Toner for electrostatic image development and image forming method

Abstract

To provide a toner for electrostatic image development that exhibits excellent low-temperature adhesion and fixation / separation properties with paper and resin media, as well as minimal change in image density even when continuous image formation is performed, and good post-processing properties. [Solution] The above-mentioned electrostatic image developing toner is an electrostatic image developing toner for continuous-form media comprising toner particles containing a release agent including a crystalline polyester resin and an ester wax, and an external additive, wherein the amount of crystalline polyester resin in the electrostatic image developing toner is 0.5% by mass or more and 5% by mass or less, the amount of ester wax in the electrostatic image developing toner is 5% by mass or more and 10% by mass or less, and the external additive has an adhesion strength of 10% or more and 35% or less as measured by a special test method.

Description

Technical Field

[0001] The present invention relates to an electrostatic charge image developing toner for continuous accounting media and an image forming method.

Background Art

[0002] Image forming apparatuses using an electrostatic charge image developing method are widely spread and used in various fields. In such an image forming apparatus, it is common to attach an electrostatic charge image developing toner (simply referred to as "toner") to a recording medium and then heat and press the toner to fix it to the recording medium.

[0003] Image forming apparatuses in which the recording medium is a continuous accounting medium are used for various industrial applications. As the material of the continuous accounting medium, not only paper but also resin may be used. Further, in image formation on the continuous accounting medium, the printing rate is often higher compared to image formation on a single-sheet recording medium. Also, in image formation on the continuous accounting medium, there is no waste burning as in image formation on a single-sheet recording medium, and image formation is continuously performed. Therefore, very high image density stability is required.

[0004] Here, as the electrostatic charge image developing toner, various types of toners have been developed, and for example, an electrostatic charge image developing toner containing a crystalline polyester resin has also been proposed (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Through diligent research, the inventors of this invention discovered that, for example, with conventional positive charge image developing toners as described in Patent Document 1, while image density remained stable at low print density, it became unstable when images were continuously formed at high print density. Furthermore, conventional electrostatic image developing toners struggled to achieve both good fixation to resin media and good fixation to paper media. Moreover, when varnish was applied after image formation, the image tended to repel the varnish, resulting in poor post-processing capabilities.

[0007] The present invention has been made in view of these problems. Specifically, the present invention aims to provide an electrostatic image developing toner for continuous-feed media that has excellent low-temperature adhesion and fixation / separation properties with paper media and resin media, and further exhibits small changes in image density even when continuous image formation is performed, and good post-processing properties, as well as an image forming method using the same. [Means for solving the problem]

[0008] One aspect of the present invention for achieving the above objective is an electrostatic image developing toner for continuous-form media, comprising toner particles containing a mold release agent comprising a crystalline polyester resin and an ester wax, and an external additive, wherein the amount of crystalline polyester resin in the electrostatic image developing toner is 0.5% by mass or more and 5% by mass or less, the amount of ester wax in the electrostatic image developing toner is 5% by mass or more and 10% by mass or less, and the external additive has an adhesion strength of 15% or more and 35% or less as measured by the following test method. (Method for measuring adhesion strength) (i) A dispersion is obtained by dispersing 4 g of electrostatic image developing toner in 40 g of an aqueous polyoxyphenyl ether solution having a polyoxyphenyl ether concentration of 0.2% by mass. (ii) The dispersion is irradiated with ultrasound at a frequency of 15 kHz and a current of 60 μA (50 W) for 2 minutes using an ultrasonic homogenizer. (iii) Identify the elements derived from the external additives in the electrostatic image developing toner before and after ultrasonic irradiation. (iv) Determine the ratio of the external additive in the electrostatic image developing toner after ultrasonic irradiation to the amount of the external additive in the electrostatic image developing toner before ultrasonic irradiation, and define this ratio as the adhesion strength.

