JP2010039171A - Toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a toner having sufficient low temperature fixability, preventing an acicular void in a solid image part even in printing a great number of sheets and continuously providing high-quality printed images. <P>SOLUTION: The toner contains a binder resin and wax, wherein the wax in the toner particles shows a number average median diameter (D<SB>50</SB>) of 0.5 to 2.0 μm and a shape factor SF-1 of not more than 130. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

  With the progress of energy saving, low temperature fixing technology is being developed in the electrophotographic industry.

  Performance required for toner to achieve low temperature fixing satisfies low temperature fixability (for example, prevention of occurrence of fixing offset on the low temperature side) and storage stability (for example, anti-aggregation in toner bottles or cartridges). It is required to make it.

  In order to achieve both prevention of occurrence of offset and anti-aggregation property, a method of making the toner structure a core / shell type has been considered and studied.

As a method for producing a core-shell type toner, resin particles obtained by polymerizing a polymerizable monomer in a solution are aggregated and fused to form a core portion, and a resin particle solution is further added to the top of the core portion. A method for forming a shell layer is known (see Patent Documents 1 and 2).
JP 2004-109939 A JP 2002-116574 A

  However, the core-shell toner as described above has a remarkable effect of aggregation resistance due to the shell layer having a high glass transition point. However, when the toner is printed in an image forming apparatus of a low-temperature fixing specification at a high speed, printing is performed. The shell layer having the high glass transition point causes a problem that the wax is hardly eluted on the surface of the toner particles and low temperature offset occurs.

  In order to prevent the occurrence of low temperature offset, it was effective to add a wax having a low melting point in the toner particles, since the toner particles were easily eluted on the surface during fixing.

  However, when wax having a low melting point is contained in the toner particles, a new problem that needle-like white spots occur in the image area during printing of a large number of sheets.

  An object of the present invention is to provide an excellent toner that satisfies the low-temperature fixability and does not have needle-like white spots in a solid image portion even when a large number of sheets are printed, and can continuously obtain a high-quality print image.

  The present invention is achieved by adopting the following configuration.

1. In a toner containing a binder resin and wax,
A toner having a number average median diameter (D ₅₀ ) of the wax of 0.5 to 2.0 μm and a wax shape factor SF-1 of 130 or less.

  2. 2. The toner according to 1 above, wherein the wax is a mixture of a low melting point wax and a high melting point wax.

  3. 3. The toner according to 1 or 2 above, wherein the high-melting wax and the low-melting wax are mixed in a ratio of 2.3 to 99.0 times by mass of the low-melting wax with respect to the high-melting wax.

  4). 4. The toner according to any one of 1 to 3, wherein the high melting point wax has a melting point of 77 to 96 ° C., and the low melting point wax has a melting point of 2 to 25 ° C. lower than the melting point of the high melting point wax.

  The toner of the present invention satisfies the low-temperature fixability, and has an excellent effect that a solid image portion does not have needle-like white spots even when a large number of sheets are printed, and a high-quality printed image can be continuously obtained.

  The inventors of the present invention have studied toners that satisfy low-temperature fixability and do not have needle-like white spots in a solid image portion even when a large number of sheets are printed, and a high-quality print image can be continuously obtained.

  As a result of the investigation, it has been found that in a toner in which a low melting point wax is contained in a resin having a low glass transition point, the wax tends to bleed out to the surface of the toner particles during storage or printing.

  When printing was performed using toner with the bleed-out wax on the toner particle surface, the bleed-out wax adhered to the surface of the photoreceptor, and it was confirmed that the place where the wax adhered became needle-like white spots.

  The present inventors have examined a toner in which wax does not bleed out on the surface of toner particles during storage or printing.

  As a result of various studies, it has been found that the wax does not easily bleed out by controlling the size and shape of the wax contained in the toner particles.

  Specifically, it has been found that when the size of the wax particles contained in the toner particles is increased and the shape thereof is made spherical, the wax can be prevented from bleeding out on the toner particle surfaces.

  When this toner was used, it was confirmed that a high-quality print image without needle-like white spots was continuously obtained even when a large number of sheets were printed.

  Hereinafter, the present invention will be described in detail.

