Electrophotographic image forming carrier, electrophotographic image forming developer, electrophotographic image forming method, electrophotographic image forming apparatus, and process cartridge

Abstract

The present invention provides an electrophotographic image forming carrier including core material particles and a coating layer coating the core material particles, the coating layer containing chargeable particles, the carrier having an internal porosity of 0.0% or greater but less than 2.0%, and an apparent density of 2.0 g / cm 3 or greater but less than 2.5 g / cm 3 .

Description

TECHNICAL FIELD

[0001] The present application relates to a carrier for electrophotographic image formation, a developer for electrophotographic image formation, an electrophotographic image formation method, an electrophotographic image formation apparatus, and a process cartridge. BACKGROUND

[0002] Generally, in an image forming method such as electrophotography and electrostatic photography, in order to develop an electrostatic latent image formed on a latent image carrier, a developer obtained by mixing a toner and a carrier by stirring is used. The developer is required to be a mixture that is properly charged. As an electrostatic latent image developing method, a method using a two-component developer obtained by mixing a toner and a carrier (hereinafter referred to as "two-component developing system") and another method using a one-component developer containing no carrier (hereinafter referred to as "one-component developing system") are known. The two-component developing system is superior to the one-component developing system in terms of maintaining high image quality for a long period of time because the carrier provides a wide area of triboelectric charging against the toner and has a stable charging ability. The two-component developing system is generally used particularly for high-speed machines because the ability to supply toner to a developing area is high. In addition, due to the above-described advantages, the two-component developing system is widely used in a digital electrophotographic system in which an electrostatic latent image is formed on a photosensitive body with a laser beam.

[0003] In order to improve the durability of the carrier used in such a two-component developing system, various attempts have been made, for example, in order to prevent used toner from adhering to the surface of the carrier, to form a uniform surface on the carrier, to prevent surface oxidation, to prevent moisture sensitivity from decreasing, to extend the life of the developer, to protect the photosensitive body from scratches or wear by the carrier, to control the polarity of the electric charge, or to adjust the amount of electric charge, a carrier coated with a specific resin material (Patent Literature 1), a carrier in which various additives are added to the coating layer (Patent Literatures 2 to 8), and a carrier in which an additive is attached to the surface of the carrier (Patent Literature 9) have been proposed. As another example, in Patent Literature 10, a carrier coated with a carrier coating layer material composed of a guanamine resin and a thermosetting resin capable of cross-linking with the guanamine resin is proposed, and in Patent Literature 11, a carrier coated with a carrier coating layer material composed of a cross-linking product of a melamine resin and an acrylic resin is also proposed.

[0004] In Patent Literatures 12 to 15, a resin-coated carrier in which electrically conductive carbon and / or an electrically conductive filler as an electrically conductive agent are dispersed in the carrier coating layer is also proposed.

[0005] Further, Patent Literature 16 discloses a support having a coating layer containing first conductive particles and second conductive particles, wherein the first conductive particles are metal oxide particles, and the second conductive particles are metal oxide particles and / or whose surface is conductively treated. As another example, Patent Literature 17 and Patent Literature 18 disclose a support containing barium sulfate in a coating layer film, and the ratio of Ba / Si determined by XPS is 0.01 to 0.08 relative to all elements. Patent Literature 19 describes an example using barium sulfate as a base material.

[0006] Patent Literature 20 attributes the cause of ghosting to an increase in developing potential caused by toner adhering to a developer carrier (e.g., a developing sleeve) (referred to as "sleeve contamination") when the developer carrier faces a non-image portion on a latent image carrier as it passes through a developing region. Patent Literature 20 proposes a developing device in which the coefficient of friction of the surface layer of the developer carrier is reduced, and the AC component of the voltage applied to the developer carrier is adjusted to suppress the occurrence of sleeve contamination, thereby preventing ghosting.

[0007] List of Citations

[0008] Patent Literature

[0009]

Patent Literature 1

[0010]

Patent Literature 2

[0011]

Patent Literature 3

[0012]

Patent Literature 4

[0013]

Patent Literature 5

[0014]

Patent Literature 6

[0015]

Patent Literature 7

[0016]

Patent Literature 8

[0017]

Patent Literature 9

[0018]

Patent Literature 10

[0019]

Patent Literature 11

[0020]

Patent Literature 12

[0021] [Patent Document 13] JP-H04-360156-A

[0022] [Patent Document 14] JP-H05-303238-A

[0023] [Patent Document 15] JP-H011-174740-A

[0024] [Patent Document 16] JP-2010-117519-A

[0025] [Patent Document 17] JP-5534409-B

[0026] [Patent Document 18] JP-2011-209678-A

[0027] [Patent Document 19] JP-2006-079022-A

[0028] [Patent Document 20] JP-6222553-B SUMMARY

[0029] TECHNICAL PROBLEM

[0030] An object of the present application is to provide an electrophotographic image forming carrier having resistance to carrier attachment (i.e., ability not to cause carrier attachment) and resistance to ghosting (i.e., ability not to cause ghosting) while maintaining a stable charge-attaching ability over a long period of use.

[0031] SOLUTION TO THE PROBLEM

[0032] The above problem can be solved by the following Embodiment 1).

[0033] 1) An electrophotographic image forming carrier comprising core material particles and a coating layer coating the core material particles,

[0034] wherein the carrier has an internal porosity of 0.0% or more but less than 2.0%, and an apparent density of 2.0 g / cm3 or more but less than 2.5 g / cm3, and the coating layer contains chargeable particles. 3 3

[0035] ADVANTAGEOUS EFFECTS OF THE INVENTION

[0036] According to some embodiments of the present application, an electrophotographic image forming carrier having resistance to carrier attachment (i.e., ability not to cause carrier attachment) and resistance to ghosting (i.e., ability not to cause ghosting) while maintaining a stable charge-attaching ability over a long period of use can be provided. BRIEF DESCRIPTION OF DRAWINGS

[0037] ​​The accompanying drawings are intended to depict embodiments of the application and should not be interpreted to limit the scope thereof. The drawings are intended for use with the explanations in the detailed description and serve to illustrate the principles of the application. The same or similar components in the drawings are denoted by the same or similar reference numerals.

[0038] Figure 1 is a schematic view illustrating a process cartridge according to an embodiment of the present application. DETAILED DESCRIPTION

[0039] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0040] In describing the embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that have a similar function, operate in a similar manner and achieve a similar result.

[0041] Embodiments of the present application are described in detail below.

[0042] In addition to the above-described embodiment 1), the present application can be achieved by the following embodiments 2) to 11).

[0043] 2) The carrier of 1) above, wherein the chargeable particles include at least one component selected from the group consisting of barium sulfate, zinc oxide, magnesium oxide, magnesium hydroxide, and hydrotalcite.

[0044] According to this embodiment 2), the chargeable particles exhibit good positive charging properties, and thus, an electrophotographic image forming carrier that is effective in stably imparting charging to a negatively chargeable toner over a long period of use can be provided.

[0045] 3) The carrier of 1) or 2) above, wherein the chargeable particles include barium sulfate, and the amount of barium exposed on the surface of the coating layer is 0.1 atom% or more.

[0046] According to this embodiment 3), the highly chargeable particles are located on the surface of the carrier that contributes most to charging, and thus, an electrophotographic image forming carrier that more effectively exhibits a charging imparting ability can be provided.

[0047] 4) The carrier of any one of 1) to 3) above, wherein the core material particles include a manganese ferrite (hereinafter referred to as "Mn ferrite").

[0048] According to this embodiment 4), the magnetization of the core material particles can be increased, and an electrophotographic image forming carrier that is improved in resistance to carrier adhesion can be provided.

[0049] 5) The carrier according to any one of the above 1) to 4), wherein the core material particles have a surface roughness Rz of 2.0 μm or more but less than 3.0 μm.

[0050] According to this embodiment 5), even when the internal voids are small, it is easy to keep the apparent density of the carrier low, and thus, it is possible to provide a carrier for electrophotographic image formation that has higher resistance to carrier adhesion and resistance to ghosting.

[0051] 6) The carrier according to any one of the above 1) to 5), wherein the carrier has a magnetic flux of 56 Am 2 / kg or more but less than 73 Am 2 / kg in a magnetic field of 1000 Oe equal to 79.58 kA / m.

[0052] According to this embodiment 6), it is possible to provide a carrier for electrophotographic image formation that has high resistance to carrier adhesion, suppresses abnormal images due to carrying of the developer on the developer carrier, and also maintains excellent chargeability over a long period of use.

[0053] 7) The carrier according to any one of the above 1) to 6), wherein the coating layer contains inorganic particles in addition to the chargeable particles, wherein the inorganic particles include at least one selected from the group consisting of:

[0054] element-doped tin oxide particles selected from the group consisting of tungsten, indium, phosphorus, tungsten oxide, indium oxide, and phosphorus oxide; and

[0055] particles that contain the base particles and have the tin oxide doped on the surface of the base particles.

