JP2011099954A - Toner for developing electrostatic latent image, and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide toner for electrostatic latent image development, the toner capable of striking a balance between the low temperature fixability, which greatly exceeds the current level, and the heat-resistant storage property, and to provide an image forming method using the toner. <P>SOLUTION: The toner for electrostatic latent image development has a core-shell structure, characterized in that: the core contains at least a hydrophobic resin having a glass transition temperature (Tg) of 10 to 30°C, a hydrophilic resin having a glass transition temperature (Tg) of 40 to 50°C, and a coloring agent; the hydrophobic resin having a low Tg is much present in the center area of the core; the proportion of the hydrophilic resin having a high Tg increases from the center toward the outside; and the shell part includes a hydrophilic resin having a Tg of 50 to 70°C. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electrostatic latent image developing toner and an image forming method using the toner.

  While energy saving is progressing in the industrial industry as a whole, low temperature fixing technology is being developed in the electrophotographic industry to reduce power consumption.

  However, toner for developing an electrostatic latent image that can be fixed at a low temperature (hereinafter, also simply referred to as toner) causes toner offset during image formation or aggregates while being stored in a toner bottle or cartridge. In many cases, there is a problem in storage stability, and it is difficult to achieve both.

  In order to achieve both prevention of offset generation and storage stability, a means for making the toner particle structure a core-shell structure is effective, and has been actively studied in recent years.

  As a method for producing toner particles having a core-shell structure, resin particles obtained by polymerizing a polymerizable monomer in a dispersion liquid are aggregated and fused to form a core portion, and further, resin particles for forming a shell layer in the liquid. Is known, and a shell layer is formed on the surface of the core part (see Patent Documents 1 and 2).

  However, in the conventional method of forming core-shell toner particles by adding resin particles for the shell after forming the core particle, the physicochemical properties of the core resin and the physicochemical properties of the resin forming the shell are If the difference is too great, the affinity between the core and the shell is lowered, and the shell-forming film cannot be formed uniformly on the core surface, or even once formed, the film tends to peel off. As a result, a core part that easily deforms or melts even at a low temperature and a shell part that firmly encloses the core part cannot be formed, and it has not been possible to achieve both ultra-low temperature fixing properties and heat-resistant storage properties (Patent Document 3).

JP 2002-116574 A JP 2005-234542 A JP 2007-4127 A

  In order to achieve both low-temperature fixing and heat-resistant storage stability at the present time, if the glass transition temperature (Tg) of the core part is lowered, the difference in glass transition temperature (Tg) from the shell part is very large. And the adhesiveness of the interface drops. On the other hand, as the speed of the image forming apparatus increases, the stress applied to the toner increases more and the interfacial peeling of the shell portion becomes remarkable.

  An object of the present invention is to provide an electrostatic latent image developing toner capable of achieving both low-temperature fixability and heat-resistant storage stability, which greatly exceeds the current level, and an image forming method using the toner.

  The inventor of the present invention has conducted a detailed study. In order to achieve the object of the present invention, a resin having a low glass transition temperature (Tg) is formed at the core central portion of the core-shell type toner particles, and the shell outermost surface portion is formed. Resin having a high glass transition temperature (Tg) is distributed, and the glass transition temperature (Tg) of the resin in the intermediate region, particularly the core resin, is gradually increased from the center side. It was ascertained whether it was possible to approach the transition temperature (Tg), and the present invention was achieved.

(1)
In the electrostatic latent image developing toner having a core-shell structure, the core portion includes at least a hydrophobic resin having a glass transition temperature (Tg) of 10 to 30 ° C., and a hydrophilic resin having a glass transition temperature (Tg) of 40 to 50 ° C. It contains a colorant, and there are many low Tg hydrophobic resins in the center of the core part, and the ratio of the high Tg hydrophilic resin increases from the center to the outside, and the Tg of the shell part is 50-70. An electrostatic latent image developing toner comprising a hydrophilic resin at 0 ° C.

(2)
The glass transition temperature (Tg) of the hydrophobic resin in the core portion is 15 to 25 ° C., the glass transition temperature (Tg) of the hydrophilic resin is 42 to 47 ° C., and the glass transition temperature of the hydrophobic resin in the shell portion ( The toner for developing an electrostatic latent image according to (1), wherein Tg) is 55 to 65 ° C.

(3)
The content of the hydrophobic resin in the core part is 80 to 90% by mass of the core part resin, the content of the hydrophilic resin is 10 to 20% by mass, and the content of the hydrophilic resin in the shell part is the total content of the toner. The toner for developing an electrostatic latent image according to (1) or (2), wherein the toner is 5 to 10% by mass of the resin.

(4)
The electrostatic latent image developing toner according to any one of (1) to (3) is used, and at least the steps of forming a latent image on the electrophotographic photosensitive member, developing, transferring to a recording sheet, and heat fixing are performed. An image forming method.

  According to the present invention, it is possible to provide a toner for developing an electrostatic latent image that can achieve both low-temperature fixability and heat-resistant storage stability that greatly exceed the current level, and an image forming method using the toner.

FIG. 4 is a schematic diagram illustrating an example of a process in which a toner base having a core-shell structure is formed. 1 is a cross-sectional view illustrating an example of an image forming apparatus used in the present invention.

