was 149.

Production of Toner No. 11 Resin dispersion A and pigment dispersion A at the same ratio as toner No. 1.
Except that the holding time at 94 ° C. was 8 hours.
A cyan toner was produced in the same manner as in the production of Toner No. 1. The average particle size of this toner No. 11 is 7.0 μm,
Ml was 119. Production of Toner No. 12 Resin Dispersion B and Pigment Dispersion A in the Same Ratio as Toner No. 1
Except that the holding time at 94 ° C. was 6 hours.
A cyan toner was produced in the same manner as in the production of Toner No. 2. The average particle size of this toner No. 12 is 6.1 μm,
Ml was 127.

Production of carrier 100 parts of ferrite particles having an average particle diameter of 35 μm, molecular weight 9
1 part of 5,000 methacrylate resin and 500 parts of toluene
The mixture was placed in a pressure kneader and mixed at room temperature for 15 minutes, and then heated to 70 ° C. while mixing under reduced pressure to distill off the toluene solvent. After cooling, the solid was sieved with a 105 μm sieve to obtain methacrylate resin-coated ferrite particles having an average particle size of 35 μm. Production of Two-Component Developer One part of colloidal silica (R972, manufactured by Nippon Aerosil Co., Ltd.) was added to 100 parts of each of toners No. 1 to No. 12, and mixed with a Henschel mixer. Each toner containing silica as an external additive and the above carrier were mixed at a toner concentration of 8% by weight to produce two-component developers No. 1 to No. 12, respectively.

Evaluation of Toner Two-component developers No. 1 to No.
The developing sleeve was rotated for 5 hours at a peripheral speed of 520 mm / sec without replenishing toner. During this time, the transport amount of the developer after passing through the regulating member is 350 to 400.
g / m ^{2. In} order to investigate the change in the particle size of the toner,
It was run idle without actually developing. Then, the particle size distribution of the toner before the rotation of the developing sleeve and after 5 hours of rotation, that is, the weight average particle diameter d ₅₀ (μm) and the ratio (%) of the particles (number) having a particle diameter of 3 μm or less were measured. Table 1 shows the measurement results. In Table 1, the “initial” column shows the particle size distribution before the rotation of the developing sleeve, and the “〇” in the “disintegration” column shows that the toner has not collapsed, and the x mark shows that the toner has collapsed.

[0034]

[Table 1]

Since the toners of the developers No. 1 to No. 7 according to the examples are not disintegrated, d ₅₀ and the particle diameter of 3 μm in the initial stage and after 5 hours are used.
The following ratios hardly changed. On the other hand, the developer No8~No10 according to the comparative example since the toner has collapsed, greatly reduced d _50, the ratio of particle size 3μm or less greatly increased. Further, when the state of the toner with respect to the developer No. 1 was observed with an SEM, the toner No. 1 showed a large change in the state of attachment of the external additive between the initial stage and 5 hours later, but no change in the toner shape. On the other hand, developer No. 8
When toner No. 8 was similarly observed, many particles of 2 to 3 μm were observed after 5 hours in toner No. 8, and the toner was separated at the fusion portion at the time of production. Next, toner Nos.
FIG. 5 shows the relationship between the weight average molecular weight Mw (× 10 ⁻³ ) and the shape factor Ml. From the evaluation results of the toner, after the developing sleeve has been rotated for 5 hours, Ml = Mw / 1000 +
Toners No. 1 to No. 7 below the straight line represented by 115
(〇 mark) is not collapsed, and toner Nos. 8 to 10 (x mark) above the straight line are collapsed. That is, in order for the toner not to collapse due to mechanical stress,
It is understood that the condition represented by (2) should be satisfied.

Evaluation of Cleaning Property In the cleaning device of the image forming apparatus, 2.0 was used.
mm thick silicone rubber blade was pressed against the tangential direction of the photosensitive drum at an angle of 25 °, and the linear pressure was reduced to 13 °.
N / m was set. Developer No1, No2, No5, No11,
For No. 12, a 50 mm × 50 mm patch was developed from the developing device onto the organic photoreceptor at a development amount of 4.5 g / m ² ,
It was cleaned as it was. Then, the weight of the toner remaining on the photoreceptor after cleaning was measured to determine the cleaning efficiency, and 99.5% or more was regarded as an allowable value. Table 1 shows the evaluation results. In the cleaning properties in Table 1, the mark “〇” indicates that the cleaning efficiency is 99.5% or more, and the mark “X” indicates that the cleaning efficiency is less than 99.5%.
As is clear from Table 1, toners No. 1, No. 5, and No. 12 having a shape factor Ml of 127 or more have good cleaning properties. On the other hand, toners No. 2 and No. 11 having Ml of 126 or less did not reach the allowable value, and the cleaning property was poor. In other words, among the toners having excellent shape retention, a toner having an irregular shape with Ml of 127 or more is more suitable for cleaning than a toner having a shape close to a true sphere.

[0037]

According to the image forming apparatus of the present invention, the upper limit of the shape factor Ml of the toner is defined in relation to the weight average molecular weight Mw of the binder resin, and the condition represented by the above formula (2) is satisfied. If it satisfies, the toner will not be destroyed by mechanical stress in the developing device even during long-term use. Further, when the toner cleaning means is of a blade type, by setting the lower limit value of the shape factor Ml to a predetermined value, it is possible to prevent defective cleaning.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an image forming apparatus of the present invention.

FIG. 2 is a schematic diagram of a developing device in the image forming apparatus.

FIG. 3 is an explanatory diagram of an image forming process of the image forming apparatus, and shows a surface potential of an electrostatic latent image carrier.

FIG. 4 is a schematic view of an image forming apparatus showing one embodiment of the present invention.

FIG. 5 is a graph showing a relationship between a weight average molecular weight Mw and a shape factor Ml.

[Explanation of symbols]

U: image forming apparatus, P: recording paper, R: developing area, 1: electrostatic latent image carrier, 4: developing device, 42: developer carrier, 46
... developer regulating member, 9 ... cleaning device, 9a ... cleaning blade.

Claims (4)

[Claims] An amount of the developer carried on the developer carrier is regulated by a developer regulating member, and a predetermined amount of the developer is carried to a developing area facing the electrostatic latent image carrier. A developing device is provided that visualizes an electrostatic latent image on the surface of the electrostatic latent image carrier with a developer by a potential difference between the electrostatic latent image carrier and the developer carrier. When the toner is formed of fine particles produced by an emulsion polymerization method in which a binder resin and a colorant are united, and the shape factor Ml of the toner is represented by the formula (1), the shape factor Ml is represented by the following formula (2). An image forming apparatus characterized by satisfying the following conditions. Ml = (π · dmax ² / 4A) × 100 (1) Ml ≦ Mw / 1000 + 115 (2) where dmax: maximum diameter of toner A: cross-sectional area of toner Mw: weight average molecular weight of binder resin 2. The image forming apparatus according to claim 1, wherein the developer is a two-component developer including a toner and a carrier. 3. The weight average molecular weight Mw is from 20,000 to 30,0.
The image forming apparatus according to claim 1, wherein the number is in the range of 00. 4. A cleaning device for removing a residual toner on the electrostatic latent image carrier after transferring the toner image on the electrostatic latent image carrier onto a recording sheet with a blade, and further comprising a shape factor Ml of the toner. The image forming apparatus according to claim 1, wherein the number is 127 or more.