JP4142681B2 - Image forming method, image forming apparatus, and toner used in the same - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming method and an image forming apparatus such as a copying machine, a printer, and a facsimile using a dry two-component developer, and a toner applied to these, in particular, a spherical toner and the spherical toner. The present invention relates to an image forming method and an image forming apparatus capable of avoiding abnormal images and image quality degradation when using the image forming apparatus.

In recent electrophotographic image forming apparatuses such as copying machines, printers, facsimiles, and the like using a dry two-component developer or a one-component developer, a series of charging, exposure, development, transfer, and cleaning is performed when obtaining a multicolor image. A method of repeating the process and sequentially superimposing color images for each color is well known. However, for example, when a multicolor image is formed on an image carrier or a transfer target, a large amount of toner can be carried, but on the other hand, there is a problem that the outer shape of the apparatus becomes very large. It was.
Therefore, as a countermeasure for the above-mentioned problem, the size of the apparatus has been reduced by using a flexible belt-shaped transfer member, and many multicolor image forming apparatuses have already been put on the market. However, there is a demand for further improving the image quality of the multicolor image and maintaining higher gradation and resolution. For example, a high resolution image having a resolution of 1200 dpi or higher is being studied.

Therefore, in order to realize high resolution, a higher-definition multicolor image forming method than before is desired. For toners and developers that visualize latent images, further spheroidization and smaller particle diameters are being studied and realized in order to form high-definition images.
For example, spherical toners having a specific particle size distribution have been proposed (see, for example, Patent Documents 1, 2, 3, and 4), and toners using various polymerization methods have been proposed (Patent Documents 5, 6, and 6). 7, 8). As the toner, a polymerized toner by a suspension polymerization method or a dispersion polymerization method or a toner subjected to a spherical treatment by a hot air flow or a fluidized granulation method is being used, and has excellent fluidity and image forming ability. Has attracted attention as a toner.

  Spherical toner has better transfer efficiency than irregular toner, and if the transfer efficiency is further improved to reduce the amount of residual toner on the image carrier, the occurrence of defective cleaning is suppressed. In order to suppress this, measures to improve transfer efficiency are effective. Further, when the transfer efficiency is improved, the amount of toner collected by cleaning is reduced, so that the improvement of transfer efficiency is also effective for the environment. Further, an image forming apparatus that recycles the toner collected by cleaning by providing a recycling mechanism, or a toner that remains after transfer in a process of charging the image carrier without developing a cleaning means or a step of developing the toner on the image carrier. Even in a cleanerless type image forming apparatus that collects toner, the characteristics of the toner collected due to various stresses are often changed with respect to normal toner, so image defects due to the collected toner are likely to occur. Since the occurrence of image defects can be suppressed as the amount of collected toner is smaller, further improvement in transfer efficiency is required.

As a measure for increasing the transfer efficiency, a technique for providing means for reducing the adhesion between the image carrier and the toner is disclosed.
For example, a method of applying fine particles having a particle diameter smaller than that of toner on an image carrier has been proposed (see Patent Documents 9, 10, 11, and 12). Further, a method has been proposed in which fine particles externally added to the toner are adhered to the image carrier (see Patent Documents 13, 14, 15, and 16). The fine particles adhering to the image carrier reduce the contact area between the image carrier and the toner, the adhesion force between the image carrier and the toner is reduced, and the toner attached to the surface of the image carrier is easily transferred. Efficiency is improved.

However, in the method as described above, it is difficult to uniformly apply fine particles on the image carrier, and uneven density of the image due to fine particle density unevenness is likely to occur. The fine particles applied to the image carrier are cleaned, etc. The image carrier is liable to be damaged due to the stress of the image, and the fine particles peeled off from the image carrier adhere to the toner or the carrier to change the chargeability and fluidity, thereby causing the development and transfer failure. There is a problem.
The transfer process is a process in which the toner is moved from the image carrier onto the transfer body by an electrostatic force due to an electric field, and the transfer characteristics are determined by the relationship between the adhesion force of the toner and the electrostatic force due to the electric field. Adhesive force control is an important factor in transfer design.
In particular, when roller transfer or belt transfer is used, when the toner image on the image carrier is pressed against the transfer member, the toner is pressed onto the image carrier due to a reaction, so that the toner and the image carrier are not pressed. The adhesion force between the toner particles and the toner particles increases, and a phenomenon occurs in which a part of the toner layer remains on the image carrier without being transferred to the transfer member. This phenomenon is particularly likely to occur at the center of the thin line portion where pressure is easily applied, and a so-called hollow character phenomenon called a hollow character occurs.

For this reason, in order to improve the void in the image, the adhesion force between the toner and the image carrier and the adhesion force between the toner particles and the toner particles or between the image carrier and the transfer member are applied. It is necessary to reduce the pressure. The adhesion force between the toner and the image carrier is classified into electrostatic adhesion force caused by toner charging and other non-electrostatic adhesion force caused by van der Waals force, liquid crosslinking force, intermolecular force, etc. However, the electrostatic adhesion force depends on the charge amount of the toner, and can be reduced by lowering the charge amount. However, if the charge amount of the toner is too small, there arises a problem that the toner cannot be transferred by electrostatic force due to an electric field.
Several reports on toner adhesion are also disclosed (see, for example, Patent Documents 17, 18, and 19). However, in the above report example, the toner adhesion force is not classified into electrostatic adhesion force and non-electrostatic adhesion force. In addition, there is an example in which the relationship between the non-electrostatic adhesion force of the toner and the image quality is examined, and the non-electrostatic adhesion force of the toner is regulated to a predetermined value or less (see Patent Document 20). However, although the non-electrostatic adhesion force of the toner changes depending on the particle size of the toner, the above example does not mention the relationship between the non-electrostatic adhesion force and the toner particle size.

  On the other hand, a technique is disclosed in which the thickness of the toner layer on the transfer belt when three colors are superimposed (hereinafter referred to as toner pile height) is specified to be 280 μm or less (see Patent Document 21). It seems that the toner pigment concentration and the above pile height were calculated from the viewpoint of gradation, but Patent Document 21 describes the shape, average particle size, fluidity, or aggregation degree of the toner that is the main factor for controlling the pile height with respect to this value. In addition, according to the above regulations, it is determined that the pile height for each color is 90 μm or more based on the simple calculation and is not a realistic measure from the fact that the current electrophotographic image is configured with a toner amount that cannot be considered. Is done.

Japanese Patent Laid-Open No. 1-112253 JP-A-2-284158 Japanese Patent Laid-Open No. 3-181952 JP-A-4-162048 Japanese Patent Laid-Open No. 5-072808 Japanese Patent Laid-Open No. 5-188642 Japanese Unexamined Patent Publication No. 6-074429 JP-A-8-160661 Japanese Patent Laid-Open No. 10-73992 JP-A-10-207098 Japanese Patent Laid-Open No. 11-45011 JP 2000-89587 A Japanese Patent Laid-Open No. 10-161425 JP 2000-89548 A JP 2000-89587 A JP 2000-292966 A JP-A-5-333757 JP-A-6-167825 JP-A-6-167826 JP-A-8-305075 JP-A-8-190240

The present invention has been made in view of the above problems, and an object of the present invention is to transfer dust and a hollow image when a spherical toner is used in an image forming method and an image forming apparatus using a two-component developer. High-definition image formation without the occurrence of abnormal images such as, and more, the use efficiency of the toner in the transfer process, excellent transferability, less waste toner than conventional, environmentally friendly image forming method And an image forming apparatus and a toner applied to the image forming apparatus.

In the image forming method and the image forming apparatus using spherical toner, the present inventors formed an image in consideration of the relationship between the toner pile height carried on the developed image carrier and the applied toner particle size. As a result, the inventors have found that the above-described object can be achieved, and further confirmed that this effect is particularly remarkable in a spherical toner produced by the production method described later.
That is, the image forming method according to the present invention includes a latent image forming step of forming an electrostatic latent image on the first image carrier, and developing the formed electrostatic latent image using a developer corresponding to a color image. Then, the developing step for forming a monochromatic toner image and the first transfer step for transferring the toner image formed on the first image carrier onto the second image carrier are repeated a plurality of times, and the second image A color image formed by laminating a single color toner image on the carrier is formed, and then a second transfer step for transferring the color image formed on the second image carrier to the recording medium, and the color image transferred to the recording medium. And a fixing step of fixing a color image on the recording medium by heating and / or pressurizing, wherein the developer is a two-component developer having a toner and a carrier, and the two-component developer The toner particles contained in the toner have a volume average particle size of 1 to 8 m, the average degree of circularity of 0.92 to 0.99, a loose apparent density was 0.5 g / cm ³ or more, the thickness of the toner layer formed on the first image bearing member, the volume of the toner particles The average particle diameter is 3 times or less, and the thickness of the color image toner layer formed on the second image carrier is 5.41 times or less the volume average particle diameter of the toner particles. And