  As described above, lowering the core Tg is effective in realizing the low-temperature fixing that is the object of the present invention. At the same time, core-shell technology has been established to ensure the heat-resistant storage property of the toner. However, as the speed of the image forming apparatus increases, the stress applied to the toner due to stirring in the developing device is extremely large. With the toner that has attempted to achieve both low temperature fixing and heat-resistant storage with the core-shell technology, The Tg difference between the portion and the shell portion becomes large, and an interfacial peeling phenomenon occurs. Therefore, it was found that the interface peeling phenomenon can be solved by giving the core part a Tg slope, the Tg being low at the center, and the Tg gradually increasing toward the outside, and reducing the Tg difference from the shell. .

  The toner production method of the present invention, the material used, the characteristics of the produced toner, and the image forming method using the toner will be further described below.

[Hydrophobic resin]
The hydrophobic resin used in the present invention is a resin that does not contain an acid monomer (polymerizable monomer) in the composition component constituting the resin. Specifically, all resins formed from polymerizable monomers that do not contain so-called hydrophilic groups in the constituent components are applicable.

  That is, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, p-phenylstyrene, p-ethylstyrene, 2,4- Styrene or styrene such as dimethyl styrene, p-tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene Derivatives, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, Phenyl methacrylate, Methacrylic acid ester derivatives such as diethylaminoethyl acrylate and dimethylaminoethyl methacrylate, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-octyl acrylate , Acrylate derivatives such as 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, phenyl acrylate, olefins such as ethylene, propylene, isobutylene, vinyl chloride, vinylidene chloride, vinyl bromide, vinyl fluoride, Halogenated vinyls such as vinylidene fluoride, vinyl esters such as vinyl propionate, vinyl acetate and vinyl benzoate, vinyl ethers such as vinyl methyl ether and vinyl ethyl ether, vinyl methyl ketone, Vinyl ketones such as vinyl ethyl ketone and vinyl hexyl ketone, N-vinyl compounds such as N-vinyl carbazole, N-vinyl indole and N-vinyl pyrrolidone, vinyl compounds such as vinyl naphthalene and vinyl pyridine, acrylonitrile, methacrylonitrile, It is a resin formed from acrylic acid or methacrylic acid derivatives such as acrylamide.

[Hydrophilic resin]
On the other hand, the hydrophilic resin in the present invention is a resin containing an acid monomer (polymerizable monomer) in a composition component constituting the resin.

  The acid monomer has, for example, a substituent such as a carboxyl group, a sulfonic acid group, and a phosphoric acid group as a constituent group of the monomer. Specifically, acrylic acid, methacrylic acid, maleic acid, itaconic acid, Cinnamic acid, fumaric acid, maleic acid monoalkyl ester, itaconic acid monoalkyl ester, styrene sulfonic acid, allyl sulfosuccinic acid, 2-acrylamido-2-acrylic acid phosphooxypropyl methacrylate and the like.

  As components constituting the hydrophilic resin other than the acid monomer, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, p- Phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, Styrene or styrene derivatives such as pn-dodecylstyrene, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, methacrylic acid 2-ethylhexyl, stearyl methacrylate, Methacrylic acid ester derivatives such as lauryl acrylate, 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, vinylidene fluoride, vinyl esters such as vinyl propionate, vinyl acetate, vinyl benzoate, vinyl methyl ether, vinyl ethyl ether Vinyl ethers such as vinyl, 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. Acrylic acid or methacrylic acid derivatives such as vinyl compounds, acrylonitrile, methacrylonitrile, acrylamide and the like can be mentioned.

  As addition amount (composition ratio) of the acid monomer in hydrophilic resin, 5.0-20.0 mass% is preferable, More preferably, it is 5.0-10.0 mass%. Moreover, as hydrophilic resin, it is preferable to use combining 2 or more types of resin from which the composition ratio of an acid monomer differs. Since hydrophilic resins having different acid monomer ratios are used to coat a hydrophobic resin having a low glass transition temperature with two or more hydrophilic resins, a hydrophobic resin having low heat resistance can be effectively coated. It is.

  Further, in the resin having a low glass transition temperature (Tg) existing in the central portion of the core portion, Tg is 10 to 30 ° C., more preferably 15 to 25 ° C., and the content of the resin is 80 of the core portion resin. -90 mass% is preferable. By setting the Tg of the low Tg resin within the above range, low temperature fixing can be secured. On the other hand, the Tg of the resin on the high glass transition temperature (Tg) side of the core resin is 40 to 50 ° C., more preferably 42 to 47 ° C., and the content of the resin is preferably 10 to 20% by mass. By setting the Tg of the high Tg resin within the above range, the affinity with the shell portion is increased, the strength against stress is increased, and the low-temperature fixability is not inhibited. Furthermore, it is preferable that Tg of the whole core part is 15-30 degreeC.

  On the other hand, the Tg of the resin in the shell part of the toner particles is 50 to 70 ° C., more preferably 55 to 65 ° C., and the content thereof is preferably 5 to 10% by mass of the whole toner resin. If the content is less than the above, the entire core particle may not be properly covered, and if it is more than that, the fixability may be hindered.

