JP4670698B2 - External additive for toner, toner for electrostatic charge development, developer for electrostatic charge development, and image forming method - Google Patents

Description

  The present invention relates to an external additive for toner used in a copying machine or the like for forming an image by an electrophotographic method, an electrostatic charge developing toner using the same, an electrostatic charge developing developer, and an image forming method. .

  Compared to conventional toners produced by the pulverization method etc., the polymerized toner produced by the aggregation coalescence method etc. is suitable for forming high-quality images because the particle size distribution and shape distribution are sharp, It is easy for toner to pass between a member to be cleaned such as an image carrier and a blade, and cleaning failure is likely to occur. Therefore, when polymerized toner is used as a cleaning means in an apparatus equipped with a cleaning blade, there is a problem that cleaning cannot be performed unless the linear pressure of the blade is set higher than that of pulverized toner.

Further, if the linear pressure of the blade with respect to the image carrier is increased in order to improve the cleaning property, the stress due to the friction between the surface of the image carrier and the cleaning blade increases, so that the blade is likely to deteriorate. Further, when a wear-type organic image carrier is used as the image carrier, the surface scratches are worsened.
By simply increasing the linear pressure of the blade in order to make full use of the polymerized toner, the toner can be cleaned without any problems in the initial stage of image formation, but as the image is formed over a long period of time, the deterioration of the blade and the occurrence of scratches on the surface of the image carrier are accelerated. As a result, defective cleaning tends to occur.

In order to suppress deterioration of the blade and scratches on the surface of the image carrier, it is necessary to reduce the friction between the image carrier and the cleaning blade, which is usually an external additive present on the toner surface. The effect by is great.
On the other hand, in a tandem image forming apparatus, for example, when a large amount of black and white images are continuously formed, the friction between the contact portion of the blade and the image carrier on the surface of the image carrier for color image formation In other words, the toner (external additive) having a function of reducing the toner continues to be idled without being newly supplied.
Since a certain external additive is interposed in the vicinity of the contact portion between the image carrier and the cleaning blade, aggregation of the external additive is formed in the vicinity of the contact portion between the image carrier and the cleaning blade. The
When a part of the aggregation of the external additive comes off and passes through the contact portion between the cleaning blade and the image carrier, a non-contact portion (gap) is generated between the image carrier and the blade, and the toner ( There is a problem in that poor cleaning of the external additive occurs and the image quality deteriorates due to a decrease in the performance of the image carrier.

  As means for improving the cleaning failure, for example, the blade side (see Patent Documents 1 to 8 etc.), the image carrier side (see Patent Document 9 etc.), the external additive (lubricant) side (Patent Documents 10 to 15). Etc.) and the like.

  As a means from the blade side, for example, a blade material having high hardness can be used. However, a material with high hardness is prone to permanent deformation (so-called “sagging”) over time, so that the edge part in contact with the image carrier will be sagged during long-term use, and the edge part will be stably pressed. The force cannot be pressed against the image carrier, resulting in poor cleaning. There is also a method of forming a low friction layer on the blade edge. However, if the low friction layer itself is worn, the above-described problem occurs. In addition, the vibration of the cleaning blade is absorbed by selecting the elastic member constituting the blade, and the cleaning failure can be suppressed to some extent, but the stress during cleaning is concentrated on the edge portion, There is also a problem that the edge portion is deformed during long-term use and the cleaning accuracy is deteriorated.

  As a means from the image carrier side, use of an image carrier having high wear resistance can be mentioned. However, in an image carrier having high wear resistance, the surface of the image carrier is hard to be worn and high torque is likely to be generated. Therefore, in order to obtain cleaning properties, it is necessary to increase the linear pressure of the blade against the image carrier. When polymerized toner is used, higher performance is required for friction reduction. Further, when an external additive having a substantially cubic shape having a sharp particle size distribution is used, since the rolling friction is high and it is difficult to enter the contact portion between the blade and the image carrier, an image using polymerized toner is used. Under the condition where the linear pressure of the blade against the carrier is high, it is difficult to sufficiently reduce the torque, and the blade is likely to be worn.

  An approach from the side of the lubricant having a function of reducing the friction between the contact portion of the blade and the photosensitive member includes selection of the amount of use. However, if the amount of lubricant applied is too small, it will not be able to exert a sufficient effect on image carrier wear, scratches, and blade deterioration, and if applied excessively, problems such as scattering and blurring in the transfer process (deterioration of image quality) will occur. May occur.

On the other hand, silica, titania and the like are generally used as external additives for the purpose of improving charging characteristics and the like. In addition, in order to suppress the burying of external additives and maintain high developability and transferability over time regardless of the initial stage, spherical large-diameter silica having a broad particle size distribution produced by a vapor phase method and true specific gravity are used. It is also disclosed that it is effective to use monodispersed spherical large-diameter silica of 1.9 or less (see Patent Documents 16 and 17). This low specific gravity monodispersed spherical silica is known to be effective because it rolls easily and is easily interposed between the blade and the image carrier, and is effective in improving cleaning properties ( (See Patent Documents 17 and 18).
JP-A-7-306616 JP-A-8-27227 Japanese Patent Laid-Open No. 9-258632 Japanese Patent Laid-Open No. 11-24522 JP 2002-214989 A JP 2002-287591 A JP 2002-287593 A JP 2003-208068 A JP 2005-316225 A JP 2000-75752 A JP-A-8-13754 JP 2002-244485 A JP 2001-337558 A Japanese Patent Laid-Open No. 10-142897 JP 2004-102236 A JP 2001-0666820 A Japanese Patent Laid-Open No. 2005-4051

As described above, monodispersed spherical silica with a low specific gravity is easy to roll, so it is easy to enter the contact portion between the image carrier and the cleaning blade, and silica agglomeration is formed at the contact portion between the image carrier and the blade. It is easy and does not cause poor cleaning in the initial stage. However, a part of the aggregation collapses with time, and a non-contact portion (gap) is generated between the image carrier and the blade, resulting in poor cleaning. On the other hand, spherical silica produced by the vapor phase method has a problem that the true specific gravity is larger than 1.9, it is difficult to form a seal between the blade and the image carrier without any gap, and cleaning failure is likely to occur. It was.
An object of the present invention is to solve the above problems. That is, the present invention relates to an external additive for toner that suppresses the occurrence of poor cleaning that has occurred when conventional silica is used as an external additive, and an electrostatic charge developing toner and electrostatic charge developing using the same. It is an object of the present invention to provide a developer and an image forming method.

  In order to solve the above-described poor cleaning, the present inventors have formed agglomeration (seal) of the external additive without any gap at the contact portion between the image carrier and the cleaning blade, and cleaning over time. Two points were considered that the non-contact part (gap) that causes the defect was not generated. That is, the aggregation of the external additive formed in the vicinity of the contact portion between the image carrier and the cleaning blade has a high closest packing property, and the external additive itself has a low specific gravity. The agglomeration of the external additive is formed without any gap at the contact portion, and the occurrence of defective cleaning is initially suppressed. In addition, a part of the aggregation is not easily broken, and even if a part of the aggregation is broken, the silica is easily rearranged so as to directly fill the gap. It is considered that a cleaning failure due to the contact portion hardly occurs.

Therefore, the present inventors considered that it is important that silica used as an external additive has a wide particle size distribution and a low specific gravity.
That is, if the particle size distribution is wide, the close-packing property is essentially excellent, so that the agglomeration is easily formed and the agglomeration is not easily broken. In addition to this, if the specific gravity is low, residual particles such as alcohol, water or voids are contained in the particles, so that silanol groups remain in the particles and are soft as particles, and are easily deformed when pressure is applied. Therefore, the closest packing property is further improved, and since the small-diameter component is contained, the silica can be easily rearranged when a part of the aggregation is broken.
That is, if the silica particle size distribution is wide and the specific gravity is low, the contact portion between the image carrier and the cleaning blade can be filled without any gaps, and the individual silica particles can be deformed themselves while maintaining high fluidity. As a result, gentle aggregation can be formed.