In this case, the true specific gravity of the toner is 1.2 to 1.5 g / cm ³ , and the toner particles contain 0.01 to 5 wt% of inorganic fine particles having a primary particle diameter of 5 nm to 2 μm. It is preferable.
The inorganic fine particles include small-sized inorganic fine particles whose primary particles have a volume average particle size of 5 nm to 80 nm and large-sized inorganic fine particles whose primary particles have a volume average particle size of 80 nm to 200 nm. Is preferred.
Furthermore, the small particle size inorganic fine particles can be slid with a mixture of two or more selected from silica, titanium oxide, and alumina.
Furthermore, the inorganic fine particles may be hydrophobic inorganic fine particles surface-treated with silicone oil or a silicone coupling agent, and the hydrophobic degree of hydrophobic inorganic fine particles may be 50% or more.
Furthermore, the toner particles may be obtained by dissolving or dispersing a toner composition containing a resin and a colorant in an organic solvent, and then dissolving the resulting solution or dispersion in an aqueous medium in the presence of an inorganic dispersant or a fine particle polymer. It can be manufactured by dispersing and subjecting the dissolved product or dispersion to a polyaddition reaction and removing the solvent from the resulting emulsified dispersion.
Furthermore, the resin is a polyester resin, preferably having a number average molecular weight of 2000 to 15000, a glass transition point of 55 to 75 ° C., and an acid value of 1 to 30 mgKOH / g.
Furthermore, the polyester resin may contain a modified polyester having a urea bond.
Furthermore, the polyester resin may contain an alkylene oxide adduct of bisphenols as a polyol component.
Furthermore, the toner particles may contain a wax as a release agent.

  According to the present invention, an abnormal image such as transfer dust or a hollow image is not generated, and a high-definition image can be formed stably with high transfer efficiency, environmentally friendly, and stably for a long time.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to the present invention. The image forming apparatus in FIG. 1 is a revolver developing multicolor image forming apparatus. However, the present invention is not limited to this, and a dry two-component developer is used and the following image forming method is adopted. It can be applied to any image forming apparatus. In the image forming method according to the present invention, at least the step of forming a toner image on the first image carrier and transferring the toner image onto the second image carrier is repeated a plurality of times, and then the second image carrier. This is an image forming method in which a multicolor toner layer formed thereon is collectively transferred onto a transfer medium by a transfer means.
The first image carrier is the electrophotographic photoreceptor 1 in the development process, and the second image carrier is the intermediate transfer body 3 in the transfer process. The intermediate transfer body 3 has a configuration in which a belt-like elastic body is stretched around a roller, so that the layout of the apparatus becomes free and the apparatus can be miniaturized.
After the surface of the electrophotographic photosensitive member 1 is uniformly charged by the charging device 4, it is irradiated with exposure light 5 to write an electrostatic latent image. The electrostatic latent image is developed by a developing device 2 as developing means to form a toner image. The process of transferring the toner image to the intermediate transfer body 3 is repeated to form a multicolor toner layer on the intermediate transfer body 3, and batch transfer onto a recording medium such as a sheet to be transferred that has been conveyed from the paper feed cassette To do.

In the present invention, as the toner used for the two-component developer, toner that has been spheroidized in the manufacturing process or in the post-manufacturing process is used. The pile height of the toner layer formed on the electrophotographic photoreceptor 1 is not more than 3 times the volume average particle diameter of the toner particles, and the pile height of the multicolor toner layer transferred onto the intermediate transfer body 3 is the toner particles. It is characterized by being 10 times or less of the volume average particle size.
Several methods can be considered for evaluating the toner pile height. In this embodiment, an ultra-deep microscope measurement system VK-8500 (manufactured by Keyence Corporation) is used, and all patterns such as solid, line, and dot images are displayed. The toner pile height was measured, and the above relationship was found from the statistical average value.
When the toner pile height on the photoconductor 1 is larger than 3 times the toner particle volume average particle size, dust or background dirt toner increases from the image on the photoconductor 1. Further, when the toner pile height on which the multicolor toner on the intermediate transfer member 3 is superimposed is larger than 10 times the volume average particle diameter of the toner particles, dust and void images at the time of transfer tend to appear. These causes are relatively easy to understand. That is, when the toner pile height is extremely high, the electrostatic force applied to the upper toner particles is weakened, so that the binding force on the toner particles is weakened, and it is estimated that dust is generated. Furthermore, in the case of a hollow image (hollow character) that occurs in a thin line or the like, the pressure on the image center in the transfer nip locally increases with an increase in pile height, and only the toner particles in the image center are compressed, Since the packing state between the toners is remarkably different between the central portion and the peripheral portion of the image, there is a difference in height in the adhesion energy between the toner and the photosensitive member in one image, and only the central toner is transferred to the photosensitive member at the time of transfer. It is estimated that it will become difficult to leave and become an abnormal image.

  The average circularity of the toner particles is 0.92 to 0.99, preferably 0.95 to 0.99. The circularity of the toner can be obtained, for example, by passing a suspension containing particles through an imaging unit detection zone on a flat plate and optically detecting and analyzing the particle image with a CCD camera. The average circularity can be calculated by dividing the circumference of a circle equal to the projected area obtained by this method by the circumference of the actual particle. When the circularity is smaller than the above circularity, the characteristics are the same as those of the irregular shaped toner produced by the pulverization method. When the toner image is formed, the pile height has the above thickness or more, and the transferability is remarkably high. Getting worse. Further, when the circularity is higher than the above circularity, the transferability is hardly changed, but the cleaning property of the residual toner is remarkably deteriorated, resulting in poor cleaning, and the toner is fixed on the photosensitive member 1 or the intermediate transfer member 3, Other abnormal images such as black streaks occur.

In order to assist fluidity and chargeability, it is preferable to add inorganic fine particles whose primary particles have a volume average particle diameter of 5 nm to 2 μm to the toner. A more preferable range of the primary particle volume average particle diameter of the inorganic fine particles is 5 nm to 500 nm. At this time loose apparent density of toner is set to 0.5 g / cm ³ or more, a true specific gravity is preferably in the range of 1.2~1.5g / cm ^3. The loose apparent density is a measure of fluidity between toner particles, and can be measured by a method defined in JIS R 1628. Moreover, it is preferable that the specific surface area by BET method of an inorganic fine particle is 20-500 m < ² > / g. The addition ratio of the inorganic fine particles is 0.01 to 5.0 wt% of the toner, and more preferably 0.01 to 2.0 wt%. If it is less than 0.01 wt%, satisfactory fluidity cannot be obtained, and if it exceeds 5 wt%, the external additive is easily released from the toner.

FIG. 2 shows the result of confirming the correlation between the total amount of external additives (indicated by weight ratio with respect to the toner) and the loose apparent density. FIG. 2 (b) is an enlarged view of a portion with a small addition amount in FIG. 2 (a). This measurement is the result of measuring an irregularly shaped toner (hereinafter referred to as a pulverized toner) produced by a normal pulverization method and a spherical toner obtained by thermally spheroidizing the pulverized toner. It can be considered that there is almost no difference in material and structure between them, and it is considered that the difference due to the difference in the shape of the toner is simply expressed.
As is apparent from FIG. 2, spherical toner has a large friction between toners when the amount of external additive added is very small, and the bulk density is lower than that of pulverized toner. Density tends to increase. This indicates that spherical toner has the characteristic of exhibiting very high fluidity by the addition of a small amount of external additives, but on the contrary, it is subjected to mechanical or electrical stress over a long period of time such as stirring in the actual machine. This suggests that the flowability deteriorates suddenly when a change occurs such that the external additive on the toner surface is buried in the toner.

Therefore, as the inorganic fine particles as the external additive, the primary particle has a volume average particle size of 5 nm to 80 nm, a small particle size inorganic fine particle, and the primary particle has a volume average particle size of 80 nm to 200 nm. Together with. This makes it difficult for the external additive to be buried and suppresses a rapid deterioration of the fluidity of the spherical toner. This is because the large particle size inorganic fine particles absorb external stress and as a result control the embedding of the small particle size inorganic fine particles that promote the fluidity of the toner.
When the inorganic fine particles having a small particle diameter are used by mixing at least two kinds of silica, titanium oxide and alumina, it is possible to control environmental stability and chargeability. In particular, when stirring and mixing are performed using inorganic fine particles having an average particle size of 50 nm or less, the electrostatic force and van der Waals force with the toner are remarkably improved, so as to obtain a desired charge level. Even when the mixing and stirring is performed inside the developing machine, the fluidity imparting agent is not detached from the toner, a good image quality in which fireflies are not generated can be obtained, and the residual toner can be further reduced.