  The glass transition temperature of the resin can be controlled by appropriately selecting the type, amount and molecular weight of the polymerizable monomer that forms the copolymer.

  As a method for calculating the glass transition temperature, the following theoretical glass transition temperature may be calculated in the present invention. Here, the theoretical glass transition temperature is calculated by multiplying the glass transition temperature when each component constituting the copolymer resin forms a homopolymer by each composition mass fraction, that is, by weighted averaging. is there. That is, the theoretical glass transition temperature Tg (referred to as absolute temperature Tg ′) is calculated from the following formula (1) using the glass transition temperature of the homopolymer of the component constituting the copolymer resin.

Formula (1) 1 / Tg ′ = W1 / T1 + W2 / T2 +... + Wn / Tn
(Wherein W1, W2,... Wn is the mass fraction of each polymerizable monomer with respect to the total polymerizable monomer constituting the copolymer resin, and T1, T2,... Tn are each polymerizable. (The glass transition temperature (absolute temperature) of a homopolymer formed using a monomer is shown.)
The glass transition temperature can be measured using a differential scanning calorimeter “DSC-7” (manufactured by PerkinElmer) and a thermal analyzer controller “TAC7 / DX” (manufactured by PerkinElmer).

  As a measurement procedure, 4.5 to 5.0 mg of toner is precisely weighed to two digits after the decimal point, sealed in an aluminum pan, and set in a DSC-7 sample holder.

  The reference used an empty aluminum pan. The measurement conditions were a measurement temperature of 0 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 was performed based on the data in Heat.

  The glass transition temperature is obtained by drawing an extension line of the baseline before the rise of the first endothermic peak and a tangent line indicating the maximum slope between the rise portion of the first peak and the peak vertex, and using the intersection as the glass transition temperature. Show.

[Production of toner]
The combination of the hydrophilic resin and the hydrophobic resin is not particularly limited as a polymerizable monomer constituting each resin.

  Specifically, the aggregated particles obtained by aggregating resin particles having a hydrophilic resin having a high glass transition temperature (high Tg) and a hydrophobic resin having a low glass transition temperature (low Tg) are subjected to thermal energy (heating ) And aging at the same time as fusing, core particles having a structure in which the hydrophilic resin is oriented outside the toner core portion and the hydrophobic resin is oriented inside (center portion of the core portion) are formed.

  The reason why the hydrophilic resin and the hydrophobic resin are oriented in the aggregated particles in this way is that the hydrophilic resin is attracted to the aqueous medium and oriented outward, the hydrophobic resin repels the aqueous medium, and the hydrophilic resin. Since it has a lower glass transition temperature than that, it is considered to be oriented inside.

  High Tg hydrophilic resin is present outside the agglomerated particles (core particle) and low Tg resin is present in the center of the core to ensure low temperature fixing performance and storage without toner offset A toner having excellent stability can be produced.

  In the present invention, since the separation structure by the hydrophobic resin and the hydrophilic resin is formed by utilizing the orientation with respect to water inside the core particle, the resin composition is oriented from the center to the surface inside the core particle. In addition, a hydrophilic resin layer (shell layer) having a high glass transition temperature (Tg) is formed thereon so that the thermal properties of the hydrophobic resin do not appear on the toner particle surface as they are. I can do it.

(Toner production method)
The toner manufacturing method of the present invention will be described with reference to FIG. 1, but the toner manufacturing method of the present invention is not limited to this.

  FIG. 1 is a schematic diagram illustrating an example of a process of forming a toner base having a core-shell structure.

  FIG. 1A is a schematic diagram showing a process in which resin particles having a hydrophilic resin and a hydrophobic resin are formed by two-stage polymerization.

  FIG. 1B is a schematic diagram showing a process (aggregation step) in which aggregated particles are formed by aggregating resin particles and colorant particles.

  FIG. 1 (c) shows a process in which agglomerated particles are aged at the same time as fusion to form core particles having a hydrophobic resin at the center and a hydrophilic resin structure at the surface (fusing / aging process). It is a schematic diagram.

  FIG. 1D is a schematic view of a step of forming a shell made of a hydrophilic resin on the core particles.

  In FIG. 1, a1 is a hydrophobic resin portion of a resin particle a3, a2 is a hydrophilic resin portion b1 is a colorant particle, b2 is an agglomerated particle, c1 and c2 are particles in a fusion / aging process, and c3 is a fusion / aging process. The core particle surface portion made of hydrophilic resin after completion, c4 is the core portion of the core particle made of hydrophobic resin, c5 is the particle core portion, d1 is the shell portion, and d2 is the toner particle (toner base).

  As shown in FIG. 1, first, resin particles a3 containing a hydrophilic resin and a hydrophobic resin are produced, and the resin particles a3 and the colorant are aggregated to form aggregated particles b2, and the aggregated particles b2 are fused. Thus, the core part c5 of the toner particles is manufactured.

  Next, in the shell forming step shown in FIG. 1D, a shell d1 is formed on the surface of the core part c5 of the toner particles using a hydrophilic resin, and this is used as toner particles (toner base material) d2.

  The toner base is a material before the external additive is processed into toner.

  The external addition process is a process for preparing a toner by mixing an external additive as necessary with the dried toner base. As an external additive mixing device, a mechanical mixing device such as a Henschel mixer or a coffee mill can be used.