[0056] According to this embodiment 7), even when the coating layer is gradually scraped off over a long period of use, since the inorganic particles that function as a resistance adjusting agent are less colored when they are detached from the surface of the carrier, it is possible to prevent color contamination to the toner.

[0057] 8) A developer for electrophotographic image formation comprising the carrier according to any one of the above 1) to 7).

[0058] According to this embodiment 8), it is possible to provide a developer that develops an electrostatic latent image using the carrier according to the embodiments of the present application, which has excellent resistance to carrier adhesion and resistance to ghosting.

[0059] 9) An electrophotographic image forming method of forming an image using the developer according to the above 8).

[0060] According to this embodiment 9), the carrier and the developer according to some embodiments of the present application are able to form an image that has excellent resistance to carrier adhesion and resistance to ghosting.

[0061] 10) An electrophotographic image forming apparatus comprising the developer of 8) above.

[0062] According to this embodiment 10), an apparatus for forming an image using the carrier and the developer according to some embodiments of the present application can be provided, which can provide excellent carrier adhesion resistance and ghosting resistance.

[0063] 11) A process cartridge comprising the developer of 8) above.

[0064] According to this embodiment 11), a detachably mounted process cartridge can form an image together with the carrier and the developer according to some embodiments of the present application, which can provide excellent carrier adhesion resistance and ghosting resistance.

[0065] The inventors of the present application have conducted earnest studies to solve the above problems.

[0066] As a result, they have found that the above problems can be solved by an electrophotographic image forming carrier (hereinafter simply referred to as "carrier") comprising core material particles and a coating layer coating the core material particles, the carrier having an internal porosity of 0.0% or more but less than 2.0%, and an apparent density of 2.0 g / cm 3 or more but less than 2.5 g / cm 3 , the coating layer containing chargeable particles.

[0067] As described above, when the carrier contains chargeable particles in the coating layer, the charging ability of the carrier is inhibited from decreasing during supply and consumption of toner in a high image area due to the charge imparting function of the chargeable particles, but, since the magnetic moment of one carrier particle becomes smaller, the magnetic bonding force received by the developer carrier becomes lower, and thus there is a disadvantage that the carrier adhesion resistance becomes lower.

[0068] The magnetic moment of the carrier is mainly dependent on the magnetization of the core material particles (hereinafter sometimes referred to as "core material"). The magnetization itself is determined by the core material composition, and thus, in order to increase the magnetic moment of each core material particle to compensate for the decrease in magnetic moment caused by the chargeable particles, it is effective to increase the mass of each core material particle as much as possible.

[0069] On the other hand, as described above, ghosting occurs due to the development potential increase caused by sleeve contamination, but even in the case where the same degree of sleeve contamination occurs, the carrier having a lower apparent density is more capable of reducing the degree of ghosting. This is because the lower the apparent density of the carrier, the higher the space occupancy of the carrier in the development area (i.e., the space between the latent image carrier and the developing sleeve), and the lower the bulk resistance of the carrier. It is considered that when the bulk resistance of the carrier is low, mirror charges easily move in the carrier in a direction to cancel the potential increase caused by sleeve contamination, thereby mitigating the potential increase and inhibiting the occurrence of ghosting. In other words, when the apparent density of the carrier increases, ghosting is more likely to occur.

[0070] One of the factors that determines the bulk carrier apparent density is the mass of one carrier particle. The bulk carrier apparent density tends to increase as the mass of one carrier particle increases, and thus, it is difficult to maintain a low bulk carrier apparent density while increasing the mass of one carrier particle, and thus, there is a balance between the carrier adhesion resistance and the ghost resistance, and it is difficult to achieve a high level of both the carrier adhesion resistance and the ghost resistance.

[0071] The inventors of the present application have extensively studied this problem and found that, even in the case of a carrier in which the magnetic moment tends to decrease due to the inclusion of chargeable particles in the coating layer, in order to maximize the mass of one carrier particle while minimizing the increase in the apparent density, it is effective to increase the magnetic moment of one carrier particle and to reduce the internal porosity of the core material to less than 2.0%.

[0072] It has also been found that, even in the case of a carrier using such a core material, by reducing the apparent density of the carrier to less than 2.5 g / cm 3 , the generation of ghosts can also be suppressed.

[0073] However, merely reducing the internal porosity of the core material to less than 2.0% can increase the apparent density of the carrier, and in particular, when a ferrite particle having a relatively high magnetization is used as the core material in order to obtain a magnetic moment, it is difficult to reduce the apparent density of the carrier to less than 2.5 g / cm 3 . The inventors of the present application have conducted studies to overcome this contradiction. As a result, the inventors of the present application have concluded that, even if the internal porosity is reduced to less than 2.0%, the apparent density of the carrier can be controlled by using other factors that do not impair the mass of one carrier particle, and the apparent density of the carrier can be reduced to less than 2.5 g / cm 3 . The generation of ghosts can also be suppressed. For example, when the surface roughness of the carrier increases, the apparent density can be reduced without impairing the mass of one carrier particle, and the apparent density of the carrier can be reduced to less than 2.5 g / cm

[0074] In order to improve the effects of the present application, the internal porosity of the carrier is preferably 0.3% or more but 1.9% or less, and / or the apparent density of the carrier is preferably 2.0 g / cm 3 or more but 2.3 g / cm 3 or less.

[0075] The surface roughness of the carrier is greatly influenced by the surface roughness of the core material. Among various surface roughness indices, Rz (maximum height) has the greatest influence on the apparent density. The inventors have found that when the Rz of the core material is 2.0 μm or greater, the apparent density of the resulting carrier can be more effectively reduced. When the Rz is less than 3.0 μm, the projections and recesses on the surface of the core material are not too large, the projected portions of the core material are not likely to be exposed on the surface of the carrier during long-term use of the carrier, the service life of the carrier is not likely to be reduced, and therefore, the Rz is preferably 2.0 μm or greater but less than 3.0 μm. More preferably, the Rz is 2.1 μm or greater but 2.9 μm or less.

[0076] The Rz of the core material refers to the maximum height Rz of the surface shape (roughness curve) defined in Japanese Industrial Standards (JIS) B0601:2001 (ISO 1365-1).

[0077] Since the carrier according to one embodiment of the present application contains chargeable particles in the coating layer, the chargeability of the carrier is suppressed from decreasing during the supply and consumption of toner with a high image area due to the chargeability-imparting function of the chargeable particles, thereby suppressing the occurrence of abnormal phenomena such as toner scattering and background staining due to a decrease in charge.

[0078] The chargeable particles refer to particles having a relatively low ionization potential, and more specifically, particles having the same ionization potential as that of alumina particles (AA-03, manufactured by Sumitomo Chemical Co., Ltd.) or particles having a lower ionization potential than that of alumina particles. Preferred materials include barium sulfate, zinc oxide, magnesium oxide, magnesium hydroxide, and hydrotalcite, and particularly suitable materials include barium sulfate. The ionization potential is measured using PYS-202 manufactured by Sumitomo Heavy Industries, Ltd.

[0079] The proportion of the chargeable particles in the coating layer is preferably 3 to 50 mass%, and more preferably 6 to 27 mass%.

[0080] When barium sulfate is used as the chargeable particles, the amount of barium exposed on the surface of the coating layer is preferably 0.1 atom% or greater. Since charge exchange for charging toner is performed on the surface of the coating layer, in a carrier in which barium sulfate is appropriately exposed on the surface of the coating layer, the chargeability of the barium sulfate can be greatly exerted even during long-term use of the carrier, even if the coating layer is not largely scraped off. When the amount of barium exposed on the surface of the coating layer is 0.1 atom% or greater, the chargeability can be exerted not only when the coating layer is scraped off, but also when used toner components are attached to the surface layer of the carrier. The amount of barium exposed on the surface of the coating layer is more preferably 0.1 to 0.2 atom%.

[0081] The exposed amount of barium sulfate on the surface layer of the carrier was measured by peak analysis using an instrument AXIS / ULTRA (manufactured by Shimadzu / KRATOS). The light beam irradiation area of the instrument was about 900 μm x 600 μm, and the measurement was performed at 17 light beam irradiation areas per one of 25 carrier particles. The penetration depth was 0 to 10 nm, and the information near the surface layer of the carrier was detected.

[0082] Specifically, the measurement was performed by setting the measurement mode to Al: 1486.6 eV, setting the excitation source to monochromatic (Al), setting the detection method to spectrum mode, and setting the magnetic lens to OFF. First, the detection elements were identified by wide-range scanning, and then the peak of each detection element was detected by narrow-range scanning. Then, the atomic percentage of barium with respect to all the detection elements was calculated using the peak analysis software program attached to the instrument.

