JP2005091437A - Magnetic toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic toner which has environmentally hardly affected and stable electrostatic charge performance, has high image density in spite of long-term use, is suppressed in the occurrence of fogging and has excellent image reproducibility. <P>SOLUTION: The toner containing at least a binder resin and iron oxide is characterized by that (I), when the diameter of the equivalent projected area of the toner is defined as C, the toner satisfying the structure of the iron oxide existing at ≥70number% down to a depth of 0.2 times the diameter of the equivalent projected area C from the surface of the toner is ≥40number% in the cross section observation of the toner using a transmission electron microscope (TEM) and (II) the iron oxide is treated with a low softening point material. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a toner used for developing an electrostatic image formed in an image forming method such as an electrophotographic method, an electrostatic recording method, a magnetic recording method, and a toner jet recording method.

  Conventionally, a number of methods are known as electrophotographic methods, but in general, a photoconductive substance is used, and electrostatic charge image carriers (hereinafter also referred to as “photoconductors”) are electrostatically charged by various means. A latent image is formed, and then the latent image is developed with toner to form a visible image. If necessary, the toner image is transferred to a recording medium such as paper, and then the toner image is formed on the recording medium by heat or pressure. Is fixed to obtain a copy.

  Among these, a jumping development method using magnetic toner (a thin coating of insulating magnetic toner is applied on a developer carrying member, this is triboelectrically charged, and then this is brought very close to an electrostatic latent image under the action of a magnetic field. In addition, the method of developing without facing and developing is widely used as a method for obtaining a high-definition image with less fog.

  However, the developing method using magnetic toner has unstable factors related to the magnetic toner to be used. This is because a considerable amount of fine magnetic powder is mixed and dispersed in the toner, and a part of the magnetic material is exposed on the surface of the toner particles, so that the fluidity and triboelectric chargeability of the toner are lowered. That's it. Therefore, in the long-term use, the developer is deteriorated such as a decrease in image density due to peeling of the magnetic material due to rubbing between the toners or the regulating member, and generation of unevenness of density called sleeve ghost.

  With respect to the deterioration of image characteristics due to the exposure of such a magnetic material, many proposals have been made from the viewpoint of the toner structure.

  For example, there is a report on a special toner in which magnetic particles are contained only in a specific portion inside the particles. Specifically, it is a pressure fixing toner manufactured by a 2-3 stage process in which a magnetic material is dry-attached after manufacturing core particles and then a shell layer is formed, and the magnetic material exists only in the toner intermediate layer. (See Patent Documents 1 and 2). There is also a report on a toner having a structure in which a resin layer having no magnetic particles is formed in the vicinity of the toner particle surface with a certain thickness or more (see Reference 3). However, in such a toner, when the average particle size is as small as 10 μm or less, for example, the volume in which the magnetic particles can be present is small, so that it is difficult to enclose a sufficient amount of the magnetic particles. That is, the ratio of the surface resin layer in which no magnetic particles are present differs between toner particles having a large particle size and toner particles having a small particle size in the toner particle size distribution. In contrast, developability and transferability also vary depending on the particle size of the developer. That is, selective developability depending on the particle size is likely to be seen. Therefore, when printing is performed for a long time with a magnetic developer having a non-uniform particle size, particles that contain a large amount of magnetic material and are difficult to develop, that is, developer particles with a large particle size are likely to remain, and the image density and image quality are reduced. It also leads to deterioration of fixability.

  On the other hand, printers and copiers have recently shifted from analog to digital, and there is a strong demand for higher reproducibility of latent images and higher resolution, while at the same time improving print speed and reducing power consumption.

  For example, paying attention to the printer, the ratio of power consumption in the fixing process to the total power consumption is considerably large, and the power consumption increases as the fixing temperature increases. Further, when the fixing temperature becomes high, problems such as curling of the printout paper also occur, and there is a great demand for lowering the fixing temperature.

  On the other hand, many studies have conventionally been made on the low-temperature fixing of toner. For example, many proposals have been made regarding a low softening point material added to toner, and the dispersibility of the magnetic powder in the toner can be achieved by using a special technique of treating the surface of the magnetic powder with the low softening point material. Have been reported to improve the fixing performance and offset resistance (see Patent Documents 4 to 6).

  However, even if such a magnetic powder is used, there is still room for improvement in achieving both low-temperature fixability and offset resistance of the toner, and improvement in fixability has been insufficient. In particular, when the process speed is high, the amount of heat received by the toner is limited because the time during which the toner contacts the fixing device becomes very short. Therefore, the toner used in the high-speed printer is required to be fixed at a lower temperature.

JP 60-3647 A JP 63-89867 A JP-A-7-209904 JP-A-9-319137 JP-A-1-259369 JP-A-1-259372

  An object of the present invention is to provide a magnetic toner that solves the above problems.

  An object of the present invention is to provide a magnetic toner that is less influenced by the environment, has a stable charging performance, has a high image density even when used for a long time, suppresses the occurrence of fogging, and has excellent image reproducibility. It is in.

  An object of the present invention is to provide a magnetic toner capable of forming a stable electrostatic latent image even in a low-temperature and low-humidity environment and having less image defects such as fog due to a decrease in chargeability during durability.

  It is a further object of the present invention to provide a magnetic toner and a method for producing the toner, which can obtain a sufficient image density even in a minute isolated dot, and can achieve high image quality and low consumption.

  An object of the present invention is to provide a magnetic toner that is excellent in low-temperature fixability and has good fixability in a wide fixing temperature range even at a high process speed.

The present invention is a toner containing at least a binder resin and iron oxide,
I) Assuming that the projected area equivalent diameter of the toner is C, in the cross-sectional observation of the toner using a transmission electron microscope (TEM), the iron oxide has a depth of 0.2 times the projected area equivalent diameter C from the toner surface. In addition, the toner satisfying the structure of 70% by number or more is 40% by number or more,
II) The present invention relates to a magnetic toner characterized in that the iron oxide has been treated with a low softening point substance.

  The magnetic toner of the present invention is excellent in low-temperature fixability and has a wide fixing temperature range even at a high process speed.

  Further, by using the magnetic toner of the present invention, an image having a high image density, high quality and excellent resolution can be obtained even in long-term use in a low temperature and low humidity environment.

  As a result of intensive investigations on the uniform and stable charging of conventional magnetic toners, particularly in a low-temperature and low-humidity environment, and the compatibility between low-temperature fixability and offset resistance, the present inventors have found that a low softening point material is uniform. In addition to satisfying image characteristics such as developability and transferability, the spherical toner has a structure in which a certain amount or more of the surface-treated iron oxide is concentrated in the vicinity of the surface. It was found that the toner consumption can be reduced due to the coloring power, and that the toner has a wide fixing temperature range, and the present invention has been achieved.

  Specifically, 40% by number or more, preferably 60% by number or more of the toner satisfying the structure in which the magnetic material is present at 70% by number or more from the toner surface to a depth 0.2 times the projected area equivalent diameter C. By providing such a substantially magnetic capsule intermediate layer, the rigidity of the toner is remarkably improved, and the embedding of the external additive is reduced, resulting in excellent durability stability. In addition, the presence of a low-resistance magnetic substance in the vicinity of the toner surface suppresses charge-up particularly in a low-temperature and low-humidity environment, and lowers the durable density and fog. Furthermore, since the magnetic capsule intermediate layer of the present invention has a locally high magnetic density along the outer periphery of the toner when melted, the toner coloring power is also improved.

  If the toner having the above-mentioned mag intermediate layer is less than 40% by number, the capsule structure of the magnetic material is not sufficient, and therefore the influence of the dispersion of the magnetic material and the particle size dependency is likely to occur. It becomes difficult to obtain the effects of the present invention. Specifically, when a large amount of wax or low molecular weight / low Tg resin is encapsulated, the deterioration of the external additive of some toners progresses, and the image density is likely to decrease due to durability, and high temperature offset is likely to occur. It tends to occur.

  On the other hand, the magnetic capsule intermediate layer is disadvantageous in terms of toner deformation. Due to its rigidity, a large amount of wax, low molecular weight / low Tg resin, etc. can be encapsulated in the inner layer, but conversely, it seems to tend to inhibit the exudation of wax. In the first place, since a large amount of magnetic powder is mixed and dispersed inside the magnetic toner, the magnetic powder having a large heat capacity with respect to the resin absorbs a part of the heat received from the fixing device, and from the fixing device. It has been considered that this heat is not used effectively for plasticity / deformation of binder resin and melting of low softening point materials.

  Accordingly, as a result of intensive studies by the present inventors, by using iron oxide treated with a low softening point substance, the low softening point substance melts and oozes out before the magnetic powder absorbs the amount of heat received during fixing. As a result, it has been found that the fixability is greatly improved. Furthermore, in the present invention, the processed iron oxide is present in the vicinity of the toner surface, so that a certain amount or more of the low softening point substance is necessarily present in the vicinity of the surface. As a result, the melting and leaching speed of the low softening point material with respect to the heat from the fixing device is increased, and it is possible to secure a sufficient low temperature fixing property and a fixing area even in a high speed printer.

  In the toner of the present invention, the ratio (B / A) of the abundance (B) of the iron element to the abundance (A) of the carbon element present on the toner surface measured by X-ray photoelectron spectroscopy is less than 0.001. Preferably there is. B / A of less than 0.001 means that iron oxide is hardly exposed on the surface of the toner particles. When such a developer is used, there is substantially no influence of moisture absorption of the magnetic material. Therefore, it is excellent in the environmental stability of charging, and in the image forming method in which the toner is pressed against the surface of the electrostatic image carrier by a charging member or a transfer member, the surface of the electrostatic image carrier is hardly scraped. In addition, it is possible to remarkably reduce the abrasion of the electrostatic charge image carrier and the toner fusion over a long period of time. Furthermore, since the surface of the low softening point material treated with iron oxide is hardly exposed, the toner carrier and the electrostatic charge image carrier are not contaminated by the low softening point material and image defects are not caused. On the other hand, when B / A is 0.001 or more, moisture density of the magnetic material tends to cause a decrease in image density due to fogging or durability particularly in a high temperature and high humidity environment. Further, the electrostatic charge image carrier is easily scraped by the exposed magnetic body.