[0009] One aspect of the present invention provides an image forming method that includes the step of forming an image on a continuous-print medium containing a resin using the electrostatic image developing toner described above. [Effects of the Invention]

[0010] According to the present invention, an electrostatic image developing toner for continuous-feed media is provided, which has excellent low-temperature adhesion and fixation / separation properties with paper media and resin media, and further exhibits small changes in image density even when continuous image formation is performed, as well as good post-processing properties, and an image forming method using the same. [Modes for carrying out the invention]

[0011] One embodiment of the present invention will be described in detail below. However, the present invention is not limited to this embodiment.

[0012] 1. Toner for developing electrostatic images The electrostatic image developing toner of this embodiment (hereinafter also simply referred to as "developing toner") comprises toner particles and an external additive. This developing toner is mainly used for image formation on continuous-form media, but it can also be used on single-fed recording media. The developing toner of this embodiment may be used as a one-component developer or as a two-component developer. When the developing toner is used as a two-component developer, the developing toner is mixed with a carrier to form the developer.

[0013] The toner particles of the developer toner in this embodiment contain at least a release agent comprising a crystalline polyester resin and an ester wax. The amount of crystalline polyester resin relative to the total developer toner is 0.5% by mass or more and 5% by mass or less. The amount of ester wax relative to the total developer toner is 5% by mass or more and 10% by mass or less. When the release agent in the toner particles contains a desired amount of ester wax, a certain amount of ester groups derived from the ester wax will be included in the resulting image. Therefore, when varnish or lamination is applied to the image, the varnish or resin for lamination interacts with these ester groups. As a result, the varnish or resin is less likely to be repelled and is more likely to adhere. However, if the amount of ester wax is excessively high, post-processing properties tend to decrease. Therefore, in this embodiment, the amount of ester wax relative to the total developer toner is 10% by mass or less.

[0014] Furthermore, when the developing toner contains a certain amount or more of crystalline polyester resin, the low-temperature fixing properties of the developing toner are improved, regardless of whether the continuous form medium is a resin medium or a paper medium.

[0015] Furthermore, in the developer toner of this embodiment, the adhesion strength of the external additive is 15% to 35%. The method for measuring the adhesion strength of the external additive will be described later, but the adhesion strength of the external additive is an indicator of how firmly the external additive adheres to the toner particles in the developer toner before it is set in the image forming apparatus. The higher the value, the more firmly it adheres to the toner particles. As mentioned above, conventional developer toners had the problem of low density stability when forming images on continuous-print media. In response to this, the inventors diligently investigated and found that there is a correlation between the adhesion strength of the external additive and the density stability when forming images on continuous-print media. The external additive in developer toner is usually partially embedded on the surface of the toner particles, and the greater the degree of embedding, the higher the adhesion strength tends to be. Generally, a higher value for the adhesion strength is considered preferable. However, in image forming using continuous-print media, the developer toner is stirred for a long time inside the image forming apparatus. Furthermore, if developer toner with high adhesion strength of external additives is agitated for a long time, the external additives are gradually pushed into the toner particles, and eventually the external additives become embedded within the toner particles. When embedding of the external additives occurs, the external additives do not function properly, leading to problems such as decreased fluidity of the developer toner or blocking of the developer toner. This is thought to contribute to the instability of image density described above. On the other hand, if developer toner with excessively low adhesion strength of external additives is agitated for a long time, the external additives gradually detach, and eventually the toner particles and external additives separate. When the toner particles and external additives separate, the external additives do not function, and in this case too, image density is thought to become unstable. In contrast, if the adhesion strength of the external additives before use (before agitation in the image forming apparatus) is set to 15% to 35%, the external additives are less likely to be completely embedded inside the toner particles even if agitated for a long time in the image forming apparatus. Also, when the adhesion strength is within this range, separation of the external additives and toner particles is less likely to occur. Therefore, the resulting image is less likely to exhibit changes in density.

[0016] In short, the developing toner of this embodiment exhibits excellent low-temperature adhesion and fixation / separation properties with paper and resin media. Furthermore, the resulting images have good post-processing capabilities. Moreover, when images are formed on continuous-feed media, the image density changes minimal, enabling high-quality image formation. Therefore, it can be used for image formation in various industrial fields. The components and physical properties of this developing toner will be described in detail below.