  In contrast, if silica has a wide particle size distribution, it tends to form dense aggregates, but if it has a high specific gravity (ie, high hardness), the residual solvent, water, or voids are few and the particle skeleton is dense. In addition, since the silica is difficult to deform, the physical affinity between the silicas is low. Therefore, the aggregation is easily broken, and when a part of the aggregation is broken, the silica is rearranged (replaced), but the cleaning is liable to occur. In addition, if the particle size of the silica is too uniform, the silica is liable to be deformed at a low specific gravity and tends to form a dense agglomeration, but when a part of the agglomeration breaks down, the silica is rearranged (replaced). Hard to happen.

  Further, if the silica itself has a low hardness, it is considered that the surface of the image carrier is hardly damaged even if agglomeration is formed at the contact portion between the image carrier and the blade. In addition to these, if the silica forms a slow agglomeration, the friction between the image carrier and the blade can be reduced, and the torque of the contact portion between the image carrier and the blade can be easily reduced. It is considered that a stable cleaning performance can be maintained over a long period of time because the loosely aggregated portion of the external additive is easily refreshed. Based on the above findings, the present inventors have found the following present invention.

That is, the present invention
<1>
A silica having a number average particle size in the range of 100 to 150 nm, a standard deviation in the number particle size distribution exceeding 0.77 times the number average particle size, and a true specific gravity of 1.9 or less. This is an external additive for toner.

<2>
An electrostatic charge developing toner, wherein the toner external additive according to <1> is externally added.

<3>
<2> The electrostatic charge developing toner according to <2>, wherein cerium oxide is externally added.

<4>
An electrostatic charge developing developer comprising the electrostatic charge developing toner according to <2> or <3>.

<5>
An electrostatic latent image forming step of forming an electrostatic latent image on the surface of the image carrier, and developing the electrostatic latent image with the developer for electrostatic charge development according to <4>, A developing step for forming a toner image, a transfer step for transferring the toner image from the surface of the image carrier to a recording medium, and a surface of the image carrier after the toner image is transferred by a cleaning blade that abuts the surface. An image forming method comprising: a cleaning step of cleaning; and a fixing step of fixing the transferred toner image to the recording medium.

  As described above, according to the present invention, an external additive for toner that suppresses the occurrence of poor cleaning that occurs when conventional silica is used as an external additive, and electrostatic charge development using the same. Toner, electrostatic charge developing developer and image forming method can be provided.

(External additive for toner)
The external additive for toner of the present invention (hereinafter sometimes referred to as “silica external additive of the present invention”) has a number average particle size in the range of 100 to 150 nm, and the standard deviation in the number particle size distribution is It includes silica having a number average particle diameter of more than 0.77 times and a true specific gravity of 1.9 or less.
Therefore, if the toner externally added with the external additive for toner of the present invention is used, it is possible to suppress the occurrence of poor cleaning that occurs when conventional silica is used as the external additive.

Here, the silica external additive of the present invention needs to have a number average particle diameter in the range of 100 to 150 nm, and preferably in the range of 100 to 130 nm. When the number average particle size is less than 100 nm, it is difficult to separate from the externally added toner particle main body, so that the cleaning performance itself is reduced by interposing between the image carrier and the cleaning blade to reduce friction. become unable. On the other hand, if it exceeds 150 nm, the particle size is too large, so that it is difficult to enter between the image carrier and the blade, and it is difficult to form the aggregated form intended by the present invention, so that poor cleaning tends to occur.
In addition, the standard deviation in the number particle size distribution of the silica external additive of the present invention needs to exceed 0.77 times the number average particle size, and is preferably 1.00 times the number average particle size or more. . When the standard deviation is 0.77 times or less of the number average particle diameter, silica is rearranged (replaced) when a part of the agglomeration formed at the contact portion between the image carrier and the cleaning blade is broken. Becomes insufficient and causes a cleaning failure. From the viewpoint of suppressing cleaning failure, it is preferable that the standard deviation in the number particle size distribution is large. However, if it is too large, particles on the large diameter side of the particle size distribution enter the contact portion between the blade and the image carrier. It may be difficult to do. Therefore, in practice, the standard deviation in the number particle size distribution is preferably 1.50 times or less.

  Here, the standard deviation in the number average particle diameter and the number particle size distribution was measured using a scanning electron microscope (SEM: S-4700, manufactured by Hitachi, Ltd.). The externally added toner particles are observed with a scanning electron microscope (SEM: S-4700, manufactured by Hitachi, Ltd.) in 100 fields (50000 times), and circular particles corresponding to the image area of each external additive. The average particle size (average value of major axis and minor axis: obtained by approximating a circle) was measured at about 1000 locations, and the average value was taken as the number average particle size of the external additive. In addition, when a plurality of types of external additives are externally added, mapping is performed at an acceleration voltage of 20 kV using an energy dispersive X-ray analyzer EMAX model 6923H (manufactured by HORIBA) attached to the electron microscope S4100. The drug type was determined.

On the other hand, the true specific gravity of the silica external additive of the present invention is required to be 1.9 or less, and more preferably 1.5 or less. When the true specific gravity exceeds 1.9, the silica particle skeleton is dense and hard, so that it is resistant to physical deformation. In this case, since the silica particles are not sufficiently deformed, aggregation is likely to be lost, and formation of slow aggregation becomes difficult.
The true specific gravity is preferably small, but if it is too small, the void ratio in the silica particles becomes high, so that it becomes weak against physical shock and easily deforms due to stress in the developing machine or machine. In some cases, the rolling property is lowered, the entry of the image carrier and the blade into the contact portion is suppressed, and the cleaning property cannot be exhibited. Therefore, the true specific gravity is preferably 1.2 or more.

In addition, in this invention, true specific gravity was measured based on 5-2-1 of JIS-K-0061: 92 using a Le Chatelier specific gravity bottle. Specifically, the measurement was performed according to the following procedure.
(1) About 250 ml of ethyl alcohol is put into a Lechatelier specific gravity bottle and adjusted so that the meniscus is at the position of the scale.
(2) The specific gravity bottle is immersed in a constant temperature water bath, and when the liquid temperature reaches 20.0 ± 0.2 ° C., the position of the meniscus is accurately read with the scale of the specific gravity bottle (accuracy is 0.025 ml).
(3) About 100.000 g of a sample is weighed and its mass is defined as W.
(4) Put the weighed sample in a specific gravity bottle to remove bubbles.
(5) The specific gravity bottle is immersed in a constant temperature water bath, and when the liquid temperature reaches 20.0 ± 0.2 ° C., the position of the meniscus is accurately read with the scale of the specific gravity bottle (accuracy is 0.025 ml).

After carrying out the operations (1) to (5) above, the specific gravity was calculated based on the following formulas (1) and (2).
Formula (1) D = W / (L2-L1)
Formula (2) S = D / 0.9982
In the formulas (1) and (2), D is the density of the sample (20 ° C.) (g / cm ³ ), S is the specific gravity of the sample (20 ° C.), W is the apparent mass (g) of the sample, L1 is the reading of the meniscus at a liquid temperature of 20 ° C. before the sample is placed in the density bottle (ml), and L2 is the reading of the meniscus at the liquid temperature of 20 ° C. after the sample is placed in the density bottle (20 ° C.) (ml) ), And the constant “0.9982” in the formula (2) is the density of water (g / cm ³ ) at 20 ° C.