  Further, in the toner of the present invention, when the minimum value of the distance between the iron oxide and the toner surface in the cross-sectional observation of the toner is D, the toner satisfying the relationship of D / C ≦ 0.02 is 50% by number or more. Is preferred. If the number of toners satisfying the relationship of D / C ≦ 0.02 is less than 50% by number, in the majority of toners, there will be no magnetic particles at least outside the boundary line of D / C = 0.02. . Therefore, the surface of the toner particles has a high resistance, and the charging characteristics of the resin are easily reflected directly, so that fogging and charge-up particularly easily occur in a low temperature and low humidity environment. Further, when the number of toners satisfying the relationship of D / C ≦ 0.02 is less than 50% by number, a low softening point substance is present at least outside the boundary line of D / C = 0.02 in the majority of toners. Will not. For this reason, it takes time to transfer heat from the fixing device to the low softening point substance, and it becomes difficult to obtain sufficient low-temperature fixability in a high-speed printer.

  The treatment with the low softening point substance of iron oxide in the toner of the present invention will be described.

  A known wax can be used as the low softening point material for treating the surface of iron oxide. For example, paraffin wax, microcrystalline wax, petroleum wax such as petrolactam and derivatives thereof, montan wax and derivatives thereof, hydrocarbon wax and derivatives thereof by Fischer-Tropsch method, polyolefin wax and derivatives thereof represented by polyethylene, carnauba wax Natural waxes such as candelilla wax and derivatives thereof. Derivatives here include oxides, block copolymers with vinyl monomers, and graft modified products. It is also possible to control the state of dispersion of iron oxide in the toner by adjusting the acid value and the degree of modification of the wax. Furthermore, higher aliphatic alcohols, higher fatty acids or compounds thereof, acid amide waxes, ester waxes, ketones, hydrogenated castor oil and derivatives thereof, plant-based waxes, and animal waxes can also be used.

  These low softening point materials preferably have an endothermic peak top in the region of 80 ° C. to 150 ° C. in DSC measurement. By having a peak top in the above temperature range, it is possible to effectively exhibit releasability while greatly contributing to low temperature fixability. When the peak top is less than 80 ° C., the low softening point material tends to melt due to heat applied during toner production, and the effect of the surface treatment becomes small. On the other hand, when the peak top exceeds 150 ° C., although the hot offset resistance effect is large, the fixing temperature becomes high. Moreover, since the low softening point substance itself becomes hard, it is difficult to maintain the uniformity of the treatment for the magnetic material, which is not preferable.

  The low softening point material is preferably treated by 0.3 to 15 parts by mass with respect to 100 parts by mass of iron oxide. When the processing amount is less than 0.3 part by mass, the amount of wax present near the toner surface and exuding instantaneously at the time of fixing is small, so that a sufficient fixing effect cannot be obtained. Furthermore, it becomes difficult to uniformly treat the magnetic surface. On the other hand, when the processing amount exceeds 15 parts by mass, the endothermic amount of the low softening point substance is too large, and conversely, low-temperature fixability is inhibited.

  As an apparatus for processing the low softening point material on the surface of the magnetic powder, an apparatus capable of applying a shearing force is preferable, and in particular, an apparatus capable of simultaneously performing shearing, spatula and compression, such as a wheel-type kneader, A ball-type kneader and a roll-type kneader can be preferably used. Among these, the use of a wheel-type kneader is particularly preferable from the viewpoint of uniform treatment. When a wheel-type kneader is used, it becomes possible to rub, adhere and stretch the low softening point material on the surface of the magnetic powder, and to uniformly cover the surface of the magnetic powder with the low softening point material.

  Specific examples of the wheel-type kneader include edge runners, multi-mals, stotz mills, wet pan mills, conner mills, ring mullers, and the like, preferably edge runners, multi-mals, stotz mills, wet pan mills, ring mullers, and more. An edge runner is preferable. Specific examples of the ball kneader include a vibration mill. Specific examples of the roll-type kneader include an extruder.

  The line load is 19.6 to 1960 N / cm (2 to 200 kg / cm), preferably 98 to 1470 N / cm (10 to 150 kg / cm) so that the low softening point material can be uniformly treated / coated on the surface of the magnetic powder. ), More preferably 147 to 980 N / cm (15 to 100 kg / cm), and the processing time may be appropriately adjusted within the range of 5 to 180 minutes, preferably 30 to 150 minutes. In addition, what is necessary is just to adjust process conditions suitably in the range of stirring speed 2-2000rpm, Preferably 5-1000rpm, More preferably, it is 10-800rpm.

  The magnetic powder used in the toner of the present invention is preferably further treated with a low softening point material after surface treatment with a coupling agent.

  As described so far, in the present invention, it is essential to treat the surface of the magnetic powder with a low softening point substance. However, while the magnetic powder is an inorganic substance, the low softening point substance is an organic compound. For this reason, it is difficult to uniformly cover the surface of the magnetic powder with the low softening point substance even if the above processing equipment is used. Therefore, by treating the surface of the magnetic powder with a coupling agent (by covering the surface of the magnetic powder with an organosiloxane compound or polysiloxane compound), it is possible to uniformly treat the low softening point substance on the medium. It becomes possible. For this reason, if the surface of the magnetic powder is not treated with the coupling agent, the uniformity of the treatment with the low softening point substance is inferior, and the low-temperature fixability is inferior.

  Here, there are two methods of treating the surface of the magnetic powder with a coupling agent: dry treatment and wet treatment. In the present invention, either method may be used, and in the case of dry processing, the processing can be performed with the same apparatus as the processing apparatus suitable for processing the low softening point material.

  When wet processing is performed, it is preferable to perform surface treatment while hydrolyzing the coupling agent in an aqueous medium in a state where iron oxide is dispersed to have a primary particle size, and after washing the magnetic material produced in an aqueous solution It is more preferable to perform the hydrophobic treatment without drying.

Examples of the coupling agent that can be used for the hydrophobization treatment of iron oxide include a silane coupling agent and a titanium coupling agent. More preferably used is a silane coupling agent having the general formula RmSiYn
[Wherein, R represents an alkoxy group, m represents an integer of 1 to 3, Y represents a hydrocarbon group such as an alkyl group, a vinyl group, a glycidoxy group, or a methacryl group, and n represents an integer of 1 to 3. Show. ]
It is shown by. For example, vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, methyltrimethoxysilane, methyltriethoxysilane, isobutyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethyl Mention may be made of methoxysilane, hydroxypropyltrimethoxysilane, phenyltrimethoxysilane, n-hexadecyltrimethoxysilane and n-octadecyltrimethoxysilane.

In particular, the formula C _p H _{2p + 1} —Si— (OC _q H _{2q + 1} ) ₃
[Wherein p represents an integer of 2 to 20, and q represents an integer of 1 to 3]
It is preferable to hydrophobize iron oxide using an alkyltrialkoxysilane coupling agent represented by

  When p in the above formula is smaller than 2, the hydrophobic treatment is easy, but it is difficult to impart sufficient hydrophobicity. When p is larger than 20, the hydrophobicity is sufficient, but iron oxide The coalescence of the particles increases and it becomes difficult to sufficiently disperse the iron oxide particles in the toner.

  On the other hand, when q is larger than 3, the reactivity of the silane coupling agent is lowered and the hydrophobicity is not sufficiently performed.

  In particular, p in the formula represents an integer of 2 to 20 (more preferably an integer of 3 to 15), and q represents an integer of 1 to 3 (more preferably an integer of 1 or 2). A coupling agent should be used.

  The treatment amount is 0.05 to 20 parts by mass, preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of iron oxide.

  In order to treat the surface of the magnetic powder with a coupling agent in an aqueous medium, a method of stirring an appropriate amount of the magnetic powder and the coupling agent in the aqueous medium can be mentioned.

  An aqueous medium is a medium containing water as a main component. Specific examples of the aqueous medium include water itself, water added with a small amount of a surfactant, water added with a pH adjusting agent, and water added with an organic solvent. As the surfactant, a nonionic surfactant such as polyvinyl alcohol is preferable. The surfactant is preferably added in an amount of 0.1 to 5% by mass with respect to water. Examples of the pH adjuster include inorganic acids such as hydrochloric acid.

  Stirring is sufficiently performed, for example, with a mixer having a stirring blade (specifically, a high shear force mixing device such as an attritor or a TK homomixer) so that the iron oxide fine particles become primary particles in the aqueous medium. Is good.

  The iron oxide used in the toner of the present invention is preferably used in an amount of 10 to 200 parts by weight, more preferably 20 to 180 parts by weight, based on 100 parts by weight of the binder resin. When the blending amount of iron oxide is less than 10 parts by mass, the coloring power of the developer is poor, and it is difficult to suppress fogging. On the other hand, when it exceeds 200 parts by mass, the coercive force due to the magnetic force on the developer carrying member is increased and developability is increased. Not only is it difficult to uniformly disperse iron oxide in individual toner particles, but also the fixability is reduced.

  In the hydrophobic magnetic body of the present invention, it is difficult to control the magnetic body structure inside the toner. To produce the magnetic body distribution structure of the present invention using only the magnetic body of the present invention, the core particles are designed, Thereafter, a multi-step process such as adding a magnetic substance is required.