The toner of the present invention contains a binder resin and a wax, the number average median diameter (D ₅₀ ) of the wax in the toner particles is 0.5 to 2.0 μm, and the shape factor SF-1 is 130 or less. It is a feature. The toner may contain colorant particles as necessary.

A toner having a number average median diameter (D ₅₀ ) of wax in toner particles of 0.5 to 2.0 μm and a shape factor SF-1 of 130 or less has a large particle size and a shape close to a spherical shape. The wax can be prevented from bleeding out at the time of printing, and the wax can easily flow out to the surface of the toner particles at the time of fixing, thereby preventing the occurrence of low temperature offset.

  As the wax used in the present invention, it is preferable to use two types of waxes having different melting points (high melting point and low melting point).

  The high melting point wax preferably has a melting point of 77 to 98 ° C. The low melting point wax preferably has a melting point 2 to 25 ° C. lower than the high melting point wax.

  The blending ratio of the high melting point wax and the low melting point wax is preferably 2.3 to 99.0 times by mass, more preferably 5 to 40 times by mass with respect to the high melting point wax.

  By adjusting the blending ratio of the high melting point wax and the low melting point wax in the above range, the image carrier (also referred to as a transfer material, an image support, etc.) with a low melting point wax (for example, ester wax) is used. Adhesiveness can be reliably obtained and fixing can be performed with sufficient fixing strength even by low-temperature fixing, and in the molecular state of a high melting point wax (for example, a hydrocarbon wax) and a low melting point wax (for example, an ester wax). The interaction due to the entanglement is sufficiently obtained, and the transfer of the wax as a whole to the toner particle surface can be suppressed.

  In the toner of the present invention, a binder resin and a wax are blended, a wax melt is formed by heating in the toner production process, and the size and shape of the wax are controlled by controlling the heat aging temperature and the cooling rate. Can be produced.

  Specifically, by setting the aging temperature in the toner production process to be higher than the melting point of the wax, a uniform melt (oil droplet) is first formed of the high melting point wax and the low melting point wax. At this time, a wax having a desired size can be formed by controlling the aging temperature. Then, the core particle which consists of high melting point wax is deposited in a melt by making temperature lower than melting | fusing point of high melting point wax. After that, by keeping the temperature lower (cooled) for a certain period of time, the low melting point wax is precipitated around the core particles of the high melting point wax, and the temperature is controlled for a certain period of time to control the shape of the wax. Can do.

By controlling the temperature of heat aging and the holding time during cooling in this manner, the number average diameter median diameter (D ₅₀ ) of the wax is large, and the wax shape can be rounded.

  The toner containing the wax having a large particle size and a round shape thus prepared was left in a high-temperature bath at 50 ° C. for 20 hours, and the bleed-out of the wax was observed. It was confirmed that it was difficult to bleed out to the particle surface.

  The confirmation of the state where the wax bleeds out to the toner particle surface can be performed by the following method.

As a confirmation method,
1. 1. Disperse 50 g of toner in 500 g of water containing a surfactant at 20 ° C. using an ultrasonic disperser to separate external additives attached to the surface of the toner particles. 2. Remove the supernatant of the separated external additive 3. Thoroughly dry the toner from which the external additive has been removed. 3. Leave the dried toner in a high temperature bath at 50 ° C. for 20 hours. 4. After standing, 50 g of toner is dispersed in 500 g of water containing a surfactant at 20 ° C. using an ultrasonic disperser. 5. Separating toner using a centrifuge 6. Visually observe the supernatant after separation. If the supernatant after separation is transparent, it is judged that there is no bleed out of the wax. If the supernatant after separation is turbid, it is judged that there is a bleed out of the wax. It is possible to confirm that the turbidity is a wax component by infrared analysis of the turbid liquid.

  Next, the shape of the toner of the present invention will be described.

  FIG. 1 is a schematic cross-sectional view showing an example of the toner of the present invention.

  As shown in FIG. 1, in the toner of the present invention, the wax particles 13 contained in the toner particles 10 have a large diameter, a round shape, and a uniform particle diameter. Even if there is no exposure, the number is small.

  FIG. 2 is a cross-sectional configuration diagram illustrating an example of a conventional (comparative example) toner.

