JP6331640B2 - Image forming method - Google Patents

Description

  The present invention relates to an image forming method.

  In an electrophotographic image forming method, a printed material is generally manufactured through the following steps. First, an electrostatic latent image is formed on the photosensitive member by irradiating the photosensitive member with exposure light, and the latent image is developed by supplying toner to the photosensitive member on which the electrostatic latent image is formed. Form. Next, the toner image on the photosensitive member is transferred to an image support such as paper, and the transferred toner image is heated and melted to fix the toner image to the image support to produce a printed matter. Then, the toner remaining on the photoconductor to which the toner image has been transferred is removed by a cleaning device, and the photoconductor from which the residual toner has been removed is charged, so that the next image can be formed.

  In recent years, from the viewpoint of energy saving, development of low-temperature fixing toner that achieves low energy fixing in a fixing process with the highest energy usage rate has been actively promoted in electrophotographic copying machines and printers in general. Particularly in the production print area, in addition to the above, speeding up, improvement and stabilization of image quality, and improvement in productivity by expanding compatible models are required. Toners are required to have improved low-temperature fixing properties and high-temperature offset properties, which are higher than conventional ones, for lowering the energy of fixing, expanding the corresponding paper types, and increasing the speed.

  In order to lower the toner fixing temperature, it is necessary to lower the melting start temperature and the melt viscosity of the binder resin in the toner. However, if the glass transition point and molecular weight of the binder resin are lowered in order to lower the melting temperature and melt viscosity of the binder resin, new problems arise, such as a reduction in heat-resistant storage stability and fixing separation performance of the toner.

  In order to achieve both low-temperature fixability and heat-resistant storage stability, a technique for controlling the toner into a core-shell structure has been proposed (see, for example, Patent Document 1). In other words, a technology that achieves both low-temperature fixability and heat-resistant storage stability by forming a shell layer made of particles with high glass transition point and softening point and excellent heat resistance on the surface of core particles with excellent low-temperature fixability has been proposed. ing. Particularly in the production of toner by the emulsion aggregation method, there is an advantage that such shape control and function improvement can be easily performed. In recent years, however, in the production print area, the speed of copying machines and printers has increased, and the number of compatible paper types has increased. With the toner of the core-shell structure, both low-temperature fixing and heat storage stability and fixing separation performance are compatible. It has become difficult.

  In order to solve this problem, a toner using a polyester resin for the shell layer has been proposed (see, for example, Patent Document 2). Polyester resin has the advantage that it can be easily designed to have a low softening point while maintaining a high glass transition point (Tg) compared to styrene-acrylic resin, and styrene-acrylic resin is used as the core binder resin. By using a polyester resin for the shell layer, the low-temperature fixability and heat-resistant storage stability can be improved due to the sharp melt property of the polyester resin.

  In addition, in order to prevent the paper from being wound around the fixing device due to a decrease in fixing separation performance, an image forming method using a fixing device that rapidly cools and separates the paper discharged from the nip portion by air blowing or the like has been proposed ( For example, see Patent Document 3). By the image forming method using this fixing device, it is possible to achieve both low-temperature fixability and fixing separation performance.

JP 2005-221933 A JP 2013-33233 A JP 2011-242429 A

  However, in the image forming method using the fixing device that rapidly cools the paper discharged from the nip portion, if the polyester resin that can easily design the softening point is used as the toner, the rubbing fixing property of the halftone image is poor. There arises a new problem that the output paper is easily stained.

  Therefore, the present invention shows an excellent low-temperature fixability in an image forming method using a fixing device having a cooling means for separating paper from a heating member, and improves the problem of rubbing and fixing of halftone images and paper stains. An object of the present invention is to provide an image forming method excellent in thin paper separation.

  As a result of intensive studies in view of the above problems, the present inventors have found that the above object is achieved by the following configuration.

1. A heating member that heats the paper carrying the toner image, a pressure member that fixes the image on the paper by abutting the nip that sandwiches the paper carrying the toner image against the heating member, and discharging from the nip An image forming method using a fixing device having cooling means for cooling the sheet to be separated and separating the sheet from the heating member,
The toner for forming the toner image contains a binder resin containing at least a polyester resin, and contains a saturated aliphatic dicarboxylic acid as a carboxylic acid component of a raw material monomer constituting the polyester resin,
The image forming method, wherein the polyester resin has a number average molecular weight of 4,000 to 7,000 , a main peak molecular weight of 7,000 to 12,000, and a main peak molecular weight of the toner of 11,000 or more.

  2. 2. The image forming method according to 1, wherein the polyester resin includes a styrene-acrylic modified polyester resin in which a styrene-acrylic copolymer segment is bonded to an end of a polyester segment.

  3. 3. The image forming method according to 2, wherein a content ratio of the styrene-acrylic copolymer segment in the styrene-acrylic modified polyester resin is 5 to 30% by mass.

  4). The image forming method according to any one of claims 1 to 3, wherein the cooling unit is a unit that cools the sheet by blowing air from a discharge port to the sheet discharged from the nip portion.

  According to the present invention, in an image forming method using a fixing device having a cooling unit that separates paper from a heating member, toner containing polyester resin is used, and the number average molecular weight and main peak molecular weight of the polyester resin are controlled to predetermined values. Further, by controlling the main peak molecular weight of the toner to a predetermined value, the rubbing and fixing properties can be improved, and the paper stain can be reduced. In addition, by using saturated aliphatic dicarboxylic acid as a carboxylic acid component in the raw material monomer constituting the polyester resin, it is possible to prevent a decrease in low-temperature fixability associated with high molecular weight design, thus exhibiting excellent low-temperature fixability. In addition, it is possible to solve the problem of deterioration in rubbing and fixing properties of halftone images and paper contamination.

1 is an overall configuration diagram of an image forming apparatus used in an embodiment of the present invention. 1 is an enlarged cross-sectional view of a fixing device in an image forming apparatus used in an embodiment of the present invention.

  The present invention includes a heating member that heats a sheet carrying a toner image, a pressure member that fixes an image on the sheet by contacting a nip portion sandwiching the sheet carrying the toner image with the heating member, And a cooling unit that cools the paper discharged from the nip portion and separates the paper from the heating member. In the image forming method using the fixing device, the toner that forms the toner image contains at least a polyester resin. As a raw material monomer constituting the polyester resin, a saturated aliphatic dicarboxylic acid is contained as a carboxylic acid component, the polyester resin has a number average molecular weight of 4,000 to 7,000, and a main peak molecular weight of 7 , 12,000 to 12,000, and the toner has a main peak molecular weight of 11,000 or more.

  Since the amount of toner adhering to a half-tone image on thin paper rough paper is small, when the paper carrying the toner image is heated, the thermal energy applied to the periphery of the toner particles present on the uneven portion of the paper is excessive or insufficient Is likely to occur. In particular, in the boundary region between the convex portions or the concave and convex portions, the thermal energy is excessive and the hot offset phenomenon is likely to occur. This phenomenon is remarkable in a toner containing a polyester resin designed to have a low softening point for the purpose of low-temperature fixing.

  In the above hot offset phenomenon in the toner containing the polyester resin, the toner is greatly deformed, and immediately after passing through the fixing nip portion, it is easy to take a protruding shape that is extended in a convex shape. In addition, in a fixing device equipped with a paper cooling device such as an air separation system for the purpose of expanding the types of paper to be applied, a toner containing a polyester resin is quickly cooled because the toner shape is not recovered elastically. In the halftone image formed by (1), the toner shape has a shape of extending protrusion.

  The present inventors have found that the formation of the above-described stretched-protruding components causes the toner to have a shape that is easily destroyed due to rubbing deterioration, which is a cause of lower rubbing fixability in a halftone image. I found it. Further, it has been found that the stretched component is destroyed by rubbing deterioration caused by a paper transport roller, a static elimination brush, etc., thereby contaminating the paper transport member in the machine and causing the output paper to become dirty.

  In order to improve the rubbing fixability and eliminate the stain on the output paper, it is considered necessary to suppress the occurrence of the hot offset phenomenon even in the halftone image on the thin paper rough paper. In the toner containing a polyester resin designed to have a low softening point for the purpose of low-temperature fixing, the above-described hot offset phenomenon tends to occur more remarkably, so that the melt viscosity of the toner is higher than that contained in the polyester resin. Reduction of low low molecular weight components was studied. As a result, the number average molecular weight of the polyester resin contained in the toner is controlled in the range of 4,000 to 7,000, the main peak molecular weight is in the range of 7,000 to 12,000, and the main peak molecular weight of the toner is 11,000 or more. It has been found that the toner viscosity corresponding to the excess thermal energy application portion is raised by controlling the temperature to improve the rubbing fixability and solve the problem of paper stains associated with the hot offset phenomenon. In addition, by introducing saturated aliphatic dicarboxylic acid as a raw material monomer constituting the polyester resin, the glass transition temperature (Tg) and softening point (Tm) are increased with the above-mentioned molecular weight design, and low temperature fixing is performed. It can suppress that property falls. That is, by introducing a saturated aliphatic dicarboxylic acid, the polyester resin can have a high molecular weight, and while maintaining the viscoelasticity at the time of melting, the glass transition temperature and the softening point can be lowered, so that both low temperature fixability can be achieved. it can.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may be different from the actual ratios.

<Toner for electrostatic image development>
The toner (toner for developing an electrostatic image) used in the present invention contains at least a binder resin containing a polyester resin. Preferably, a release agent, a colorant, a charge control agent, and an external additive are further included.

[Binder resin]
<Polyester resin>
The toner used in the present invention contains at least a polyester resin as a binder resin. The polyester resin may be a crystalline polyester resin, an amorphous polyester resin, or a combination thereof. Moreover, the said polyester resin may also contain the styrene-acryl modified polyester resin mentioned later. The polyester resin is produced, for example, by a polycondensation reaction using a carboxylic acid component (polyvalent carboxylic acid component) and a polyhydric alcohol component as raw materials in the presence of an appropriate catalyst.

  The content of the polyester resin in the binder resin is not particularly limited, but is preferably 5 to 50% by mass and more preferably 10 to 30% by mass with respect to the total amount of the binder resin. When the content of the polyester resin is 5% by mass or more with respect to the total amount of the binder resin, the low-temperature fixability is excellent. Further, when the core of the core-shell toner is formed using a polyester resin, sufficient storage as a function of the shell can be obtained. If the content of the polyester resin is 50% by mass or less, it is preferable in terms of thin paper separability. In addition, when a shell layer of a toner having a core-shell structure is formed, the meltability with the core particle component is high, and excellent fixability can be obtained.

  In the present invention, the number average molecular weight (Mn) of the polyester resin contained in the toner is 4,000 to 7,000, preferably 4,500 to 6,500. When the number average molecular weight of the polyester resin is less than 4,000, it is difficult to obtain a suitable cohesive force as the whole binder resin, and a hot offset phenomenon is likely to occur during fixing. For this reason, when an image is formed with a toner containing a polyester resin using a fixing device equipped with a paper cooling device, the half-tone image cannot be sufficiently rub-fixed, and the output paper is likely to be stained. On the other hand, when the number average molecular weight exceeds 7,000, it is difficult to obtain sufficient melting and to secure a sufficient minimum fixing temperature. Moreover, since the content of the terminal carboxyl group is relatively small, it is difficult to prepare the resin dispersion. When the toner contains two or more types of polyester resins, the number average molecular weight of at least one type of polyester resin may be in the above range. Here, the value calculated | required by the method as described in the below-mentioned Example shall be employ | adopted for the number average molecular weight of a polyester resin.

  Moreover, the main peak molecular weight (Mp) of the said polyester resin is 7,000-12,000, Preferably it is 7,500-11,000. When the main peak molecular weight of the polyester resin is less than 7,000, the melt viscosity of the toner becomes low, and a hot offset phenomenon tends to occur during fixing. For this reason, the rubbing and fixing property of the halftone image is not sufficiently obtained, and the output paper is easily stained. On the other hand, when the main peak molecular weight exceeds 12,000, it is difficult to obtain sufficient melting and to secure a sufficient minimum fixing temperature. Moreover, since the content of the terminal carboxyl group is relatively small, it is difficult to prepare the resin dispersion. When the toner contains two or more types of polyester resins, the main peak molecular weight of at least one type of polyester resin may be in the above range. Here, the value calculated | required by the method as described in the below-mentioned Example shall be employ | adopted for the main peak molecular weight of a polyester resin.

  The number average molecular weight or main peak molecular weight of the polyester resin can be adjusted, for example, by controlling the pressure during the reaction and the reaction time when preparing the polyester resin. For example, the molecular weight increases as the pressure and reaction time during the reaction for preparing the polyester resin increase.

  In the present invention, the polyester resin contained in the toner contains saturated aliphatic dicarboxylic acid as the carboxylic acid component of the raw material monomer. When the toner contains two or more kinds of polyester resins, it is sufficient that saturated aliphatic dicarboxylic acid is contained as a carboxylic acid component of the raw material monomer of at least one kind of polyester resin. The polyester resin may further contain other polyvalent carboxylic acid as a carboxylic acid component together with the above saturated aliphatic dicarboxylic acid as a raw material monomer.

  Examples of saturated aliphatic dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, 1,11-undecane. Linear saturation such as dicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,13-tridecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,16-hexadecanedicarboxylic acid, 1,18-octadecanedicarboxylic acid Aliphatic dicarboxylic acids; saturated aliphatic dicarboxylic acids having side chains such as methylmalonic acid, methylsuccinic acid, ethylsuccinic acid, octylsuccinic acid, methylglutaric acid, β-methyladipic acid; cyclohexanedicarboxylic acid, camphoric acid And alicyclic saturated aliphatic dicarboxylic acids. At this time, it is preferable to use a straight-chain saturated aliphatic dicarboxylic acid in which two COOH groups are bonded to both ends of the carbon chain. These saturated aliphatic dicarboxylic acids may be used alone or in combination of two or more.