  Therefore, the toner of the present invention preferably contains a polar compound having a saponification value of 20 to 200. By adding the above polar compound in a direct polymerization system in an aqueous medium, it becomes easy to segregate the magnetic substance uniformly dispersed inside in the vicinity of the surface.

  The polar compound having a saponification value of 20 to 200 in the present invention is a resin having a carboxylic acid derivative group such as acrylic acid, methacrylic acid or abietic acid, or a sulfur acid group such as sulfonic acid or sulfuric acid group, or a modified product thereof. Any monomer component can be used, and specific monomer components include methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, n-propyl acrylate, n-octyl acrylate, dodecyl acrylate, acrylic 2-ethylhexyl acid, stearyl acrylate, 2-chloroethyl acrylate, acrylic esters such as phenyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-propyl methacrylate, methacryl Acid n-octyl, methacrylate methacrylate Methacrylic acid esters such as 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, maleic anhydride such as maleic anhydride and maleic acid half ester, sulfonic acid, etc. Examples include sulfur acid groups and abietic acid.

  Among these compounds, a resin having a maleic acid component is preferable in that it can exhibit an effect even in a very small amount. From the viewpoint of excellent compatibility with the binder resin without impairing the chargeability, the following general formula ( The maleic anhydride copolymer represented by 1) and / or (2) or a ring-opening compound thereof is particularly preferred, and the effects of the present invention are further exhibited.

（各式中、Ａはアルキル又はアルキレン基を示し、Ｒは水素原子または炭素数１乃至２０のアルキル基を示す。ｎは１〜２０の整数、ｘ、ｙ、ｚはそれぞれ各成分の共重合比を示す。）

(In each formula, A represents an alkyl or alkylene group, R represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, n represents an integer of 1 to 20, and x, y, and z each represent a copolymer of each component. Indicates the ratio.)

  The amount of the polar compound added is preferably 0.001 to 10 parts by mass of the polar substance with respect to the binder resin component in the toner, and less than 0.001 parts by mass of the present invention. If the effect is not exhibited and the amount exceeds 10 parts by mass, the absolute value of the charge amount is likely to decrease due to charge leakage, and fog and durability image density are likely to decrease.

  Next, the circularity of the toner will be described. In order to reduce the toner adhesion to the non-image area on the electrostatic image bearing member and the amount of residual toner, it is necessary that the chargeability of the toner particles is sufficient and uniform. Furthermore, when using a toner having a small particle diameter from the viewpoint of improving the image quality, the adhesion force of the toner particles increases, so the shape of the toner particles has a great influence on the toner adhesion to the non-image area on the electrostatic charge image carrier. Effect. In other words, the closer the toner particles are to a spherical shape and the more uniform the shape, the smaller the adhesion area of the particles, the less toner adhesion to the non-image area on the electrostatic image bearing member and the residual toner transfer amount, high image quality and durability Stability is achieved.

  The toner particles according to the present invention are sufficiently charged, and as described above, the adhesion of the toner particles is reduced, so that the transfer efficiency of the toner from the electrostatic charge image carrier to the transfer material such as paper is also large. Improved. This can be said to be an important toner performance for achieving high resolution as well as reproducibility of a minute dot image.

  Further, when the toner particles are nearly spherical and uniform in shape, the contact area between the toner and the fixing device becomes uniform, so that the low softening point processed by the magnetic material existing in the vicinity of the toner particle surface of the present invention. Substances can be leached stably. For this reason, it is possible to exhibit a stable fixing property even at a high process speed.

  Therefore, in the toner of the present invention, it is preferable that the average circularity of the toner is 0.970 or more, whereby high image quality, high stability, and low-temperature fixability are achieved.

  In the toner of the present invention, the weight average particle diameter is preferably 2 to 10 μm.

  When the weight average particle size of the toner exceeds 10 μm, the reproducibility of the fine dot image is lowered, and the toner configuration of the present invention is more susceptible to the variation in the particle size in the durability. The charging stability of the toner under the environment cannot be sufficiently exhibited. On the other hand, when the weight average particle size of the toner is smaller than 2 μm, even if the special structure of the present invention is used, the external additive is likely to be deteriorated due to a decrease in fluidity. Such problems are likely to occur.

  That is, in the toner of the present invention, a remarkable effect on the image such as improvement in charging stability and fluidity appears on the image when the weight average particle diameter is 2 to 10 μm (more preferably 3 to 10 μm). Furthermore, 3.5 to 8.0 μm is preferable from the viewpoint of higher image quality.

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

  Although the toner of the present invention can be produced by a pulverization method, the pulverization method requires a multi-step process in order to obtain the magnetic structure of the present invention. It is disadvantageous.

  On the other hand, in a toner production method (hereinafter referred to as a polymerization method) obtained by directly polymerizing a monomer system in an aqueous medium, it is locally between polar and nonpolar components from the viewpoint of affinity with the aqueous medium. Since the presence / separation is likely to occur, the magnetic structure of the present invention can be obtained in one step, which is preferable. In particular, in the present invention, the use of a trace amount of the polar compound of the present invention can improve the stability of droplets during polymerization, and the particle size distribution becomes sharp, which is further preferable in terms of yield.

  The following are mentioned as a polymerizable monomer which comprises the polymerizable monomer type | system | group used for this invention.

  Examples of the polymerizable monomer include styrene monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, and p-ethylstyrene; methyl acrylate, ethyl acrylate, Acrylic esters such as n-butyl acrylate, isobutyl acrylate, n-propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate Class: Methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenolic methacrylate , Dimethylaminoethyl methacrylate, such as methacrylic acid esters of diethylaminoethyl methacrylate; acrylonitrile, methacrylonitrile, acrylamide.

  These monomers can be used alone or in combination. Among the above-mentioned monomers, styrene or a styrene derivative is preferably used alone or mixed with other monomers from the viewpoint of the developing characteristics and durability of the toner.

  As described above, the toner of the present invention has a low softening point substance against the heat received during fixing because the iron oxide surface-treated with the low softening point substance is localized near the toner particle surface. Since it melts and exudes quickly, it has excellent fixability, but it is preferable to contain 1 to 50% by weight of a release agent with respect to the binder resin. By including a release agent in the inner layer of the magnetic capsule intermediate layer, the fixability is further improved. If the content of the release agent is less than 1% by mass, the effect of suppressing low temperature offset is small, and if it exceeds 50% by mass, the long-term storage stability is lowered and the dispersibility of other toner materials is deteriorated. It leads to deterioration of fluidity and image characteristics.

  As the release agent that can be used in the toner of the present invention, the above-mentioned types that are used as a low softening point material for treating the surface of iron oxide can be used.

  Among them, in DSC measurement, those showing a peak top of the endothermic peak in the region of 30 to 100 ° C. are preferable, and those showing the endotherm in the region of 35 to 90 ° C. are more preferable. If the endotherm is present in a region of less than 30 ° C. in DSC measurement, the wax component oozes out even at room temperature, resulting in poor storage stability. On the other hand, if the endotherm exceeds 100 ° C., the fixing temperature increases and low temperature offset tends to occur, which is not preferable. Further, when the toner is obtained directly by polymerization in an aqueous medium, if the temperature in the endothermic region is high, it is not preferable because a problem such as precipitation of a wax component during granulation occurs when a large amount is added.

  Furthermore, the release agent preferably has a half-value width of an endothermic peak in DSC measurement of 10 ° C. or more. By having a wide range of endothermic components from low temperature to high temperature, releasability can be effectively expressed while greatly contributing to low-temperature fixing.

  The maximum endothermic peak temperature of the wax component is measured according to “ASTM D 3418-8”. For the measurement, for example, DSC-7 manufactured by PerkinElmer is used. The temperature correction of the device detection unit uses the melting points of indium and zinc, and the correction of heat uses the heat of fusion of indium. An aluminum pan is used as a measurement sample, an empty pan is set as a control, and measurement is performed at a heating rate of 10 ° C./min.

  In the present invention, a resin that is not included in the saponification value of the polar compound of the present invention may be polymerized by adding a resin to the monomer system. For example, hydrophilic functional groups such as amino groups, carboxylic acid groups, hydroxyl groups, sulfonic acid groups, glycidyl groups, and nitrile groups cannot be used because monomers are water-soluble and dissolve in aqueous suspension to cause emulsion polymerization. When it is desired to introduce the monomer component contained in the toner, it may be in the form of a copolymer such as a random copolymer of these and a vinyl compound such as styrene or ethylene, a block copolymer, or a graft copolymer, or It can be used in the form of a polycondensate such as polyester or polyamide, or a polyaddition polymer such as polyether or polyimine. When such a polymer containing a polar functional group is allowed to coexist in the toner, the above-mentioned wax component is phase-separated and the encapsulation becomes stronger, and a toner having good offset resistance, blocking resistance, and low-temperature fixability can be obtained. Can be obtained. As the usage-amount, 1-20 mass parts is preferable with respect to 100 mass parts of polymerizable monomers. If the amount used is less than 1 part by mass, the effect of addition is small, whereas if it is used in excess of 20 parts by mass, it becomes difficult to design various physical properties of the polymerized toner. Moreover, the average molecular weight of the high molecular polymer containing these polar functional groups is preferably 3000 or more. When the molecular weight is less than 3000, particularly 2000 or less, the present polymer is likely to concentrate near the surface, which is unfavorable because it tends to adversely affect developability, blocking resistance and the like. In addition, if a polymer having a molecular weight different from the molecular weight range of the toner obtained by polymerizing the monomer is dissolved in the monomer and polymerized, a toner having a wide molecular weight distribution and high offset resistance can be obtained. it can.