[0083] The particle diameter of the chargeable particles is not particularly limited, but when the average thickness of the coating layer is T, the particle diameter h preferably satisfies the following formula: h / 2 ≤ T ≤ h. By making the particle diameter of the chargeable particles larger than the thickness of the coating layer, the chargeable particles are more likely to protrude from the surface of the coating layer. When the top of the chargeable particles protrudes from the coating layer, when the carrier particles rub against each other or against the wall of the housing container or the conveying means, the chargeable particles function as a spacer between the rubbed object and the resin of the coating layer, thereby prolonging the life of the coating layer. In addition, the chargeable particles are more likely to come into contact with the toner, which is also preferable from the viewpoint of imparting a chargeability function. Furthermore, when the thickness T of the coating layer is larger than half the particle diameter of the chargeable particles, the chargeable particles are firmly captured in the coating layer, so that the chargeable particles are less likely to protrude from the coating layer.

[0084] The particle diameter of the chargeable particles can be measured by a conventionally known method. For example, before the carrier is manufactured, the particle diameter of the chargeable particles can be measured by using NANOTRAC UPA series (manufactured by RIGAKU). As another example, after the carrier is manufactured, the particle diameter can be measured by cutting the coating layer on the surface of the carrier with FIB (focused ion beam), and observing the cross section by scanning electron microscope (SEM) and / or energy dispersive X-ray spectrometry (EDX). Another non-limiting example method is described below.

[0085] The support was mixed with an embedding agent (DEVCON, available from ITW PP&F JAPAN Co., Ltd., two-component mixture, 30-minute curable epoxy resin), left overnight or longer to cure, and mechanically polished to prepare a rough cross-section sample. The cross-section was finished with a cross-section polisher (SM-09010 manufactured by JEOL Ltd.) at an acceleration voltage of 5.0 kV and a beam current of 120 μA. The cross-section was photographed with a scanning electron microscope (MERLIN, available from Carl Zeiss Co., Ltd.) at an acceleration voltage of 0.8 kV and a magnification of 30,000 times. The photographed image was taken into a TIFF (Tagged Image File Format) image, and the equivalent circle diameters of 100 barium sulfate particles were measured using IMAGE-PRO PLUS manufactured by Media Cybernetics, Inc., and the measured values were averaged.

[0086] The measurement method is not limited to the above method, and the thickness of the coating layer can be measured from the image photographed in the same manner. Since each particle has individual differences, and the thickness of the coating layer varies depending on the position, the measurement is not performed on one particle or one position, but on a statistically reliable number of particles or positions.

[0087] The support according to the embodiment of the present application has an internal porosity of 0.0% or more but less than 2.0%. As described above, when the internal porosity is 2.0% or more, the magnetic moment of each particle is lost, and the resistance to support adhesion is reduced.

[0088] The internal porosity of the support can be measured as follows:

[0089] First, the support is cut, and a cross-section is photographed. The cross-section can be photographed by a known method such as SEM (scanning electron microscope). Next, the outline area S of one particle is obtained from the cross-section photograph using known image analysis software (for example, IMAGE PRO PREMIER manufactured by Media Cybernetics, Inc.). Similarly, the area s of the internal void portion of one particle is obtained, and the porosity of one particle is calculated by the following equation.

[0090] Porosity of one particle [%] = (s / S) x 100

[0091] This process is performed on 60 randomly selected particles, and the average value is taken as the internal porosity.

[0092] The support according to the embodiment of the present application has an apparent density of 2.0 g / cm3 3 or more but less than 2.5 g / cm3 3 As described above, when the apparent density of the support is 2.5 g / cm3 3or more, the space occupancy of the carrier particles in the developing region becomes low when the image is developed from the developing roller to the image carrier, and thus, the electric charge is difficult to move in the developing region via the carrier, and also difficult to reduce the potential rise caused by the toner adhering to the developing sleeve, resulting in easy generation of ghosting. Further, when the apparent density is less than 2.0 g / cm 3 when the apparent density is less than 2.0 g / cm

[0093] Further, the inventors of the present application have found that when the chargeable particles are contained in the coating layer, the internal porosity is less than 2.0%, and the apparent density is less than 2.5 g / cm3, as in the carrier according to the embodiment of the present application, the charging ability can be more effectively maintained during long-term use.

[0094] Although the specific reason is not clear, it can be considered that the mechanism is as follows.

[0095] In the case of the carrier having an apparent density lower than 2.5 g / cm3, although the internal porosity is low, there is a large surface irregularity, and when the carrier particles rub against or collide with each other in the developing device, the protruding portions of the carrier function as claws, and can scrape off the waste components on the surface of the coating layer.

[0096] However, if the weight of one carrier particle is small, the energy applied to the carrier particle at the time of rubbing and collision is small, and thus, the effect of scraping off the waste components by the protruding portions is low. Therefore, when the internal porosity is reduced to less than 2.0% and the weight per particle is increased, as in the carrier according to the embodiment of the present application, a large amount of energy is applied at the time of scraping, so that the protruding portions of the carrier can effectively scrape off the waste components, as a result, the accumulation of the waste components is suppressed, and the reduction of the charging ability is effectively suppressed.

[0097] The carrier according to the embodiment of the present application contains the chargeable particles in the coating layer, and the chargeable particles exert their charging ability at the time of contact with the toner particles. Since the chargeable particles are covered with, for example, resin in the coating layer, the chargeable particles must be exposed by breaking the resin covering the chargeable particles. The scraping by the protruding portions and the weight per carrier particle can expose the chargeable particles to exert the charging ability at an early stage, and continue to exert the ability for a long period.

[0098] The core material particles for the carrier according to the embodiment of the present application can be appropriately selected from the publicly known ones as the core material particles of the electrophotographic two-component carrier according to the purpose, and in particular, Mn ferrite having relatively high magnetization is preferred because it is easy to set the magnetic moment per carrier particle in a suitable range in view of the carrier-attachment resistance.

[0099] In a magnetic field of 1000 Oe equal to 79.58 kA / m, the carrier according to the embodiment of the present application preferably has a magnetization of 56 Am 2 / kg or more but less than 73 Am 2 / kg, more preferably a magnetization of 56 Am 2 / kg or more but less than 63 Am 2 / kg.

[0100] When the magnetization is 56 Am 2 / kg or more, even if the internal void ratio is reduced to increase the mass of each particle, the magnetic moment of each particle does not decrease, and carrier adhesion is difficult to occur. Furthermore, when the magnetization is 56 Am 2 / kg or more, not only is carrier adhesion difficult to occur, but also the scraping of the above-described waste components is promoted due to the strong rubbing of the carrier particles on the developer carrier, which is advantageous for maintaining the chargeability of the carrier.

[0101] When the magnetization of the carrier is less than 73 Am 2 / kg, the magnetization is not too high, and the developer whose toner concentration has been reduced after image development does not re-enter the developing area without separating from the developing roller, and therefore, the image density of the solid image in the second and subsequent revolutions of the developing roller does not decrease, and banding abnormal images are difficult to occur.

[0102] In order to have the magnetization of the carrier in the above-described range, in a magnetic field of 1000 Oe, the magnetization of the core material is preferably 66 Am 2 / kg or more but less than 75 Am 2 / kg.

[0103] The magnetization was measured using a high-sensitivity vibrating sample magnetometer for room temperature (VSM-P7, manufactured by Toei Industry Co., Ltd.), which was continuously applied with one cycle in the range of an external magnetic field of 0-1000 Oe, and the magnetization σ1000 in an external magnetic field of 1000 Oe was determined.

[0104] To adjust the resistance, the coating layer preferably contains electrically conductive particles. Conventionally, carbon black is widely used as an electrically conductive material, but when used for a long time in a developer, carbon black or a resin sheet containing carbon black can be detached from the carrier coating layer due to friction or collision between the carrier particles or between the carrier particles and the toner particles, adhere to the toner particles or remain as is and develop. When the developer is combined with toner, particularly yellow toner, white toner or transparent toner, a problem of color turbidity (color contamination) is significantly observed. Therefore, the electrically conductive particles are preferably as close to white or colorless as possible. Examples of materials having good color and electrically conductive functions include, but are not limited to, doped tin oxide doped with tungsten, indium, phosphorus or oxides of these substances, which can be used directly or provided on the surface of the base particles. As the base particles, any known material can be used, examples of which include, but are not limited to, alumina and titania.

[0105] The coating layer can also contain a resin, and other components as needed.