[0017] (1) Toner particles Toner particles are particles generally also called toner matrix particles. These toner particles may contain at least a crystalline polyester resin and a release agent containing ester wax, but in this embodiment, they further contain an amorphous resin. In addition, the toner particles may contain other components such as colorants, release agents, and charge control agents as needed.

[0018] (Crystalline polyester resin) The crystalline polyester resin can be any resin that exhibits crystallinity and contains an ester structure. The toner particles may contain only one type of crystalline polyester resin, or two or more types. In this specification, a resin exhibiting crystallinity means that, in the endothermic curve obtained by DSC, it has a clear endothermic peak rather than a stepwise endothermic change when the temperature rises. More specifically, it means that in the endothermic curve when the temperature is raised at a heating rate of 10°C / min, it has a peak with a full width at half maximum of 15°C or less. The measurement by differential scanning calorimetry (DSC) is performed, for example, using a differential scanning calorimeter (DSC-60A, manufactured by Shimadzu Corporation). The measurement is performed as follows: First, the temperature is raised from room temperature (25°C) to 150°C at a heating rate of 10°C / min, and the temperature is held isothermally at 150°C for 5 minutes (first heating process). Then, the temperature is cooled from 150°C to 0°C at a cooling rate of 10°C / min, and the temperature is held isothermally at 0°C for 5 minutes (cooling process). Furthermore, the temperature is increased from 0°C to 200°C at a heating / lowering rate of 10°C / min (second heating process). Then, the endothermic curve during the second heating process is examined, and if there is an endothermic peak in the endothermic curve with a full width at half maximum of 15°C or less, it is determined that the resin is crystalline.

[0019] Crystalline polyester resins preferably contain polyester structures formed by a polymerization reaction between a divalent or higher carboxylic acid (polycarboxylic acid) and a divalent or higher alcohol (polyhydric alcohol). That is, crystalline polyester resins preferably contain at least structural units derived from polyhydric carboxylic acids and structural units derived from polyhydric alcohols. Polymerization of polyhydric carboxylic acids and polyhydric alcohols can be carried out using known esterification catalysts.

[0020] The polycarboxylic acid usable for polymerization of crystalline polyester resins may be any compound containing two or more carboxyl groups in one molecule, or it may contain three or more. The polycarboxylic acid may be an aromatic polycarboxylic acid, an aliphatic polycarboxylic acid, or an alicyclic polycarboxylic acid containing an alicyclic structure. In this specification, examples of polycarboxylic acids also include derivatives of polycarboxylic acids, i.e., alkyl esters, acid anhydrides, and acid chlorides of polycarboxylic acids. Examples of such polycarboxylic acids 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, terephthalic acid, tetrachlorophthalic acid, chlorophthalic acid, nitrophthalic acid, p-carboxyphenylacetic acid, p-phenylenediacetic acid. This includes divalent carboxylic acids such as m-phenylenediglycolic acid, p-phenylenediglycolic acid, o-phenylenediglycolic acid, diphenylacetic acid, diphenyl-p,p'-dicarboxylic acid, naphthalene-1,4-dicarboxylic acid, naphthalene-1,5-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, anthracenedicarboxylic acid, and dodecenylsuccinic acid; trivalent or higher carboxylic acids such as trimellitic acid, pyromellitic acid, naphthalentricarboxylic acid, naphthalenetetracarboxylic acid, pyrentricarboxylic acid, and pyrenetetracarboxylic acid; and alkyl esters, acid anhydrides, and acid chlorides thereof; etc. The crystalline polyester resin may contain only one of these polyvalent carboxylic acid-derived structures, or it may contain two or more.

[0021] On the other hand, polyhydric alcohols that can be used for polymerization of crystalline polyester resins are any compounds that contain two or more hydroxyl groups in one molecule, and may contain three or more. Furthermore, such polyhydric alcohols may be aromatic polyhydric alcohols, aliphatic polyhydric alcohols, or alicyclic polyhydric alcohols containing alicyclic structures. Examples of polyhydric alcohols include dihydric alcohols such as ethylene glycol, propylene glycol, butanediol, diethylene glycol, hexanediol, cyclohexanediol, octanediol, decanediol, dodecanediol, ethylene oxide adducts of bisphenol A, and propylene oxide adducts of bisphenol A; and trihydric or higher polyols such as glycerin, pentaerythritol, hexamethylolmelamine, hexaethylolmelamine, tetramethylolbenzoguanamine, and tetraethylolbenzoguanamine. The crystalline polyester resin may contain only one of these polyhydric alcohol-derived structures, or it may contain two or more.