  Preferably, the saturated aliphatic dicarboxylic acid suppresses an increase in the glass transition temperature accompanying the molecular weight design, and when used as a material for the shell layer of the core-shell structure toner particle, it is compatible with the resin used for the core particle. It is preferable to use a saturated aliphatic dicarboxylic acid having 4 to 12 carbon atoms because a shell layer can be produced efficiently due to easy dissolution balance. Here, the carbon number is the number of carbon atoms including carbons belonging to two carboxyl groups.

  The saturated aliphatic dicarboxylic acid used in the present invention has 4 to 12 carbon atoms, such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid. Linear saturated aliphatic dicarboxylic acids can be used particularly preferably.

  The ratio of the saturated aliphatic dicarboxylic acid in the total carboxylic acid to be used is preferably 15 to 50% by mass, and more preferably 20 to 40% by mass. If it is the said range, the effect which maintains low-temperature fixability, making polyester resin high molecular weight can be acquired more notably.

(Crystalline polyester resin)
The crystalline polyester resin is obtained by condensation polymerization of at least a diol component and a dicarboxylic acid component.

  In the present invention, the crystalline polyester resin refers to a polyester resin having a clear endothermic peak rather than a stepwise endothermic amount change in differential scanning calorimetry (DSC). The clear endothermic peak specifically means a peak in which the half-value width of the endothermic peak is within 15 ° C. when measured at a rate of temperature increase of 10 ° C./min in differential scanning calorimetry (DSC). To do.

  The crystalline polyester resin is more effective as a fixing aid in the toner because it has higher meltability in the temperature range at the time of fixing than the amorphous polyester resin.

  The diol component for forming the crystalline polyester resin preferably contains an aliphatic diol having a straight chain of 6 to 12 carbon atoms, and other diols may be used in combination as necessary. In the present invention, a linear aliphatic diol (linear aliphatic diol) means a structure in which OH groups are bonded to both ends. The diol component is not limited to one type, and two or more types may be mixed and used.

  Examples of the straight chain aliphatic diol having 6 to 12 carbon atoms include 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol. 1,11-undecanediol, 1,12-dodecanediol and the like.

  As the linear aliphatic diol, it is preferable to use one in which two OH groups are bonded to both ends of the carbon chain.

  Examples of other diols include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,15. -Other linear fatty acid diols such as pentadecanediol, 1,18-octadecanediol, 1,20-eicosanediol; 2-butene-1,4-diol, 3-hexene-1,6-diol, 4-octene Examples thereof include diols having a double bond such as -1,8-diol.

  The dicarboxylic acid component for forming the crystalline polyester resin preferably contains a linear aliphatic dicarboxylic acid in which the carbon chain containing carbon belonging to the above-mentioned carboxyl group is a straight chain having 8 to 14 carbon atoms. Depending on the case, other dicarboxylic acids may be used in combination.

  The dicarboxylic acid component is not limited to one type, and two or more types may be mixed and used.

  Examples of the linear aliphatic dicarboxylic acid having 8 to 14 carbon atoms include suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, 1,11-undecanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, and the like. Is mentioned.

  As the linear aliphatic dicarboxylic acid, it is preferable to use one in which two COOH groups are bonded to both ends of the carbon chain.

  Examples of other dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, 1,13-tridecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, and 1,16-hexadecanedicarboxylic acid. Examples include acids and other linear fatty acid dicarboxylic acids such as 1,18-octadecanedicarboxylic acid; their lower alkyl esters and acid anhydrides.

  The method for producing the crystalline polyester resin is not particularly limited, and can be produced by using a general polyester polymerization method in which a dicarboxylic acid component and a diol component are reacted in the presence of a catalyst, such as direct polycondensation or ester. It is preferable that the exchange method is used in accordance with the type of monomer.

  Examples of catalysts that can be used for the production of crystalline polyester resins include titanium catalysts such as titanium tetraethoxide, titanium tetrapropoxide, titanium tetraisopropoxide, titanium tetrabutoxide, dibutyltin dichloride, dibutyltin oxide, and diphenyltin oxide. And tin catalysts.

  The use ratio of the dicarboxylic acid component to the diol component is preferably an equivalent ratio [OH] / [COOH] of the hydroxyl group [OH] of the diol component and the carboxyl group [COOH] of the dicarboxylic acid component, preferably 1.5. /1-1/1.5, more preferably 1.2 / 1 to 1 / 1.2.

  The molecular weight of the crystalline polyester resin measured by gel permeation chromatography (GPC) is preferably a weight average molecular weight (Mw) of 50,000 to 800,000, more preferably 60,000 to 500,000. It is.

  When the crystalline polyester resin has a weight average molecular weight (Mw) of 50,000 or more, bleeding of the crystalline polyester resin is suppressed even during storage, and sufficient heat-resistant storage stability is obtained. When the weight average molecular weight (Mw) of the crystalline polyester resin is 800,000 or less, sufficient low-temperature fixability can be obtained. Here, the value calculated | required by the method as described in the below-mentioned Example shall be employ | adopted for the weight average molecular weight of a polyester resin.

  The acid value of the crystalline polyester resin is not particularly limited, but is, for example, 10 to 30 mg / KOH, and preferably 15 to 25 mg / KOH. If the acid value of the crystalline polyester resin is 10 mg / KOH or more, the resin dispersion can be easily prepared. If the acid value of the crystalline polyester resin is 30 mg / KOH or less, a sufficient degree of polymerization can be obtained, so that it becomes easy to prepare a polyester resin having a desired molecular weight. Further, since the hygroscopicity of the toner surface is kept low, the charge amount and toner storage property under high temperature and high humidity are improved. The acid value in the present invention means the number of mg of potassium hydroxide necessary for neutralizing the acid component contained in 1 g of resin. An example of the test method is a neutralization titration method.

  As the crystalline polyester resin, one having a melting point of 40 to 90 ° C is preferably used, and more preferably 55 to 80 ° C.

  When the melting point of the crystalline polyester resin is 40 ° C. or higher, the obtained toner has a high thermal strength and a sufficient heat-resistant storage property is obtained. In addition, since the melting point of the crystalline polyester resin is 90 ° C. or less, the crystalline polyester resin can be quickly melted during thermal fixing to promote fixing on a transfer material, and sufficient low-temperature fixing property can be obtained. It is done.

  Here, the melting point of the crystalline polyester resin is specifically determined by using a differential scanning calorimeter “Diamond DSC” (manufactured by Perkin Elmer Co., Ltd.) and raising the temperature from 0 ° C. to 200 ° C. at an elevation rate of 10 ° C./min. Measurement through a temperature increasing process, a cooling process for cooling from 200 ° C. to 0 ° C. at a cooling rate of 10 ° C./min, and a second temperature increasing process for increasing the temperature from 0 ° C. to 200 ° C. at a lifting speed of 10 ° C./min. Based on the DSC curve obtained by this measurement (temperature increase / cooling conditions), the melting point is the endothermic peak top temperature derived from the crystalline polyester resin in the first temperature increase process. It is. As a measurement procedure, 3.0 mg of crystalline polyester resin is sealed in an aluminum pan and set in a sample holder of “Diamond DSC”. The reference used an empty aluminum pan.

[Amorphous polyester resin]
In the present invention, the amorphous polyester resin is a polycondensation product of at least a polyhydric alcohol component and a polycarboxylic acid component, and no clear endothermic peak is observed in differential scanning calorimetry (DSC). Polyester resin.

  The toner used in the present invention preferably contains at least an amorphous polyester resin. In the toner having a core-shell structure, the shell layer preferably contains an amorphous polyester resin.

  As the polyvalent carboxylic acid component for forming the amorphous polyester resin, polyvalent carboxylic acid and alkyl esters thereof, acid anhydrides and acid chlorides can be used. Alcohols and their ester compounds and hydroxycarboxylic acids can be used.

  Examples of the polyvalent carboxylic acid include oxalic acid, succinic acid, maleic acid, adipic acid, β-methyladipic acid, azelaic acid, sebacic acid, nonanedicarboxylic acid, decanedicarboxylic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, fumaric acid. , Citraconic acid, diglycolic acid, cyclohexane-3,5-diene-1,2-dicarboxylic acid, malic acid, citric acid, hexahydroterephthalic acid, malonic acid, pimelic acid, tartaric acid, mucoic acid, phthalic acid, isophthalic acid Acid, terephthalic acid, tetrachlorophthalic acid, chlorophthalic acid, nitrophthalic acid, p-carboxyphenylacetic acid, p-phenylenediacetic acid, m-phenylenediglycolic acid, p-phenylenediglycolic acid, o-phenylenediglycolic acid, diphenyl Acetic acid, diphenyl-p, p'-dicarbo Divalent carboxylic acids such as acid, naphthalene-1,4-dicarboxylic acid, naphthalene-1,5-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, anthracene dicarboxylic acid, dodecenyl succinic acid; trimellitic acid, pyromellitic acid And trivalent or higher carboxylic acids such as naphthalenetricarboxylic acid, naphthalenetetracarboxylic acid, pyrenetricarboxylic acid, and pyrenetetracarboxylic acid.

  In the present invention, a saturated aliphatic dicarboxylic acid is preferably included as a carboxylic acid component of the raw material monomer constituting the amorphous polyester resin. The specific form of the saturated aliphatic dicarboxylic acid is the same as described above.

  Preferably, the ratio of the saturated aliphatic dicarboxylic acid in the total carboxylic acid used as a raw material monomer constituting the amorphous polyester resin is 15 to 50% by mass, more preferably 20 to 40% by mass.

As the polyvalent carboxylic acid, an unsaturated aliphatic dicarboxylic acid such as fumaric acid, maleic acid, or mesaconic acid is preferably further used. In particular, an unsaturated aliphatic dicarboxylic acid represented by the following general formula (A) is used. It is preferable.
General formula (A): HOOC- (CR < ₁ > = CR _{< 2 >} ) _n- COOH
(Wherein R ₁ and R ₂ are a hydrogen atom, a methyl group or an ethyl group, and may be the same or different from each other, and n is an integer of 1 or 2).
In the present invention, an anhydride of a dicarboxylic acid such as maleic anhydride can also be used.

  The proportion of unsaturated aliphatic dicarboxylic acid in the total polyvalent carboxylic acid used is preferably 25 mol% or more and 75 mol% or less, and more preferably 30 mol% or more and 60 mol% or less.

  Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, butanediol, diethylene glycol, hexanediol, cyclohexanediol, octanediol, decanediol, dodecanediol, ethylene oxide adduct of bisphenol A, propylene oxide adduct of bisphenol A, etc. Examples include divalent alcohols; trivalent or higher polyols such as glycerin, pentaerythritol, hexamethylol melamine, hexaethylol melamine, tetramethylol benzoguanamine, and tetraethylol benzoguanamine.

  The ratio of the polycarboxylic acid component to the polyhydric alcohol component is such that the equivalent ratio [OH] / [COOH] of the hydroxy group [OH] of the polyhydric alcohol and the carboxy group [COOH] of the polycarboxylic acid is Preferably it is 1.5 / 1-1 / 1.5, More preferably, it is 1.2 / 1-1 / 1.2.

  Various conventionally known catalysts can be used as the catalyst for synthesizing the amorphous polyester resin.

  The amorphous polyester resin preferably has a glass transition point of 40 ° C. or higher and 70 ° C. or lower, more preferably 50 ° C. or higher and 65 ° C. or lower. When the glass transition point of the unmodified polyester resin is 40 ° C. or higher, the cohesive force in the high temperature region becomes appropriate for the polyester resin, and the occurrence of hot offset phenomenon during fixing is suppressed. Further, since the glass transition point of the unmodified polyester resin is 70 ° C. or less, sufficient melting can be obtained at the time of fixing, and a sufficient minimum fixing temperature can be ensured. The glass transition point of the amorphous polyester resin is a value measured by DSC measurement similar to the above except that the amorphous polyester resin was used as a measurement sample.

  Preferably, the toner used in the present invention contains an amorphous polyester resin, and the number average molecular weight (Mn) of the amorphous polyester resin is preferably 4,000 to 7,000, more preferably 4,500. ~ 6,500.

  The main peak molecular weight (Mp) of the amorphous polyester resin is preferably 7,000 or more and 12,000, more preferably 7,500 to 11,000.

  Further, the weight average molecular weight (Mw) of the amorphous polyester resin is not particularly limited, but is preferably 50,000 to 800,000, more preferably 60,000 to 500,000.

  When the amorphous polyester resin has a weight average molecular weight (Mw) of 50,000 or more, bleeding of the amorphous polyester resin is suppressed even during storage, and sufficient heat-resistant storage stability is obtained. Sufficient low-temperature fixability can be obtained when the amorphous polyester resin has a weight average molecular weight (Mw) of 800,000 or less. Here, the value calculated | required by the method as described in the below-mentioned Example shall be employ | adopted for the weight average molecular weight of a polyester resin.

  The acid value of the amorphous polyester resin is not particularly limited, but is, for example, 10 to 30 mg / KOH, and preferably 15 to 25 mg / KOH. If the acid value of the amorphous polyester resin is 10 mg / KOH or more, the resin dispersion can be easily prepared. If the acid value of the amorphous polyester resin is 30 mg / KOH or less, a sufficient degree of polymerization can be obtained, so that it becomes easy to prepare a polyester resin having a desired molecular weight. Further, since the hygroscopicity of the toner surface is kept low, the charge amount and toner storage property under high temperature and high humidity are improved. The acid value in the present invention means the number of mg of potassium hydroxide necessary for neutralizing the acid component contained in 1 g of resin. An example of the test method is a neutralization titration method.