[0106] The resin used for the coating layer can include a silicone resin, an acrylic resin, or a combination thereof. The acrylic resin has strong adhesion and low brittleness, and thus has very excellent wear resistance, however, on the other hand, the acrylic resin has a high surface energy, and in the case of combination with a consumable toner, the charge amount is reduced due to accumulation of the consumed toner component. In this case, the problem can be solved by using a silicone resin which is less likely to consume the toner component due to low surface energy, and is difficult to accumulate the consumed component due to film wear. However, the silicone resin has low adhesion and high brittleness, and thus also has a weak point of poor wear resistance, and thus, it is important to obtain a good balance of the properties of the two resins, whereby a coating film having difficulty in accumulation of the consumed material and having wear resistance can be obtained. This is because the silicone resin has a low surface energy, and thus, it is difficult for the toner component to be consumed, and an effect of making it difficult to accumulate the consumed component for film wear can be obtained.

[0107] The silicone resin described in the present specification refers to all known silicone resins, examples of which include straight-chain silicone resins consisting of silicone-oxane bonds alone and silicone resins modified with alkyd, polyester, epoxy, acrylic, urethane, and the like. However, the silicone resin is not limited to these examples. Examples of commercially available products of the straight-chain silicone resin include KR271, KR255, and KR152 manufactured by Shin-Etsu Chemical Co., Ltd. and SR2400, SR2406, and SR2410 manufactured by Dow Corning Toray Silicone Co., Ltd. In these cases, although the silicone resin alone can be used, the silicone resin can also be used simultaneously with other components that can cause cross-linking reaction and a charge amount adjusting component, and the like. Examples of the modified silicone resin include KR206 (alkyd-modified), KR5208 (acrylic resin-modified), ES1001N (epoxy-modified), and KR305 (urethane-modified) manufactured by Shin-Etsu Chemical Co., Ltd. and SR2115 (epoxy-modified) and SR2110 (alkyd-modified) manufactured by Dow Corning Toray Silicone Co., Ltd.

[0108] Examples of the polycondensation catalyst include, but are not limited to, titanium-based catalysts, tin-based catalysts, zirconium-based catalysts, and aluminum-based catalysts. Among these catalysts, diisopropoxy bis(ethylacetoacetate titanium) is the most preferred catalyst in the titanium-based catalysts that provide excellent results according to the present application. This can be considered because the catalyst is highly effective for promoting the condensation reaction of the silanol groups and is difficult to deactivate.

[0109] The acrylic resin described in the present specification refers to all known resins containing an acrylic component, which is not particularly limited. These acrylic resins can be used alone, or in combination with at least one cross-linking component. Specific examples of the cross-linking component include, but are not limited to, amino resins and acidic catalysts. Specific examples of the amino resin include, but are not limited to, guanamine resins and melamine resins. The acidic catalyst refers to all materials having a catalytic action. Specific examples thereof include, but are not limited to, catalysts having reactive groups of a fully alkylated type, a methylol type, an imino type, a methylol / imino type.

[0110] The coating layer preferably contains a cross-linking product of an acrylic resin and an amino resin, in which case the coating layers can be prevented from fusing with each other while maintaining proper elasticity.

[0111] Examples of the amino resin include, but are not limited to, melamine resin and benzoguanamine resin, which can improve the charge-imparting ability of the resulting support. When it is desired to appropriately control the charge-imparting ability of the resulting support, the melamine resin and / or the benzoguanamine resin can be used in combination with another amino resin.

[0112] The acrylic resin which can be crosslinked with the amino resin is preferably an acrylic resin containing a hydroxyl group and / or a carboxyl group, and more preferably an acrylic resin containing a hydroxyl group. Thereby, the close contact with the core material particles and the electrically conductive particles can be improved, and the dispersion stability of the electrically conductive particles can be improved. In this case, the hydroxyl value of the acrylic resin is preferably 10 mgKOH / g or more, and more preferably 20 mgKOH / g or more.

[0113] The composition for forming the coating layer preferably contains a silane coupling agent. In this case, the electrically conductive particles can be stably dispersed.

[0114] Specific examples of the silane coupling agent include, but are not limited to, γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropylmethyldimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane hydrochloride, γ-glycidyloxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, vinyltriacetyloxy silane, γ-chloropropyltrimethoxysilane, hexamethyldisilazane, γ-anilinopropyltrimethoxysilane, vinyltrimethoxysilane, octadecyldimethyl[3-(trimethoxysilyl)propyl]ammonium chloride, γ-chloropropylmethyldimethoxysilane, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, allyltriethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, dimethyldiethoxysilane, 1,3-divinyltetramethyldisilazane, and methacryloyloxyethyldimethyl(3-trimethoxysilylpropyl)ammonium chloride. Two or more of these silanes can be used in combination.

[0115] Specific examples of commercially available products of the silane coupling agent include, but are not limited to, AY43-059, SR6020, SZ6023, SH6026, SZ6032, SZ6050, AY43-310M, SZ6030, SH6040, AY43-026, AY43-031, sh6062, Z-6911, sz6300, sz6075, sz6079, sz6083, sz6070, sz6072, Z-6721, AY43-004, Z-6187, AY43-021, AY43-043, AY43-040, AY43-047, Z-6265, AY43-204M, AY43-048, Z-6403, AY43-206M, AY43-206E, Z6341, AY43-210MC, AY43-083, AY43-101, AY43-013, AY43-158E, Z-6920, and Z-6940 (manufactured by Toray Silicon Co., Ltd.).

[0116] Preferably, the proportion of the silane coupling agent to the silicone resin is 0.1 to 10% by mass. When the proportion of the silane coupling agent is less than 0.1% by mass, the adhesion strength between the core particles / conductive particles and the silicone resin decreases, resulting in peeling of the coating layer in long-term use, and when the proportion exceeds 10% by mass, toner filming occurs in long-term use.

[0117] The volume average particle diameter of the carrier core is not particularly limited, and the volume average particle diameter is preferably 20 μm or more in order to prevent carrier attachment and carrier scattering, and the volume average particle diameter is preferably 100 μm or less in order to prevent abnormal images (such as streaks caused by carrier particles) and image quality deterioration, and in particular, a core having a volume average particle diameter of 20 to 60 μm can satisfy recent demands for higher image quality. The volume average particle diameter can be measured using, for example, a particle size distribution meter, MICROTRAC Model HRA9320-X100 (manufactured by NIKKISO CO., LTD.).

[0118] The carrier according to one embodiment of the present application can be produced by, for example, dissolving a resin or the like in a solvent to prepare a coating liquid, uniformly coating the surface of the core particles with the coating liquid using a publicly known coating method, and then drying and baking. Examples of the coating method include, but are not limited to, a dipping method, a spray coating method, and a brush coating method.

[0119] The solvent is not particularly limited and can be appropriately selected depending on the specific purpose, and specific examples include, but are not limited to, toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, cellosolve, and butyl acetate.

[0120] The baking method is not particularly limited and can be appropriately selected depending on the specific purpose. Specific examples include, but are not limited to, external heating methods and internal heating methods.

[0121] The baking appliance is not particularly limited and can be appropriately selected depending on the specific purpose. Specific examples include, but are not limited to, stationary electric furnaces, flow-type electric furnaces, rotary electric furnaces, combustion furnaces, and devices equipped with microwaves.

[0122] The average thickness of the coating layer is preferably 0.2 μm or more but 1.0 μm or less, more preferably 0.4 μm or more but 0.8 μm or less.

[0123] The average thickness of the coating layer can be measured by, for example, observing the cross section of the support using a transmission electron microscope (TEM).

[0124] The developer according to one embodiment of the present application, which contains the support according to one embodiment of the present application, can further contain a toner.

[0125] The toner can contain a binder, a colorant, a release agent, a charge control agent, an external additive, or the like, can be any one of a monochrome toner, a color toner, a white toner, a transparent toner, or a metallic luster toner, and can be produced by a conventionally known method such as a pulverization method and a polymerization method or any other method.

[0126] In a typical pulverization method, a toner material is melt-kneaded, the melt-kneaded product is cooled and pulverized into particles, the particles are classified by size, a master batch is prepared, and an external additive is added to the master batch in order to further improve transferability and durability, thereby obtaining a toner.

[0127] Specific examples of the kneader used to knead the toner material include, but are not limited to, a batch-type double roll machine; an internal mixer; a continuous twin-screw extruder such as a KTK twin-screw extruder (available from Kobe Steel, Ltd.), a TEM twin-screw kneader (available from TOSHIBA MACHINE CO., LTD.), a twin-screw extruder (available from KCK), a PCM twin-screw extruder (available from IKEGAI), and a KEX twin-screw extruder (available from Kurimoto, Ltd.); and a continuous single-screw kneader such as a co-kneader (available from BUSS).

[0128] When the cooled melt-kneaded product is pulverized, the melt-kneaded product is coarsely pulverized by means of a hammer-type pulverizer, a Rotoplex, or the like, and then the resultant is finely pulverized using a fine pulverizer utilizing jet flow or a mechanical fine pulverizer. The pulverization is preferably performed such that the average particle diameter of the particles is 3 μm to 15 μm.

