JP2010060979A - Toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide toner that keeps the electric charge quantity thereof stably even when used for printing a number of sheets of a document with low printing rate and with which a high-quality printed image having no deteriorated image density and no fogging can be continuously obtained. <P>SOLUTION: The toner has an undulation formed of mountains and valleys of specific sizes on the surface of a toner base particle comprising a binder resin, a coloring agent and a releasing agent and traps an external additive in each valley. An average difference in height of the undulation is 30-200 nm and the average size of the undulation is 20-300 nm and the undulation accounts for 20-100%, on the average, of the surface of a toner particle. Two external additives different at least in number-average primary particle size are used as the external additive. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a toner used for electrophotographic image formation.

  In recent years, image forming apparatuses that perform large-scale printing at high speed have been developed. It is desired that this image forming apparatus can continuously obtain high-quality print images with energy saving.

  In order to continuously obtain energy-saving and high-quality print images with a high-speed image forming apparatus, the toner Tg is lowered and toner having a small particle diameter is used. When the Tg of the toner is lowered, the surface of the toner particles becomes soft, and when a large amount of printing (printing a large number of sheets) is performed, the external additive fixed on the surface of the toner particles is buried in the toner particles, and a stable charge amount is maintained. It was difficult to continuously obtain high-quality prints.

  In order to continuously obtain high-quality prints, a device for external additives has been disclosed.

  Further, in order to obtain low-temperature fixing and continuously obtaining high-quality prints, studies are being made to devise a toner particle structure (for example, a core-shell structure).

  Further, full-color images are currently being developed, and accordingly, it is desired to support a wide variety of print patterns. For example, in offices, there is a higher image need for a small amount of color in a black character image than in a photographic image using all colors. In such a case, a large amount of toner is consumed at a high printing rate for a certain color, whereas a color with a low printing rate is stirred for a long time in the developing machine with a low consumption of toner. Deterioration of the developer due to burying of the external additive occurs. In particular, low Tg toners tend to cause external additives to be buried due to the softness of the resin, resulting in toner aggregation, weakly charged toner, and image defects such as image roughness and fogging of halftone images. cause.

  As means for preventing toner aggregation, techniques using the addition of a large-diameter external additive and a toner having a core / shell structure with a high Tg shell are disclosed (for example, see Patent Document 1).

In addition, as a means for preventing the external additive from being buried, a large-diameter external additive is provided with a spacer function by using a plurality of types of inorganic particles having different particle sizes (for example, a large-diameter external additive and a small-diameter external additive). A technique for stabilizing the developability and transferability is disclosed (for example, see Patent Document 2).
JP 2001-175025 A JP 2006-39023 A

  However, even when the toner disclosed above is used, toner particles are used under conditions for printing a document having various printing rates with a high-speed image forming apparatus, particularly under printing conditions where the printing rate is low and toner stays in the developing machine for a long time. As a result, an external pressure is applied, and the external additive is buried in the toner base particles or detached from the surface of the toner base particles, resulting in a phenomenon that the chargeability of the toner cannot be kept constant. As a result, there has been a problem that the image density is lowered or fogging occurs.

  The present invention can maintain a stable charge amount even when printing a large number of documents (for example, 300,000 sheets or more) with a low printing rate (for example, 1% printing rate), and there is no reduction in image density and occurrence of fogging. Another object of the present invention is to provide a toner capable of continuously obtaining a high-quality print image.

  The present invention is achieved by adopting the following configuration.

1. In the toner in which the surface of the toner base particle having a binder resin, a colorant, and a release agent has undulations formed from peaks and valleys of a specific size, and the external additive is captured in the valley portions.
The difference in level of the swell is 30 to 200 nm on average, the size of swell is 20 to 300 nm on average, and the ratio of swell is 20 to 100% on the average of the toner particle surface,
A toner comprising at least two types of external additives having different number average primary particle sizes as the external additives.

  2. 2. The toner according to 1, wherein the external additive has a number average primary particle size of 10 to 60 nm and a number average primary particle size of 80 nm to 1 μm.

  The toner of the present invention can maintain a stable charge amount even when printing a large number of documents (for example, 300,000 sheets or more) with a low printing rate (for example, a printing rate of 1%), a decrease in image density, and occurrence of fogging. And has an excellent effect of continuously obtaining a high-quality printed image.

  With the reduction in power consumption of high-speed image forming apparatuses, development of toner that can be fixed at low temperature is underway. When using this low-temperature fixable toner to print a large number of documents with a low printing rate, the external additive fixed on the surface of the toner particles is reduced by being embedded in or detached from the particles, and stable charging is achieved. The amount could not be maintained, resulting in a decrease in image density and fogging.

  The present inventors have examined toners that can stably maintain the charge amount and can continuously obtain a high-quality printed image even if a large number of low-printing-rate originals are printed using toner that can be fixed at low temperature. went.

  As a result of various studies, a toner formed by mixing two or more types of external additives having a specific particle size with a toner base particle having a specific number of undulations on the surface of the toner particle has a low printing rate. It has been found that a stable charge amount can be secured even when a large number of originals are printed.

  This is because the external additive trapped in the undulation valley formed on the surface of the toner particles is ejected from the undulation valley of the toner particles as the printing progresses, and the extruded external additive is applied to the toner particle surface. It is presumed that this was achieved by replenishing and fixing to the particle surface of the toner, and a fixed amount of external additive always being fixed to the toner particle surface.

  The difference in level of waviness on the surface of the toner base particles is 30 to 200 nm on average, preferably 40 to 170 nm, the size of the waviness is on average 20 to 300 nm, preferably 50 to 200 nm, and the proportion of waviness is 20 on average on the surface of the toner base particles. -100%, preferably 30-100%.

  Using the toner of the above shape, it is possible to capture the amount of external additive necessary to stably maintain the charge amount even when a large number of originals with a low printing rate are printed. The shape does not change.