In particular, hydrophobic silica fine particles surface-treated with silicone oil or silicone coupling agent and hydrophobic titanium oxide fine particles are used in combination, and the addition amount is in the range of 0.3 to 1.5 wt% of the toner. The effect of the present invention is great when the hydrophobicity of the hydrophobic inorganic fine particles is 50% or more. Details of the degree of hydrophobicity will be described later.
Titanium oxide fine particles are excellent in environmental stability and image density stability, but have a tendency to deteriorate the charge rise characteristics. Therefore, if the amount of titanium oxide fine particles added is larger than the amount of silica fine particles added, this side effect is affected. It can be considered large. However, when the addition amount of the hydrophobic silica fine particles and the hydrophobic titanium oxide fine particles is in the range of 0.3 to 1.5 wt%, the charge rising characteristics are not greatly impaired, and the desired charge rising characteristics can be obtained, that is, the copying can be repeated. Even if it is performed, stable image quality can be obtained and toner blowing can be suppressed.

The main purpose of hydrophobizing the inorganic fine particles used as the external additive is to suppress the hygroscopicity of the inorganic fine particles and increase the weather resistance of the toner particles in view of use under high humidity.
Specific treatment methods for the hydrophobic treatment include, for example, known silane coupling agents such as dialkyl dihalogenated silane, trialkyl halogenated silane, and alkyl trihalogenated silane, and known silicone oil typified by dimethyl silicone oil. And the above-mentioned inorganic fine particles are contact-reacted at a high temperature.
In the present embodiment, the guideline of the degree of hydrophobicity is used as a guideline for the above-described hydrophobizing treatment, but this is obtained by the following method. 0.4 g of the above inorganic fine particles are added to 100 ml of water, stirred with a stirrer, etc., and then titrated with methanol. When the amount of methanol dropped at the time when all of the inorganic fine particles are suspended in the aqueous solution is Tml, it is expressed by the following formula.
Hydrophobic degree = [T / (T + 100)] × 100 (%)
When the degree of hydrophobicity is less than 50%, the inorganic fine particles have high hygroscopicity and are easily affected by humidity, etc., and water molecules are adsorbed to the inorganic fine particles and liquid is brought into contact with each other or with the carrier. Since the cross-linking is formed and the fluidity is remarkably deteriorated, the function as a developer is not achieved.

The spherical toner is manufactured as follows, for example. That is, in the spherical toner, a toner composition comprising at least a resin and a colorant is dissolved or dispersed in an organic solvent, and the resulting solution or dispersion is dispersed in an aqueous medium in the presence of an inorganic dispersant or fine particle polymer. And the resulting dissolved or dispersed product is reacted with an amine to cause a polyaddition reaction, and the solvent of the resulting emulsified dispersion is removed.
Specifically, a toner composition containing, for example, a polyester resin reacted with a polyvalent isocyanate is dispersed in an organic medium, and the resulting dissolved or dispersed material is dispersed in an aqueous medium in the presence of an inorganic dispersant or fine particle polymer. It is prepared by an emulsion polymerization method in which an amine is added, an isocyanate group-containing prepolymer is subjected to an extension reaction and / or a crosslinking reaction with the amine, and the solvent is removed from the obtained emulsion dispersion. Although the toner obtained by the emulsion polymerization method is a spherical toner having a high average circularity, the toner is significantly more miscible with the carrier than the spherical toner produced by the conventional polymerization method.
The polyester resin contained in the toner contains a modified polyester having a number average molecular weight of 2000 to 15000, a glass transition point of 55 to 75 ° C., an acid value of 1 to 30 mgKOH / g, and a urea bond. As a polyol component of the polyester resin, an alkylene oxide adduct of bisphenols is contained. The glass transition point (Tg) is preferably 55 to 65 ° C. If the temperature is less than 55 ° C., the heat-resistant storage stability of the toner deteriorates, and if it exceeds 75 ° C., the low-temperature fixability becomes insufficient. Further, by containing a urea-modified polyester resin, the heat resistant storage stability tends to be good even when the glass transition point is low, as compared with known polyester toners.

The toner may contain a wax as a release agent.
As the wax, a low melting point having a melting point of 50 to 120 ° C. works more effectively as a release agent in the dispersion with the binder resin between the fixing roller and the toner interface. It shows an effect on high temperature offset without applying a mold release agent. In this embodiment, the melting point of the wax is the maximum endothermic peak measured by a differential operation calorimeter (DSC).
Examples of such a wax component include the following. Examples of waxes and waxes include plant waxes such as carnauba wax, cotton wax, wood wax and rice wax, animal waxes such as beeswax and lanolin, mineral waxes such as ozokerite and cercin, and paraffin, microcrystalline and petrolatum. And petroleum wax. In addition to these natural waxes, synthetic hydrocarbon waxes such as Fischer-Tropsch wax and polyethylene wax, and synthetic waxes such as esters, ketones, and ethers can be used. Furthermore, fatty acid amides such as 12-hydroxystearic acid amide, stearic acid amide, phthalic anhydride imide, chlorinated hydrocarbon, and low molecular weight crystalline polymer resin, poly-n-stearyl methacrylate, poly-n- A crystalline polymer having a long alkyl group in the side chain, such as a homopolymer or copolymer of polyacrylate such as lauryl methacrylate (for example, a copolymer of n-stearyl acrylate-ethyl methacrylate, etc.) can also be used. .

  The direct reason why the toner particles produced by the above method showed a good result when the relationship between the toner pile height and the average particle diameter was maintained is not clear. However, in general, the spherical toner has a larger effective contact area with other members than the irregular toner. This is because the point contact is in the case of an indeterminate shape and the surface contact is in the case of a spherical shape. The toner charge typified by van der Waals force is proportional to the contact area, but spherical toner has a higher non-electrostatic adhesion force that is not caused by the charge, and this effect is thought to reduce the fluidity of the developer. It is done.

  The volume average particle diameter of the toner particles is 1 to 8 μm. If the particle size of the toner particles is out of the above range, the intended purpose may not be achieved even if the relationship between the pile height and the average particle size described above is satisfied. The carrier particles constituting the developer preferably have a volume average particle size of less than 60 μm. In this case, good results are obtained.

Hereinafter, specific components of the toner and a manufacturing method thereof will be described.
Polyester as a resin that is a constituent component of the toner is obtained by a polycondensation reaction between a polyhydric alcohol compound and a polycarboxylic acid compound.
Examples of the polyhydric alcohol compound (PO) include dihydric alcohol (DIO) and trihydric or higher polyhydric alcohol (TO), and DIO alone or a mixture of DIO and a small amount of TO is preferable. Examples of the dihydric alcohol (DIO) include alkylene glycol (ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, etc.); alkylene ether glycol (diethylene glycol) , Triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, etc.); alicyclic diols (1,4-cyclohexanedimethanol, hydrogenated bisphenol A, etc.); bisphenols (bisphenol A, bisphenol) F, bisphenol S, etc.); alkylene oxide (ethylene oxide, propylene oxide, butylene oxide, etc.) adduct of the above alicyclic diol; Alkylene oxide bisphenol (ethylene oxide, propylene oxide, butylene oxide, etc.), etc. adducts. Among them, preferred are alkylene glycols having 2 to 12 carbon atoms and alkylene oxide adducts of bisphenols, and particularly preferred are alkylene oxide adducts of bisphenols and alkylene glycols having 2 to 12 carbon atoms. It is a combined use. The trihydric or higher polyhydric alcohol (TO) includes 3 to 8 or higher polyhydric aliphatic alcohols (glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, sorbitol, etc.); trihydric or higher phenols (Trisphenol PA, phenol novolak, cresol novolak, etc.); and alkylene oxide adducts of the above trivalent or higher polyphenols.

  Examples of the polyvalent carboxylic acid (PC) include divalent carboxylic acid (DIC) and trivalent or higher polyvalent carboxylic acid (TC), and DIC alone or a mixture of DIC and a small amount of TC is preferable. Divalent carboxylic acids (DIC) include alkylene dicarboxylic acids (succinic acid, adipic acid, sebacic acid, etc.); alkenylene dicarboxylic acids (maleic acid, fumaric acid, etc.); aromatic dicarboxylic acids (phthalic acid, isophthalic acid, terephthalic acid) And naphthalenedicarboxylic acid). Of these, preferred are alkenylene dicarboxylic acids having 4 to 20 carbon atoms and aromatic dicarboxylic acids having 8 to 20 carbon atoms. Examples of the trivalent or higher polyvalent carboxylic acid (TC) include aromatic polycarboxylic acids having 9 to 20 carbon atoms (such as trimellitic acid and pyromellitic acid). In addition, as polyhydric carboxylic acid (PC), you may make it react with polyhydric alcohol (PO) using the above-mentioned acid anhydride or lower alkyl ester (Methyl ester, ethyl ester, isopropyl ester, etc.).

