Two-component developer for electrostatic charge image development, electrophotographic image forming method, and electrophotographic image forming apparatus

Abstract

To provide a two-component developer, an electrophotographic image forming method, and an electrophotographic image forming apparatus that improve the charge rising characteristics of toner corresponding to high-speed printing, and can achieve the stable amount of charge of toner even under environmental variations, thereby stably outputting high-quality images during continuous printing.SOLUTION: A two-component developer for electrostatic charge image development of the present invention contains: a toner particle that includes a toner base particle and an external additive arranged on a surface of the toner base particle; and a carrier particle that has a core material particle and a coating part arranged on a surface of the core material particle. The external additive contains inorganic fine particles that are surface-modified by a surface modifier represented by the following general formula (1), and a value of the content of iron element (atomic%) in a surface of the carrier particle satisfies the following formula (1). General formula (1): (R1)4-n-Si-(X)n; formula (1) 4.0≤{AFe / (AC+AO+AFe)}×100≤15.0.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a two-component developer for electrostatic charge image development, an electrophotographic image forming method using the same, and an electrophotographic image forming apparatus. More specifically, the present invention relates to a two-component developer for electrostatic charge image development that improves the charging rise property of toner corresponding to high-speed printing, and further, even under environmental variations, the charge amount of the toner is stable, and a high-quality image can be stably output during continuous printing.

Background Art

[0002] As copiers and printers have become widespread, higher performance has been demanded for toners for electrostatic charge image development used in printing (hereinafter, also simply referred to as "toners"). In recent years, digital printing technology called print-on-demand (POD) that directly prints without a plate-making process has attracted attention. Since the POD can handle both small-lot printing and variable printing in which the printed content is changed for each sheet, it is more user-friendly than conventional offset printing, and further, the demand for high-speed printing and energy-saving measures is increasing.

[0003] For high-speed printing and energy-saving measures, it is necessary to improve the charging rise property of the toner in order to obtain a desired toner charge amount by friction in a very short time. Further, as a measure for high reliability related to toner charging, stable toner charge amount control is required so that the toner charge amount at the developing portion always falls within the set range allowed in the process. Furthermore, under high humidity conditions, the toner charge amount decreases, and the toner develops white areas (also referred to as "fogging"), and during drying, problems such as a decrease in image quality density due to overcharging (also referred to as "overcharge") occur. Therefore, in order to cope with environmental variation stability, it is required to reduce the variation in the toner charge amount. In toner manufacturing, it has become an urgent task to develop high-quality toners in which the charging characteristics are highly controlled in this way.

[0004] In order to solve this problem, it has been proposed to stabilize the charge amount by using silica treated with an alkylalkoxysilane having a relatively long carbon number (see, for example, Patent Document 1). However, silica particles treated with an alkylalkoxysilane having a relatively long carbon number have a high adhesiveness to containers and the like, and when used in toner, the toner fluidity tends to decrease. Further, since the charge rise is slow, when continuously printing images with a high printing rate, it does not rise to the desired charge amount and becomes a low charge state, so there has been a problem that the image quality is likely to deteriorate.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The present invention has been made in view of the above problems and situations, and the problem to be solved is to improve the charge rising property of toner corresponding to high-speed printing, and further, even under environmental fluctuations, the charge amount of toner is stable, and a two-component developer for electrostatic charge image development, an electrophotographic image forming method, and an electrophotographic image forming apparatus that can stably output high-quality images during continuous printing are provided.

Means for Solving the Problems

[0007] In order to solve the above problems, the present inventor, in the process of examining the causes of the above problems, is composed of toner particles containing toner base particles and external additives, and carrier particles containing core particles having a coating portion, and the external additive contains inorganic fine particles surface-modified with a specific surface modifier, and the present invention has been achieved by finding that the above problems can be solved by a two-component developer for electrostatic charge image development in which the iron element content ratio derived from the core particles on the surface of the carrier particles is within a specific range.

[0008] That is, the above problems according to the present invention are solved by the following means.

[0009] 1. A two-component developer for electrostatic charge image development containing toner particles including toner base particles and external additives disposed on the surface of the toner base particles, and carrier particles having core particles and a coating portion disposed on the surface of the core particles, wherein the external additive contains silica particles surface-modified with a surface modifier represented by the following general formula (1) sub and a two-component developer for electrostatic charge image development, characterized in that the value of the iron element content (atomic%) measured by X-ray photoelectron spectroscopy (XPS) on the surface of the carrier particles satisfies the following formula (1). General formula (1): (R1) 4-n -Si-(X) n 〔R1 represents ethyl group, n-propyl group or n-butyl group . X is a halogeno group or an alkoxy group, which may be the same or different from each other. n represents an integer from 1 to 3.〕 Formula (1) 8.0 ≦{A Fe / (A C +A O +A Fe )}×100≦15.0 (However, A Fe , A C and A O each represent the content (atomic%) of Fe, C and O in the unit area of the surface of the carrier particles.)

[0011] 2 . The two-component developer for electrostatic charge image development according to claim 1, characterized in that the shape factor (SF-1) of the core particles is in the range of 115 to 150. in the item described two-component developer for electrostatic charge image development.

[0012] 3 . The two-component developer for electrostatic charge image development according to claim 1, characterized in that the toner base particles have a core-shell structure. or Item in item 2 described two-component developer for electrostatic charge image development.

[0013] 4. The core - shell structure is characterized in that the core part is mainly composed of an amorphous vinyl resin and the shell part is mainly composed of an amorphous polyester resin, and it is the second 3 component developer for electrostatic charge image development according to the item described.

[0014] 5 . An electrophotographic image forming method having at least a charging step of an image carrier, an electrostatic charge image forming step, an electrostatic charge image developing step, a toner image transfer step, a toner image fixing step, and a cleaning step, using the two - component developer for electrostatic charge image development according to any one of claims 1 to 4 the item described.

[0015] 6 . An electrophotographic image forming apparatus comprising at least a charging means of an image carrier, an electrostatic charge image forming means, an electrostatic charge image developing means, a toner image transfer means, a toner image fixing means, and a cleaning means, using the two - component developer for electrostatic charge image development according to any one of claims 1 to 4 the item described.

Advantages of the Invention

[0016] By the above - mentioned means of the present invention, it is possible to provide a two - component developer for electrostatic charge image development, an electrophotographic image forming method, and an electrophotographic image forming apparatus that improve the charging rise property of the toner corresponding to high - speed printing, and in which the charge amount of the toner is stable even under environmental variations, and a high - quality image can be stably output during continuous printing.

[0017] Regarding the mechanism or working mechanism for the manifestation of the effects of the present invention, it is not clearly defined, but it is speculated as follows.

[0018] The two-component developer for electrostatic charge image development of the present invention contains toner particles including toner base particles and external additives disposed on the surface of the toner base particles, and the external additives contain inorganic fine particles surface-modified with an alkylalkoxysilane-based surface modifier represented by the general formula (1) and having a linear alkyl group with 1 to 4 carbon atoms.

[0019] Treatments such as hexamethyldisilazane (HMDS) treatment, which is a commonly used surface modifier, have low adhesion force, enabling high fluidization of the toner. However, due to the weak adhesion force to the toner mother particles, there is a problem of causing a decrease in charge amount due to carrier contamination. In addition, in the case of a single-chain treatment agent such as the HMDS, since water molecules easily approach the unreacted OH groups, charge leakage occurs, and particularly in a high-temperature and high-humidity environment, the charge amount tends to decrease.

[0020] On the other hand, when improving the adhesion force to the toner base particles by alkylalkoxysilane treatment or the like, it is necessary to efficiently construct a state in which electron transfer such as polar groups easily occurs for charge control. However, when a long-chain alkyl group is introduced, although the approach of water molecules can be prevented, since the long-chain alkyl group directly triboelectrically charges rather than the OH group contacting the carrier, there is a tendency to easily cause overcharging particularly in a low-temperature and low-humidity environment.

[0021] Therefore, as a result of considering and examining that it is necessary to construct an environment in which the OH group directly contacts the carrier by eliminating the influence of water, it has been found that treating the surface of the external additive with an alkoxysilane or a halogenated silane having a linear alkyl group with 1 to 4 carbon atoms is preferable with respect to chargeability.

[0022] The two-component developer for electrostatic charge image development of the present invention further contains the toner particles, core particles, and carrier particles having a coating portion disposed on the surface of the core particles, and the value of the iron element content rate (atomic%) derived from the core particles measured by X-ray photoelectron spectroscopy (XPS) on the surface of the carrier particles is in the range of 4.0 to 15.0.

[0023] When the outermost surface of the carrier particles is coated with resin, the added external additives in contact are likely to be overcharged, and as a result, the charge amount of the toner is also likely to be overcharged. The state of overcharging, that is, a state where the saturation charge amount value is high, means that the toner and the carrier particles are strongly electrostatically attached, so the replaceability of the toner deteriorates, and the charge amount distribution of the toner tends to spread. Along with this, there is a problem that a concentration change is likely to occur significantly.

[0024] On the other hand, when the core material particles are exposed on the surface of the carrier particles, charge leakage can occur through discharge from the core material particles during triboelectric charging, so the above overcharging can be suppressed. However, if the exposed area of the core material particles is too large, the resistance becomes low and charge leakage is likely to occur. Therefore, it has been found that by controlling the exposed area of the core material particles within a certain range, the charging rise property of the toner can be improved. In the present invention, the exposed area of the core material particles can be controlled by adjusting the value of the iron element content rate (atomic%) measured by X-ray photoelectron spectroscopy (XPS) on the surface of the carrier particles represented by the above formula (1).

[0025] The above formula (1) represents the relationship of the iron element content rate on the surface of the carrier particles. The main atoms on the surface of the carrier particles are carbon, oxygen, and iron. Carbon mainly comes from the resin. In the present invention, since an iron oxide-based material is used as the core material particles, iron mainly comes from the core material. Formula (1) represents the ratio of iron among the main atoms (carbon, oxygen, and iron) on the surface of the carrier particles. By setting this ratio within a specific range, the core material particles are appropriately exposed on the surface of the carrier.

[0026] From the above, by treating the surface of the external additive with an alkoxysilane or a halogenated silane having a linear alkyl group with 1 to 4 carbon atoms, and controlling the exposed area of the core material particles in the carrier particles having a coating portion, a two-component developer for electrostatic charge image development can be obtained that improves the charging rise property and stabilizes the charge amount of the toner even under environmental variations such as humidity.

Brief Description of the Drawings

[0027] [[Figure 1]] Schematic diagram showing the structure of the electrophotographic image forming apparatus of the present invention

Mode for Carrying Out the Invention

[0028] The two-component developer for electrostatic charge image development of the present invention contains toner particles including toner base particles and external additives disposed on the surface of the toner base particles, and carrier particles having core particles and a coating portion disposed on the surface of the core particles. The external additives contain inorganic fine particles surface-modified with a surface modifier represented by the general formula (1), and the value of the iron element content rate (atomic%) measured by X-ray photoelectron spectroscopy (XPS) on the surface of the carrier particles satisfies the formula (1). This feature is a technical feature common to or corresponding to the following embodiments.

[0029] As an embodiment of the present invention, it is preferable that the external additive is silica particles, alumina particles, or titanate compound particles from the viewpoints of the charging startability of the toner and the improvement of the stability and fluidity of the charging amount of the toner under environmental variations.

[0030] Also, it is preferable that the shape factor (SF-1) of the core particles is in the range of 115 to 150 from the viewpoints of improving the stability of the charging amount of the toner under environmental variations and the transportability of the toner to the development nip portion.

[0031] It is preferable that the toner base particles have a core-shell structure, and in the core-shell structure, the core portion is mainly composed of an amorphous vinyl resin and the shell portion is mainly composed of an amorphous polyester resin from the viewpoints of the low-temperature fixability of the toner and the improvement of the stability of the charging amount of the toner under environmental variations.

[0032] The electrophotographic image forming method of the present invention (hereinafter, also referred to as "image forming method") is an electrophotographic image forming method having at least a charging step of an image carrier, an electrostatic latent image forming step, an electrostatic latent image developing step, a toner image transfer step, and a toner image fixing step, and is characterized by using the two-component developer for electrostatic latent image development of the present invention.

[0033] Further, the electronic image forming apparatus of the present invention (hereinafter, also referred to as "image forming apparatus") is an electrophotographic image forming apparatus including at least a charging means for an image carrier, an electrostatic latent image forming means, an electrostatic latent image developing means, a toner image transfer means, and a toner image fixing means, and is characterized by using the two-component developer for electrostatic latent image development of the present invention.

[0034] Hereinafter, the present invention, its components, and embodiments and modes for carrying out the present invention will be described in detail. In the present application, "~" is used to mean including the numerical values described before and after as a lower limit value and an upper limit value.

[0035] ≪Outline of the two-component developer for electrostatic latent image development of the present invention≫ The two-component developer for electrostatic latent image development of the present invention (hereinafter, may be simply referred to as "two-component developer") contains toner particles including toner base particles and external additives disposed on the surface of the toner base particles, and carrier particles having core particles and a coating portion disposed on the surface of the core particles, and is a two-component developer for electrostatic latent image development, The external additive contains inorganic fine particles surface-modified with a surface modifier represented by the following general formula (1), and the value of the iron element content rate (atomic%) measured by X-ray photoelectron spectroscopy (XPS) on the surface of the carrier particles satisfies the following formula (1). General formula (1): (R1) 4-n -Si-(X) n 〔R1 represents a linear alkyl group having 1 to 4 carbon atoms which may have a substituent. X is a halogeno group or an alkoxy group, and they may be the same or different from each other. n represents an integer from 1 to 3.〕 Formula (1) 4.0 ≦ {A Fe / (A C +AO +A Fe )}×100 ≦ 15.0 (However, A Fe , A C and A O represent the contents (atomic %) of Fe, C, and O on the unit area of the carrier particle surface, respectively.)

[0036] The two-component developer for electrostatic charge image development of the present invention (hereinafter also referred to as "toner") contains toner particles including toner base particles and external additives disposed on the surface of the toner base particles.) In this specification, the "toner base particles" constitute the base of the "toner particles". The "toner base particles" according to the present invention contain at least a binder resin, and may contain other constituent components such as a colorant, a release agent (wax), a charge control agent, etc. as required. The "toner base particles" are referred to as "toner particles" by adding external additives. And the "toner" refers to an aggregate of toner particles.)

[0037] Furthermore, the two-component developer for electrostatic charge image development of the present invention contains, in addition to the toner particles, core particles and carrier particles having a coating portion disposed on the surface of the core particles, and constitutes a two-component developer.)

[0038] First, the constituent elements of the present invention will be described in detail starting from the carrier particles.) [1] Carrier particles The two-component developer for electrostatic charge image development of the present invention is used as a two-component developer by mixing toner particles and carrier particles. Examples of carrier particles include magnetic particles made of conventionally known materials such as metals such as iron, ferrite, magnetite, and alloys of these metals with metals such as aluminum and lead. Examples of carrier particles include coated carrier particles having a core material particle made of a magnetic material and a coating material covering the surface of the core material particle as a coating portion, and resin-dispersed type carrier particles in which fine powder of a magnetic material is dispersed in a resin. From the viewpoint of suppressing the adhesion of carrier particles to the photoreceptor, coated carrier particles are preferred, and the carrier particles according to the present invention are coated carrier particles.)

[0039] The core material particles are, for example, magnetic materials that are strongly magnetized in that direction by a magnetic field. The magnetic material may be used alone or in combination of two or more kinds. Examples of the magnetic material include metals showing ferromagnetism such as iron, nickel and cobalt, alloys or compounds containing these metals, and alloys showing ferromagnetism by heat treatment.

[0040] Examples of the metal showing ferromagnetism or the compound containing the same include iron, ferrite represented by the following formula (a), and magnetite represented by the following formula (b). In formula (a) and formula (b), M represents one or more monovalent or divalent metals selected from, for example, manganese (Mn), magnesium (Mg), strontium (Sr), calcium (Ca), titanium (Ti), copper (Cu), zinc (Zn), nickel (Ni), aluminum (Al), silicon (Si), zirconium (Zr), bismuth (Bi), cobalt (Co), lithium (Li), etc.

[0041] MO·Fe2O3 Formula (a) MFe2O4 Formula (b)

[0042] Examples of the alloy showing ferromagnetism include Heusler alloys such as manganese - copper - aluminum and manganese - copper - tin, and chromium dioxide.

[0043] The core material particles are preferably various ferrites. The specific gravity of the coated carrier particles is smaller than the specific gravity of the metal constituting the core material particles. Therefore, various ferrites can reduce the impact force of stirring in the developing device more.