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

  As a method for producing a toner, core particles (core part) are produced by a method including a step of aggregating resin particles having at least a hydrophilic resin and a hydrophobic resin to produce agglomerated particles and fusing the agglomerated particles. It is not particularly limited as long as it is produced and forms a shell part on this surface, and specific examples include emulsion polymerization / aggregation method, miniemulsion polymerization / aggregation method and the like.

  Next, an example of a toner manufacturing method using a miniemulsion polymerization / aggregation method will be described.

(1) Dissolution / dispersion step for dissolving or dispersing the release agent in the radical polymerizable monomer (2) Polymerization step for preparing a dispersion of core resin particles having a hydrophobic resin and a hydrophilic resin 3) Aggregation step of aggregating core resin particles and colorant particles in an aqueous medium to obtain aggregated particles (4) The aggregated core particles are heated with heat energy, and a hydrophobic resin is contained in the core particles and a hydrophilic resin is contained in the core particles. (5) A step of adding core resin particles to the core particle dispersion and fusing the shell resin particles to the core particle surface to form core-shell toner base particles. 6) Cooling step for cooling the dispersion of the toner base (7) Cleaning step for solid-liquid separation of the toner base from the cooled dispersion of the toner base and removing the surfactant from the toner base (8) Cleaning Processed (9) Step of Adding External Additive to Dry Toner Base Next, the particle size of the toner according to the present invention will be described.

[Toner particle size]
In the present invention, the particle diameter of the toner is preferably 3.0 to 8.0 μm, more preferably 4.0 to 7.0 μm in terms of volume-based median diameter (D ₅₀ ).

The measurement of the median diameter (D ₅₀ ) on a volume basis is performed as follows.

  Measurement and calculation are performed using a device in which a computer system for data processing (manufactured by Beckman Coulter) is connected to "Coulter Multisizer 3" (manufactured by Beckman Coulter). As a measuring means, 0.02 g of toner was conditioned with 20 g of a surfactant solution (for example, a surfactant solution in which a neutral detergent containing a surfactant was diluted 10 times with pure water for the purpose of dispersing the toner). Thereafter, ultrasonic dispersion is performed for 1 minute to prepare a toner dispersion. This toner dispersion is pipetted into a beaker containing ISOTON II (manufactured by Beckman Coulter, Inc.) in a sample stand until the measured concentration is 5 to 10% by mass. By setting this concentration range, a reproducible measurement value can be obtained. In the measuring machine, the measurement particle count number is 25000, the aperture diameter is 50 μm, and the frequency range is calculated by dividing the measurement range of 1 to 30 μm into 256. Let the particle diameter be the median diameter on a volume basis.

[Confirmation of core shell structure]
The confirmation of the core-shell structure of the toner particles according to the present invention is confirmed by, for example, a method of visually confirming a boundary line that is an interface between the core particles and the shell using a transmission electron microscope or a method of detecting the difference in hardness of the resin. Is.

  As a confirmation method using a transmission electron microscope, for example, LEM-2000 type (manufactured by Topcon Corporation), JEM-2000FX (manufactured by JEOL Ltd.) or the like is used. Specifically, the toner particles are first sufficiently dispersed in a room temperature curable epoxy resin, then embedded, dispersed in styrene fine powder having a particle size of about 100 nm, and then subjected to pressure molding. After the necessary blocks were dyed with ruthenium tetroxide or osmium tetroxide, a flaky sample was cut out using a microtome with diamond teeth, and a transmission electron microscope (TEM) was used. Then, the photograph is taken at a magnification (approximately 10,000 times) in which the cross section of one toner particle can be viewed. Next, in the said photograph, the boundary line used as the interface of a core particle and a shell is confirmed visually, confirming presence area, such as a coloring agent and wax, by visual observation.

  As a method for detecting the difference in hardness of the resin, a scanning probe microscope SPI3800N and a multifunctional unit SPA400 (manufactured by SII NanoTechnology Co., Ltd.) were used. The measurement sample is a block in which toner particles are embedded in an epoxy resin, cured for 24 hours at 60 ° C., and then a flat surface is cut out using a microtome with diamond teeth to smooth the cross section and the toner particle cross section can be observed. Using. The scanner was FS-100N (inner surface 100 μm, vertical 15 μm), the microcantilever was silicon nitride SN-AF01 (spring constant 0.08 N / m), and the measurement mode was micro viscoelastic mode (VE-AFM). . The excitation frequency is set to 3 to 5 kHz and the excitation amplitude is set to 4 to 6 nm, and four screens of the shape image, amplitude A, Asin δ, and Acos δ are simultaneously measured in a measurement area of 10 μm × 10 μm, and the shell layer is visually observed in the amplitude image. This was confirmed by observation.

  The number of toner particles to be measured is 50 in any method, and when a core-shell structure is confirmed in 95% by number or more of the particles, a toner having a core-shell structure is obtained.

  The core-shell structure refers to a state in which the shell is formed as a resin layer by fusing resin particles, and is different from a state in which particles such as external additive particles are adhered or fixed.