[0129] Further, when the pulverized melt-kneaded product is classified, a pneumatic classifier or the like can be used. The classification is preferably performed so that the average particle diameter of the master batch is 5 μm to 20 μm.

[0130] When the external additive is added to the master batch, the external additive is crushed by mixing and stirring using a mixer or the like so as to adhere to the surface of the master batch.

[0131] Examples of the binding resin include, but are not limited to, homopolymers of styrene and substituted products of styrene, such as polystyrene, poly(p- styrene), and polyvinyltoluene; copolymers based on styrene, such as a copolymer of styrene-p-chlorostyrene, a copolymer of styrene-propylene, a copolymer of styrene-vinyltoluene, a copolymer of styrene-methyl acrylate, a copolymer of styrene-ethyl acrylate, a copolymer of styrene-methacrylic acid, a copolymer of styrene-methyl methacrylate, a copolymer of styrene-ethyl methacrylate, a copolymer of styrene-butyl methacrylate, a copolymer of styrene-α-chloromethyl methacrylate, a copolymer of styrene-acrylonitrile, a copolymer of styrene-vinyl methyl ether, a copolymer of styrene-methyl vinyl ketone, a copolymer of styrene-butadiene, a copolymer of styrene-isoprene, and a copolymer of styrene-maleate; polymethyl methacrylate; polybutyl methacrylate; polyvinyl chloride; polyvinyl acetate; polyethylene; a polyester; a polyurethane; an epoxy resin; polyvinyl butyral; polyacrylic acid; a rosin; a modified rosin; a terpene resin; a phenol resin; an aliphatic or aromatic hydrocarbon resin; and an aromatic petroleum resin. The above-listed examples can be used in combination.

[0132] The binding resin for pressure fixation is not particularly limited. Examples of the binding resin for pressure fixation include: polyolefins, such as low-molecular-weight polyethylene and low-molecular-weight polypropylene; olefin copolymers, such as a copolymer of ethylene-acrylic acid, a copolymer of ethylene-acrylate, a copolymer of styrene-methacrylic acid, a copolymer of ethylene-methacrylate, a copolymer of ethylene-chlorovinyl, a copolymer of ethylene-vinyl acetate, and an ionic bond resin; an epoxy resin; a polyester; a copolymer of styrene-butadiene; polyvinylpyrrolidone; a copolymer of methyl vinyl ether-maleic anhydride; a maleic acid-modified phenol resin; and a phenol-modified terpene resin. The above-listed examples can be used in combination.

[0133] Specific examples of colorants (i.e., pigments and dyes) include, but are not limited to, yellow pigments such as cadmium yellow, mineral fast yellow, nickel titanium yellow, naples yellow S, Hansa yellow G, Hansa yellow 10G, benzidine yellow GR, quinoline yellow lake, permanent yellow NCG, and tartrazine lake; orange pigments such as molybdate orange (molybdate orange), permanent orange GTR, pyrazolone orange, balkan orange, indanthrone brilliant orange RK, benzidine orange G, and indanthrone brilliant orange GK; red pigments such as red iron oxide, cadmium red, permanent red 4R, lithol red, pyrazolone red, watching red calcium salt, red lake D, brilliant carmine 6B, eosin lake, rhodamine lake B, alizarin lake, and brilliant carmine 3B; violet pigments such as fast violet B and methyl violet lake; blue pigments such as cobalt blue, alkali blue, victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, partially chlorinated phthalocyanine blue, fast sky blue, and indanthrone blue BC; green pigments such as chromium green, chromium oxide, pigment green B, and malachite green lake; and black pigments such as carbon black, oil furnace black, stack black, lamp black, acetylene black, azine dyes (e.g., aniline black), metal salts of azo dyes, metal oxides, and complex metal oxides; and white pigments such as titanium oxide. Two or more of these colorants can be used in combination, and the transparent toner can be free of colorants.

[0134] Specific examples of release agents include, but are not limited to, polyolefins (e.g., polyethylene, polypropylene), metal salts of fatty acids, fatty acid esters, paraffin wax, amide-based wax, polyol wax, silicone varnish, carnauba wax, and ester wax. Two or more of these materials can be used in combination.

[0135] Specific examples of the charge control agent include, but are not limited to: aniline black; azine-based dyes including an alkyl group having 2 to 16 carbon atoms; basic dyes such as C.I. Basic Yellow 2 (C.I. 41000), C.I. Basic Yellow 3, C.I. Basic Red 1 (C.I. 45160), C.I. Basic Red 9 (C.I. 42500), C.I. Basic Violet 1 (C.I. 42535), C.I. Basic Violet 3 (C.I. 42555), C.I. Basic Violet 10 (C.I. 45170), C.I. Basic Violet 14 (C.I. 42510), C.I. Basic Blue 1 (C.I. 42025), C.I. Basic Blue 3 (C.I. 51005), C.I. Basic Blue 5 (C.I. 42140), C.I. Basic Blue 7 (C.I. 42595), C.I. Basic Blue (C.I. 52015), C.I. Basic Blue 24 (C.I. 52030), C.I. Basic Blue 25 (C.I. 52025), C.I. Basic Blue 26 (C.I. 44045), C.I. Basic Green 1 (C.I. 42040), and C.I. Basic Green 4 (C.I. 42000); lake pigments of the above-listed basic dyes; quaternary ammonium salts such as C.I. Solvent Black 8 (C.I. 26150), benzoylmethylhexadecylammonium chloride, and decyltrimethylammonium chloride; alkyltin compounds such as dibutyltin compounds and dioctyltin compounds; dialkyltin borate compounds; guanidine derivatives; polyamine resins such as amino group-containing vinyl-based polymers and amino group-containing condensate-based polymers; metal complex salts of metal complexes of monoazo dyes; salicylic acid; metal (e.g., Zn, Al, Co, Cr, and Fe) complexes of dialkylsalicylic acids, naphthoic acids, and dicarboxylic acids; sulfonated copper phthalocyanine pigments; organic boron salts; fluorine-containing quaternary ammonium salts; and calixarene-based compounds. The above-listed examples can be used in combination. For colored toners other than black toners, white metal salts of salicylic acid derivatives are preferred.

[0136] Specific examples of the external additive include, but are not limited to: inorganic particles such as silica, titanium oxide, aluminum oxide, silicon carbide, silicon nitride, and boron nitride; and resin particles having an average particle diameter of 0.05 to 1 μm, such as polymethyl methacrylate particles and polystyrene particles, obtained by a soap-free emulsion polymerization method. The above-listed examples can be used in combination. Among the above-listed examples, metal oxide particles such as silica and titanium oxide, whose surfaces are hydrophobically treated, are preferred. Furthermore, toners having excellent charge stability against humidity can be obtained by using hydrophobically treated silica and hydrophobically treated titanium oxide in combination and adjusting the amount of the hydrophobically treated titanium oxide to be greater than the amount of the hydrophobically treated silica.

[0137] The electrophotographic image forming method according to the embodiment of the present application forms an image using the developer according to the embodiment of the present application, and the electrophotographic image forming apparatus according to the embodiment of the present application contains the developer according to the embodiment of the present application.

[0138] Specifically, the electrophotographic image forming method according to the embodiment of the present application includes the steps of forming an electrostatic latent image on an electrostatic latent image carrier (including the step of charging the electrostatic latent image carrier and the step of irradiating the electrostatic latent image carrier to form an electrostatic latent image thereon), developing the electrostatic latent image formed on the electrostatic latent image carrier with the developer according to the embodiment of the present application to form a toner image, transferring the toner image formed on the electrostatic latent image carrier to a recording medium, and fixing the toner image on the recording medium.

[0139] The electrophotographic image forming apparatus according to the embodiment of the present application includes an electrostatic latent image carrier, a charger configured to charge the electrostatic latent image carrier, an exposure device configured to form an electrostatic latent image on the electrostatic latent image carrier, a developing device containing the developer according to the embodiment of the present application, configured to develop the electrostatic latent image formed on the electrostatic latent image carrier with the developer to form a toner image, a transfer device configured to transfer the toner image formed on the electrostatic latent image carrier to a recording medium, and a fixing device configured to fix the toner image on the recording medium.

[0140] Figure 1 is a schematic view illustrating a process cartridge according to the embodiment of the present application. The process cartridge includes a photosensitive body 20, a proximity-type brush charger 32, a developing device 40 containing the developer according to the embodiment of the present application, and a cleaner 61 having a cleaning blade, and the process cartridge 61 is detachably mounted on an image forming apparatus main body, and the above-mentioned constituent members are integrated to constitute the process cartridge, which is detachably mounted on an image forming apparatus main body such as a copying machine or a printer.

[0141] EMBODIMENT

[0142] Hereinafter, the present application will be described in more detail with reference to Examples and Comparative Examples. However, the present application is not limited to these Examples. In the following description, unless otherwise specified, "parts" means "mass parts", and "%" means "mass %".