[0044] The coating portion is disposed on the surface of the core material particles. The coating portion has a coating material. The coating material may be used alone as one type, or two or more types may be used in combination. As the coating material, known resins used for coating the core material particles in the carrier particles can be used. Examples of the resin used as the coating material include polyolefin resins such as polyethylene and polypropylene; polystyrene resin; (meth)acrylic resins such as polymethyl methacrylate, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride and polyvinylidene resins; copolymer resins such as vinyl chloride-vinyl acetate copolymer and styrene-acrylic acid copolymer; silicone resins composed of organosiloxane bonds or modified resins thereof; fluorine resins such as polyvinyl fluoride; polyamide resins; polyester resins; polyurethane resins; amino resins such as urea-formaldehyde resins; and epoxy resins. Examples of the modified resin include modified resins with alkyd resins, polyester resins, epoxy resins, polyurethane, etc.

[0045] From the viewpoints of reducing the moisture adsorption of the carrier particles and enhancing the adhesion between the core material particles in the coating portion, the resin used as the coating material is preferably a resin having a cycloalkyl group. Examples of the cycloalkyl group include cyclohexyl group, cyclopentyl group, cyclopropyl group, cyclobutyl group, cycloheptyl group, cyclooctyl group, cyclononyl group and cyclodecyl group. The cycloalkyl group is preferably a cyclohexyl group or a cyclopentyl group, and more preferably a cyclohexyl group from the viewpoint of the adhesion between the coating portion and the core material particles.

[0046] The weight average molecular weight (Mw) of the resin having a cycloalkyl group is preferably from 10,000 to 800,000, more preferably from 100,000 to 750,000. The content of the structural unit containing a cycloalkyl group in the resin is, for example, 10 to 90% by mass. The content of the cycloalkyl group in the resin can be determined by known instrumental analysis methods such as P-GC / MS and 1 1H-NMR.

[0047] When the core particles of the carrier particles according to the present invention are coated with resin, toner does not scatter and a stable image density can be obtained. However, when the core particles are completely coated with resin, the core particles made of a magnetic material are not exposed, so the resistance of the carrier particles increases. Therefore, the carrier particles need to be initially coated with resin so that the core particles are moderately exposed.

[0048] The exposed area (degree of exposure) of the core particles on the surface of the carrier particles according to the present invention is achieved by adjusting the value of the iron element content (atomic%) measured by X-ray photoelectron spectroscopy (XPS) on the surface of the carrier particles so as to satisfy the following formula (1). Formula (1) 4.0 ≦ {A Fe / (A C + A O + A Fe )} × 100 ≦ 15.0 (However, A Fe , A C and A O represent the contents (atomic%) of Fe, C, and O in the unit area of the surface of the carrier particles, respectively.)

[0049] Here, "initial" means the stage of mixing toner particles and carrier particles to produce a two-component developer for electrostatic charge image development. When the value of the iron element content is less than 4.0 atomic%, the resistance value of the carrier particles becomes too high, the electrostatic adhesion force between the carrier particles and the toner particles increases, the replaceability of the toner particles deteriorates, and fogging and image quality degradation occur. On the other hand, when the value of the iron element content exceeds 15.0 atomic%, the resistance value of the carrier particles themselves decreases, the charge amount of the toner particles becomes low, and image quality deterioration occurs.

[0050] In addition, when the material of the core particles is other than the iron oxide type, similarly, in the main element contained in the material of the core particles, by setting the value of the element content shown below within a specific range, the core particles are moderately exposed on the surface of the carrier, and the same effect is considered to be obtained.

[0051] The following formula (2) represents the proportion of iron (also referred to as the "iron element content rate") among the main elements (carbon, oxygen, and iron) on the surface of the carrier particles. By setting this proportion within a specific range, the core material particles are moderately exposed on the surface of the carrier particles.

[0052] Formula (2) Iron element content rate (atomic%) = A Fe / (A C + A O + A Fe ) (where A Fe , A C and A O represent the contents (atomic%) of Fe, C, and O per unit area on the surface of the carrier particles, respectively.)

[0053] The iron element content rate represented by formula (2) can be measured by the following method. In the surface element composition analysis by X-ray photoelectron spectroscopy (XPS measurement), for carbon, the C1s spectrum is measured, for iron, the Fe2p 3 / 2 spectrum is measured, and for oxygen, the O1s spectrum is measured. Based on the spectra of these respective elements, the contents (atomic%) of Fe, C, and O per unit area on the carrier surface, represented by "A C ", "A O ", and "A Fe " are obtained and calculated from formula (2).

[0054] Note that as the XPS measurement device, Thermo Fisher Scientific's K-Alpha is used. The measurement is performed using Al monochromatic X-rays as the X-ray source, with the acceleration voltage set to 7 kV and the emission current set to 6 mA.

[0055] The volume-average particle diameter of the carrier particles is preferably in the range of 20 to 100 μm, more preferably in the range of 25 to 80 μm, based on the volume-based median diameter. The volume-based median diameter of the carrier particles can be measured, for example, using a laser diffraction particle size distribution measuring device (HELOS; SYMPATEC Co., Ltd.) equipped with a wet disperser or the method for measuring the volume-based median diameter of toner particles described below.

[0056] The shape factor (SF-1) of the core material particles is preferably 115 or more and 150 or less. When the shape factor is 115 or more, since the shape of the measured particles does not become close to a perfect sphere, the bulk density (g / cc) of the carrier does not increase too much, and the two-component developer for electrostatic charge image development is not excessively conveyed to the development nip portion, and there is an advantage that fogging and toner scattering are less likely to occur.

[0057] On the other hand, when the shape factor is 150 or less, the unevenness on the surface of the core material particles is moderate and voids are less likely to occur inside the core material particles. Therefore, the core material particles can suppress the water content according to the humidity. Accordingly, there is no significant decrease in the charge retention ability due to the decrease in the resistance value per particle caused by the water, and the occurrence of defects such as fogging development can be suppressed.

[0058] Further, since the surface of the core material particles has appropriate unevenness within the above range, in the carrier coated with the resin, the value of the iron element content represented by the formula (2) can be adjusted within the above range. Note that by increasing the shape factor, the unevenness of the core material particles becomes larger, so the core material particles are more likely to be exposed, and the value of the iron element content represented by the formula (2) also becomes larger.

[0059] The shape factor of the core material particles is measured by the following method. The carrier core material is randomly photographed at a magnification of 150 times with a scanning electron microscope to obtain photos of 100 or more particles, and the photographed image captured by the scanner is used with an image processing analyzer LUZEX AP (manufactured by Nireco Corporation) to measure the maximum length and projected area of the core material particles. The "maximum length" refers to the maximum spanning length of the particle image. The shape factor is a value calculated by the average value of the shape factor SF-1 calculated by the above formula for 100 core material particles. Formula (3) SF-1 = (maximum length of the particle) 2 / (projected area of the particle) × (π / 4) × 100

[0060] As a method for producing core material particles with a shape factor of about 115 to 150, in the firing process, it is preferable to set the firing temperature higher than before, such as 1300 to 1500 °C.

[0061] The dynamic resistivity of the carrier particles is preferably 1.0×10 8 Ω·cm or more and 1.0×10 11 Ω·cm or less. When the dynamic resistivity of the carrier particles is 1.0×10 8 Ω·cm or more, the charge retention ability of the carrier particles themselves does not decrease, and the charge amount of the toner particles can be maintained. On the other hand, when the dynamic resistivity of the carrier particles is 1.0×10 11 Ω·cm or less, the charge of the opposite pole to the toner particles on the carrier particles is not accumulated, the electrostatic adhesion force between the toner particles and the carrier particles becomes appropriate, and the replaceability of the toner particles is improved. Therefore, it is possible to suppress the occurrence of fogging and image quality degradation.

[0062] The dynamic resistivity of the carrier particles is obtained by the following formula (4) by replacing the aluminum electrode drum with the same dimensions as the photoreceptor drum with the photoreceptor drum, supplying carrier particles onto the developing sleeve to form a magnetic brush, rubbing this magnetic brush against the electrode drum, and measuring the current flowing between the two by applying a voltage (500 V) between the sleeve and the photoreceptor drum.

[0063] Equation (4) DVR (Ω·cm) = (V / I) × (N × L / Dsd)

[0064] DVR: Carrier resistance (Ω·cm) V: Voltage between the developing sleeve and the drum (V) I: Measured current value (A) N: Developing nip width (cm) L: Developing sleeve length (cm) DSD: Distance between the developing sleeve and the photoreceptor drum (cm)

[0065] For example, it can be measured with V = 500V, N = 1cm, L = 6cm, and Dsd = 0.6mm.

[0066] Examples of the method for manufacturing coated carrier particles having core material particles and a coating part include the wet coating method and the dry coating method. Examples of the wet coating method include the fluidized bed spray coating method, the dipping coating method, and the polymerization method.

[0067] The "fluidized bed spray coating method" is a method in which a coating solution obtained by dissolving a resin used as a coating material in a solvent is spray-coated onto the surface of magnetic particles using a fluidized bed, and then dried to form a coating part. The "dipping coating method" is a method in which magnetic particles are immersed in a coating solution obtained by dissolving a resin used as a coating material in a solvent for coating treatment, and then dried to form a coating part. The "polymerization method" is a method in which magnetic particles are immersed in a coating solution obtained by dissolving a reactive compound in a solvent for coating treatment, and then heat or the like is applied to carry out a polymerization reaction to form a coating part.

[0068] The "dry coating method" is a method in which a resin used as a coating material is adhered to the surface of core material particles, and then mechanical impact force is applied to melt or soften the resin adhered to the surface of the core material particles and fix it to form a coated portion. Specifically, the core material particles, the resin used as the coating material, and the low-resistance fine particles are mixed using a high-speed stirring mixer capable of applying mechanical impact force under non-heating or heating conditions, and are stirred at high speed to repeatedly apply impact force to the mixture, and a carrier dissolved or softened and fixed on the surface of the magnetic particles is produced. As coating conditions, when heating, 80 to 130 °C is preferable, the wind speed causing the impact force is preferably 10 m / s or more during heating, and preferably 5 m / s or less during cooling from the viewpoint of suppressing aggregation of the carrier particles. The time for applying the impact force is preferably 20 to 60 minutes.

[0069] By mixing the toner particles and the carrier particles according to the present invention, a two-component developer can be obtained. The mixing device used during mixing is not particularly limited. Examples of the mixing device include a Nauta mixer, a W cone, and a V-type mixer. The content (toner concentration) of the toner particles in the two-component developer for electrostatic charge image development is not particularly limited, but is preferably 4.0 to 8.0% by mass.

[0070] [2] Toner particles The two-component developer for electrostatic charge image development of the present invention contains toner particles including toner base particles and external additives disposed on the surface of the toner base particles.

[0071] [2.1] External additives The external additive according to the present invention contains inorganic fine particles surface-modified with a surface modifier represented by the following general formula (1). General formula (1): (R1) 4-n -Si-(X) n [R1 represents a linear alkyl group having 1 to 4 carbon atoms which may have a substituent. X is a halogeno group or an alkoxy group, and they may be the same or different from each other. n represents an integer from 1 to 3. ]

[0072] The rise of charging is effectively achieved by using polar groups where electron transfer is likely to occur. However, in the case of short-chain surface modifiers such as HMDS treatment, water molecules can easily approach the unreacted OH groups on the surface of the external additive, so charge leakage occurs preferentially rather than the rise of charging.

[0073] On the other hand, when introducing long-chain alkyl groups (C6~), the approach of water molecules can be prevented. However, since high-resistance alkyl groups are introduced on the outermost surface, the probability of triboelectric charging between the long-chain alkyl groups and the carrier increases, and the transfer of electrons occurs less chain-like, resulting in a slower rise of charging.

[0074] Alkoxysilanes or halogenated silanes having linear alkyl groups within the range of 1 to 4 carbon atoms can suppress the approach of water molecules due to the steric structure of the alkyl group, halogeno group, and alkoxy group, and the electron transfer from the alkyl group to the polar group becomes smooth by forming a hydrogen bond network between the alkoxy group and the unreacted OH group, significantly improving the charging rise property.

[0075] In addition, when the external additive in contact with the resin coating part on the outermost surface of the carrier particles adheres electrostatically, the fluidity of the carrier particles is improved, the number of triboelectric charging times per unit time with toner or external additive increases, and the charging rise speed becomes faster, but the saturation charge amount value tends to be higher. On the other hand, when the carrier core particles are exposed, excess charges can be discharged by charge leakage, suppressing overcharging.

[0076] As the inorganic fine particles, the external additive according to the present invention can use conventionally known metal oxide particles, such as silica particles, alumina particles, titanate compound particles, zirconia particles, zinc oxide particles, chromium oxide particles, cerium oxide particles, antimony oxide particles, tungsten oxide particles, tin oxide particles, tellurium oxide particles, manganese oxide particles, and boron oxide particles, etc. These may be used alone or in combination of two or more.

[0077] Among them, silica particles, alumina particles, or titanate compound particles are preferable. Silica particles are effective in improving toner fluidity, and thus have good charge rising properties and are likely to be charged uniformly. On the other hand, since titania particles have low resistance, they have good charge rising properties, but there is a problem that charge retention becomes difficult in a high-temperature and high-humidity environment and the charge amount decreases. Alumina particles and titanate compound particles have the characteristics that their resistance is sufficiently lower than that of silica particles and higher than that of titania particles. Therefore, compared with silica particles, charge transfer is likely to occur, the charge rising is good, and since the resistance is higher than that of titania particles, charge leakage is also unlikely to occur, so that uniformization of the toner charge amount can be realized.

[0078] (Silica particles) Silica produced by a known method such as the sol-gel method, the vapor phase method, or the melting method can be used. The production method of silica by the sol-gel method is a method of generating silane particles by reacting tetraalkoxysilane as a raw material while supplying tetraalkoxysilane and an alkali catalyst as a catalyst in the presence of an alcohol containing an alkali catalyst. It has the characteristic that it is easy to control the particle size distribution and shape.

[0079] The vapor phase method (gas combustion method) synthesizes silica by vaporizing silicon chloride and performing a gas phase reaction in a high-temperature hydrogen flame. In the melting method, a mixed raw material composed of finely pulverized quartz silica, a reducing agent such as metal silicone powder or carbon powder, and water for making it into a slurry is heat-treated at a high temperature in a reducing atmosphere to generate SiO gas, and it is rapidly cooled in an atmosphere containing oxygen to obtain it.

[0080] (Alumina particles) Alumina refers to aluminum oxide represented by Al2O3, and its forms such as α-type, γ-type, σ-type, and their mixtures are known. As for the shape, it ranges from cubic to spherical by controlling its crystal system. Alumina can be produced by known methods. As a method for producing alumina, the Bayer process is common, but in order to obtain high-purity and nano-sized alumina, hydrolysis methods, vapor-phase synthesis methods, flame hydrolysis methods, underwater spark discharge methods, etc. can be mentioned.

[0081] (Titanate compound particles) As the titanate compound used in the titanate compound particles according to the present invention, for example, a compound represented by the following general formula called so-called metatitanate formed from titanium(IV) oxide and other metal oxides or metal carbonates is a typical one.

[0082] General formula (2) MI2TiO3 or MIITiO3 (In the formula, MI represents a monovalent metal atom, and MII represents a divalent metal atom.)

[0083] The titanate compound that can be used in the present invention is preferably a titanate compound having a structure bonded to a divalent metal atom represented by MIITiO3. Specific examples of the titanate compound bonded to a divalent metal atom include, for example, calcium titanate (CaTiO3), magnesium titanate (MgTiO3), strontium titanate (SrTiO3), barium titanate (BaTiO3), etc. Among these titanate compounds bonded to a divalent metal atom, from the viewpoints of environmental impact, etc. and maintaining the charge amount at a certain level over a long period, calcium titanate (CaTiO3) is preferred.

[0084] The titanate compound that can be used in the present invention can be produced by a known method. As a method for producing the titanate compound that can be used in the present invention, for example, there is a method of producing through a titanium(IV) oxide compound TiO2·H2O having a hydrated form called metatitanic acid. This method is a method of reacting the titanium(IV) oxide compound with a metal carbonate salt such as calcium carbonate or a metal oxide, and then generating a titanate compound typified by calcium titanate through a firing treatment. Incidentally, the hydrolyzate of titanium oxide such as metatitanic acid is also called a mineral acid peptized product and has a form of a liquid in which titanium oxide particles are dispersed. A water-soluble metal carbonate salt or metal oxide is added to the mineral acid peptized product composed of this titanium oxide hydrolyzate, and the mixture is heated to 50 °C or higher and reacted while adding an aqueous alkali solution to produce a titanate compound.

[0085] One representative example of the mineral acid peptized product, metatitanic acid, has a sulfurous acid SO3 content of 1.0 mass% or less, preferably 0.5 mass% or less, and is peptized by adjusting the pH to 0.8 to 1.5 with hydrochloric acid.