  As shown in FIG. 2, conventional (comparative) toners include wax particles 13 having a small diameter to a large diameter, and are often in the form of flakes (elongated), and the wax is exposed on the surface of the toner particles 10. Many things are seen.

  1 and 2, reference numeral 10 denotes toner base particles, 11 denotes a binder resin, 12 denotes colorant particles, and 13 denotes wax particles.

The median particle size (D ₅₀ ) based on the number of toners is preferably 3 to 8 μm, and the colorant particles preferably have a particle size of 50 to 300 nm.

  In the present invention, toner is a general term for toner particles, toner particles are those obtained by attaching an external additive to toner base particles, and toner base is a general term for toner base particles.

  Next, the values defined in the present invention will be described.

<Melting point of wax>
The melting point of the wax is determined by measurement using “DSC-7 differential scanning calorimeter” (manufactured by PerkinElmer) and “TAC7 / DX thermal analyzer controller” (manufactured by PerkinElmer).

  As a measuring procedure, 4.5 to 5.0 mg of wax is precisely weighed to two decimal places, sealed in an aluminum pan (KIT No. 0219-0041), and set in a “DSC-7 sample holder”. The reference uses an empty aluminum pan. The measurement conditions were a measurement temperature of 0 ° C. to 200 ° C., a temperature increase rate of 10 ° C./min, a temperature decrease rate of 10 ° C./min, and heat-cool-heat temperature control. Analysis is performed based on the data in Heat.

<Number-average median diameter of the wax _(D 50)>
The number average median diameter (D ₅₀ ) of the wax in the toner particles is determined by measurement using an electron microscope (TEM) photograph and image processing analysis (LUZEX analysis) method.

The number average median diameter (D ₅₀ ) of the wax in the toner particle is calculated as the number average value of the horizontal ferret diameter of the wax in a cross section of the toner particle cut along a plane passing through the center of the toner particle.

  The cross-sectional sample of the toner particles is sufficiently dispersed in room temperature curable acrylic resin, embedded and cured, and then cut on the surface passing through the center of the toner particles using a microtome with diamond teeth, A flaky sample is cut out.

A cross-sectional sample of the toner particles was photographed with a transmission electron microscope JEM-2000FX (manufactured by JEOL Ltd.) at an acceleration voltage of 80 kV at a magnification of 30000 times, a photographic image was captured by a scanner, and an image processing analysis apparatus LUZEX AP ( The number average median diameter (D ₅₀ ) of the wax dispersed in the toner particles is measured using Nireco Co., Ltd.

In the present invention, 100 toner particles are selected at random, 100 toner particles are photographed, the number average median diameter (D ₅₀ ) of each wax in the photographed image is measured, and the average value is used as the number average median. The diameter (D ₅₀ ).

<Wax shape factor SF-1>
The shape factor SF-1 of the wax in the toner particles indicates the degree of roundness of the particles, and a value of SF-1 of 100 means that the shape is a true sphere. Therefore, it can be said that the wax suitable for the present invention has a round shape because the shape factor SF-1 is 130 or less.

  The shape factor SF-1 is defined by the following equation.

SF-1 = (maximum length of particle) ² / (projected area of particle) × (π / 4) × 100
The “maximum length” in the equation means a width that maximizes the interval between parallel lines when a projected image of wax on a plane is sandwiched between two parallel lines.

The shape factor SF-1 of the wax can be measured by the following procedure. That is, a photograph created by measuring the number average median diameter (D ₅₀ ) of the wax is read with a scanner or the like, and SF-1 is calculated from the read image data using an image analysis processor, and the average value is calculated as SF−. Set to 1. As the image analysis processing device, “LUZEX AP (manufactured by Nireco)” is used.

  In the present invention, 100 toner particles are selected at random, the shape factor SF-1 of each wax in the image obtained by photographing the 100 toner particles is measured, and the average value is defined as the shape factor SF-1.

  Next, the wax used in the present invention will be described.

"wax"
Examples of the wax that can be used in the toner of the present invention include conventionally known waxes, and specific examples thereof include the following.
(1) Hydrocarbon wax (2) Ester wax (3) Amide wax Ethylenediamine dibehenyl amide, trimellitic acid tristearyl amide, etc. (4) Dialkyl ketone wax, distearyl ketone, etc. (5) Other carnauba wax, Montan wax etc.