[0143] Preparation of toner

[0144] Synthesis Example 1 of binding resin

[0145] In a reaction vessel equipped with a cooling tube, a stirrer, and a nitrogen inlet tube, 724 parts of a bisphenol A ethylene oxide 2 mole adduct, 276 parts of isophthalic acid, and 2 parts of dibutyltin oxide were charged, and reacted at 230°C for 8 hours under normal pressure, and then reacted for 5 hours under reduced pressure of 10 to 15 mmHg, and then cooled to 160°C, and 32 parts of phthalic anhydride was added thereto, and reacted for 2 hours.

[0146] Next, it was cooled to 80°C, and reacted with 188 parts of isophorone diisocyanate in ethyl acetate for 2 hours to obtain an isocyanate-containing prepolymer (P1).

[0147] Next, 267 parts of the prepolymer (P1) and 14 parts of isophorone diamine were reacted at 50°C for 2 hours to obtain a urea-modified polyester (U1) having a weight average molecular weight of 64,000.

[0148] In the same manner as described above, 724 parts of a bisphenol A ethylene oxide 2 mole adduct and 276 parts of terephthalic acid were subjected to polycondensation at 230°C for 8 hours under normal pressure, and then reacted for 5 hours under reduced pressure of 10 to 15 mmHg to obtain an unmodified polyester (E1) having a peak molecular weight of 5,000.

[0149] 200 parts of the urea-modified polyester (U1) and 800 parts of the unmodified polyester (E1) were dissolved and mixed in 2000 parts of a mixed solvent of ethyl acetate / MEK (1 / 1) to obtain an ethyl acetate / MEK solution of the adhesive resin (B1).

[0150] A part of the adhesive resin (B1) was separated by reduced pressure drying.

[0151] Master Batch Production Example 1

[0152] - Pigment: C.I. Pigment Yellow 155: 40 parts

[0153] - Adhesive resin: Polyester Resin A: 60 parts

[0154] - Water: 30 parts

[0155] Polyester Resin A Synthesis Example

[0156] - Terephthalic acid: 60 parts

[0157] - Dodecenyl succinic anhydride: 25 parts

[0158] - Trimellitic anhydride: 15 parts

[0159] - Bisphenol A (2,2) propylene oxide: 70 parts

[0160] - Bisphenol A (2,2) ethylene oxide: 50 parts

[0161] The above composition was put in a four-necked round flask equipped with a thermometer, a stirrer, a condenser and a nitrogen gas introduction tube, the flask was placed on a mantle-type electric resistance heater, nitrogen gas was introduced through the nitrogen gas introduction tube, the flask was kept in an inert gas atmosphere, and then 0.05 g of dibutyltin oxide was added, and the temperature was kept at 200°C to carry out the reaction, whereby polyester resin A was obtained.

[0162] The above raw materials were mixed with a Henschel mixer to obtain a water-permeable mixture in pigment aggregates. This was mixed with a two-roll mill set at a roll surface temperature of 130°C for 45 minutes, and pulverized with a pulverizer to particles of about 1 mm in diameter, thereby preparing a master batch (Ml).

[0163] Toner production example A

[0164] In a beaker, 240 parts of an ethyl acetate / MEK solution of the binder resin (Bl), 20 parts of tetra-tert-pentyl titanate (melting point: 81°C, melt viscosity: 25 cps) and 8 parts of the master batch (Ml) were uniformly dissolved and dispersed with a TK-type homogenizer at 12000 rpm and 60°C, thereby preparing a toner material liquid.

[0165] In another beaker, 706 parts of ion-exchanged water, 294 parts of a 10% hydroxyapatite suspension (SUPATAITO 10, manufactured by Nippon Chemical Industrial Co., Ltd.) and 0.2 parts of sodium dodecylbenzenesulfonate were uniformly dissolved and heated to 60°C. The above prepared toner material liquid was added, and stirred with a TK-type homogenizer at 12000 rpm for 10 minutes.

[0166] The resulting mixture was transferred to a flask equipped with a stirring device and a thermometer, heated to 98°C to remove the solvent, and then subjected to filtration, washing, drying and air classification. In this way, the base toner particles A were prepared.

[0167] Next, 100 parts of the base toner particles A were mixed with 1.0 part of hydrophobic silica and 1.0 part of hydrophobic titanium oxide with a Henschel mixer, thereby preparing toner A.

[0168] The particle size of the toner was measured with a particle size analyzer COULTER COUNTER TA-II (available from Beckman Coulter, Inc. (formerly known as Coulter Electronics)) having a pore size of 100 μm, and as a result, the volume average particle size (Dv) of the toner A was found to be 6.2 μm, and the number average particle size (Dn) was found to be 5.1 μm.

[0169] Preparation of a carrier

[0170] Carrier production example 1

[0171] Core material A

[0172] Mn-Mg-Sr ferrite, internal porosity 1.9%, apparent density 2.0 g / cm 3 surface roughness Rz 2.5 μm, σ1000 63 Am 2 / kg, average particle diameter 36 μm.

[0173] Composition of resin solution 1

[0174] Acrylic resin solution (solid content concentration 20 mass %): 200 mass parts

[0175] Silicone resin solution (solid content concentration 40 mass %): 2000 mass parts

[0176] Amino silane (solid content concentration 100 mass %): 30 mass parts

[0177] Tin oxide doped with tungsten oxide (powder resistivity 40 Ω-cm): 1200 mass parts

[0178] Barium sulfate (average particle diameter 0.4 μm): 650 mass parts

[0179] Toluene: 6000 mass parts

[0180] The materials of the above resin solution 1 were subjected to dispersion treatment for 10 minutes using a homogenizer, thereby obtaining a coating layer forming liquid.

[0181] The surface of the core material A was coated with the coating layer forming liquid (resin solution 1) at a speed of 30 g / min in an atmosphere of 55°C using a spin coater (manufactured by Okada Electronic Industry Co., Ltd.), and was dried. The layer thickness of the coating layer was made to be 0.6 μm. The layer thickness was adjusted by adjusting the amount of the resin solution. After being left in an electric furnace at 150°C for 1 hour, it was subjected to firing, and then was cooled, and was pulverized using a sieve having a mesh opening of 100 μm, thereby producing the support 1.

[0182] Support production example 2

[0183] Core material B

[0184] Mn-Mg-Sr ferrite, internal porosity 1.6%, apparent density 2.3 g / cm 3 surface roughness Rz 2.0 μm, σ1000 63 Am 2 / kg, average particle diameter 36 μm.

[0185] The support 2 was produced in the same manner as in production example 1 except that the core material B was used instead of the core material.

[0186] Support production example 3

[0187] Core material C

[0188] - Mn-Mg-Sr ferrite, internal void ratio: 2.1%, apparent density: 2.2 g / cm 3 , surface roughness Rz: 1.8 μm, σ1000: 63 Am 2 / kg, average particle diameter: 36 μm.

[0189] The carrier 3 was produced in the same manner as in Production Example 1, except that the core material C was used instead of the core material.

[0190] Production Example 4 of Carrier

[0191] Core material D

[0192] - Mn-Mg-Sr ferrite, internal void ratio: 1.9%, apparent density: 1.8 g / cm 3 , surface roughness Rz: 2.8 μm, σ1000: 63 Am 2 / kg, average particle diameter: 36 μm.

[0193] The carrier 4 was produced in the same manner as in Production Example 1, except that the core material D was used instead of the core material.

[0194] Production Example 5 of Carrier

[0195] Core material E

[0196] - Mn-Mg-Sr ferrite, internal void ratio: 0.7%, apparent density: 2.5 g / cm 3 , surface roughness Rz: 1.6 μm, σ1000: 63 Am 2 / kg, average particle diameter: 36 μm.

[0197] The carrier 5 was produced in the same manner as in Production Example 1, except that the core material E was used instead of the core material.

[0198] Production Example 6 of Carrier

[0199] Core material F

[0200] - Mn-Mg-Sr ferrite, internal void ratio: 1.4%, apparent density: 2.2 g / cm 3 , surface roughness Rz: 2.4 μm, σ1000: 63 Am 2 / kg, average particle diameter: 36 μm.

[0201] Composition of Resin Solution 2

[0202] - Acrylic resin solution (solid content concentration: 20 mass %): 200 mass parts

[0203] - Silicone resin solution (solid content concentration: 40 mass %): 2000 mass parts

[0204] - aminosilane (solid content concentration: 100 mass %) : 35 mass parts

[0205] - tin oxide doped with tungsten oxide (powder resistivity: 40 Ω-cm) : 1200 mass parts

[0206] - toluene : 6000 mass parts

[0207] A carrier 6 was produced in the same manner as in Production Example 1, except that the core material F and the resin solution 2 were used instead of the core material and the resin solution, respectively.

