JP4557855B2 - Method for producing polymerized toner - Google Patents

Description

  The present invention relates to a method for producing toner used for developing an electrostatic latent image formed by a method such as electrophotography, electrostatic recording, magnetic recording, or toner jet recording.

  Various methods are known as an electrophotographic image forming method. In general, a photoconductive substance is used on an electrostatic image bearing member (hereinafter also referred to as “photosensitive member”) by various means. An electrostatic latent image is formed and then developed with toner to make the electrostatic latent image a visible image. If necessary, the visible image is transferred to a recording medium such as paper and then heated. Alternatively, it is fixed as a toner image on the recording medium by pressure to obtain a copy. Examples of such an image forming apparatus include a printer and a copying machine.

  In recent years, these printers and copiers are required to increase the resolution of images by digitization, and at the same time, increase the printing or copying speed, or save space and reduce power consumption by downsizing the apparatus. ing. Various types of fixing devices used in these printers and copiers have been put to practical use, but the most common method is a heat-pressing method using a heat roller. In this method, a fixing sheet as a recording medium to which toner is transferred is provided between a heat roller having a surface made of a material having releasability with respect to toner and a pressure roller that presses the surface. Fixing is performed by passing the toner image surface so as to be in contact with the heat roller side. In this method, since the surface of the heat roller and the toner image surface of the fixing sheet are in contact with each other under pressure, the toner is excellent in thermal efficiency when fusing onto the fixing sheet, and thus a particularly high speed is required. It is suitably used for applications. Further, as a method used for applications requiring low power consumption, a film fixing method can be mentioned as a representative method. This method uses a film unit equipped with a heating device in place of the heat roller, and performs fixing by passing a sheet to be fixed under a relatively low pressure between the film and the pressure roller. It is. In this method, the heat capacity of the film is small and the wait time can be shortened, so that the power consumption can be reduced.

  On the other hand, in order to satisfy the above-mentioned demands for higher speed and lower power consumption, improvement in fixing performance of the toner itself is also required. That is, it is desired to realize a toner that can be fixed at a lower temperature.

  As a general method for solving the low-temperature fixability, there are a method of lowering the molecular weight of the binder resin constituting the toner and a method of lowering the glass transition temperature (Tg). Specifically, for example, a method of obtaining a binder resin by polymerizing a polymerizable monomer in the presence of a chain transfer agent such as n-dodecyl mercaptan or t-dodecyl mercaptan is known. However, according to such a method of simply lowering the molecular weight and glass transition temperature (Tg) of the binder resin, a so-called high temperature offset in which the toner melted at the time of fixing adheres to the surface of the heat roller or the fixing film. It has a problem that the toner particles are likely to occur, the toner particles are likely to be blocked and the storage stability is lowered, and further, the developability in long-term use and the fixation to the photosensitive member are likely to occur. It was.

  Examples of the method for improving the high temperature offset resistance include a method of forming an appropriate cross-linked site in the binder resin. In general, a method using a polyfunctional monomer such as divinylbenzene or diethylene glycol dimethacrylate is used to form a cross-linked site. However, the crosslinking component thus formed (THF insoluble matter) has an action of inhibiting low-temperature fixability. Therefore, it is important to keep the amount of THF insolubles to the minimum necessary, and to balance the low-temperature fixability and the high-temperature offset resistance, but when using the above-mentioned polyfunctional monomer, the dependence on the amount used is important. Is very large and it is difficult to control the amount of THF-insoluble matter, which hinders improvement in production stability.

  In order to solve these problems, the low molecular weight polymer component effective in improving low temperature fixability and the high molecular weight polymer component effective in improving high temperature offset resistance coexist effectively in the binder resin. Various methods for achieving this have been studied.

  For example, after using a compound having 3 or more t-butyl peroxide groups in one molecule as a polymerization initiator and subjecting the high molecular weight polymer component to suspension polymerization at a temperature of 95 ° C. or higher, the high molecular weight polymer component There has been proposed a method of producing a binder resin for toner by suspension polymerization of a low molecular weight polymer component in the presence of (see Patent Document 1). In addition, a low molecular weight polymer component is polymerized using a polymerization initiator having three or more cleavage parts in one molecule, and then the high molecular weight polymer component is polymerized in the presence of the low molecular weight polymer component. A method of manufacturing a binder resin for use in the environment has been proposed (see Patent Document 2). The toner binder resin thus obtained is melt-kneaded by adding a colorant, if necessary, a charge control agent, wax, etc., and then finely pulverized and classified to obtain a so-called pulverized toner. Can be manufactured.

  Furthermore, a method for producing a suspension polymerization toner using a mixture of a tetrafunctional or higher functional polymerization initiator and a monofunctional polymerization initiator as a polymerization initiator has been proposed (see Patent Document 3). This toner can obtain a high molecular weight polymer component without increasing the crosslink density as in the case of using a polyfunctional monomer by using the polyfunctional initiator described above. Is improved. Moreover, since a relatively low molecular weight polymer component can also be obtained by using a monofunctional polymerization initiator in combination, the low-temperature fixability is not impaired.

JP 07-228609 A Japanese Patent Laid-Open No. 09-106099 JP 07-152198 A

  However, among the conventional examples described above, the methods disclosed in Patent Document 1 and Patent Document 2 both perform the polymerization reaction in two stages, and not only the production process is complicated, but also high If the molecular weight of the molecular weight polymer component is increased, the dispersibility of the colorant, charge control agent, wax, etc. during melt-kneading is hindered. This is a cause of dirt, fusion to a photosensitive member, filming, and the like. In addition, when the kneading conditions during melt kneading are strengthened for the purpose of improving dispersibility, the molecular weight after toner production decreases due to the breaking of the molecular chain of the binder resin, etc., and the effect of improving the high temperature offset resistance is insufficient. I have found out that

  On the other hand, the toner by the method disclosed in Patent Document 3 described above is a polymer component having a high molecular weight due to a tetrafunctional or higher polymerization initiator in addition to a conventional polymer component having a molecular weight due to a monofunctional polymerization initiator. Are formed simultaneously. According to this method, the dispersibility of the various components described above is not impaired, and since the melt kneading step is not included, problems such as the breaking of the molecular chain of the binder resin as described above do not occur. As a result, a toner having a relatively wide fixing area can be obtained. However, there is a limit to the expansion of the molecular weight distribution of the binder resin by this method, and polymer particles having a plurality of distinctly different molecular weight distributions cannot be obtained. That is, the objective of achieving both low temperature fixability and high temperature offset resistance is not always satisfactory, and there is room for further improvement.

  Accordingly, it is an object of the present invention to provide a toner manufacturing method that solves the above-described conventional problems. That is, an object of the present invention is to provide a method for producing a polymerized toner which is excellent in both low-temperature fixability and high-temperature offset resistance and excellent in various image characteristics and durability in long-term use.

In order to achieve the above object, the method for producing a polymerized toner of the present invention comprises the step of polymerizing a monomer composition containing at least a polymerizable monomer and a colorant to obtain polymer particles. The polymerization is carried out in the presence of at least two kinds of polymerization initiators including at least a peroxydicarbonate polymerization initiator and other polymerization initiators, and gel permeation of tetrahydrofuran (THF) soluble matter. In the molecular weight distribution by chromatography (GPC) measurement, polymer particles having at least one peak or shoulder on each of the low molecular weight side and the high molecular weight side , which are produced by polymerization with the two or more kinds of polymerization initiators, are obtained. It is characterized by this.