[0086] As the aqueous alkali solution used for producing the titanate compound, a caustic aqueous alkali solution typified by an aqueous sodium hydroxide solution is preferred. Further, examples of the compound that reacts with the hydrolyzate of titanium oxide include nitrate compounds, carbonate compounds, chloride compounds, etc. of strontium, magnesium, calcium, barium, aluminum, zirconium, sodium, etc.

[0087] In the manufacturing process of the titanate compound particles, the particle size of the titanate compound particles can be controlled by adjusting the addition ratio of the hydrate or hydrolyzate of titanium oxide and the metal oxide, etc., the concentration of the titanium oxide hydrate or hydrolyzate during the reaction, the temperature and addition rate when adding the aqueous alkali solution, etc. Also, in order to prevent the generation of carbonate compounds in the reaction process, it is preferable to carry out the reaction in a nitrogen gas atmosphere.

[0088] When adding the aqueous alkali solution, the higher the temperature, the more crystalline product can be obtained. Practically, a range of 50°C or higher and 101°C or lower is appropriate. Also, the addition rate of the aqueous alkali solution tends to affect the particle size of the resulting titanate compound particles. The slower the addition rate, the larger the particle size of the titanate compound particles obtained, and the faster the addition rate, the smaller the particle size formed. The addition rate of the aqueous alkali solution is 0.001 to 1.0 equivalent / hour, preferably 0.005 to 0.5 equivalent / hour, based on the charged raw materials, and can be appropriately adjusted according to the desired particle size. The addition rate of the aqueous alkali solution can also be changed during the process according to the purpose.

[0089] The toner of the present invention may further contain other known external additives as external additives. Also, these inorganic fine particles may be subjected to surface treatment such as gloss treatment or hydrophobization treatment with a silane coupling agent, a titanium coupling agent, a higher fatty acid, a silicone oil, etc. for improving heat-resistant storage stability, environmental stability, etc.

[0090] Furthermore, organic fine particles can also be used as other external additives. Specifically, organic fine particles made of homopolymers or copolymers of styrene, methyl methacrylate, etc. can be used.

[0091] A lubricant can also be used as an external additive. The lubricant is used for the purpose of further improving cleaning performance and transfer performance. Specifically, salts of zinc, aluminum, copper, magnesium, calcium, etc. of stearic acid, salts of zinc, manganese, iron, copper, magnesium, etc. of oleic acid, salts of zinc, copper, magnesium, calcium, etc. of palmitic acid, salts of zinc, calcium, etc. of linoleic acid, salts of zinc, calcium, etc. of ricinoleic acid, etc., i.e., metal salts of higher fatty acids, can be mentioned.

[0092] (External addition treatment) For the external addition mixing process of the external additive to the toner base particles described below, a mechanical mixing device can be used. As the mechanical mixing device, a Henschel mixer, a Nauta mixer, a Turbular mixer, etc. can be used. Among these, a mixing device that can apply shear force to the particles to be processed, such as a Henschel mixer, can be used to perform mixing processes such as increasing the mixing time or increasing the rotational peripheral speed of the stirring blades. Further, when using multiple types of external additives, all the external additives can be mixed with the toner particles at once, or they can be mixed in multiple batches according to the external additives.

[0093] The mixing method of the external additive can control the degree of fragmentation and adhesion strength of the external additive by using the above mechanical mixing device to control the mixing intensity, that is, the peripheral speed of the stirring blades, the mixing time, or the mixing temperature, etc.

[0094] The total amount of the addition amount of these external additives is preferably in the range of 0.1 to 10% by mass, more preferably in the range of 1 to 5% by mass, based on 100 parts by mass of the toner base particles.

[0095] 〔2.2〕Toner base particles The toner base particles according to the present invention preferably contain a vinyl-based resin as an amorphous resin as the binder resin at least from the viewpoints of low-temperature fixability of the toner and improvement in the stability of the charge amount of the toner under environmental variations. That is, it is preferable that the toner base particles contain a binder resin having a vinyl group.

[0096] To incorporate a binder resin having a vinyl group into the toner base particles, an embodiment in which the toner base particles have a core-shell structure, the core part is mainly composed of an amorphous vinyl resin, and the shell part is mainly composed of an amorphous polyester resin can be cited as a preferred example.

[0097] That is, the toner base particles preferably have a core-shell structure. By adopting a core-shell structure, an interface exists between the core and the shell. Therefore, when the incompatibility is high, the charges generated during toner charging can be efficiently trapped to prevent charge leakage, and by increasing the compatibility, the degree of charge leakage can be controlled. Note that the shell portion is not limited to completely covering the core particles, and a part of the surface of the core particles may be exposed. The core-shell structure can be confirmed, for example, by observing the structure of the cross-section of the toner using known means such as a transmission electron microscope (TEM) or a scanning probe microscope (SPM).

[0098] As the resin constituting the core part, an amorphous vinyl resin is preferably the main component, and as the resin constituting the shell part, an amorphous polyester resin is preferably the main component. Here, the "main component" means containing 55% by mass or more, preferably 70% by mass or more, and more preferably 80% by mass or more based on the total amount of the constituent resins.

[0099] Also, the degree of compatibility between the core part forming resin and the shell part forming resin can be controlled by methods such as changing the composition of the core part resin and the shell part resin, such as using a styrene-acrylic resin for the core part resin and a polyester resin for the shell part resin, or by introducing styrene-acrylic resin units into the polyester resin. Furthermore, the toner base particles according to the present invention may contain other constituent components such as a colorant, a release agent (wax), a charge control agent, etc., as required.

[0100] [2.2.1] Binder resin <Amorphous resin> (Vinyl resin) The vinyl resin according to the present invention is not particularly limited as long as it is a polymerized vinyl compound. Examples thereof include (meth)acrylic acid ester resins, styrene-(meth)acrylic acid ester resins, and ethylene-vinyl acetate resins. These may be used alone or in combination of two or more.

[0101] Among the above vinyl resins, considering the plasticity during heat fixation, styrene·(meth)acrylate resin is preferred. Therefore, hereinafter, styrene·(meth)acrylate resin as an amorphous resin (hereinafter, also referred to as "styrene·(meth)acrylic resin") will be described.

[0102] An amorphous resin refers to a resin in which no distinct endothermic peak is observed in differential scanning calorimetry (DSC). That is, it usually does not have a melting point (a distinct endothermic peak in the DSC curve measured using a differential scanning calorimetry (DSC) apparatus), but has a relatively high glass transition point (Tg). More specifically, the Tg of the amorphous resin measured by a differential scanning calorimeter is preferably in the range of 35 to 70 °C, more preferably in the range of 50 to 65 °C. When the Tg of the amorphous resin is 35 °C or higher, sufficient thermal strength can be imparted to the toner, and sufficient heat-resistant storage stability can be obtained. Also, when the Tg of the amorphous resin is 70 °C or lower, sufficient low-temperature fixability can be surely obtained.

[0103] The Tg of the amorphous resin is measured by the method (DSC method) specified in ASTM (American Society for Testing and Materials Standard) D3418 - 82. That is, 4.5 mg of the measurement sample (amorphous resin) is precisely weighed to two decimal places, sealed in an aluminum pan, and set in the sample holder of a differential scanning calorimeter "DSC8500" (manufactured by PerkinElmer). For the reference, an empty aluminum pan is used, and temperature control of heating - cooling - heating is performed at a measurement temperature of -10 to 120 °C, a heating rate of 10 °C / min, and a cooling rate of 10 °C / min, and analysis is performed based on the data in the second heating. The value of the intersection of the extension line of the baseline before the rise of the first endothermic peak and the tangent line showing the maximum slope between the rising part of the first endothermic peak and the peak top is taken as the glass transition point.

[0104] The styrene-(meth)acrylic resin is formed by addition polymerization of at least a styrene monomer and a (meth)acrylic acid ester monomer. The styrene monomer referred to here includes, in addition to styrene represented by the structural formula CH2=CH-C6H5, those having a structure with known side chains or functional groups in the styrene structure.

[0105] In addition, the (meth)acrylic acid ester monomer referred to here includes, in addition to acrylic acid esters and methacrylic acid esters represented by CH2=CHCOOR (R is an alkyl group), esters having known side chains or functional groups in their structures such as acrylic acid ester derivatives and methacrylic acid ester derivatives. In this specification, the "(meth)acrylic acid ester monomer" is a general term for "acrylic acid ester monomer" and "methacrylic acid ester monomer".

[0106] An example of the styrene monomer and the (meth)acrylic acid ester monomer capable of forming the styrene-(meth)acrylic resin is shown below.

[0107] Specific examples of the styrene monomer include, for example, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene, p-n-dodecylstyrene, and the like. These styrene monomers can be used alone or in combination of two or more.

[0108] Specific examples of the (meth)acrylate monomer include, for example, acrylate monomers such as methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, phenyl acrylate; methacrylate esters such as 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, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate. These (meth)acrylate monomers can be used alone or in combination of two or more.

[0109] The content of the structural unit derived from the styrene monomer in the styrene-(meth)acrylic resin is preferably in the range of 40 to 90% by mass based on the total amount of the resin. Further, the content of the structural unit derived from the (meth)acrylate monomer in the resin is preferably in the range of 10 to 60% by mass based on the total amount of the resin. Furthermore, the styrene-(meth)acrylic resin may contain the following monomer compounds in addition to the above styrene monomer and (meth)acrylate monomer. Examples of such monomer compounds include compounds having a carboxy group such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, cinnamic acid, fumaric acid, maleic acid monoalkyl ester, itaconic acid monoalkyl ester; compounds having a hydroxy group such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate. These monomer compounds can be used alone or in combination of two or more.

[0110] The content rate of the structural unit derived from the above monomer compound in the styrene·(meth)acrylic resin is preferably in the range of 0.5 to 20% by mass with respect to the total amount of the resin. The weight average molecular weight (Mw) of the styrene·(meth)acrylic resin is preferably in the range of 10,000 to 100,000.

[0111] The molecular weight of the styrene·(meth)acrylic resin is the weight average molecular weight (Mw) calculated from the molecular weight distribution measured by gel permeation chromatography (GPC). The molecular weight measurement by GPC is carried out as follows.

[0112] That is, using the apparatus "HLC-8320" (manufactured by Tosoh Corporation), columns "TSKgel guardcolumn SuperHZ-L" and "TSKgel SuperHZM-M" (manufactured by Tosoh Corporation), while maintaining the column temperature at 40°C, tetrahydrofuran (THF) is flowed as a carrier solvent at a flow rate of 0.2 ml / min. The measurement sample (crystalline polyester resin) is dissolved in tetrahydrofuran to a concentration of 1 mg / ml under dissolution conditions of being treated for 5 minutes using an ultrasonic disperser at room temperature, and then treated with a membrane filter having a pore size of 0.2 μm to obtain a sample solution. 10 μL of this sample solution is injected into the apparatus together with the above carrier solvent, detected using a refractive index detector (RI detector), and calculated using a calibration curve obtained by measuring the molecular weight distribution of the measurement sample using monodisperse polystyrene standard particles.

[0113] As the standard polystyrene sample for calibration curve measurement, those manufactured by Pressure Chemical with molecular weights of 6×10 2 , 2.1×10 3 , 4×10 3 , 1.75×10 4 , 5.1×10 4 , 1.1×10 5 , 3.9×10 5 , 8.6×10 5 , 2×10 6 , 4.48×10 6Using this, measure at least about 10 standard polystyrene samples to create a calibration curve.

[0114] The method for producing the styrene-(meth)acrylic resin is not particularly limited, and any polymerization initiator such as peroxides, persulfides, persulfates, and azo compounds commonly used for the polymerization of the above monomers can be used, and polymerization can be carried out by known polymerization methods such as bulk polymerization, solution polymerization, emulsion polymerization method, miniemulsion method, and dispersion polymerization method. Also, for the purpose of adjusting the molecular weight, a generally used chain transfer agent can be used. The chain transfer agent is not particularly limited, and examples thereof include alkyl mercaptans such as n-octyl mercaptan and mercapto fatty acid esters.

[0115] (Amorphous polyester resin) The amorphous polyester resin is obtained by a polycondensation reaction of a dicarboxylic acid or higher (polyvalent carboxylic acid) and a diol or higher (polyvalent alcohol). There are no particular restrictions on the specific amorphous polyester resin, and conventionally known amorphous polyester resins in the technical field can be used.

[0116] The specific production method of the amorphous polyester resin is not particularly limited, and the resin can be produced by polycondensing (esterifying) a polyvalent carboxylic acid and a polyvalent alcohol using a known esterification catalyst.

[0117] The weight average molecular weight (Mw) of the amorphous polyester resin is not particularly limited, but for example, it is preferably in the range of 5,000 to 100,000, and more preferably in the range of 5,000 to 50,000. When the above weight average molecular weight (Mw) is 5,000 or more, the heat-resistant storage property of the toner can be improved, and when it is 100,000 or less, the low-temperature fixing property can be further improved.

[0118] Examples of the polyvalent carboxylic acid and polyvalent alcohol used in the preparation of the amorphous polyester resin are not particularly limited, but the following are mentioned.

[0119] 《Polycarboxylic Acid》 Aromatic carboxylic acids such as terephthalic acid, isophthalic acid, phthalic anhydride, trimellitic anhydride, pyromellitic acid, naphthalenedicarboxylic acid, etc., aliphatic carboxylic acids such as maleic anhydride, fumaric acid, succinic acid, alkenyl succinic anhydride, adipic acid, etc., and alicyclic carboxylic acids such as cyclohexanedicarboxylic acid, etc. may be mentioned. These polycarboxylic acids may be used alone or in combination of two or more.

[0120] Among these polycarboxylic acids, it is preferable to use aromatic carboxylic acids, and in order to ensure better fixing properties and to form a crosslinked structure or a branched structure, it is preferable to use a carboxylic acid having a valence of 3 or more (such as trimellitic acid or its acid anhydride, etc.) in combination with a dicarboxylic acid. Examples of carboxylic acids having a valence of 3 or more include 1,2,3-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,3,5-benzenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, etc., and anhydrides thereof and lower alkyl esters thereof. These may be used alone or in combination of two or more.

[0121] 《Polyhydric Alcohol》 Aliphatic diols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol, glycerin, etc., alicyclic diols such as cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A, etc., and aromatic diols such as ethylene oxide adduct of bisphenol A, propylene oxide adduct of bisphenol A, etc. may be mentioned. These polyhydric alcohols may be used alone or in combination of two or more.

[0122] Among these polyhydric alcohols, aromatic diols and alicyclic diols are preferred, and among them, aromatic diols are more preferred. Further, in order to ensure better fixing properties, a polyhydric alcohol having a trivalent or higher valence (glycerin, trimethylolpropane, pentaerythritol) may be used in combination with the diol in order to form a crosslinked structure or a branched structure.

[0123] In addition, a monocarboxylic acid and / or a monoalcohol may be added to the polyester resin obtained by polycondensation of a polycarboxylic acid and a polyhydric alcohol to esterify the hydroxy group and / or the carboxy group at the polymerization terminal to adjust the acid value of the polyester resin.

[0124] Examples of the monocarboxylic acid include acetic acid, acetic anhydride, benzoic acid, trichloroacetic acid, trifluoroacetic acid, propionic anhydride, etc., and examples of the monoalcohol include methanol, ethanol, propanol, octanol, 2-ethylhexanol, trifluoroethanol, trichloroethanol, hexafluoroisopropanol, phenol, etc.

[0125] As the amorphous polyester resin used in the present invention, a hybrid amorphous polyester resin in which a vinyl-based polymer segment composed of a styrene·acrylic polymer or the like and a polyester-based polymer segment composed of an amorphous polyester resin are bonded via both reactive monomers can also be used.

[0126] The content ratio of the vinyl-based polymer segment is preferably in the range of 5 to 30% by mass, more preferably in the range of 10 to 20% by mass, based on the total mass of the hybrid amorphous polyester resin.

[0127] When the hybrid amorphous polyester resin contains a vinyl-based polymer segment in the range of 5 to 30% by mass, it becomes possible to control the balance between charge retention and charge leakage.

[0128] <Crystalline resin> (Crystalline polyester resin)

[0129] From the viewpoint of low-temperature fixability, it is preferable that the toner base particles according to the present invention contain a crystalline resin as a binder resin.

[0130] The crystalline resin refers to a resin having a clear endothermic peak instead of a stepped endothermic change in differential scanning calorimetry (DSC). Specifically, the clear endothermic peak means a peak whose half-width at half maximum of the endothermic peak is within 15 °C when measured at a heating rate of 10 °C / min in differential scanning calorimetry (DSC).