  Moreover, as an analyzer for examining the change in glass transition temperature (Tg) from the center to the surface in the core particle, there is Nano-TA2 (manufactured by Anasys Instruments). The measurement method is described below. First, the toner was embedded in an epoxy resin, the cross section was cut with a microtome, and this was attached to a sample stage to prepare a sample. Nano-TA2 (manufactured by Anasys Instruments) was connected to a scanning probe microscope SPI3800N (manufactured by SII Nanotechnology). First, a silicon thermal probe was attached to the scanning probe microscope, and the shape was observed in the contact AFM mode. The place where the transition temperature was to be measured was selected in the shape image, and the thermal probe was moved. For Nano-TA2, the temperature of the thermal probe was calibrated by measuring the melting point of a reference film of polycaprolactone, polyethylene, and polyethylene terephthalate in advance. The thermal probe was fixed at the measurement position and approached the sample surface. The temperature range for temperature increase was set, and the temperature was increased at 5 ° C./sec. In the chart of time and Diffraction (V), the temperature at which rapid thermal contraction occurs was defined as the glass transition temperature.

[Compounds used for toner preparation]
(Polymerization initiator)
It is used when preparing the above-described hydrophobic resin and hydrophilic resin.

  In the case of using an emulsion polymerization / aggregation method, a water-soluble radical polymerization initiator can be used. As the water-soluble polymerization initiator, persulfates such as potassium persulfate and ammonium persulfate, azobisaminodipropane acetate, azobiscyanovaleric acid and its salts, hydrogen peroxide and the like can be used.

(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.

  In addition, 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.

(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 the organic fine particles that can be used as the external additive include spherical fine particles having a number average primary particle diameter 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 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 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.

[Image Forming Method and Image Forming Apparatus]
The toner according to the present invention transfers an image obtained by toner development of an electrostatic latent image formed on a photoconductor, and transfers a transfer material on which the toner image is formed between heating members constituting a fixing device. It is suitably used for a contact-type fixing type image forming apparatus that passes and fixes.

  The image forming apparatus will be described below.

  FIG. 2 is a schematic view showing an example of an image forming apparatus in which the developer of the present invention is preferably used.

  In FIG. 2, 1Y, 1M, 1C and 1K are photosensitive members, 4Y, 4M, 4C and 4K are developing means, 5Y, 5M, 5C and 5K are primary transfer rollers as primary transfer means, and 5A is a secondary transfer means. Secondary transfer rollers 6Y, 6M, 6C and 6K are cleaning means, 7 is an intermediate transfer body unit, 24 is a heat roll type fixing device, and 70 is an intermediate transfer body.

  This image forming apparatus is called a tandem color image forming apparatus, and includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, an endless belt-shaped intermediate transfer body unit 7 as a transfer unit, and a recording member P. An endless belt-shaped sheet feeding / conveying means 21 and a heat roll type fixing device 24 as a fixing means. A document image reading device SC is disposed on the upper part of the main body A of the image forming apparatus.

  As one of the different color toner images formed on each photoconductor, an image forming unit 10Y that forms a yellow image includes a drum-shaped photoconductor 1Y as a first image carrier, and the photoconductor 1Y. A charging unit 2Y, an exposure unit 3Y, a developing unit 4Y, a primary transfer roller 5Y as a primary transfer unit, and a cleaning unit 6Y are arranged around the periphery. An image forming unit 10M that forms a magenta image as another different color toner image is arranged around a drum-shaped photoconductor 1M as a first image carrier, and around the photoconductor 1M. The charging unit 2M, the exposure unit 3M, the developing unit 4M, the primary transfer roller 5M as the primary transfer unit, and the cleaning unit 6M are included. In addition, an image forming unit 10C that forms a cyan image as another different color toner image includes a drum-shaped photoreceptor 1C serving as a first image carrier, and the periphery of the photoreceptor 1C. A charging unit 2C, an exposure unit 3C, a developing unit 4C, a primary transfer roller 5C as a primary transfer unit, and a cleaning unit 6C are disposed. An image forming unit 10K that forms a black image as one of other different color toner images is disposed around a drum-shaped photoreceptor 1K as a first image carrier, and the periphery of the photoreceptor 1K. A charging unit 2K, an exposure unit 3K, a developing unit 4K, a primary transfer roller 5K as a primary transfer unit, and a cleaning unit 6K.

  The endless belt-shaped intermediate transfer body unit 7 has an endless belt-shaped intermediate transfer body 70 as an intermediate transfer endless belt-shaped second image carrier that is wound around a plurality of rollers and is rotatably supported.

  Each color image formed by the image forming units 10Y, 10M, 10C, and 10K is sequentially transferred and synthesized on the rotating endless belt-shaped intermediate transfer body 70 by the primary transfer rollers 5Y, 5M, 5C, and 5K. A color image is formed. A recording member P such as a sheet as a transfer material accommodated in the sheet feeding cassette 20 is fed by the sheet feeding / conveying means 21, passes through a plurality of intermediate rollers 22 A, 22 B, 22 C, 22 D, and a registration roller 23, and is secondary. A color image is transferred onto the recording member P at a time by being conveyed to a secondary transfer roller 5 </ b> A as a transfer unit. The recording member P to which the color image has been transferred is fixed by a heat roller type fixing device 24, is sandwiched between paper discharge rollers 25, and is placed on a paper discharge tray 26 outside the apparatus.