As a method for producing the silica external additive of the present invention, a known silica particle production method can be used, but in a process involving firing at a high temperature such as a vapor phase oxidation method as shown in Patent Document 16, the true specific gravity is obtained. Therefore, it is preferable to use a sol-gel method capable of low-temperature synthesis because it is impossible or difficult to control the value of 1.9 or less.
In addition, in the sol-gel method, in general, a baking treatment is often performed. However, since it is easy to control the true specific gravity to 1.9 or less, the silica external additive of the invention is manufactured. It is particularly preferable that the baking treatment is not performed before the surface treatment step. That is, it is particularly preferable that the silica external additive of the present invention is produced using a sol-gel method, and the maximum process temperature during production is 75 ° C. or less. In order to control the true specific gravity to 1.9 or less, it is preferable that a solvent having a high boiling point remains in the silica gel during the drying step. Therefore, alcohol having a high boiling point is preferably used as a solvent, and 2-propanol, tert-butyl alcohol, and the like are more preferable. Further, when N, N-dimethylformaldehyde or formaldehyde is used as a dry solvent or a small amount thereof is added, gel shrinkage is inhibited and the true specific gravity can be reduced.

In this case, the silica external additive of the present invention is produced mainly through three steps of hydrolysis, condensation polymerization, and hydrophobization treatment, and may be carried out by combining other steps such as drying as necessary.
Here, the particle size is in the range of 100 to 150 nm by controlling the weight ratio of alkoxysilane, catalyst such as ammonia and acid, alcohol, water, reaction temperature, stirring rate, and supply rate in the hydrolysis and condensation polymerization step. Can be adjusted in.
Also, the particle size distribution can be adjusted in the hydrolysis step by the weight ratio of alkoxysilane, catalyst, alcohol, water, reaction temperature, stirring rate, and supply rate, so that the standard deviation in the number particle size distribution is 0. The particle size distribution can be adjusted in a broad direction to exceed 77 times.

In addition, as a method of controlling the particle size distribution in a broad direction, it is preferable to use a method of making the hydrolysis reaction nonuniform in the hydrolysis step. As a result, a sol having a broad particle size distribution can be obtained, and thus a silica external additive having a standard deviation in the number particle size distribution exceeding 0.77 times the number average particle size can be obtained through a gelation process.
In order to make the hydrolysis reaction non-uniform, for example, a method using at least two kinds of alkoxides can be mentioned. Alkoxysilane used as a raw material varies in the rate of hydrolysis depending on the type of alkoxy group, and generally the larger the alkoxyl group, the lower the rate of hydrolysis. The reaction can be heterogeneous.

Therefore, a sol having a wide particle size distribution can be obtained by performing a hydrolysis reaction using at least two types of alkoxysilanes. For example, tetraethoxysilane and diphenyldiethoxysilane, or a combination of tetramethoxysilane and tert-butyldimethylchlorosilane may be mentioned. Alkyl of two or more types of alkoxysilanes used as raw materials in the production of silica external additives There is no particular limitation as long as the molecular sizes (or carbon numbers) of the groups are different from each other.
In addition, when water or acid is added in a system with a high hydrolysis rate, such as when an alkoxysilane with a high hydrolysis rate such as tetramethoxysilane is used, a portion with a high moisture concentration is generated. A sol having non-uniformity and a wide particle size distribution can be obtained. Moreover, the same effect can be obtained also by slowly or slowly stirring the system.

Next, the outline of the production process of the silica external additive of the present invention by the sol-gel method will be described below. First, an alkoxysilane is dropped and stirred while adding a catalyst and applying temperature in the presence of water and alcohol. Next, the silica sol suspension obtained by the reaction is centrifuged to separate into wet silica gel, alcohol and aqueous ammonia. A solvent is added to wet silica gel to form a silica sol again, and a hydrophobizing agent is added to hydrophobize the silica surface. Alternatively, after the sol is dried to obtain a dry sol, a hydrophobizing agent is added, and the silica surface is hydrophobized.
As the hydrophobizing agent, a general coupling agent, silicone oil, fatty acid, fatty acid metal salt, or the like can be used. Next, the silica external additive of the present invention can be obtained by removing the solvent from the hydrophobized silica sol and drying it. Further, the silica external additive thus obtained may be subjected to a hydrophobic treatment again.
For example, a dry method such as a spray drying method in which a treatment agent or a solution containing a treatment agent is sprayed on particles suspended in a gas phase, or a wet method in which particles are immersed in a solution containing a treatment agent and dried. Or by a mixing method in which the treatment agent and particles are mixed by a mixer. Further, after the surface treatment, a step of washing with a solvent and removing a residual treatment agent or a low-boiling residue may be added.

As the silane compound used as the hydrophobizing agent, a water-soluble compound can be used. As such a silane compound, what is shown by following Structural formula (1) can be utilized.
Structural formula (1) R _a SiX _4-a
Here, in the structural formula (1), a is an integer of 0 to 3, R represents an organic group such as a hydrogen atom, an alkyl group, and an alkenyl group, and X represents a chlorine atom, a methoxy group, an ethoxy group, and the like. Represents a hydrolyzable group.

Examples of the compound represented by the structural formula (1) include chlorosilane, alkoxysilane, silazane, and a special silylating agent. Specifically, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, tetraethoxysilane, Methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, isobutyltrimethoxysilane, decyltrimethoxysilane, hexamethyldisilazane, N, O- (bistrimethylsilyl) acetamide, N, N-bis (Trimethylsilyl) urea, tert-butyldimethylchlorosilane, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxy Silane, γ-methacryloxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-mercapto Representative examples include propyltrimethoxysilane and γ-chloropropyltrimethoxysilane.
Particularly preferably, the hydrophobizing agent used in the present invention includes dimethyldimethoxysilane, hexamethyldisilazane (HMDS), methyltrimethoxysilane, isobutyltrimethoxysilane, decyltrimethoxysilane and the like.

Specific examples of silicone oils include, for example, organosiloxane oligomers; cyclic compounds such as octamethylcyclotetrasiloxane or decamethylcyclopentasiloxane, tetramethylcyclotetrasiloxane, tetravinyltetramethylcyclotetrasiloxane, linear or branched Can be mentioned. Alternatively, a highly reactive silicone oil in which a modifying group is introduced at a side chain, one end, both ends, side chain one end, side chain both ends, or the like may be used. Examples of the modifying group include alkoxy, carboxyl, carbinol, higher fatty acid modification, phenol, epoxy, methacryl, amino and the like, but are not particularly limited. Further, it may be a silicone oil having several kinds of modifying groups such as amino / alkoxy modification.
Further, dimethyl silicone oil, these modified silicone oils, and other surface treatment agents may be mixed or used in combination (such as silane coupling agents (including HMDS), etc.). ). Examples of the treating agent used in combination include silane coupling agents, titanate coupling agents, aluminate coupling agents, various silicone oils, fatty acids, fatty acid metal salts, esterified products thereof, rosin acid, and the like. .
The viscosity of the silicone oil is preferably 500 centistokes or less because it is easy to uniformly adhere to the surface of the external additive particles. More preferably, 300 centistokes or less is more suitable for use, and even more preferably 200 centistokes or less.

(Static charge developing toner)
The electrostatic charge developing toner of the present invention (hereinafter sometimes abbreviated as “toner”) is not particularly limited as long as it is externally added with the above-described silica external additive of the present invention. External additives can be added in combination. In addition, cerium oxide is mentioned as an external additive suitable for using together with the silica external additive of this invention.
Silica forms hard agglomerates when the surface treatment agent on the surface of the silica particles changes due to rubbing heat or moisture (external additive content or moisture) at the contact portion between the image carrier and the cleaning blade. Has a function of making it brittle by reacting with silica (silica external additive of the present invention) adhering to the blade, so that formation of hard agglomeration of silica can be further suppressed.
Note that since Ce of cerium oxide has an electronic state similar to Si, it can be replaced with Si atoms in silica (SiO ₂ ) formed by covalent bonding of Si and O. On the other hand, since Ce—O bond is less covalent than Si—O bond, when Si in silica is replaced with Ce, it becomes impossible to maintain the network of silica Si—O bond, and Ce is replaced with Ce. The part is destroyed with a weaker force. Therefore, the occurrence of hard aggregation of silica as described above can be effectively suppressed.