In the polyester resin, a partially branched structure or a crosslinked structure may be formed by selecting a carboxylic acid valence or an alcohol valence as a polyvalent carboxylic acid monomer and / or a polyhydric alcohol monomer to be used. .

  Moreover, the said polyester resin may also contain the styrene-acryl modified polyester resin obtained by using unsaturated aliphatic dicarboxylic acid. Details of the styrene-acrylic modified polyester resin will be described later.

  The content of the amorphous polyester resin in the binder resin is not particularly limited, but is preferably 5 to 50% by mass and more preferably 10 to 30% by mass with respect to the total amount of the binder resin. When the content of the amorphous polyester resin is 5% by mass or more based on the total amount of the binder resin, the low temperature fixability is excellent. Moreover, if it is 50 mass% or less, it is preferable at the point of thin paper separability.

<Styrene-acrylic modified polyester resin>
In the present invention, it is preferable that at least a part of the polyester resin as the binder resin contains a styrene-acryl-modified polyester resin. The content ratio of the styrene-acrylic modified polyester resin in the polyester resin is preferably 70 to 100% by mass and more preferably 90 to 100% by mass in 100% by mass of the polyester resin. Hereinafter, the styrene-acryl modified polyester resin will be described.

  In the present invention, a styrene-acrylic modified polyester resin is a polyester segment composed of a polyester resin and a styrene-acrylic polymer segment composed of a styrene-acrylic polymer bonded via both reactive monomers. Resin. The styrene-acrylic polymer segment refers to a polymer portion obtained by polymerizing an aromatic vinyl monomer and a (meth) acrylate monomer.

  The styrene-acryl-modified polyester resin is not particularly limited, but is preferably a styrene-acryl-modified polyester resin having the following configuration. When preparing a toner having a core-shell structure, the styrene-acrylic modified polyester resin used for the core particle binder resin and the styrene-acrylic modified polyester resin used for the shell layer may be the same or different. Also good.

  The content ratio of the styrene-acrylic polymer segment in the styrene-acrylic modified polyester resin used in the present invention (hereinafter also referred to as “styrene-acrylic modification rate”) is not particularly limited, but is 5% by mass or more and 30% by mass. Or less, more preferably 5% by mass or more and 25% by mass or less, and further preferably 15% by mass or more and 25% by mass or less.

  The content ratio of the styrene-acrylic polymer segment in the styrene-acrylic modified polyester resin, that is, the styrene-acrylic modification rate is specifically the total mass of the resin material used for synthesizing the styrene-acrylic modified polyester resin, That is, a polymerizable monomer constituting an unmodified polyester resin that becomes a polyester segment, an aromatic vinyl monomer that becomes a styrene-acrylic polymer segment, and a (meth) acrylic acid ester monomer, and for combining them. The ratio of the mass of the aromatic vinyl monomer and the (meth) acrylic acid ester monomer to the total mass of both reactive monomers is referred to.

  When the styrene-acryl modification rate is 5% by mass or more, a toner having a sufficiently high storage elastic modulus can be obtained, so that the thin paper separability can be further improved. Further, when the styrene-acryl modification rate is 30% by mass or less, a high sharp melt property can be obtained, so that the low temperature fixability can be improved. In particular, when a styrene-acrylic modified polyester resin is used for the shell layer of a toner having a core-shell structure, the affinity with the core particles is appropriately controlled, and the film thickness is more uniform while being a thin layer. A smooth shell layer can be formed.

  In the toner used in the present invention, an unsaturated aliphatic dicarboxylic acid is used as a polyvalent carboxylic acid monomer to form a polyester segment of a styrene-acryl-modified polyester resin, and the unsaturated fat is added to the polyester segment. It is preferable that a structural unit derived from a group dicarboxylic acid is contained. An unsaturated aliphatic dicarboxylic acid refers to a chain dicarboxylic acid having a vinylene group in the molecule. Here, the structural unit means a unit having a molecular structure derived from a monomer in the resin.

  In particular, in a toner having a core-shell structure, a styrene-acryl-modified polyester resin having a structural unit derived from an unsaturated aliphatic dicarboxylic acid is used for the shell layer, so that the film thickness can be more uniform while being a thin layer. A smooth shell layer can be reliably formed. In addition, by containing a styrene-acryl-modified polyester resin having a structural unit derived from this unsaturated aliphatic dicarboxylic acid in the core particle, the linear structure is present in the molecule, so that it has an affinity for a release agent. And the incorporation of the release agent into the core particles is improved, and the smoothness of the surface can be maintained.

  Content ratio of structural unit derived from unsaturated aliphatic dicarboxylic acid in structural unit derived from polyvalent carboxylic acid monomer constituting polyester segment of styrene-acrylic modified polyester resin (hereinafter referred to as “specific unsaturated dicarboxylic acid contained” The ratio is also not particularly limited, but is, for example, 18 mol% or more, preferably 25 mol% or more and 75 mol% or less, and more preferably 25 mol% or more and 60 mol% or less. Particularly preferred is 30 mol% or more and 60 mol% or less.

The structural unit derived from the unsaturated aliphatic dicarboxylic acid is preferably a structural unit derived from one represented by the following general formula (A).
General formula (A): HOOC- (CR < ₁ > = CR _{< 2 >} ) _n- COOH
(Wherein R ₁ and R ₂ are a hydrogen atom, a methyl group or an ethyl group, and may be the same or different from each other, and n is an integer of 1 or 2).
By containing the structural unit derived from such an unsaturated aliphatic dicarboxylic acid, the thin paper separation property and the low-temperature fixing property can be further improved. Further, when used as a shell layer, a smooth shell layer having a more uniform film thickness and a thin layer can be more reliably formed. Moreover, in this invention, when using unsaturated aliphatic dicarboxylic acid represented by general formula (A) for a polymerization reaction, it can also be used with the form of an anhydride.

  That is, in general, polyester resins have hydrophobic properties. When toner particles are produced by an emulsion aggregation method described later, polyester resin particles aggregate in the presence of core particles composed of a styrene-acrylic resin. In other words, so-called homoaggregation occurs. However, when a carbon-carbon double bond is present in the polyester molecule, the hydrophilicity of the polyester resin is increased and homoaggregation hardly occurs. In addition, since the hydrophilicity of the polyester resin is increased, when toner particles are produced by an emulsion aggregation method in an aqueous medium, the polyester resin segment has a great effect of being oriented outward with respect to the core particles, that is, the aqueous medium side. As a result, a thin and uniform shell layer can be formed.

  Therefore, as described above, the resin constituting the shell layer is a styrene-acrylic modified polyester resin, so that the styrene-acrylic component of the styrene-acrylic modified resin constituting the shell layer constitutes the core and It is possible to form a more uniform and dense shell layer due to the hydrophilic effect by the carbon-carbon double bond in the polyester resin segment, while keeping the affinity of Inferred.

  The styrene-acrylic modified polyester resin used in the present invention has a glass transition point of 50 from the viewpoint of reliably obtaining fixing properties such as low-temperature fixing property and fixing separation property, and heat resistance such as heat-resistant storage property and blocking resistance. It is preferable that it is -70 degreeC, More preferably, it is 50-65 degreeC, and it is preferable that a softening point is 80-110 degreeC. When used as a binder resin for core particles, the glass transition point is preferably 40 to 60 ° C, and the softening point is preferably 80 to 110 ° C.

  The glass transition point of the styrene-acrylic modified polyester resin is a value measured by a method (DSC method) defined in ASTM (American Society for Testing and Materials) D3418-82.

  Specifically, 4.5 mg of the sample was precisely weighed to two digits after the decimal point, sealed in an aluminum pan, and set in a sample holder of a differential scanning calorimeter “DSC8500” (Perkin Elmer). The reference uses an empty aluminum pan, and performs heat-cool-heat temperature control at a measurement temperature of −0 ° C. to 120 ° C., a temperature increase rate of 10 ° C./min, and a temperature decrease rate of 10 ° C./min. 2nd. Analysis was performed based on the data in Heat. The glass transition temperature is defined as the value of the intersection of the baseline extension before the rise of the first endothermic peak and the tangent indicating the maximum slope between the rise of the first endothermic peak and the peak apex.

  Moreover, the softening point of a styrene-acryl modified polyester resin is measured as follows.

First, in an environment of 20 ° C. ± 1 ° C./50%±5% RH, 1.1 g of resin is placed in a petri dish and flattened and allowed to stand for 12 hours or more. ) Is pressed with a force of 3820 kg / cm ² for 30 seconds to produce a cylindrical molded sample having a diameter of 1 cm, and this molded sample is then subjected to an environment of 24 ° C. ± 5 ° C. and 50% ± 20% RH, With a flow tester “CFT-500D” (manufactured by Shimadzu Corporation), a cylindrical die hole (1 mm diameter ×× 1 kg), with a load of 196 N (20 kgf), a starting temperature of 60 ° C., a preheating time of 300 seconds, and a heating rate of 6 ° C./min. than 1 mm), extruded from the time of preheating ends with piston diameter 1 cm, offset method temperature _{T offset} measured by setting the offset value 5mm at a melt temperature measurement method of temperature ramps are resin It is the softening point.

(Method for producing styrene-acrylic modified polyester resin)
As a method for producing the styrene-acrylic modified polyester resin as described above, an existing general scheme can be used. As typical methods, there are the following four methods.

  (A) A polyester segment is polymerized in advance, and both reactive monomers are reacted with the polyester segment, and an aromatic vinyl monomer and a (meth) acrylic acid ester for forming a styrene-acrylic polymer segment. A method of forming a styrene-acrylic polymerized segment by reacting a system monomer. That is, an aromatic vinyl monomer and a (meth) acrylic acid ester monomer for forming a styrene-acrylic polymer segment are reacted with a polyvalent carboxylic acid monomer or a polyhydric alcohol monomer for forming a polyester segment. A method of polymerizing in the presence of an amphoteric monomer having a group to be obtained and a polymerizable unsaturated group, and an unmodified polyester resin.

  (B) A styrene-acrylic polymer segment is preliminarily polymerized, both reactive monomers are reacted with the styrene-acrylic polymer segment, and further a polyvalent carboxylic acid monomer and a polyester for forming a polyester segment are used. A method of forming a polyester segment by reacting a monohydric alcohol monomer.

  (C) A method in which a polyester segment and a styrene-acrylic polymer segment are respectively polymerized in advance, and the both reactive monomers are reacted with each other to bond them together.

  (D) A polyester segment is preliminarily polymerized, and a styrene-acrylic polymerizable monomer is added to the polymerizable unsaturated group of the polyester segment, or reacted with a vinyl group in the styrene-acrylic polymer segment to bond them together. Method.

  In the present invention, both reactive monomers are a group capable of reacting with a polyvalent carboxylic acid monomer and / or a polyhydric alcohol monomer for forming a polyester segment of a styrene-acryl-modified polyester resin, a polymerizable unsaturated group, It is a monomer having

The method (A) will be specifically described.
(1) A mixing step of mixing an unmodified polyester resin for forming a polyester segment, an aromatic vinyl monomer and a (meth) acrylic acid ester monomer, and both reactive monomers,
(2) Styrene-acrylic is added at the end of the polyester segment by polymerizing an aromatic vinyl monomer and a (meth) acrylic acid ester monomer in the presence of both reactive monomers and unmodified polyester resin. A polymer segment can be formed. In this case, the terminal hydroxyl group of the polyester segment and the carboxy group of the both reactive monomers form an ester bond, and the vinyl group of the both reactive monomers is the vinyl group of the aromatic vinyl monomer or (meth) acrylic acid monomer. The styrene-acrylic polymer segment is bonded to each other. Of the above synthesis methods, the method (A) is most preferred.

  According to this method, a styrene-acrylic polymer segment can be added to the end of a chain polyester segment, and this styrene-acrylic polymer segment has an affinity for the styrene-acrylic resin of the core particle. It is considered that the core-shell structure toner having a thin and uniform shell layer can be formed in such a manner that the polyester segments are exposed to the toner surface.

  In the mixing step (1), it is preferable to heat. The heating temperature may be within a range in which an unmodified polyester resin, aromatic vinyl monomer, (meth) acrylic acid ester monomer and both reactive monomers can be mixed, and good mixing is obtained. Since polymerization control becomes easy, it can be set to 80-120 degreeC, for example, More preferably, it is 85-115 degreeC, More preferably, it is 90-110 degreeC.

  As described above, the content ratio of the styrene-acrylic polymer segment in the styrene-acrylic modified polyester resin is when the total mass of the resin material used for synthesizing the styrene-acrylic modified polyester resin is 100% by mass. The ratio of the total of the aromatic vinyl monomer and (meth) acrylic acid ester monomer is preferably 5% by mass or more and 30% by mass or less.

The relative proportion of the aromatic vinyl monomer and the (meth) acrylic acid ester monomer is such that the glass transition point (Tg) calculated by the FOX formula represented by the following formula (i) is 35-8.
The ratio is preferably 0 ° C., preferably 40 to 60 ° C.

Formula (i): 1 / Tg = Σ (Wx / Tgx)
(In formula (i), Wx is the weight fraction of monomer x, and Tgx is the glass transition point of the homopolymer of monomer x.)
In the present specification, both reactive monomers are not used for calculation of the glass transition point.