  On the other hand, after the color image is transferred to the recording member P by the secondary transfer roller 5A, the residual toner is removed from the endless belt-shaped intermediate transfer body 70 from which the recording member P is separated by the curvature by the cleaning means 6A.

  During the image forming process, the primary transfer roller 5K is always in pressure contact with the photoreceptor 1K. The other primary transfer rollers 5Y, 5M, and 5C are in pressure contact with the corresponding photoreceptors 1Y, 1M, and 1C, respectively, only during color image formation.

  The secondary transfer roller 5A comes into pressure contact with the endless belt-shaped intermediate transfer body 70 only when the recording member P passes through the secondary transfer roller 5A and the secondary transfer is performed.

  In this way, toner images are formed on the photoreceptors 1Y, 1M, 1C, and 1K by charging, exposure, and development, and the toner images of the respective colors are superimposed on the endless belt-shaped intermediate transfer body 70, and are collectively applied to the recording member P The image is transferred, and fixed by pressing and heating with a heat roll type fixing device 24 and fixed. The photoconductors 1Y, 1M, 1C, and 1K after transferring the toner image to the recording member P are cleaned by the cleaning devices 6Y, 6M, 6C, and 6K after the toner remaining on the photoconductor is transferred and then charged as described above. Then, the exposure and development cycles are entered, and the next image formation is performed.

[Transfer material]
The transfer material used in the present invention is a support for holding a toner image, and is usually called an image support, a recording material, or transfer paper. Specifically, various transfer materials such as plain paper and fine paper from thin paper to thick paper, coated printing paper such as art paper and coated paper, commercially available Japanese paper and postcard paper, plastic film for OHP, cloth, etc. However, it is not limited to these.

  Hereinafter, specific embodiments of the present invention will be described by way of examples, but the present invention is not limited thereto.

<Production of toner>
The toner of the present invention was produced as follows.

  First, the following core resin particles and shell resin particles were prepared, and then a dispersion of colorant particles was prepared.

<Production of resin particles>
“Core resin particles” were prepared as described below.

<Preparation of core resin particle A>
(1) Polymerization of core low Tg (hydrophobic) resin particles A mixture containing the following monomers is heated to 90 ° C. with stirring, and 160 parts by mass of pentaerythritol tetrabehenate is dissolved in this mixture, A wax-containing monomer mixture was prepared.

Styrene 436.8 parts by mass n-butyl acrylate 277.2 parts by mass n-octyl-3-mercaptopropionate 2.7 parts by mass A reaction vessel equipped with a stirrer, a temperature sensor, a condenser tube, and a nitrogen introduction device was charged with poly A machine having a circulation path, charged with a solution prepared by dissolving 2 parts by mass of sodium oxyethylene (2) sodium dodecyl ether in 3000 parts by mass of ion-exchanged water, heated to 82 ° C., and added with the wax-containing monomer mixture. A dispersion liquid containing emulsified particles (oil droplets) was prepared by mixing and dispersing for 1 hour using a type disperser “CLEARMIX (manufactured by M Technique)”.

  Next, an initiator solution prepared by dissolving 10 parts by mass of potassium persulfate in 384 parts by mass of ion-exchanged water is added to the dispersion, and polymerization is performed by heating and stirring the system at 82 ° C. for 1 hour. Core low Tg (hydrophobic) resin particles A1 were prepared.

(2) Polymerization of Core High Tg (Hydrophilic) Resin Particles Next, 1.76 parts by mass of potassium persulfate is added to the solution containing the core low Tg (hydrophobic) resin A1, and 33.4 parts by mass of ion-exchanged water. The initiator solution dissolved in the part is added, the liquid temperature is set to 80 ° C., the mixture containing the following monomers is added dropwise over 1 hour, heated at 80 ° C. for 2 hours and then polymerized by stirring. , “Resin particle A for core (core A)” was obtained.

Styrene 86.2 parts by mass n-butyl acrylate 33.5 parts by mass Methacrylic acid 6.3 parts by mass n-octyl-3-mercaptopropionate 0.5 parts by mass <Preparation of resin particles B to I for core>
“Core resin particles B to I (core B to I)” were prepared in the same manner except that the polymerizable monomer used in the production of “core A” was changed as shown in Table 1.

<Preparation of core resin particle J>
A mixed solution containing the following monomers was heated to 90 ° C. while stirring, and 160 parts by mass of pentaerythritol tetrabehenate was dissolved in this mixed solution to prepare a wax-containing monomer mixed solution.

Styrene 456.5 parts by weight n-butyl acrylate 341.5 parts by weight Methacrylic acid 42.0 parts by weight n-octyl-3-mercaptopropionate 3.0 parts by weight A stirrer, temperature sensor, cooling tube, nitrogen introduction device A solution prepared by dissolving 2 parts by mass of sodium polyoxyethylene (2) sodium dodecyl ether sulfate in 3000 parts by mass of ion-exchanged water was charged into the attached reaction vessel, heated to 82 ° C., and the above wax-containing monomer mixture was added. Then, it was mixed and dispersed for 1 hour by a mechanical disperser “CLEARMIX (manufactured by M Technique Co., Ltd.)” having a circulation path to prepare a dispersion containing emulsified particles (oil droplets).