-Other external additives-
In addition to the silica external additive of the present invention and the above-described cerium oxide, conventionally known external additives may be used in combination with the toner of the present invention, if necessary.
Examples of these other external additives include known inorganic materials such as inorganic fine particles, charge control agents, lubricants, abrasives, and cleaning aids for the purpose of improving charging characteristics, powder characteristics, transfer characteristics, and cleaning characteristics. An external additive composed of fine particles and / or resin fine particles can be externally added to the toner particles.

Known inorganic fine particles can be used. For example, silica (however, the number average particle diameter is outside the range of 100 to 150 nm), titania, metatitanic acid, zinc oxide, zirconia, magnesia, calcium carbonate, magnesium carbonate, calcium phosphate, cerium oxide, strontium titanate, etc. It is done. In addition, it is preferable to perform the water-repellent treatment like the external additive of the present invention.
Examples of the resin fine particles include spherical particles such as PMMA (polymethyl methacrylate), nylon, melamine, benzoguanamine, and fluorine, and amorphous powders such as vinylidene chloride and fatty acid metal salts.

  In the present invention, a fatty acid metal salt may be contained in the toner particles for the purpose of controlling the polishing amount and / or polishing uniformity of the image carrier. Examples of fatty acid metal salts include higher fatty acid metal salts. Specific examples of the higher fatty acid metal salt include zinc stearate, aluminum stearate, copper stearate, magnesium stearate, etc., zinc oleate, manganese oleate, iron oleate, copper oleate, olein Oleic acid metal salts such as magnesium acid, zinc palmitate, copper palmitate, magnesium palmitate, etc., linoleic acid metal salts such as zinc linoleate, ricinoleic acid metal salts such as zinc ricinoleate and lithium ricinoleate Etc. A fatty acid calcium salt is particularly preferable from the viewpoint of preventing the cleaning blade and the image carrier from being worn.

-Amount of external additive-
The addition amount of the silica external additive of the present invention with respect to the toner particles is preferably in the range of 0.1% by weight to 5.0% by weight with respect to 100 parts by weight of the toner particles, and 0.5% by weight to 2.0%. More preferably within the range of% by weight.
If the addition amount is less than 0.1% by weight, the amount is too small, and a sufficient cleaning effect may not be obtained. On the other hand, if it exceeds 5.0% by weight, the amount may be so large that the surface of the image carrier may be easily damaged.

The amount of cerium oxide added to the toner particles is preferably in the range of 0.1% by weight to 2.0% by weight, preferably 0.1% by weight to 0.5% by weight, based on 100 parts by weight of the toner particles. Within the range is more preferable.
If the addition amount is less than 0.1% by weight, the amount is too small, and the effect of reducing hard aggregation of silica may not be sufficiently obtained. On the other hand, if it exceeds 2.0% by weight, the toner basic characteristics such as toner charging characteristics and powder fluidity may be deteriorated.

  When other external additives other than those described above are used, the amount of addition is 0.1% by weight to 5% with respect to the toner particles, although it depends on the configuration and amount of the external additive of the present invention. It is preferable to be within a range of about 0.0% by weight. When the amount is less than 0.1% by weight, the surface of the toner base particles is exposed to a large extent, and the characteristics of the toner base particles become dominant, and secondary obstacles such as deterioration of powder characteristics tend to occur. When the amount is more than 5.0% by weight, the fixing property may be deteriorated, which is not preferable.

-Toner particles-
As the toner particles constituting the toner of the present invention, known ones can be used. Specifically, those containing a binder resin and a colorant and, if necessary, a release agent and other components are used. it can. Hereinafter, the toner of the present invention will be described in more detail.

-Binder resin-
As the binder resin used for the toner particles, a known resin can be used, and a crystalline resin, or a crystalline resin and an amorphous resin may be used in combination because excellent low-temperature fixability can be obtained.
Binder resins include styrenes such as styrene and chlorostyrene; monoolefins such as ethylene, propylene, butylene and isoprene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate and vinyl butyrate; methyl acrylate , Α-methylene aliphatic monocarboxylic acid esters such as ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate; vinyl Homopolymers and copolymers of vinyl ethers such as methyl ether, vinyl ethyl ether, vinyl butyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, vinyl isopropenyl ketone; Typical binder resins include polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer. Examples thereof include coalescence, polyethylene, and polypropylene. Further examples include polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin wax and the like.
Among these, styrene-alkyl acrylate copolymers and styrene-alkyl methacrylate copolymers are particularly preferable.

  Specific examples of the crystalline resin include adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, tridecanedioic acid and other long-chain alkyl dicarboxylic acids, butanediol, pentanediol, and hexane. Polyester resins using diols such as diol, heptanediol, octanediol, nonanediol, decanediol, batyl alcohol and other long-chain alkyl and alkenyl diols; amyl (meth) acrylate, hexyl (meth) acrylate, (meth) acrylic Heptyl acid, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, tridecyl (meth) acrylate, myristyl (meth) acrylate, (meth) acrylic acid Cetyl, (meth) acrylic acid And vinyl resins using long-chain alkyls such as ryl, oleyl (meth) acrylate, and behenyl (meth) acrylate, and (meth) acrylic esters of alkenyl; and the like, to a recording medium such as paper at the time of fixing. Polyester resin based crystalline resins are preferred from the standpoints of adhesion, chargeability, and ease of adjusting the melting point within a desired range.

-Colorant-
The colorant is not particularly limited and may be either a dye or a pigment, but a pigment is preferable from the viewpoint of light resistance and water resistance.
Preferred pigments include carbon black, aniline black, aniline blue, calcoil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, rose bengal, Quinacridone, benzidine yellow, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 185, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 180, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 74, C.I. I. Pigment blue 15: 1, C.I. I. A known pigment such as CI Pigment Blue 15: 3 can be used.
Magnetic powder can also be used as a colorant. As the magnetic powder, known magnetic materials such as ferromagnetic metals such as cobalt, iron and nickel, alloys and oxides of metals such as cobalt, iron, nickel, aluminum, lead, magnesium, zinc and manganese can be used.
The above colorants can be used alone or in combination of two or more. The content of the colorant contained in the toner of the present invention is preferably 0.1 to 40 parts by weight, more preferably 1 to 30 parts by weight with respect to 100 parts by weight of the toner particles. In addition, each color toner such as yellow toner, magenta toner, cyan toner, and black toner can be obtained by appropriately selecting the type of colorant.

-Other internal components-
Other components such as a release agent and a charge control agent may be internally added to the toner particles as necessary.
Generally as a mold release agent, it uses for the purpose of improving mold release property. Specific examples of the release agent include low molecular weight polyolefins such as polyethylene, polypropylene, and polybutene; silicones having a softening point by heating; fatty acid amides such as oleic acid amide, erucic acid amide, ricinoleic acid amide, and stearic acid amide Kinds: Plant waxes such as carnauba wax, rice wax, candelilla wax, tree wax, jojoba oil; animal waxes such as beeswax; montan wax, ozokerite, ceresin, paraffin wax, microcrystalline wax, Fischer-Tropsch wax, etc. Mineral / petroleum waxes; ester waxes such as fatty acid esters, montanic acid esters, and carboxylic acid esters. In this invention, these mold release agents may be used individually by 1 type, and may use 2 or more types together.