  The toner of the present invention preferably has a glass transition point of 20 to 50 ° C., more preferably 30 to 45 ° C., in order to enable low-temperature fixing using a high-speed image forming apparatus.

  The glass transition temperature of the toner can be measured using “DSC-7 differential scanning calorimeter” (manufactured by PerkinElmer) or “TAC7 / DX thermal analyzer controller” (manufactured by PerkinElmer).

The median diameter (D ₅₀ ) based on the number of toners of the present invention is preferably 3 to 8 μm. When a toner having a median diameter (D ₅₀ ) in this range is in this range, high image quality (for example, high resolution, reproducibility of a halftone image) is obtained.

Median diameter _{(D 50)} in the number reference of the toner, the Coulter Multisizer 3 (manufactured by Beckman Coulter, Inc.), using the device connected to the computer system (manufactured by Beckman Coulter, Inc.) equipped with software for data processing "Software V3.51" Measured and calculated.

  The toner of the present invention has two or more external additives having different particle diameters, and has an external additive having a small diameter of at least a number average primary particle diameter of 10 to 60 nm (hereinafter also referred to as a small diameter external additive). The number average primary particle size is preferably 80 nm to 1 μm and a large-diameter external additive (hereinafter also referred to as a small-diameter external additive).

  By adding a small-diameter external additive, good charging characteristics of the developer can be obtained.

  When the large-diameter external additive is added, the large-diameter external additive is captured in a form that covers the small-diameter external additive at the bottom of the undulation formed on the toner particle surface, and the small-diameter external additive is added to the lower part of the undulation. Captured state. When the large-diameter external additive covering the small-diameter external additive is removed together with the printing, the small-diameter external additive captured in the lower part of the undulation is ejected and replenished to the toner particle surface.

  As described above, since the small-diameter external additive is replenished on the surface of the toner particles and a certain amount of the small-diameter external additive is fixed, it is possible to keep the charge amount constant.

  In the present invention, the toner base has a binder resin, a colorant and a release agent, the toner base particles have a toner base, and the toner particles have toner base particles and an external additive. The toner is a general term for toner particles.

  Hereinafter, the present invention will be described in detail.

  FIG. 1 is a schematic view showing an example of toner base particles having undulations on the surface.

  In FIG. 1, 2 is a toner base particle, 3 is a toner base, 4 is a height difference of waviness, 5 is the size (interval) of waviness, 6 is a wavy portion, 7 is a peak portion (high portion), and 8 is a trough. The part (low part) is shown.

  As shown in the figure, the toner of the present invention has undulations on the surface of the toner base particles (2), and the external additive added later has a shape that is easily captured by the valleys of the undulations. is doing.

  In the present invention, the undulation difference (4) is the average value of the difference between the undulation peaks (high) and the valley (low), and the undulation size (5) is the undulation peaks and peaks. The mean value of the distances (intervals) is the swell portion (6) is the portion having swells.

  The ratio of waviness refers to the ratio (area ratio) of waviness (6) in the toner particle surface that can be observed from one direction.

  FIG. 2 is an enlarged cross-sectional view of the toner particles showing an example of the behavior of the external additive on the surface of the toner particles when printing is performed.

  In FIG. 2, 1 denotes toner particles, 3 denotes a toner base, 7 denotes a peak portion (high portion), 8 denotes a valley portion (low portion), 9 denotes a large-diameter external additive, and 10 denotes a small-diameter external additive. .

  FIG. 2A is an enlarged cross-sectional view of the toner particles produced by the external additive treatment, and shows a state where the small diameter and large diameter external additives are captured on the surface of the toner base.

  In FIG. 2 (b), the large-diameter external additive (9) is removed by advancing printing, and the small-diameter external additive (10) captured in the undulation valleys is ejected, and the toner base (3) is removed. It is the schematic which shows the state with which the surface was replenished.

《Swelling numerical measurement method》
The level difference of the swell formed on the surface of the toner particles, the size of the swell, and the ratio of the swell can be determined by measuring by the method described in paragraphs 0034 to 0036 of JP-A-2003-121333.

  Specifically, it is an average value of values obtained by measuring the level difference of waviness, the size of waviness, and the ratio of waviness existing on the observed surface of 300 toner particles.

  A method for measuring the numerical value of waviness using a scanning probe microscope (SPM) will be described.

  A scanning probe microscope is a general term for microscopes that detect interaction force (tunnel current, atomic force, electromagnetic force, etc.) acting between a probe and a sample, and perform surface shape observation and physical property analysis of a minute region.

  For example, the surface shape can be measured by contact AFM or dynamic force mode using a scanning probe microscope system SPI3800N and a multifunctional unit SPA400 manufactured by Seiko Instruments Inc.

  A specific measurement method will be described.

  Cut the Matsunami micro slide glass (product number s1226 thickness 1.0mm) into 10mm x 10mm, and mix the same amount of Nichiban Epoxy strong adhesive Araldite standard main component and polyamidoamine curing agent on the surface. Apply as thin as possible. After leaving at 25 ° C. for 5 hours, digital toner (black) for digital copying machine Sitos series manufactured by Konica Minolta was sprayed evenly so that the particles were dispersed, and cured at 25 ° C. for 7 hours. The average particle size of the digital toner used was 7 μm. By fixing the adhesive, about 1/2 of the particle size of each particle of the digital toner was exposed on the adhesive on average.

  This was placed on a sample stage and measured by a dynamic force mode (DFM) of a scanning probe microscope system SPI3800N manufactured by Seiko Instruments Inc. and a multifunctional unit SPA400. The cantilever was SI-DF20 (manufactured by Seiko Instruments Inc., made of silicone, spring constant of about 20 N / m, resonance frequency 135 kHz), and the shape of the scanner was measured using FS-100N.

  The scanning area was 2 μm × 2 μm, and the scanning speed was 1 Hz.