  In the present invention, it is preferable to mix and use a high melting point wax and a low melting point wax.

  As the high melting point wax, a hydrocarbon wax is preferable. Hydrocarbon wax tends to crystallize rapidly when cooled to a temperature lower than its melting point, and is suitable for producing core particles.

  Examples of hydrocarbon waxes include petroleum-derived paraffin wax, microcrystalline wax, and synthetic waxes such as Fischer-Tropsch wax, polyethylene wax, and polypropylene wax.

  As the low melting point wax, ester wax is preferable. Examples of the ester wax include saturated fatty acid esters represented by the following general formula (1).

General formula (1): R _< ¹ _> -(OCO-R _< ² _> ) _n
(In the formula, R ¹ and R ² each independently represent a saturated aliphatic hydrocarbon group having 1 to 40 carbon atoms which may have a substituent, and n is an integer of 1 to 4).
In the general formula (1), R ¹ is a monovalent to tetravalent saturated aliphatic hydrocarbon group, and the valence differs depending on n. For example, when n is 1, R ¹ is a monovalent saturated aliphatic hydrocarbon group, when n is 2, R ¹ is a divalent saturated aliphatic hydrocarbon group, and when n is 3, R ¹ is a trivalent saturated aliphatic hydrocarbon group, and when n is 4, R ¹ is a tetravalent saturated aliphatic hydrocarbon group. R ¹ has 1 to 40 carbon atoms, preferably 1 to 20 carbon atoms, more preferably 2 to 5 carbon atoms.

R ² is a monovalent saturated aliphatic hydrocarbon group. R ² has 1 to 40 carbon atoms, preferably 16 to 30 carbon atoms, and more preferably 18 to 26 carbon atoms.

Examples of the substituent that R ¹ and R ² may have include a hydroxyl group. n is an integer of 1 to 4, preferably an integer of 2 to 4, more preferably an integer of 3 to 4, and particularly preferably 4.

The saturated fatty acid ester represented by the general formula (1) can be suitably synthesized by a dehydration condensation reaction between an alcohol containing a predetermined R ¹ group and a carboxylic acid containing a predetermined R ² group.

  Specific examples of the saturated fatty acid ester include compounds represented by the following formulas (W1) to (W22).

  In the present invention, as long as the object of the present invention is achieved, other waxes such as carnauba wax may be added to the toner in addition to the hydrocarbon wax and ester wax.

  The amount of wax in the toner particles is preferably 1 to 30% by mass and more preferably 5 to 20% by mass with respect to the total mass of the toner.

  Next, a method for producing the toner of the present invention will be described.

  As a method for producing the toner, a method of producing the toner with a chemical toner in which the particle diameter and shape factor of the wax in the toner particles can be easily controlled is preferable.

  The method for producing the chemical toner is not particularly limited, and examples thereof include a method in which resin particles are formed by an emulsion polymerization method and the toner particles are assembled to produce a toner, and a method in which a toner is produced by suspension polymerization.

Hereinafter, an example of a toner production method using an emulsion polymerization association method will be described in detail.
(1) Dissolution / dispersion step of dissolving or dispersing two kinds of waxes having different melting points in a radical polymerizable monomer (2) Polymerization step for preparing a dispersion of resin particles (3) Resin particles in an aqueous medium Agglomeration and fusion step of aggregating and fusing the colorant particles to obtain associated particles (4) Aging the associated particles with thermal energy to adjust the shape and adjusting the particle diameter, shape and shape factor of the wax, A maturing step for producing a dispersion of the toner base (5) A cooling step for cooling the dispersion of the toner base (6) A solid-liquid separation of the toner base from the cooled dispersion of the toner base, and a surface activity from the toner base (7) A drying step for drying the washed toner base. (8) A step of adding an external additive to the dried toner base.

  Hereinafter, each step will be described.

[Dissolution / dispersion process]
This step is a step of preparing a radical polymerizable monomer solution containing the wax by dissolving or dispersing two kinds of waxes having different melting points in the radical polymerizable monomer.