The content of the release agent is preferably 1 to 20 parts by weight, more preferably 2 to 15 parts by weight with respect to 100 parts by weight of the toner particles. If the amount is less than 1 part by weight, there is no effect of adding a release agent. If the amount exceeds 20 parts by weight, an adverse effect on the chargeability tends to appear, and the toner is easily destroyed inside the developing machine. In addition to the effect that the resin is spent on the carrier and the charge is likely to be lowered, for example, when color toner is used, the image surface tends to be insufficiently oozed out at the time of fixing. In some cases, the release agent tends to stay therein, so that the transparency is deteriorated, which is not preferable.
The melting point of the release agent is preferably 50 to 120 ° C, more preferably 60 to 100 ° C. If the melting point of the release agent is less than 60 ° C., the change temperature of the release agent is too low, and the blocking resistance may be inferior, or the developability may deteriorate when the temperature in the copying machine increases.

  In addition, a charge control agent may be added to the toner particles as necessary. Known charge control agents can be used, but azo metal complex compounds, metal complex compounds of salicylic acid, and resin type charge control agents containing polar groups can be used. When the toner is manufactured by a wet manufacturing method, it is preferable to use a material that is difficult to dissolve in water in terms of controlling ionic strength and reducing wastewater contamination.

-Toner particle size-
The toner particles preferably have a small particle diameter for the purpose of improving the image quality. However, if the diameter is too small, development is difficult with the conventional system from the viewpoint of charging and fluidity. From such a viewpoint, the volume average particle diameter of the toner particles is preferably in the range of 2 to 8 μm, and more preferably in the range of 4 to 7 μm.
When the volume average particle diameter of the toner particles exceeds 8 μm, the image quality such as fine line reproducibility and halftone granularity deteriorates, and it may be difficult to obtain good image quality when outputting photographic image quality. . Further, when the volume average particle diameter of the toner particles is less than 2 μm, the powder characteristics and the charging characteristics are very deteriorated, and it may be difficult to output at high speed by the conventional image forming apparatus.
The value of volume average particle size / number average particle size, which is an index of particle size distribution, is preferably 1.6 or less, and more preferably 1.5 or less. When this value is larger than 1.6, the spread of the particle size distribution becomes large, so that the distribution of the charge amount becomes wide, and reverse polarity toner and low-charge toner are likely to be generated.

In the present invention, the volume average particle diameter (cumulative volume average particle diameter D ₅₀ ), number average particle diameter (cumulative number average particle diameter D _50P ) and various particle size distribution indices of the toner are Coulter Multisizer II (Beckman- The electrolyte can be measured using ISOTON-II (Beckman-Coulter).
In the measurement, 0.5 to 50 mg of a measurement sample is added to 2 ml of a 5% aqueous solution of a surfactant, preferably sodium alkylbenzenesulfonate as a dispersant. This is added to 100-150 ml of electrolyte.
The electrolyte in which the sample is suspended is dispersed for about 1 minute with an ultrasonic disperser, and the particle size distribution of particles in the range of 2 to 60 μm is measured using a Coulter Multisizer II with an aperture diameter of 100 μm. To do. The number of particles to be sampled is 50,000.
For the particle size range (channel) divided on the basis of the particle size distribution measured in this way, the cumulative distribution is drawn from the smaller diameter side for the volume and number, respectively, and the cumulative particle size average particle size is 16%. Diameter D _16v , Cumulative number average particle diameter D _16P , Cumulative volume average particle diameter D _50v , Cumulative volume average particle diameter D _50v , Cumulative number average particle diameter D _50P , Cumulative volume average particle diameter D _84v , cumulative number average particle size D _84P .
Using these, the volume average particle size distribution index (GSDv) is calculated as (D _84v / D _16V ) ^1/2 and the number average particle size distribution index (GSDp) is calculated as (D _84P / D _16P ) ^1/2 .

-Toner production method-
For the production of toner particles, a known wet method or dry method can be used. For example, a binder resin, a colorant, and, if necessary, a release agent, a charge control agent, and the like are kneaded, pulverized, and classified. A kneading and pulverizing method; a method of changing the shape of particles obtained by the kneading and pulverizing method by mechanical impact force or thermal energy; an emulsion polymerization of a polymerizable monomer of a binder resin, and a dispersion formed; An emulsion polymerization aggregation method in which a dispersion liquid in which a colorant is dispersed and a dispersion liquid such as a release agent and a charge control agent used as necessary are mixed, aggregated, and heat-fused to obtain toner particles; Suspension polymerization method in which a polymerizable monomer for obtaining a binder resin, a colorant, and, if necessary, a solution of a release agent, a charge control agent, etc. are suspended in an aqueous solvent for polymerization; Granulation by suspending resin, colorant and, if necessary, solution of release agent, charge control agent, etc. in aqueous solvent And the like can be used; dissolution suspension method that.
In addition, toner particles obtained by the above method can be used as a core, and resin particles can be further adhered, and then heat-fused to produce a toner having a core-shell structure.

Subsequently, the toner of the present invention can be obtained by adding the silica external additive of the present invention and, if necessary, other external additives to the toner particles thus obtained and mixing them.
The mixing of the toner particles and the external additive can be performed by a known method, for example, a V blender, a Henshur mixer, a Ladyge mixer or the like. Furthermore, if necessary, the toner obtained using a vibration classifier, a wind classifier, or the like may be classified to remove coarse particles.
Further, as an external addition method to the toner, even if the silica external additive of the present invention and other external additives are added and mixed at the same time, after the silica particles of the present invention are added and mixed first, other external additives are added. Even if it is added and mixed, the silica external additive of the present invention may be added and mixed after the other external additives are added and mixed first.

(Developer for electrostatic charge development)
The developer for electrophotography of the present invention is not particularly limited as long as it contains the toner of the present invention. Specifically, the one-component developer comprising only the toner of the present invention, or the toner and carrier of the present invention. Any of two-component developers consisting of
As the carrier, it is preferable in terms of charge controllability and resistance controllability to use a resin-coated carrier having a resin coating layer in which a conductive material is dispersed and contained in a matrix resin on a core material. As an average particle diameter of a carrier core material, generally 10-100 micrometers is preferable and 20-80 micrometers is more preferable. If it is smaller than 10 μm, the magnetic force per carrier particle may be reduced, and carrier jump may easily occur. If it is larger than 100 μm, there may be a problem that sufficient charge cannot be imparted to the toner or the image deteriorates.
The core material of the carrier is not particularly limited, and examples thereof include magnetic metals such as iron, steel, nickel and cobalt, magnetic oxides such as ferrite and magnetite, glass beads, and the like, from the viewpoint of using the magnetic brush method. Is preferably a magnetic carrier.

Coating resins include polyethylene, polypropylene, polystyrene, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether, polyvinyl ketone, vinyl chloride-vinyl acetate copolymer, styrene-acrylic acid copolymer Examples thereof include straight silicone resins composed of coalesced or organosiloxane bonds or modified products thereof, fluororesins, polyesters, polyurethanes, polycarbonates, phenol resins, amino resins, melamine resins, benzoguanamine resins, urea resins, amide resins, epoxy resins, etc. However, it is not limited to these.
The average film thickness of the resin coating layer formed by the above method is usually 0.1 to 10 μm, preferably 0.2 to 5 μm. When the thickness is 0.1 μm or less, the core is easily peeled off and the core is easily exposed over time, and the charge imparting ability and the resistance may be lowered, and a stable image quality may not be obtained. When the film thickness is 10 μm or more, the change with time does not easily occur, but the resistance becomes too high, so that the image quality may deteriorate or the fluidity may deteriorate.

In order to reduce the resistance while increasing the film thickness, the resin matrix may contain conductive powder. Examples of the conductive material include metals such as gold, silver and copper, and titanium oxide, zinc oxide, barium sulfate, aluminum borate, potassium titanate, tin oxide, carbon black, magnetite, and the like. Is not to be done.
The content of the conductive material is preferably 1 to 50 parts by weight and more preferably 3 to 20 parts by weight with respect to 100 parts by weight of the matrix resin.
If the carrier resistance is too low, the carrier may adhere to the image portion of the image carrier due to charge injection from the sleeve, or the latent image charge may escape through the carrier, resulting in a latent image distortion or image loss. May cause problems. On the other hand, when the carrier resistance is high, the carrier charge is less likely to leak, resulting in an edged image, but on the other hand, the edge effect is that the image density at the center is very thin on a large image area. May arise.