  The peroxydicarbonate polymerization initiator can easily lower the molecular weight of the binder resin constituting the toner. When the polymerization is performed using the peroxydicarbonate polymerization initiator in combination with another polymerization initiator, other than the polymer component derived from the peroxydicarbonate polymerization initiator, A polymer component derived from the polymerization initiator can be formed in the binder resin. Therefore, polymer particles each containing a low molecular weight component and a high molecular weight component having different molecular weight distributions can be obtained depending on the combination of the polymerization initiators to coexist.

  Further, in the method for producing a polymerized toner of the present invention, the polymerization initiator coexisting with the peroxydicarbonate polymerization initiator has a 10-hour half-life temperature higher than at least the peroxydicarbonate polymerization initiator. And at least one of them is characterized in that the 10-hour half-life temperature difference is in the range of 10 to 50 ° C. By using a polymerization initiator having such a 10-hour half-life temperature in combination, polymer particles having a broader molecular weight distribution in which the low molecular weight component and the high molecular weight component are different from each other can be obtained. As such a polymerization initiator, a diacyl peroxide polymerization initiator and / or a peroxyester polymerization initiator can be used.

  Further, in the method for producing a polymerized toner of the present invention, the polymer particles have at least one peak or shoulder in the molecular weight region of 5000 to 20000 in the molecular weight distribution by GPC measurement of the THF-soluble matter, and the molecular weight It has at least one peak or shoulder in the region of 50,000 to 500,000. That is, by controlling the molecular weight distribution of the binder resin within such a range, it is possible to achieve both low-temperature fixability and high-temperature offset resistance, which are the objects of the present invention.

  Furthermore, in this invention, 5-30 mass parts THF insoluble matter can be formed in 100 mass parts of resin components in the resin component of the said polymer particle. The formation of such THF-insoluble matter further promotes the effect of improving the high-temperature offset resistance described above. When the THF-insoluble content is less than 5 parts by mass, the effect of promoting high-temperature offset resistance cannot be obtained, and when the THF-insoluble content exceeds 30 parts by mass, the low-temperature fixability is remarkably deteriorated.

  As described above, according to the present invention, there is provided a method for producing a polymerized toner which is excellent in both low-temperature fixability and high-temperature offset resistance and excellent in various image characteristics and durability in long-term use. Can do.

  Hereinafter, the present invention will be described in more detail with reference to preferred embodiments.

  In the toner production process using the suspension polymerization method, the present inventors easily reduce the molecular weight of the binder resin constituting the toner when a peroxydicarbonate-based polymerization initiator is used as the polymerization initiator. When the peroxydicarbonate polymerization initiator is used in combination with other polymerization initiators, a low molecular weight polymer component derived from the peroxydicarbonate polymerization initiator is added. The present inventors have found that a higher molecular weight polymer component derived from a polymerization initiator used in combination with the binder resin can be formed in the binder resin while maintaining the state, and the present invention has been completed.

  Here, the suspension polymerization method as a feature of the production method of the present invention will be described.

  In the suspension polymerization method, a monomer composition obtained by adding a polymerization initiator, a polyfunctional monomer, a chain transfer agent, or the like to a polymerizable monomer, and an aqueous medium containing a dispersion stabilizer. It is a method of carrying out polymerization by suspending in a granule and heating it. In the monomer composition, colorants and other substances that need to be encapsulated in the toner particles are dissolved or dispersed in advance to perform polymerization, and the polymer particles after the polymerization are used as toner particles as they are. So-called suspension polymerization toner can be produced.

  The suspension polymerization toner according to the present invention is produced as follows.

  First, at least a colorant is added to a polymerizable monomer that becomes a toner composition, that is, a binder resin, and these are uniformly dissolved or dispersed using a disperser such as a homogenizer, a ball mill, a colloid mill, or an ultrasonic disperser. A monomer composition is prepared. At this time, in the monomer composition, if necessary, a polyfunctional monomer, a chain transfer agent, a mold release agent, a charge control agent, a plasticizer, and other additives such as a high A molecular polymer, a dispersing agent, etc. can be added suitably.

  Next, the monomer composition is granulated by suspending it in an aqueous medium containing a dispersion stabilizer prepared in advance. At this time, the particle size distribution of the obtained toner particles can be sharpened by using a high-speed disperser such as a high-speed stirrer or an ultrasonic disperser to obtain a desired particle size all at once.

  A polymerization initiator uses together 2 or more types of polymerization initiators containing a peroxy dicarbonate type polymerization initiator at least. These polymerization initiators may be added simultaneously with mixing other additives in the polymerizable monomer, or may be mixed immediately before suspending in the aqueous medium. Moreover, it can also be added in the state melt | dissolved in the polymerizable monomer or the other solvent during granulation or after granulation completion, ie, just before starting a polymerization reaction.

Thereafter, the obtained suspension is subjected to a polymerization reaction while being stirred to such an extent that the particle state is maintained using a normal stirrer and no particle floating or sedimentation occurs. After the polymerization reaction, it is filtered by a known method, washed and then dried. Thus, the suspension polymerization method toner of the present invention is obtained.
The peroxydicarbonate polymerization initiator has a chemical structure represented by the following general formula (1), and the 10-hour half-life temperature is in the range of approximately 40 to 50 ° C., depending on the type of alkyl group (R). It is almost constant. This is considered to be due to the influence of the oxygen atom (O) adjacent to the alkyl group (R).

  In general, in order to obtain a low molecular weight polymer, in addition to the method of adding a chain transfer agent as described above, a method of using a large amount of a polymerization initiator or raising the polymerization temperature is used. When an oxydicarbonate-based polymerization initiator is used, the molecular weight can be easily reduced even in a relatively small amount and under mild polymerization conditions.

  In general, when polymerization is performed in combination with a plurality of polymerization initiators, the resulting polymer exhibits an intermediate molecular weight distribution with respect to the molecular weight distribution when each polymerization initiator is used alone. It is common. However, when the polymerization is carried out in combination with a peroxydicarbonate polymerization initiator and other polymerization initiators, the mechanism of action is not clear, but the resulting polymer is the peroxydicarbonate polymerization initiator. It has been clarified that the polymer component having a plurality of distributions exhibits a unique molecular weight distribution due to the polymer component derived from the polymer component and the polymer component derived from the other polymerization initiator used in combination.

  Here, the low molecular weight polymer component can be easily formed by using a peroxydicarbonate polymerization initiator as described above. On the other hand, in order to form a high molecular weight polymer component, the coexisting polymerization initiator has at least a 10-hour half-life temperature higher than that of the peroxydicarbonate-based polymerization initiator, At least one of them preferably has a 10-hour half-life temperature difference of 10 to 50 ° C. If the 10-hour half-life temperature of the coexisting polymerization initiator is lower than the above range, the molecular weight of the high molecular weight component cannot be sufficiently increased, and the effect of improving the high temperature offset resistance cannot be obtained. In addition, if the 10-hour half-life temperature of the coexisting polymerization initiator is higher than the above range, the utilization efficiency of the polymerization initiator is reduced, and the effect of improving either the low-temperature fixability or the high-temperature offset resistance is impaired. There may be a problem in that the unreacted polymerizable monomer tends to remain in the polymer particles after completion of the reaction.

  Therefore, according to the present invention, by performing suspension polymerization in the presence of two or more kinds of polymerization initiators as described above, including at least a peroxydicarbonate polymerization initiator, low molecular weights having different molecular weight distributions from each other. Polymer particles containing a component and a high molecular weight component can be easily obtained.