  The toner of the present invention may contain a charge control agent in order to stabilize the charge characteristics. As the charge control agent, known ones can be used, but a charge control agent that has a high charging speed and can stably maintain a constant charge amount is particularly preferable.

  Further, when the toner is produced using a direct polymerization method, a charge control agent having a low polymerization inhibitory property and substantially free from a solubilized product in an aqueous dispersion medium is particularly preferable. Specific compounds include, as negative charge control agents, metal compounds of aromatic carboxylic acids such as salicylic acid, alkylsalicylic acid, dialkylsalicylic acid, naphthoic acid, dicarboxylic acid, metal salts or metal complexes of azo dyes or azo pigments, sulfones Examples thereof include a polymer compound having an acid or carboxylic acid group in the side chain, a boron compound, a urea compound, a silicon compound, and a calixarene. Examples of the positive charge control agent include a quaternary ammonium salt, a polymer compound having the quaternary ammonium salt in the side chain, a guanidine compound, a nigrosine compound, and an imidazole compound. These charge control agents are preferably used in an amount of 0.5 to 10 parts by mass with respect to 100 parts by mass of the polymerizable monomer. However, the developer involved in the image forming method of the present invention does not require the addition of a charge control agent, and the toner in the toner is positively utilized by frictional charging of the developer with the layer pressure regulating member or the developer carrier. It is not always necessary to include a charge control agent.

The iron oxide used as the magnetic material in the toner of the present invention may contain elements such as phosphorus, cobalt, nickel, copper, magnesium, manganese, aluminum, and silicon, and is mainly composed of iron trioxide and γ-iron oxide. These are used as components, and these may be used alone or in combination of two or more. These iron oxides preferably have a BET specific surface area by a nitrogen adsorption method of ² to 30 m ² / g, particularly 3 to 28 m ² / g, and a Mohs hardness of 5 to 7.

  The shape of iron oxide includes octahedrons, hexahedrons, spheres, needles, scales, etc., but those with low anisotropy such as octahedrons, hexahedrons, spheres, and irregular shapes increase the image density. Preferred above. Such a shape can be confirmed by SEM or the like. As the particle size of iron oxide, the volume average particle size is 0.1 to 0.3 μm and 0.03 to 0.1 μm in the measurement of particle size targeting particles having a particle size of 0.03 μm or more. The number of particles is preferably 40% by number or less.

  When an image is obtained from a magnetic toner using iron oxide having an average particle size of less than 0.1 μm, the color of the image shifts to red, and the blackness of the image is insufficient, or the halftone image is more reddish. Generally, it is not preferable, such as a strong tendency to feel strongly. Further, since the surface area of iron oxide is increased, dispersibility is lowered, energy required for production is increased, and it is not efficient. Further, the effect of iron oxide as a colorant is weakened, and the image density may be insufficient, which is not preferable.

  On the other hand, if the average particle size of iron oxide exceeds 0.3 μm, the mass per particle increases, so the probability of exposure to the toner surface increases due to the difference in specific gravity with the binder during production, or the wear of the production equipment This is not preferable because the possibility that it becomes remarkable will increase or the sedimentation stability of the dispersion will decrease.

  In addition, when the number of particles of 0.1 μm or less of the iron oxide in the toner exceeds 40% by number, the surface area of the iron oxide is increased, the dispersibility is lowered, and agglomerates are easily formed in the toner. In order to increase the possibility of impairing the chargeability or reducing the coloring power, the number is preferably 40% by number or less. Furthermore, when it is 30% by number or less, the tendency becomes smaller, which is more preferable.

  It should be noted that iron oxide of less than 0.03 μm has a low probability of appearing on the surface of the toner particles because the stress applied during toner production is small due to the small particle diameter. Furthermore, even if it is exposed to the particle surface, it hardly acts as a leak site and is not substantially a problem. Therefore, in the present invention, attention is paid to particles of 0.03 to 0.1 μm, and the number% is defined.

  Further, if the number of particles of 0.3 μm or more in iron oxide exceeds 10% by number, the coloring power tends to decrease and the image density tends to decrease. It is not preferable that the toner particles exist in the vicinity of the surface of the toner particles and that a uniform number is included in each toner particle. More preferably, it is 5% or less.

  In the present invention, it is preferable to use a product in which iron oxide production conditions are set or the particle size distribution is adjusted in advance such as pulverization and classification so as to satisfy the conditions of the particle size distribution described above. As the classification method, for example, a method using sedimentation separation such as centrifugal separation or thickener, or a wet classification device using a cyclone is suitable.

  The volume average particle size and particle size distribution of iron oxide are determined by the following measurement method.

  With the particles sufficiently dispersed, the projection area of each of the 100 iron oxide particles in the field of view was measured with a transmission electron microscope (TEM) at a magnification of 30,000 times, and each of the measured particles was measured. The equivalent diameter of a circle equal to the projected area was determined as each particle diameter. Furthermore, based on the result, the volume average particle diameter was calculated, and the number% of particles having a size of 0.03 to 0.1 μm and particles having a size of 0.3 μm or more was calculated. The particle size was measured for particles having a particle size of 0.03 μm or more. It is also possible to measure the particle size with an image analyzer.

  When determining the volume average particle size and particle size distribution of iron oxide in the toner particles, the following measurement method is used.

  After sufficiently dispersing the toner particles to be observed in the epoxy resin, the cured product obtained by curing in an atmosphere at a temperature of 40 ° C. for 2 days was used as a flaky sample by a microtome, and a transmission electron microscope (TEM). , The projected area of each of the 100 iron oxide particles in the field of view is measured with a photograph with a magnification of 10,000 to 40,000 times, and the equivalent diameter of a circle equal to the measured projected area of each particle is The particle diameter was obtained. Further, based on the results, the number% of particles having a size of 0.03 to 0.1 μm and particles having a size of 0.3 μm or more was calculated. It is also possible to measure the particle size with an image analyzer.

  Furthermore, other colorants may be used in combination with iron oxide. Examples of coloring materials that can be used in combination include magnetic or nonmagnetic inorganic compounds, and known dyes and pigments. Specifically, for example, ferromagnetic metal particles such as cobalt and nickel, or alloys obtained by adding chromium, manganese, copper, zinc, aluminum, rare earth elements to these, hematite, titanium black, nigrosine dye / pigment, carbon black, Examples include phthalocyanine. These may also be used after treating the surface.

  The polymerization initiator used in the present invention has a half-life of 0.5 to 30 hours during the polymerization reaction. When the polymerization reaction is carried out with an addition amount of 0.5 to 20% by mass of the polymerizable monomer, the molecular weight A polymer having a maximum between 10,000 and 100,000 can be obtained, and the toner can be provided with desirable strength and suitable melting characteristics. Examples of polymerization initiators include 2,2′-azobis- (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexane-1-carbonitrile ), 2,2′-azobis-4-methoxy-2,4-dimethylvaleronitrile, azo or diazo polymerization initiators such as azobisisobutyronitrile; benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate , Peroxide polymerization initiators such as cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide.

  In the present invention, a crosslinking agent may be added, and a preferable addition amount is 0.001 to 15% by mass of the polymerizable monomer.

  In the production of toner by suspension polymerization, generally, the above-described toner composition, that is, a polymerizable monomer, contains iron oxide, a colorant, a release agent, a plasticizer, a binder, a charge control agent, a crosslinking agent, and the like. Components necessary for the toner and other additives such as an organic solvent and a dispersant added to lower the viscosity of the polymer produced by the polymerization reaction, as appropriate, homogenizer, ball mill, colloid mill, ultrasonic disperser, etc. The monomer system uniformly dissolved or dispersed by the dispersing machine is suspended in an aqueous medium containing a dispersion stabilizer. At this time, the particle size of the obtained toner particles becomes sharper by using a high-speed disperser such as a high-speed stirrer or an ultrasonic disperser to obtain a desired toner particle size at a stretch. The polymerization initiator may be added at the same time when other additives are added to the polymerizable monomer, or may be mixed immediately before being suspended in the aqueous medium. Also, a polymerization initiator dissolved in a polymerizable monomer or solvent can be added immediately after granulation and before starting the polymerization reaction.

  After granulation, stirring may be performed using a normal stirrer to such an extent that the particle state is maintained and particle floating and sedimentation are prevented. In order to appropriately segregate near the surface using the polar compound of the present invention, the pH in the aqueous medium before adding the monomer system is important. The pH is preferably 4 to 10.5. If the pH is less than 4, the effect of the polar compound almost disappears, so that a large amount of polar substance needs to be added, and the effect of lowering the charge amount, broadening of the particle size distribution, and the like occurs. On the other hand, if the pH exceeds 10.5, the addition of a polar compound promotes the exposure of some of the magnetic materials, making it difficult to maintain the magnetic structure of the present invention.

  In the suspension polymerization method of the present invention, known surfactants and organic / inorganic dispersants can be used as dispersion stabilizers. In particular, inorganic dispersants are less likely to produce harmful ultrafine powders, and their steric hindrance prevents dispersion stability. Therefore, even if the reaction temperature is changed, the stability is not easily lost, the cleaning is easy, and the toner is not adversely affected. Examples of such inorganic dispersants include polyvalent metal phosphates such as calcium phosphate, magnesium phosphate, aluminum phosphate and zinc phosphate; carbonates such as calcium carbonate and magnesium carbonate; calcium metasuccinate, calcium sulfate and barium sulfate. Inorganic salts; inorganic oxides such as calcium hydroxide, magnesium hydroxide, aluminum hydroxide, silica, bentonite and alumina can be mentioned.