[0022] The above combinations of polycarboxylic acids and polyhydric alcohols are not particularly limited, but examples include 1,12-dodecanediol (12 carbon atoms) and sebacic acid (10 carbon atoms); ethylene glycol (2 carbon atoms) and sebacic acid (10 carbon atoms); 1,6-hexanediol (6 carbon atoms) and dodecanedioic acid (12 carbon atoms); 1,9-nonanediol (9 carbon atoms) and dodecanedioic acid (12 carbon atoms); 1,6-hexanediol (6 carbon atoms) and sebacic acid (10 carbon atoms), etc.

[0023] Esterification catalysts used for the polymerization of the above-mentioned polycarboxylic acids and polyhydric alcohols include tin compounds such as dibutyltin oxide and tin(II) 2-ethylhexanoate; titanium compounds such as titanium diisopropylate bistriethanolamine; and others. Esterification co-catalysts may also be used, and examples of such esterification de-catalysts include gallic acid. The amount of esterification catalyst used when polymerizing the above-mentioned polycarboxylic acids and polyhydric alcohols is appropriately selected depending on the type and amount of polyhydric alcohol and polycarboxylic acid.

[0024] Here, the crystalline polyester resin may contain only the structure (crystalline polyester structure) obtained by the polymerization reaction of the polycarboxylic acid monomer and polyhydric alcohol monomer described above. On the other hand, the crystalline polyester resin may consist of a crystalline polyester polymerization segment obtained by polymerizing the polycarboxylic acid monomer and the polyhydric alcohol monomer, and an amorphous polymerization segment which is a polymer of monomers other than polyester resin. In this specification, a crystalline polyester resin having both a crystalline polyester polymerization segment and an amorphous polymerization segment is also referred to as a "hybrid polyester resin". When the crystalline polyester resin is a hybrid polyester resin, the affinity between the crystalline polyester resin and the amorphous resin described later increases. As a result, the low-temperature fixing and fixing separation properties of the developing toner become even better.

[0025] In hybrid polyester resins, the amount of amorphous polymerization segments is not particularly limited, as long as the properties of the crystalline polyester polymerization segments are not impaired. However, from the viewpoint of allowing the properties of the crystalline polyester polymerization segments to be fully exhibited, the amount of amorphous polymerization segments is preferably 0.1 to 30% by mass, and more preferably 0.5 to 20% by mass, relative to the total amount of hybrid polyester resin. When the amount of amorphous polymerization segments is 0.1% by mass or more, the amorphous polymerization segments are more likely to exert their effects. On the other hand, when the amount of amorphous polymerization segments is 30% by mass or less, the properties of the crystalline polyester polymerization segments are less likely to be impaired.

[0026] The bonding configuration of crystalline polyester polymerization segments and amorphous polymerization segments in a hybrid polyester resin is not particularly limited. For example, the hybrid polyester resin may be a block copolymer obtained by block copolymerizing crystalline polyester polymerization segments and amorphous polymerization segments. Alternatively, it may be a graft copolymer in which side chains containing crystalline polyester polymerization segments are bonded to a main chain containing amorphous polymerization segments. The reverse is also possible. Among these, it is preferable that the hybrid polyester resin is a graft copolymer in which the main chain is amorphous polymerization segments and the side chains are crystalline polyester polymerization segments. In other words, it is preferable that the hybrid polyester resin is a graft copolymer with a comb-like structure in which amorphous polymerization segments form the trunk and crystalline polyester polymerization segments form the branches. When the hybrid polyester resin is a graft copolymer with the above-described comb-like structure, the orientation of the crystalline polyester polymerization segments tends to align in one direction. Furthermore, since the crystalline polyester polymerization segments tend to align densely, sufficient crystallinity can be imparted to the hybrid polyester resin. As a result, the crystallinity of the binder resin (crystalline polyester resin and amorphous resin described later) in the developing toner is improved. Therefore, the low-temperature fixing properties of the developing toner tend to improve further.