The ratio of the polyhydric alcohol (PO) to the polycarboxylic acid (PC) is usually 2/1 to 1/1, preferably as the equivalent ratio [OH] / [COOH] of the hydroxyl group [OH] and the carboxyl group [COOH]. Is 1.5 / 1 to 1/1, more preferably 1.3 / 1 to 1.02 / 1.
The hydroxyl value of the polyester obtained by the polycondensation reaction of the polyhydric alcohol (PO) and the polyvalent carboxylic acid (PC) is preferably 5 or more, and the acid value of the polyester is usually 1 to 30, preferably 5 to 20. It is. By giving an acid value, it tends to be negatively charged, and furthermore, when fixing to a recording paper, the affinity between the recording paper and the toner is good and the low-temperature fixability is improved. When the acid value exceeds 30, there is a tendency to deteriorate with respect to the stability of charging, particularly environmental fluctuation.

In addition to the unmodified polyester obtained by the above polycondensation reaction, the polyester preferably contains a urea-modified polyester. The urea-modified polyester is obtained by reacting the terminal carboxyl group or hydroxyl group of the polyester obtained by the above polycondensation reaction with a polyvalent isocyanate compound (PIC) to obtain a polyester prepolymer (A) having an isocyanate group. It is obtained by cross-linking and / or extending the molecular chain by the reaction of amide with amines.
Examples of the polyvalent isocyanate compound (PIC) include aliphatic polyisocyanates (tetramethylene diisocyanate, hexamethylene diisocyanate, 2,6-diisocyanatomethylcaproate, etc.); alicyclic polyisocyanates (isophorone diisocyanate, cyclohexylmethane diisocyanate, etc.) Aromatic diisocyanates (tolylene diisocyanate, diphenylmethane diisocyanate, etc.); araliphatic diisocyanates (α, α, α ′, α′-tetramethylxylylene diisocyanate, etc.); isocyanates; Those blocked with caprolactam or the like; and combinations of two or more of these.

The ratio of the polyvalent isocyanate compound (PIC) is usually 5/1 to 1/1, preferably as an equivalent ratio [NCO] / [OH] of the isocyanate group [NCO] and the hydroxyl group [OH] of the polyester having a hydroxyl group. 4/1 to 1.2 / 1, more preferably 2.5 / 1 to 1.5 / 1. When [NCO] / [OH] exceeds 5, low-temperature fixability deteriorates. When the molar ratio of [NCO] is less than 1, when a urea-modified polyester is used, the urea content in the ester is lowered and hot offset resistance is deteriorated.
The content of the polyvalent isocyanate compound (PIC) component in the polyester prepolymer (A) having an isocyanate group is usually 0.5 to 40 wt%, preferably 1 to 30 wt%, more preferably 2 to 20 wt%. . If it is less than 0.5 wt%, the hot offset resistance deteriorates, and it is disadvantageous in terms of both heat-resistant storage stability and low-temperature fixability. On the other hand, if it exceeds 40 wt%, the low-temperature fixability deteriorates.
The number of isocyanate groups contained per molecule in the polyester prepolymer (A) having an isocyanate group is usually 1 or more, preferably 1.5 to 3 on average, more preferably 1.8 to 2 on average. Five. If it is less than 1 per molecule, the molecular weight of the urea-modified polyester will be low, and the hot offset resistance will deteriorate.

Next, as amines (B) to be reacted with the polyester prepolymer (A), a divalent amine compound (B1), a trivalent or higher polyvalent amine compound (B2), an amino alcohol (B3), an amino mercaptan (B4) ), Amino acid (B5), and amino acid block of B1 to B5 (B6).
Examples of the divalent amine compound (B1) include aromatic diamines (phenylenediamine, diethyltoluenediamine, 4,4′-diaminodiphenylmethane, etc.); alicyclic diamines (4,4′-diamino-3,3′-dimethyldicyclohexyl). Methane, diamine cyclohexane, isophorone diamine, etc.); and aliphatic diamines (ethylene diamine, tetramethylene diamine, hexamethylene diamine, etc.) and the like. Examples of the trivalent or higher polyvalent amine compound (B2) include diethylenetriamine and triethylenetetramine. Examples of amino alcohol (B3) include ethanolamine and hydroxyethylaniline. Examples of amino mercaptan (B4) include aminoethyl mercaptan and aminopropyl mercaptan. Examples of the amino acid (B5) include aminopropionic acid and aminocaproic acid. Examples of the compound (B6) obtained by blocking the amino group of B1 to B5 include ketimine compounds and oxazolidine compounds obtained from the amines of B1 to B5 and ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.). Among these amines (B), preferred are B1 and a mixture of B1 and a small amount of B2.

The ratio of amines (B) is equivalent to the equivalent ratio [NCO] / [NHx] of isocyanate groups [NCO] in the polyester prepolymer (A) having isocyanate groups and amino groups [NHx] in amines (B). Is usually 1/2 to 2/1, preferably 1.5 / 1 to 1 / 1.5, more preferably 1.2 / 1 to 1 / 1.2. When [NCO] / [NHx] is more than 2 or less than 1/2, the molecular weight of the urea-modified polyester is lowered, and the hot offset resistance is deteriorated.
The urea-modified polyester may contain a urethane bond together with a urea bond. The molar ratio of the urea bond content to the urethane bond content is usually 100/0 to 10/90, preferably 80/20 to 20/80, and more preferably 60/40 to 30/70. When the molar ratio of the urea bond is less than 10%, the hot offset resistance is deteriorated.

The urea-modified polyester is produced by a one-shot method or the like. Polyhydric alcohol (PO) and polyvalent carboxylic acid (PC) are heated to 150-280 ° C. in the presence of a known esterification catalyst such as tetrabutoxytitanate, dibutyltin oxide, etc., and water generated while reducing the pressure as necessary. Distill off to obtain a polyester having a hydroxyl group. Subsequently, at 40-140 degreeC, this is made to react with polyvalent isocyanate (PIC), and the polyester prepolymer (A) which has an isocyanate group is obtained. Further, this (A) is reacted with amines (B) at 0 to 140 ° C. to obtain a urea-modified polyester.
When reacting PIC and when reacting the polyester prepolymer (A) having an isocyanate group and the amines (B), a solvent may be used as necessary. Usable solvents include aromatic solvents (toluene, xylene, etc.); ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.); esters (ethyl acetate, etc.); amides (dimethylformamide, dimethylacetamide, etc.) and ethers And those inert to isocyanates (PIC) such as tetrahydrofuran (such as tetrahydrofuran).

In addition, in the crosslinking and / or extension reaction between the polyester prepolymer (A) and the amines (B), a reaction terminator may be used as necessary to adjust the molecular weight of the resulting urea-modified polyester. Examples of the reaction terminator include monoamines (diethylamine, dibutylamine, butylamine, laurylamine, etc.), and those obtained by blocking them (ketimine compounds).
The weight average molecular weight of the urea-modified polyester is usually 10,000 or more, preferably 20,000 to 10,000,000, and more preferably 30,000 to 1,000,000. If it is less than 10,000, the hot offset resistance deteriorates. The number average molecular weight of the urea-modified polyester or the like is not particularly limited when the above-mentioned unmodified polyester is used, and may be a number average molecular weight that can be easily obtained to obtain the weight average molecular weight. When the urea-modified polyester is used alone, its number average molecular weight is usually 2000-15000, preferably 2000-10000, more preferably 2000-8000. When the number average molecular weight exceeds 20000, the low-temperature fixability and the gloss when used in a full-color device are deteriorated.

By using the unmodified polyester and the urea-modified polyester in combination, the low-temperature fixability and the glossiness when used in a full-color image forming apparatus are improved. Therefore, it is preferable to use the urea-modified polyester alone. The unmodified polyester may include a polyester modified with a chemical bond other than a urea bond.
The unmodified polyester and the urea-modified polyester are preferably at least partially compatible with each other in terms of low-temperature fixability and hot offset resistance. Therefore, it is preferable that the unmodified polyester and the urea-modified polyester have a similar composition.
The weight ratio of unmodified polyester to urea-modified polyester is usually 20/80 to 95/5, preferably 70/30 to 95/5, more preferably 75/25 to 95/5, particularly preferably 80 /. 20-93 / 7. When the weight ratio of the urea-modified polyester is less than 5%, the hot offset resistance is deteriorated, and it is disadvantageous in terms of both heat-resistant storage stability and low-temperature fixability.

The glass transition point (Tg) of the binder resin containing unmodified polyester and urea-modified polyester is usually 55 to 75 ° C, preferably 55 to 65 ° C. If the temperature is less than 55 ° C., the heat-resistant storage stability of the toner deteriorates, and if it exceeds 75 ° C., the low-temperature fixability becomes insufficient.
In addition, since the urea-modified polyester is likely to be present on the surface of the obtained toner base particles, the heat-resistant storage stability tends to be good even when the glass transition point is low as compared with known polyester-based toners.