  Among unmodified polyester resin, aromatic vinyl monomer, (meth) acrylic acid ester monomer, and both reactive monomers, the proportion of both reactive monomers used is the total mass of the resin material used, that is, the above four factors It is preferable that the ratio of the both reactive monomers is 100% by mass or more and 5.0% by mass or less, particularly 0.5% by mass or more and 3.0% by mass or less, when the total mass of is 100% by mass It is preferable that

(Aromatic vinyl monomers and (meth) acrylic acid ester monomers)
The aromatic vinyl monomer and (meth) acrylic acid ester monomer for forming the styrene-acrylic polymer segment have an ethylenically unsaturated bond capable of radical polymerization.

  Examples of the aromatic vinyl monomer include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, p-ethylstyrene, and pn. -Butyl styrene, p-tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, 2,4- Examples thereof include dimethylstyrene, 3,4-dichlorostyrene, and derivatives thereof.

  These aromatic vinyl monomers can be used alone or in combination of two or more.

  Examples of (meth) acrylic acid ester monomers include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, Examples include hexyl methacrylate, 2-ethylhexyl methacrylate, ethyl β-hydroxyacrylate, propyl γ-aminoacrylate, stearyl methacrylate, dimethylaminoethyl methacrylate, and diethylaminoethyl methacrylate. These (meth) acrylic acid ester monomers can be used alone or in combination of two or more.

  As aromatic vinyl monomers and (meth) acrylic acid ester monomers for forming styrene-acrylic polymer segments, styrene or its derivatives are often used from the viewpoint of obtaining excellent chargeability and image quality characteristics. Is preferred. Specifically, the amount of styrene or its derivative used is 50 mass in all monomers (aromatic vinyl monomer and (meth) acrylic acid ester monomer) used to form a styrene-acrylic polymer segment. % Or more is preferable.

(Amotropic monomer)
Examples of the both reactive monomers for forming the styrene-acrylic polymer segment include a group capable of reacting with the polyvalent carboxylic acid monomer and / or the polyhydric alcohol monomer for forming the polyester segment, and a polymerizable unsaturated group. Specifically, for example, acrylic acid, methacrylic acid, fumaric acid, maleic acid, maleic anhydride and the like can be used. In the present invention, it is preferable to use acrylic acid or methacrylic acid as the bireactive monomer.

  The polyester resin used for producing the styrene-acrylic modified polyester resin is as described above.

(Polymerization initiator)
In the polymerization step of polymerizing the aromatic vinyl monomer and the (meth) acrylic acid ester monomer, the polymerization is preferably performed in the presence of a radical polymerization initiator, and the timing of adding the radical polymerization initiator is particularly limited. However, it is preferably added after the mixing step in terms of easy control of radical polymerization.

  Various known polymerization initiators are preferably used as the polymerization initiator. Specifically, for example, hydrogen peroxide, acetyl peroxide, cumyl peroxide, tert-butyl peroxide, propionyl peroxide, benzoyl peroxide, chlorobenzoyl peroxide, dichlorobenzoyl peroxide, bromomethylbenzoyl peroxide, Lauroyl oxide, ammonium persulfate, sodium persulfate, potassium persulfate, diisopropyl peroxycarbonate, tetralin hydroperoxide, 1-phenyl-2-methylpropyl-1-hydroperoxide, pertriphenylacetic acid-tert-hydroperoxide, performic acid-tert -Butyl, peracetic acid-tert-butyl, perbenzoic acid-tert-butyl, perphenylacetic acid-tert-butyl, permethoxyacetic acid-tert-butyl, per-N- (3-toluyl) palmitic acid-tert-butyl, etc. Peroxides; 2 2′-azobis (2-aminodipropane) hydrochloride, 2,2′-azobis- (2-aminodipropane) nitrate, 1,1′-azobis (1-methylbutyronitrile-3-sulfonic acid sodium salt) 4,4′-azobis-4-cyanovaleric acid, and azo compounds such as poly (tetraethylene glycol-2,2′-azobisisobutyrate).

(Chain transfer agent)
In the polymerization step of polymerizing the aromatic vinyl monomer and the (meth) acrylic acid ester monomer, a chain transfer agent generally used is used for the purpose of adjusting the molecular weight of the styrene-acrylic polymer segment. Can be used. The chain transfer agent is not particularly limited, and examples thereof include alkyl mercaptans and mercapto fatty acid esters.

  The chain transfer agent is preferably mixed with the resin forming material in the mixing step.

  The addition amount of the chain transfer agent varies depending on the molecular weight and molecular weight distribution of the desired styrene-acrylic polymer segment. Specifically, the aromatic vinyl monomer, (meth) acrylic acid ester monomer, and both reactive monomers are used. It is preferable to add in the range of 0.1-5 mass% with respect to the total amount.

  The polymerization temperature in the polymerization step for polymerizing the aromatic vinyl monomer and the (meth) acrylic acid ester monomer is not particularly limited, and the polymerization between the aromatic vinyl monomer and the (meth) acrylic acid ester monomer and the polyester It can select suitably in the range in which the coupling | bonding to resin advances. For example, the polymerization temperature is preferably 85 ° C. or higher and 125 ° C. or lower, more preferably 90 ° C. or higher and 120 ° C. or lower, and further preferably 95 ° C. or higher and 115 ° C. or lower.

  In the production of the styrene-acrylic modified polyester resin, it is practically preferable that volatile organic substances from the emulsion such as the amount of residual monomer after the polymerization step are suppressed to 1,000 ppm or less, more preferably 500 ppm or less, Preferably it is 200 ppm or less.

(Other binder resins)
As the binder resin for the toner used in the present invention, in addition to the above polyester resin, the following resins may be used in combination. For example, a polymer of styrene such as polystyrene, poly p-chlorostyrene, polyvinyltoluene and the like; a styrene-p-chlorostyrene copolymer, a styrene-propylene copolymer, a styrene-vinyltoluene copolymer, a styrene- Vinyl naphthalene 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, styrene-acrylonitrile copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene Copolymer, styrene-iso Styrene copolymers such as a lene copolymer, a styrene-acrylonitrile-indene copolymer, a styrene-maleic acid copolymer, and a styrene-maleic acid ester copolymer; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, Examples thereof include polyvinyl acetate, polyethylene, polypropylene, epoxy resin, epoxy polyol resin, polyurethane, polyamide, polyvinyl butyral, polyacrylic acid resin, and the like. These can be used alone or in combination of two or more.

<< Toner having core-shell structure >>
The toner used in the method of the present invention is not particularly limited. For example, a toner having a core-shell structure or a toner having a homogeneous structure that is not a core-shell type may have two or more types. The toner may be a toner having a sea-island structure, but a toner having a core-shell structure is preferable from the viewpoint of achieving both low-temperature fixability and heat-resistant storage stability of the toner. The shell layer constituting the toner having a core-shell structure is not particularly limited, but is preferably made of a shell resin containing the above-mentioned styrene-acryl-modified polyester resin.

≪Shell layer≫
Examples of the resin used in the shell resin include styrene-acrylic modified polyester resin, styrene-acrylic resin, polyester resin, and urethane resin. A polyester resin, a urethane resin, or the like may be contained together with the styrene-acrylic modified polyester resin.

  The content of the styrene-acrylic modified polyester resin in the shell resin is preferably 70 to 100% by mass and more preferably 90 to 100% by mass in 100% by mass of the shell resin.

  When the content ratio of the styrene-acrylic modified polyester resin in the shell resin is within the above range, a sufficient affinity between the core particles and the shell layer can be obtained, thereby forming a uniform shell layer with a thin layer. Therefore, heat storage stability and crushing resistance are improved, and chargeability is improved.

  By using a styrene-acryl-modified polyester resin as the shell resin constituting the toner, the following effects can be obtained.

  That is, in general, the advantage of using a polyester resin as a binder resin in designing toner particles is that the polyester resin maintains a high glass transition point (Tg) as compared with a styrene-acrylic resin and is designed to have a low softening point. Is easy to do. That is, the polyester resin is a suitable resin for satisfying both low-temperature fixability and heat-resistant storage stability. And by introducing a styrene-acrylic polymer segment into the polyester resin used in the shell layer, the affinity of the core particle with the styrene-acrylic resin of the core particle while maintaining the high glass transition point and low softening point of the polyester resin As a result, a shell layer having a more uniform film thickness and a smooth surface can be formed while being a thin layer. Therefore, according to the toner of the present invention, both low-temperature fixability and heat-resistant storage stability are satisfied, and excellent chargeability is obtained. Further, since the shell layer is hardly peeled off, the toner is stirred in the developing device. As a result, sufficient resistance to crushing that is not crushed even when subjected to stress is obtained, and as a result, a high-quality image such as a high-speed machine can be obtained without causing image noise.

  The content ratio of the shell resin in the binder resin constituting the toner is preferably 5 to 50% by mass and more preferably 10 to 40% by mass with respect to the total amount of the binder resin.

  It is preferable that the content ratio of the shell resin in the binder resin in the toner is in the above range since both low-temperature fixability and heat-resistant storage stability can be achieved.

≪Core particle≫
The core particles contain at least a binder resin, and may contain a colorant, a wax (also referred to as a release agent), and a charge control agent as necessary. The binder resin constituting the core particle is not particularly limited, and styrene-acrylic resin, styrene-acryl-modified polyester resin, polyester resin, and the like can be used. In particular, the binder resin constituting the core particles preferably contains a styrene-acrylic resin or a styrene-acrylic modified polyester resin.

(Styrene-acrylic modified polyester resin)
As the styrene-acrylic modified polyester resin constituting the core particle, the aforementioned styrene-acrylic modified polyester resin is used.

(Styrene-acrylic resin)
The polymerizable monomer used in the styrene-acrylic resin constituting the core particle is an aromatic vinyl monomer and a (meth) acrylic acid ester monomer, and has an ethylenically unsaturated bond capable of radical polymerization. Those are preferred. For example, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, p-ethylstyrene, pn-butylstyrene, p-tert- Butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, 2,4-dimethyl styrene, 3,4-dichloro Examples thereof include styrene and derivatives thereof. These aromatic vinyl monomers can be used alone or in combination of two or more.

  Examples of (meth) acrylic acid ester monomers include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, Examples include hexyl methacrylate, 2-ethylhexyl methacrylate, ethyl β-hydroxyacrylate, propyl γ-aminoacrylate, stearyl methacrylate, dimethylaminoethyl methacrylate, and diethylaminoethyl methacrylate. These (meth) acrylic acid ester monomers can be used alone or in combination of two or more. Among these, it is preferable to use a combination of a styrene monomer, an acrylate ester monomer, and / or a methacrylate ester monomer.

  A third vinyl monomer can also be used as the polymerizable monomer. Examples of the third vinyl monomer include acid monomers such as acrylic acid, methacrylic acid, maleic anhydride, and vinyl acetate, and acrylamide, methacrylamide, acrylonitrile, ethylene, propylene, butylene vinyl chloride, N-vinylpyrrolidone, butadiene, and the like. Is mentioned.

  A polyfunctional vinyl monomer may be further used as the polymerizable monomer. Examples of the polyfunctional vinyl monomer include diacrylates such as ethylene glycol, propylene glycol, butylene glycol, and hexylene glycol, and dimethacrylates and trimethacrylates of tertiary alcohols such as divinylbenzene, pentaerythritol, and trimethylolpropane. Is mentioned. The copolymerization ratio of the polyfunctional vinyl monomer to the entire polymerizable monomer is usually 0.001 to 5% by mass, preferably 0.003 to 2% by mass, and more preferably 0.01 to 1% by mass. By using a polyfunctional vinyl monomer, a gel component insoluble in tetrahydrofuran is produced, but the proportion of the gel component in the whole polymer is usually 40% by mass or less, preferably 20% by mass or less.

  The glass transition point (Tg) of the binder resin constituting the core particle is preferably 40 ° C to 60 ° C.

  Similarly, the softening point of the binder resin constituting the core particle is preferably 80 ° C. to 110 ° C. When the glass transition point and softening point of the binder resin constituting the core particle are within the above ranges, the viscosity and elasticity of the toner can be within a preferable range, so that both low temperature fixability and fixing separation performance are satisfied. Can do.

  The measuring method of the glass transition point (Tg) and softening point of the binder resin constituting the core particle can be performed by the same method as the measuring method of the styrene-acrylic modified polyester resin.

(Method for producing styrene-acrylic resin)
The styrene-acrylic resin is preferably used in an emulsion polymerization method. Emulsion polymerization can be obtained by dispersing and polymerizing a polymerizable monomer such as styrene or acrylate in an aqueous medium. In order to disperse the polymerizable monomer in the aqueous medium, a surfactant is preferably used, and a polymerization initiator and a chain transfer agent can be used for the polymerization.

(Polymerization initiator)
The polymerization initiator used for the polymerization of the styrene-acrylic resin is not particularly limited, and known ones can be used, and the styrene-acrylic polymer of the styrene-acrylic modified polyester resin described above. A polymerization initiator used for polymerizing the segments can be used. As the polymerization initiator used for the polymerization, a water-soluble polymerization initiator is preferably used. Specifically, for example, hydrogen peroxide, acetyl peroxide, cumyl peroxide, tert-butyl peroxide, propionyl peroxide, benzoyl peroxide, chlorobenzoyl peroxide, dichlorobenzoyl peroxide, bromomethylbenzoyl peroxide, Lauroyl oxide, ammonium persulfate, sodium persulfate, potassium persulfate, diisopropyl peroxycarbonate, tetralin hydroperoxide, 1-phenyl-2-methylpropyl-1-hydroperoxide, pertriphenylacetic acid-tert-hydroperoxide, performic acid-tert -Butyl, peracetic acid-tert-butyl, perbenzoic acid-tert-butyl, perphenylacetic acid-tert-butyl, permethoxyacetic acid-tert-butyl, per-N- (3-toluyl) palmitic acid-tert-butyl, etc. Peroxides; 2, '-Azobis (2-aminodipropane) hydrochloride, 2,2'-azobis- (2-aminodipropane) nitrate, 1,1'-azobis (sodium 1-methylbutyronitrile-3-sulfonate), Examples include 4,4′-azobis-4-cyanovaleric acid and azo compounds such as poly (tetraethylene glycol-2,2′-azobisisobutyrate).