[0131] The crystalline resin is not particularly limited as long as it has the above characteristics, and conventionally known crystalline resins in the technical field can be used. Specific examples thereof include crystalline polyester resins, crystalline polyurethane resins, crystalline polyurea resins, crystalline polyamide resins, crystalline polyether resins, and the like. The crystalline resin can be used alone or in combination of two or more.

[0132] Among them, the crystalline resin is preferably a crystalline polyester resin. Here, the "crystalline polyester resin" is a known polyester resin obtained by a polycondensation reaction of a dicarboxylic acid or higher (polyvalent carboxylic acid) and its derivative with a diol or higher (polyvalent alcohol) and its derivative, and satisfies the above endothermic characteristics.

[0133] The melting point of the crystalline polyester resin is preferably in the range of 55 to 90°C, more preferably in the range of 60 to 85°C. When the melting point of the crystalline polyester resin is within the above range, sufficient low-temperature fixability and excellent image storage properties can be obtained. The melting point of the crystalline polyester resin can be controlled by the resin composition. Here, the melting point of the crystalline polyester resin is the peak top temperature of the melting peak in the second heating process in the DSC curve obtained by differential scanning calorimetry of the above-mentioned crystalline polyester resin alone. When there are multiple melting peaks in the DSC curve, the peak top temperature of the melting peak with the largest endothermic amount is taken as the melting point.

[0134] The polyvalent carboxylic acid component for forming the crystalline polyester resin is a compound containing two or more carboxy groups in one molecule. Specifically, for example, saturated aliphatic dicarboxylic acids such as succinic acid, sebacic acid, and dodecanedioic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid; aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, and terephthalic acid; polyvalent carboxylic acids with a valence of 3 or more such as trimellitic acid and pyromellitic acid; and anhydrides of these carboxylic acid compounds, or alkyl esters having 1 to 3 carbon atoms, etc. can be mentioned. As the polyvalent carboxylic acid component for forming the crystalline polyester resin, it is preferable to use a saturated aliphatic dicarboxylic acid. These may be used alone or in combination of two or more.

[0135] The polyhydric alcohol component for forming the crystalline polyester resin is a compound containing two or more hydroxy groups in one molecule. Specifically, for example, aliphatic diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, neopentyl glycol, 1,4-butenediol; polyhydric alcohols with three or more valences such as glycerin, pentaerythritol, trimethylolpropane, sorbitol, etc. can be mentioned. As the polyhydric alcohol component for forming the crystalline polyester resin, it is preferable to use an aliphatic diol. These may be used alone or in combination of two or more.

[0136] There is no particular limitation on the method for producing the crystalline polyester resin, and it can be produced using a general polyester polymerization method in which the above-mentioned polycarboxylic acid and polyhydric alcohol are reacted under a catalyst. For example, it is preferable to separately use direct polycondensation or transesterification depending on the type of monomer.

[0137] In addition, linear aliphatic hydroxycarboxylic acids can be used in combination with the polycarboxylic acid and / or polyhydric alcohol. Examples of the linear aliphatic hydroxycarboxylic acid for forming the crystalline polyester resin include 5-hydroxypentanoic acid, 6-hydroxyhexanoic acid, 7-hydroxypentanoic acid, 8-hydroxyoctanoic acid, 9-hydroxynonanoic acid, 10-hydroxydecanoic acid, 12-hydroxydodecanoic acid, 14-hydroxytetradecanoic acid, 16-hydroxyhexadecanoic acid, 18-hydroxyoctadecanoic acid; lactone compounds formed by cyclization of these hydroxycarboxylic acids, or alkyl esters with alcohols having 1 to 3 carbon atoms, etc. These may be used alone or in combination of two or more.

[0138] In addition, when forming a crystalline polyester resin, it is preferable to use a polyvalent carboxylic acid and a polyhydric alcohol component to control the reaction, and a resin having a target molecular weight can be obtained.

[0139] Examples of the catalyst that can be used in the production of the crystalline polyester resin include titanium catalysts such as titanium tetraethoxide, titanium tetrapropoxide, titanium tetraisopropoxide, and titanium tetrabutoxide, and tin catalysts such as dibutyltin dichloride, dibutyltin oxide, and diphenyltin oxide.

[0140] The usage ratio of the above polyvalent carboxylic acid component and polyhydric alcohol component is such that the equivalent ratio [OH] / [COOH] of the hydroxy group [OH] of the polyhydric alcohol component and the carboxy group [COOH] of the polyvalent carboxylic acid component is preferably in the range of 1.5 / 1 to 1 / 1.5, more preferably in the range of 1.2 / 1 to 1 / 1.2.

[0141] The acid value of the crystalline polyester resin is preferably in the range of 5 to 30 mgKOH / g, more preferably in the range of 10 to 25 mgKOH / g, and even more preferably in the range of 15 to 25 mgKOH / g. This acid value represents the mass of potassium hydroxide (KOH) required for neutralizing the acid contained in 1 g of the sample in mg units. The acid value of the resin is measured according to the following procedure in accordance with JIS K0070-1992.

[0142] (Preparation of reagents) Dissolve 1.0 g of phenolphthalein in 90 mL of ethyl alcohol (95% by volume), add ion-exchanged water to make 100 mL, and prepare a phenolphthalein solution. Dissolve 7 g of JIS special grade potassium hydroxide in 5 mL of ion-exchanged water, add ethyl alcohol (95% by volume) to make 1 liter. Put it in an alkali-resistant container so as not to come into contact with carbon dioxide gas, leave it for 3 days, and then filter it to prepare a potassium hydroxide solution. The calibration follows the description in JIS K0070-1992.

[0143] (This test) Precisely weigh 2.0 g of the crushed sample into a 200 mL Erlenmeyer flask, add 100 mL of a mixed solution of toluene / ethanol (toluene:ethanol is 2:1 by volume ratio), and dissolve it over 5 hours. Then, add a few drops of the phenolphthalein solution prepared as an indicator and titrate with the prepared potassium hydroxide solution. Note that the end point of the titration is when the faint red color of the indicator persists for about 30 seconds.

[0144] (Blank test) Perform the same operations as the above main test, except that no sample is used (that is, use only the mixed solution of toluene / ethanol (toluene:ethanol is 2:1 by volume ratio)).

[0145] Substitute the titration results of the main test and the blank test into the following formula (a) to calculate the acid value.

[0146] Formula (a) A = 〔(C - B) × f × 5.6〕 / S A: Acid value (mgKOH / g) B: Amount of potassium hydroxide solution added during the blank test (mL) C: Amount of potassium hydroxide solution added during the main test (mL) f: Factor of 0.1 mol / L potassium hydroxide ethanol solution S: Mass of the sample (g)

[0147] The weight average molecular weight (Mw) of the crystalline polyester resin is preferably from 3,000 to 100,000, more preferably from 4,000 to 50,000, and particularly preferably from 5,000 to 20,000 from the viewpoint of ensuring both sufficient low-temperature fixability and excellent long-term heat-resistant storage stability. The usage ratio of the above diol component and dicarboxylic acid component is preferably such that the ratio [OH] / [COOH] of the equivalent [OH] of the hydroxyl group of the diol component to the equivalent [COOH] of the carboxyl group of the dicarboxylic acid component is from 1.5 / 1 to 1 / 1.5, and more preferably from 1.2 / 1 to 1 / 1.2.

[0148] The content ratio of the crystalline polyester resin in the binder resin is preferably in the range of 5 to 20% by mass, more preferably in the range of 5 to 10% by mass. When the content ratio of the crystalline polyester resin in the binder resin is 5% by mass or more, sufficient low-temperature fixability can be surely obtained. Further, when the content ratio of the crystalline polyester resin in the binder resin is 20% by mass or less, the crystalline polyester resin can be surely introduced into the toner in the production of the toner.

[0149] Further, as the crystalline polyester resin, a styrene-acrylic modified crystalline polyester resin formed by bonding a styrene-acrylic polymer segment and a crystalline polyester polymer segment may be used.

[0150] The "styrene-acrylic modified crystalline polyester resin" is a resin composed of polyester molecules having a block copolymer structure in which a styrene-acrylic copolymer molecular chain (styrene-acrylic polymer segment) is chemically bonded to a crystalline polyester molecular chain (crystalline polyester polymer segment).

[0151] The method for forming the crystalline polyester polymer segment is not particularly limited. Since the specific types of the polyvalent carboxylic acid and polyhydric alcohol used for forming the polymer segment and the polycondensation conditions of these monomers are the same as those described above, the description thereof is omitted here.

[0152] On the other hand, the styrene-acrylic polymer segment constituting the styrene-acrylic modified crystalline polyester resin is formed by addition polymerization of at least a styrene monomer and a (meth)acrylic acid ester monomer. The styrene monomer and the (meth)acrylic acid ester monomer used are not particularly limited, and for example, one or more selected from the following may be used.

[0153] (1) Styrene monomer Styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene, p-n-dodecylstyrene, and derivatives thereof;

[0154] (2) (Meth)acrylic acid ester monomers (Meth)acrylic acid methyl, (meth)acrylic acid ethyl, (meth)acrylic acid n-butyl (n-butyl (meth)acrylate), (meth)acrylic acid isopropyl, (meth)acrylic acid isobutyl, (meth)acrylic acid t-butyl, (meth)acrylic acid n-octyl, (meth)acrylic acid 2-ethylhexyl, (meth)acrylic acid n-stearyl, (meth)acrylic acid dodecyl, (meth)acrylic acid phenyl, (meth)acrylic acid diethylaminoethyl, (meth)acrylic acid dimethylaminoethyl, and derivatives thereof; In this specification, "(meth)acrylic acid" includes both acrylic acid and methacrylic acid.

[0155] In addition to the above monomers, the styrene-acrylic polymerization segment may be formed by further using the following monomers.

[0156] (3) Vinyl esters Vinyl propionate, vinyl acetate, vinyl benzoate, etc.;

[0157] (4) Vinyl ethers Vinyl methyl ether, vinyl ethyl ether, etc.;

[0158] (5) Vinyl ketones Vinyl methyl ketone, vinyl ethyl ketone, vinyl hexyl ketone, etc.;

[0159] (6) N-vinyl compounds N-vinylcarbazole, N-vinylindole, N-vinylpyrrolidone, etc.;

[0160] (7) Other monomers Vinyl compounds such as vinyl naphthalene and vinyl pyridine, acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide, etc.

[0161] The method for forming the styrene-acrylic polymerization segment is not particularly limited, and any polymerization initiator such as peroxides, persulfides, persulfates, azo compounds, etc., which are commonly used in the polymerization of the above monomers, can be used, and polymerization can be carried out by known polymerization methods such as bulk polymerization, solution polymerization, emulsion polymerization method, miniemulsion method, dispersion polymerization method, etc.

[0162] The content ratio of the crystalline polyester polymerization segment in the styrene-acrylic modified crystalline polyester resin is not particularly limited, but it is preferably in the range of 60 to 99% by mass, more preferably in the range of 70 to 98% by mass, based on 100% by mass of the styrene-acrylic modified polyester resin.

[0163] The content ratio of the styrene-acrylic polymerization segment in the styrene-acrylic modified crystalline polyester resin (hereinafter, also referred to as the "styrene-acrylic modification amount") is not particularly limited, but it is preferably in the range of 1 to 40% by mass, more preferably in the range of 2 to 30% by mass, based on 100% by mass of the styrene-acrylic modified crystalline polyester resin.

[0164] Specifically, the styrene-acrylic modification amount refers to the ratio of the total mass of the styrene monomer and the (meth)acrylate monomer to the total mass of the resin materials used to synthesize the styrene-acrylic modified crystalline polyester resin, that is, the monomers for synthesizing the unmodified crystalline polyester resin that will become the crystalline polyester polymerization segment, the styrene monomer and the (meth)acrylate monomer that will become the styrene-acrylic polymerization segment, and the total mass of both reactive monomers for bonding them.

[0165] Here, the "difunctional monomer" is a monomer that binds a styrene-acrylic polymerization segment and a crystalline polyester polymerization segment, and has, in the molecule, both a group selected from a hydroxy group, a carboxy group, an epoxy group, a primary amino group, and a secondary amino group that form the crystalline polyester polymerization segment and an ethylenically unsaturated group that forms the styrene-acrylic polymerization segment.

[0166] Specific examples of the difunctional monomer include, for example, acrylic acid, methacrylic acid, fumaric acid, maleic acid, etc., and may further be esters of these hydroxyalkyls (having 1 to 3 carbon atoms), but acrylic acid, methacrylic acid, or fumaric acid is preferable from the viewpoint of reactivity. Through this difunctional monomer, the styrene-acrylic polymerization segment and the crystalline polyester polymerization segment are bonded.

[0167] From the viewpoint of improving low-temperature fixability, the amount of the difunctional monomer used is preferably in the range of 1 to 20% by mass with respect to 100% by mass of the total amount of the monomers constituting the styrene-acrylic polymerization segment.

[0168] The method for producing the styrene-acrylic modified crystalline polyester resin is not particularly limited as long as it is a method capable of forming a polymer having a structure in which the crystalline polyester polymerization segment and the styrene-acrylic polymerization segment are chemically bonded. Specific methods for producing the styrene-acrylic modified crystalline polyester resin include, for example, the methods shown below.

[0169] (A) A method of forming a styrene-acrylic polymerization segment by previously polymerizing a crystalline polyester polymerization segment, reacting a difunctional monomer with the crystalline polyester polymerization segment, and further reacting a styrene monomer and a (meth)acrylic acid ester monomer for forming the styrene-acrylic polymerization segment;

[0170] (B) A method of forming a crystalline polyester polymerization segment by polymerizing a styrene-acrylic polymerization segment in advance, reacting both reactive monomers with the styrene-acrylic polymerization segment, and further reacting a polyvalent carboxylic acid and a polyhydric alcohol for forming a crystalline polyester polymerization segment;

[0171] (C) A forming method of bonding a crystalline polyester polymerization segment and a styrene-acrylic polymerization segment by polymerizing them in advance and reacting both reactive monomers with them.

[0172] Among the above formation methods (A) to (C), the method (A) is preferable from the viewpoint of being able to simplify the production process and the like.

[0173] [2.2.2] Other components (Colorant) As the colorant, carbon black, magnetic substances, dyes, pigments, etc. can be arbitrarily used. As carbon black, channel black, furnace black, acetylene black, thermal black, or lamp black, etc. are used. As magnetic substances, ferromagnetic metals such as iron, nickel, or cobalt, alloys containing these metals, compounds of ferromagnetic metals such as ferrite or magnetite, etc. can be used. Examples of dyes include C.I. Solvent Red 1, 49, 52, 58, 63, 111, 122, C.I. Solvent Yellow 19, 44, 77, 79, 81, 82, 93, 98, 103, 104, 112, 162, C.I. Solvent Blue 25, 36, 60, 70, 93, 95, etc., and mixtures thereof can also be used. Examples of pigments include C.I. Pigment Red 5, 48:1, 48:3, 53:1, 57:1, 81:4, 122, 139, 144, 149, 166, 177, 178, 222, C.I. Pigment Orange 31, 43, C.I. Pigment Yellow 14, 17, 74, 93, 94, 138, 155, 180, 185, C.I. Pigment Green 7, C.I. Pigment Blue 15:3, 15:4, or 60, etc., and mixtures thereof can also be used.

[0174] Examples of colorants for white include inorganic pigments (e.g., titanium white, zinc white, titanium strontium white, heavy calcium carbonate, light calcium carbonate, titanium dioxide, aluminum hydroxide, satin white, talc, calcium sulfate, barium sulfate, zinc oxide, magnesium oxide, magnesium carbonate, amorphous silica, colloidal silica, white carbon, kaolin, calcined kaolin, delaminated kaolin, aluminosilicate, sericite, bentonite, smectite, etc.) or organic pigments (e.g., polystyrene resin particles, urea formalin resin particles, etc.).

[0175] The content of the above colorant in the toner base particles can be determined appropriately and independently. For example, from the viewpoint of ensuring color reproducibility of the image, it is preferably in the range of 1 to 30% by mass, and more preferably in the range of 2 to 20% by mass.

[0176] Also, the size of the colorant particles is preferably in the range of, for example, 10 to 1000 nm, more preferably in the range of 50 to 500 nm, and even more preferably in the range of 80 to 300 nm in terms of volume average particle diameter.

[0177] The volume average particle diameter may be a catalog value. For example, the volume average particle diameter (volume-based median diameter) of a colorant can be measured by "UPA-150" (manufactured by Microtrac Bell Co., Ltd.).

[0178] (Release agent) The toner according to the present invention may contain a release agent (also referred to as "wax"). As the release agent, various known waxes can be used.