[0208] Production Example 7

[0209] Composition of Resin Solution 3

[0210] - acrylic resin solution (solid content concentration: 20 mass %) : 200 mass parts

[0211] - silicone resin solution (solid content concentration: 40 mass %) : 2000 mass parts

[0212] - aminosilane (solid content concentration: 100 mass %) : 30 mass parts

[0213] - tin oxide doped with tungsten oxide (powder resistivity: 40 Ω-cm) : 1200 mass parts

[0214] - magnesium oxide (average particle diameter: 0.05 μm) : 650 mass parts

[0215] - toluene : 6000 mass parts

[0216] A carrier 7 was produced in the same manner as in Production Example 6, except that the resin solution 3 was used instead of the resin solution.

[0217] Production Example 8

[0218] Composition of Resin Solution 4

[0219] - acrylic resin solution (solid content concentration: 20 mass %) : 200 mass parts

[0220] - silicone resin solution (solid content concentration: 40 mass %) : 2000 mass parts

[0221] - aminosilane (solid content concentration: 100 mass %) : 30 mass parts

[0222] - tin oxide doped with tungsten oxide (powder resistivity: 40 Ω-cm) : 1200 mass parts

[0223] - magnesium hydroxide (average particle diameter: 0.1 μm) : 650 mass parts

[0224] - toluene: 6000 parts by mass

[0225] The support 8 was produced in the same manner as in Production Example 6, except that the resin liquid 4 was used instead of the resin liquid.

[0226] Production Example 9 of Support

[0227] Composition of Resin Liquid 5

[0228] - acrylic resin solution (solid content concentration: 20 mass %): 200 mass parts

[0229] - silicone resin solution (solid content concentration: 40 mass %): 2000 mass parts

[0230] - amino silane (solid content concentration: 100 mass %): 30 mass parts

[0231] - tin oxide doped with tungsten oxide (powder resistivity: 40 Ω-cm): 1200 mass parts

[0232] - hydrotalcite (average particle diameter: 0.5 μm): 650 mass parts

[0233] - toluene: 6000 mass parts

[0234] The support 9 was produced in the same manner as in Production Example 6, except that the resin liquid 5 was used instead of the resin liquid.

[0235] Production Example 10 of Support

[0236] Composition of Resin Liquid 6

[0237] - acrylic resin solution (solid content concentration: 20 mass %): 200 mass parts

[0238] - silicone resin solution (solid content concentration: 40 mass %): 2000 mass parts

[0239] - amino silane (solid content concentration: 100 mass %): 30 mass parts

[0240] - tin oxide doped with tungsten oxide (powder resistivity: 40 Ω-cm): 1200 mass parts

[0241] - alumina (average particle diameter: 0.4 μm): 650 mass parts

[0242] - toluene: 6000 mass parts

[0243] The support 10 was produced in the same manner as in Production Example 6, except that the resin liquid 6 was used instead of the resin liquid.

[0244] Production Example 11 of Support

[0245] Composition of resin solution 7

[0246] - Acrylic resin solution (solid content concentration: 20 mass %) : 200 mass parts

[0247] - Silicone resin solution (solid content concentration: 40 mass %) : 2000 mass parts

[0248] - Aminosilane (solid content concentration: 100 mass %) : 30 mass parts

[0249] - Tungsten-doped tin oxide (powder resistivity: 40 Ω-cm) : 1200 mass parts

[0250] - Barium sulfate (average particle diameter: 0.4 μm) : 150 mass parts

[0251] - Toluene : 6000 mass parts

[0252] A support 11 was produced in the same manner as in Production Example 6, except that the resin solution 7 was used instead of the resin solution.

[0253] Production Example 12 of support

[0254] Core material G

[0255] - Mn ferrite, internal void ratio: 0.5%, apparent density: 2.2 g / cm 3 , surface roughness Rz: 2.3 μm, σ1000: 70 Am 2 / kg, average particle diameter: 36 μm.

[0256] A support 12 was produced in the same manner as in Production Example 1, except that the core material G was used instead of the core material.

[0257] Production Example 13 of support

[0258] Core material H

[0259] - Mn ferrite, internal void ratio: 1.8%, apparent density: 2.3 g / cm 3 , surface roughness Rz: 1.9 μm, σ1000: 70 Am 2 / kg, average particle diameter: 36 μm.

[0260] A support 13 was produced in the same manner as in Production Example 1, except that the core material H was used instead of the core material.

[0261] Production Example 14 of support

[0262] Core material I

[0263] - Mn ferrite, internal void ratio: 1.7%, apparent density: 2.2 g / cm 3Rz = 2.1 μm, σ1000 = 70 Am 2 / kg, average particle diameter = 36 μm.

[0264] The carrier 14 was produced in the same manner as in Production Example 1, except that the core material I was used instead of the core material.

[0265] Production Example 15

[0266] Core material J

[0267] -Mn ferrite, internal void ratio = 0.4%, apparent density = 2.0 g / cm 3 , Rz = 2.9 μm, σ1000 = 70 Am 2 / kg, average particle diameter = 36 μm.

[0268] The carrier 15 was produced in the same manner as in Production Example 1, except that the core material J was used instead of the core material.

[0269] Production Example 16

[0270] Core material K

[0271] -Mn ferrite, internal void ratio = 0.3%, apparent density = 2.0 g / cm 3 , Rz = 3.1 μm, σ1000 = 70 Am 2 / kg, average particle diameter = 36 μm.

[0272] The carrier 16 was produced in the same manner as in Production Example 1, except that the core material K was used instead of the core material.

[0273] Production Example 17

[0274] Core material L

[0275] -Mn ferrite, internal void ratio = 0.5%, apparent density = 2.2 g / cm 3 , Rz = 2.3 μm, σ1000 = 65 Am 2 / kg, average particle diameter = 36 μm.

[0276] The carrier 17 was produced in the same manner as in Production Example 1, except that the core material L was used instead of the core material.

[0277] Production Example 18

[0278] Core material M

[0279] -Mn ferrite, internal void ratio = 0.5%, apparent density = 2.2 g / cm 3 , Rz = 2.3 μm, σ1000 = 67 Am 2 / kg, and the average particle diameter was 36 μm.

[0280] The carrier 18 was produced in the same manner as in Production Example 1, except that the core material M was used instead of the core material.

[0281] Production Example 19

[0282] Core material N

[0283] -Mn ferrite, internal void ratio: 0.5%, apparent density: 2.2 g / cm 3 , surface roughness Rz: 2.3 μm, σ1000: 74 Am 2 / kg, and the average particle diameter was 36 μm.

[0284] The carrier 19 was produced in the same manner as in Production Example 1, except that the core material N was used instead of the core material.

[0285] Production Example 20

[0286] Core material O

[0287] -Mn ferrite, internal void ratio: 0.5%, apparent density: 2.2 g / cm 3 , surface roughness Rz: 2.3 μm, σ1000: 76 Am 2 / kg, and the average particle diameter was 36 μm.

[0288] The carrier 20 was produced in the same manner as in Production Example 1, except that the core material O was used instead of the core material.

[0289] Production Example 21

[0290] Composition of resin solution 8

[0291] -Acrylic resin solution (solid content concentration: 20 mass %): 200 mass parts

[0292] -Silicone resin solution (solid content concentration: 40 mass %): 2000 mass parts

[0293] -Aminosilane (solid content concentration: 100 mass %): 30 mass parts

[0294] -Indium-doped tin oxide (powder resistivity: 40 Ω-cm): 1200 mass parts

[0295] -Barium sulfate (average particle diameter: 0.4 μm): 650 mass parts

[0296] -Toluene: 6000 mass parts

[0297] The carrier 21 was produced in the same manner as in Production Example 1, except that the resin solution 8 was used instead of the resin solution.

[0298] Support production example 22

[0299] Composition of resin solution 9

[0300] - Acrylic resin solution (solid content concentration: 20 mass%) : 200 mass parts

[0301] - Silicone resin solution (solid content concentration: 40 mass%) : 2000 mass parts

[0302] - Aminosilane (solid content concentration: 100 mass%) : 30 mass parts

[0303] - Tin oxide doped with phosphorus pentoxide (powder resistivity: 40 Ω-cm) : 1200 mass parts

[0304] - Barium sulfate (average particle diameter: 0.4 μm) : 650 mass parts

[0305] - Toluene : 6000 mass parts

[0306] A support 22 was produced in the same manner as in Production Example 1, except that the resin solution 9 was used instead of the resin solution.

[0307] Support production example 23

[0308] Composition of resin solution 10

[0309] - Acrylic resin solution (solid content concentration: 20 mass%) : 200 mass parts

[0310] - Silicone resin solution (solid content concentration: 40 mass%) : 2000 mass parts

[0311] - Aminosilane (solid content concentration: 100 mass%) : 30 mass parts

[0312] - Carbon (Ketjen black) : 900 mass parts

[0313] - Barium sulfate (average particle diameter: 0.4 μm) : 650 mass parts

[0314] - Toluene : 6000 mass parts

[0315] A support 23 was produced in the same manner as in Production Example 12, except that the resin solution 10 was used instead of the resin solution.