[Polymerization process]
In a preferred example of this polymerization step, a radically polymerizable monomer solution containing two kinds of waxes having different melting points is added to an aqueous medium containing a surfactant, and mechanical energy is added to form droplets. Then, the polymerization reaction is allowed to proceed in the droplets by radicals from the water-soluble radical polymerization initiator. In addition, you may add the resin particle as a core particle in the said aqueous medium.

  By this polymerization step, resin particles having a wax, a hydrophilic resin, and a hydrophobic resin are obtained. Such 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 addition, when using uncolored resin particles, the dispersion of the colorant particles is added to the dispersion of the resin particles in the fusion and aging process described later, and the resin particles and the colorant particles are melted. By attaching it, it can be made a toner base.

[Aggregation / fusion process]
In water containing resin particles and colorant particles, a salting-out agent made of an alkali metal salt or alkaline earth metal salt is added as an aggregating agent having a critical aggregation concentration or more, and each particle is agglomerated and fused. To form associated particles. In the agglomeration / fusion step, internal additive particles such as wax particles and charge control agents can be aggregated together with the resin particles and the colorant particles.

[Aging process]
Aging is preferably performed by thermal energy (heating).

  Specifically, this is a step of adjusting the shape of the associated particles by heating and stirring the liquid containing the associated particles and adjusting the particle diameter, distribution, and shape of the wax to form a toner base.

  By making the temperature during heat aging higher than the melting point of the high melting point wax, a uniform melt (oil droplet) is first formed of the high melting point wax and the low melting point wax, and the aging temperature is made lower than the melting point of the high melting point wax. Thus, a high melting point wax is precipitated in the melt to form core particles of the high melting point wax.

  Thereafter, the aging temperature is further lowered to deposit the low melting point wax around the core particles of the high melting point wax.

  In the present invention, the size and shape of the wax are controlled by adjusting the temperature at the time of thermal aging and the cooling conditions.

[Cooling process]
This step is a step of cooling the toner base dispersion. 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.

[Solid-liquid separation and washing process]
In this solid-liquid separation / washing step, a solid-liquid separation process for solid-liquid separation of the toner base from the dispersion of the toner base cooled to a predetermined temperature in the above-described step, and a solid-liquid separated toner cake (in a wet state) A cleaning process is performed to remove deposits such as a surfactant and a salting-out agent from an aggregate obtained by agglomerating a toner base in a cake form. Here, the filtration method is not particularly limited, such as a centrifugal separation method, a vacuum filtration method using Nutsche or the like, a filtration method using a filter press or the like.

[Drying process]
In this step, the washed toner cake is dried to obtain a dried toner base. 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 water content of the dried toner base is preferably 5% by mass or less, and more preferably 2% by mass or less. In addition, when the toner bases subjected to the drying treatment are aggregated with 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.

[External process]
In this step, an external additive is mixed with the dried toner base to produce a toner.

  As an external additive mixing device, a mechanical mixing device such as a Henschel mixer or a coffee mill can be used.

  Next, materials constituting the toner will be described.

  The toner contains a binder resin, a colorant, and two types of waxes having different melting points.

(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.

  It is more preferable to use a combination of monomers having an ionic dissociation group as the polymerizable monomer constituting the binder 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, polyfunctionality 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 used in the present invention, a known inorganic or organic colorant can be used. Specific colorants are shown below.

  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 74, 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.

(wax)
The wax used in the present invention is the above wax.

(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.

(External additive)
Examples of inorganic particles that can be used as an external additive include conventionally known particles. Specifically, silica fine particles, titania fine particles, alumina fine particles, and complex oxides thereof can be preferably used. These inorganic particles are preferably hydrophobic.

  Examples of organic fine particles that can be used as an external additive include spherical fine particles having a number average primary particle size of about 10 to 2000 nm. Examples of the constituent material of the organic fine particles include polystyrene, polymethyl methacrylate, styrene-methyl methacrylate copolymer, and the like.

<Developer>
The toner according to 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 size of the carrier is preferably 20 to 100 μm, and more preferably 25 to 80 μm.