[0179] Specifically, for example, polyolefin waxes such as polyethylene wax and polypropylene wax; branched-chain hydrocarbon waxes such as microcrystalline wax; long-chain hydrocarbon waxes such as paraffin wax and sasol wax; dialkyl ketone waxes such as distearyl ketone; ester waxes such as carnauba wax, montan wax, behenyl behenate, trimethylolpropane tribehenate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecanediol distearate, tristearyl trimellitate, distearyl maleate; amide waxes such as ethylenediamine behenylamide and tristearyl trimellitate amide, etc. can be mentioned.

[0180] As the release agent, it is preferable to use one that has no interaction such as being compatible with the resin constituting the binder resin.

[0181] Among these, from the viewpoint of release property during low-temperature fixing, it is preferable to use those with a low melting point, specifically, those with a melting point in the range of 60 to 100°C. Further, as the release agent, it is preferable to use one having a melting point of about (Mp1 - 10)°C to (Mp1 + 20)°C with respect to the melting point Mp1 of the crystalline polyester resin constituting the binder resin.

[0182] The content ratio of the release agent is preferably in the range of 1 to 20% by mass in the toner, more preferably in the range of 5 to 20% by mass. When the content ratio of the release agent in the toner is within the above range, the separability and fixability can be surely achieved simultaneously.

[0183] As a method for introducing the release agent into the toner, in the aggregation and fusion step of the toner manufacturing method described later, a method of aggregating and fusing particles composed only of the release agent together with amorphous resin particles, crystalline polyester resin particles, etc. in an aqueous medium can be mentioned. The release agent particles can be obtained as a dispersion liquid in which the release agent is dispersed in an aqueous medium. The dispersion liquid of the release agent particles can be prepared by heating an aqueous medium containing a surfactant to a temperature higher than the melting point of the release agent, adding the melted release agent solution, and applying mechanical energy such as mechanical stirring or ultrasonic energy to finely disperse it, and then cooling it.

[0184] Also, when the amorphous resin is, for example, a styrene-acrylic resin, the release agent can be introduced into the toner by previously mixing the release agent with the amorphous resin particles (styrene-acrylic resin particles) to be subjected to the aggregation and fusion step.

[0185] Specifically, the release agent is dissolved in a solution of a polymerizable monomer for forming a styrene-acrylic resin. This solution is added to an aqueous medium containing a surfactant, and after finely dispersing it by applying mechanical energy such as mechanical stirring or ultrasonic energy in the same manner as above, a polymerization initiator is added and polymerization is carried out at a desired polymerization temperature. By the so-called miniemulsion polymerization method, a dispersion liquid of amorphous resin particles containing the release agent can be prepared.

[0186] (Charge control agent) As the charge control agent, various known compounds can be used. Examples thereof include nigrosine dyes, metal salts of naphthenic acid or higher fatty acids, alkoxylated amines, quaternary ammonium salt compounds, azo metal complexes, and metal salts of salicylic acid.

[0187] The content of the charge control agent in the toner of the present invention is usually in the range of 0.1 to 10 parts by mass, preferably in the range of 0.5 to 5% by mass, based on 100 parts by mass of the binder resin.

[0188] Also, the size of the particles of the charge control agent is, for example, in the range of 10 to 1000 nm in terms of the number average primary particle diameter, preferably in the range of 50 to 500 nm, and more preferably in the range of 80 to 300 nm.

[0189] In the toner particles according to the present invention, it is preferable to have a core-shell structure including core particles containing a binder resin and a colorant, and a shell layer coated on the surface of the core particles. Note that the shell layer is not limited to completely covering the core particles, and a part of the surface of the core particles may be exposed. By having a core-shell structure for the toner, charge stability and heat-resistant storage properties can be obtained. The resin constituting the shell layer is not particularly limited, but it is preferable to use an amorphous polyester resin, an amorphous vinyl resin, or the like.

[0190] The core-shell structure can be confirmed, for example, by observing the structure of the cross-section of the toner using known means such as a transmission electron microscope (TEM) or a scanning probe microscope (SPM).

[0191] [2.2.3] Method for manufacturing toner particles The method for manufacturing the toner particles of the present invention is not particularly limited, and known methods such as a kneading and grinding method, a suspension polymerization method, an emulsion aggregation method, a dissolution suspension method, a polyester stretching method, and a dispersion polymerization method can be mentioned. Among these, from the viewpoints of particle size uniformity and shape controllability, it is preferable to adopt the emulsion aggregation method.

[0192] The toner particles according to the present invention can be specifically manufactured by a manufacturing method including the following steps. However, only an example is disclosed here, and the present invention is not limited to the examples of the following manufacturing methods.

[0193] The toner particles according to the present invention are preferably manufactured by a wet method prepared in an aqueous medium, and can be manufactured, for example, by an emulsification aggregation method or the like.

[0194] The emulsification aggregation method involves mixing an aqueous dispersion of resin particles constituting a binder resin with an aqueous dispersion of particles of other toner constituent components as necessary, and slowly aggregating while balancing the repulsive force on the particle surface by pH adjustment and the aggregating force by the addition of a flocculant composed of an electrolyte, and performing association while controlling the average particle diameter and particle size distribution. At the same time, fusion between fine particles is carried out by heating and stirring to control the shape, thereby manufacturing toner.

[0195] As an example of a preferred method for manufacturing toner particles according to the present invention, when obtaining toner particles having a core-shell structure using the emulsification aggregation method is shown below. (1) Step of preparing a colorant particle dispersion in which colorant particles are dispersed in an aqueous medium (2) Step of preparing a resin particle dispersion (core / shell resin particle dispersion) in which binder resin particles containing an internal additive as necessary are dispersed in an aqueous medium (3) Step of mixing the colorant particle dispersion and the core resin particle dispersion to obtain a resin particle dispersion for aggregation, and aggregating and fusing the colorant particles and the binder resin particles in the presence of a flocculant to form aggregated particles as core particles (aggregation / fusion step) (4) Step of adding a shell resin particle dispersion containing shell binder resin particles to the dispersion containing core particles, and aggregating and fusing the shell particles on the surface of the core particles to form toner base particles having a core-shell structure (aggregation / fusion step) (5) Step of filtering out the toner base particles from the dispersion of the toner base particles (toner base particle dispersion) and removing a surfactant or the like (filtering, washing step) (6) Step of drying the toner base particles (drying step) (7) Step of adding an external additive to the toner base particles (external additive treatment step) Toner particles having a core-shell structure can be obtained by first aggregating and fusing binder resin particles for core particles and colorant particles to produce core particles, and then adding binder resin particles for the shell into the dispersion of the core particles to aggregate and fuse the binder resin particles for the shell on the surface of the core particles to form a shell layer covering the surface of the core particles. However, for example, in the step (4) above, toner particles formed from single-layer particles can also be produced in the same manner without adding the resin particle dispersion for the shell.

[0196] In the present invention, the "aqueous medium" refers to a medium composed of 50 to 100% by mass of water and 0 to 50% by mass of a water-soluble organic solvent. Examples of the water-soluble organic solvent include methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone, and tetrahydrofuran, and it is preferable to use an alcohol-based organic solvent that does not dissolve the resulting resin.

[0197] (1) Colorant particle dispersion preparation step The colorant particle dispersion can be prepared by dispersing the colorant in an aqueous medium. The dispersion treatment of the colorant is preferably carried out in a state where the surfactant concentration is at or above the critical micelle concentration (CMC) in the aqueous medium because the colorant is uniformly dispersed. As the disperser used for the dispersion treatment of the colorant, various known dispersers can be used.

[0198] (Surfactant) As surfactants, anionic surfactants such as alkyl sulfate salts, polyoxyethylene(n) alkyl ether sulfates, alkylbenzene sulfonates, α-olefin sulfonates, and phosphate esters; amine salt types such as alkylamine salts, amino alcohol fatty acid derivatives, polyamine fatty acid derivatives, and imidazolines; and quaternary ammonium salt types of cationic surfactants such as alkyltrimethylammonium salts, dialkyldimethylammonium salts, alkyldimethylbenzylammonium salts, pyridinium salts, alkylisoquinolinium salts, and benzethonium chloride; nonionic surfactants such as fatty acid amide derivatives and polyhydric alcohol derivatives; amphoteric surfactants such as alanine, dodecyldi(aminoethyl)glycine, di(octylaminoethyl)glycine, and N-alkyl-N,N-dimethylammonium betaine can be mentioned. Also, anionic surfactants and cationic surfactants having a fluoroalkyl group can be used.

[0199] In the coloring agent particle dispersion preparation step, the dispersion diameter of the coloring agent particles in the prepared coloring agent particle dispersion is preferably in the range of 10 to 300 nm in terms of the volume-based median diameter. The volume-based median diameter of the coloring agent particles in this coloring agent particle dispersion is measured with an electrophoretic light scattering photometer "ELS-800 (manufactured by Otsuka Electronics Co., Ltd.)".

[0200] The coloring agent may be introduced into the toner by dissolving or dispersing it in a monomer solution for forming an amorphous resin in advance using the miniemulsion method in the amorphous resin particle dispersion preparation step described later.

[0201] (2) A step of preparing a resin particle dispersion (core / shell resin particle dispersion) in which binder resin particles containing an internal additive as needed are dispersed in an aqueous medium As a method for dispersing a binder resin in an aqueous medium, there are an aqueous direct dispersion method in which the binder resin is dispersed in an aqueous medium added with a surfactant by an ultrasonic dispersion method, a bead mill dispersion method, etc., a dissolution emulsification desolvation method in which the binder resin is dissolved in a solvent, dispersed in an aqueous medium to form emulsion particles (oil droplets), and then the solvent is removed, a phase inversion emulsification method, and the like.

[0202] In this step of preparing the binder resin particle dispersion, the average particle diameter of the binder resin particles obtained is preferably in the range of, for example, 50 to 500 nm in terms of the volume-based median diameter. The volume-based median diameter is measured using "UPA-EX150" (manufactured by Microtrac Bell Co., Ltd.).

[0203] When the binder resin is an amorphous vinyl resin, in an aqueous medium containing a surfactant below the critical micelle concentration (CMC), to the polymerizable monomer for forming the amorphous vinyl resin, a liquid in which toner components such as a release agent and a charge control agent are dissolved or dispersed as necessary is added, mechanical energy is applied to form droplets, and then a water-soluble radical polymerization initiator is added to allow the polymerization reaction to proceed in the droplets, whereby an amorphous resin particle dispersion can also be prepared. Note that an oil-soluble polymerization initiator may be contained in the droplets. In such a step of preparing the amorphous resin particle dispersion, a treatment for applying mechanical energy to perform emulsification (formation of droplets) is essential. Examples of the means for applying such mechanical energy include a homomixer, ultrasonic waves, and means for applying strong stirring such as Manton Gaulin or ultrasonic vibration energy.

[0204] The binder resin particles formed in this step of preparing the binder resin particle dispersion can also have a structure of two or more layers made of resins having different compositions. In this case, a method can be adopted in which a polymerization initiator and a polymerizable monomer are added to a dispersion of resin particles prepared by an emulsion polymerization treatment (first-stage polymerization) according to a conventional method, and this system is subjected to a polymerization treatment (second-stage polymerization, third-stage polymerization).

[0205] When using a surfactant in this process, as the surfactant, for example, the same ones as the above-mentioned surfactants can be used.

[0206] (Polymerization initiator) As the polymerization initiator to be used, various known polymerization initiators can be used. Specifically, for example, hydrogen peroxide, acetyl peroxide, cumyl peroxide, tert-butyl peroxide, propionyl peroxide, benzoyl peroxide, chlorobenzoyl peroxide, dichlorobenzoyl peroxide, bromomethylbenzoyl peroxide, lauroyl peroxide, ammonium persulfate, sodium persulfate, potassium persulfate, diisopropyl peroxydicarbonate, tetralin hydroperoxide, 1-phenyl-2-methylpropyl-1-hydroperoxide, tert-hydroperoxide of triphenylacetic acid, tert-butyl peroxyformate, tert-butyl peracetate, tert-butyl perbenzoate, tert-butyl perphenylacetate, tert-butyl permethoxyacetate, tert-butyl per-N-(3-tolyl)palmitate and other peroxides; 2,2'-azobis(2-amidinopropane) hydrochloride, 2,2'-azobis-(2-amidinopropane) nitrate, 1,1'-azobis(1-methylbutyronitrile-3-sulfonic acid sodium salt), 4,4'-azobis-4-cyanovaleric acid, poly(tetraethylene glycol-2,2'-azobisisobutyrate) and other azo compounds, etc. can be mentioned. Among these, water-soluble polymerization initiators, for example, ammonium persulfate, sodium persulfate, potassium persulfate, hydrogen peroxide, 2,2'-azobis(2-amidinopropane) hydrochloride, 2,2'-azobis-(2-amidinopropane) nitrate, 1,1'-azobis(1-methylbutyronitrile-3-sulfonic acid sodium salt), 4,4'-azobis-4-cyanovaleric acid can be preferably used.

[0207] Also, as the polymerization initiator, redox polymerization initiators such as persulfate and metabisulfite, hydrogen peroxide and ascorbic acid can also be used.

[0208] (Chain transfer agent) In the step of preparing the binder resin (especially amorphous vinyl resin) particle dispersion, a commonly used chain transfer agent can be used for the purpose of adjusting the molecular weight of the amorphous resin. The chain transfer agent is not particularly limited, and examples thereof include alkyl mercaptan and mercapto fatty acid ester.

[0209] The average particle diameter of the amorphous vinyl resin particles obtained in this step of preparing the binder resin particle dispersion is preferably in the range of, for example, 50 to 500 nm in terms of the volume-based median diameter. The volume-based median diameter is measured using "UPA-EX150" (manufactured by Microtrac Bell Co., Ltd.).

[0210] (3) A step of mixing the colorant particle dispersion and the core resin particle dispersion to obtain a resin particle dispersion for aggregation, and aggregating and fusing the colorant particles and the binder resin particles in the presence of a flocculant to form aggregated particles as core particles (aggregation and fusion step)

[0211] This step aggregates and fuses the colorant particles and the binder resin particles contained in the dispersion formed in the above step in an aqueous medium. In this step, the binder resin particle dispersion and the colorant particle dispersion are added to the aqueous medium, and these particles are aggregated and fused.

[0212] As a specific method for aggregating and fusing the colorant particle dispersion and the binder resin particle dispersion, a flocculant is added to the aqueous medium so that the concentration is equal to or higher than the critical flocculation concentration, and then the temperature is raised to a temperature equal to or higher than the glass transition point of the binder resin particles and equal to or higher than the melting peak temperature of the mold release agent. By doing so, salting out of the colorant particles and the binder resin particles proceeds while fusion proceeds in parallel. When growth reaches the desired particle size, a flocculation inhibitor is added to stop particle growth, and further heating is continued as necessary to control the particle shape.

[0213] In this method, it is preferable to heat the mixture to a temperature equal to or higher than the glass transition point of the binder resin as soon as possible after adding the flocculant, while minimizing the standing time. Although the reason is not clear, there is concern that depending on the standing time after salting out, the aggregation state of the particles may vary, resulting in an unstable particle size distribution, or the surface properties of the fused particles may change. The time until the temperature is raised is usually preferably within 30 minutes, and more preferably within 10 minutes.

[0214] Also, the heating rate is preferably 1°C / min or more. Although there is no particular upper limit for the heating rate, from the perspective of suppressing the generation of coarse particles due to rapid fusion progress, it is preferably 15°C / min or less. Furthermore, after the reaction system reaches a temperature equal to or higher than the glass transition point, it is essential to hold the temperature of the reaction system for a certain period of time to continue the fusion. This enables the growth and fusion of the toner to proceed effectively, ultimately improving the durability of the obtained toner.

[0215] (Flocculant) The flocculant to be used is not particularly limited, but those selected from metal salts are preferably used. Examples of metal salts include monovalent metal salts such as salts of alkali metals such as sodium, potassium, and lithium; divalent metal salts such as calcium, magnesium, manganese, and copper; and trivalent metal salts such as iron and aluminum. Specific metal salts include sodium chloride, potassium chloride, lithium chloride, calcium chloride, magnesium chloride, zinc chloride, copper sulfate, magnesium sulfate, manganese sulfate, etc. Among these, it is particularly preferable to use divalent metal salts because they can promote aggregation in small amounts and it is easy to control the aggregability. These can be used alone or in combination of two or more.

[0216] When a surfactant is used in this step, a surfactant similar to the above-described surfactant can be used, for example.

[0217] (4) A step of adding a shell resin particle dispersion containing binder resin particles for the shell to a dispersion containing core particles, and aggregating and fusing the particles for the shell on the surface of the core particles to form toner base particles having a core-shell structure (aggregation and fusion step). This step is the same as the step of aggregating and fusing the colorant particles and the binder resin particles in the presence of the aggregating agent in (3) to form aggregated particles as core particles (aggregation and fusion step), and aggregates and fuses the particles for the shell on the surface of the core particles to form toner base particles having a core-shell structure.