  These inorganic dispersants are preferably used in an amount of 0.2 to 20 parts by mass alone or in combination of two or more with respect to 100 parts by mass of the polymerizable monomer. When aiming at a more finely divided toner having an average particle diameter of 5 μm or less, 0.001 to 0.1 parts by mass of a surfactant may be used in combination.

  Examples of the surfactant include sodium dodecylbenzene sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, sodium oleate, sodium laurate, sodium stearate, and potassium stearate.

  When these inorganic dispersants are used, they may be used as they are, but in order to obtain finer particles, the inorganic dispersant particles can be generated in an aqueous medium. For example, in the case of calcium phosphate, a sodium phosphate aqueous solution and a calcium chloride aqueous solution can be mixed with high-speed stirring to produce water-insoluble calcium phosphate, which enables more uniform and fine dispersion. At the same time, a water-soluble sodium chloride salt is produced as a by-product. However, if a water-soluble salt is present in the aqueous medium, dissolution of the polymerizable monomer in water is suppressed, and an ultrafine toner based on emulsion polymerization is produced. Since it becomes difficult to generate | occur | produce, it is more convenient. Since it becomes an obstacle when removing the remaining polymerizable monomer at the end of the polymerization reaction, it is better to replace the aqueous medium or desalinate with an ion exchange resin. The inorganic dispersant can be almost completely removed by dissolving with an acid or alkali after completion of the polymerization.

  In the polymerization step, the polymerization is performed at a polymerization temperature of 40 ° C. or higher, generally 50 to 90 ° C. When the polymerization is carried out in this temperature range, the release agent and wax to be sealed inside are precipitated by phase separation, and the encapsulation is more complete. In order to consume the remaining polymerizable monomer, the reaction temperature can be increased to 90 to 150 ° C. at the end of the polymerization reaction.

  The toner of the present invention is preferably mixed with an inorganic fine powder or a hydrophobic inorganic fine powder as a fluidity improver. For example, titanium oxide fine powder, silica fine powder, and alumina fine powder are preferably added and used, and silica fine powder is particularly preferred.

Inorganic fine powder used in the developer, specific surface area by nitrogen adsorption measured by BET method of more than 30 m ² / g, it is possible in particular in the range of 50 to 400 m ² / g give good results preferable.

  If necessary, an external additive other than the fluidity improver may be added to the toner in the present invention.

For example, for the purpose of improving cleaning properties, the primary particle diameter exceeds 30 nm (preferably the specific surface area is less than 50 m ² / g), more preferably the primary particle diameter is 50 nm or more (preferably the specific surface area is 30 m ^2). It is also one of preferable modes to add inorganic fine particles or organic fine particles that are nearly spherical at a rate of less than / g). For example, spherical silica particles, spherical polymethylsilsesquioxane particles, and spherical resin particles are preferably used.

  Still other additives, for example, lubricant powders such as polyethylene fluoride powder, zinc stearate powder, polyvinylidene fluoride powder; or abrasives such as cerium oxide powder, silicon carbide powder, strontium titanate powder; anti-caking agent; Conductivity imparting agents such as carbon black powder, zinc oxide powder and tin oxide powder; organic fine particles having opposite polarity and inorganic fine particles can be added in a small amount as a developability improver. These additives can also be used after hydrophobizing the surface.

  As described above, the external additive may be used in an amount of 0.1 to 5 parts by mass (preferably 0.1 to 3 parts by mass) with respect to 100 parts by mass of the toner.

  When the toner of the present invention is produced by a pulverization method, a known method can be used. Known methods include, for example, binder resins, mold release agents, charge control agents, and in some cases, components necessary as toners such as colorants and other additives in a mixer such as a Henschel mixer or a ball mill. After mixing, melt and knead using a heat kneader such as a heating roll, a kneader, and an extruder to disperse or dissolve other toner materials such as a magnetic material while the resins are mutually compatible. After cooling and solidification and pulverization, classification is performed, in addition, surface treatment with a magnetic material is performed, and toner particles are obtained by a multi-step process of surface treatment with resin particles, and fine powder is added and mixed as necessary. Thus, a developer can be obtained. Either the classification or the surface treatment may be performed first. In the classification step, it is preferable to use a multi-division classifier from the viewpoint of production efficiency.

  The pulverization step can be performed using a known pulverizer such as a mechanical impact type or a jet type. In order to obtain a developer having a specific circularity according to the present invention, it is preferable to further pulverize by applying heat or to add a mechanical impact in an auxiliary manner. Further, a hot water bath method in which finely pulverized (classified as necessary) toner particles are dispersed in hot water, a method of passing in a hot air stream, or the like may be used.

  As a method of applying a mechanical impact force, for example, there is a method using a mechanical impact type pulverizer such as a kryptron system manufactured by Kawasaki Heavy Industries, Ltd. or a turbo mill manufactured by Turbo Industry. Also, like devices such as Hosokawa Micron's Mechano-Fusion System and Nara Machinery's Hybridization System, the toner is pressed against the inside of the casing by centrifugal force with high-speed rotating blades, and the force of compression force, friction force, etc. A method of applying a mechanical impact force to the toner may be used.

  In the case of performing a process of applying mechanical impact, the atmosphere temperature during the process is set to a temperature near the glass transition point Tg of the toner (that is, a temperature in the range of ± 30 ° C. of the glass transition point Tg) to prevent aggregation. From the viewpoint of productivity. More preferably, the treatment at a temperature in the range of ± 20 ° C. of the glass transition point Tg of the toner is particularly effective for improving the transfer efficiency.

  Furthermore, the toner of the present invention is a method for obtaining a spherical toner by atomizing a molten mixture into air using a disk or a multi-fluid nozzle described in JP-B-56-13945, etc. Represented by a dispersion polymerization method in which a toner is directly produced using an aqueous organic solvent in which the polymer obtained in 1 is insoluble, or a soap-free polymerization method in which a toner is produced by direct polymerization in the presence of a water-soluble polar polymerization initiator. The toner can also be produced by a method of producing toner using an emulsion polymerization method or the like.

  An example of an image forming apparatus that can suitably use the toner of the present invention will be specifically described with reference to the drawings.

  In the image forming apparatus of FIG. 1, reference numeral 100 denotes a photosensitive drum, and a primary charging roller 117, a developing device 140, a transfer charging roller 114, a cleaner 116, a register roller 124, and the like are provided around the photosensitive drum. The photoreceptor 100 is charged to, for example, −700 V by the primary charging roller 117 (applied voltages are AC voltage −2.0 kVpp, DC voltage −700 Vdc). Then, exposure is performed by irradiating the photosensitive member 100 with a laser beam 123 by the laser generator 121. The electrostatic latent image on the photoconductor 100 is developed with a one-component magnetic developer by the developing device 140 and transferred onto the transfer material by the transfer roller 114 in contact with the photoconductor via the transfer material. The transfer material on which the toner image is placed is conveyed to the fixing device 126 by the conveying belt 125 or the like and fixed on the transfer material. In addition, toner remaining on a part of the photoconductor is cleaned by the cleaning unit 116. As shown in FIG. 2, the developing device 140 is provided with a cylindrical toner carrier 102 (hereinafter referred to as a developing sleeve) made of a nonmagnetic metal such as aluminum or stainless steel in the vicinity of the photosensitive member 100. The gap between 100 and the developing sleeve 102 is maintained at about 300 μm by a sleeve / photoreceptor gap holding member (not shown). A magnet roller 104 is fixed and arranged concentrically with the developing sleeve 102 in the developing sleeve. However, the developing sleeve 102 is rotatable. The magnet roller 104 is provided with a plurality of magnetic poles as shown in the figure, where S1 affects development, N1 regulates the toner coat amount, S2 takes in / conveys toner, and N2 affects toner blowout prevention. The toner is applied to the developing sleeve 102 by the toner application roller 141, and is adhered and conveyed. An elastic blade 103 is provided as a member for regulating the amount of toner conveyed, and the amount of toner conveyed to the development area is controlled by the contact pressure of the elastic blade 103 against the developing sleeve 102. In the development region, a DC and AC development bias is applied between the photoconductor 100 and the development sleeve 102, and the developer on the development sleeve flies onto the photoconductor 100 in accordance with the electrostatic latent image and becomes a visible image. .

  The method for measuring various physical property data in the present invention is described in detail below.

(1) Ratio of iron element content (B) to carbon element content (A) present on the toner surface (B / A)
The ratio (B / A) of the iron element content (B) to the carbon element content (A) present on the toner surface in the present invention was calculated by performing surface composition analysis by ESCA (X-ray photoelectron spectroscopy). .

In the present invention, the ESCA apparatus and measurement conditions are as follows.
Equipment used: 1600S type X-ray photoelectron spectrometer manufactured by PHI (Physical Electronics Industries, Inc.) Measurement conditions: X-ray source MgKα (400 W)
Spectral region 800μmφ
In the present invention, the surface atomic concentration (atomic%) was calculated from the measured peak intensity of each element using a relative sensitivity factor provided by PHI.

  As the measurement sample, toner is used. When an external additive is added to the toner, the toner is washed with a solvent that does not dissolve the toner, such as isopropanol, and the measurement is performed after removing the external additive. Do.

(2) Average circularity of toner The circularity in the present invention is used as a simple method for quantitatively expressing the particle shape. In the present invention, the flow type particle image analyzer FPIA- manufactured by Toa Medical Electronics Co., Ltd. is used. The particle shape is measured using 1000, and the circularity is obtained by the following formula. Furthermore, as shown by the following equation, a value obtained by dividing the total roundness of all the measured particles by the total number of particles is defined as the average circularity.