  In addition, when the peroxydicarbonate-based polymerization initiator is used to form a low molecular weight polymer component, blocking and developability are deteriorated compared to the case where a general chain transfer agent is used, and the adhesion to the photoreceptor is affected. The production of very low molecular weight polymers and oligomers that affect Furthermore, the distribution state of the low molecular weight component and the high molecular weight component thus formed in the polymer particles is extremely uniform, and the dispersibility of various components such as the colorant, the charge control agent, and the wax is not impaired. And other problems such as image contamination, fusion to a photosensitive member, filming, and the like do not occur. Therefore, according to the present invention, it is possible to obtain a polymerized toner having excellent durability in long-term use.

  The molecular weight distribution of the polymer particles has at least one peak or shoulder in the molecular weight region of 5000 to 20000 and at least one peak or shoulder in the molecular weight region of 50,000 to 500,000 in the GPC measurement of THF-soluble matter. It is preferable to have. That is, by controlling the molecular weight distribution of each of the low molecular weight component and the high molecular weight component within the above ranges, the low molecular weight component can improve the low temperature fixability and the high molecular weight component can improve the high temperature offset resistance. It can be expressed effectively, and it is possible to achieve both the low-temperature fixability and the high-temperature offset resistance which are the objects of the present invention.

  Further, according to the present invention, depending on the kind of the polymerization initiator combined with the peroxydicarbonate polymerization initiator, an appropriate THF-insoluble component can be formed in the binder resin constituting the toner. This is considered to be manifested by the entanglement of the formed low molecular weight component and high molecular weight component uniformly, thereby further improving the high temperature offset resistance of the toner. Further, the THF-insoluble matter formed in this way has a pseudo-crosslinked structure in which the end of the polymer chain does not have a chemical bond, and the toner using this binder resin is used in the above-mentioned film fixing system. However, since the toner particles are easily deformed by heating, it is easy for the wax to ooze out and the low-temperature fixability is not hindered. Further, in the present invention, for the purpose of further promoting the effect of improving the high temperature offset resistance, for example, the amount of THF insolubles formed can be reduced by adding a small amount of a polyfunctional monomer to the monomer composition. It can also be increased. In this case, the preferable amount of THF-insoluble matter is 5 to 30 parts by mass per 100 parts by mass of the resin component. When the THF-insoluble content is less than 5 parts by mass, the effect of promoting high-temperature offset resistance cannot be obtained, and when the THF-insoluble content exceeds 30 parts by mass, the improvement effect on low-temperature fixability is significantly impaired.

  As described above, the present invention seeks to achieve both low-temperature fixability and high-temperature offset resistance by a new action and effect expressed by the combination of a polymerization initiator having a specific structure and another polymerization initiator. It is impossible to achieve the object of the present invention simply by combining polymerization initiators having different half-temperatures for 10 hours, and a polyfunctional polymerization initiator, a monofunctional polymerization initiator, This is different from the conventional technique in which improvement is achieved by the combined use of the above-mentioned or by simply adjusting the balance between the molecular weight adjusting action by the chain transfer agent and the crosslinking reaction by the polyfunctional monomer.

  As described above, according to the present invention, it is possible to realize a polymerized toner having both good low-temperature fixability and high-temperature offset resistance.

  Here, molecular weight distribution and peak molecular weight by gel permeation chromatography (GPC) can be measured as follows.

First, the sample toner is immersed in THF, extracted so that the concentration of the resin component is 0.05 to 0.6 parts by mass, and this extract is filtered through a solvent-resistant membrane filter having a pore size of 0.5 μm. A sample solution is used. Next, the column is stabilized in a heat chamber at 40 ° C., THF is passed through the column at this temperature at a flow rate of 1 ml / min, and 50 to 200 μl of the sample solution is injected and measured. In measuring the molecular weight of a sample, the molecular weight distribution of the sample is calculated from the relationship between the logarithmic value of a calibration curve prepared from several monodisperse polystyrene standard samples and the number of counts. As a standard polystyrene sample for preparing a calibration curve, for example, Pressure Chemical Co. Or Tosoh molecular weights of 6 × 10 ² , 2.1 × 10 ³ , 4 × 10 ³ , 1.75 × 10 ⁴ , 5.1 × 10 ⁴ , 1.1 × 10 ⁵ , 3.9 × 10 ^It is appropriate to use a standard polystyrene sample of at least about 10 points, using samples of ⁵ , 8.6 × 10 ⁵ , 2 × 10 ⁶ , 4.48 × 10 ⁶ . An RI (refractive index) detector is used as the detector. In addition, as a column, in order to qualitatively measure the molecular weight region of 10 ³ to 2 × 10 ⁶ , it is preferable to combine a plurality of commercially available polystyrene gel columns. In the present invention, measurement is performed under the following conditions.

GPC measurement condition equipment: HLC-8120GPC (manufactured by Tosoh Corporation)
Column: KF801, 802, 803, 804, 805, 806, 807
(Made by Shodex)
Column temperature: 40 ° C
solv. : THF

  The amount of THF insoluble matter can be measured as follows.

First, the sample toner is weighed and placed in a cylindrical filter paper (for example, No. 86R manufactured by Toyo Roshi Kaisha, Ltd., size 28 × 100 mm), and this is inserted into a Soxhlet extractor. Using 200 ml of THF as an extraction solvent, extraction is performed for 20 hours at a reflux rate such that the extraction cycle of THF is about once every 4 to 5 minutes. After completion of the extraction, the cylindrical filter paper is taken out and dried, and the THF-insoluble matter is calculated by weighing the remaining toner mass. When the toner contains an insoluble component such as a magnetic substance or a pigment other than the resin component, the mass of the toner put in the cylindrical filter paper is W1, and the mass of the extracted THF-soluble resin component is W2. When the mass of the THF-insoluble component other than the resin component contained in the toner is W3, the THF-insoluble content of the resin component in the toner is calculated using the following formula (1).
Formula (1)
THF insoluble matter (mass%) = [(W1- (W3 + W2)) / (W1-W3)] × 100

  Examples of the polymerizable monomer used in the present invention include styrene monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, p-ethylstyrene, and acrylic acid. Methyl, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, n-propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, acrylic acid Acrylic esters such as phenyl, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, methacrylic acid Stearyl, Methacrylic acid phenyl, dimethylaminoethyl methacrylate, methacrylic acid esters such as diethylaminoethyl methacrylate, other, acrylonitrile, methacrylonitrile, and monomers such as acrylamide.

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

  The peroxydicarbonate-based polymerization initiator used in the present invention includes di-n-propyl peroxydicarbonate, di-n-butyl peroxydicarbonate, di-n-pentyl peroxydicarbonate, diisopropyl peroxy Dicarbonate, di-sec-butyl peroxydicarbonate, di (2-ethylhexyl) peroxydicarbonate, di (2-ethoxyethyl) peroxydicarbonate, di (3-methoxybutyl) peroxydicarbonate, di ( 4-t-butylcyclohexyl) peroxydicarbonate and the like.

  The polymerization initiator coexisting with the peroxydicarbonate polymerization initiator used in the present invention is not particularly limited, and a known peroxide polymerization initiator or azo polymerization initiator can be used.

  As the peroxide polymerization initiator, as the diacyl peroxide polymerization initiator, diisobutyryl peroxide, diisononanoyl peroxide, di-n-octanoyl peroxide, dilauroyl peroxide, distearoyl peroxide, Examples thereof include dibenzoyl peroxide, di-m-toluoyl peroxide, and benzoyl-m-toluoyl peroxide.