(Chain transfer agent)
In the production of the styrene-acrylic resin, a chain transfer agent may be added together with the polymerizable monomer. The molecular weight of the polymer can be controlled by adding a chain transfer agent. As the chain transfer agent, a known one can be used. For example, the chain transfer agent used for the polymerization of the styrene-acrylic polymer segment of the styrene-acryl-modified polyester resin described above can be used. Examples include mercaptans and mercapto fatty acid esters. The addition amount of the chain transfer agent varies depending on the desired molecular weight and molecular weight distribution, but specifically, it is preferably added in the range of 0.1 to 5% by mass with respect to the polymerizable monomer.

(Surfactant)
When a styrene-acrylic resin is dispersed in an aqueous medium and polymerized by an emulsion polymerization method, a dispersion stabilizer is usually added to prevent aggregation of the dispersed droplets. As the dispersion stabilizer, a known surfactant can be used, and a dispersion stabilizer selected from a cationic surfactant, an anionic surfactant, a nonionic surfactant and the like can be used. Two or more of these surfactants may be used in combination. The dispersion stabilizer can also be used in a dispersion liquid such as a colorant and an offset preventing agent.

  Specific examples of the cationic surfactant include dodecyl ammonium bromide, dodecyl trimethyl ammonium bromide, dodecyl pyridinium chloride, dodecyl pyridinium bromide, and hexadecyl trimethyl ammonium bromide.

  Specific examples of nonionic surfactants include dodecyl polyoxyethylene ether, hexadecyl polyoxyethylene ether, norylphenyl polyoxyethylene ether, lauryl polyoxyethylene ether, sorbitan monooleate polyoxyethylene ether, styrylphenyl poly Examples thereof include oxyethylene ether and monodecanoyl sucrose.

  Specific examples of anionic surfactants include aliphatic soaps such as sodium stearate and sodium laurate, sodium lauryl sulfate, sodium dodecylbenzene sulfonate, and polyoxyethylene (2) sodium lauryl ether sulfate. Can do.

  If necessary, a colorant, a release agent (wax), and a charge control agent can be added to the toner used in the present invention.

(Coloring agent)
As the colorant used in the toner, carbon black, a magnetic material, a dye, a pigment, and the like can be arbitrarily used. Examples of the carbon black include channel black, furnace black, acetylene black, thermal black, and lamp black. used. As the magnetic material, a ferromagnetic metal such as iron, nickel, or cobalt, an alloy containing these metals, a compound of a ferromagnetic metal such as ferrite or magnetite, or the like can be used.

  As the dye, C.I. I. Solvent Red 1, 49, 52, 58, 63, 111, 122, C.I. I. Solvent Yellow 19, 44, 77, 79, 81, 82, 93, 98, 103, 104, 112, 162, C.I. I. Solvent Blue 25, 36, 60, 70, 93, 95, etc. can be used, and mixtures thereof can also be used. Examples of the pigment include C.I. I. Pigment Red 5, 48: 1, 48: 3, 53: 1, 57: 1, 81: 4, 122, 139, 144, 149, 166, 177, 178, 222, C.I. I. Pigment Orange 31 and 43, C.I. I. Pigment Yellow 14, 17, 74, 93, 94, 138, 155, 180, 185, C.I. I. Pigment green 7, C.I. I. Pigment Blue 15: 3, 15: 4, 60, etc. can be used, and a mixture thereof can also be used. The number average primary particle diameter varies depending on the type, but is preferably about 10 to 200 nm.

(Release agent)
The toner can contain a release agent. Examples of the release agent include hydrocarbon waxes such as low molecular weight polyethylene wax, low molecular weight polypropylene wax, Fischer-Tropsch wax, microcrystalline wax, and paraffin wax, carnauba wax, pentaerythritol behenate, and behenyl behenate. And ester waxes such as behenyl citrate. These can be used alone or in combination of two or more.

  The content rate of a mold release agent is 2-20 mass% of the resin particle total mass, Preferably it is 3-18 mass%, More preferably, it is 4-15 mass%.

  Further, the melting point of the release agent is preferably 50 to 95 ° C. from the viewpoint of low-temperature fixability and releasability of the toner in electrophotography.

(Charge control agent)
As the charge control agent constituting the charge control agent particles, various known ones that can be dispersed in an aqueous medium can be used. Specific examples include nigrosine dyes, naphthenic acid or higher fatty acid metal salts, alkoxylated amines, quaternary ammonium salt compounds, azo metal complexes, salicylic acid metal salts, or metal complexes thereof.

  The charge control agent particles preferably have a number average primary particle diameter of about 10 to 500 nm in a dispersed state.

≪Toner matrix particles≫
Next, the toner base particles used in the present invention will be described. The “toner base particle” as used in the present invention is a particle containing at least a binder resin and, if necessary, a colorant, and is a base of toner particles used for electrophotographic image formation. It constitutes. The toner base particles can be used as toner particles as they are, but it is usually preferable to add the external additives.

  The toner is an aggregate of toner particles.

  The average circularity of the toner base particles is preferably 0.850 or more and 0.990 or less.

  Here, the average circularity of the toner base particles is a value measured using “FPIA-2100” (manufactured by Sysmex).

  Specifically, the toner base particles are moistened in a surfactant aqueous solution, and ultrasonic dispersion is performed for 1 minute. After dispersion, the HPF is used in the measurement condition HPF (high magnification imaging) mode using “FPIA-2100”. Measurement is performed at an appropriate concentration of 4000 detections. The circularity is calculated by the following formula.

Circularity = (perimeter of a circle having the same projection area as the particle image) / (perimeter of the particle projection image)
The average circularity is an arithmetic average value obtained by adding the circularity of each particle and dividing by the total number of particles measured.

The toner base particles preferably have a volume-based median diameter (D ₅₀ ) of 3 μm or more and 10 μm or less.

  By setting the volume reference median diameter in the above range, for example, it is possible to faithfully reproduce a very minute dot image at a level of 1200 dpi (dpi; number of dots per inch (2.54 cm)).

The volume-based median diameter (D ₅₀ ) of the toner base particles can be measured and calculated using, for example, an apparatus in which a computer system for data processing is connected to “Multisizer 3 (manufactured by Beckman Coulter)”. .

As a measurement procedure, 0.02 g of toner base particles was added to 20 ml of a surfactant solution (for example, a surfactant solution in which a neutral detergent containing a surfactant component was diluted 10 times with pure water for the purpose of dispersing toner base particles. ), Followed by ultrasonic dispersion for 1 minute to prepare a toner particle dispersion. This toner base particle dispersion is poured into a beaker containing ISOTON II (manufactured by Beckman Coulter) in a sample stand with a pipette until the measured concentration reaches 5 to 10%, and the measuring machine count is set to 25,000. To measure. The aperture size of the multisizer 3 is 100 μm. The frequency number obtained by dividing the measurement range of 1 to 30 μm into 256 parts is calculated, and the particle diameter of 50% from the larger volume integrated fraction is defined as the volume reference median diameter (D ₅₀ ).

≪Toner≫
(Main peak molecular weight of toner)
The main peak molecular weight of the toner used in the present invention is 11,000 or more. The main peak molecular weight of the toner is a molecular weight measured with respect to a tetrahydrofuran (THF) soluble component, and the contribution of a component that does not dissolve in THF such as a colorant is excluded. The main peak molecular weight of the toner is a value obtained by the measurement method described in Examples described later. When the main peak molecular weight of the toner is less than 11,000, the halftone image is rubbed in a halftone image formed with toner containing a polyester resin using an image device including a fixing device having a cooling unit. Fixability is reduced and output paper is likely to be stained. In addition, since the meltability of the toner becomes high, it is difficult to achieve both storage stability. Preferably, the main peak molecular weight of the toner is 15,000 or more. The upper limit of the main peak molecular weight of the toner is not particularly limited, but is preferably 25,000 or less from the viewpoint of securing low temperature fixability.

(Toner softening point)
The softening point of the toner used in the present invention is preferably 90 to 115 ° C. When the softening point of the toner is within this range, preferable low-temperature fixability can be obtained.

  The softening point can be measured by the above-described method, that is, “Flow Tester CFT-500D” (manufactured by Shimadzu Corporation).

(Viscoelasticity of toner)
The storage elastic modulus at 150 ° C. of the toner used in the present invention is 1.0 × 10 ^{3 to} 1.0 × 1.
It is preferably in the range of 0 ⁴ Pa. The storage elastic modulus of the toner is an index indicating the hardness of the toner as a viscoelastic body. If the storage elastic modulus at 150 ° C. of the toner is 1.0 × 10 ³ Pa or more, a halftone formed with a toner containing a polyester resin using an image device provided with a fixing device having a cooling means In an image, the toner shape is unlikely to be a stretched protrusion. Therefore, it is possible to prevent the stretched protrusion component from being destroyed and the rubbing and fixing properties of the halftone image from being deteriorated, and the output paper from becoming dirty. On the other hand, if the storage elastic modulus of the toner at 150 ° C. is 1.0 × 10 ⁴ Pa or less, the low-temperature fixability of the toner can be improved. More preferably, the storage elastic modulus of the toner at 150 ° C. is 1.5 to 8.0 × 10 ³ Pa. The tan δ at 150 ° C. of the toner is obtained as (loss elastic modulus / storage elastic modulus) from the storage elastic modulus value and the loss elastic modulus value. The tan δ at 150 ° C. of the toner is preferably 1.7 or less, more preferably 1.2 or less. If the value of tan δ is 1.7 or less, the stretched protrusion shape that can occur after passing through the fixing nip portion of the image forming apparatus is quickly elastically recovered. For this reason, it is possible to prevent the stretched protrusion component from being destroyed and the rubbing and fixing properties of the halftone image from being deteriorated to cause the output paper to become dirty. The lower limit of tan δ is not particularly limited, but is preferably 0.5 or more from the viewpoint of forming a high-quality image. The viscoelasticity of the toner can be adjusted, for example, by controlling the molecular weight of the polyester resin contained in the binder resin, the styrene-acryl modification rate of the polyester resin, and the like. Specifically, the storage elastic modulus increases as the weight average molecular weight of the polyester resin increases. Further, the higher the styrene-acryl modification rate of the polyester resin, the greater the storage elastic modulus.

  The storage elastic modulus and loss elastic modulus can be measured according to the following procedures (1) to (5) using a viscoelasticity measuring device “MCR302” (manufactured by Anton Paar).

  (1) Put the measurement sample in a petri dish and level it in an environment of 20 ± 1 ° C and relative humidity of 50 ± 5% RH, leave it for 12 hours or more, and then load 0.2g into the compression molder. Then, a pellet having a diameter of 1 cm is produced by applying a load of 3 t for 30 seconds.

  (2) The pellet is loaded on the parallel plate.

  (3) The measurement part temperature is set to a previously measured softening point of the toner of −20 ° C., and the parallel plate gap is set to 1 mm. With this setting, the measuring part is heated to the softening point of the toner of −20 ° C., and the pellet is compressed until the gap becomes 1 mm. Then, it cools to 30 degreeC.

  (4) After setting the measurement part temperature to 30 ° C., the temperature of the measurement part is increased to 200 ° C. at a temperature increase rate of 3 ° C./min while applying a sinusoidal vibration with a frequency of 1.0 Hz, and the complex elasticity at 150 ° C. Measure the rate. The strain angle is controlled by automatic strain control.

  (5) Calculate storage elastic modulus and loss elastic modulus from the complex elastic modulus.

(Toner production method)
The toner used in the present invention obtains toner base particles by using a binder resin, if necessary, a colorant, and an internal additive such as a release agent, and externally removes the toner base particles as necessary. The toner can be produced by adding an additive.

  The toner base particles are particles containing at least a binder resin and, if necessary, a colorant, and constitute the base of toner particles used for electrophotographic image formation. These are called particles or colored particles.

  Examples of the method for producing the toner base particles include a suspension polymerization method, an emulsion aggregation method, and other known methods. The emulsion aggregation method is preferably used. According to this emulsion aggregation method, the toner particles can be easily reduced in size from the viewpoint of production cost and production stability.

  Here, the emulsion aggregation method refers to a dispersion of binder resin particles (hereinafter also referred to as “binder resin particles”) produced by emulsification, and, if necessary, particles of colorant (hereinafter referred to as “coloring”). In this method, toner particles are produced by mixing with a dispersion liquid (also referred to as “agent particles”), aggregating until a desired toner particle diameter is obtained, and further fusing the binder resin particles to control the shape. is there. Here, the binder resin particles may optionally contain a release agent, a charge control agent, and the like.

  An example of using the emulsion aggregation method as a method for producing the toner is shown below.