<< Preparation of toner base particles having undulations >>
In the preparation of the toner described later, the toner base particles having waviness can be prepared by controlling the circularity adjusting conditions when the toner base particles are prepared by a polymerization method. Specifically, when the circularity is adjusted (aggregation / fusion process) at high speed, bubbles of micron order are generated by cavitation. It is speculated that the bubbles are adsorbed on the surface of the particles being agglomerated and fused, and the degree of circularity adjustment proceeds while the bubbles are adsorbed. After a certain period of time, the bubbles are removed and the bubbles are wavy.

  Specifically, a procedure for producing toner base particles having waviness will be described.

At the stage of the aggregation / fusion process (4) below for producing toner base particles,
1. 1. Stirring is performed at a high speed (for example, 100 rpm) while being heated to a temperature higher than the glass transition point of the resin forming the toner base particles. 2. When stirring at high speed, bubbles of micron order are generated by cavitation. The bubbles adhere to the surface of the particles being agglomerated and fused, and are taken into the particle surface. 4. Then, in the process of cooling to the glass transition point of the resin forming the toner base particles, the incorporated bubbles pop out from the particle surface by cooling. 5. Traces of bubbles popping out are undulating. Thereafter, the particles are filtered and washed to prepare toner base particles.

  The difference in the level of waviness, the size of waviness, and the proportion of waviness are the Tg of the toner base particles, the temperature when adjusting the circularity of the toner base particles, the number of stirring (speed) for generating cavitation, and the circularity adjustment. It can be adjusted according to the cooling rate from the temperature of the hour to room temperature.

<External additive>
The toner of the present invention contains two or more external additives having different particle diameters. Specifically, it is preferable that the number average primary particle size is 10 to 60 nm and the small diameter external additive and the number average primary particle size is 80 nm to 1 μm and the large diameter external additive is contained.

  As the small-diameter external additive, known inorganic fine particles can be mentioned. Examples of the large-diameter external additive include known organic fine particles and inorganic fine particles.

  By the external additive treatment, the small-diameter external additive is easily captured at the lower part of the swell, and the large-diameter external additive is easily fixed so as to cover the small-diameter external additive at the bottom of the swell.

  The small-diameter external additive trapped in the lower part of the undulation is removed when the covered large-diameter external additive is removed, and is replenished and fixed to the surface of the toner base.

  The number average primary particle size of the small and large external additives can be obtained by photographing the dispersed external additive with an electron microscope and analyzing the photographed images.

  Next, toner production will be described.

<Production of toner>
The toner of the present invention is obtained by mixing at least two kinds of external additives having different particle diameters with toner base particles containing a binder resin, a colorant and a release agent.

  The method for producing the toner is not particularly limited, but a method using an emulsion association method is preferably used. In particular, a method is preferred in which the toner particles are produced by associating (aggregating and fusing) resin particles having a multi-stage polymerization structure by emulsion polymerization of the miniemulsion polymerized particles, and an external additive is added to the toner mother particles. .

Hereinafter, a method for producing a toner by the miniemulsion polymerization association method will be described as an example and described in detail. In this toner manufacturing method, the toner is manufactured through the following steps.
(1) Dissolution / dispersion step of dissolving or dispersing the release agent in the radical polymerizable monomer (2) The polymerizable monomer solution in which the release agent is dissolved / dispersed is formed into droplets in a solution medium, and the mini Polymerization step of preparing resin particle dispersion by emulsion polymerization (3) Colorant dispersion step of dispersing colorant in solution medium (4) Associating particles by associating resin particles and colorant particles in solution medium Aggregation / fusion step (5) Aging step for forming toner base particles by the method described in “Preparation of toner base particles having waviness” (6) Cooling step (7) for cooling the dispersion of toner base particles A step of solid-liquid separation of the toner base particles from the cooled dispersion of the toner base particles, and removing a surfactant and the like from the toner base (8) A drying step of drying the toner base particles that have been subjected to the cleaning treatment ( 9) Dried tona The base particles, the following step of adding an external additive, each step is explained.

(1) [Dissolution / dispersion step]
This step is a step of preparing a radical polymerizable monomer solution of the release agent by dissolving or dispersing the release agent in the radical polymerizable monomer.

(2) [Polymerization process]
In a preferred example of this polymerization step, a radical polymerizable monomer solution in which the release agent is dissolved or dispersed is added to a solution medium containing a surfactant, and mechanical energy is applied to form droplets. Then, the polymerization reaction is advanced in the droplets by radicals from the water-soluble radical polymerization initiator. Note that resin particles may be added as core particles to the solution medium.

  By this polymerization step, resin particles containing a release agent and a binder resin are obtained. The resin particles may be colored particles or non-colored particles. The colored resin particles can be obtained by polymerizing a monomer composition containing a colorant. In the case where uncolored resin particles are used, in the aggregation process described later, a dispersion of colorant particles is added to the dispersion of resin particles to aggregate the resin particles and the colorant particles. It can be a base particle.

(3) [Dispersing step of colorant particles]
In this step, the colorant particles are added to a solution medium containing a surfactant, and the colorant particles are dispersed in the solution medium using a dispersing device.

  The dispersing device used in the step of dispersing the colorant particles is not particularly limited, and a known device can be used. Preferred dispersing devices include pressure dispersers such as an ultrasonic disperser, a mechanical homogenizer, a manton gourin, and a pressure homogenizer, and medium dispersers such as a sand grinder, a Getzman mill, and a diamond fine mill.

  The colorant may be surface-modified. In the surface modification method of the colorant, the colorant particles are dispersed in a solvent, the surface modifier is added to the dispersion, and the system is reacted by raising the temperature. After completion of the reaction, the colorant particles are filtered off, washed and filtered with the same solvent, and then dried to obtain a colorant treated with the surface modifier.