  Examples of the method for producing the carrier include an immersion method in which the powder of the carrier core material is immersed in a solution for forming the coating layer, a spray method in which the solution for forming the coating layer is sprayed on the surface of the carrier core material, and the carrier core material is fluidized air. The fluidized bed method in which the coating layer forming solution is sprayed in a suspended state, the kneader coater method in which the carrier core material and the coating layer forming solution are mixed in the kneader coater to remove the solvent, and the coating resin is made into fine particles. Examples of the powder coating method include a carrier core material and a kneader coater which are mixed at a melting point or higher and cooled to form a film, and the kneader coater method and the powder coat method are particularly preferably used.

  The mixing ratio (weight ratio) between the toner of the present invention and the carrier in the two-component developer is in the range of toner: carrier = 1: 100 to 30: 100, and in the range of 3: 100 to 20: 100. Is more preferable.

(Image forming method)
The image forming method of the present invention can use a known electrophotographic method as long as an image can be formed using the developer of the present invention. Specifically, an electrostatic latent image is formed on the surface of the image carrier. Forming an electrostatic latent image, developing the electrostatic latent image with the developer of the present invention to form a toner image on the surface of the image carrier, and transferring the toner image from the surface of the image carrier to a recording medium A transfer process, a cleaning process for cleaning the surface of the image carrier after the toner image has been transferred by a cleaning blade in contact with the image carrier, and a fixing process for fixing the transferred toner image to the recording medium. Is preferred.
In image formation using a tandem image forming apparatus, when a large amount of black and white images are continuously formed, the surface of the image carrier for color image formation is brought into contact with the blade and the photosensitive member. The toner (external additive) that has the function of reducing the torque of the part continues to be idle without being newly supplied, and the specific external additive receives the linear pressure of the blade at the abutting part, so the image is carried Rearrangement hardly occurs when a part of the aggregation of the external additive collapses in the vicinity of the contact portion between the body and the cleaning blade.
Therefore, it is particularly preferable that the image forming method of the present invention is carried out using a tandem image forming apparatus. Even in such a case, if the developer of the present invention is used, the aggregation formed in the vicinity of the contact portion between the image carrier and the cleaning blade is not hard and is excellent in that it is loose aggregation. The cleaning property can be maintained for a long time.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to the following examples. In the following description, “parts” means “parts by weight” unless otherwise specified.

[Production of colored particles]
<Preparation of resin particle dispersion>
・ Styrene 296 parts ・ N-butyl acrylate 104 parts ・ Acrylic acid 6 parts ・ Dodecanethiol 9 parts ・ Divinyl adipate 1.6 parts (above, manufactured by Wako Pure Chemical Industries, Ltd.)
10 parts of a nonionic surfactant (Sanyo Kasei Co., Ltd .: Nonipol 400) and an anionic surfactant (Daiichi Kogyo Seiyaku Co., Ltd .: Neogen SC) 8 Ion exchange with 8 parts of ammonium persulfate (manufactured by Wako Pure Chemical Industries, Ltd.) dissolved in 610 parts of ion-exchanged water, dispersed in a flask, emulsified, and slowly mixed for 10 minutes. 50 parts of water was added and nitrogen substitution was performed at 0.1 liter / min for 20 minutes. Thereafter, the contents in the flask are heated with an oil bath until the content reaches 70 ° C., and emulsion polymerization is continued as it is for 5 hours, and a resin fine particle dispersion having an average particle size of 200 nm and a solid content concentration of 40% ( 1) was prepared. When a part of the dispersion was left on an oven at 100 ° C. to remove moisture, DSC (differential scanning calorimeter) measurement was carried out. As a result, the glass transition point was 53 ° C. and the weight average molecular weight was 33,000. Met.

<Preparation of colored dispersion (1A)>
Cyan pigment B15: 3 manufactured by Dainichi Seika Co., Ltd .: cyanine blue 4937) 10 parts anionic surfactant 10 parts (Neogen RK: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
490 parts of ion-exchanged water The above components are mixed, dissolved, and dispersed for 10 minutes using a homogenizer (Ultra Turrax T50: manufactured by IKA) to disperse colorant (Cyan pigment) particles having an average particle diameter of 250 nm. A colored dispersant (1A) was prepared.

<Preparation of colored dispersion (2A)>
The colorant is C.I. I. The colorant dispersion (2A) was prepared in the same manner as the colorant dispersion (1A), except that it was changed to CI Pigment Red 122 (Quinacridone pigment: manufactured by Dainichi Seika Co., Ltd .: Chromofine Magenta 6887). The average particle size was 220 nm.

<Preparation of colored dispersion (3A)>
The colorant is C.I. I. The colorant dispersion (3A) was prepared in the same manner as the colorant dispersion (1A) except that the pigment yellow 74 (monoazo pigment: manufactured by Dainichi Seika Co., Ltd .: Seika First Yellow 2054) was used. The average particle size was 240 nm.

<Releasing agent dispersion A>
100 parts of paraffin wax (HNP0190: manufactured by Nippon Seiwa Co., Ltd., melting point 85 ° C.)
Anionic surfactant 10 parts (manufactured by Lion Corporation: Lipal 860K)
400 parts of ion-exchanged water The above components were dispersed for 10 minutes in a round stainless steel flask using a homogenizer (Ultra Turrax T50: manufactured by IKA), and then dispersed with a pressure discharge type homogenizer to obtain an average particle diameter. A release agent dispersion A in which release agent particles having a diameter of 550 nm are dispersed was prepared.

(Production of colored particles Cyan)
-Resin particle dispersion 320 parts-Colored dispersion (1A) 80 parts-Release agent dispersion A 96 parts-Aluminum sulfate (manufactured by Wako Pure Chemical Industries, Ltd.) 1.5 parts-Ion-exchanged water 1270 parts Was placed in a round stainless steel flask with a temperature control jacket and dispersed for 5 minutes at 5,000 rpm using a homogenizer (manufactured by IKA, Ultra Tarrax T50). It was left stirring for 4 minutes with 4 paddles. Thereafter, the mixture was heated with a mantle heater while stirring and heated at a heating rate of 1 ° C./min until the inside reached 48 ° C., and held at 48 ° C. for 20 minutes. Next, 80 parts of the resin particle dispersion was gradually added and kept at 48 ° C. for 30 minutes, and then a 1N aqueous sodium hydroxide solution was added to adjust the pH to 6.5.

Thereafter, the temperature was raised to 95 ° C. at a rate of 1 ° C./min and held for 30 minutes. A 0.1N aqueous nitric acid solution was added to adjust the pH to 4.8, and the mixture was allowed to stand at 95 ° C. for 2 hours. Thereafter, the 1N aqueous sodium hydroxide solution was further added to adjust the pH to 6.5, and the mixture was allowed to stand at 95 ° C. for 5 hours. Thereafter, it was cooled to 30 ° C. at 5 ° C./min.
The resulting toner particle dispersion was filtered, (A) 2,000 parts of ion-exchanged water at 35 ° C. was added to the obtained toner particles, (B) allowed to stand for 20 minutes, and (C) then filtered. After the operations from (A) to (C) were repeated 5 times, the toner particles on the filter paper were transferred to a vacuum dryer and dried at 45 ° C. and 1,000 Pa or less for 10 hours. The reason why the pressure is 1,000 Pa or less is that the above-mentioned toner particles are in a water-containing state, and in the initial stage of drying, the water freezes even at 45 ° C. and then the water sublimates. This is because is not constant. However, it was stable at 100 Pa at the end of drying. After returning the inside of the dryer to normal pressure, this was taken out to obtain colored particles Cyan.
The obtained colored particles Cyan had a D50v of 5.8 μm, a GSDp of 1.23, a glass transition temperature of 53 ° C., and a shape factor SF1 of 132.