  The particle size of the carrier can be typically measured by a laser diffraction particle size distribution measuring apparatus “HELOS” (manufactured by SYMPATEC) 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 silicon resin, an ester resin, a fluorine-containing polymer resin, or the like is used. In addition, the resin for constituting the resin-dispersed carrier is not particularly limited, and a known resin can be used. For example, a styrene-acrylic resin, a polyester resin, a fluorine resin, a phenol resin, or the like is 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 apparatus in which the toner of the present invention is preferably used will be described.

<Image forming apparatus>
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 to 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 an image forming apparatus, a semiconductor laser or a light emitting diode can be used as an image exposure light source when forming an electrostatic latent image on a photoreceptor. 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. Let 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 is switched back by the transfer paper reversing unit 179, and the rear end portion of the transfer paper P is transported into the duplex copying paper supply unit 130 as the leading end. 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. In addition, 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 is 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 wax>
As waxes, hydrocarbon waxes and ester waxes shown in Table 1 were prepared.

  As the high melting point wax, “hydrocarbon waxes A to E” were prepared by thermal decomposition of high pressure polyethylene and fractionated. As the low melting point wax, “ester waxes A to G” having different melting points of the saturated fatty acid ester represented by the general formula (1) were prepared.

  Table 1 shows the melting points of the prepared high melting point wax and low melting point wax.

  In addition, melting | fusing point is the value measured by the said measuring method.

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

<Preparation of Resin Particle A>
First stage polymerization Into a reaction vessel equipped with a stirrer, temperature sensor, condenser, and nitrogen introduction device, 8 parts by weight of sodium dodecyl sulfate and 3000 parts by weight of ion-exchanged water are charged and stirred under a nitrogen stream at a stirring speed of 230 rpm. The internal temperature was raised to 80 ° C. After raising the temperature, 10 parts by mass of potassium persulfate dissolved in 200 parts by mass of ion-exchanged water was added, the temperature was again adjusted to 80 ° C., and the following monomer mixed solution was added dropwise over 1 hour, and then to 80 ° C. Then, polymerization was carried out by heating and stirring for 2 hours to prepare resin particles. This is designated as “resin particles (1A)”.

Monomer mixed solution Styrene 532.0 parts by mass n-butyl acrylate 192.0 parts by mass Methacrylic acid 76.0 parts by mass n-octyl mercaptan 16.0 parts by mass Second stage polymerization Stirrer, temperature sensor, condenser, nitrogen A reaction vessel equipped with an introduction device was charged with a solution prepared by dissolving 7 parts by mass of sodium polyoxyethylene (2) dodecyl ether sulfate in 800 parts by mass of ion-exchanged water, heated to 98 ° C., and then the resin particles (1A) 260 parts by mass and a solution prepared by dissolving the following monomer mixed solution at 90 ° C. were added, and the mechanical disperser “CLEARMIX” (manufactured by M Technique Co., Ltd.) having a circulation route was used for 1 hour. A dispersion liquid containing emulsified particles (oil droplets) was prepared by mixing and dispersing.

Dispersion Styrene 246.0 parts by mass n-butyl acrylate 119.0 parts by mass n-octyl mercaptan 1.5 parts by mass Hydrocarbon wax C (melting point 96 ° C.) 20.0 parts by mass Ester wax C (melting point 52 ° C.) 150.0 parts by mass An initiator solution prepared by dissolving 6 parts by mass of potassium persulfate in 200 parts by mass of ion-exchanged water was added to this dispersion, and the system was polymerized by heating and stirring at 82 ° C for 1 hour. To obtain resin particles. This is designated as “resin particles (2A)”.

Third stage polymerization Further, the following solution in which 11 parts by mass of potassium persulfate was dissolved in 400 parts by mass of ion-exchanged water was added to the solution of “resin particles (2A)”, and the temperature was set to 82 ° C.
Solution Styrene 414.0 parts by mass n-butyl acrylate 180.0 parts by mass Methacrylic acid 6.0 parts by mass n-octyl mercaptan 1.0 part by mass A monomer mixture solution was added dropwise over 1 hour. After completion of the dropping, polymerization was carried out by heating and stirring for 2 hours, and then cooled to 28 ° C. to obtain resin particles. This is designated as “resin particle A”.