  Further, as peroxy ester polymerization initiators, t-butyl peroxylaurate, t-butyl peroxyneodecanoate, t-butyl peroxypivalate, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxyisobutyrate, t-butyl peroxyacetate, t-butyl peroxyisononanoate, t-butyl peroxybenzoate, t-amyl peroxyneodecanoate, t-amyl peroxypivalate, t-amylperoxy-2-ethylhexanoate, t-amylperoxyacetate, t-amylperoxyisononanoate, t-amylperoxybenzoate, t-hexylperoxyneodecanoate, t-hexylper Oxypivalate, t-hexylperoxy-2-ethylhe Sanoate, t-hexylperoxybenzoate, α-cumylperoxyneodecanoate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, 1,1,3,3-tetramethyl Butyl peroxyneodecanoate, 1-cyclohexyl-1-methylethylperoxyneodecanoate, 2,5-dimethyl-2,5-bis (2-ethylhexanoylperoxy) hexane, 2,5-dimethyl -2,5-bis (benzoylperoxy) hexane, t-butylperoxy-3,5,5-trimethylhexanoate, 2,5-dimethyl-2,5-bis (m-toluoylperoxy) hexane Etc.

  Other peroxy monocarbonates such as t-hexyl peroxyisopropyl monocarbonate, t-butyl peroxyisopropyl monocarbonate, t-butyl peroxy 2-ethylhexyl monocarbonate, t-butyl peroxyallyl monocarbonate, 1,1 -Di-t-hexylperoxycyclohexane, 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane, 1,1-di-t-butylperoxycyclohexane, 2,2-di- Examples include peroxyketals such as t-butylperoxybutane, dialkyl peroxides such as dicumyl peroxide, di-t-butyl peroxide, and t-butylcumyl peroxide.

  As the azo polymerization initiator, 2,2′-azobis- (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexane-1-carbonitrile) ), 2,2′-azobis-4-methoxy-2,4-dimethylvaleronitrile, azobisisobutyronitrile and the like.

  Among these polymerization initiators, peroxide-based polymerization initiators are preferable because there is little residue of decomposition products. The 10-hour half-life temperature is preferably higher than that of the peroxydicarbonate-based polymerization initiator and the difference is 50 ° C. or less. That is, those having a 10-hour half-life temperature of approximately 50 to 100 ° C. are suitable. Examples of the polymerization initiator satisfying such conditions include a diacyl peroxide polymerization initiator and a peroxyester polymerization initiator, and a diacyl peroxide polymerization initiator is particularly preferably used.

  Moreover, in this invention, a chain transfer agent can be used as needed. Specific examples include n-pentyl mercaptan, isopentyl mercaptan, 2-methylbutyl mercaptan, n-hexyl mercaptan, n-heptyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, t-nonyl mercaptan, n-dodecyl mercaptan, Alkyl mercaptans such as t-dodecyl mercaptan, n-tetradecyl mercaptan, t-tetradecyl mercaptan, n-pentadecyl mercaptan, n-hexadecyl mercaptan, t-hexadecyl mercaptan, stearyl mercaptan, alkyl esters of thioglycolic acid , Alkyl esters of mercaptopropionic acid, halogenated hydrocarbons such as chloroform, carbon tetrachloride, ethylene bromide, carbon tetrabromide, α-methylstyrene dimer And the like.

  These chain transfer agents are not necessarily used, but a preferable addition amount when used is 0.05 to 3 parts by mass with respect to 100 parts by mass of the polymerizable monomer.

Moreover, in this invention, a small amount of polyfunctional monomers can be used together. As the polyfunctional monomer, compounds having two or more polymerizable double bonds are mainly used. For example, aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene, such as ethylene glycol diacrylate and ethylene glycol. Carboxylic acid esters having two double bonds such as dimethacrylate and 1,3-butanediol dimethacrylate, or divinyl compounds such as divinylaniline, divinyl ether, divinyl sulfide and divinyl sulfone, and more than two vinyl groups The compound which has is mentioned.
The preferable addition amount in the case of using these polyfunctional monomers together is 0.01 to 1 part by mass with respect to 100 parts by mass of the polymerizable monomer.

  As the dispersion stabilizer used in the present invention, known surfactants, organic dispersants, and inorganic dispersants can be used. Among these, inorganic dispersants can be suitably used because they are less likely to produce harmful ultra fine powders, are less likely to lose stability even when the polymerization temperature is changed, are easy to wash and do not adversely affect the toner. Examples of such inorganic dispersants include polyvalent metal phosphates such as calcium phosphate, magnesium phosphate, aluminum phosphate and zinc phosphate, carbonates such as calcium carbonate and magnesium carbonate, calcium metasuccinate, calcium sulfate and barium sulfate. And inorganic oxides such as calcium hydroxide, magnesium hydroxide, aluminum hydroxide, silica, bentonite, and alumina.

  When these inorganic dispersants are used, they may be used as they are added to the aqueous medium, but in order to obtain finer particles, the inorganic dispersant particles in the aqueous medium using a compound capable of generating the inorganic dispersant. It can also be generated and used. For example, in the case of calcium phosphate, a sodium phosphate aqueous solution and a calcium chloride aqueous solution can be mixed with high-speed stirring to produce water-insoluble calcium phosphate, which enables more uniform and fine dispersion. At the same time, water-soluble sodium chloride is by-produced. However, when a water-soluble salt is present in the aqueous medium, dissolution of the polymerizable monomer in water is suppressed, and an ultrafine particle toner by emulsion polymerization is produced. Since it becomes difficult to generate | occur | produce, it is more convenient. The inorganic dispersant can be almost completely removed by adding an acid or an alkali after the polymerization and dissolving.

  These inorganic dispersants are desirably used alone in an amount of 0.2 to 20 parts by mass with respect to 100 parts by mass of the polymerizable monomer, but if necessary, 0.001 to 0.1 parts by mass. Some surfactants may be used in combination. Examples of the surfactant include sodium dodecylbenzene sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, sodium oleate, sodium laurate, sodium stearate, potassium stearate and the like.

  As the colorant used in the present invention, known ones can be used, and examples thereof include carbon black as a black colorant, magnetic powder, and yellow / magenta / cyan colorants shown below.

  As the yellow colorant, compounds represented by condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, and allylamide compounds are used. Specifically, C.I. I. Pigment Yellow 12, 13, 14, 15, 17, 62, 74, 83, 93, 94, 95, 109, 110, 111, 128, 129, 147, 168, 180, etc. are preferably used.

  As the magenta colorant, a condensed azo compound, diketopyrrolopyrrole compound, anthraquinone, quinacridone compound, basic dye lake compound, naphthol compound, benzimidazolone compound, thioindigo compound, and perylene compound are used. Specifically, C.I. I. Pigment Red 2, 3, 5, 6, 7, 23, 48: 2, 48: 3, 48: 4, 57: 1, 81: 1, 122, 144, 146, 166, 169, 177, 184, 185, 202, 206, 220, 221, 254, etc. are preferably used.

  As the cyan colorant, copper phthalocyanine compounds and derivatives thereof, anthraquinone compounds, basic dye lake compounds, and the like are used. Specifically, C.I. I. Pigment Blue 1, 7, 15, 15: 1, 15: 2, 15: 3, 15: 4, 60, 62, 66 and the like are preferably used.