(Production of colored particles Magenta)
Colored particles Magenta were produced in the same manner as the cyan toner, except that the colorant dispersion (1A) was changed to the color dispersion (2A) that is a magenta colorant.
The obtained colored particles Magenta had a D50v of 5.6 μm, a GSDp of 1.22, a glass transition temperature of 53 ° C., and a shape factor SF1 of 134.

(Production of colored particles Yellow)
Colored particles Yellow were prepared in the same manner as the cyan toner except that the colorant dispersion (1A) was changed to the color dispersion (3A), which is a yellow colorant.
The obtained colored particles Yellow had a D50v of 5.8 μm, a GSDp of 1.22, a glass transition temperature of 53 ° C., and a shape factor SF1 of 133.

<Generation of carrier>
Ferrite particles (volume average particle size: 50 μm) 100 parts toluene 14 parts styrene-methyl methacrylate copolymer (component ratio: 90/10) 2 parts carbon black (Regal 330: manufactured by Cabot Corporation) 0.2 parts First, ferrite particles The above components other than the above are stirred with a stirrer for 10 minutes to prepare a dispersed coating solution, and then this coating solution and ferrite particles are placed in a vacuum degassing kneader and stirred at 60 ° C. for 30 minutes. The carrier was obtained by degassing by depressurization while heating and drying. This carrier had a volume resistivity of 10 ¹¹ Ωcm at an applied electric field of 1000 V / cm.

-Preparation of silica external additive-
A method for producing a large-diameter size silica external additive (a silica external additive having a number average particle diameter exceeding 80 nm) used in the examples is shown below.

(Preparation of silica external additive (1))
In a nitrogen atmosphere, 80 parts of ethanol, 80 parts of 2-propanol, 6 parts of tetraethoxysilane, 6 parts of tert-butyldimethylchlorosilane, and 6 parts of distilled water are placed in a reaction vessel and stirred at 80 rpm. 14 parts of aqueous ammonia was added dropwise over 4 minutes. After stirring at 30 ° C. for 3.5 hours, the mixture was concentrated using an evaporator until the liquid volume became half. Thereto, 10 parts of tert-butyl alcohol and 300 parts of distilled water were added, and the product was precipitated by a centrifugal settling machine. After removing the supernatant by decantation, 300 parts of distilled water was added and separation was carried out in the same manner by a centrifugal sedimentator. After repeating this several times, the precipitate was freeze-dried with a freeze dryer for 2 days to obtain a white powder. 10 parts of this white powder was added to 300 parts of toluene and 1 part of HMDS, stirred for 30 minutes at room temperature, concentrated to dryness, and dried by heating at 120 ° C. for 1 hour. Thereafter, the mixture was further added to 100 parts of HMDS, subjected to ultrasonic wave for 30 minutes, stirred at room temperature, concentrated to dryness, and heated and dried at 120 ° C. for 1 hour, followed by true specific gravity 1.5, number average particle size 130 nm, standard deviation 138 (number average) White powder having a particle size of 0.77 = 100.1 and a number average particle size of 1.00 = 130 was obtained.

(Preparation of silica external additive (2))
Instead of using tert-butyldimethylchlorosilane in combination, 9 parts of tetraethoxysilane and 3 parts of diphenyldiethoxysilane were used. While stirring at 60 rpm, 20% aqueous ammonia was added dropwise over 40 minutes. -True specific gravity 1.9, number average particle size 110 nm, standard deviation 100 (number average particle size x 0.77 = 84.84) in the same manner as silica external additive (1) except that butyltrimethoxysilane was used. 7, a number average particle size × 1.00 = 110) white powder was obtained.

(Preparation of silica external additive (3))
Tert-butyl alcohol was used instead of 2-propanol, and 20 parts of 20% aqueous ammonia was added dropwise over 8 minutes while stirring at 100 rpm, so that the amount of tert-butyl alcohol added after concentration was 300 parts. In the same manner as in the silica external additive (1), true specific gravity 1.3, number average particle size 140 nm, standard deviation 150 (number average particle size × 0.77 = 107.8, number average particle size × 1) (0.00 = 140) white powder was obtained.
(Preparation of silica external additive (4))

  Using tert-butyl alcohol instead of 2-propanol, 20 parts of 20% aqueous ammonia was added dropwise over 15 minutes while stirring at 80 rpm, and the amount of tert-butyl alcohol added after concentration was adjusted to 300 parts. In the same manner as in the silica external additive (1), true specific gravity 1.3, number average particle size 140 nm, standard deviation 135 (number average particle size × 0.77 = 107.8, number average particle size × 1) (0.00 = 140) white powder was obtained.

(Preparation of silica external additive (5))
A true specific gravity of 1.5, a number average particle size of 90 nm, and a standard deviation of 80 (standard deviation 80) are obtained in the same manner as the silica external additive (1) except that 20% aqueous ammonia is added dropwise over 40 minutes while stirring at 60 rpm. A white powder having a number average particle diameter × 0.77 = 69.3) was obtained.

(Preparation of silica external additive (6))
The true specific gravity is the same as that of the silica external additive (1) except that 20% ammonia water is dropped over 10 minutes while stirring at 200 rpm and i-butyltrimethoxysilane is used instead of HMDS. A white powder having a number average particle diameter of 1.5, a standard deviation of 180 nm (number average particle diameter × 0.77 = 154) was obtained.

(Preparation of silica external additive (7))
Gas phase method silica (UFP-30, manufactured by Denki Kagaku Kogyo) having a number average particle size of 130 nm was used, and HMDS treatment was performed in the same manner as the silica external additive (1). A white powder having a true specific gravity of 2.2, a number average particle size of 110 nm, and a standard deviation of 90 (number average particle size × 0.77 = 84.7) was obtained.

(Preparation of silica external additive (8))
Using 160 parts of ethanol without 2-propanol and 12 parts of tetraethoxysilane without using tert-butyldimethylchlorosilane, 20% aqueous ammonia was added dropwise over 10 minutes while stirring at 100 rpm. In the same manner as the external silica additive (1) except that i-butyltrimethoxysilane was used instead of HMDS, the true specific gravity was 1.5, the number average particle size was 135 nm, and the standard deviation was 29 (number average particle size). × 0.77 = 103.95) white powder was obtained.

(Developer adjustment)
[Example 1]
1 part of hydrophobic titanium oxide having a number average particle diameter of 21 nm (T805, manufactured by Nippon Aerosil Co., Ltd.), 1.2 parts of hydrophobic silicon oxide having a number average particle diameter of 40 nm (RX50, manufactured by Nippon Aerosil Co., Ltd.) After blending 1 part of silica external additive (1) with a Henschel mixer at a peripheral speed of 32 m / s × 10 minutes, coarse particles were removed using a 45 μm mesh sieve to obtain a toner. 100 parts of the carrier and 5 parts of the toner were stirred at 40 rpm for 20 minutes using a V-blender, and sieved with a sieve having a 177 μm mesh to obtain a developer.

[Example 2]
1 part of hydrophobic titanium oxide (T805, manufactured by Nippon Aerosil Co., Ltd.) having a number average particle diameter of 21 nm and 1 part of silica external additive (2) are blended with 100 parts of the colored particles Magenta using a Henschel mixer at a peripheral speed of 32 m / s × 10 minutes. After that, coarse particles were removed using a 45 μm mesh sieve to obtain a toner. 100 parts of the carrier and 5 parts of the toner were stirred at 40 rpm for 20 minutes using a V-blender, and sieved with a sieve having a 177 μm mesh to obtain a developer.