  In the toner manufacturing process, the average dispersion diameter of the colorant dispersed in the solution medium is preferably 2 to 300 nm, and more preferably 2 to 200 nm. The average dispersion diameter of the colorant can be controlled by the amount of the surfactant, the number of rotations of the dispersion device, the dispersion time, and the like.

(4) [Aggregation / fusion process]
The aggregation step is a step of forming toner base particles using resin particles and colorant particles obtained in the polymerization step. In the aggregation step, resin particles and colorant particles can be aggregated together with release agent particles, internal additive particles such as charge control agents, and the like.

  A preferred aggregating method is to add a salting-out agent composed of an alkali metal salt, an alkaline earth metal salt, or the like as an aggregating agent having a critical aggregation concentration or more in water in which resin particles and colorant particles are present, This is a step of agglomerating by heating to a temperature above the glass transition point of the resin particles and above the melting peak temperature (° C.) of the release agent.

(5) [Aging process]
The aging step is a step of producing toner base particles having undulations by the method described in “Preparation of toner base particles having undulations”.

(6) [Cooling process]
This step is a step of cooling (rapid cooling) the dispersion of toner base particles. As a cooling treatment condition, cooling is performed at a cooling rate of 1 to 20 ° C./min. The cooling treatment method is not particularly limited, and examples thereof include a method of cooling by introducing a refrigerant from the outside of the reaction vessel, and a method of cooling by directly introducing cold water into the reaction system.

(7) [Washing process]
In the solid-liquid separation / washing step, the solid-liquid separation process for solid-liquid separation of the toner base particles from the dispersion of the toner base particles cooled to a predetermined temperature in the above-described step, and the solid-liquid separated toner cake (wet A cleaning process is performed to remove deposits such as surfactants and salting-out agents and the alkali agent used in the aging process from the aggregate of toner base particles in a state of cake.

  In the washing treatment, the filtrate is washed with water until the electric conductivity of the filtrate reaches 10 μS / cm. Examples of the filtration method include a centrifugal separation method, a vacuum filtration method using Nutsche and the like, and a filtration method using a filter press and the like, and are not particularly limited.

(8) [Drying process]
In this step, the washed toner cake is dried to obtain dried toner base particles. Examples of dryers used in this process include spray dryers, vacuum freeze dryers, vacuum dryers, etc., stationary shelf dryers, mobile shelf dryers, fluidized bed dryers, rotary dryers It is preferable to use a stirring dryer or the like. The moisture content of the dried toner base particles is preferably 5% by mass or less, and more preferably 2% by mass or less. In addition, when the toner base particles that have been dried are aggregated by weak interparticle attraction, the aggregate may be crushed. Here, as the crushing treatment apparatus, a mechanical crushing apparatus such as a jet mill, a Henschel mixer, a coffee mill, or a food processor can be used.

(9) [Step of mixing external additive into toner base particles]
This step is a step of preparing a toner by mixing two or more kinds of external additives with the toner base particles. As an external additive mixing device, a mechanical mixing device such as a Henschel mixer or a coffee mill can be used.

  The two or more types of external additives used in the present invention may be mixed by adding two or more types of external additives to the toner base particles at the same time or separately. In order to obtain the spacer effect by the external additive, it is preferable that only the large external additive is mixed and fixed with the toner base particles first, and then the small particle is mixed.

  As conditions for the mixing apparatus, the peripheral speed is preferably 10 to 50 m / sec, and the peripheral speed of the large-diameter external additive treatment is preferably faster than the peripheral speed of the small-diameter external additive treatment. The treatment time is preferably 3 to 40 minutes, but the treatment time is preferably set longer because the smaller the external additive, the easier it is for the external additive particles to aggregate.

  Next, members constituting the toner will be described.

<Components of toner>
(Binder resin)
As the polymerizable monomer constituting the binder resin, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-chlorostyrene, 3,4-dichloro are used. Styrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn -Styrene or styrene derivatives such as decylstyrene, pn-dodecylstyrene, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-methacrylate Octyl, 2-ethylhexyl methacrylate, stearyl methacrylate Methacrylic acid ester derivatives such as lauryl methacrylate, phenyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, acrylic Acrylates such as isobutyl acid, n-octyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, phenyl acrylate, olefins such as ethylene, propylene, isobutylene, vinyl chloride, vinylidene chloride, Halogenated vinyls such as vinyl bromide, vinyl fluoride and vinylidene fluoride, vinyl esters such as vinyl propionate, vinyl acetate and vinyl benzoate, vinyl methyl ether, vinyl ethyl ether Vinyl ethers such as ether, vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone, vinyl hexyl ketone, N-vinyl compounds such as N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrolidone, vinyl naphthalene, vinyl pyridine, etc. Examples include vinyl compounds, acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide. These vinyl monomers can be used alone or in combination.

  Further, it is more preferable to use a combination of monomers having an ionic dissociation group as the polymerizable monomer constituting the resin. For example, it has a substituent such as a carboxyl group, a sulfonic acid group, a phosphoric acid group as a constituent group of the monomer, specifically, acrylic acid, methacrylic acid, maleic acid, itaconic acid, cinnamic acid, fumar Acid, maleic acid monoalkyl ester, itaconic acid monoalkyl ester, styrene sulfonic acid, allyl sulfosuccinic acid, 2-acrylamido-2-methylpropane sulfonic acid, acid phosphooxyethyl methacrylate, 3-chloro-2-acid phosphooxy And propyl methacrylate.

  Furthermore, multifunctional such as divinylbenzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol diacrylate, neopentyl glycol dimethacrylate, neopentyl glycol diacrylate, etc. It is also possible to use a crosslinkable resin by using a functional vinyl.