  These colorants can be used alone or in combination, and further in the form of a solid solution. When magnetic powder is used as the black colorant, the amount added is preferably 40 to 150 parts by mass with respect to 100 parts by mass of the polymerizable monomer. In the case of a color toner, it is selected from the viewpoints of hue angle, saturation, lightness, weather resistance, OHP transparency, and dispersibility in the toner, and the preferred addition amount is 100 parts by weight of the polymerizable monomer. It is 1-20 mass parts with respect to.

  When these colorants are used in suspension polymerization method toners, it is necessary to pay attention to the polymerization inhibitory property and water phase transferability of the colorant, and surface modification, for example, depending on the substance that does not inhibit polymerization. It is preferable to perform a hydrophobic treatment.

  In particular, since dye-based colorants and carbon black often have polymerization inhibiting properties, care must be taken when using them. A preferable method for surface-treating the dye-based colorant includes a method in which a polymerizable monomer is polymerized in the presence of these dyes in advance, and the obtained colored polymer is added to the monomer system. For carbon black, in addition to the same treatment as the above dye, a grafting treatment may be performed with a substance that reacts with the surface functional group of carbon black, for example, polyorganosiloxane.

  In addition, magnetic powder is mainly composed of iron oxide such as triiron tetroxide and γ-iron oxide, and since it is generally hydrophilic, it is magnetic by interaction with water as a dispersion medium. The powder tends to be unevenly distributed on the particle surface, and the resulting toner particles are inferior in fluidity and frictional charging uniformity due to the magnetic powder exposed on the surface. Therefore, the surface of the magnetic powder is preferably subjected to a hydrophobic treatment uniformly with a coupling agent. Examples of the coupling agent that can be used include a silane coupling agent and a titanium coupling agent, and a silane coupling agent is particularly preferably used.

  The toner of the present invention preferably contains a release agent in order to improve fixability. Examples of the release agent that can be used include petroleum wax such as paraffin wax, microcrystalline wax, and petrolactam and derivatives thereof, montan wax and derivatives thereof, hydrocarbon wax and derivatives thereof according to Fischer-Tropsch method, and polyethylene. Polyolefin waxes and derivatives thereof, natural waxes and derivatives thereof, such as carnauba wax and candelilla wax. Derivatives include oxides, block copolymers with vinyl monomers, graft modified products, and the like. Furthermore, fatty acids such as higher aliphatic alcohols, stearic acid and palmitic acid, or compounds thereof, acid amide waxes, ester waxes, ketones, hydrogenated castor oil and derivatives thereof, plant waxes, animal waxes and the like can also be used. These mold release agents may be used independently and may use 2 or more types together.

  Among these release agents, those having an endothermic peak of 40 to 130 ° C. by differential thermal analysis, that is, a maximum endothermic peak in the region of 40 to 130 ° C. at the time of temperature rise in a DSC curve measured by a differential differential calorimeter. What has is preferable, and what has in a 45-120 degreeC area | region is further more preferable. By having the maximum endothermic peak in the above temperature range, the mold releasability is also effectively exhibited while greatly contributing to the low temperature fixability. When the maximum endothermic peak is less than 40 ° C., the self-aggregating force of the release agent component becomes weak, and as a result, the high temperature offset resistance deteriorates. Further, exudation of the release agent is likely to occur at times other than during fixing, and the charge amount of the toner is reduced, and the durability under high temperature and high humidity is reduced. On the other hand, if the maximum endothermic peak exceeds 130 ° C., the fixing temperature becomes high and low temperature offset tends to occur, which is not preferable. Furthermore, when the toner is directly produced by the suspension polymerization method, if the maximum endothermic peak temperature is high, the release agent component mainly precipitates during granulation, and the dispersibility of the release agent decreases. Therefore, it is not preferable.

  The content of the release agent is preferably 1 to 30 parts by mass and more preferably 3 to 20 parts by mass with respect to 100 parts by mass of the binder resin. When the content of the release agent is less than 1 part by mass, a sufficient addition effect cannot be obtained and the offset suppressing effect is insufficient. On the other hand, when the amount exceeds 30 parts by mass, the long-term storage stability is deteriorated and the dispersibility of other toner materials such as a release agent and a colorant is deteriorated, resulting in a decrease in toner fluidity and image characteristics. . Further, exfoliation of the release agent component occurs other than at the time of fixing, resulting in poor durability under high temperature and high humidity.

  In addition, the toner of the present invention can be blended with a charge control agent as necessary in order to stabilize the charge characteristics. As the charge control agent, known ones can be used. However, when a toner is produced by a direct polymerization method, a charge control agent having a low polymerization inhibition property and substantially free from a solubilized product in an aqueous dispersion medium is used. Particularly preferred. Specific compounds include, as negative charge control agents, metal compounds of aromatic carboxylic acids such as salicylic acid, alkyl salicylic acid, dialkyl salicylic acid, naphthoic acid and dicarboxylic acid, metal salts or metal complexes of azo dyes or azo pigments, Examples thereof include a polymer compound having a sulfonic acid or carboxylic acid group in the side chain, a boron compound, a urea compound, a silicon compound, and a calixarene. Examples of positive charge control agents include quaternary ammonium salts, polymer compounds having quaternary ammonium salts in the side chain, guanidine compounds, nigrosine compounds, and imidazole compounds.

  The amount of use of these charge control agents is determined by the toner production method including the type of binder resin, the presence or absence of other additives, and the dispersion method, and is not uniquely limited. Preferably, it is used in the range of 0.1 to 10 parts by mass, more preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the binder resin.

  Further, when a toner is produced by a suspension polymerization method, the polymerization may be carried out by adding a resin to the monomer composition described above. For example, the monomer is water-soluble and has a hydrophilic group such as an amino group, a carboxyl group, a hydroxyl group, a glycidyl group, or a nitrile group that cannot be used because it dissolves in an aqueous suspension and causes emulsion polymerization. When it is desired to introduce a monomer component into the toner, the copolymer may be in the form of a random copolymer, a block copolymer, a graft copolymer, or the like of these and a vinyl compound such as styrene or ethylene, or a polyester, polyamide, or the like. It can be used in the form of a polyaddition polymer such as a polycondensate, polyether or polyimine. By coexisting such a high molecular polymer containing a polar functional group in the toner, the wax component described above can be easily phase-separated and the encapsulation becomes stronger, so that a toner having good blocking resistance and developability can be obtained. Obtainable.

  As addition amount of these resin, 1-20 mass parts is preferable with respect to 100 mass parts of polymerizable monomers. If the amount is less than 1 part by mass, the effect of addition is small.

  The toner of the present invention is preferably externally added with a fluidity improver to improve image quality. As the fluidity improver, inorganic fine powders such as silicate fine powder, titanium oxide, and aluminum oxide are preferably used. These inorganic fine powders are preferably hydrophobized with a hydrophobizing agent such as a silane coupling agent, silicone oil or a mixture thereof.

  The toner of the present invention can be used as it is as a one-component developer or as a two-component developer by mixing with a magnetic carrier. When used as a two-component developer, the average particle size of the carrier to be mixed is preferably 10 to 100 μm, and the toner concentration in the developer is preferably 2 to 15 parts by mass.