Next, the colorant will be described.
As the colorant, all known dyes and pigments can be used. For example, carbon black, nigrosine dye, iron black, naphthol yellow S, Hansa yellow (10G, 5G, G), cadmium yellow, yellow iron oxide, ocher , Yellow lead, titanium yellow, polyazo yellow, oil yellow, Hansa yellow (GR, A, RN, R), pigment yellow L, benzidine yellow (G, GR), permanent yellow (NCG), Vulcan fast yellow (5G, R), Tartrazine Lake, Quinoline Yellow Lake, Anthrazan Yellow BGL, Isoindolinone Yellow, Bengala, Red Dan, Lead Zhu, Cadmium Red, Cadmium Mercury Red, Antimon Zhu, Permanent Red 4R, Para Red, Phi Sayred, Parachlor Ortonito Aniline Red, Resol Fast Scarlet G, Brilliant Fast Scarlet, Brilliant Carmin Min BS, Permanent Red (F2R, F4R, FRL, FRLL, F4RH), Fast Scarlet VD, Belkan Fast Rubin B, Brilliant Scarlet G, Resol Rubin GX, Permanent Red F5R , Brilliant Carmine 6B, Pigment Scarlet 3B, Bordeaux 5B, Toluidine Maroon, Permanent Bordeaux F2K, Helio Bordeaux BL, Bordeaux 10B, Bon Maroon Light, Bon Maroon Medium, Eosin Lake, Rhodamine Lake B, Rhodamine Lake Y, Alizarin Lake, Thio Indigo Red B, Thioindigo Maroon, Oil Red, Quinacridone Red, Pyrazolone Red Polyazo Red, Chrome Vermillion, Benzidine Orange, Perinone Orange, Oil Orange, Cobalt Blue, Cerulean Blue, Alkaline Blue Lake, Peacock Blue Lake, Victoria Blue Lake, Metal Free Phthalocyanine Blue, Phthalocyanine Blue, Fast Sky Blue, Indanthrene Blue (RS, BC), indigo, ultramarine blue, bitumen, anthraquinone blue, fast violet B, methyl violet lake, cobalt purple, manganese purple, dioxane violet, anthraquinone violet, chrome green, zinc green, chromium oxide, pyridian, emerald green, pigment Green B, Naphthol Green B, Green Gold, Acid Green Lake, Malachite Green Lake, Lid Russian nin green, anthraquinone green, titanium oxide, zinc white, litbon and mixtures thereof can be used. The content of the colorant is usually 1 to 15% by weight, preferably 3 to 10% by weight, based on the toner.

The above-mentioned polyester can secure low-temperature fixability of polyester resin as a binder resin and transparency of color toners, and urea-bonded basic molecules have strong dispersion power for pigment dispersion in a solvent, enabling advanced pigment dispersion. I have to. This is due to the action of the basic molecules of the basic polyester having a urea bond both with the pigment-based colorant.
However, the dispersed particle diameter of the pigment-based colorant is further reduced by making the pigment-based colorant a pigment-based dispersant whose dispersion has been increased in advance. That is, by using a master batch obtained by mixing and kneading a pigment-based colorant with a high concentration with respect to the binder resin under a high shearing force, a toner having excellent transparency particularly in a full-color toner can be obtained.
As the binder resin to be kneaded together with the production of the master batch or the master batch, in addition to the above-mentioned unmodified / modified polyester, styrene such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene, and polymers of substituted products thereof; Styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer Styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α- Chloromethyl methacrylate copolymer, Tylene-acrylonitrile copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid Styrene copolymers such as acid ester copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, epoxy resin, epoxy polyol resin, polyurethane, polyamide, polyvinyl butyral, poly Acrylic resin, rosin, modified rosin, terpene resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, paraffin wax and the like can be mentioned, and these can be used alone or in combination.

  In producing the master batch, an organic solvent can be used to enhance the interaction between the colorant and the binder resin. There is also a so-called flushing method in which an aqueous paste containing water of a colorant is kneaded with a resin and an organic solvent, the colorant is transferred to the resin side, and moisture and organic solvent components are removed. Since the cake can be used as it is, it does not need to be dried and is preferably used. For mixing and kneading, a high shearing dispersion device such as a three-roll mill is preferably used.

Next, the charge control agent will be described.
The toner of the present invention may contain a charge control agent as necessary.
Known charge control agents can be used, such as nigrosine dyes, triphenylmethane dyes, chromium-containing metal complex dyes, molybdate chelate pigments, rhodamine dyes, alkoxy amines, quaternary ammonium salts (fluorine-modified quaternary salts). Secondary ammonium salts or compounds, tungsten simple substances or compounds, fluorine-based activators, salicylic acid metal salts, and metal salts of salicylic acid derivatives. Specifically, Nitronine-based dye Bontron 03, quaternary ammonium salt Bontron P-51, metal-containing azo dye Bontron S-34, oxynaphthoic acid metal complex E-82, salicylic acid metal complex E- 84, E-89 of a phenol-based condensate (manufactured by Orient Chemical Industry Co., Ltd.), TP-302 of a quaternary ammonium salt molybdenum complex, TP-415 (manufactured by Hodogaya Chemical Industry Co., Ltd.), quaternary ammonium Copy charge PSY VP2038 of salt, copy blue PR of triphenylmethane derivative, copy charge of quaternary ammonium salt NEG VP2036, copy charge NX VP434 (manufactured by Hoechst), LRA-901, LR-147 which is a boron complex (Nippon Carlit), copper phthalocyanine, perylene, quinacridone Azo pigments, sulfonate group, a carboxyl group include compounds of polymers having a functional group such as quaternary ammonium salts. In addition, since the toner in the present invention is used as a color toner, it is preferable that the charge control agent itself is colorless or single color and does not cause a color tone trouble to the toner.
The amount of charge control agent used in the toner in the present invention is determined by the type of binder resin, the presence or absence of additives used as necessary, and the toner production method including the dispersion method. Although it is not limited to this, Preferably it is used in 0.1-10 weight part with respect to 100 weight part of binder resin, More preferably, the range of 0.2-5 weight part is good. When the amount exceeds 10 parts by weight, the chargeability of the toner is too high, the effect of the main charge control agent is reduced, the electrostatic attractive force with the developing roller is increased, the flowability of the developer is reduced, and the image density is reduced. Incurs a decline. These charge control agents and mold release agents can be melt-kneaded together with the masterbatch and binder resin, and of course, they may be added when dissolved and dispersed in an organic solvent.

Next, a toner manufacturing method will be described. Here, although a preferable manufacturing method is shown, it is not limited to this.
The modified polyester resin as a resin for toner binder is produced, for example, by the following method.
Polyhydric alcohol (PO) and polyvalent carboxylic acid (PC) are heated to 150-280 ° C. in the presence of a known esterification catalyst such as tetrabutoxytitanate, dibutyltin oxide, etc., and water generated while reducing the pressure as necessary. Distill off to obtain a polyester having a hydroxyl group. Subsequently, at 40-140 degreeC, this is made to react with a polyvalent isocyanate compound (PIC), and the polyester prepolymer (A) which has an isocyanate group is obtained. Further, the polyester prepolymer (A) is reacted with amines at 0 to 140 ° C. to obtain a urea-modified polyester. When the unmodified polyester is used in combination, the unmodified polyester is produced in the same manner as the polyester having a hydroxyl group, and this is dissolved and mixed in the solution after completion of the urea-modified polyester reaction.

Next, a toner manufacturing method in an aqueous medium will be described.
The toner particles may be formed by reacting a dispersion made of a polyester prepolymer (A) having an isocyanate group in an aqueous medium with amines (B), or using a urea-modified polyester produced in advance. good. As a method of stably forming a dispersion composed of urea-modified polyester or polyester prepolymer in an aqueous medium, a composition of a toner raw material composed of urea-modified polyester or polyester prepolymer is added to an aqueous medium, and shearing force is applied. Examples include a method of dispersing. Prepolymer and other toner composition (hereinafter referred to as toner raw material), colorant masterbatch, release agent, charge control agent, unmodified polyester resin, etc. form a dispersion in an aqueous medium. However, it is more preferable to mix the toner raw materials in advance and then add and disperse the mixture in the aqueous medium. Further, other toner raw materials such as a colorant, a release agent, and a charge control agent do not necessarily have to be mixed when forming particles in an aqueous medium, and may be added after the particles are formed. Good. For example, after forming particles not containing a colorant, the colorant can be added by a known dyeing method.