(1) Step of preparing a dispersion liquid in which colorant particles are dispersed in an aqueous medium (2) Dispersion liquid in which binder resin particles containing an internal additive are dispersed in an aqueous medium as necessary (3) A step of mixing the colorant particle dispersion and the binder resin particle dispersion to agglomerate and fuse the colorant particles and the binder resin particles to form toner particles (4) ) A step of filtering the toner particles from the dispersion system (aqueous medium) of the toner particles and removing the surfactant, etc. (5) A step of drying the toner particles (6) A step of adding an external additive to the toner particles As a method for dispersing the binder resin particles in the step 2), it is preferable to use an emulsion polymer particle dispersion obtained by emulsion polymerization. The binder resin particles may have a multilayer structure of two or more layers made of binder resins having different compositions. For the binder resin particles having such a structure, for example, those having a two-layer structure, a dispersion of resin particles is prepared by emulsion polymerization treatment (first stage polymerization) according to a conventional method, and polymerization is started in this dispersion. An agent and a polymerizable monomer are added, and this system can be obtained by a technique of polymerization treatment (second stage polymerization).

  In the emulsion aggregation method, it is also possible to obtain toner particles having a core-shell structure. Specifically, toner particles having a core-shell structure are prepared by first binding resin particles for core particles, colorant particles, and the like. Then, core particles are prepared by agglomerating and fusing, and then the binder resin particles for the shell layer are added to the core particle dispersion to agglomerate and fuse the binder resin particles for the shell layer on the core particle surface. It can be obtained by forming a shell layer that coats the surface of the core particles.

(Process for producing core particles)
As a method for forming the core particle, it can be produced by a known method, but an emulsion aggregation method in which resin particles dispersed in an aqueous medium and colored particles are aggregated to form core particles is preferably used.

  When the core particles have a structure formed by aggregating / fusion of binder resin particles containing styrene-acrylic resin or styrene-acrylic modified polyester resin, the core particles are usually formed by an emulsion aggregation method. In the case of employing the emulsion aggregation method, in detail, an aqueous medium together with a release agent, a charge control agent, magnetic powder, etc., if necessary, is obtained by polymerizing resin particles and colorant particles obtained by emulsifying and dispersing a polymerizable monomer in an aqueous medium. The core particles may be aggregated / fused to form core particles, or the polymerizable particles are seed-emulsified in an aqueous medium in the presence of an emulsified release agent or charge control agent to form core particles. It may be formed. The particle diameter of the resin particles is usually preferably in the range of 50 to 500 nm in terms of weight average particle diameter.

(Method for forming shell layer)
When the shell layer is uniformly formed on the surface of the core particle, it is preferable to employ an emulsion aggregation method. When the emulsion aggregation method is employed, an emulsion dispersion of shell particles can be added to an aqueous dispersion of core particles, and the shell particles can be aggregated / fused on the surface of the core particles to form a shell layer.

  In particular, the toner used in the present invention is a mixture of a dispersion liquid in which colorant particles are dispersed in an aqueous medium and a dispersion liquid in which binder resin particles are dispersed in an aqueous medium, whereby the colorant particles are mixed. In addition, it is preferably obtained by a process of aggregating and fusing the binder resin particles, that is, obtained by a production method such as an emulsion aggregation method.

  In the present invention, the “aqueous medium” refers to a medium comprising 50 to 100% by mass of water and 0 to 50% by mass of a water-soluble organic solvent. Examples of the water-soluble organic solvent include methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone, and tetrahydrofuran, and alcohol-based organic solvents that do not dissolve the resulting resin are preferable.

(Surfactant)
A dispersion stabilizer is usually added to the aqueous medium in order to prevent aggregation of dispersed droplets. As the dispersion stabilizer, a known surfactant can be used, and a dispersion stabilizer selected from a cationic surfactant, an anionic surfactant, a nonionic surfactant, and the like can be used. . Two or more of these surfactants may be used in combination. The dispersion stabilizer can also be used in a dispersion liquid such as a colorant and an offset preventing agent.

  Specific examples of the cationic surfactant include dodecyl ammonium bromide, dodecyl trimethyl ammonium bromide, dodecyl pyridinium chloride, dodecyl pyridinium bromide, hexadecyl trimethyl anonium bromide and the like.

  Specific examples of nonionic surfactants include dodecyl polyoxyethylene ether, hexadecyl polyoxyethylene ether, norylphenyl polyoxyethylene ether, lauryl polyoxyethylene ether, sorbitan monooleate polyoxyethylene ether, styrylphenyl poly Examples thereof include oxyethylene ether and monodecanoyl sucrose.

  Specific examples of anionic surfactants include aliphatic soaps such as sodium stearate and sodium laurate, sodium lauryl sulfate, sodium dodecylbenzene sulfonate, and polyoxyethylene (2) sodium lauryl ether sulfate. Can do.

(Dispersion of colorant)
A dispersion of colorant particles can be prepared by dispersing a colorant in an aqueous medium. The dispersion treatment of the colorant is preferably performed in a state where the surfactant concentration in the aqueous medium is equal to or higher than the critical micelle concentration because the colorant is uniformly dispersed. A known disperser can be used as the disperser used for the dispersion treatment of the colorant. Moreover, as a surfactant which can be used, a publicly known thing can be used.

  The particle diameter of the colorant particles in the step (1) of preparing the dispersion is preferably 10 to 300 nm in terms of volume-based median diameter.

(Measurement of dispersed particle size in colorant dispersion)
The dispersion particle diameter of the colorant particles in the aqueous medium is a volume average particle diameter, that is, a median diameter on a volume basis. This median diameter is measured using a microtrack particle size distribution measuring apparatus “UPA-150” (manufactured by Nikkiso Co., Ltd.). It is a measured value.

(Measurement condition)
(1) Sample refractive index: 1.59
(2) Sample specific gravity: 1.05 (in terms of spherical particles)
(3) Solvent refractive index: 1.33
(4) Solvent viscosity: 0.797 at 30 ° C, 1.002 at 20 ° C
Ion exchange water is put into the measurement cell, and the zero point adjustment is performed.

(Aggregation / fusion process)
Next, the step of aggregating and associating resin particles and colorant particles in the emulsion aggregation method will be described.

  In the agglomeration step, an aqueous dispersion of resin particles is mixed with a dispersion of colorant particles and, if necessary, release agent particles, charge control agent particles, and other toner constituent particles, to obtain a dispersion liquid for aggregation. And agglomerated and fused in an aqueous medium to form a dispersion of colored particles.

  The flocculant is not particularly limited, but a flocculant selected from metal salts is preferably used. For example, salts of monovalent metals such as alkali metal salts such as sodium, potassium and lithium, salts of divalent metals such as calcium, magnesium, manganese and copper, salts of trivalent metals such as iron and aluminum Specific examples of the salt include sodium chloride, potassium chloride, lithium chloride, calcium chloride, magnesium chloride, zinc chloride, copper sulfate, magnesium sulfate, and manganese sulfate. Among these, Particularly preferred are divalent metal salts. When a divalent metal salt is used, agglomeration can be promoted with a smaller amount. These may be used alone or in combination of two or more.

  In the flocculation step, it is preferable that the standing time (time until heating is started) to be left after adding the flocculant is as short as possible. That is, after adding the flocculant, it is preferable to start heating the flocculating dispersion liquid as quickly as possible so as to be equal to or higher than the glass transition point of the resin composition. The reason for this is not clear, but the agglomeration state of the particles fluctuates with the passage of the standing time, and there is a possibility that the particle size distribution of the obtained toner particles becomes unstable or the surface property fluctuates. Because there is. The standing time is usually within 30 minutes, preferably within 10 minutes.

  In the aggregation step, it is preferable to quickly raise the temperature by heating, and the rate of temperature rise is preferably 1 ° C./min or more. The upper limit of the heating rate is not particularly limited, but is preferably 15 ° C./min or less from the viewpoint of suppressing the generation of coarse particles due to rapid progress of fusion. Furthermore, it is important to continue the fusion by holding the temperature of the aggregation dispersion liquid for a certain period of time after the aggregation dispersion liquid reaches a temperature equal to or higher than the glass transition temperature. Thereby, the growth and fusion of the colored particles can be effectively advanced, and the durability of the toner particles finally obtained can be improved.

(External additive)
In the present invention, an external additive can be added for the purpose of improving the fluidity and charging characteristics of the toner.

  Examples of the external additive include inorganic oxide fine particles such as silica fine particles, alumina fine particles, and titanium oxide fine particles, inorganic stearate compound fine particles such as aluminum stearate fine particles and zinc stearate fine particles, strontium titanate, and zinc titanate. Inorganic fine particles such as inorganic titanic acid compound fine particles.

  These inorganic fine particles are preferably those subjected to surface treatment with a silane coupling agent, a titanium coupling agent, a higher fatty acid, silicone oil, or the like from the viewpoints of heat-resistant storage stability and environmental stability.

  The addition amount of the external additive is 0.05 to 5% by mass, preferably 0.1 to 3% by mass with respect to 100% by mass of the toner base particles. Various external additives may be used in combination.

  Examples of the method for adding the external additive include a dry method in which the external additive is added in powder form to the dried toner base particles. Examples of the mixing device include mechanical mixing devices such as a Henschel mixer and a coffee mill. Can be mentioned.

(Developer)
The toner can be used as a two-component developer composed of a carrier and a toner, or as a non-magnetic one-component developer composed only of a toner.

  Carriers that are magnetic particles used when used as a two-component developer are conventionally known materials such as metals such as iron, ferrite, and magnetite, and alloys of these metals with metals such as aluminum and lead. It is possible to use. Among these, ferrite particles are preferable. Further, as the carrier, a coated carrier in which the surface of the magnetic particles is coated with a coating agent such as a resin, a resin dispersion type carrier in which a magnetic fine powder is dispersed in a binder resin, or the like may be used. The carrier has a volume average particle size of preferably 15 to 100 μm, more preferably 25 to 80 μm.

<Image forming method>
The image forming method of the present invention is a method using an image forming apparatus having a fixing device having a cooling means.

  In an electrophotographic image forming method, an electrostatic latent image formed on a photoreceptor is visualized with toner, and the visualized toner image is transferred and fixed on a sheet to form an image.

  According to the image forming method of the present invention, a heating member that heats the paper carrying the toner image and a nip portion that sandwiches the paper carrying the toner image are brought into contact with the heating member to fix the image on the paper. A fixing device including a pressure member and a cooling unit that cools the sheet discharged from the nip portion and separates the sheet from the heating member is used.

  In such a fixing device, since the toner on the paper is heated and melted when passing through the nip portion, the paper does not wrap around the surface of the fixing roller or the fixing belt due to the adhesive force of the toner, and the paper jam occurs. May occur. When thin paper with a small amount of paper or coated paper for printing is used as the paper, it is particularly easy to wrap around the surface of a fixing roller or the like. However, by using a fixing device having a cooling means for cooling the paper discharged from the nip portion, the thin paper separation can be improved.

  The cooling means is not particularly limited, and means for cooling the paper by blowing air from the discharge port to the paper discharged from the nip portion (air separation means), and fixing belt or roller member for the fixed image. Means for cooling the sheet by contact may be used. Among them, it is preferable to use a means for cooling the paper by blowing air from the discharge port to the paper discharged from the nip portion as the cooling means. By using a means for cooling the paper by blowing air from the discharge port to the paper discharged from the nip portion, the thin paper separation property can be further improved. Further, the sheet can be separated without bringing a member such as a separation claw into contact with the surface of the roller member or the like, and the surface of the roller member or the like is not damaged.

[Outline of image forming apparatus]
FIG. 1 is an overall configuration diagram of an image forming apparatus X used in an embodiment of the present invention.

  The image forming apparatus X includes an image forming apparatus main body GH and an image reading apparatus YS. The image forming apparatus main body GH includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, a belt-shaped intermediate transfer belt 5, a paper feeding / conveying unit, a fixing device 8, and the like.

  An image reading device YS including an automatic document feeder 201 and a document image scanning exposure device 202 is installed on the upper part of the image forming apparatus main body GH. The document d placed on the document table of the automatic document feeder 201 is transported by the transport unit, and an image on one or both sides of the document d is scanned and exposed by the optical system of the document image scanning exposure device 202, and the line image sensor CCD is scanned. Is read.

  The signal formed by photoelectric conversion by the line image sensor CCD is subjected to analog processing, A / D conversion, shading correction, image compression processing, and the like in the image processing unit, and then the exposure units 3Y, 3M, 3C, and 3K. Sent to.

  In the image forming unit 10Y that forms a yellow (Y) image, a charging unit 2Y, an exposure unit 3Y, a developing unit 4Y, and a cleaning unit 7Y are arranged around the photosensitive drum 1Y. The image forming units 10M, 10C, and 10K have substantially the same configuration as the image forming unit 10Y. The developing units 4Y, 4M, 4C, and 4K include a two-component developer including yellow (Y), magenta (M), cyan (C), and black (K) toner having a small particle diameter and a carrier. The toner includes, for example, a pigment or dye serving as a colorant, a release agent that helps the toner peel from the fixing belt 81 after fixing, and a binder resin that holds them.

  The intermediate transfer belt 5 is wound around a plurality of rollers and is rotatably supported.

  The fixing device 8 heats and pressurizes the toner image on the paper P at a nip portion formed between the heated fixing belt 81 and the pressure roller 84 and fixes the toner image.

  Each color image formed by the image forming units 10Y, 10M, 10C, and 10K is sequentially transferred to the rotating intermediate transfer belt 5 by the transfer units 6Y, 6M, 6C, and 6K, thereby forming a color toner image. . The paper P stored in the paper feeding cassette 20 is fed by the paper feeding unit 21 and is conveyed to the transfer unit 6A through the paper feeding rollers 22A, 22B, 22C, 22D, the registration rollers 23, and the like. A color toner image is transferred. The sheet P on which the color toner image is transferred is heated and pressurized in the fixing device 8, and the color toner image is fixed on the sheet P. Thereafter, the sheet is sandwiched between the sheet discharge rollers 24 and placed on the sheet discharge tray 25.