  The average circularity of the toner obtained by the present invention is preferably 0.970 or more. The average circularity is an index representing the degree of unevenness of toner particles, and is 1.000 when the toner is a perfect sphere, and the value becomes smaller as the surface shape becomes more complicated. That is, that the average circularity is 0.970 or more means that the toner shape is substantially spherical. The toner having such a shape is likely to be uniformly charged, and is effective in suppressing fog and sleeve ghost. Further, since the toner ears formed on the toner carrier are uniform, control in the developing unit is facilitated. Furthermore, since it has a spherical shape, it has good fluidity and is not easily stressed in the developing device, so that the chargeability is not easily lowered even when used for a long time under high humidity. Further, since heat and pressure are easily applied to the entire toner even at the time of fixing, it contributes to improvement of fixing properties.

  The average circularity in the present invention is used as a method for quantitatively expressing the shape of the particles. The average circularity is measured using a flow type particle image analyzer “FPIA-1000” manufactured by Toago Medical Electronics Co., Ltd., 3 μm This is obtained for the particle group having the equivalent circle diameter.

  Here, the average circularity (C) is obtained by calculating the circularity (Ci) of each particle according to the following equation (2), and, as shown in the following equation (3), the total circularity of all particles measured. Is divided by the total number of particles (m).

  However, in the measurement device “FPIA-1000” used in the present invention, when calculating the average circularity from the circularity of each particle, the circularity of 0.40 to 1.00 is determined according to the obtained circularity value. A method of calculating using the center value of each divided range and the frequency value at that time after the division into 61 divided ranges is used. There is very little error between the average circularity value calculated by this calculation method and the average circularity value calculated by the above-described calculation method that directly uses the circularity of each particle. Therefore, there is no problem even if such a calculation method that is partially changed is used.

  The measurement procedure is as follows.

  A dispersion is prepared by dispersing about 5 mg of sample toner in 10 ml of water in which about 0.1 mg of a surfactant is dissolved. The dispersion is subjected to ultrasonic dispersion treatment (20 KHz, 50 W) for 5 minutes, and then the dispersion. The concentration is set to 5000 to 20,000 / μl, and measurement is performed with the above-described apparatus to determine the average circularity of a particle group having a circle-equivalent diameter of 3 μm or more. In this measurement, the reason why the circularity is measured only for the particle group having an equivalent circle diameter of 3 μm or more is that the particle group of the external additive existing independently of the toner particles in the particle group having an equivalent circle diameter of less than 3 μm. This is because the degree of circularity of the toner particle group cannot be accurately estimated due to the influence thereof.

  The weight average particle diameter of the toner obtained by the present invention is preferably 3 to 10 μm in order to develop finer latent image dots faithfully and obtain a high quality image. When the weight average particle size is less than 3 μm, the transfer residual toner on the photoconductor increases due to a decrease in transfer efficiency, and it becomes difficult to suppress photoconductor shaving and toner fusion in the contact charging step. In addition to an increase in the surface area of the entire toner, fluidity and agitation as a powder decrease, and it becomes difficult to uniformly charge individual toner particles. Since it tends to decrease, it is not preferable. On the other hand, if the weight average particle diameter exceeds 10 μm, the characters and the line image are likely to be scattered and it becomes difficult to obtain high resolution. Also, as the device becomes higher in resolution, the reproducibility of one dot tends to deteriorate.

  Here, the average particle size and particle size distribution of the toner can be measured using a Coulter Counter TA-II type or Coulter Multisizer (both manufactured by Coulter). In the present invention, a Coulter multisizer was used, and an interface (manufactured by Nikka) and a PC9801 personal computer (manufactured by NEC) were connected to the number distribution and volume distribution. In addition, a 1% NaCl aqueous solution prepared using primary sodium chloride was used as the electrolytic solution.

  As a measuring method, 0.1 to 5 ml of a surfactant, preferably alkylbenzene sulfonate is added as a dispersant to 100 to 150 ml of the electrolytic solution, and 2 to 20 mg of a measurement sample is further added. Next, this electrolytic solution is subjected to a dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and the volume and number of toner particles of 2 μm or more are measured using the 100 μm aperture as the aperture by the Coulter Multisizer. The number distribution is calculated. Then, the volume-based weight average particle diameter (D4) obtained from the volume distribution and the number-based length average particle diameter obtained from the number distribution, that is, the number average particle diameter (D1) are obtained.

  Next, an image forming apparatus that can suitably use the toner of the present invention will be specifically described with reference to the drawings. Here, as an example, an image forming apparatus suitable for a magnetic toner using magnetic powder as a colorant is shown.

  In FIG. 1, reference numeral 100 denotes a photosensitive drum, and a charging roller 117, a developing device 140, a transfer roller 114, a cleaner 116, a paper feed roller 124, and the like are provided around the photosensitive drum. The photosensitive drum 100 is charged to −700 V by the charging roller 117. Next, exposure is performed with laser light 123 emitted from the laser generator 121. The electrostatic latent image thus formed on the photosensitive drum 100 is developed with magnetic toner by the developing device 140. The toner image on the photoconductive drum 100 is transferred onto the transfer material by the transfer roller 114 in contact with the photoconductive drum 100 via the transfer material P. The transfer material P on which the toner image is placed is conveyed by the conveying belt 125 and fixed by the fixing device 126. Further, the toner remaining on a part of the photosensitive drum 100 is cleaned by the cleaner 116. As shown in FIG. 1, the developing device 140 is provided with a cylindrical toner carrier 102 (hereinafter referred to as a developing sleeve) made of a nonmagnetic metal such as aluminum or stainless steel in the vicinity of the photosensitive drum 100. The gap between the photosensitive drum 100 and the developing sleeve 102 is maintained at about 230 μm by a sleeve / photosensitive gap holding member (not shown) or the like. In the developing sleeve 102, a magnet roller (not shown) is disposed and fixed concentrically with the developing sleeve 102, and only the developing sleeve 102 rotates. The magnet roller is provided with a plurality of magnetic poles, and S1 contributes to development, N1 regulates the toner coat amount, S2 takes in / conveys toner, and N2 contributes to prevention of toner blowout. Further, an elastic blade is provided as a member for regulating the amount of magnetic toner that adheres to the developing sleeve 102 and is conveyed, and the amount of toner conveyed to the developing region is controlled by the contact pressure against the developing sleeve 102. . In the development region, a DC and AC development bias is applied between the photosensitive drum 100 and the developing sleeve 102, and the magnetic toner on the developing sleeve 102 flies onto the photosensitive drum 100 in accordance with the electrostatic latent image. Becomes a visible image.

  Hereinafter, although the manufacturing method of this invention is demonstrated concretely using an Example, this invention is not limited at all by these Examples.

<Example 1>
450 parts by mass of 0.1 mol / liter-Na ₃ PO ₄ aqueous solution was added to 720 parts by mass of ion-exchanged water, heated to 60 ° C. with stirring, and then 68 parts by mass of 1.0 mol / liter-CaCl ₂ aqueous solution. Was added and stirring was continued to prepare an aqueous medium containing a dispersion stabilizer composed of Ca ₃ (PO ₄ ) ₂ .

On the other hand, the following formulation was uniformly dispersed and mixed using an attritor (manufactured by Mitsui Miike Chemical Industries) to prepare a monomer composition.
Styrene: 80 parts by mass n-butyl acrylate: 20 parts by mass Saturated polyester resin (terephthalic acid-propylene oxide modified bisphenol A polycondensate, Mw: 20,000, Tg: 60 ° C., acid value: 10 mgKOH / g): 8 parts by mass Charge control agent (BONTRON (registered trademark), E-84 (Orient Chemical Co., Ltd.): 1 part by mass Hydrophobic magnetic iron oxide: 80 parts by mass

  The monomer composition was heated to 60 ° C., and 10 parts by mass of styrene-modified paraffin wax (maximum value of endothermic peak in DSC: 74 ° C.) was added and mixed and dissolved.