  Next, an initiator solution prepared by dissolving 10 parts by mass of potassium persulfate in 384 parts by mass of ion-exchanged water is added to the dispersion, and polymerization is performed by heating and stirring the system at 82 ° C. for 1 hour. A “core resin particle J (core J)” was produced.

St: Styrene BA: n-Butyl acrylate MAA: Methacrylic acid <Preparation of resin particle A for shell>
A reaction vessel equipped with a stirrer, temperature sensor, condenser, and nitrogen introducing device was charged with a solution prepared by dissolving 2.3 parts by mass of sodium dodecyl sulfate in 2800 parts by mass of ion-exchanged water, and stirred at a rate of 230 rpm under a nitrogen stream. The internal temperature was raised to 80 ° C. while stirring. After the temperature increase, a solution in which 10 parts by mass of potassium persulfate was dissolved in 400 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, followed by 80 ° C. After heating for 2 hours, polymerization was carried out by stirring to prepare “resin particles A for shell (shell A)”.

Styrene 602.6 parts by mass n-butyl acrylate 153.4 parts by mass Methacrylic acid 44.0 parts by mass n-octyl-3-mercaptopropionate 21.7 parts by mass <Preparation of Resin Particles BE for Shell>
“Shell resin particles B to E (shell B to E)” were prepared in the same manner except that the polymerizable monomer used in the production of “shell A” was changed as shown in Table 2.

<< 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. The particle diameter of this dispersion was measured using UPA (manufactured by Microtrac) and found to be 117 nm.

<< Production of Toner 1 >>
(Aggregation / fusion process)
In a reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introduction device, 300 parts by mass of core A in terms of solid content, 1400 parts by mass of ion-exchanged water, and 120 parts by mass of a colorant dispersion [1] Then, a solution in which 3 parts by mass of polyoxyethylene (2) sodium dodecyl ether sulfate was dissolved in 120 parts by mass of ion-exchanged water was added, the temperature was adjusted to 30 ° C., and then a 5 mol / liter sodium hydroxide aqueous solution was added. 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 is measured with “Coulter Multisizer 3 (manufactured by Beckman Coulter)”. The aqueous solution dissolved in was added to stop particle growth. Next, the mixture was heated and stirred at 90 ° C. for 30 minutes, and a large amount of hydrophobic resin was oriented at the center of the core particles and hydrophilic resin was oriented at the surface. Next, 21.9 parts by mass of the shell A in terms of solid content was dropped over 10 minutes, and after 1 hour, it was confirmed that the shell particles were fused to the surface of the core particles. Thereafter, an aqueous solution in which 100 parts by mass of sodium chloride is dissolved in 400 parts by mass of ion-exchanged water is added, and the mixture is heated and stirred at a liquid temperature of 90 ° C. Spheronization was performed until 0.965. Thereafter, the solution was cooled to 30 ° C. and stirring was stopped.

(Washing / drying process)
The particles produced in the aggregation / fusion process were solid-liquid separated using a basket-type centrifuge to form a wet cake of toner base particles. The wet cake was washed with ion exchange water at 35 ° C. until the electric conductivity of the filtrate reached 5 μS / cm with the basket-type centrifuge, and then transferred to “flash jet dryer (manufactured by Seishin Enterprise Co., Ltd.)”. The toner was dried until the amount became 0.5% by mass to prepare “toner base particles 1”.

(External additive treatment process)
1% by mass of hydrophobic silica (number average primary particle size = 12 nm) and 0.3% by mass of hydrophobic titania (number average primary particle size = 20 nm) are added to the “toner base particle 1”, and a Henschel mixer is used. By mixing, “Toner 1” was produced.

  Using a transmission electron microscope LEM-2000, the core-shell structure of the toner was confirmed by the measurement method described above. Moreover, using Nano-TA2, it was confirmed that the glass transition temperature (Tg) was increased from the central part to the surface part in the core particles by the measurement method described above.

<< Production of Toners 2-15 >>
“Toners 2 to 15” were produced in the same manner except that “core A” and “shell A” used in the aggregation / fusion process in the production of toner 1 were changed as shown in Table 3.

<Production of developer>
100 parts by mass of ferrite core and 5 parts by mass of copolymer resin particles of cyclohexyl methacrylate / methyl methacrylate (copolymerization ratio 5/5) are put into a high-speed mixer equipped with stirring blades and stirred and mixed at 120 ° C. for 30 minutes. Then, a resin coat layer was formed on the surface of the ferrite core by the action of mechanical impact force to obtain a carrier having a volume-based median diameter of 40 μm.

  The volume-based median diameter of the carrier was measured by a laser diffraction particle size distribution measuring apparatus “HELOS” (manufactured by Sympathic) equipped with a wet disperser.

  Toners were added to the carrier so that the toner concentration would be 7% by mass, respectively, and charged into a micro-type V-type mixer (Tsujii Chemical Co., Ltd.), and mixed at a rotational speed of 45 rpm for 30 minutes to prepare a developer.