(Preparation of resin particle J)
Into a reaction vessel equipped with a stirrer, a temperature sensor cooling pipe, and a nitrogen introduction device, 8 parts by mass of sodium dodecyl sulfate was charged into 3000 parts by mass of ion-exchanged water, and the internal temperature was 80 while stirring at a stirring speed of 230 rpm under a nitrogen stream. The temperature was raised to ° C. After the temperature increase, 10 parts by mass of potassium persulfate dissolved in 200 parts by mass of ion-exchanged water was added, the liquid temperature was again adjusted to 80 ° C., and the following monomer mixture was added dropwise over 1 hour, and then to 80 ° C. Then, polymerization was carried out by heating and stirring for 2 hours to prepare resin particles. This is designated as “resin particle J”.

Monomer mixed solution Styrene 570.0 parts by mass n-butyl acrylate 165.0 parts by mass Methacrylic acid 70.0 parts by mass n-octyl mercaptan 5.5 parts by mass <Preparation of Colorant Dispersion>
90 parts by mass of sodium dodecyl sulfate was dissolved in 1600 parts by mass of ion-exchanged water with stirring. While stirring this solution, 420 parts by mass of carbon black “Regal 330R” (Cabot Corp.) is gradually added, and then dispersed using a stirring device “Cleamix” (M Technique Corp.). A dispersion of colorant particles was prepared. This is referred to as a “colorant dispersion”. The particle size of the colorant particles in this colorant dispersion was measured using an electrophoretic light scattering photometer “ELS-800” (manufactured by Otsuka Electronics Co., Ltd.) and found to be 110 nm.

<< Production of Toner 1 >>
<Preparation of Toner Base 1>
(Aggregation / fusion process)
In a reaction vessel equipped with a stirrer, a temperature sensor, a cooling tube, and a nitrogen introduction device, 300 parts by mass of “resin particles A”, 1400 parts by mass of ion-exchanged water, and 120 parts by weight of “colorant dispersion liquid” are calculated. And a solution prepared by dissolving 3 parts by mass of sodium polyoxyethylene (2) dodecyl ether sulfate in 120 parts by mass of ion-exchanged water, adjusting the liquid temperature to 30 ° C., and then adding a 5N aqueous sodium hydroxide solution The pH was adjusted to 10. Next, an aqueous solution in which 35 parts by mass of magnesium chloride was dissolved in 35 parts by mass of ion-exchanged water was added at 30 ° C. over 10 minutes with stirring. After holding for 3 minutes, the temperature was raised and the system was heated to 90 ° C. over 60 minutes, and the particle growth reaction was continued while maintaining 90 ° C.

In this state, the particle size of the associated particles was measured by “Coulter Multisizer 3” (manufactured by Beckman Coulter), and when the median particle size (D ₅₀ ) on the volume basis became 5.0 μm, “resin 260 parts by mass of “particle J” was added, and particle growth was continued as it was. When the median particle diameter (D ₅₀ ) on the volume basis reaches 6.5 μm, an aqueous solution in which 150 parts by mass of sodium chloride is dissolved in 600 parts by mass of ion-exchanged water is added to stop the particle growth, and “associate particles” are formed. Obtained.

(Aging process)
“Association particles” are heated and stirred at a liquid temperature of 98 ° C. for 20 minutes and then gradually cooled over 60 minutes, thereby adjusting the shape of the association particles and simultaneously adjusting the particle size, particle size distribution, and shape factor of the wax. Prepared and produced core-shell structured particles.

  Thereafter, the solution was cooled to 20 ° C., hydrochloric acid was added to adjust the pH to 4.0, and stirring was stopped.

(Washing and drying process)
The particles produced in the aging step were subjected to solid-liquid separation with a basket-type centrifuge “MARK III model number 60 × 40” (manufactured by Matsumoto Kikai Co., Ltd.) to form a wet cake of toner base particles. The wet cake was washed with water using the basket-type centrifuge until the electric conductivity of the filtrate reached 5 μS / cm, and then transferred to a “flash jet dryer” (manufactured by Seishin Enterprise Co., Ltd.). % Of the toner was dried to prepare “Toner Base 1”.