[0218] (5) A step of filtering out the toner base particles from a dispersion of the toner base particles (toner base particle dispersion) and removing a surfactant or the like (filtration and washing step). (6) A step of drying the toner base particles (drying step). The filtration and washing step and the drying step can be carried out by adopting various known methods.

[0219] (7) A step of adding an external additive to the toner base particles (external additive treatment step). This external additive treatment step is a step of adding and mixing the external additive according to the present invention to the dried toner base particles.

[0220] Examples of the method of adding the external additive include a dry method of adding a powdery external additive to the dried toner base particles and mixing them, and as the mixing device, a mechanical mixing device such as a Henschel mixer or a coffee mill can be used.

[0221] [2.2.4] Physical properties of toner particles <Average particle diameter of toner particles> In the toner particles according to the present invention, the average particle diameter is preferably in the range of 3 to 8 μm, more preferably in the range of 5 to 8 μm, for example, the median diameter based on volume.

[0222] This average particle diameter can be controlled, for example, when manufacturing using the emulsion aggregation method described later, by factors such as the concentration of the aggregating agent used, the addition amount of the organic solvent, the fusing time, and the composition of the polymer. When the median diameter based on volume is within the above range, the transfer efficiency is increased, the halftone image quality is improved, and the image quality of fine lines and dots is also improved.

[0223] The median diameter of the toner based on volume can be measured and calculated, for example, using a measuring device connected to a computer system equipped with data processing software "Software V3.51" and a "Multisizer 3" (manufactured by Beckman Coulter).

[0224] Specifically, 0.02 g of the measurement sample (toner) is added to 20 mL of a surfactant solution (for example, a surfactant solution obtained by diluting a neutral detergent containing a surfactant component 10 times with pure water for the purpose of dispersing the toner), allowed to mix well, and then 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) in a sample stand until the display concentration of the measuring device reaches 8%. Here, by setting this concentration range, reproducible measurement values can be obtained. Then, in the measuring device, the number of measured particles is set to 25,000, the aperture diameter is set to 100 μm, the frequency values are calculated by dividing the measurement range of 2 to 60 μm into 256 parts, and the particle diameter at 50% from the larger side of the volume integration fraction is defined as the median diameter based on volume.

[0225] <Average circularity of toner particles> In the toner particles according to the present invention, from the viewpoints of the stability of the charging characteristics and the low-temperature fixability, it is preferable that the average circularity is within the range of 0.930 to 1.000, and more preferably within the range of 0.950 to 0.995. When the average circularity is within the above range, each toner particle is less likely to be crushed, the contamination of the friction charging member is suppressed, the charging property of the toner is stabilized, and the image quality of the formed image is high.

[0226] In the present invention, the average circularity of toner particles is measured using "FPIA-3000" (manufactured by Sysmex Corporation).

[0227] Specifically, the sample (toner particles) is wetted with an aqueous solution containing a surfactant, ultrasonic dispersion treatment is performed for 1 minute to disperse it, and then, using "FPIA-3000" (manufactured by Sysmex Corporation), imaging is performed at an appropriate concentration of 3000 to 10000 HPF detection counts in the measurement condition HPF (high magnification imaging) mode. For each toner particle, the circularity is calculated according to the following formula (T), the circularities of each toner particle are added up, and the result is divided by the total number of toner particles to obtain the average circularity.

[0228] Formula (T): Circularity = (circumference of a circle having the same projected area as the particle image) / (circumference of the particle projection image)

[0229] <Softening point of toner particles> From the viewpoint of obtaining low-temperature fixability for the toner, the softening point of the toner particles is preferably in the range of 80 to 120 °C, more preferably in the range of 90 to 110 °C.

[0230] The softening point of the toner particles is measured by the flow tester shown below.

[0231] Specifically, first, in an environment of 20 °C and 50% RH, 1.1 g of the sample (toner) is placed in a petri dish and leveled, and after leaving it for 12 hours or more, it is pressed by a molding machine "SSP-10A" (manufactured by Shimadzu Corporation) with a force of 3820 kg / cm 2 for 30 seconds to prepare a cylindrical molded sample with a diameter of 1 cm. Then, this molded sample is placed in an environment of 24 °C and 50% RH, and using a flow tester "CFT-500D" (manufactured by Shimadzu Corporation), with a load of 196 N (20 kgf), a starting temperature of 60 °C, a preheating time of 300 seconds, and a heating rate of 6 °C / min, from the hole of the cylindrical die (1 mm diameter × 1 mm), using a piston with a diameter of 1 cm, it is extruded from the end of the preheating, and the offset method temperature T offset measured with an offset value of 5 mm set by the melting temperature measurement method of the heating method is taken as the softening point.

[0232] [3] Electrophotographic Image Forming Method and Electrophotographic Image Forming Apparatus The electrophotographic image forming method of the present invention is an electrophotographic image forming method having at least a charging step of an image carrier, an electrostatic charge image forming step, an electrostatic charge image developing step, a toner image transfer step, a toner image fixing step, and a cleaning step, characterized in that at least the two-component developer for electrostatic charge image development of the present invention is used.

[0233] Specifically, it includes a charging step of charging the surface of the image carrier, an electrostatic charge image forming step of forming an electrostatic charge image on the charged surface of the image carrier, a developing step of developing the electrostatic charge image formed on the surface of the image carrier as a toner image using at least four-color two-component developer for electrostatic charge image development of the present invention, a transfer step of transferring the toner image formed on the surface of the image carrier to the surface of a recording medium, a fixing step of fixing the toner image transferred to the surface of the recording medium, and a cleaning step of the surface of the image carrier.

[0234] (Charging step) In this step, the electrophotographic photoreceptor is charged. The charging method is not particularly limited, and for example, a known method such as a charging roller method in which the electrophotographic photoreceptor is charged by a charging roller may be used.

[0235] (Step of forming an electrostatic charge image) In this step, an electrostatic charge image is formed on the electrophotographic photoreceptor (electrostatic charge image carrier).

[0236] The electrophotographic photoreceptor is not particularly limited, and examples thereof include a drum-shaped one made of an organic photoreceptor such as polysilane or phthalopolymethine.

[0237] The formation of the electrostatic charge image is performed, for example, by uniformly charging the surface of the electrophotographic photoreceptor by a charging means and imagewise exposing the surface of the electrophotographic photoreceptor by an exposure means. Note that the electrostatic charge image is an image formed on the surface of the electrophotographic photoreceptor by such a charging means.

[0238] The charging means and the exposure means are not particularly limited, and those generally used in the electrophotographic method can be used.

[0239] (Developing step) The developing step is a step of developing the electrostatic latent image with toner (generally, a dry developer containing toner) to form a toner image.

[0240] The formation of the toner image is performed, for example, using a developing means including a stirrer that stirs and charges the toner by friction using a dry developer containing toner, and a rotatable magnetic roller.

[0241] Specifically, in the developing means, for example, the toner and the carrier are mixed and stirred, and the toner is charged by the friction at that time, and is held on the surface of the rotating magnetic roller, and a magnetic brush is formed. Since the magnetic roller is disposed near the electrophotographic photoreceptor, a part of the toner constituting the magnetic brush formed on the surface of the magnetic roller moves to the surface of the electrophotographic photoreceptor by an electric attractive force. As a result, the electrostatic latent image is developed with toner, and a toner image is formed on the surface of the electrophotographic photoreceptor.

[0242] (Transferring step) In this step, the toner image is transferred to the recording medium.

[0243] The transfer of the toner image to the recording medium is performed by peeling and charging the toner image onto the recording medium.

[0244] As the transfer means, for example, a corona transfer device by corona discharge, a transfer belt, a transfer roller, etc. can be used.

[0245] In addition, the transferring step can be performed, for example, by using an intermediate transfer member, first transferring the toner image onto the intermediate transfer member, and then secondarily transferring this toner image onto the recording medium, or by directly transferring the toner image formed on the electrophotographic photoreceptor onto the recording medium.

[0246] (Fixing process) In the fixing process according to the present invention, a recording material onto which an unfixed image (toner image) formed using toner is transferred is passed between a heated fixing belt or fixing roller and a pressure member, thereby fixing the unfixed image onto the recording material. When the fixing belt or fixing roller used is a fixing member according to the present invention, even when the paper output speed of the image forming apparatus is increased (using an image forming apparatus with a copying speed of 70 cpm or more, so-called Segment 5 or higher), it is possible to exhibit high fixing and separation performance and obtain the effect of not causing image unevenness.

[0247] Specifically, as a method of the fixing process, for example, a belt fixing method or a roller fixing method configured by a fixing belt or fixing roller as a fixing rotating body and a pressure roller as a pressure member provided in a state of being pressed against the fixing belt or fixing roller so that a fixing nip portion is formed on the fixing belt or fixing roller can be mentioned.

[0248] (Cleaning process) In this process, the developer that has not been used for image formation or has remained without being transferred is removed from the developer carrier such as the photoreceptor and the intermediate transfer body.

[0249] The cleaning method is not particularly limited, but it is preferably a method using a blade that contacts and rubs the surface of the photoreceptor and is provided in contact with the cleaning target such as the photoreceptor. Preferably, it is a method using a blade that contacts and rubs the surface of the photoreceptor and is provided in contact with the cleaning target such as the photoreceptor.

[0250] In the electrophotographic image forming method of the present invention, an image of colored or black toner is finally transferred and formed onto a recording medium.

[0251] The recording medium is not particularly limited. For example, it can be ordinary paper from thin paper to thick paper, coated printing paper such as high-quality paper, art paper or coated paper, papers such as commercially available Japanese paper and postcard paper; resin films such as polypropylene (PP) film, polyethylene terephthalate (PET) film, and triacetyl cellulose (TAC) film; cloth, etc. However, it is not limited to these. Also, the color of the recording medium is not particularly limited, and recording media of various colors can be used.

[0252] Further, the electrophotographic image forming apparatus of the present invention is an electrophotographic image forming apparatus including at least a charging means for an image carrier, an electrostatic charge image forming means, an electrostatic charge image developing means, a toner image transferring means, a toner image fixing means, and a cleaning means, characterized by using the two-component developer for electrostatic charge image development of the present invention.

[0253] Specifically, an image carrier, a charging means for charging the surface of the image carrier, an electrostatic charge image forming means for forming an electrostatic charge image on the charged surface of the image carrier, a developing means for developing the electrostatic charge image formed on the surface of the image carrier as a toner image using the toner set for electrostatic charge image development of the present invention, a transferring means for transferring the toner image formed on the surface of the image carrier to the surface of a recording medium, a fixing means for fixing the toner image transferred to the surface of the recording medium, and a cleaning means.

[0254] As the electrophotographic image forming apparatus of the present invention, for example, an image forming apparatus as shown in FIG. 1 can be used. FIG. 1 is a schematic cross-sectional view showing the configuration in an example thereof. This image forming apparatus 100 is called a tandem type color image forming apparatus and has four sets of image forming units (image forming units) 10Y, 10M, 10C, and 10Bk arranged vertically in series, an intermediate transfer body unit 7, a paper feeding means 21, and a fixing means 24. An original image reading device SC is arranged above the main body A of the image forming apparatus 100.

[0255] The intermediate transfer unit 7 includes an endless belt-shaped intermediate transfer member 70 that is rotatable by winding rollers 71, 72, 73, and 74, primary transfer rollers 5Y, 5M, 5C, 5Bk, and cleaning means 6b.

[0256] The four sets of image forming units 10Y, 10M, 10C, and 10Bk each have a drum-shaped photoreceptor 1Y, 1M, 1C, and 1Bk at the center, and charging means 2Y, 2M, 2C, and 2Bk, exposure means 3Y, 3M, 3C, and 3Bk, rotating developing means 4Y, 4M, 4C, and 4Bk, and cleaning means 6Y, 6M, 6C, and 6Bk for cleaning the photoreceptors 1Y, 1M, 1C, and 1Bk disposed around them. The image forming apparatus 100 includes the photoreceptors according to the present invention as the photoreceptors 1Y, 1M, 1C, and 1Bk.

[0257] The image forming units 10Y, 10M, 10C, and 10Bk form toner images of yellow, magenta, cyan, and black, respectively. In the image forming system of the present invention, the charging step, the exposure step, and the developing step are steps of forming a toner image on the photoreceptor. In the image forming apparatus 100, the image forming units 10Y, 10M, 10C, 10Bk use the photoreceptors 1Y, 1M, 1C, and 1Bk according to the present invention and the toner according to the present invention, and are performed as follows. Note that the toner can be mixed with the carrier as described above and used as a two-component developer.

[0258] The image forming units 10Y, 10M, 10C, 10Bk have the same configuration except that the colors of the toner images formed on the photoreceptors 1Y, 1M, 1C, 1Bk are different. The image forming unit 10Y will be described in detail as an example.

[0259] The image forming unit 10Y arranges a charging means 2Y, an exposure means 3Y, a developing means 4Y, and a cleaning means 6Y around a photoreceptor 1Y which is an image forming body, and forms a yellow (Y) toner image on the photoreceptor 1Y. Further, in the present embodiment, at least the photoreceptor 1Y, the charging means 2Y, the developing means 4Y, and the cleaning means 6Y among the image forming unit 10Y are provided so as to be integrated.

[0260] The charging means 2Y is a means for applying a uniform potential to the photoreceptor 1Y. In the present invention, examples of the charging means include those of a contact or non-contact roller charging method, etc., but those of the contact roller charging method are preferable in that the effects of the present invention are more effective.

[0261] The exposure means 3Y is a means for performing exposure on the photoreceptor 1Y to which a uniform potential has been applied by the charging means 2Y based on an image signal (yellow), and forming an electrostatic charge image corresponding to the yellow image. As this exposure means 3Y, those composed of an LED in which light emitting elements are arranged in an array in the axial direction of the photoreceptor 1Y and a pixel element, or a laser optical system or the like is used.

[0262] The developing means 4Y includes, for example, a developing sleeve that incorporates a magnet and holds and rotates a two-component developer, and a voltage applying device that applies a DC and / or AC bias voltage between the photoreceptor 1Y and this developing sleeve.

[0263] The cleaning means 6Y is composed of a cleaning blade provided so that the tip abuts on the surface of the photoreceptor 1Y, and a brush roller that contacts the surface of the photoreceptor 1Y and is provided upstream of this cleaning blade. The cleaning blade has a function of removing residual toner adhering to the photoreceptor 1Y and a function of scraping the surface of the photoreceptor 1Y.

[0264] The brush roller has a function of scraping the surface of the photoreceptor 1Y, along with a function of removing residual toner attached to the photoreceptor 1Y and a function of recovering the residual toner removed by the cleaning blade. That is, the brush roller contacts the surface of the photoreceptor 1Y, and at the contact portion, it rotates in the same direction as the photoreceptor 1Y in the advancing direction, removes residual toner and paper dust on the photoreceptor 1Y, and conveys and recovers the residual toner removed by the cleaning blade.

[0265] Here, in the photoreceptor according to the present invention, the memory performance is ensured by containing the charge transport material (1) or (2) in the photosensitive layer included in the photoreceptor. Further, the toner according to the present invention contains lanthanum-doped titanate compound particles as an external additive, whereby the charge amount of the toner is controlled, the adhesion force of the toner to the photoreceptor is weakened, and the removability during cleaning is ensured, and an image forming system excellent in cleaning performance is provided. Thereby, direct damage to the photoreceptor is reduced, and the occurrence of filming due to a decrease in the adhesion force on the photoreceptor is suppressed. In this way, in the image forming system of the present invention, the photoreceptor can maintain high durability while achieving both cleaning performance and memory performance, and thus a high-quality image can be stably supplied even during long-term use.

[0266] In the image forming system using the image forming apparatus 100, the transfer process of transferring the toner image formed on the photoreceptor to the transfer material is as described below. Using an intermediate transfer member, after the toner image is primarily transferred onto the intermediate transfer member, the toner image is secondarily transferred onto the transfer material.

[0267] The toner images of respective colors formed by the image forming units 10Y, 10M, 10C, and 10Bk are sequentially transferred onto the rotatable endless belt-shaped intermediate transfer member 70 included in the intermediate transfer member unit 7 by the primary transfer rollers 5Y, 5M, 5C, and 5Bk as primary transfer means, and a combined color image is formed. The endless belt-shaped intermediate transfer member 70 is a semiconductive endless belt-shaped second image carrier that is wound by a plurality of rollers 71, 72, 73, and 74 and is rotatably supported.