  After the color toner image is transferred onto the paper P by the transfer unit 6A, the toner remaining on the intermediate transfer belt 5 from which the paper P has been peeled is removed by the cleaning unit 7A.

[Outline of fixing device]
Next, the fixing device 8 will be described in detail. FIG. 2 is an enlarged cross-sectional view of the fixing device 8.

  The fixing device 8 includes a fixing frame 8F having an outer frame made up of a plurality of frame members. Each member constituting the fixing device 8 is supported by the fixing frame 8F directly or indirectly. The fixing frame 8F is movably supported by a guide mechanism such as a slide rail, and the fixing device 8 can be pulled out of the image forming apparatus X in the front direction (the front side in FIG. 1 and FIG. 2). .

  The fixing belt 81 as a heating member is formed in an endless shape. For example, PI (polyimide) having a thickness of 70 μm is used as a base, and heat-resistant silicon rubber having a thickness of 200 μm is used as an elastic layer (hardness JIS-). A30 °), and the surface layer is coated with PFA (perfluoroalkoxyalkane), which is a heat-resistant resin having a thickness of 30 μm.

  The fixing belt 81 is stretched between the heating roller 82 and the fixing roller 83.

  The heating roller 82 has a built-in halogen heater 82A for heating the fixing belt 81. For example, a resin in which the outer peripheral surface of a cylindrical metal core 82B having a thickness of 4 mm formed of aluminum or the like is coated with PTFE having a thickness of 30 μm. Covered with layer 82C. The halogen heater 82A is composed of, for example, two of 1200 W, two of 750 W, and one of 500 W in order to cope with different paper widths, and different heat generation distributions in the axial direction corresponding to different paper widths of the paper. It is arranged to be.

  The fixing roller 83 is disposed to face the pressure roller 84 in order to form a nip portion N between the fixing belt 81 and the pressure roller 84. That is, in the present embodiment, the pressure roller 84 corresponds to the pressure member in the present invention. The fixing roller 83 is made of a solid core metal 83A formed of a metal such as iron, which is covered with a heat-resistant silicon rubber having a thickness of 20 mm as an elastic layer 83B. It is covered with a resin layer 83C coated with some PTFE.

  Around the heating roller 82, a temperature detection sensor SE that detects the temperature of the fixing belt 81 in a non-contact state with the fixing belt 81 is provided. The ON / OFF control of the halogen heater 82A is performed based on the detection result of the temperature detection sensor SE, and the fixing belt 81 is maintained at a temperature suitable for the fixing operation.

  The pressure roller 84 in contact with the fixing belt 81 incorporates a halogen heater 84A as a heating means in order to shorten the heating time immediately after the power supply to the image forming apparatus X is turned on, and is a cylinder having a thickness of 4 mm formed of aluminum or the like. The outer peripheral surface of the metal core 84B is covered with a 1 mm thick heat-resistant silicon rubber (hardness JIS-A 30 °) as an elastic layer 84C, and further covered with a resin layer 84D of a 30 μm thick PFA tube. Yes. The outer diameter is 90 mm. The pressure roller 84 is pressed against the fixing belt 81 and the fixing roller 83 by an urging means (not shown).

  In the above configuration, when the pressure roller 84 is rotated counterclockwise (x direction in FIG. 2) by a driving unit (not shown), the fixing belt 81, the heating roller 82, and the fixing roller 83 are rotated clockwise (y direction in FIG. 2). ) Rotate and rotate.

  The fixing belt 81 is heated by the halogen heater 82A via the heating roller 82 that contacts the fixing belt 81, and the pressure roller 84 is also heated by the halogen heater 84A. The fed paper is heated and pressurized at the nip portion N formed between the fixing belt 81 wound around the fixing roller 83 and the pressure roller 84, and the toner image on the paper is fixed. The

  In the present invention, the surface temperature of the fixing belt 81 can be appropriately set according to the type and thickness of the paper, but is, for example, 150 to 200 ° C., and preferably 160 to 190 ° C. Further, the speed of the fixing belt 81 is, for example, 150 to 400 mm / sec, preferably 220 to 330 mm / sec.

[Outline of air separation mechanism]
In the fixing device 8, an air separation unit that blows air against the paper discharged from the nip portion N to separate the paper from the fixing belt 81 is installed as a cooling unit. The air separation unit includes the suction fan F, the first duct 121, and the second duct 131 shown in FIG.

  The first duct 121 is formed of an elastic flexible member, and the second duct 131 is formed of a metal such as iron. The end portion of the first duct 121 is fixed to the end portion of the second duct 131, and the first duct 121 is deformed even when the second duct 131 is movable, as will be described later, and the opening portion 121 b of the first duct 121. And air does not leak from between the opening 131a of the second duct 131.

  As shown in FIG. 2, the opening 121a of the first duct 121 is connected to the suction fan F directly or through a communication duct (not shown). The other opening 121 b of the first duct 121 is connected to the opening 131 a of the second duct 131.

  The discharge port 131b, which is the other opening of the second duct 131, is installed near the nip N. Air sent from the suction fan F flows through the first duct 121 and the second duct 131 in the direction of the arrow shown in FIG. 2 and is discharged from the discharge port 131b, and near the leading edge of the paper discharged from the nip portion N. And sprayed. As a result, air enters between the sheet and the fixing belt 81, and the sheet is appropriately separated from the fixing belt 81, thereby preventing the sheet from being wound. In addition, by separating the paper from the fixing belt 81 by the air separation unit including the suction fan F, the first duct 121, and the second duct 131, a member such as a separation claw is not brought into contact with the surface of the fixing belt 81. Since the paper can be separated, the surface of the fixing belt 81 is not damaged.

At this time, the rotational speed of the suction fan F can be set, for example, within a range of 3000-15000 rpm, and the air volume discharged from the discharge port 131b is, for example, 0.3-1.3 m ³ / min. can do. The suction fan F sucks outside air at a temperature around the fixing device 8, but the temperature of the air blown against the paper is substantially the same as the temperature of the sucked outside air, for example, about 10 to 60 ° C. It can be.

  The sheet separated from the fixing belt 81 by the air separation unit is guided by the upper guide 211, the lower guide 212, and 213, and is sandwiched by the transport rollers R1 and R2 and is disposed on the downstream side in the transport direction of the fixing device 8. It is conveyed in the direction of 24 (see FIG. 1).

  Examples of the present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.

<Preparation of colorant particle dispersion>
90 parts by mass of sodium lauryl sulfate was stirred and dissolved in 1600 parts by mass of ion-exchanged water. While stirring this solution, 420 parts by mass of carbon black “Mogal L” (manufactured by Cabot) was gradually added.

  Subsequently, a “colorant particle dispersion” in which the colorant particles were dispersed was prepared by performing a dispersion treatment using a stirrer “CLEARMIX” (manufactured by M Technique Co., Ltd.). When the particle diameter of the colorant particles in this dispersion was measured using a Microtrac particle size distribution analyzer UPA-150 (manufactured by Nikkiso Co., Ltd.), the average particle diameter was 120 nm.

<Preparation of resin particle dispersion (A1) for core> (styrene-acrylic resin particles)
First stage polymerization In a reaction vessel equipped with a stirrer, temperature sensor, temperature control device, cooling pipe and nitrogen introduction device, 2.0 parts by mass of sodium lauryl sulfate as an anionic surfactant in advance to 2900 parts by mass of ion-exchanged water The dissolved anionic surfactant solution was charged, and the internal temperature was raised to 80 ° C. while stirring at a stirring speed of 230 rpm under a nitrogen stream.

To this surfactant solution, 9.0 parts by weight of potassium persulfate (KPS) as a polymerization initiator was added and the internal temperature was set to 78 ° C.
Solution (1); That is, styrene 540 parts by mass n-butyl acrylate 270 parts by mass Methacrylic acid 65 parts by mass n-octyl mercaptan 17 parts by mass of solution (1) was added dropwise over 3 hours. Polymerization (first stage polymerization) was carried out by heating and stirring for 1 hour to prepare “dispersion of resin particles [a1]”.
Second stage polymerization: formation of an intermediate layer In a flask equipped with a stirrer,
Solution (2);
Styrene 94 parts by weight n-butyl acrylate 60 parts by weight Methacrylic acid 11 parts by weight n-octyl mercaptan 5 parts by weight Paraffin wax (melting point: 73 ° C.) 51 parts by weight as a release agent was added, A monomer solution [2] was prepared by heating to 85 ° C. and dissolving.

On the other hand, a surfactant solution in which 2 parts by mass of sodium lauryl sulfate as an anionic surfactant was dissolved in 1100 parts by mass of ion-exchanged water was heated to 90 ° C. After adding 28 parts by mass of the above-prepared “dispersion of resin particles [a1]” in terms of solid content of the resin particles [a1] to this surfactant solution, a mechanical disperser “CLEAMIX” having a circulation path is added. (M Technique Co., Ltd.) mixed and dispersed the monomer solution [2] for 4 hours to prepare a dispersion containing emulsified particles having a dispersed particle diameter of 350 nm. To this dispersion, an initiator aqueous solution in which 2.5 parts by mass of potassium persulfate (KPS) as a polymerization initiator was dissolved in 110 parts by mass of ion-exchanged water was added, and this system was heated at 90 ° C. for 2 hours. Polymerization (second stage polymerization) was performed by stirring to prepare “dispersion of resin particles [a11]”.
-Third stage polymerization: formation of outer layer In the above-mentioned "dispersion of resin particles [a11]", 2.5 parts by mass of potassium persulfate (KPS) as a polymerization initiator was dissolved in 110 parts by mass of ion-exchanged water. Aqueous agent aqueous solution is added and under the temperature condition of 80 ° C.
Solution (3);
Styrene 230 mass parts n-butyl acrylate 100 mass parts n-octyl mercaptan Solution (3) which consists of 5.2 mass parts was dripped over 1 hour. After completion of the dropwise addition, polymerization (third stage polymerization) was performed by heating and stirring for 3 hours. Then, it cooled to 28 degreeC and prepared "the resin particle dispersion liquid (A1) for cores."

<Preparation of resin particle dispersion (B1) for core> (Polyester resin particles)
Synthesis of crystalline polyester resin [b1] In a 5 L reaction vessel equipped with a stirrer, a temperature sensor, a cooling tube and a nitrogen introducing device, 300 parts by mass of polycarboxylic acid: sebacic acid (molecular weight 202.25), Monohydric alcohol: 170 parts by mass of 1,6-hexanediol (molecular weight 118.17) was charged, and while stirring this system, the internal temperature was raised to 190 ° C. over 1 hour, and the system was uniformly stirred. After confirming that it was present, Ti (OBu) ₄ was added as a catalyst in an amount of 0.003% by mass relative to the charged amount of polyvalent carboxylic acid. Thereafter, the internal temperature is raised from 190 ° C. to 240 ° C. over 6 hours while distilling off the generated water, and the dehydration condensation reaction is continued over 6 hours under the condition of a temperature of 240 ° C. for polymerization. As a result, a crystalline polyester resin [b1] was obtained.
-Synthesis | combination of crystalline polyester resin particle dispersion (B1) 100 mass parts of obtained crystalline polyester resins [b1] were dissolved in 400 mass parts of ethyl acetate.

  Subsequently, 25 mass parts of 5.0 mass% sodium hydroxide aqueous solution was added, and the resin solution was prepared. This resin solution was put into a container having a stirrer, and 638 parts by mass of a 0.26% by mass aqueous sodium lauryl sulfate solution was added dropwise over 30 minutes while stirring the resin solution. During the dropping of the sodium lauryl sulfate aqueous solution, the liquid in the reaction vessel became cloudy, and after the entire amount of the sodium lauryl sulfate aqueous solution was dropped, an emulsion was formed in which the resin solution particles were uniformly dispersed.

  Next, the emulsion was heated to 40 ° C., and using a diaphragm vacuum pump “V-700” (manufactured by BUCHI), ethyl acetate was distilled off under a reduced pressure of 150 hPa. Dispersion (B1) "was obtained.

<Preparation of Resin Particle Particle Dispersion (C1)> (Styrene-acrylic modified polyester resin particles)
-Synthesis of amorphous polyester resin [c1] In a four-necked flask with a capacity of 10 liters equipped with a nitrogen introduction tube, a dehydration tube, a stirrer and a thermocouple,
Bisphenol A propylene oxide 2 mol adduct 500 parts by mass Terephthalic acid 86 parts by mass Fumaric acid 73 parts by mass Adipic acid 40 parts by mass Esterification catalyst (tin octylate) 2 parts by mass Furthermore, after reacting at 8 kPa for 5 hours and cooling to 160 ° C.,
Acrylic acid 10 parts by weight Styrene 162 parts by weight Butyl acrylate 42 parts by weight Polymerization initiator (di-t-butyl peroxide) 10 parts by weight of the mixture was dropped with a dropping funnel over 1 hour, and maintained at 160 ° C. after dropping. After the addition polymerization reaction was continued for 1 hour, the temperature was raised to 200 ° C. and held at 10 kPa for 1 hour, and then acrylic acid, styrene, and butyl acrylate were removed to bond the styrene acrylic segment and the polyester segment. Amorphous polyester resin [c1] was obtained.
-Synthesis | combination of amorphous polyester resin particle dispersion (C1) 100 mass parts of obtained amorphous polyester resins [c1] were dissolved in 400 mass parts of ethyl acetate.