(Process of adding external additives)
Next, 1% by mass of hydrophobic silica (number average primary particle size = 12 nm, hydrophobicity = 68) and hydrophobic titanium oxide (number average primary particle size = 20 nm, hydrophobicity) are prepared on the toner base 1 produced above. = 63) was added in an amount of 1% by mass and mixed using a “Henschel mixer” (Mitsui Miike Chemical Co., Ltd.). Thereafter, coarse particles were removed using a sieve having an opening of 45 μm to prepare “Toner 1”. The median particle size (D ₅₀ ) on a volume basis was 6.5 μm, which was the same as that of the associated particles.

<< Production of Toners 2 to 24 >>
“Toners 2 to 24” were prepared by changing the wax used in the production of “Toner 1”, the thermal aging temperature, and the cooling holding time as shown in Table 2.

Tables 2 and 3 show the wax used for the production of “Toners 1 to 24”, the melting point and blending amount of the wax, the melting point difference, the thermal aging temperature, the holding time during cooling, the toner particle size (volume-based median particle size ( D ₅₀ )), wax particle size (volume-based median particle size (D ₅₀ )) and wax shape factor.

  The particle size and the like were measured by the method described above.

<Preparation of developer>
Each of the toners prepared above was mixed with a silicon carrier-coated ferrite carrier having a volume average particle diameter of 60 μm so that the toner concentration was 6% by mass to prepare “Developers 1 to 24”. .

<< Evaluation of Wax Bleed Out >>
The evaluation of the state in which the wax bleeds out to the toner particle surface was performed by the method described above.

Evaluation standard ◎: The supernatant liquid is not cloudy and there is no bleed out of the wax. ○: The supernatant is slightly turbid but the bleed out of the wax is small. X: The supernatant is clearly turbid and the bleed out of the wax is large.

《Image evaluation》
As an image forming apparatus for image evaluation, “Bizhub PRO750” (manufactured by Konica Minolta Business Technologies Co., Ltd.), which is a high-speed and low-temperature fixing specification, is sequentially loaded with “Toner 1-23” and “Developer 1-23” prepared above. 200,000 sheets were printed in a printing environment of 30 ° C. and 80% RH.

  As for low-temperature fixability (including low-temperature offset), printing was performed with the image forming apparatus, but none of the toners caused problems.

<Evaluation of needle-like white spots in solid image area>
As the image forming apparatus, “Bizhub PRO750” (manufactured by Konica Minolta Business Technologies Co., Ltd.), which is a high-speed and low-temperature fixing specification, is sequentially loaded with “Toner 1-23” and “Developer 1-23” prepared above. 200,000 sheets were printed in a printing environment of 80% RH.

The needle-like white spots in the solid image portion are printed on 200,000 sheets and then printed on a high quality paper (64 g / m ² ) of A4 size. Evaluation was based on the number of omissions.

Evaluation criteria ◎: Needle-like white spots are not seen in the solid image portion, and good ○: One to three needle-like white spots are seen in the solid image portion, but there is no practical problem ×: Needle-like in the solid image portion There are practical problems with white spots exceeding 3 in number.

  Table 4 shows the evaluation results.

  As is clear from the evaluation results, “Embodiments 1 to 17” are excellent in all evaluation items, but “Comparative Examples 1 to 7” have a problem in any of the evaluation items.

FIG. 3 is a schematic cross-sectional view illustrating an example of the toner of the present invention. FIG. 6 is a cross-sectional configuration diagram illustrating an example of conventional (comparative example) toner. 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

10: toner base particles 11: binder resin 12: colorant particles 13: wax particles

Claims (4)

In a toner containing a binder resin and wax,
A toner having a number average median diameter (D ₅₀ ) of the wax of 0.5 to 2.0 μm and a wax shape factor SF-1 of 130 or less. The toner according to claim 1, wherein the wax is a mixture of a low melting point wax and a high melting point wax. 3. The toner according to claim 1, wherein the blending ratio of the high melting point wax and the low melting point wax is 2.3 to 99.0 times by mass of the low melting point wax with respect to the high melting point wax. The toner according to claim 1, wherein the melting point of the high melting point wax is 77 to 96 ° C., and the melting point of the low melting point wax is 2 to 25 ° C. lower than the melting point of the high melting point wax.

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