[Example 3]
After blending 1.5 parts of silica external additive (3) to 100 parts of the above colored particles with a Henschel mixer at a peripheral speed of 32 m / s × 10 minutes, hydrophobic silicon oxide (R974, Japan) having a number average particle diameter of 12 nm. 1 part Aerosil), 1.2 parts hydrophobic silicon oxide with a number average particle size of 40 nm (RX50, made by Nippon Aerosil Co., Ltd.), blend at a peripheral speed of 20 m / s × 5 minutes, and use a 45 μm mesh sieve Thus, coarse particles were removed to obtain a toner. 100 parts of the carrier and 5 parts of the toner were stirred at 40 rpm for 20 minutes using a V-blender, and sieved with a sieve having a 177 μm mesh to obtain a developer.

[Example 4]
After blending 1.5 parts of the silica external additive (4) to 100 parts of the above colored particles Cyan using a Henschel mixer for a peripheral speed of 32 m / s × 10 minutes, hydrophobic titanium oxide (T805, Japan) 1.2 parts of Aerosil) and 1.2 parts of hydrophobic silicon oxide having a number average particle size of 30 nm (NA50H, manufactured by Nippon Aerosil Co., Ltd.), blended at a peripheral speed of 20 m / s × 5 minutes, and sieved 45 μm mesh The coarse particles were removed using a toner to obtain a toner. 100 parts of the carrier and 5 parts of the toner were stirred at 40 rpm for 20 minutes using a V-blender, and sieved with a sieve having a 177 μm mesh to obtain a developer.

[Example 5]
After blending 1.5 parts of silica external additive (1) with 100 parts of the above colored particles Cyan using a Henschel mixer at a peripheral speed of 32 m / s × 10 minutes, hydrophobic titanium oxide having a number average particle diameter of 21 nm (T805, Japan) 1.2 parts of Aerosil) and 1.2 parts of hydrophobic silicon oxide having a number average particle size of 30 nm (NA50H, manufactured by Nippon Aerosil Co., Ltd.), blended at a peripheral speed of 20 m / s × 5 minutes, and sieved 45 μm mesh The coarse particles were removed using a toner to obtain a toner. 100 parts of the carrier and 5 parts of the toner were stirred at 40 rpm for 20 minutes using a V-blender, and sieved with a sieve having a 177 μm mesh to obtain a developer.

[Example 6]
1 part of hydrophobic silicon dioxide (R974, manufactured by Nippon Aerosil Co., Ltd.) having a number average particle size of 12 nm, 1 part of silica external additive (1), and hydrophobic silicon dioxide having a number average particle size of 40 nm (RX50, Nippon Aerosil Co., Ltd.) 1 part, 1 part of cerium oxide with a number average particle size of 0.85 μm was blended using a Henschel mixer for a peripheral speed of 32 m / s × 10 minutes, and then coarse particles were removed using a 45 μm mesh sieve. The toner was obtained. 100 parts of the carrier and 5 parts of the toner were stirred at 40 rpm for 20 minutes using a V-blender, and sieved with a sieve having a 177 μm mesh to obtain a developer.

[Comparative Example 1]
A developer was obtained in the same manner as in Example 1, except that the silica external additive (1) was not used.

[Comparative Example 2]
A developer was obtained in the same manner as in Example 1, except that the silica external additive (5) was used instead of the silica external additive (1).

[Comparative Example 3]
A developer was obtained in the same manner as in Example 1 except that the silica external additive (6) was used instead of the silica external additive (1).

[Comparative Example 4]
A developer was obtained in the same manner as in Example 1, except that the silica external additive (7) was used instead of the silica external additive (1).

[Comparative Example 5]
A developer was obtained in the same manner as in Example 1 except that the silica external additive (8) was used instead of the silica external additive (1).

(Evaluation)
Using an image forming apparatus (manufactured by Fuji Xerox Co., Ltd., Docu Center Color 320 modified machine), image forming tests were performed with the developers of Examples 1 to 6 and Comparative Examples 1 to 5.
Specifically, after the apparatus is first left and left in an environment of 30 ° C. and 75% for a day and night, each developer is set in the Color (Yellow, Magenta or Cyan) position in an environment of 10 ° C. and 10%. A Kuro developer for Center Color 320 was set.
Subsequently, after outputting 100 images with an image density of 5% Kuro to A4 paper (P paper, manufactured by Fuji Xerox Co., Ltd.), one image with 100% image density and 0% image with a color developer each time. One sheet with a density was continuously output on A4 paper. At that time, the image surface (striped stain) and the scratches on the surface of the image carrier (image carrier corresponding to the color of the developer used) were evaluated. Tables 1 and 2 show the results of repeating the formation and evaluation of 100 black-and-white images and two color images.

The image quality and image carrier damage evaluation methods and evaluation criteria shown in Tables 1 and 2 are as follows.
<Evaluation of scratches on image carrier (image carrier)>
Image carrier scratches were evaluated by visually observing the surface of a color image carrier on which a color developer was set every time 100 images were formed with a 5% Kuro color image density. Existence and degree were evaluated according to the following criteria.
A: Almost no streak can be confirmed even on the 2000th sheet.
Δ: Some streak-like scratches are seen on the 1500th sheet, but there is no practical problem.
X: Streak-like scratches are uniformly confirmed on the entire surface at the 1000th sheet or less.

<Evaluation of image quality>
The evaluation of image quality is based on the output color (cyan, magenta, or yellow) using a color image carrier in which a color developer is set each time 100 images are formed with an image density of 5% Kuro. A color image having a 100% image density was checked for the presence or absence of streak stains on the image, and evaluated according to the following criteria.
At a Kuro color 5% image density, no streak occurs even on the 2000th sheet.
Δ: Streaky stains occurred on the 1500th sheet.
X: Streaks were generated on the 1000th sheet or less.

As can be seen from Table 1, in Examples 1 to 6, the image quality and the evaluation of the image carrier scratch were good. In addition, when the silica external additive of the present invention was used for a small-diameter toner that was harder to clean (Example 5), the image carrier was slightly scratched, but at a practically satisfactory level. Even in the case of a small-diameter toner, when the cerium oxide was used in combination with the silica external additive of the present invention, the image quality and image carrier damage were evaluated well. Further, with respect to Examples 1 to 5, evaluation was further performed up to the 3000th sheet. However, although Examples 2 and 5 had some streak stains, Examples 1 and 6 did not cause streak stains. In Example 6, streak stains did not occur even on the 4000th sheet.
On the other hand, in Comparative Examples 1 and 2, the amount of the specific external additive supplied to the contact portion between the image carrier and the blade is small, a cleaning failure occurs from the initial stage of image formation, and the image quality deteriorates at the 1000th sheet. (Streak, comet) and image carrier scratches were confirmed. Further, in Comparative Examples 3 to 5, a toner (external additive) cleaning failure occurred over time, and image quality deterioration (streaks scratches) and image carrier scratches were confirmed at 1500 sheets.

Claims (5)

  A silica having a number average particle size in the range of 100 to 150 nm, a standard deviation in the number particle size distribution exceeding 0.77 times the number average particle size, and a true specific gravity of 1.9 or less. A featured external additive for toner.   A toner for electrostatic charge development, wherein the external additive for toner according to claim 1 is externally added.   The electrostatic charge developing toner according to claim 2, wherein cerium oxide is externally added.   An electrostatic charge developing developer comprising the electrostatic charge developing toner according to claim 2.   An electrostatic latent image forming step for forming an electrostatic latent image on the surface of the image carrier, and the electrostatic latent image is developed by the electrostatic charge developing developer according to claim 4 so as to form a surface on the surface of the image carrier. A developing step for forming a toner image, a transfer step for transferring the toner image from the surface of the image carrier to a recording medium, and a surface of the image carrier after the toner image is transferred by a cleaning blade that abuts the surface. An image forming method comprising: a cleaning step of cleaning; and a fixing step of fixing the transferred toner image to the recording medium.