[0268] The color image synthesized on the endless belt-shaped intermediate transfer member 70 is then transferred to a transfer material (image support that carries the fixed final image: for example, plain paper, transparent sheet, etc.) P. Specifically, the transfer material P accommodated in the paper feed cassette 20 is fed by the paper feed means 21 and conveyed to the secondary transfer roller 5b as the secondary transfer means through a plurality of intermediate rollers 22A, 22B, 22C, 22D, and the registration roller 23. Then, at the secondary transfer roller 5b, the color image is batch-transferred (secondary transfer) from the endless belt-shaped intermediate transfer member 70 onto the transfer material P. The transfer material P onto which the color image has been transferred is subjected to a fixing process by the fixing means 24, clamped by the paper discharge roller 25, and placed on the external paper discharge tray 26.

[0269] Examples of the fixing means 24 include those of a heat roller fixing method configured by a heating roller having a heat source inside and a pressure roller provided in a state of being pressed against the heating roller so that a fixing nip portion is formed thereon.

[0270] On the other hand, after the color image is transferred to the transfer material P by the secondary transfer roller 5b as the secondary transfer means, the endless belt-shaped intermediate transfer member 70 from which the transfer material P has been separated by curvature has the residual toner removed by the cleaning means 6b.

[0271] During the image formation process, the primary transfer roller 5Bk is always in contact with the photoreceptor 1Bk. The other primary transfer rollers 5Y, 5M, and 5C are in contact with the corresponding photoreceptors 1Y, 1M, and 1C only during color image formation. The secondary transfer roller 5b is in contact with the endless belt-shaped intermediate transfer member 70 only when the transfer material P passes here and secondary transfer is performed.

[0272] Further, in the image forming apparatus 100, a housing 8 including the image forming units 10Y, 10M, 10C, and 10Bk and the intermediate transfer unit 7 can be pulled out from the apparatus main body A via support rails 82L and 82R.

[0273] Although the image forming system in a color laser printer has been described using the image forming apparatus 100 shown in FIG. 1, the image forming system of the present invention is similarly applicable to a monochrome laser printer or a copying machine. Further, an exposure light source other than a laser, for example, an LED light source may be used.

Example

[0274] Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the examples, the unit of “part” or “%” is used, which represents “part by mass” or “mass %” unless otherwise specified.

[0275] <Preparation of External Additive> <Preparation of External Additives 1 to 12> To silica particles produced by a vapor phase method having a number average primary particle diameter of 30 nm, 3.0 parts by mass of pure water was sprayed while stirring in a nitrogen atmosphere. 15 parts by mass of dimethyldichlorosilane and 1.0 part by mass of diethylamine, which are surface modifiers, were sprayed thereon, and heat stirring was performed at 180° C. for 1 hour, followed by cooling and drying under reduced pressure to obtain External Additive 1. Similarly, for the preparation of External Additives 2 to 12, the surface modifier was changed to the materials described in Table I and the same treatment was performed.

[0276] For External Additive 12, silica particles produced by a vapor phase method having a number average primary particle diameter described in Table I were used, and the same treatment as that for External Additive 1 was performed.

[0277] <Preparation of External Additives 13 to 15> Using the description of JP-A-2012-224542 as a reference, 3.0 parts by mass of pure water was sprayed while stirring alumina particles having a number average primary particle diameter of 30 nm in a nitrogen atmosphere. To this, 20 parts by mass of ethyltrimethoxysilane, which is a surface modifier, and 1.0 part by mass of diethylamine were sprayed, followed by heat stirring at 180 °C for 1 hour, then cooling, and drying under reduced pressure to obtain external additive 14. The number average primary particle diameter was 30 nm.

[0278] External additives 14 and 15 were prepared by changing the surface modifier to the materials described in Table I and performing the same treatment.

[0279] <Preparation of External Additives 16 to 20> 500 parts by mass of methanol was stirred in a 1 L reactor equipped with a stirrer, a dropping funnel, and a thermometer, 10 parts by mass of titanium isopropoxide was added dropwise, and stirring was continued for 10 minutes. Thereafter, the resulting titanium oxide fine particles were separated and recovered by a centrifuge, and after drying under reduced pressure, metatitanic acid having a number average primary particle diameter of 30 nm was obtained. While stirring metatitanic acid in a nitrogen atmosphere, 3.0 parts by mass of pure water was sprayed. To this, 20 parts by mass of ethyltrimethoxysilane, which is a surface modifier, and 1.0 part by mass of diethylamine were sprayed, followed by heat stirring at 180 °C for 1 hour, then cooling, and drying under reduced pressure to obtain external additive 16. Similarly, external additives 17 and 18 were prepared by changing the surface modifier to the materials described in the table and performing the same treatment.

[0280] Further, the obtained metatitanic acid was heated in a high-temperature electric furnace at 800 °C for 5 hours in the atmosphere to obtain titanium oxide fine particles. While stirring the obtained titanium oxide particles in a nitrogen atmosphere, 3.0 parts by mass of pure water was sprayed. To this, 20 parts by mass of ethyltrimethoxysilane, which is a surface modifier, and 1.0 part by mass of diethylamine were sprayed, followed by heat stirring at 180 °C for 1 hour, then cooling, and drying under reduced pressure to obtain external additive 19. Similarly, external additive 20 was prepared by changing the surface modifier to the materials described in Table I and performing the same treatment. The number average primary particle diameter of the titanium oxide fine particles was 30 nm.

[0281] <Preparation of External Additives 21 and 22> The pH of the metatitanic acid dispersion was adjusted to 9.0 with a 4.0 mol / L aqueous sodium hydroxide solution for desulfurization treatment, and then a 6.0 mol / L aqueous hydrochloric acid solution was added to adjust the pH to 5.5 for neutralization treatment. Subsequently, water was added to the metatitanic acid cake prepared by filtering and washing the metatitanic acid dispersion, and it was adjusted to a dispersion corresponding to 1.25 mol / L in terms of titanium dioxide TiO2. Then, the pH was adjusted to 1.2 with a 6.0 mol / L aqueous hydrochloric acid solution. And the temperature of the dispersion was adjusted to 35 °C, and stirring was carried out at this temperature for 1 hour to peptize the metatitanic acid dispersion.

[0282] From the peptized metatitanic acid dispersion, 0.156 mol of metatitanic acid corresponding to titanium dioxide TiO2 was collected and put into a reaction vessel. Subsequently, an aqueous calcium carbonate CaCO3 solution was put into the reaction vessel. At this time, the reaction system was prepared so that the titanium dioxide concentration became 0.156 mol / L. Also, calcium carbonate CaCO3 was added so that the molar ratio to titanium dioxide was 1.15 (CaCO3 / TiO2 = 1.15 / 1.00). Nitrogen gas was supplied into the above reaction vessel and left for 20 minutes to make the inside of the reaction vessel under a nitrogen gas atmosphere, and then the mixed solution composed of metatitanic acid and calcium carbonate was heated to 90 °C. Subsequently, an aqueous sodium hydroxide solution was added over 5 hours until the pH reached 8.0, and then stirring was continued at 90 °C for 1 hour to complete the reaction. After the reaction was completed, the inside of the reaction vessel was cooled to 40 °C, and after removing the supernatant under a nitrogen atmosphere, 2500 parts by mass of pure water was put into the reaction vessel and decantation was repeated twice. After decantation, the reaction system was filtered with a Nutsche to form a cake, and the obtained cake was heated to 110 °C and dried in the air for 8 hours. The dried calcium titanate obtained was put into an alumina crucible and dehydrated and calcined at 930 °C. After the calcination treatment, calcium titanate was put into water, wet pulverized with a sand grinder to obtain a dispersion, and then a 6.0 mol / L aqueous hydrochloric acid solution was added to adjust the pH to 2.0 to remove the excess calcium carbonate.

[0283] After removing the excess calcium carbonate, a diluted solution of ethyltrimethoxysilane or isobutyltrimethoxysilane (10 parts by mass of isobutylsilane / 90 parts by mass of ethanol) was prepared and surface modification treatment was carried out. Under a nitrogen atmosphere, the surface modification treatment was carried out by stirring with a Henschel mixer for 30 minutes. At that time, 5.0 parts by mass of isobutyltrimethoxysilane was added to 100 parts by mass of the calcium titanate solid content for the treatment. After the above wet surface treatment, a 4.0 mol / liter sodium hydroxide aqueous solution was added to adjust the pH to 6.5 for neutralization treatment, and then filtration and washing were carried out, followed by drying treatment at 150 °C. Furthermore, using a mechanical pulverization device, disintegration treatment was carried out for 60 minutes to produce an external additive 21 using calcium titanate. The number average primary particle diameter was 30 nm. The production of the external additive 22 was carried out by changing the surface modification treatment agent to the material described in Table I and performing the same treatment.

[0284] <Measurement of number average primary particle diameter> The number average primary particle diameter was measured by measuring the diameter in a certain direction between two parallel lines in a certain direction sandwiching 200 or more and 500 or less primary particles at a magnification of 30,000 times using a transmission electron microscope (JEOL Ltd. EM-2100), removing the numerical values of the upper 5% and the lower 5%, and obtaining the average value of the remaining 90%, and that value was used.

[0285]

Table 1

[0286] <Production of core particles for carrier particles> Each raw material was blended in an appropriate amount so as to be 19.0 mol% in terms of MnO, 2.8 mol% in terms of MgO, 1.5 mol% in terms of SrO, and 75.0 mol% in terms of Fe2O3. Water was added, and the mixture was pulverized and mixed in a wet ball mill for 10 hours, dried, held at 950 °C for 4 hours, and then the slurry that had been pulverized in a wet ball mill for 24 hours was granulated and dried. 50% of the volume was added into a firing furnace equipped with a stirring device, held at a peripheral speed of 10 m / s and 1400 °C for 4 hours, crushed, and the particle size was adjusted to 32 mm to obtain the core material particles 1 for carrier particles. The shape factor (SF-1) of the core material particles 1 for carrier particles was 140.

[0287] Similarly, the firing temperature was changed under the conditions shown in Table II to produce the core material particles 2 to 6 for carrier particles.

[0288] <Measurement method of shape factor> The shape factor was measured using an image processing analyzer (LUZEX AP: Nireco Corporation) by taking photos of 100 or more particles randomly at 150 times magnification with a scanning electron microscope and capturing the photographed images with a scanner. The shape factor (SF-1) of the core material particles was determined by the following formula (1). Formula (1) SF-1 = (maximum length of the particle) 2 / (projected area of the particle) × (π / 4) × 100 The shape factor indicates the degree of unevenness of the core material particles to be measured, and the value increases as the undulation of the surface unevenness becomes more intense.

[0289]

Table 2

[0290] <Production of resin for coating core material (coating material 1)> In an aqueous solution of 0.3 mass% sodium benzenesulfonate, cyclohexyl methacrylate and methyl methacrylate were added in a molar ratio of 1:1, and potassium persulfate in an amount corresponding to 0.5 mass% of the total amount of the monomers was added to conduct emulsion polymerization. The resin particles in the obtained dispersion were dried by spray-drying the dispersion to produce Coating Material 1 which is a resin for core material coating. The weight-average molecular weight (Mw) of the obtained Coating Material 1 was 500,000. The weight-average molecular weight (Mw) of Coating Material 1 was determined by gel permeation chromatography (GPC).

[0291] <Preparation of Carrier Particles 3> 100 parts by mass of Mn-Mg ferrite particles with a volume-average particle diameter of 32 μm and a shape factor SF-1 of 140 were put into a high-speed stirring mixer with a horizontal stirring blade, and 3.2 parts by mass of Coating Material 1 was added thereto. Mixing and stirring were carried out at 22 °C for 15 minutes under the condition that the peripheral speed of the horizontal rotating blade was 8 m / sec. Then, mixing was carried out at 120 °C for 50 minutes to coat Coating Material 1 on the surface of the above core material particles by the action of mechanical impact force (mechanical chemical method) to produce Carrier Particles 3. The median diameter based on the volume distribution of Carrier Particles 3 was 33 μm. The value of the iron element content rate representing the degree of the exposed area of the core material particles was 8.2%.

[0292] <Measurement of Volume-Average Particle Diameter of Carrier Particles> The volume-average particle diameter of the above carrier particles is a value obtained by measuring by the wet method using a laser diffraction particle size distribution measuring device (manufactured by Nippon Laser Co., Ltd., HELOS KA). Specifically, first, an optical system with a focal position of 200 mm was selected, and the measurement time was set to 5 seconds. Then, the carrier core material for measurement was added to an aqueous solution of 0.2 mass% sodium dodecyl sulfate, and dispersed for 3 minutes using an ultrasonic cleaner (manufactured by asone Co., Ltd., US-1) to prepare a measurement sample dispersion. Several drops of this were supplied to the above laser diffraction particle size distribution measuring device, and measurement was started when the sample concentration gauge reached the measurable region. A cumulative distribution was created from the obtained particle size distribution with respect to the particle size range (channel) from the small diameter side, and the volume-average particle diameter was calculated based on this.

[0293] <Iron element content rate on the surface of carrier particles> The iron element content rate (atomic %) was calculated by the following method. Using Thermo Fisher Scientific's K-Alpha (for the measurement, Al monochromatic X-rays were used as the X-ray source, the acceleration voltage was set to 7 kV, and the emission current was set to 6 mA). By XPS measurement (X-ray photoelectron spectroscopy), the C1s spectrum for carbon, the Fe2p3 / 2 spectrum for iron, and the O1s spectrum for oxygen were measured. Then, based on the spectra of these respective atoms, the contents (atomic %) of Fe, C, and O in the unit area of the carrier particle surface, represented as "AC", "AO", and "AFe" respectively, were determined and calculated from the following formula (2).

[0294] Formula (2) Iron element content rate (atomic %) = A Fe / (A C + A O + A Fe ) (However, A Fe , A C , and A O represent the contents (atomic %) of Fe, C, and O in the unit area of the carrier particle surface, respectively.)

[0295] Similarly, for carrier particles 1, 2, 4 to 11, carrier particles were prepared by changing the type of core material particles and the amount of coating resin as shown in Table III below.

[0296]

Table 3

[0297] <Production of toner base particles> <Preparation of dispersion liquid BK of black colorant fine particles> 90 parts by mass of sodium n-dodecyl sulfate was stirred and dissolved in 1600 parts by mass of ion-exchanged water. While stirring this solution, 420 parts by mass of carbon black "Morgal L" (manufactured by Cabot Corporation, pH 2 (room temperature 25 °C)) was gradually added.

[0298] Next, a dispersion liquid BK of black colorant fine particles in which carbon black particles are dispersed was prepared by performing a dispersion treatment using a stirring device "Clear Mix" (manufactured by M Technique Co., Ltd.). When the particle size of the black colorant fine particles in this dispersion liquid was measured using a microtrack particle size distribution measuring device "UPA-150" (manufactured by Nikkiso Co., Ltd.), the median diameter based on volume was 77 nm.

[0299] (Synthesis of crystalline polyester resin c1) Into a reaction vessel equipped with a stirring device, a nitrogen gas introduction tube, a temperature sensor, and a rectification column, 200 parts by mass of dodecanedioic acid and 102 parts by mass of 1,6-hexanediol were charged, and the temperature of the reaction system was raised to 190 °C over 1 hour, and it was confirmed that the inside of the reaction system was uniformly stirred. Thereafter, 0.3 part by mass of titanium tetrabutoxide as a catalyst was added. Further, while distilling off the generated water, the temperature of the reaction system was raised from 190 °C to 240 °C over 6 hours. Further, a dehydration condensation reaction was continued for 6 hours while maintaining the temperature at 240 °C to carry out a polymerization reaction, and a crystalline polyester resin c1 was obtained.

[0300] The obtained crystalline polyester resin had a weight average molecular weight of 14,500 and a melting point of 70 °C.

[0301] (Measurement of weight average molecular weight) Using a GPC device "HLC-8220" (manufactured by Tosoh Corporation) and a column "TSKguardcolumn + TSKgel SuperHZM-M3 series" (manufactured by Tosoh Corporation), while maintaining the column temperature at 40 °C, tetrahydrofuran (THF) was flowed as a carrier solvent at a flow rate of 0.2 mL / min, 10 μL of a sample solution was injected into the above device, detected using a refractive index detector (RI detector), and the molecular weight distribution of the measurement sample was calculated using a calibration curve measured using monodisperse polystyrene standard particles.

[0302] (Measurement of melting point of crystalline resin) The melting point of the crystalline resin was measured using a differential scanning calorimeter "Diamond DSC" (manufactured by PerkinElmer). 3.0 mg of the sample was sealed in an aluminum pan and set in a holder. An empty aluminum pan was set as a reference. The first heating process was to raise the temperature from 0 °C to 200 °C at a rate of 10 °C / min, the cooling process was to cool from 200 °C to 0 °C at a rate of 10 °C / min, and the second heating process was to raise the temperature from 0 °C to 200 °C at a rate of 10 °C / min. DSC curves were obtained according to the measurement conditions (heating and cooling conditions) in this order. Then, based on this DSC curve, the peak top temperature of the endotherm derived from the crystalline polyester in the first heating process was taken as the melting point.