[0027] Here, the crystalline polyester polymerization segment contained in the hybrid resin can be a polymer obtained by the polymerization reaction of the polycarboxylic acid and polyhydric alcohol described above.

[0028] On the other hand, the amorphous polymerization segment contained in the hybrid polyester resin may be any amorphous resin component. Preferably, the amorphous resin segment is a polymerization segment that has no melting point and a relatively high glass transition temperature (Tg) when differential scanning calorimetry (DSC) is performed on a resin having the same chemical structure and molecular weight as the unit. Specifically, the glass transition temperature (Tg1) in the first heating step of a DSC measurement of a resin having the same chemical structure and molecular weight as the unit is preferably 30°C to 80°C, and particularly preferably 40°C to 65°C.

[0029] The structure of the resin components constituting the amorphous polymerization segment is not particularly limited. Examples include vinyl polymerization segments, urethane polymerization segments, urea polymerization segments, and the like. Among these, vinyl polymerization segments are preferred because their thermoplasticity is easily controllable.

[0030] The vinyl polymerization segment is not particularly limited as long as it is a polymer of a vinyl compound, but considering the plasticity during thermal fixing of toner particles, it is preferable that it has structural units derived from styrene. Furthermore, it is more preferable that the styrene-acrylic polymerization segment has constituent units derived from styrene and constituent units derived from (meth)acrylic acid ester. In this specification, (meth)acrylic means methacrylic, acrylic, or both.

[0031] The styrene-acrylic polymerization segment is a polymer of styrene monomer and (meth)acrylic acid monomer. The styrene monomer in this specification includes, in addition to styrene, structures having known side chains or functional groups in the styrene structure. Furthermore, the (meth)acrylic acid ester monomer in this specification includes, in addition to acrylic acid esters and methacrylic acid esters, acrylic acid ester derivatives and methacrylic acid ester derivatives, etc.

[0032] Specific examples of styrene monomers include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, and pn-dodecylstyrene. These can be used individually or in combination of two or more.

[0033] Furthermore, specific examples of (meth)acrylic acid ester monomers include acrylic acid ester monomers such as methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, and phenyl acrylate; and methacrylic acid ester monomers such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, phenyl methacrylate, diethylaminoethyl methacrylate, and dimethylaminoethyl methacrylate. These can be used individually or in combination of two or more.

[0034] The amount of constituent units derived from styrene monomers in the amorphous polymerization segment is preferably 40 to 90% by mass of the total amount of the amorphous polymerization segment. Furthermore, the amount of constituent units derived from (meth)acrylic acid ester monomers in the amorphous polymerization segment is preferably 10 to 60% by mass of the total amount of the amorphous polymerization segment. By setting the amounts within these ranges, it becomes easier to control the plasticity of the hybrid polyester resin. However, the amorphous polymerization segment may also contain structures derived from any monomer other than the styrene monomers and (meth)acrylic acid ester monomers mentioned above.

[0035] In hybrid polyester resins, it is preferable that the crystalline polyester polymerization segment and the amorphous polymerization segment are bonded together by reactive compounds that are reactive with both. The structures of the reactive compounds are not particularly limited, but it is preferable that they are compounds having a functional group that can react with hydroxyl groups, carboxyl groups, etc., in the crystalline polyester polymerization segment and a functional group that can polymerize with the ethylenically unsaturated groups contained in the amorphous polymerization segment.

[0036] Specific examples of both reactive compounds include acrylic acid, methacrylic acid, fumaric acid, maleic acid, or hydroxyalkyl (1-3 carbon atoms) esters thereof. From the viewpoint of reactivity in particular, acrylic acid, methacrylic acid, or fumaric acid are preferred as both reactive compounds.