  Next, as a polymerization initiator, 3 parts by mass of di-sec-butyl peroxydicarbonate (peroxydicarbonate system, 10-hour half-life temperature: 51 ° C.) and distearoyl peroxide (diacyl peroxide system, 10-hour half) (Phase temperature: 62 ° C.) 2 parts by mass were mixed and further added and dissolved in the monomer composition.

  This was put into the aqueous medium, and granulated by stirring for 15 minutes at 10,000 rpm in a nitrogen atmosphere at 60 ° C. using CLEARMIX (M Technique Co., Ltd.).

  Further, polymerization was performed at 70 ° C. for 10 hours while stirring the obtained suspension with a paddle stirring blade. After completion of the reaction, the suspension was cooled and hydrochloric acid was added to dissolve the dispersion stabilizer, followed by filtration, washing with water and drying to obtain polymer particles.

Thereafter, a hydrophobic silica fine powder treated with hexamethyldisilazane and silicone oil and having a primary particle size of 12 nm and a BET specific surface area of 120 m ² / g was prepared. 1 part by mass of silica fine powder was added and mixed using a Henschel mixer (manufactured by Mitsui Miike Chemical Industries).

  Thus, a toner was produced by the production method of the present invention.

<Example 2>
450 parts by mass of 0.1 mol / liter-Na ₃ PO ₄ aqueous solution was added to 720 parts by mass of ion-exchanged water, heated to 60 ° C. with stirring, and then 68 parts by mass of 1.0 mol / liter-CaCl ₂ aqueous solution. Was added and stirring was continued to prepare an aqueous medium containing a dispersion stabilizer composed of Ca ₃ (PO ₄ ) ₂ .

On the other hand, the following formulation was uniformly dispersed and mixed using an attritor (manufactured by Mitsui Miike Chemical Industries) to prepare a monomer composition.
Styrene: 80 parts by mass n-butyl acrylate: 20 parts by mass Divinylbenzene: 0.2 parts by mass Saturated polyester resin (terephthalic acid-propylene oxide modified bisphenol A polycondensate, Mw: 20,000, Tg: 60 ° C., acid value: 10 mg KOH / g): 8 parts by mass charge control agent (BONTRON (registered trademark), E-84 (Orient Chemical Co., Ltd.): 1 part by mass hydrophobic magnetic iron oxide: 80 parts by mass

  The monomer composition was heated to 60 ° C., and 10 parts by mass of styrene-modified paraffin wax (maximum value of endothermic peak in DSC: 74 ° C.) was added and mixed and dissolved.

  Subsequently, 3 parts by mass of di (2 ethylhexyl) peroxydicarbonate (peroxydicarbonate system, 10 hour half-life temperature: 49 ° C.) and diisononanoyl peroxide (diacyl peroxide system, 10) were used as polymerization initiators. (Time half-life temperature: 61 ° C.) 2 parts by mass were mixed and further added and dissolved in the monomer composition.

  This was put into the aqueous medium, and granulated by stirring for 15 minutes at 10,000 rpm in a nitrogen atmosphere at 60 ° C. using CLEARMIX (M Technique Co., Ltd.).

  Further, polymerization was performed at 70 ° C. for 10 hours while stirring the obtained suspension with a paddle stirring blade. After completion of the reaction, the suspension was cooled and hydrochloric acid was added to dissolve the dispersion stabilizer, followed by filtration, washing with water and drying to obtain polymer particles.

Thereafter, a hydrophobic silica fine powder treated with hexamethyldisilazane and silicone oil and having a primary particle size of 12 nm and a BET specific surface area of 120 m ² / g was prepared. 1 part by mass of silica fine powder was added and mixed using a Henschel mixer (manufactured by Mitsui Miike Chemical Industries).

  Thus, a toner by the production method of the present invention was produced.

<Example 3>
In Example 1, except that 2 parts by mass of t-amyl peroxypivalate (peroxyester, 10 hour half-life temperature: 55 ° C.) was used in place of 2 parts by mass of distearoyl peroxide as a polymerization initiator. Were the same as in Example 1 to prepare the toner of the present invention.

<Example 4>
In Example 1, instead of 2 parts by mass of distearoyl peroxide, 2 parts by mass of t-butyl peroxyisononanoate (peroxyester, 10 hour half-life temperature: 102 ° C.) was used as a polymerization initiator. Except for this, the toner of the present invention was produced in the same manner as in Example 1.

<Comparative Example 1>
In Example 1, a comparative toner was prepared in the same manner as in Example 1 except that 5 parts by mass of di-sec-butyl peroxydicarbonate was used alone as the polymerization initiator.

<Comparative example 2>
In Example 1, a comparative toner was prepared in the same manner as in Example 1 except that 5 parts by mass of distearoyl peroxide was used alone as a polymerization initiator.

<Comparative Example 3>
In Example 1, a toner of a comparative example was prepared in the same manner as in Example 1 except that 3 parts by mass of t-amyl peroxypivalate and 2 parts by mass of distearoyl peroxide were used as the polymerization initiator. .

<Comparative example 4>
In Example 1, 3 parts by mass of t-amyl peroxypivalate and 2 parts by mass of t-butyl peroxyisobutyrate (peroxy ester type, 10 hour half-life temperature: 82 ° C.) are used as the polymerization initiator. A comparative toner was prepared in the same manner as in Example 1 except for the above.

<Comparative Example 5>
450 parts by mass of 0.1 mol / liter-Na ₃ PO ₄ aqueous solution was added to 720 parts by mass of ion-exchanged water, heated to 60 ° C. with stirring, and then 68 parts by mass of 1.0 mol / liter-CaCl ₂ aqueous solution. Was added and stirring was continued to prepare an aqueous medium containing a dispersion stabilizer composed of Ca ₃ (PO ₄ ) ₂ .

On the other hand, the following formulation was uniformly dispersed and mixed using an attritor (manufactured by Mitsui Miike Chemical Industries) to prepare a monomer composition.
Styrene: 80 parts by mass n-butyl acrylate: 20 parts by mass Divinylbenzene: 1 part by mass t-dodecyl mercaptan: 2 parts by mass saturated polyester resin (terephthalic acid-propylene oxide modified bisphenol A polycondensate, Mw: 20,000, Tg: 60 ° C., acid value: 10 mg KOH / g): 8 parts by mass charge control agent (BONTRON (registered trademark), E-84 (Orient Chemical)): 1 part by mass hydrophobic magnetic iron oxide: 80 parts by mass The above monomer composition The product was heated to 60 ° C., and 10 parts by mass of styrene-modified paraffin wax (maximum value of endothermic peak in DSC: 74 ° C.) was added and mixed and dissolved.

  Next, 5 parts by mass of t-amyl peroxypivalate as a polymerization initiator was further added and dissolved in the monomer composition.

  This was put into the aqueous medium, and granulated by stirring for 15 minutes at 10,000 rpm in a nitrogen atmosphere at 60 ° C. using CLEARMIX (M Technique Co., Ltd.).

  Further, polymerization was performed at 70 ° C. for 10 hours while stirring the obtained suspension with a paddle stirring blade. After completion of the reaction, the suspension was cooled and hydrochloric acid was added to dissolve the dispersion stabilizer, followed by filtration, washing with water and drying to obtain polymer particles.