  In addition, “FPIA-1000” which is a measuring apparatus used in the present invention calculates the circularity of each particle, and then calculates the average circularity, and the circularity is 0.400 depending on the circularity obtained. 1.000 divided at intervals of 0.010 at intervals of 0.400 or more and less than 0.410, 0.410 or more and less than 0.420 ... 0.990 or more and less than 1.000 and 1.000 A calculation method is used in which the average circularity is calculated using the center value and frequency of the dividing points.

  There is very little error between each value of the average circularity calculated by this calculation method and each value of the average circularity calculated by the calculation formula that directly uses the circularity of each particle described above. Since it is negligible, the present invention uses the concept of the calculation formula that directly uses the circularity of each particle described above for reasons of handling data such as shortening the calculation time and simplifying the calculation calculation formula. However, such a calculation method which is partially changed is used.

  The circularity in the present invention is an index indicating the degree of unevenness of particles, and is 1.000 when the particles are completely spherical, and the circularity becomes smaller as the surface shape becomes more complicated.

  As a specific method for measuring the degree of circularity, about 5 mg of toner is dispersed in 10 ml of water in which about 0.1 mg of a nonionic surfactant is dissolved, and a dispersion is prepared, and ultrasonic waves (20 kHz, 50 W) are applied to the dispersion. And the dispersion concentration is set to 5000 to 20000 particles / μl, and the circularity distribution of particles having a circle-equivalent diameter of 3 μm or more is measured using the flow type particle image measuring apparatus.

  The outline of the measurement is described in the catalog (June 1995 edition) of FPIA-1000 published by Toa Medical Electronics Co., Ltd., the operation manual of the measuring apparatus, and JP-A-8-136439. It is.

  The sample dispersion is passed through a flat and flat transparent flow cell (thickness: about 200 μm) flow path (spread along the flow direction). The strobe and the CCD camera are mounted on the flow cell so as to be opposite to each other so as to form an optical path that passes through the thickness of the flow cell. While the sample dispersion is flowing, strobe light is irradiated at 1/30 second intervals to obtain an image of the particles flowing through the flow cell, so that each particle has a certain range parallel to the flow cell 2. Taken as a dimensional image. From the area of the two-dimensional image of each particle, the diameter of a circle having the same area is calculated as the equivalent circle diameter. The circularity of each particle is calculated from the projected area of the two-dimensional image of each particle and the perimeter of the projected image using the above circularity calculation formula.

(3) Toner particle size distribution A Coulter Counter TA-II type (manufactured by Coulter Inc.) is used as a measuring device, and an interface (manufactured by Nikkiki) that outputs number distribution and volume distribution and a CX-1 personal computer (manufactured by Canon) Connect and prepare 1% NaCl aqueous solution using 1st grade sodium chloride as electrolyte. For example, ISOTON R-II (manufactured by Coulter Scientific Japan) can be used. As a measuring method, 0.1 to 5 ml of a surfactant (preferably alkylbenzene sulfonate) is added as a dispersant to 100 to 150 ml of the electrolytic aqueous solution, and 2 to 20 mg of a measurement sample is further added. The electrolyte in which the sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and the volume and the number of toners are measured by measuring the volume and number of toners using the Coulter counter TA-II type with a 100 μm aperture as the aperture. Calculate the volume distribution and number distribution of particles of ˜40 μm. Then, the weight-based weight-average diameter D4 obtained from the number-average particle diameter (D1) volume distribution (the median value of each channel is the representative value for each channel), and the weight-based weight of 12.7 μm or more obtained from the volume distribution. Find the distribution.

(4) Measuring method of D / C and magnetic substance distribution In the present invention, as a concrete measuring method of D / C and magnetic substance distribution by TEM, there are enough particles to be observed in a room temperature curable epoxy resin. A method of observing a cured product obtained by dispersing for 2 days in an atmosphere at a temperature of 40 ° C. after dispersion as it is or by freezing it with a microtome equipped with diamond teeth is preferred.

  A specific method for determining the ratio of the number of corresponding particles is as follows. Particles for determining D / C by TEM are obtained by calculating the equivalent circle diameter from the cross-sectional area in the micrograph, and the value is a width of ± 10% of the number average particle diameter obtained by the method described later using a Coulter counter. The particles contained in the above are regarded as applicable particles, and for the corresponding 100 particles, the minimum value (D) of the distance from the magnetic particle surface is measured, D / C is obtained, and the particles having a D / C value of 0.02 or less Calculate the percentage.

  Further, the distribution of the magnetic substance is obtained by counting the number of the magnetic substance in the corresponding particle and the number of the magnetic substance outside 0.2 times the equivalent circle diameter of the present invention.

  In this case, a magnification of 10,000 to 20,000 times is suitable for the microphotograph to perform highly accurate measurement. In the present invention, a transmission electron microscope (Hitachi model H-600) was used as an apparatus, observed at an accelerating voltage of 100 kV, and observed and measured using a photomicrograph with a magnification of 10,000.

(5) Method for measuring acid value The acid value is determined as follows. Basic operation conforms to JIS-K0070.
Test by:
(1) Reagent (a) Solvent ethyl ether-ethyl alcohol mixed solution (1 + 1 or 2 + 1) or benzene-ethyl alcohol mixed solution (1 + 1 or 2 + 1), these solutions were subjected to N / 10 hydroxylation using phenolphthalein as an indicator immediately before use. Neutralize with potassium ethyl alcohol solution.
(B) Phenolphthalein solution 1 g of phenolphthalein is dissolved in 100 ml of ethyl alcohol (95 v / v%).
(C) N / 10 potassium hydroxide-ethyl alcohol solution Dissolve 7.0 g of potassium hydroxide in as little water as possible, add ethyl alcohol (95 v / v%) to 1 liter, leave it for 2 to 3 days, and filter. The standardization is performed according to JIS K 8006 (basic matters concerning titration during the reagent content test).
(2) Operation Weigh correctly 1 to 20 g of sample, add 100 ml of solvent and a few drops of phenolphthalein solution as an indicator, and shake well until the sample is completely dissolved. In the case of a solid sample, dissolve it by heating on a water bath. After cooling, this is titrated with an N / 10 potassium hydroxide ethyl alcohol solution, and the end point of neutralization is defined as the time when the indicator is slightly red for 30 seconds.
3) Calculation formula The acid value is calculated by the following formula.

ここにＡ：酸価
Ｂ：Ｎ／１０水酸化カリウムエチルアルコール溶液の使用量（ｍｌ）
ｆ：Ｎ／１０水酸化カリウムエチルアルコール溶液のファクター
Ｓ：試料（ｇ）

Where A: acid value B: N / 10 amount of potassium hydroxide ethyl alcohol solution used (ml)
f: Factor of N / 10 potassium hydroxide ethyl alcohol solution S: Sample (g)

(6) Method for measuring saponification value The saponification value is determined as follows. Basic operation conforms to JIS-K0070.

The number of mg of potassium hydroxide required to neutralize free fatty acids, resin acids, etc. contained in 1 g of the sample is called the acid value, and the test is conducted as follows.
(1) Reagent (a) Solvent ethyl ether-ethyl alcohol mixed solution (1 + 1 or 2 + 1) or benzene-ethyl alcohol mixed solution (1 + 1 or 2 + 1), these solutions were subjected to N / 10 hydroxylation using phenolphthalein as an indicator immediately before use. Neutralize with potassium ethyl alcohol solution.
(B) Phenolphthalein solution 1 g of phenolphthalein is dissolved in 100 ml of ethyl alcohol (95 v / v%).
(C) N / 10 potassium hydroxide-ethyl alcohol solution Dissolve 7.0 g of potassium hydroxide in as little water as possible, add ethyl alcohol (95 v / v%) to 1 liter, leave it for 2 to 3 days, and filter. The standardization is performed according to JIS K 8006 (basic matters concerning titration during the reagent content test).
(2) Operation Weigh correctly 1 to 20 g of sample, add 100 ml of solvent and a few drops of phenolphthalein solution as an indicator, and shake well until the sample is completely dissolved. In the case of a solid sample, dissolve it by heating on a water bath. After cooling, 100-200 ml of an excessive amount of N / 10 potassium hydroxide ethyl alcohol solution is added to this, heated to reflux for 1 hour, saponified, and then cooled. The obtained solution is back titrated with a N / 10 hydrochloric acid aqueous solution, and the end point of neutralization is taken when the indicator's slight red color disappears continuously for 30 seconds. In addition, a blank test is performed in parallel with this test. 3) Calculation formula The acid value is calculated by the following formula.
A = {(B) − (C)} × 5.611 × f / S
Where A: saponification value B: amount of N / 10 hydrochloric acid aqueous solution in the blank test (ml)
C: Amount of N / 10 hydrochloric acid aqueous solution added in this test (ml)
f: Factor of N / 10 hydrochloric acid aqueous solution S: Sample (g)

  Hereinafter, the present invention will be specifically described with reference to production examples and examples, but this does not limit the present invention in any way. In addition, all the parts in the following mixing | blending are a mass part.

<Manufacture of magnetic powder 1>
In aqueous ferrous sulfate solution, 1.0 to 1.1 equivalents of caustic soda solution with respect to iron element, 1.5 mass% sodium hexametaphosphate in terms of phosphorus element with respect to iron element, silicon with respect to iron element An aqueous solution containing ferrous hydroxide was prepared by mixing 1.5 mass% sodium silicate in terms of element.

  While maintaining the aqueous solution at pH 9, air was blown and an oxidation reaction was performed at 80 to 90 ° C. to prepare a slurry liquid for generating seed crystals. Subsequently, after adding ferrous sulfate aqueous solution to this slurry liquid so that it may become 0.9-1.2 equivalent with respect to the original alkali amount (sodium component of caustic soda), the slurry liquid is maintained at pH 8, and air is supplied. The oxidation reaction was advanced while blowing to obtain a slurry liquid containing magnetic iron oxide. This slurry is filtered, washed, dried, and then crushed. To this, 2 parts of n-octyltriethoxysilane coupling agent is added to 100 parts of magnetic iron oxide, and processed in a wheel-type kneader for 60 minutes. The surface of the magnetic powder was hydrophobized.