  These polymerizable monomers can be polymerized using a radical polymerization initiator. In this case, an oil-soluble polymerization initiator can be used in the suspension polymerization method. Examples of the oil-soluble polymerization initiator include 2,2′-azobis- (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexane-1-carboxyl). Nitriles), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, azo- or diazo-based polymerization initiators such as azobisisobutyronitrile, benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate , Cumene hydroperoxide, t-butyl hydroperoxide, di-t-butyl peroxide, dicumyl peroxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide, 2,2-bis- (4,4- t-butylperoxycyclohexyl) propane, tris- Peroxide polymerization initiator or a peroxide such as t- butylperoxy) triazine and the like polymeric initiator having a side chain.

  Moreover, when using an emulsion polymerization method, a water-soluble radical polymerization initiator can be used. Examples of the water-soluble polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate, azobisaminodipropane acetate, azobiscyanovaleric acid and its salts, hydrogen peroxide and the like.

(Chain transfer agent)
In order to adjust the molecular weight of the resin, a commonly used chain transfer agent can be used. The chain transfer agent used is not particularly limited. For example, mercaptans such as n-octyl mercaptan, n-decyl mercaptan, tert-dodecyl mercaptan, and mercaptopropionate esters such as n-octyl-3-mercaptopropionate. , Terpinolene, carbon tetrabromide and α-methylstyrene dimer are used.

(Coloring agent)
As the colorant, a colorant of each color can be used.

  Examples of the black colorant include carbon black such as furnace black, channel black, acetylene black, thermal black, and lamp black, and magnetic powder such as magnetite and ferrite.

  Examples of the colorant for magenta or red include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48; 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. And CI Pigment Red 222.

  Examples of the colorant for orange or yellow include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. And CI Pigment Yellow 138.

  Examples of the colorant for green or cyan include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15; 2, C.I. I. Pigment blue 15; 3, C.I. I. Pigment blue 15; 4, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. Pigment blue 62, C.I. I. Pigment blue 66, C.I. I. And CI Pigment Green 7.

  These colorants may be used alone or in combination of two or more as required. The addition amount of the colorant is set in the range of 1 to 30% by mass, preferably 2 to 20% by mass with respect to the whole toner.

(Release agent)
A known compound can be used as the release agent used in the present invention.

  As such, for example, polyolefin wax such as polyethylene wax and polypropylene wax, long chain hydrocarbon wax such as paraffin wax and sazol wax, dialkyl ketone wax such as distearyl ketone, carnauba wax, montan wax, Trimethylolpropane tribehenate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecanediol distearate, tristearyl trimellitic acid, distearyl maleate, etc. And amide waxes such as ethylenediamine behenyl amide and trimellitic acid tristearyl amide.

  The amount of the release agent contained in the toner is preferably 1 to 20% by mass and more preferably 3 to 15% by mass with respect to the whole toner.

(Charge control agent)
A charge control agent can be added to the toner according to the present invention as necessary. A known compound can be used as the charge control agent.

  Next, the developer will be described.

<Developer>
The toner of the present invention can be used as a one-component developer or a two-component developer.

  When used as a one-component developer, a non-magnetic one-component developer or a magnetic one-component developer containing about 0.1 μm to 0.5 μm of magnetic particles in the toner can be used. be able to.

  Further, it can be mixed with a carrier and used as a two-component developer. As the carrier, conventionally known magnetic particles such as metals such as iron, ferrite, and magnetite, and alloys of these metals with metals such as aluminum and lead can be used. Ferrite particles are particularly preferable. The particle diameter of the carrier is preferably 20 to 100 μm, and more preferably 25 to 80 μm.

  The particle diameter of the carrier can be typically measured by a laser diffraction type particle size distribution measuring apparatus “HELOS” (manufactured by Sympathetic) equipped with a wet disperser.

  The carrier is preferably a carrier in which magnetic particles are further coated with a resin, or a so-called resin dispersion type carrier in which magnetic particles are dispersed in a resin. The coating resin is not particularly limited, and for example, an olefin resin, a styrene resin, a styrene-acrylic resin, a silicone resin, an ester resin, a fluorine-containing polymer resin, or the like is used. The resin for constituting the resin-dispersed carrier is not particularly limited, and known resins can be used. For example, styrene-acrylic resin, polyester resin, fluorine resin, phenol resin, etc. are used. be able to. Among these, a coat carrier coated with a styrene-acrylic resin is more preferable because it can prevent the external additive from being detached and ensure durability.

  Next, an image forming method and an image forming apparatus using the toner of the present invention will be described.

<Image formation>
FIG. 3 is a cross-sectional configuration diagram illustrating an example of an image forming apparatus using the toner of the present invention.

  An image forming apparatus 1 shown in FIG. 3 is a digital image forming apparatus, and includes an image reading unit A, an image processing unit B, an image forming unit C, and a transfer paper transport unit D as a transfer paper transport unit. Yes.

  The upper part of the image reading unit A is provided with automatic document feeding means for automatically conveying the document. The document placed on the document placing table 11 is separated and conveyed by the document conveying roller 12 at the reading position 13a. The image is read. The document after the document reading is completed is discharged onto the document discharge tray 14 by the document transport roller 12.

  On the other hand, the image of the original when placed on the platen glass 13 is read at a speed v of the first mirror unit 15 including the illumination lamp and the first mirror constituting the scanning optical system, and the V-shaped first image is located. Reading is performed by the movement of the second mirror unit 16 including the two mirrors and the third mirror in the same direction at the speed v / 2.

  The read image is formed on the light receiving surface of the image sensor CCD, which is a line sensor, through the projection lens 17. The line-shaped optical image formed on the image sensor CCD is sequentially photoelectrically converted into an electric signal (luminance signal) and then A / D converted, and the image processing unit B performs processing such as density conversion and filter processing. Then, the image data is temporarily stored in the memory.