The dispersion method is not particularly limited, and known equipment such as a low-speed shear type, a high-speed shear type, a friction type, a high-pressure jet type, and an ultrasonic wave can be applied. In order to make the particle size of the dispersion 2 to 20 μm, a high-speed shearing type is preferable. When a high-speed shearing disperser is used, the number of rotations is not particularly limited, but is usually 1000 to 30000 rpm, preferably 5000 to 20000 rpm. The dispersion time is not particularly limited, but in the case of a batch method, it is usually 0.1 to 5 minutes. The temperature during dispersion is usually 0 to 150 ° C. (under pressure), preferably 40 to 98 ° C. Higher temperatures are preferred in that the dispersion of a urea-modified polyester or polyester prepolymer has a low viscosity and is easy to disperse.
The amount of the aqueous medium used relative to 100 parts of the toner composition containing urea-modified polyester or polyester prepolymer is usually 50 to 2000 parts by weight, preferably 100 to 1000 parts by weight. If the amount is less than 50 parts by weight, the dispersion state of the toner composition is poor, and toner particles having a predetermined particle diameter cannot be obtained. If it exceeds 2000 parts by weight, it is not economical.
The aqueous medium may be water alone or an organic solvent such as alcohol (methanol, isopropyl alcohol, ethylene glycol, etc.), dimethylformamide, tetrahydrofuran, cellosolves (methyl cellosolve, etc.), lower ketones (acetone, methyl ethyl ketone, etc.). It may be included.

In order to satisfactorily emulsify and disperse the oily phase in which the toner composition is dispersed in an aqueous medium, a dispersant such as a surfactant and organic fine particles is appropriately added as necessary. The use of a dispersant is preferable in that the particle size distribution becomes sharp and the dispersion is stable.
As surfactants, anionic surfactants such as alkylbenzene sulfonates, α-olefin sulfonates, phosphate esters, alkylamine salts, amino alcohol fatty acid derivatives, polyamine fatty acid derivatives, amine salt types such as imidazoline, Quaternary ammonium salt type cationic surfactants such as alkyltrimethylammonium salt, dialkyldimethylammonium salt, alkyldimethylbenzylammonium salt, pyridinium salt, alkylisoquinolinium salt, benzethonium chloride, fatty acid amide derivative, polyhydric alcohol Nonionic surfactants such as derivatives, for example, amphoteric surfactants such as alanine, dodecyldi (aminoethyl) glycine, di (octylaminoethyl) glycine and N-alkyl-N, N-dimethylammonium betaine. It is.

  The organic fine particles have an effect of stabilizing the toner base particles formed in the aqueous medium. In particular, at least one selected from vinyl resins, polyurethane resins, epoxy resins, silicone resins, polyester resins, and fluorine resins may be used. Specifically, MMA polymer fine particles 1 μm and 3 μm, styrene fine particles 0.5 μm and 2 μm, styrene-acrylonitrile fine particle polymer 1 μm, trade names are PB-200H (manufactured by Kao Corporation), SGP (manufactured by Soken Co., Ltd.), Technopolymer SB (Sekisui Chemical Co., Ltd.), SGP-3G (manufactured by Sokensha), Micropearl (manufactured by Sekisui Fine Chemical Co., Ltd.) and the like.

  Further, as a dispersant that can be used in combination with the surfactant and the fine particle polymer, the dispersed droplets may be stabilized by a polymer protective colloid. For example, (meth) acrylic monomer containing acrylic acid, methacrylic acid, α-cyanoacrylic acid, α-cyanomethacrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid or maleic anhydride, or hydroxyl group For example, β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, β-hydroxypropyl acrylate, β-hydroxypropyl methacrylate, γ-hydroxypropyl acrylate, γ-hydroxypropyl methacrylate, 3-chloroacrylate 2-hydroxypropyl, 3-chloro-2-methacrylic acid methacrylate, diethylene glycol monoacrylate, diethylene glycol monomethacrylate, glycerol monoacrylate, glycerol monomethacrylate, N-methylol acrylamide, N-methylol methacrylamide, etc., vinyl alcohol or ethers with vinyl alcohol, such as vinyl methyl ether, vinyl ethyl ether, vinyl propyl ether, or esters of compounds containing vinyl alcohol and a carboxyl group Such as pinyl acetate, pinyl propionate, vinyl butyrate, acrylamide, methacrylamide, diacetone acrylamide or their methylol compounds, acid chlorides such as acrylic acid chloride, methacrylic acid chloride, pinyl pyridine, vinyl pyrrolidone, vinyl imidazole, ethylene Homopolymers or copolymers such as those having a nitrogen atom such as imine or a heterocyclic ring thereof, polyoxyethylene, polyoxypropylene, Reoxyethylene alkylamine, polyoxypropylene alkylamine, polyoxyethylene alkylamide, polyoxypropylene alkylamide, polyoxyethylene nonyl phenyl ether, polyoxyethylene lauryl phenyl ether, polyoxyethylene stearyl phenyl ester, polyoxyethylene nonyl Polyoxyethylenes such as phenyl esters, celluloses such as methyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose can be used.

In order to remove the organic solvent from the obtained emulsified dispersion, a method in which the temperature of the entire system is gradually raised and the organic solvent in the droplets is completely removed in a short time can be employed. In addition, when an acid such as calcium phosphate salt or an alkali-soluble substance is used as the dispersion stabilizer, the calcium phosphate salt is removed from the fine particles by a method such as dissolving the calcium phosphate salt with an acid such as hydrochloric acid and washing with water. To do. It can also be removed by operations such as enzymatic degradation.
When a dispersant is used, the dispersant can remain on the surface of the toner particles. However, it is preferable from the charged surface of the toner that the dispersant is washed and removed after the crosslinking and / or elongation reaction.

Furthermore, in order to lower the viscosity of the toner composition, a solvent in which urea-modified polyester or polyester prepolymer is soluble can be used. The use of a solvent is preferable in that the particle size distribution becomes sharp. The solvent is preferably volatile with a boiling point of less than 100 ° C. from the viewpoint of easy removal. Examples of such solvents include toluene, xylene, benzene, carbon tetrachloride, methylene chloride, 1,2-dichloroethane, 1,1,2-trichloroethane, trichloroethylene, chloroform, monochlorobenzene, dichloroethylidene, methyl acetate, acetic acid. Ethyl, methyl ethyl ketone, methyl isobutyl ketone and the like can be used alone or in combination of two or more. In particular, aromatic solvents such as toluene and xylene and halogenated hydrocarbons such as methylene chloride, 1,2-dichloroethane, chloroform, and carbon tetrachloride are preferable. The usage-amount of the solvent with respect to 100 parts of prepolymers is 0-300 parts normally, Preferably it is 0-100 parts, More preferably, it is 25-70 parts. When a solvent is used, it is removed by heating under normal pressure or reduced pressure after the crosslinking and / or extension reaction.
The crosslinking and / or extension reaction time is selected depending on the reactivity depending on the combination of the isocyanate group structure of the prepolymer and amines, and is usually 10 minutes to 40 hours, preferably 2 to 24 hours. The reaction temperature is generally 0 to 150 ° C, preferably 40 to 98 ° C. Moreover, a well-known catalyst can be used as needed. Specific examples include dibutyltin laurate and dioctyltin laurate.

  After completion of the reaction, the organic solvent is removed from the emulsified dispersion (reactant), washed and dried to obtain toner base particles. In order to remove the organic solvent, the temperature of the entire system is gradually raised in a laminar stirring state, and after giving strong stirring in a certain temperature range, the solvent base is removed to produce spindle-shaped toner base particles. . Further, when an acid such as calcium phosphate salt or an alkali-soluble material is used as the dispersion stabilizer, the calcium phosphate salt is dissolved from the toner base particles by a method such as dissolving the calcium phosphate salt with an acid such as hydrochloric acid and washing with water. Remove. It can also be removed by operations such as enzymatic degradation.

A charge control agent is injected into the toner base particles obtained above, and then an external additive is externally added to obtain a toner. The injection of the charge control agent and the external addition of the external additive are performed by a known method using a mixer or the like.
Thereby, a toner having a small particle size and a sharp particle size distribution can be obtained. Furthermore, the spherical shape can be controlled by giving strong stirring in the step of removing the organic solvent.

Hereinafter, specific examples of the present invention will be described.
(Example 1)
In preparing the toner, a toner binder was first synthesized.
That is, 690 parts of bisphenol A ethylene oxide 2-mole adduct, 256 parts of isophthalic acid, and 2 parts of dibutyltin oxide were placed in a reaction vessel equipped with a cooling pipe, a stirrer, and a nitrogen introduction pipe, and at normal pressure of 230 ° C. for 8 hours. The mixture was further reacted for 5 hours at a reduced pressure of 10 to 15 mmHg, then cooled to 160 ° C., 18 parts of phthalic anhydride was added thereto and reacted for 2 hours. Subsequently, it cooled to 80 degreeC and made it react with 188 parts of isophorone diisocyanate in ethyl acetate for 2 hours, and the isocyanate containing prepolymer was obtained. Next, 267 parts of the prepolymer and 14 parts of isophoronediamine were reacted at 50 ° C. for 2 hours to obtain a urea-modified polyester. In the same manner as above, 690 parts of bisphenol A ethylene oxide 2-mole adduct and 256 parts of terephthalic acid were polycondensed at 230 ° C. for 8 hours under normal pressure, and then reacted for 5 hours under reduced pressure of 10 to 15 mmHg to give an unmodified polyester. Obtained.
100 parts of urea-modified polyester and 900 parts of unmodified polyester were dissolved and mixed in 1800 parts of an ethyl acetate solvent to obtain an ethyl acetate solution of a toner binder. A portion was dried under reduced pressure to isolate the toner binder. In addition, the number average molecular weight of the said polyester resin was about 6000, the glass transition point (Tg) was 72 degreeC, and the acid value was 21 mgKOH / g.