[0316] Support production example 24

[0317] Composition of resin solution 11

[0318] - Acrylic resin solution (solid content concentration: 20 mass%) : 200 mass parts

[0319] - Silica solution (solid content concentration: 40 mass %): 2000 mass parts

[0320] - Aminosilane (solid content concentration: 100 mass %): 30 mass parts

[0321] - Alumina surface-treated with tungsten-doped tin oxide (powder resistivity: 40 Ω-cm): 1400 mass parts

[0322] - Barium sulfate (average particle diameter: 0.4 μm): 650 mass parts

[0323] - Toluene: 6000 mass parts

[0324] A support 24 was produced in the same manner as in Production Example 12, except that the resin solution 11 was used instead of the resin solution.

[0325] The supports obtained in Support Production Examples 1 to 24 are shown in detail in Table 1-1 and Table 1-2.

[0326] Table 1-1

[0327]

[0328] Table 1-2

[0329]

[0330] Example

[0331] Example 1

[0332] A developer 1 was produced by stirring and mixing 7 mass parts of the toner A produced in the toner production example and 93 mass parts of the support 1 produced in the support production example 1 using a mixer for 10 minutes.

[0333] The developer was set in a commercially available digital full-color printer (IMAGIO MP C6004SP manufactured by Ricoh Company), and the initial developer was evaluated. Then, a text image with an image area ratio of 5% was output on 50,000 sheets of paper, and an image image with an image area ratio of 20% was output on 50,000 sheets of paper, and thus a total of 100,000 sheets of paper were output with images, and the developer (hereinafter referred to as "the aged developer") was evaluated.

[0334] Amount of charge reduction

[0335] The amount of charge reduction before and after the output of 100,000 sheets of images was evaluated.

[0336] First, a triboelectrically charged sample (hereinafter referred to as "initial developer") was prepared by mixing 7 mass% of toner with respect to 93 mass% of the initial carrier, and the charge amount of the sample was measured by a general blowout method (using TB-200 manufactured by Toshiba Chemical Co., Ltd.), and the measured charge amount was defined as the initial charge amount. Next, after image output, the toner was removed from the developer by the above-described blowout device, and another triboelectrically charged sample was prepared by mixing 93 mass% of the final carrier and 7 mass% of fresh toner in the same manner as described above, and the charge amount of the sample was measured, and the difference between the measured charge amount and the initial charge amount was defined as the charge reduction amount. The target amount of the charge reduction amount was less than 10 μC / g.

[0337] Ghost image

[0338] A solid image was output using the initial developer, and the difference in image density between the top end portion of the image and the portion at a distance equal to the circumferential length of the developing roller from the top end portion toward the rear was observed with the naked eye, and the degree of occurrence of the ghost image was evaluated according to the following criteria.

[0339] A+: Very good

[0340] A: Good

[0341] B: Acceptable

[0342] C: Not acceptable in actual use

[0343] White spot (carrier adhesion)

[0344] A solid image and a 2-dot line (100 lpi / inch) pattern image in the sub-scanning direction were output on A3-sized paper using the initial developer and the aged developer, and the number of white spots produced by the carrier adhered to the solid image and between the lines of the 2-dot line pattern image was observed with the naked eye, and the evaluation was performed according to the following criteria.

[0345] A+: Very good

[0346] A: Good

[0347] B: Acceptable

[0348] C: Not acceptable in actual use

[0349] Vertical streak abnormal image

[0350] The printer was tilted by 1° to the front side, and a solid image was output using the initial developer. The resulting vertical streak abnormal image was observed with the naked eye, and the evaluation was performed according to the following criteria.

[0351] A: Good

[0352] B: Acceptable

[0353] C: Not acceptable in actual use

[0354] color contamination

[0355] A solid image was output with the initial developer and the developer after 100,000 sheets of image output (i.e., the aged developer), and measured with X-RITE.

[0356] Specifically, the values (L0*, a0*, b0* and ID) of the solid image output with the initial developer were measured using X-RITE 938D50 (available from X-Rite, Inc.), the values (L1*, a1*, b1* and ID') of the solid image output after 100,000 sheets of paper on which images were output were measured, the ΔE was calculated by the following equation, and the degree of color contamination was classified based on ΔE according to the following criteria.

[0357] Color difference ΔE = {(L0*-L1*) 2 +(a0*-a1*) 2 +(b0*-b1*) 2} 1 / 2

[0358] L0*, a0* and b0*: measured values of the initial developer

[0359] L1*, a1* and b1*: measured values after 100,000 sheets of paper on which images were output

[0360] A: ΔE < 2

[0361] B: 2 < ΔE < 6

[0362] C: 6 < ΔE

[0363] The grades A and B are acceptable.

[0364] Examples 2 to 20 and Comparative Examples 1 to 4

[0365] The evaluation was performed in the same manner as Example 1 except that the respective supports 2 to 24 were used and the developers 2 to 24 were substituted for the developer.

[0366] Table 2 shows the evaluation results.

[0367] Table 2

[0368]

[0369] It is clear from the results in Table 2 that each of the examples achieved good results in evaluating the above-described properties, i.e., "amount of charge reduction", "white spot (support attachment)", "vertical streak abnormal image" and "color contamination". In contrast, each of the comparative examples could not satisfy all of these properties at the same time.

[0370] The above-described embodiments are illustrative and not restrictive. Many further modifications and variations can be possible in light of the above teachings. For example, components and / or features of different illustrative embodiments can be combined and / or substituted for one another in this disclosure without departing from the scope of the application.

[0371] This patent application is based on and claims priority to Japanese Patent Application No. 2019-207223, filed on November 15, 2019, the entire contents of which are incorporated herein by reference.

[0372] List of Reference Signs

[0373] 20 photoreceptor

[0374] 32 charger

[0375] 40 developing device

[0376] 61 cleaner

Claims

1. A carrier for electrophotographic image formation, comprising: core material particles; and a coating layer coating the core material particles, the coating layer containing chargeable particles, wherein the core material particles have a surface roughness Rz of 2.0 μm or more but less than 3.0 μm. The chargeable particles include at least one component selected from the group consisting of barium sulfate, zinc oxide, magnesium oxide, magnesium hydroxide, and hydrotalcite. The chargeable particles include barium sulfate, and the amount of barium exposed on the surface of the coating layer is 0.1 atom% or more. wherein The carrier has an internal porosity of 0.0% or more but less than 2.0%, and an apparent density of 2.0 g / cm 3 or more but less than 2.5 g / cm 3 ​ The core material particles include manganese ferrite.

2. The vector of claim 1, wherein, 6. The carrier according to any one of claims 1 to 4, 3. The vector of claim 1, wherein, The coating layer further contains inorganic particles, 4. The vector of claim 1, wherein, wherein the inorganic particles include at least one selected from the group consisting of:

5. The vector of any one of claims 1-4, wherein, The support has a magnetization of 56 Am 2 / kg or more but less than 73 Am 2 / kg in a magnetic field of 1000 Oe equal to 79.58 kA / m. at least one element-doped tin oxide particle selected from the group consisting of tungsten, indium, phosphorus, tungsten oxide, indium oxide, and phosphorus oxide; and wherein a particle containing a base particle and having the tin oxide doped on the surface of the base particle.

7. A developer for electrophotographic image formation, comprising the carrier according to any one of claims 1 to 6.

8. An electrophotographic image forming method, comprising: forming an electrostatic latent image on an electrostatic latent image carrier; developing the electrostatic latent image formed on the electrostatic latent image carrier with the developer according to claim 7 to form a toner image; transferring the toner image formed on the electrostatic latent image carrier to a recording medium; and fixing the toner image on the recording medium.

9. An electrophotographic image forming apparatus, comprising: an electrostatic latent image carrier; a charger configured to charge the electrostatic latent image carrier; an exposure device configured to form an electrostatic latent image on the electrostatic latent image carrier; a developing device containing the developer according to claim 7, the developing device being configured to develop the electrostatic latent image formed on the electrostatic latent image carrier with the developer to form a toner image; a transfer device configured to transfer the toner image formed on the electrostatic latent image carrier to a recording medium; and a fixing device configured to fix the toner image on the recording medium.

10. A process cartridge detachably mounted on an image forming apparatus, comprising: an electrostatic latent image carrier; a charger configured to charge the electrostatic latent image carrier; a developing device containing the developer according to claim 7, the developing device being configured to develop the electrostatic latent image formed on the electrostatic latent image carrier with the developer to form a toner image; and a cleaner configured to clean the electrostatic latent image carrier. ​ ​ ​ ​ ​ ​

Images