  In the image forming unit C, as an image forming unit, a drum-shaped photoconductor 21 as an image carrier, a charging means (charging step) 22 for charging the photoconductor 21 on the outer periphery thereof, and a surface potential of the charged photoconductor. Potential detecting means 220 for detecting the toner, developing means (developing process) 23, transfer conveying belt device 45 as a transferring means (transfer process), cleaning device (cleaning process) 26 for the photosensitive member 21, and light neutralizing means (light slow charge). PCL (precharge lamp) 27 as a process is arranged in the order of operation. Further, on the downstream side of the developing means 23, a reflection density detecting means 222 for measuring the reflection density of the patch image developed on the photosensitive member 21 is provided. As the photosensitive member 21, the photosensitive member according to the present invention is used, and the photosensitive member 21 is driven and rotated in the clockwise direction shown in the drawing.

  After the rotating photosensitive member 21 is uniformly charged by the charging unit 22, an image based on an image signal called from the memory of the image processing unit B by an exposure optical system as an image exposure unit (image exposure step) 30 is used. Exposure is performed. The exposure optical system as the image exposure means 30 as the writing means uses a laser diode (not shown) as a light source, and the optical path is bent by the reflection mirror 32 via the rotating polygon mirror 31, the fθ lens 34, and the cylindrical lens 35, and main scanning is performed. Therefore, image exposure is performed on the photoconductor 21 at the position Ao, and an electrostatic latent image is formed by rotation (sub-scanning) of the photoconductor 21. In an example of this embodiment, the character portion is exposed to form an electrostatic latent image.

  In the image forming apparatus, a semiconductor laser or a light emitting diode can be used as an image exposure light source when an electrostatic latent image is formed on a photoconductor. By using these image exposure light sources, the exposure dot diameter in the writing principal direction is narrowed down to 10 to 80 μm, and digital exposure is performed on the photosensitive member, whereby from 400 dpi (dpi: the number of dots per 2.54 cm) to 2500 dpi. High-resolution electrophotographic images can be obtained.

The exposure dot diameter refers to the length of the exposure beam along the main scanning direction (Ld: measured at the maximum length) in a region where the intensity of the exposure beam is 1 / e ² or more of the peak intensity.

The light beams used have a solid scanner such as the scanning optical system and LED using a semiconductor laser, there is a Gaussian distribution and Lorentz distribution, etc. also the light intensity distribution is in each 1 / e ² or more regions of peak intensity The exposure dot diameter according to the present invention is used.

  The electrostatic latent image on the photoconductor 21 is reversely developed by the developing unit 23, and a visible toner image is formed on the surface of the photoconductor 21. In the image forming method according to the present invention, it is preferable to use a polymerized toner as a developer used in the developing unit. By using a polymer toner having a uniform shape and particle size distribution in combination with the photoreceptor of the present invention, an electrophotographic image with better sharpness can be obtained.

  In the transfer paper transport section D, paper feed units 41 (A), 41 (B), and 41 (C) are provided below the image forming unit as transfer paper storage means for storing transfer paper P of different sizes. Further, a manual paper feeding unit 42 for manually feeding paper is provided on the side, and the transfer paper P selected from any of them is fed along the transport path 40 by the guide roller 43 and fed. The transfer paper P is temporarily stopped by a pair of paper feed registration rollers 44 that correct the inclination and bias of the transfer paper P to be transferred, and then fed again. The transport path 40, the pre-transfer roller 43a, and the paper feed path 46 The toner image on the photosensitive member 21 is transferred to the transfer paper P while being transferred to the transfer conveyance belt 454 of the transfer conveyance belt device 45 by the transfer electrode 24 and the separation electrode 25 at the transfer position Bo. Is, transfer sheet P is separated from the photosensitive member 21 surface, it is conveyed to the fixing unit 50 by the transfer conveyor belt device 45.

  The fixing unit 50 includes a fixing roller 51 and a pressure roller 52. By passing the transfer paper P between the fixing roller 51 and the pressure roller 52, the toner is fixed by heating and pressing. After the toner image has been fixed, the transfer paper P is discharged onto the paper discharge tray 64.

  The above describes the state in which image formation is performed on one side of the transfer paper. However, in the case of double-sided copying, the paper discharge switching member 170 is switched, the transfer paper guide 177 is opened, and the transfer paper P is indicated by a broken arrow. Conveyed in the direction.

  Further, the transfer paper P is transported downward by the transport mechanism 178 and switched back by the transfer paper reversing unit 179, and the rear end portion of the transfer paper P becomes the leading end portion and transported into the duplex copying paper supply unit 130. The

  The transfer paper P is moved in a paper feed direction by a conveyance guide 131 provided in the double-sided copy paper supply unit 130, the transfer paper P is re-fed by the paper supply roller 132, and the transfer paper P is guided to the conveyance path 40. .

  Again, as described above, the transfer paper P is conveyed in the direction of the photosensitive member 21, the toner image is transferred to the back surface of the transfer paper P, fixed by the fixing unit 50, and then discharged onto the paper discharge tray 64.

  As the image forming apparatus, the above-described photosensitive member and components such as a developing device and a cleaning device may be integrally combined as a process cartridge, and this unit may be configured to be detachable from the apparatus main body. Further, at least one of a charger, an image exposure device, a developing device, a transfer or separation device, and a cleaning device is integrally supported together with a photosensitive member to form a process cartridge, and a single unit that is detachable from the apparatus main body. It is good also as a structure which can be attached or detached using guide means, such as a rail of an apparatus main body.

  The present invention will be specifically described below with reference to examples, but the embodiments of the present invention are not limited to these examples.

(Preparation of external additives)
The following external additives were prepared.
External additive 1: Hydrophobized silica particle external additive having a number average primary particle size of 5 nm 2: Hydrophobized silica particle external additive having a number average primary particle size of 10 nm 3: Hydrophobized silica having a number average primary particle size of 60 nm Particle external additive 4: Hydrophobized silica particle external additive having a number average primary particle size of 80 nm 5: Hydrophobized titania particle external additive having a number average primary particle size of 300 nm 6: Polymethyl having a number average primary particle size of 800 nm Methacrylate resin particle external additive 7: polymethyl methacrylate resin particles having a number average primary particle size of 1100 nm.