Next, a toner was prepared.
In a beaker, 210 parts of an ethyl acetate solution of the toner binder, 2 parts of an iron-containing monoazo dye (T-77 manufactured by Hodogaya Chemical Co., Ltd.) as a charge control agent, and 4 parts of copper phthalocyanine blue pigment are placed at 60 ° C. and a TK homomixer is placed. Used and stirred at 12000 rpm to uniformly dissolve and disperse. In a beaker, 265 parts of ion-exchanged water, 260 parts of a 10% aqueous solution of tricalcium phosphate and 0.2 part of sodium dodecylbenzenesulfonate were uniformly dissolved. Next, the temperature was raised to 60 ° C., stirred at 12000 rpm with a TK homomixer, transferred to a flask with a thermometer capable of distilling 500 g of the suspension, and stirred at 40-50 ° C. under reduced pressure, 45-50. The solvent was removed in minutes. Next, after filtering, washing and drying, air classification was performed to obtain spherical toner particles.
To 100 parts of the obtained toner particles, 0.5 part of hydrophobic silica having a degree of hydrophobicity of 60% and 0.5 part of hydrophobic titanium oxide having a degree of hydrophobicity of 60% are mixed with a Henschel mixer. Thus, an electrophotographic toner was obtained.
The above electrophotographic toner is mixed using a color developer TYPE L (manufactured by Ricoh Co., Ltd.) so that the toner ratio is 5 wt% of the total amount, and then stirred for 1 minute using a turbula mixer. It was used for the following evaluation as an example developer.

Next, the image test will be described.
Using the electrophotographic toner, image evaluation was performed with an evaluation machine obtained by modifying IMAGEIO COLOR 5100 (manufactured by Ricoh). The image is output in the printer mode using a document with an image area ratio of 6%, and the width of one dot line image in the sub-scanning line direction on the photosensitive member and the intermediate transfer member, the pile height, the background stain, the dust, the void image The presence or absence was evaluated. The results are shown in Table 1. The development conditions are as follows.
Development bias: AC + DC wave, 4.50 KHz rectangular wave, Vp-p: 800 V, Duty = 35%, Vdc: −500 V
Transfer bias: 1400V
Photoconductor: 90 mmφ, dark part potential Vd: −700 V, light part potential Vl: −150 V
In Table 1, the symbols in the image evaluation column represent the following states.
◯: Dirt, dust, hollow image… None ×: Dirt, dust, hollow image… Yes

(Example 2)
A similar evaluation was performed in the same manner as in Example 1 except that the electrophotographic toner of Example 1 was used and the DC component Vdc of the developing bias was changed to -550V. The results are shown in Table 1.

(Example 3)
Using the electrophotographic toner of Example 1 above, the DC component Vdc of the developing bias is set to -630 V, the same developer is used under the same conditions, and a toner layer is formed on the photosensitive member from another developing device, and intermediate transfer is performed. The same evaluation was carried out in the same manner as in Example 1 except that it was superimposed twice on the body. The results are shown in Table 1.

Example 4
First, a toner binder was synthesized as follows.
That is, 314 parts of bisphenol A ethylene oxide 2-mole adduct, 314 parts of bisphenol A propylene oxide 2-mole adduct, 274 parts of isophthalic acid and 20 parts of trimellitic anhydride were polycondensed in the same manner as in Example 1, followed by isophorone diisocyanate. 154 parts were reacted to obtain a prepolymer. Next, 213 parts of the prepolymer, 9.5 parts of isophoronediamine and 0.5 part of dibutylamine were reacted in the same manner as in Example 1 to obtain a urea-modified polyester. 200 parts of urea-modified polyester and 800 parts of unmodified polyester were dissolved and mixed in 1000 parts of ethyl acetate to obtain an ethyl acetate solution of a toner binder. Thereafter, the toner binder was isolated by partially drying under reduced pressure. In addition, the number average molecular weight of the said polyester resin was about 6000, the glass transition point (Tg) was 70 degreeC, and the acid value was 18 mgKOH / g.
Next, a toner was prepared as follows.
That is, spherical toner particles were obtained in the same manner as in Example 1. Next, 100 parts of toner particles were blended so that the amount of silica fine particles having a hydrophobization degree of 55% was 0.5 parts of the toner amount, and mixed and stirred with a Henschel mixer to prepare an electrophotographic toner.
The electrophotographic toner prepared by the above method was evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Example 5)
A similar evaluation was performed in the same manner as in Example 1 except that the electrophotographic toner of Example 4 was used and the DC component Vdc of the developing bias was set to -550V. The results are shown in Table 1.

(Example 6)
Using the electrophotographic toner of Example 4 above, the DC component Vdc of the developing bias is set to -630 V, the same developer is used under the same conditions, and a toner layer is formed on the photosensitive member from another developing device, and intermediate transfer is performed. The same evaluation was carried out in the same manner as in Example 1 except that it was superimposed twice on the body. The results are shown in Table 1.

(Comparative Example 1)
Using the electrophotographic toner of Example 1 above, the DC component of the developing bias is set to −700 V, the same developer is used under the same conditions, and a toner layer is formed on the photosensitive member from another developing device, and an intermediate transfer member The same evaluation was performed in the same manner as in Example 1 except that it was overlaid four times. The results are shown in Table 1.

(Comparative Example 2)
First, a toner was prepared as follows.
That is, 93 parts of methanol, 7 parts of polyvinyl methyl ether, 28 parts of styrene monomer, 7 parts of n-butyl acrylate, 1 part of carbon black, 1 part of chromium complex of di-tert-butylsalicylic acid, 2,2′-azobis A mixture consisting of 1 part of isobutyronitrile was put into a flask, mixed well, and nitrogen gas was introduced into the mixture. The amount of nitrogen gas introduced was 250 cc / min, and replacement was performed for 30 minutes. Thereafter, the amount of nitrogen introduced was suppressed to 50 cc / min. Next, this mixture was polymerized at about 50 to 60 ° C. for 3 hours to produce polymer particles. After the polymerization reaction, the resulting reaction mixture was repeatedly washed with methanol and filtered to remove polyvinyl methyl ether. Thereafter, the obtained toner particles are further vacuum dried, and then 100 parts of toner particles are 0.5 parts of hydrophobic silica having a hydrophobization degree of 60%, and the hydrophobic titanium oxide having a hydrophobization degree of 60% is further added to 0.1 parts. 5 parts were mixed with a Henschel mixer to obtain an electrophotographic toner. The electrophotographic toner obtained by the above method was evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 3)
First, a toner was prepared as follows.
That is, 83 parts of styrene, 17 parts of n-butyl acrylate, 7 parts of carbon black, 0.03 part of a charge control agent “N1” (trade name; manufactured by Orient Chemical Co., Ltd.), 0.6 part of divinylbenzene, t-dodecyl mercaptan 1 5 parts and 5 parts of pentaerythritol tetramitytylate were dispersed with a bead mill at room temperature to obtain a uniform mixed solution. While stirring the mixed solution, 5 parts of t-butylperoxy-2-ethylhexanoate was added, and stirring was continued until the droplets became uniform. On the other hand, to an aqueous solution in which 9.5 parts of magnesium chloride was dissolved in 250 parts of ion-exchanged water, an aqueous solution in which 4.8 parts of sodium hydroxide was dissolved in 50 parts of ion-exchanged water was gradually added with stirring. A colloidal dispersion was prepared. A polymerizable monomer composition was charged into the colloid and stirred with high shear at 12000 rpm using a TK homomixer to granulate droplets of the polymerizable monomer mixture. The aqueous dispersion of the granulated polymerizable monomer mixture is put into a reactor equipped with a stirring blade, the polymerization reaction is started at 90 ° C., polymerized for 8 hours and then cooled to obtain an aqueous dispersion of polymer particles. Got. While stirring the aqueous dispersion of polymer particles obtained as described above, acid cleaning was performed with sulfuric acid at a pH of 4 or less, water was separated by filtration, and 500 parts of ion-exchanged water was newly added and re-added. Slurried and washed with water. Thereafter, again, dehydration and water washing were repeated several times, and the solid content was separated by filtration, followed by drying at 45 ° C. for one day in a dryer to obtain toner particles.
100 parts of the obtained toner particles are mixed with 0.5 part of hydrophobic silica having a hydrophobization degree of 60% and 0.5 part of hydrophobized titanium oxide having a hydrophobization degree of 60% by using a Henschel mixer. Toner was obtained. The obtained electrophotographic toner was evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 4)
Using the toner of Example 1, the DC component Vdc of the developing bias is set to −800 V, the same developer is used under the same conditions, a toner layer is formed on the photosensitive member from another developing device, and 4 on the intermediate transfer member. The same evaluation was carried out in the same manner as in Example 1 except that the test was repeated. The results are shown in Table 1.