  5 parts of Fischer-Tropsch wax (average particle size is 30 μm) is added to 100 parts of the magnetic powder thus obtained, and the mixture is processed for 2 hours while being pressed with a wheel-type kneader, and the average particle size is 0.21 μm. Magnetic powder 1 was obtained.

<Manufacture of magnetic powder 2>
Magnetic powder 2 was obtained in the same manner as magnetic powder 1 except that Fischer-Tropsch wax was changed to polypropylene wax (average particle size: 130 μm) in the production of magnetic powder 1.

<Manufacture of magnetic powder 3>
Magnetic powder 3 was obtained in the same manner as in the production of magnetic powder 1 except that Fischer-Tropsch wax was changed to paraffin wax (average particle diameter was 60 μm) in the production of magnetic powder 1.

<Manufacture of magnetic powder 4>
In the production of the magnetic powder 1, the magnetic powder 4 was obtained in the same manner as the production of the magnetic powder 1 except that the amount of Fischer-Tropsch wax was changed from 5 parts to 0.2 parts.

<Manufacture of magnetic powder 5>
Magnetic powder 5 was obtained in the same manner as magnetic powder 1 except that the amount of Fischer-Tropsch wax was changed from 5 parts to 16 parts in the production of magnetic powder 1.

<Manufacture of magnetic powder 6>
The oxidation reaction proceeded in the same manner as in the production of the magnetic powder 1 to obtain a slurry liquid containing magnetic iron oxide. This slurry solution is filtered, washed and dried, and then sufficiently pulverized. To this, 2 parts of n-octyltriethoxysilane coupling agent is added to 100 parts of magnetic iron oxide, and processed for 60 minutes with a wheel type kneader. Magnetic powder 6 was obtained.

<Manufacture of magnetic powder 7>
The oxidation reaction proceeded in the same manner as in the production of the magnetic powder 1 to obtain a slurry liquid containing magnetic iron oxide. This slurry was filtered, washed and dried, and then sufficiently crushed. 5 parts of Fischer-Tropsch wax (average particle size is 30 μm) was added to 100 parts of the magnetic powder thus obtained, and the mixture was processed for 2 hours while being pressed with a wheel-type kneader to obtain a magnetic powder 7.

  The physical properties of the above magnetic powders 1 to 7 are shown in Table 1.

<Manufacture of magnetic toner 1>
An aqueous medium containing a dispersion stabilizer by adding 450 parts of a 0.1M Na ₃ PO ₄ aqueous solution to 720 parts of ion-exchanged water and heating to 60 ° C., and then adding 67.7 parts of a 1.0 M CaCl ₂ aqueous solution. Got.

Styrene 74 parts n-Butyl acrylate 26 parts Divinylbenzene 0.5 part Saturated polyester resin [Mn = 11000, Mw / Mn = 2.4,
Acid value = 30 mgKOH / g, Tg = 72 ° C.] 6 parts Negative charge control agent / T-77 (Hodogaya Chemical) 1 part Magnetic powder 1 95 parts Polar compound 1 (styrene-maleic anhydride copolymer) [Ken Chemical value = 150, Mp = 3000] 0.1 part The above formulation was uniformly dispersed and mixed using an attritor (Mitsui Miike Chemical Co., Ltd.).

  This monomer composition was heated to 60 ° C., and 10 parts of polyethylene wax (maximum endothermic peak in DSC 65 ° C., half-end width of endothermic peak 17 ° C.) was added and dissolved therein. A polymerizable monomer composition was prepared by dissolving 4 parts of butyl-oxy-2-ethylhexanoate.

The polymerizable monomer composition was put into the aqueous medium in the previous period and stirred at 10,000 rpm for 15 minutes in a TK homomixer (Special Machine Industries Co., Ltd.) at 60 ° C. and N ₂ atmosphere. Grained. Thereafter, the mixture was reacted at 80 ° C. for 8 hours while stirring with a paddle stirring blade. After completion of the reaction, the suspension was cooled, hydrochloric acid was added to dissolve the dispersant, the dispersant was dissolved, filtered, washed with water, and dried to obtain toner particles 1.

100 parts of the toner particles and silica having a primary particle diameter of 12 nm are treated with hexamethyldisilazane and then treated with silicone oil, and 1.0 part of hydrophobic silica fine powder having a BET value of 120 m ² / g after the treatment is obtained. Magnetic toner 1 was prepared by mixing using a Henschel mixer (Mitsui Miike Chemical Co., Ltd.). Table 2 shows the physical properties of the magnetic toner 1.

<Manufacture of magnetic toner 2>
Magnetic toner 2 was obtained in the same manner as in the production of magnetic toner 1 except that the addition amount of polar compound 1 was changed from 0.1 part to 0.05 part. Table 2 shows the physical properties of the magnetic toner 2.

<Manufacture of magnetic toner 3>
The magnetic toner 3 was prepared in the same manner as in the production of the magnetic toner 1 except that the magnetic powder 7 was used instead of the magnetic powder 1 and the addition amount of the polar compound 1 was changed from 0.1 part to 1.0 part. Obtained. Table 2 shows the physical properties of the magnetic toner 3.

<Manufacture of magnetic toner 4>
After adding 25 parts of emulsified particles (styrene-methacrylic acid, particle size 0.05 μm) to 100 parts of the toner particles obtained in the production of the magnetic toner 1, an impact surface treatment apparatus (treatment temperature 50 ° C., Film toner particles were obtained by repeatedly fixing and forming a film using a rotating processing blade peripheral speed of 90 m / sec.). In the same manner as in the production of magnetic toner 1, 1.0 part of hydrophobic silica fine powder was externally added to obtain magnetic toner 4. Table 2 shows the physical properties of the magnetic toner 4.

<Manufacture of magnetic toner 5>
A magnetic toner 5 was obtained in the same manner as in the production of the magnetic toner 1 except that the magnetic powder 1 was changed to the magnetic powder 2. Table 2 shows the physical properties of the magnetic toner 5.

<Manufacture of magnetic toner 6>
A magnetic toner 6 was obtained in the same manner as in the production of the magnetic toner 1 except that the magnetic powder 1 was changed to the magnetic powder 3. Table 2 shows the physical properties of the magnetic toner 6.

<Manufacture of magnetic toner 7>
A magnetic toner 7 was obtained in the same manner as in the production of the magnetic toner 1 except that the magnetic powder 1 was changed to the magnetic powder 4. Table 2 shows the physical properties of the magnetic toner 7.

<Manufacture of magnetic toner 8>
A magnetic toner 8 was obtained in the same manner as in the production of the magnetic toner 1 except that the magnetic powder 1 was changed to the magnetic powder 5. Table 2 shows the physical properties of the magnetic toner 8.

<Manufacture of magnetic toner 9>
The magnetic toner 9 was prepared in the same manner as in the production of the magnetic toner 1 except that the polar compound 1 was changed to 5.0 parts of the polar compound 2 (styrene-methacrylic acid copolymer) [saponification number = 18, Mp = 6200]. Got. Table 2 shows the physical properties of the magnetic toner 9.

<Manufacture of magnetic toner 10>
The magnetic toner was prepared in the same manner as in the production of the magnetic toner 1 except that the polar compound 1 was changed to 0.05 part of the polar compound 3 (styrene-maleic anhydride copolymer) [saponification number = 220, Mp = 4300]. 10 was obtained. Table 2 shows the physical properties of the magnetic toner 10.

<Manufacture of magnetic toner 11>
A magnetic toner 11 was obtained in the same manner as in the production of the magnetic toner 1 except that the polyethylene wax was changed to paraffin wax (maximum endothermic peak 78 ° C. in DSC, half-width of endothermic peak 9 ° C.). Table 2 shows the physical properties of the magnetic toner 11.

<Manufacture of magnetic toner 12>
Styrene / n-butyl acrylate copolymer (mass ratio 74/26)
(Mn = 24300, Mw / Mn = 3.0) 100 parts Saturated polyester resin [Mn = 11000, Mw / Mn = 2.4,
Acid value = 30 mg KOH / g, Tg = 72 ° C.] 5 parts Negative charge control agent T-77 (manufactured by Hodogaya Chemical) 1 part Magnetic powder 1 30 parts Polar compound 1 [saponification number = 150, Mp = 3000] 0 .1 part Polyethylene wax used in the production of magnetic toner 1 5 parts The above materials are mixed in a blender, melt kneaded with a biaxial extruder heated to 110 ° C., and the cooled kneaded material is coarsely pulverized with a hammer mill. The coarsely pulverized product was finely pulverized with a turbo mill (manufactured by Turbo Kogyo Co., Ltd.), and the resulting finely pulverized product was subjected to air classification to obtain toner particles having a weight average particle diameter of 6.0 μm.

  Thereafter, 65 parts of magnetic powder 1 is externally added to 100 parts of the toner particles, and the surface of the magnetic material is applied using an impact surface treatment apparatus (treatment temperature 55 ° C., rotary treatment blade peripheral speed 90 m / sec.). Then, 8 parts of emulsified particles (styrene-methacrylic acid, particle size 0.05 μm) were externally added to 100 parts of magnetic substance-fixed toner particles, and then an impact surface treatment apparatus (treatment temperature 50 ° C., Using a rotating processing blade peripheral speed of 90 m / sec.), Fixation and film formation were performed to obtain coated toner particles. In the same manner as in the production of magnetic toner 1, 1.0 part of hydrophobic silica fine powder was externally added to 100 parts of the obtained toner particles to prepare magnetic toner 12. Table 2 shows the physical properties of the magnetic toner 12 obtained.