<Production of toner>
A toner was prepared as follows.

<Preparation of core resin particle 1>
First stage polymerization In a 5 L reaction vessel equipped with a stirrer, temperature sensor, condenser, and nitrogen inlet, the following compounds were added and mixed:
Styrene 110.9 parts by mass n-butyl acrylate 52.8 parts by mass Methacrylic acid 12.3 parts by mass
After adding 93.8 parts by mass of paraffin wax “HNP-57 (Nippon Seiki Co., Ltd.)”, it was heated to 80 ° C. and dissolved to obtain a polymerizable monomer solution.

  On the other hand, a surfactant solution was prepared by dissolving 2.9 parts by mass of sodium polyoxyethylene (2) dodecyl ether sulfate in 1340 parts by mass of ion-exchanged water. After heating the surfactant solution to 80 ° C., the polymerizable monomer solution is added, and the polymerizable monomer is added by a mechanical disperser “CLEAMIX (manufactured by M Technique)” having a circulation path. The solution was mixed and dispersed for 2 hours. Then, a dispersion of emulsified particles (oil droplets) having an average particle size of 245 nm was prepared.

  Next, after adding 1460 parts by mass of ion-exchanged water, an initiator solution in which 6 parts by mass of a polymerization initiator (potassium persulfate) is dissolved in 142 parts by mass of ion-exchanged water, 1.8 parts by mass of n-octyl mercaptan, Was added to bring the temperature to 80 ° C. This system was heated and stirred at 80 ° C. for 3 hours to conduct polymerization (first stage polymerization) to produce resin particles. This is designated as “resin particle 1”.

Second stage polymerization (formation of outer layer)
An initiator solution prepared by dissolving 5.1 parts by mass of potassium persulfate in 197 parts by mass of ion-exchanged water is added to the “resin particle 1”, and the following polymerizable monomer is mixed under a temperature condition of 80 ° C. The mixed solution having the monomer was added dropwise over 1 hour. The liquid mixture containing the monomer is
Styrene 282.2 parts by weight n-butyl acrylate 134.4 parts by weight Methacrylic acid 31.4 parts by weight n-octyl mercaptan 4.93 parts by weight After completion of dropping, the mixture is heated and stirred at 80 ° C. for 2 hours. To carry out the second stage polymerization (formation of the outer layer). Thereafter, cooling was performed to obtain “core resin particles 1”.

  The formed “core resin particle 1” had a weight average molecular weight of 21,300, a mass average particle diameter of 180 nm, and a glass transition point of 39 ° C.

(Preparation of colorant dispersion)
While stirring 900 parts by weight of an aqueous solution of 10% by weight sodium dodecyl sulfate, 210 parts by weight of the colorant “Regal 330R” is gradually added, and then dispersed using a stirrer “Claremix” (MTechnics). By doing so, a colorant dispersion was prepared. This is referred to as a “colorant dispersion”. The average dispersion diameter of the colorant particles in the colorant dispersion was measured using a dynamic light scattering particle size analyzer “Microtrack UPA150” (manufactured by Nikkiso Co., Ltd.), and found to be 150 nm.

<Preparation of toner base particles>
(Preparation of toner base particles 1)
Core particle formation (salting out / fusion (association / fusion) process)
In a reaction vessel equipped with a stirrer, temperature sensor, cooling pipe, nitrogen introduction device,
"Core resin particle 1" 420 parts by mass (in terms of solid content)
900 parts by mass of ion-exchanged water 200 parts by mass of “colorant dispersion” (in terms of solid content)
Was added and stirred. After adjusting the temperature in the reaction vessel to 30 ° C., 5 mol / liter sodium hydroxide aqueous solution was added to this solution to adjust the pH to 9.

Next, an aqueous solution in which 2 parts by mass of magnesium chloride hexahydrate is dissolved in 1000 parts by mass of ion-exchanged water is added to the reaction system over 10 minutes at 30 ° C. with stirring, and the mixture is allowed to stand for 3 minutes. Once started, the system was heated to 65 ° C. over 60 minutes to initiate the association. In this state, the particle size of the associated particles was measured by “Multisizer 3 (manufactured by Coulter)”, and when the volume-based median system (D ₅₀ ) of the particles became 7.0 μm, 40.2 mass of sodium chloride. An aqueous solution in which 1000 parts by mass of ion-exchanged water was dissolved was added to stop particle size growth.

  Further, the mixture was heated to 80 ° C. and stirred for 1 hour to release bubbles adhering to the particle surface to form undulations on the particle surface, thereby preparing a dispersion liquid of “toner base particle 1”.

  The circularity of “toner base particle 1” was measured by “FPIA2100” (manufactured by Systex) and found to be 0.930.

Washing and drying process The “toner base particle 1” dispersion is subjected to solid-liquid separation using a basket-type centrifuge “MARK III model number 60 × 40 (manufactured by Matsumoto Kikai Co., Ltd.)”. A toner cake of “base particles 1” was formed. Then, washing and solid-liquid separation of “toner base particles 1” were repeated using the basket type centrifugal separator until the electric conductivity of the filtrate reached 5 μS / cm. After the filtrate has a predetermined electrical conductivity, a drying apparatus “flash jet dryer (manufactured by Seishin Enterprise Co., Ltd.)” is used to perform a drying process until the water content becomes 0.5 mass%, thereby obtaining “toner base particles”. 1 "was obtained. “Mother toner particle 1” had a median diameter (D ₅₀ ) of 7.0 μm and a glass transition point of 39 ° C. on a volume basis.

  The difference in level and size of the waviness of 300 toner base particles was measured by the above method. As a result, the level difference of waviness was 30 nm on average, the size of waviness was 70 nm, and the ratio of waviness was 50% on average.