As can be seen from Table 1, in Examples 1 to 6, the requirements of the present invention were satisfied, so that good images free from background stains, dust, voids and the like could be obtained. On the other hand, in Comparative Examples 1 and 4, since the toner pile height was too large to satisfy the requirements of the present invention, problems such as background contamination occurred. In Comparative Examples 2 and 3, since the circularity of the toner particles was too low to satisfy the requirements of the present invention, defective images such as dust and voids were generated.

(Example 7)
First, a toner was prepared as follows.
That is, with respect to 100 parts of the toner particles (volume average particle diameter 4.5 μm) prepared in Example 4, 0.4 parts of hydrophobic silica having a primary particle diameter of 15 nm and a hydrophobization degree of 60% is the same as the primary particles. 0.4 part of hydrophobized titanium oxide having a diameter of 20 nm and a hydrophobization degree of 60% was mixed with a Henschel mixer, and then 0.4 g of large particle size silica (RX-50 manufactured by Nippon Aerosil Co., Ltd.) having a primary particle diameter of 100 nm was mixed. Partly added and mixed again with a Henschel mixer to obtain an electrophotographic toner.
The obtained electrophotographic toner is mixed with an electrophotographic carrier (average particle size 50 μmφ) used in the color developer TYPE L (manufactured by Ricoh), and mixed so that the ratio of the toner is 5 wt% of the total amount. After that, the developer was stirred for 1 minute using a turbula mixer and used for the following evaluation.
Next, the image test will be described.
Using the electrophotographic toner described above, an image evaluation was performed after outputting 20000 images in the printer mode using a document with an image area ratio of 6% using an evaluation machine in which IMAGEIO COLOR 5100 (manufactured by Ricoh) was modified. Carried out. Similar to the first embodiment, the image to be evaluated is the width of one dot line image in the sub-scanning line direction on the photosensitive member and the intermediate transfer member, the pile height, the background stain, the dust, and the presence or absence of a hollow image. Thereafter, the toner formed on the photosensitive member and the intermediate transfer member was collected, and the loose density of the toner was measured by a method based on the JIS R 1628 standard. The results are shown in Table 2. The development conditions are as follows.
Development bias: AC + DC wave, 4.50 KHz rectangular wave, Vp-p: 800 V, Duty = 35%, Vdc: −500 V
Transfer bias: 1400V
Photoconductor: 90 mmφ, dark portion potential Vd: −700 V, light portion potential Vl: −150 V
In Table 1, the symbols in the image evaluation column represent the following states.
◯: Dirt, dust, hollow image… None ×: Dirt, dust, hollow image… Yes

(Example 8)
Using the toner particles of Example 7 above, 0.4 part of hydrophobic silica having a primary particle size of 15 nm and a hydrophobicity of 60%, and a hydrophobic titanium oxide having a primary particle size of 20 nm and a hydrophobicity of 60% 0.4 part was mixed with a Henschel mixer. Thereafter, 0.8 part of silica having a large primary particle diameter of 100 nm (RX-50 manufactured by Nippon Aerosil Co., Ltd.) was added and mixed again with a Henschel mixer to obtain an electrophotographic toner. In the same manner, the same evaluation was performed. The results are shown in Table 2.

Example 9
Using the toner particles of Example 7 above, 0.5 part of hydrophobic silica having a primary particle diameter of 15 nm and a hydrophobicity of 60%, and a hydrophobic titanium oxide having a primary particle diameter of 20 nm and a hydrophobicity of 60% 0.5 part was mixed with a Henschel mixer. Thereafter, 0.4 part of silica having a large primary particle size of 100 nm (RX-50 manufactured by Nippon Aerosil Co., Ltd.) was added and mixed again with a Henschel mixer to obtain an electrophotographic toner. In the same manner, the same evaluation was performed. The results are shown in Table 2.

(Example 10)
Evaluation was performed in the same manner as in Example 9 except that the electrophotographic toner particles of Example 9 were used and a developer having an average particle diameter of 35 μmφ was used. The results are shown in Table 2.

(Comparative Example 5)
An electrophotographic toner was prepared and evaluated in the same manner as in Example 7 except that the toner particles of Example 7 were used but no large particle size silica was added. The results are shown in Table 2.

(Comparative Example 6)
Using 100 parts of an irregularly shaped toner (volume average particle size 6.8 μm) usually used in IMAGEIO COLOR 5100 (manufactured by Ricoh Co., Ltd.), the same formulation as in Example 7 was used, and the primary particle size was 15 nm and the degree of hydrophobicity was 0.4 part of 60% hydrophobic silica and 0.4 part of hydrophobized titanium oxide having a primary particle size of 20 nm and a hydrophobization degree of 60% were mixed with a Henschel mixer. Thereafter, the same evaluation as in Example 7 was performed. The results are shown in Table 2.

As is clear from Table 2, Examples 7 to 10 satisfy the requirements of the present invention, so that good images free from background stains, dust, voids and the like could be obtained. On the other hand, in Comparative Example 5, since the large particle size inorganic fine particles were not added as an external additive, the fluidity of the developer deteriorated, and the loose apparent density did not satisfy the requirements of the present invention. A malfunction occurred. In Comparative Example 6, since the irregular toner is used, the average circularity of the toner is smaller than when the spherical toner is used and the requirement of the present invention is not satisfied. , Hollowing out, etc. occurred.

1 is a schematic configuration diagram of an image forming apparatus applied to an image forming method of the present invention. 6 is a graph showing the correlation between the total amount of toner external additives and the loose apparent density.

Explanation of symbols

1 Electrophotographic photoreceptor (first image carrier)
2 Developing device 3 Intermediate transfer member (second image carrier)
4 Charging device 5 Exposure light 6 Cleaning device 7 Registration roller 8 Transfer device 9 Fixing device 10 Paper feeding device

Claims (10)

A latent image forming step of forming an electrostatic latent image on the first image carrier;
A developing step of developing the formed electrostatic latent image using a developer corresponding to a color image to form a monochromatic toner image;
Repeating the first transfer step of transferring the toner image formed on the first image carrier onto the second image carrier a plurality of times,
After forming a color image in which a single color toner image is laminated on the second image carrier,
A second transfer step of transferring a color image formed on the second image carrier to a recording medium;
A color image forming method for performing a fixing step of fixing the color image transferred to the recording medium by heating and / or pressurizing the recording medium;
The developer is a two-component developer having a toner and a carrier. The toner particles contained in the two-component developer have a volume average particle diameter of 1 to 8 μm, an average circularity of 0.92 to 0.99, and a looseness. The apparent density is 0.5 g / cm ³ or more,
The thickness of the toner layer formed on the first image carrier is not more than three times the volume average particle diameter of the toner particles, and the toner layer of the color image formed on the second image carrier is An image forming method, wherein the thickness is not more than 5.41 times the volume average particle diameter of the toner particles. The true specific gravity of the toner is 1.2 to 1.5 g / cm ³ ,
The image forming method according to claim 1, wherein the toner particles contain 0.01 to 5 wt% of inorganic fine particles having a primary particle diameter of 5 nm to 2 μm. The inorganic fine particles include small-sized inorganic fine particles whose primary particles have a volume average particle size of 5 nm to 80 nm and large-sized inorganic fine particles whose primary particles have a volume average particle size of 80 nm to 200 nm. The image forming method according to claim 2. The image forming method according to claim 3, wherein the small-sized inorganic fine particles are a mixture of two or more selected from silica, titanium oxide, and alumina. The inorganic fine particles are hydrophobic inorganic fine particles surface-treated with silicone oil or a silicone coupling agent, and the hydrophobic degree of the hydrophobic inorganic fine particles is 50% or more. 5. The image forming method according to any one of 4 above. The toner particles are obtained by dissolving or dispersing a toner composition containing a resin and a colorant in an organic solvent, and dispersing the obtained solution or dispersion in an aqueous medium in the presence of an inorganic dispersant or fine particle polymer. The image according to any one of claims 1 to 5, wherein the image is produced by polyaddition reaction of the dissolved product or dispersion and removing the solvent from the obtained emulsified dispersion. Forming method. The image forming method according to claim 6, wherein the resin is a polyester resin and has a number average molecular weight of 2000 to 15000, a glass transition point of 55 to 75 ° C., and an acid value of 1 to 30 mgKOH / g. . The image forming method according to claim 7, wherein the polyester resin contains a modified polyester having a urea bond. The image forming method according to claim 7 or 8, wherein the polyester resin contains an alkylene oxide adduct of bisphenols as a polyol component. The image forming method according to claim 1, wherein the toner particles contain wax as a release agent.

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