Thereafter, a hydrophobic silica fine powder treated with hexamethyldisilazane and silicone oil and having a primary particle size of 12 nm and a BET specific surface area of 120 m ² / g was prepared. 1 part by mass of silica fine powder was added and mixed using a Henschel mixer (Mitsui Miike Chemical Co., Ltd.). Thus, a toner of a comparative example was produced.

  In Examples 1 to 4 and Comparative Examples 1 to 5, the types of polymerization initiators used, the 10-hour half-life temperature, the number of added parts, the number of added crosslinking agents, and the number of added parts of the chain transfer agent are summarized in Table 1.

  For the evaluation of these toners, a Canon laser beam printer LBP-1760 was remodeled as an image forming apparatus, and a toner having a structure generally shown in FIG. 1 was used.

  As the fixing device, a film fixing type that does not have an oil application function and is heat-pressed with a heater through a film was used. At this time, a pressure roller having a fluororesin surface layer and a diameter of 30 mm was used. The fixing temperature was 180 ° C., and the nip width was set to 7 mm. An external fixing device having the same configuration was used for evaluating the fixing property.

Note that 75 g / m ² of paper was used as the transfer material.

  The specific evaluation method and the judgment criteria are as follows. All the evaluations were performed in a normal temperature and normal humidity environment (23 ° C., 60% RH).

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

(2) Transfer efficiency The transfer residual toner on the photosensitive drum after transferring the solid black image is taped off with Mylar tape, and this is pasted on the paper and the Macbeth density is measured. Paste the Mylar tape on the paper with the toner before fixing, measure the Macbeth density, set the value to B, paste only the Mylar tape on the unused paper, measure the Macbeth density, and measure the value. C. The transfer efficiency was approximately calculated by the following equation.
Transfer efficiency (%) = (B−A) / (B−C) × 100

The transfer efficiency obtained from the above formula was judged according to the following criteria.
A: Transfer efficiency is 96% or more B: Transfer efficiency is 92% or more and less than 96% C: Transfer efficiency is 89% or more and less than 92% D: Transfer efficiency is less than 89%

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

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

(4) Fixing property A solid image part in which the toner applied amount per unit area is adjusted to 0.7 mg / cm ² is formed, and the temperature of the fixing device is sequentially raised within a range of 130 to 230 ° C., and every 5 ° C. A fixed image was output. The obtained fixed image was rubbed and reciprocated 5 times with sylbon paper applied with a load of 4.9 kPa (50 g / cm ² ), and the temperature at which the reduction rate of the image density before and after the rub was 10% or less It was. The high temperature offset temperature was evaluated by visually observing the presence or absence of stains on the non-image area on the fixed image surface and the back of the paper.

  Table 2 summarizes the physical property values of the toners produced in Examples 1 to 4 and Comparative Examples 1 to 5. Table 3 shows the evaluation results of the fixing properties and the evaluation results of image density, transfer efficiency, and fog after performing the image printing endurance test for 2000 sheets with an image pattern consisting of only a horizontal line with a printing rate of 2%. Are shown together.

  As shown in Table 2, the toner of the present invention using both a peroxydicarbonate-based polymerization initiator and another polymerization initiator exhibits a molecular weight distribution having peaks on the low molecular weight side and the high molecular weight side, respectively. I understood it. However, when the 10-hour half-life temperature of the polymerization initiator used in combination as in the toner of Example 3 was relatively low, the peak molecular weight on the high molecular weight side tended to be small. In addition, when the 10-hour half-life temperature of the polymerization initiator used in combination as in the toner of Example 4 is high, only a small amount of the high molecular weight component was observed, and the utilization efficiency of the polymerization initiator decreased. It was suggested that

  On the other hand, none of the toners of the comparative examples showed a plurality of peaks in the molecular weight distribution. As a matter of course, the toners of Comparative Example 1, Comparative Example 2 and Comparative Example 5 in which the polymerization initiator is used alone are used. In the toners of Comparative Example 3 and Comparative Example 4, two kinds of polymerization initiators are used in combination. Nevertheless, multiple peaks were not observed. From this, when a polymerization initiator other than a peroxydicarbonate-based polymerization initiator is combined, or when only a polymerization initiator having a different 10-hour half-life temperature is used in combination, the molecular weight distribution as in the present invention is used. It has become clear that it is not possible to obtain a toner having a toner, and it is necessary to use at least a peroxydicarbonate-based polymerization initiator.

  Further, as shown in Table 3, it was found that the toners of the present invention are both excellent in low temperature fixability and high temperature offset resistance and have a wide fixing area. Further, the image characteristics after the image printing endurance test were also good. As is apparent from Example 1 and Example 2, the high temperature offset resistance can be more effectively expressed by selecting a polymerization initiator having an appropriate 10-hour half-life temperature as the polymerization initiator used in combination. Furthermore, it has been found that the formation of THF-insoluble matter by adding a small amount of a crosslinking agent is also effective in promoting the improvement effect of high temperature offset resistance.

  In contrast, although the toner of Comparative Example 1 is excellent in low-temperature fixability, high-temperature offset occurs early, and the toner of Comparative Example 2 is excellent in high-temperature offset resistance, but the low-temperature fixability is remarkably deteriorated. In both cases, the fixing area was narrow. In either case, the deterioration of the image characteristics after the durability test was significant. In addition, when a polymerization initiator other than the peroxydicarbonate-based polymerization initiator is combined as in the toner of Comparative Example 3, or as in the toner of Comparative Example 4, a polymerization initiator having a different 10-hour half-life temperature is simply different. It has been found that a toner having a wide fixing area as in the present invention cannot be obtained only by using together.

1 is a diagram illustrating an example of an image forming apparatus used in an embodiment of the present invention.

Explanation of symbols

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

Claims (5)

A method for producing a polymerized toner comprising a step of polymerizing a monomer composition containing at least a polymerizable monomer and a colorant to obtain polymer particles, wherein the polymerization is at least a peroxydicarbonate polymerization initiator. And two or more polymerization initiators including other polymerization initiators. In the molecular weight distribution by gel permeation chromatography (GPC) measurement of tetrahydrofuran (THF) soluble matter, the two or more polymerizations A method for producing a polymerized toner, wherein polymer particles having at least one peak or shoulder on each of a low molecular weight side and a high molecular weight side , which are produced by polymerization with an initiator, are obtained.   The polymerization initiator that coexists with the peroxydicarbonate polymerization initiator has a 10-hour half-life temperature higher than that of the peroxydicarbonate polymerization initiator, and at least one of them is The method for producing a polymerized toner according to claim 1, wherein the difference in 10-hour half-life temperature is in the range of 10 to 50 ° C.   The polymerization toner according to claim 2, wherein at least a diacyl peroxide polymerization initiator and / or a peroxyester polymerization initiator is used as a polymerization initiator to coexist with the peroxydicarbonate polymerization initiator. Manufacturing method.   The polymer particles have at least one peak or shoulder in a molecular weight region of 5000 to 20000 and at least one peak or shoulder in a molecular weight region of 50,000 to 500,000 in the molecular weight distribution measured by GPC measurement of THF-soluble matter. The method for producing a polymerized toner according to any one of claims 1 to 3, wherein:   The method for producing a polymerized toner according to any one of claims 1 to 4, wherein the THF insoluble content of the resin component in the polymer particles is 5 to 30 parts by mass per 100 parts by mass of the resin component.

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