(Preparation of toner base particles 2 to 8)
“Toner base particles 2 to 8” were prepared in the same manner except that the stirring conditions in preparation of “toner base particles 1” were changed as shown in Table 1 below.

(Preparation of toner base particles 9)
In the production of the core resin particle 1, the monomer amount in the first stage polymerization is changed to 115.3 parts by mass of styrene, 48.4 parts by mass of n-butyl acrylate, 12.3 parts by mass of methacrylic acid, and the monomer in the second stage polymerization. “Toner base particles 9” were prepared in the same manner except that the amount was changed to 293.4 parts by mass of styrene, 123.2 parts by mass of n-butyl acrylate, and 31.4 parts by mass of methacrylic acid. The “toner base particles 9” had a volume-based median diameter (D ₅₀ ) of 7.0 μm and a glass transition point of 44 ° C.

(Preparation of toner base particles 10-13)
“Toner base particles 10 to 13” were prepared in the same manner except that the stirring conditions in the production of “toner base particles 9” were changed as shown in Table 1 below.

  Table 1 shows the temperature and rotation speed at the time of preparation of each toner base particle, the particle size of the toner base particle, the glass transition point (Tg), the average height difference of the waviness, the average size, and the average ratio of waviness. In addition, the glass transition point (Tg), the average height difference of waviness, the average size, and the average ratio of waviness were measured by the above methods.

<Production of toner>
(Preparation of Toner 1)
As an external additive, 1.2 parts by mass of “external additive 2 (10 nm)” and “external additive 5 (80 nm)” are added to 100 parts by mass of “toner base particle 1” produced above. Then, using a “Henschel mixer (manufactured by Mitsui Miike Chemical Co., Ltd.)”, mixing for 5 minutes produced “Toner 1”.

(Production of toners 2 to 20)
External additives were added to the “toner base particles 2 to 13” prepared above as shown in Table 2, and mixed under the same conditions as in the toner 1 to prepare “toners 2 to 20”.

  Note that the average height difference, the average size, and the average ratio of waviness of the toner particles after the external additive treatment is washed with a surfactant water and the external additive is removed are the values before the external additive treatment. The value of the toner base particles was the same.

  Table 2 shows the No. of the external additive used for preparing the toner. Indicates.

<Production of developer>
To 100 parts by mass of a ferrite carrier having a volume average particle diameter of 35 μm coated with a silicone resin, 6 parts by mass of each of the toners prepared above are added and mixed for 10 minutes using a “Nauter mixer (manufactured by Hosokawa Micron)”. Developers 1-20 "were prepared.

<Evaluation>
The evaluation was performed using a commercially available multi-function machine “bizhub PRO1050” (manufactured by Konica Minolta Business Technologies, Inc.) adopting an electrophotographic method.

Printing, normal temperature and normal humidity environment (20 ℃, 55% RH) below, was 500,000 sheets printed character document printing rate of 1% of A4 size high quality paper (64g / ^{m 2).}

  The evaluation was performed on the charge amount, image density, and fog.

<Charge amount>
After the initial printing and after printing 500,000 sheets, 2 g of the developer was sampled from the image forming apparatus, and the toner charge amount of this sample was measured using a charge amount measuring device “Blow-off type TB-200” (manufactured by Toshiba). .

Specifically, a measurement sample is loaded into a sample part equipped with a 400 mesh stainless steel screen of the above charge amount measuring apparatus, and a blow pressure of 50 kPa (0. 0. 0) in a normal temperature and humidity environment (20 ° C., 55% RH). The electric charge is measured by blowing with nitrogen gas for 10 seconds under the condition of 5 kgf / cm ² ). The charge amount (μC / g) is calculated by dividing the measured charge by the mass of the flying toner.

  In addition, regarding the charge amount, the difference between the initial value and the value after printing 500,000 sheets is 20 μC / g or less.

<Image density>
The density of the solid image was printed on a high-quality paper (64 g / m ² ) at the initial stage and after printing 500,000 sheets, and the density of the solid black image portion was measured using a reflection densitometer “RD-918” (manufactured by Macbeth). Spot measurement was performed and the average image density was evaluated.

  The image density is 1.30 or more as acceptable.

<Cover>
After printing 500,000 sheets, a plain original is printed on high-quality paper (64 g / m ² ), and the fog on the printed image is 12 points using a reflection densitometer “RD-918” (manufactured by Macbeth). It measured and evaluated by the average value.

  In addition, a fogging of 0.02 or less is acceptable.

  Table 2 shows the evaluation results.

  As is clear from the results of Table 2, “Toners 1 to 5, 10 and 16 to 20” of “Examples 1 to 11” of the present invention obtained satisfactory results in all the evaluation items. “Toners 6 to 9, 11 to 15” of “Comparative Examples 1 to 9” outside the invention did not satisfy the above evaluation items due to some problems.

FIG. 3 is a schematic diagram illustrating an example of toner base particles having undulations on the surface. FIG. 2 is an enlarged cross-sectional view of toner particles showing an example of the behavior of an external additive on the surface of toner particles when printing is performed. 1 is a cross-sectional configuration diagram illustrating an example of an image forming apparatus using a toner of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Toner particle 2 Toner base particle 3 Toner base 4 Level difference of waviness 5 Size of waviness 6 Waviness part 7 Mountain part (high part)
8 Valley part (low part)
9 Large diameter external additive 10 Small diameter external additive

Claims (2)

In the toner in which the surface of the toner base particle having a binder resin, a colorant, and a release agent has undulations formed from peaks and valleys of a specific size, and the external additive is captured in the valley portions.
The difference in level of the swell is 30 to 200 nm on average, the size of swell is 20 to 300 nm on average, and the ratio of swell is 20 to 100% on the average of the toner particle surface,
A toner comprising at least two types of external additives having different number average primary particle sizes as the external additives. The toner according to claim 1, wherein the external additive has a number average primary particle size of 10 to 60 nm and a number average primary particle size of 80 nm to 1 μm.

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