<Manufacture of magnetic toner 13>
Styrene / n-butyl acrylate copolymer (mass ratio 74/26)
(Mn = 24300, Mw / Mn = 3.0) 100 parts Saturated polyester resin [Mn = 11000, Mw / Mn = 2.4,
Acid value = 30 mg KOH / g, Tg = 72 ° C.] 5 parts Negative charge control agent T-77 (manufactured by Hodogaya Chemical) 1 part Magnetic powder 1 95 parts Polar compound 1 [saponification number = 150, Mp = 3000] 0 .1 part Polyethylene wax used in the production of magnetic toner 1 5 parts The above materials are mixed in a blender, melt kneaded with a biaxial extruder heated to 110 ° C., and the cooled kneaded material is coarsely pulverized with a hammer mill. The coarsely pulverized product was finely pulverized with a turbo mill (manufactured by Turbo Kogyo Co., Ltd.), and the resulting finely pulverized product was subjected to air classification to obtain toner particles having a weight average particle diameter of 6.5 μm.

  In the same manner as in the production of the magnetic toner 1, 1.0 part of hydrophobic silica fine powder was externally added to 100 parts of the obtained toner particles to prepare a magnetic toner 13. Table 2 shows the physical properties of the magnetic toner 13 obtained.

<Manufacture of magnetic toner 14>
A magnetic toner 14 was obtained in the same manner as in the production of the magnetic toner 1 except that the magnetic powder 1 was changed to the magnetic powder 6. Table 2 shows the physical properties of the magnetic toner 14.

<Example 1>
As the image forming apparatus, LBP-1760 was remodeled and the one having the structure shown in FIG. 1 was used.

The potential of the electrostatic image bearing member (photoreceptor drum) was set to dark portion potential V _d = −650 V and light portion potential V _L = −130 V. The gap between the electrostatic charge image carrier and the developing sleeve is 270 μm, and the surface of the toner carrier is blasted with a resin layer having a layer thickness of about 7 μm and a JIS centerline average roughness (RA) of 1.0 μm. A developing sleeve formed on an aluminum cylinder having a diameter of 16φ is used, and a developing magnetic pole of 85 mT (850 gauss), a urethane regulating blade having a thickness of 1.0 mm and a free length of 0.5 mm as a toner regulating member is 39.2 N / m (40 g). / Cm).
Phenol resin 100 parts Graphite (particle size approx. 7 μm) 90 parts Carbon black 10 parts

Next, a DC bias component V _dc = −450 V, an overlapping AC bias component V _pp = 1600 V, and F = 2200 Hz were used as the developing bias. The peripheral speed of the developing sleeve was 110% (259 mm / sec) in the forward direction with respect to the peripheral speed of the photosensitive member (235 mm / sec). The transfer bias was set to 1.5 kV DC.

  As a fixing method, there was used a fixing device of LBP-1760 which does not have an oil application function and which is fixed by heating and pressing with a heater through a film. At this time, a pressure roller having a fluororesin surface layer was used, and the diameter of the roller was 30 mm. The fixing temperature was set to 180 ° C. and the nip width was set to 7 mm.

100 g of magnetic toner 1 is filled in a cartridge, and the image pattern consists of only a horizontal line with a printing rate of 2% in a normal temperature and humidity environment (23 ° C., 60% RH) and a low temperature and low humidity environment (15 ° C., 10% RH). An image printing test of 5000 sheets was performed. Note that 75 g / m ² of paper was used as the transfer material.

  As a result, the toner 1 did not have a decrease in density at the initial stage and after the image was printed on 5000 sheets, and a good image without fogging on the non-image area was obtained. In addition, it was excellent in low-temperature fixability and offset resistance, and was able to take a wide fixing temperature range. Table 3 shows the evaluation results under a normal temperature and humidity environment, and Table 4 shows the evaluation results under a low temperature and low humidity environment.

  The evaluation items described in the examples of the present invention and the comparative examples and the judgment criteria thereof will be described.

(Fixability)
Using a modified LBP-1760 machine, a fixing test was performed in a normal temperature and humidity environment. The image area ratio at this time was 25%, and the applied toner amount per unit area was set to 0.6 mg / cm ² . The process speed was set to 235 mm / sec. The fixing start temperature is measured by adjusting the set temperature of the fixing device every 5 ° C. within a temperature range of 130 to 230 ° C., outputting a fixed image at each temperature, and obtaining the fixed image at 4.9 kPa. The fixing temperature at which the density reduction rate before and after the rubbing was 10% or less was determined as the fixing start temperature by rubbing with a Silbon paper to which a load of 50 g / cm ² was applied. Further, regarding the high temperature offset temperature, the stain on the image and the back of the paper was visually evaluated.

(Image density)
The image density formed a solid image portion, and this solid image was measured with a Macbeth reflection densitometer (manufactured by Macbeth).

(Fog)
The fog was measured using a REFECTMETER MODEL TC-6DS manufactured by Tokyo Denshoku. The filter used was a green filter, and fog was calculated from the following formula.
Fog (reflectance) (%) = reflectance on standard paper (%) − reflectance of sample non-image area (%)

The criteria for fogging are as follows.
A: Very good (less than 1.5%)
B: Good (1.5% or more to less than 2.5%)
C: Normal (2.5% or more to less than 4.0%)
D: Poor (4% or more)

(Dot reproducibility)
The dot reproducibility was evaluated by performing an image formation test using a checker pattern of 80 μm × 50 μm shown in FIG.
A: 2 or less defects in 100 B: 3 to 5 defects in 100 C: 6 to 10 defects in 100 D: 11 or less defects in 100

(Coloring power)
Adjust the toner weight per unit area to 0.6 mg / cm ² on A4 plain paper for copying machines (75 g / m ² ), and output an image with many 10 mm x 10 mm solid images for density measurement. The image density at this time was evaluated. The image density was evaluated based on the following using a “Macbeth reflection densitometer” (manufactured by Macbeth).
A: 1.55 or more B: 1.40 or more, less than 1.55 C: 1.20 or more, less than 1.40 D: less than 1.20

<Examples 2 to 12>
Magnetic toners 2 to 12 were used as toners, and image printing tests, fixing properties evaluations and durability evaluations were performed under the same conditions as in Example 1. As a result, there were no problems in the initial image characteristics, and no problem was obtained in any of up to 5000 prints. Table 3 shows the evaluation results under a normal temperature and humidity environment, and Table 4 shows the evaluation results under a low temperature and low humidity environment.

<Comparative Examples 1-2>
Magnetic toners 13 and 14 were used as toners, and an image printing test, a fixing property evaluation, and a durability evaluation were performed under the same conditions as in Example 1. As a result, the fogging of the magnetic toner 13 was deteriorated along with the durability test, and the image density was particularly lowered in a low temperature and low humidity environment. Further, the fixing area of the magnetic toner 14 was narrow. Table 3 shows the evaluation results under a normal temperature and humidity environment, and Table 4 shows the evaluation results under a low temperature and low humidity environment.

1 is a schematic diagram illustrating an example of an image forming apparatus used in an embodiment of the present invention. It is explanatory drawing of the checker pattern for testing the development characteristic of a toner.

Explanation of symbols

100 photoconductor (image carrier, charged body)
102 Developing sleeve (magnetic toner carrier)
114 Transfer roller (transfer member)
116 Cleaner 117 Charging roller (contact charging member)
121 Laser beam scanner (latent image forming means, exposure device)
124 Feed roller 125 Conveying member 126 Fixing device 140 Developing device 141 Stirring member

Claims (10)

A toner containing at least a binder resin and iron oxide,
I) Assuming that the projected area equivalent diameter of the toner is C, in the cross-sectional observation of the toner using a transmission electron microscope (TEM), the iron oxide has a depth of 0.2 times the projected area equivalent diameter C from the toner surface. In addition, the toner satisfying the structure of 70% by number or more is 40% by number or more,
II) A magnetic toner, wherein the iron oxide is treated with a low softening point substance. In cross-sectional observation of the magnetic toner, there are 60% by number or more of toners that satisfy the structure in which the iron oxide exists at a depth of 0.2 times the diameter C equivalent to the projected area from the toner surface. The magnetic toner according to claim 1, wherein the toner is a magnetic toner. The ratio (B / A) of the abundance (B) of iron element to the abundance (A) of carbon element present on the surface of the magnetic toner particle measured by X-ray photoelectron spectroscopy of the magnetic toner is 0.001. The magnetic toner according to claim 1, wherein the magnetic toner is less than 1. The toner satisfying the relationship of D / C ≦ 0.02 is 50% by number or more, where D is the minimum distance between the iron oxide and the toner surface in cross-sectional observation of the magnetic toner. Item 4. The magnetic toner according to any one of Items 1 to 3. The magnetic toner according to claim 1, wherein the low softening point substance has a peak top of an endothermic peak in a region of 80 ° C. to 150 ° C. in DSC measurement. The magnetic toner according to claim 1, wherein a processing amount of the low softening point substance with respect to 100 parts by mass of the iron oxide is 0.3 to 15 parts by mass. The magnetic toner according to claim 1, wherein the magnetic toner has an average circularity of 0.970 or more. The magnetic toner according to claim 1, wherein the magnetic toner has a weight average particle diameter of 2 to 10 μm. The magnetic toner according to claim 1, wherein the magnetic toner contains a polar compound. 10. The magnetic toner according to claim 9, wherein the polar compound is a compound having a saponification value of 20 to 200.

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