<Evaluation>
(Evaluation of toner crushability)
The prepared developer is filled in a developing device used in a commercially available color multifunction peripheral “bizhub PRO C6500 (manufactured by Konica Minolta Business Technologies)”, and stirred for 1 hour at a speed of 400 rpm with a single drive. It was. Thereafter, a small amount of developer was collected, put into a beaker, 0.1 g of a commercially available surfactant and 20 g of pure water were added, the beaker was shaken while applying a magnet from the lower side of the beaker, and the toner was released from the carrier. . The supernatant was collected and the particle size distribution was measured with a Coulter Multisizer 3. Crushability was evaluated based on the increase amount N of the proportion of toner of X μm or less (volume basis) in the particle size distribution before and after stirring.

X = D ₅₀ before stirring (volume basis) −standard deviation σ of particle size distribution before stirring (volume basis)
N ₀ = ratio (%) of X μm or less (volume basis) of toner before stirring
N _m = ratio (%) of X μm or less (volume basis) of the toner after stirring
N = N _m −N ₀ (%)
The smaller the increase amount N of the proportion of the toner of X μm or less (volume basis) in the particle size distribution before and after stirring, the better the toner crushability.

◎: 0 to less than 1% ○: 1 to less than 5% ×: 5% or more (Fixability (under offset property))
The image evaluation was performed by sequentially loading the toner and the developer prepared above in a developing device of a commercially available color multifunction peripheral “bizhub PRO C6500 (manufactured by Konica Minolta Business Technologies, Inc.)”. In addition, modification was made so that the fixing temperature, the toner adhesion amount, and the system speed could be set freely. Using NPI 128 g / m ² (manufactured by Nippon Paper Industries Co., Ltd.) as an evaluation paper, a solid image with a toner adhesion amount of 11.3 g / m ² is fixed at a fixing speed of 300 mm / sec. The fixing lower limit temperature at which no cold offset occurs when fixing at a temperature of 5 ° C. and setting at a temperature of 5 ° C. was evaluated. The lower this fixing minimum temperature is, the better the fixing property is, and 150 ° C. or less is acceptable.

(Heat resistant storage)
0.5 g of toner is placed in a 10 ml glass bottle with an inner diameter of 21 mm, the lid is closed, shaken 600 times at room temperature with a tap denser KYT-2000 (manufactured by Seishin Enterprise), and then the lid is removed at 55 ° C. and 35% RH. For 2 hours. Next, place the toner on a 48-mesh (mesh 350 μm) sieve, taking care not to crush the toner aggregates, set the powder tester (manufactured by Hosokawa Micron), and fix it with a press bar and knob nut. After adjusting the vibration strength to a feed width of 1 mm and applying vibration for 10 seconds, the ratio (mass%) of the amount of toner remaining on the sieve was measured.

  The toner aggregation rate is a value calculated by the following formula.

Toner aggregation rate (%) = residual toner mass on sieve (g) /0.5 (g) × 100
The heat resistant storage stability of the toner was evaluated according to the criteria described below.

A: The toner aggregation rate is less than 15% by mass (the toner has excellent heat-resistant storage stability)
○: Toner aggregation rate of 20% by mass or less (good heat storage stability of toner)
X: Toner aggregation rate exceeds 20% by mass (toner has poor heat-resistant storage property and cannot be used)
The evaluation results are shown in Table 3 below.

  Examples 1 to 7 in the present invention are good because all the characteristics are at a level that can be put into practical use, but Comparative Examples 1 to 8 outside the present invention have problems in at least any of the characteristics and are put into practical use. You can see that it is not at a possible level.

a1 Hydrophobic Resin Part a2 Hydrophilic Resin Part a3 Resin Particles Containing Hydrophilic Resin and Hydrophobic Resin b1 Colorant Particles b2 Aggregated Particles c1 Fusing / Aging Process Particles c2 Fusing / Aging Process Particles c3 Core Particle Surface Part c4 core particle central part c5 toner particle core part d1 shell d2 toner particle (toner base)

Claims (4)

  In the electrostatic latent image developing toner having a core-shell structure, the core portion includes at least a hydrophobic resin having a glass transition temperature (Tg) of 10 to 30 ° C., and a hydrophilic resin having a glass transition temperature (Tg) of 40 to 50 ° C. It contains a colorant, and there are many low Tg hydrophobic resins in the center of the core part, and the ratio of the high Tg hydrophilic resin increases from the center to the outside, and the Tg of the shell part is 50-70. An electrostatic latent image developing toner comprising a hydrophilic resin at 0 ° C.   The glass transition temperature (Tg) of the hydrophobic resin in the core portion is 15 to 25 ° C., the glass transition temperature (Tg) of the hydrophilic resin is 42 to 47 ° C., and the glass transition temperature of the hydrophobic resin in the shell portion ( The toner for developing an electrostatic latent image according to claim 1, wherein Tg) is 55 to 65 ° C.   The content of the hydrophobic resin in the core part is 80 to 90% by mass of the core part resin, the content of the hydrophilic resin is 10 to 20% by mass, and the content of the hydrophilic resin in the shell part is the total content of the toner. The toner for developing an electrostatic latent image according to claim 1, wherein the toner is 5 to 10% by mass of the resin.   The toner for developing an electrostatic latent image according to any one of claims 1 to 3, and at least the steps of forming a latent image on an electrophotographic photosensitive member, developing, transferring to a recording paper, and heat fixing. An image forming method.

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