  Subsequently, 25 mass parts of 5.0 mass% sodium hydroxide aqueous solution was added, and the resin solution was prepared. This resin solution was put into a container having a stirrer, and 638 parts by mass of a 0.26% by mass aqueous sodium lauryl sulfate solution was added dropwise over 30 minutes while stirring the resin solution. During the dropping of the sodium lauryl sulfate aqueous solution, the liquid in the reaction vessel became cloudy, and after the entire amount of the sodium lauryl sulfate aqueous solution was dropped, an emulsion was formed in which the resin solution particles were uniformly dispersed.

  Next, the emulsion was heated to 40 ° C., and ethyl acetate was distilled off under a reduced pressure of 150 hPa using a diaphragm vacuum pump “V-700” (manufactured by BUCHI). Dispersion (C1) "was obtained.

<Preparation of Shell Resin Particle Dispersions (C2) to (C10)> (Styrene-acrylic modified polyester resin particles)
-Synthesis of amorphous polyester resin [c2] to [c12] In the synthesis of amorphous polyester resin [c1], the same composition except that the monomer composition, pressure and reaction time were changed as shown in Table 1 below. Resin polyester resins [c2] to [c12] were synthesized.

Synthesis of Amorphous Polyester Resin Particle Dispersions (C2) to (C12) The obtained amorphous polyester resins [c2] to [c12] were obtained in the same manner as the amorphous polyester resin fine particle dispersion (C1). The “resin particle dispersions for shell (C2) to (C12)” were obtained.

<Preparation of Toner 1>
-Preparation of toner base particle dispersion 1 (aggregation / fusion process)
Into a reaction vessel equipped with a stirrer, a temperature sensor, and a cooling pipe, 288 parts by mass of the above-prepared “resin particle dispersion (A1)” prepared in the above in terms of solid content and 2000 parts by mass of ion-exchanged water are added. The pH was adjusted to 10 at 25 ° C. by adding a mol / liter aqueous sodium hydroxide solution. Thereafter, 40 parts by mass of the “colorant particle dispersion” was added in terms of solid content.

  Next, an aqueous solution in which 60 parts by mass of magnesium chloride was dissolved in 60 parts by mass of ion-exchanged water was added over 10 minutes at 30 ° C. with stirring.

Thereafter, the temperature was raised after being allowed to stand for 3 minutes, and the temperature of the system was raised to 80 ° C. over 60 minutes, and the particle growth reaction was continued while maintaining 80 ° C. In this state, the particle size of the associated particles was measured with “Coulter Multisizer 3” (manufactured by Coulter Beckman). When the median diameter (D ₅₀ ) on the volume basis became 6.0 μm, “resin particles for shell” Dispersion (C1) ”was added in 72 parts by mass in terms of solid content over 30 minutes, and when the supernatant of the reaction solution became transparent, an aqueous solution in which 190 parts by mass of sodium chloride was dissolved in 760 parts by mass of ion-exchanged water. Was added to stop grain growth.

Further, the temperature is raised and the mixture is heated and stirred in a state of 90 ° C. to advance the fusing of the particles, and the average circularity measurement apparatus “FPIA-2100” (manufactured by Sysmex) is used (HPF detection) When the average circularity reached 0.945, the mixture was cooled to 30 ° C. to prepare “Toner Base Particle Dispersion 1”.
-Washing step and drying step The obtained toner base particle dispersion 1 was subjected to solid-liquid separation with a centrifugal separator to form a wet cake of toner base particles. The wet cake was washed with ion-exchanged water at 35 ° C. until the electric conductivity of the filtrate reached 5 μS / cm in the centrifuge. Thereafter, the toner was transferred to a “flash jet dryer” (manufactured by Seishin Enterprise Co., Ltd.) and dried until the water content became 0.5 mass% to prepare “toner base particle 1”.
External additive treatment step As a hydrophobic silica, 1% by mass of the toner base particle 1 having a number average primary particle size of 12 nm and 0.3% by mass of a number average primary particle size of 80 nm are used. Using this mixed system, hydrophobic silica and hydrophobic titania (number average primary particle size = 20 nm) 0.3% by mass of this mixed system were added and mixed with a Henschel mixer to prepare “Toner 1”. .

<Preparation of Toners 2 to 18>
In the production of the toner 1, toners 2 to 18 were produced in the same manner except that the core resin particle dispersion and the shell resin particle dispersion were changed as shown in Table 2 below.

<Preparation of developers 1 to 18>
100 parts by mass of ferrite core and 5 parts by mass of copolymer resin particles of cyclohexyl methacrylate / methyl methacrylate (copolymerization ratio 5/5) are put into a high-speed mixer equipped with stirring blades and stirred and mixed at 120 ° C. for 30 minutes. Then, a resin coat layer was formed on the surface of the ferrite core by the action of mechanical impact force to obtain a carrier having a volume-based median diameter of 50 μm.

  The volume-based median diameter of the carrier was measured by a laser diffraction particle size distribution measuring apparatus “HELOS” (manufactured by Sympathic) equipped with a wet disperser.

  Toners 1 to 18 are added to the carrier so as to have a toner concentration of 6% by mass, charged into a micro-type V-type mixer (Tsujii Chemical Co., Ltd.), mixed at a rotational speed of 45 rpm for 30 minutes, and developed. 1-18 were produced.

[Molecular weight measurement]
As a method for measuring the molecular weight of a resin by GPC (gel permeation chromatography), a measurement sample is dissolved in tetrahydrofuran so as to have a concentration of 1 mg / ml. As dissolution conditions, it is carried out at room temperature for 10 minutes using an ultrasonic disperser. Next, after processing with a membrane filter having a pore size of 0.2 μm, 10 μl of the sample solution is injected into the GPC. Specific examples of GPC measurement conditions are shown below.

Apparatus: HLC-8220 (manufactured by Tosoh)
Column: TSKguardcolumn + TSKgelSuperHZM-M3 series (manufactured by Tosoh Corporation)
Column temperature: 40 ° C
Solvent: Tetrahydrofuran Flow rate: 0.2 ml / min
Detector: Refractive index detector (RI detector)
In the measurement of the molecular weight of a sample, the molecular weight distribution of the sample is calculated using a calibration curve measured using monodisperse polystyrene standard particles. Ten polystyrenes were used for calibration curve measurement.

  The main peak molecular weight refers to the peak top molecular weight of the peak with the highest frequency in the measurement range.

[Evaluation method]
<Rubbing fixability>
Evaluation was performed by sequentially loading the developer prepared above into a developing device of a commercially available color copying machine “bizhub PRO C6500” (manufactured by Konica Minolta Co., Ltd.). The fixing temperature, the toner adhesion amount, the system speed, and the fixing device cooling device have been modified so that they can be freely set and removed. A fixing experiment in which a paper having a basis weight of 75 g is used as an evaluation paper and a half-tone image is fixed at a fixing speed of 300 mm / sec is set within a range of 180 to 210 ° C. on the upper fixing belt and 20 ° C. below the upper belt. The test was performed while changing the level to every 10 ° C. Next, the obtained fixed image was rubbed with a “JK wiper” (manufactured by Crecia Co., Ltd.) under a load of 3 kgf, the brightness of the JK wiper before and after that was measured, and the rub fixing property was evaluated from the difference value. In any temperature range, if the difference value of brightness before and after rubbing was less than 5, it was judged as acceptable. Note that a spectrophotometer “Gretag Macbeth Spectrolino” (manufactured by Gretag Macbeth) was used for the lightness measurement.

(Criteria)
◎: less than 1,
○: 1 to less than 3,
Δ: 3 or more and less than 5
X: 5 or more.

<Paper stain>
The developer produced above was sequentially loaded into the developing device of the color copying machine “bizhub PRO C6500” (manufactured by Konica Minolta Co., Ltd.), and 100 half-tone images were printed on the entire surface using 75 g basis weight paper as evaluation paper. A white paper was printed, and the density of the white paper of the transfer material was measured to evaluate the paper stain. The white paper density of the transfer material is measured at 20 points of A4 size, and the average value is defined as the white paper density. Density measurement was performed using a reflection densitometer “RD-918” (manufactured by Macbeth).

(Criteria)
A: Less than 0.03,
○: 0.03 or more and less than 0.06,
Δ: 0.06 or more and less than 0.10,
X: 0.10 or more.

<Low temperature fixability>
Using the above developer and “bizhub PRO C6500” (manufactured by Konica Minolta Co., Ltd.), using “NPi fine paper (128 g / m ² )” (manufactured by Nippon Paper Industries) as an evaluation paper, the toner adhesion amount is 11.3 g. / M ² solid image at a fixing speed of 300 mm / sec within the upper fixing belt 150 to 200 ° C. range, the lower fixing roller is set 20 ° C. lower than the upper belt and fixed at every 5 ° C. The lower limit fixing temperature that does not occur was evaluated. The lower the fixing minimum temperature, the better the fixing property.

(Criteria)
: Fixing lower limit temperature is less than 150 ° C.
○: Fixing lower limit temperature is 150 ° C. or higher and lower than 160 ° C.,
(Triangle | delta): The minimum fixing temperature is 160 degreeC or more and less than 165 degreeC,
X: The minimum fixing temperature is 165 ° C. or higher.

<Thin paper separability>
Using the above developer and “bizhub PRO C6500” (manufactured by Konica Minolta Co., Ltd.), in an environment of normal temperature and normal humidity (temperature 20 ° C., relative humidity 55%), “OK Kanto + (84.9 g / m ² )” A solid image with a margin of 5 mm at the tip and a fixing temperature of 195 ° C./120° C. (made by Oji Paper Co., Ltd.) was printed with the amount of adhesion varied, and the amount of solid image just before the occurrence of a paper jam (jam) (g / M ² ) was measured, and this was taken as the separation limit adhesion amount and a measure of the thin paper separation performance. The larger this value, the better the separation performance.

(Criteria)
A: 3.5 g / m ² or more,
○: 2.0g / ^{m 2} or more ~3.5g / ^m less than ^2,
△: 1.0g / ^{m 2} or more ~2.0g / ^m less than ^2,
×: less than 1.0g / ^{m 2.}

  The obtained results are shown in Table 3 below.

  From the results shown in Table 3, the toner contains a polyester resin having a number average molecular weight of 4,000 to 7,000, a main peak molecular weight of 7,000 to 12,000, and the toner has a main peak molecular weight of 11,000 or more. An image obtained using an image forming apparatus using a toner and having a fixing device having a cooling means is found to exhibit excellent properties with good balance in rubbing fixing property, paper stain, low temperature fixing property, and thin paper separation property. It was.

  On the other hand, in Comparative Example 1 using the toner 1 containing no polyester resin, the low-temperature fixability cannot be sufficiently obtained. In Comparative Examples 2 and 4 in which the number average molecular weight or main peak molecular weight of the polyester resin is smaller than the specific value of the present invention, and in Comparative Example 6 in which the main peak molecular weight of the toner is smaller than the specific value of the present invention, rubbing Fixability, paper stains, and thin paper separation are not sufficient. In addition, low temperature fixability cannot be obtained in Comparative Example 3 in which the number average molecular weight and main peak molecular weight of the polyester resin are larger than the specific values of the present invention. Further, it was found that in Comparative Example 5 which does not contain a saturated aliphatic dicarboxylic acid as the carboxylic acid component constituting the polyester resin, the rubbing fixability is not sufficient and there is a problem of paper stains.

1Y, 1M, 1C, 1K photosensitive drum,
2Y, 2M, 2C, 2K charging unit,
3Y, 3M, 3C, 3K exposure unit,
4Y, 4M, 4C, 4K development unit,
5 Intermediate transfer belt,
6Y, 6M, 6C, 6K, 6A transcription part,
7Y, 7M, 7C, 7K, 7A Cleaning section,
8 fixing device,
8F fixing frame,
10Y, 10M, 10C, 10K image forming unit,
20 paper cassette,
21 Paper feed unit,
22A, 22B, 22C, 22D Paper feed roller,
23 Registration roller,
24 paper discharge roller,
25 Output tray,
81 fixing belt,
82 heating roller,
82A, 84A halogen heater,
82B, 83A, 84B Core,
82C, 84D resin layer,
83 fixing roller,
83B, 84C elastic layer,
84 Pressure roller,
85 Pressure roller holding plate,
121 the first duct,
121a, 121b, 131a opening 131 second duct,
131b discharge port,
201 automatic document feeder,
202 Document image scanning exposure apparatus,
211 upper guide,
212, 213 Lower guide,
F suction fan,
GH image forming apparatus body,
N nip,
P paper,
R1, R2 transport rollers,
SE temperature detection sensor,
X image forming apparatus,
YS image reader,
d Manuscript.

Claims (4)

A heating member that heats the paper carrying the toner image, a pressure member that fixes the image on the paper by abutting the nip that sandwiches the paper carrying the toner image against the heating member, and discharging from the nip An image forming method using a fixing device having cooling means for cooling the sheet to be separated and separating the sheet from the heating member,
The toner for forming the toner image contains a binder resin containing at least a polyester resin, and contains a saturated aliphatic dicarboxylic acid as a carboxylic acid component of a raw material monomer constituting the polyester resin,
The image forming method, wherein the polyester resin has a number average molecular weight of 4,000 to 7,000 , a main peak molecular weight of 7,000 to 12,000, and a main peak molecular weight of the toner of 11,000 or more.   The image forming method according to claim 1, wherein the polyester resin includes a styrene-acrylic modified polyester resin in which a styrene-acrylic copolymer segment is bonded to an end of a polyester segment.   The image forming method according to claim 2, wherein a content ratio of the styrene-acrylic copolymer segment in the styrene-acrylic modified polyester resin is 5 to 30% by mass.   The image forming method according to claim 1, wherein the cooling unit is a unit that cools the sheet by blowing air from a discharge port to the sheet discharged from the nip portion.