[0303] <Preparation of Crystalline Polyester Resin Particle Dispersion Liquid C1> 100 parts by mass of the crystalline polyester resin c1 obtained above was dissolved in 400 parts by mass of ethyl acetate and mixed with 638 parts by mass of an aqueous sodium dodecyl sulfate solution with a concentration of 0.26 mass%. While stirring the resulting mixture, ultrasonic dispersion treatment was performed for 30 minutes at V-LEVEL 300 μA using an ultrasonic homogenizer US-150T (manufactured by Nippon Seiki Co., Ltd.).

[0304] Thereafter, while heating to 50 °C, a diaphragm vacuum pump V-700 (manufactured by BUCHI) was used to completely remove ethyl acetate while stirring under reduced pressure for 3 hours to prepare a crystalline polyester resin particle dispersion liquid C1. The crystalline polyester resin particles in the dispersion had a volume-based median diameter of 148 nm.

[0305] <Preparation of Styrene·Acrylic Resin Particle Dispersion Liquid S1 for Core> (First-stage Polymerization) A reaction vessel equipped with a stirring device, a temperature sensor, a cooling pipe, and a nitrogen gas introduction device was charged with 4 parts by mass of sodium dodecyl sulfate and 3000 parts by mass of ion-exchanged water, and while stirring at a stirring speed of 230 rpm under a nitrogen stream, the internal temperature was raised to 80 °C. After the temperature rise, a solution prepared by dissolving 10 parts by mass of potassium persulfate in 200 parts by mass of ion-exchanged water was added, the liquid temperature was set to 80 °C again, and a mixed solution of the following monomers was added dropwise over 2 hours.

[0306] Styrene (St) 570.0 parts by mass n-Butyl acrylate (BA) 165.0 parts by mass Methacrylic acid (MAA) 68.0 parts by mass After the dropwise addition of the above mixed solution, polymerization was carried out by heating and stirring at 80 °C for 2 hours to prepare a styrene-acrylic resin particle dispersion 1-a for the core.

[0307] (Second-stage polymerization) A reaction vessel equipped with a stirring device, a temperature sensor, a cooling pipe, and a nitrogen introduction device was charged with a solution prepared by dissolving 3 parts by mass of polyoxyethylene (2) dodecyl ether sulfate in 1210 parts by mass of ion-exchanged water and heated to 80 °C. After heating, 60 parts by mass of the amorphous vinyl resin particle dispersion 1-a prepared by the above first-stage polymerization in terms of solid content, and a mixed solution prepared by dissolving the following monomers, a chain transfer agent, and a mold release agent at 80 °C were added.

[0308] Styrene (St) 245.0 parts by mass 2-Ethylhexyl acrylate (2EHA) 97.0 parts by mass Methacrylic acid (MAA) 30.0 parts by mass n-Octyl 3-mercaptopropionate 4.0 parts by mass Microcrystalline wax "HNP-0190" (manufactured by Nippon Seiro Co., Ltd.) 170.0 parts by mass

[0309] Using a mechanical disperser CLEARMIX (registered trademark) (manufactured by M Technique Co., Ltd.) having a circulation path, a mixing and dispersion treatment was carried out for 1 hour to prepare a dispersion liquid containing emulsified particles (oil droplets). To this dispersion liquid, a solution of a polymerization initiator in which 5.2 parts by mass of potassium persulfate was dissolved in 200 parts by mass of ion-exchanged water, and 1000 parts by mass of ion-exchanged water were added, and polymerization was carried out by heating and stirring this system at 84 ° C for 1 hour to prepare a core styrene-acrylic resin particle dispersion liquid 1-b.

[0310] (Third-stage polymerization) To the core styrene-acrylic resin particle dispersion liquid 1-b obtained by the above second-stage polymerization, a solution in which 7 parts by mass of potassium persulfate was dissolved in 130 parts by mass of ion-exchanged water was added. Further, under a temperature condition of 82 ° C, a mixed liquid of the following monomers and a chain transfer agent was added dropwise over 1 hour.

[0311] Styrene (St) 350 parts by mass Methyl methacrylate (MMA) 50 parts by mass n-Butyl acrylate (BA) 170 parts by mass Methacrylic acid (MAA) 35 parts by mass n-Octyl-3-mercaptopropionate 8.0 parts by mass

[0312] After completion of the dropwise addition, polymerization was carried out by heating and stirring for 2 hours, and then cooled to 28 ° C to prepare a core styrene-acrylic resin particle dispersion liquid S1. The styrene-acrylic resin particles in the dispersion liquid had a median diameter of 145 nm on a volume basis. Further, the weight average molecular weight of the obtained styrene-acrylic resin was 35000, and the glass transition temperature (Tg) was 37 ° C.

[0313] (Measurement of glass transition temperature) The glass transition point is a value measured by the method (DSC method) defined in ASTM (American Society for Testing and Materials Standard) D3418-82.

[0314] Specifically, 4.5 mg of the sample was accurately weighed to two decimal places, sealed in an aluminum pan, and set in the sample holder of a differential scanning calorimeter "DSC8500" (manufactured by PerkinElmer). As a reference, an empty aluminum pan was used, and temperature control of Heat-Cool-Heat was performed at a measurement temperature of -0 to 120 °C, a heating rate of 10 °C / min, and a cooling rate of 10 °C / min, and analysis was performed based on the data in its 2nd. Heat. The value of the intersection point between the extension line of the baseline before the rise of the first endothermic peak and the tangent line indicating the maximum slope between the rising part of the first endothermic peak and the peak apex was defined as the glass transition temperature.

[0315] <Synthesis of Amorphous Polyester Resin> (Synthesis of Styrene·Acrylic Modified Polyester Resin A1) Into a 10-liter four-necked flask equipped with a nitrogen inlet tube, a water removal tube, a stirrer, and a thermocouple, 500 parts by mass of bisphenol A propylene oxide 2 mol adduct 117 parts by mass of terephthalic acid 82 parts by mass of fumaric acid 2 parts by mass of an esterification catalyst (tin octylate) were placed, and a polycondensation reaction was carried out at 230 °C for 8 hours, followed by cooling to obtain amorphous polyester resin A1.

[0316] (Synthesis of Styrene·Acrylic Modified Polyester Resin B1) Into a 10-liter four-necked flask equipped with a nitrogen inlet tube, a water removal tube, a stirrer, and a thermocouple, 500 parts by mass of bisphenol A propylene oxide 2 mol adduct 117 parts by mass of terephthalic acid 82 parts by mass of fumaric acid 2 parts by mass of an esterification catalyst (tin octylate) were placed, and a polycondensation reaction was carried out at 230 °C for 8 hours, and further reacted at 8 kPa for 1 hour. After cooling to 160 °C, 10 parts by mass of acrylic acid 15 parts by mass of styrene 4 parts by mass of butyl acrylate 10 parts by mass of a polymerization initiator (di-t-butyl peroxide) The mixture was added dropwise over 1 hour using a dropping funnel. After the addition, while maintaining the temperature at 160°C, the polymerization reaction was continued for 1 hour, then the temperature was raised to 200°C and held at 10 kPa for 1 hour, and then acrylic acid, styrene, and butyl acrylate were removed to obtain styrene-acrylic modified polyester resin B1.

[0317] (Synthesis of styrene-acrylic modified polyester resins B2 to B5) Styrene-acrylic modified polyester resins B2 to B5 were prepared by changing the monomer amounts in Table IV below (in the table, St represents styrene and Ac represents acrylic).

[0318] [Table 4]

[0319] ><Preparation of polyester resin particle dispersion D1>[[]] 100 parts by mass of the amorphous polyester resin A1 obtained above was dissolved in 400 parts by mass of ethyl acetate and mixed with 638 parts by mass of an aqueous sodium dodecyl sulfate solution having a concentration of 0.26% by mass prepared in advance. While stirring the resulting mixture, ultrasonic dispersion treatment was performed at V-LEVEL 300 μA for 30 minutes using an ultrasonic homogenizer US-150T (manufactured by Nippon Seiki Co., Ltd.).

[0320] Thereafter, while heating to 50°C, a diaphragm vacuum pump V-700 (manufactured by BUCHI) was used to completely remove ethyl acetate while stirring under reduced pressure for 3 hours to prepare an amorphous polyester resin particle dispersion D1. The amorphous polyester resin particles in the dispersion had a median diameter of 180 nm based on volume.

[0321] ><Preparation of toner base particles 1 (aggregation / fusion step)>[[]] ​​In a 5L reaction vessel equipped with a stirring device, a temperature sensor, a cooling pipe, and a nitrogen introduction device, 405 g (in terms of solid content) of a dispersion of core resin fine particles S1, 45 g (in terms of solid content) of a dispersion of crystalline polyester resin particles C1, 1100 g of ion-exchanged water, and 50 g of a dispersion of colorant fine particles BK were charged. After adjusting the temperature of the obtained dispersion to 30°C, a 5N aqueous sodium hydroxide solution was added to the dispersion to adjust the pH of the dispersion to 10. Next, an aqueous solution prepared by dissolving 60 g of magnesium chloride in 60 g of ion-exchanged water was added to the above dispersion at 30°C over 10 minutes with stirring. After the addition, the dispersion was held at 30°C for 3 minutes and then the temperature was raised. The above dispersion was heated to 85°C over 60 minutes, and the particle growth reaction was continued while maintaining the temperature of the dispersion at 85°C to prepare a dispersion of pre-core particles (1). 50 g (in terms of solid content) of shell resin fine particles D1 was added thereto, and stirring was continued at 80°C for 1 hour to fuse the shell resin fine particles D1 to the surface of the core particles (1) to form a shell layer and obtain resin particles 1. Here, an aqueous solution prepared by dissolving 150 g of sodium chloride in 600 g of ion-exchanged water was added to the obtained dispersion, and aging treatment was performed at a liquid temperature of 80°C. The dispersion was cooled to 30°C when the average circularity of the resin particles 1 reached 0.970. The median diameter of the toner mother particles 1 after cooling was 5.5 μm. Toner mother particles 2 to 6 were prepared by changing the resin in the shell part as shown in Table V below.

[0322]

Table 5

[0323] <Preparation of Toner Particles 1 (External Additive Treatment Step)> The following external additives were added to the toner mother particles 3, and they were added to a Henschel mixer model "FM20C / I" (manufactured by Nippon Coke & Engineering Co., Ltd.). The rotational speed of the stirring blades was set so that the peripheral speed at the tip of the blades was 40 m / s, and stirring was performed for 15 minutes to prepare toner particles 1.

[0324] External Additive 1 1.5 parts by mass

[0325] Note that the temperature during mixing the external additive with the toner particles 1 was set to be 40°C ± 1°C. When the temperature reached 41°C, cooling water was flowed into the outer bath of the Henschel mixer at a flow rate of 5 L / min. When the temperature reached 39°C, cooling water was flowed so that the flow rate of the cooling water became 1 L / min, thereby controlling the temperature inside the Henschel mixer.

[0326] <Production of Toner Particles 2 to 29 (External Additive Treatment Step)> In the same manner as the production of toner particles 1, the external additive treatment shown in Table VI was performed to produce toner particles 2 to 29.

[0327] [Table 6]

[0328] <Production of Two-Component Developer 1> Toner particles 1 and carrier particles 3 were mixed in a V-type mixer for 30 minutes so that the toner content (toner concentration) in the two-component developer was 6% by mass to obtain two-component developer 1.

[0329] <Production of Two-Component Developers 2 to 40> In the same manner as the production of two-component developer 1, two-component developers 2 to 40 were produced with the configurations described in Tables VII and VIII.

[0330] <Evaluation> The following evaluations were performed using the produced two-component developers 1 to 40.

[0331] As an evaluation apparatus, a commercially available digital full-color multifunction printer "bizhub PRESS 1070" (manufactured by Konica Minolta, Inc., "bizhub" is a registered trademark of the company) was used. Each of the produced two-component developers was loaded, and the following evaluations were carried out. In this evaluation apparatus, printing was performed by an electrophotographic image forming method having a charging step, an exposure step, a developing step, and a transfer step.

[0332] (Evaluation of Fog) After printing 100,000 solid-color charts with a printing rate of 40% under the environment of 30°C and 85% RH, white paper was printed and evaluated by the density of the white paper. Twenty density values were measured on A4 size paper, and the average value was taken as the white paper density. The density measurement was performed using X-Rite938 (manufactured by X-Rite). In the following judgment criteria, "◎" or "○" was regarded as passing. ◎: White paper density is less than 0.005 ○: White paper density is 0.005 or more and less than 0.02 ×: White paper density is 0.02 or more

[0333] (Evaluation of image density variation) After printing 100,000 solid-color charts with a printing rate of 40% under the environment of 10°C and 10% RH, an image pattern in which solid patches with a size of 2 cm square were arranged at intervals of one circumference of the developing sleeve was output. The density difference between one circumference of the sleeve (a) and two weeks later (b) was measured using X-Rite938 (manufactured by X-Rite). In the following judgment criteria, "◎" or "○" was regarded as passing. ◎: Density difference Δ is less than 0.005 ○: Density difference Δ is 0.005 or more and less than 0.02 ×: Density difference Δ is 0.02 or more

[0334]

Table 1

[0335]

Table 2

[0336] From Table VII and Table VIII, it can be seen that Examples 1 to 31 of the two-component developer for electrostatic charge image development according to the present invention have improved charging rise characteristics and suppressed fog generation compared to Comparative Examples 1 to 9, and the charge amount of the toner is stable even under environmental variations, and they are excellent in resistance to image density variation.

Explanation of reference numerals

[0337] 101 Conductive support 102 Intermediate layer 103 Photosensitive layer 103a Charge generation layer 103b Charge transport layer 103c Surface protection layer 100 Image forming apparatus 1A, 1B, 1Y, 1M, 1C, 1Bk Photoreceptor 2Y, 2M, 2C, 2Bk Charging means 3Y, 3M, 3C, 3Bk Exposure means 4Y, 4M, 4C, 4Bk Developing means 5Y, 5M, 5C, 5Bk Primary transfer roller 5b Secondary transfer roller 6Y, 6M, 6C, 6Bk, 6b Cleaning means 7 Intermediate transfer unit 8 Housing 10Y, 10M, 10C, 10Bk Image forming unit 21 Paper feeding means 20 Paper feed cassette 22A, 22B, 22C, 22D Intermediate roller 23 Registration roller 24 Fixing means 25 Paper discharge roller 26 Paper discharge tray 70 Endless belt-shaped intermediate transfer member 71, 72, 73, 74 Roller 82L, 82R Support rail P Transfer material

Claims

1. A two-component developer for electrostatic charge image development containing toner particles including toner base particles and external additives disposed on the surfaces of the toner base particles, and carrier particles having core particles and a coating portion disposed on the surfaces of the core particles, wherein the external additives contain silica particles surface-modified with a surface modifier represented by the following general formula (1), and a two-component developer for electrostatic charge image development, characterized in that the value of the iron element content rate (atomic %) measured by X-ray photoelectron spectroscopy (XPS) on the surface of the carrier particles satisfies the following formula (1). General formula (1): (R １ ) ４－ｎ -Si-(X) ｎ [R １ represents an ethyl group, an n-propyl group or an n-butyl group. X is a halogeno group or an alkoxy group, and they may be the same or different from each other. n represents an integer from 1 to 3.] Formula (1) 8.0 ≦ {A Ｆｅ / (A Ｃ + A Ｏ + A Ｆｅ )} × 100 ≦ 15.0 (However, A Ｆｅ , A Ｃ , and A Ｏ represent the contents (atomic %) of Fe, C, and O in the unit area of the carrier particle surface, respectively.)

2. The two-component developer for electrostatic charge image development according to claim 1, wherein the shape factor (SF-1) of the core particles is in the range of 115 to 150.

3. The two-component developer for electrostatic charge image development according to claim 1 or claim 2, wherein the toner base particles have a core-shell structure.

4. The two-component developer for electrostatic charge image development according to claim 3, wherein in the core-shell structure, the core portion is mainly composed of an amorphous vinyl resin and the shell portion is mainly composed of an amorphous polyester resin.

5. An electrophotographic image forming method having at least a charging step of an image carrier, an electrostatic charge image forming step, an electrostatic charge image developing step, a toner image transfer step, a toner image fixing step, and a cleaning step, characterized by using the two-component developer for electrostatic charge image development according to any one of claims 1 to 4.

6. An electrophotographic image forming apparatus including at least a charging means for an image carrier, an electrostatic charge image forming means, an electrostatic charge image developing means, a toner image transfer means, a toner image fixing means, and a cleaning means, characterized by using the two-component developer for electrostatic charge image development according to any one of claims 1 to 4.

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