[0037] The amount of structural units derived from both reactive compounds in the hybrid resin is preferably 1 to 10 parts by mass, and more preferably 4 to 8 parts by mass, per 100 parts by mass of the total amount of structural units in the amorphous polymerization segment.

[0038] The weight-average molecular weight (Mw) of the hybrid polyester resin is preferably 3,000 to 100,000, more preferably 4,000 to 50,000, and even more preferably 5,000 to 30,000, from the viewpoint of easily achieving low-temperature fixation of the developing toner. Furthermore, the number-average molecular weight (Mn) of the hybrid polyester resin is preferably 3,000 to 100,000, more preferably 4,000 to 50,000, and particularly preferably 5,000 to 20,000. These weight-average and number-average molecular weights are polystyrene equivalent values ​​measured by gel permeation chromatography (GPC).

[0039] Furthermore, the melting point (Tm) of the hybrid polyester resin is preferably 60 to 90°C, and more preferably 65 to 85°C. When the melting point (Tm) is within this range, the storage stability and low-temperature fixing properties of the developing toner tend to be even better.

[0040] The above-mentioned method for producing the hybrid resin can be a known method. Specific examples include the following three methods. All are useful methods, but method (2) below is particularly preferred.

[0041] (1) A method in which a crystalline polyester polymerization segment is polymerized in advance, both reactive compounds are reacted with the crystalline polyester polymerization segment, and then monomers for forming an amorphous polymerization segment (e.g., aromatic vinyl monomer and (meth)acrylic acid ester monomer) are reacted.

[0042] (2) A method for forming a crystalline polyester polymer segment by first polymerizing an amorphous polymer segment, reacting the amorphous polymer segment with both reactive monomers, and further reacting it with a polycarboxylic acid and a polyhydric alcohol.

[0043] (3) A method in which crystalline polyester polymerization segments and amorphous polymerization segments are polymerized in advance, and both reactive monomers are reacted with them to bond them together.

[0044] Here, whether the crystalline polyester resin is a resin having only a crystalline polyester structure or a hybrid polyester resin, the amount of crystalline polyester resin in the developer toner should be 0.5% by mass or more and 5% by mass or less, and more preferably 1% by mass or more and 3% by mass or less, relative to the total amount of developer toner (total amount of toner particles and external additives). When the amount of crystalline polyester resin is within this range, as described above, the developer toner will adhere more easily regardless of the material of the continuous-feed medium. In this specification, when the crystalline polyester resin is a hybrid polyester resin, the total amount of the hybrid polyester resin, i.e., the "total amount of crystalline polyester polymerization segments and amorphous polymerization segments," is treated as the amount of crystalline polyester resin. The amount of crystalline polyester resin in the developer toner may be determined from the amount charged, but it can also be determined by differential scanning calorimetry, for example.

[0045] (Release agent) The release agent contains at least an ester wax. The release agent may contain only one kind of ester wax or two or more kinds of ester waxes. Further, the release agent may contain components other than the ester wax as long as the objects and effects of the present embodiment are not impaired. However, with respect to the total amount of the release agent, the amount of the ester wax is preferably 85% by mass or more, and more preferably 90% by mass or more.

[0046] The ester wax only needs to have one or more ester structures in the molecule. The ester wax may be any of a monoester, a diester, a triester, and a tetraester. Examples of the ester wax include esters of higher fatty acids and higher alcohols having structures represented by the following general formulas (1) to (3); trimethylolpropane triesters having a structure represented by the following general formula (4); glycerin triesters having a structure represented by the following general formula (5); pentaerythritol tetraesters having a structure represented by the following general formula (6); and the like.

[0047] General formula (1) R 1 -COO-R 2 General formula (2) R 1 -COO-(CH2) n -OCO-R 2 General formula (3) R 1 -OCO-(CH2) n -COO-R 2

[0048] In general formulas (1) to (3), R 1 and R 2 each independently represent a substituted or unsubstituted hydrocarbon group having 13 to 30 carbon atoms, and the number of carbon atoms is more preferably 17 to 22. R 1 and R 2 may be the same or different. n represents an integer of 1 to 30, and 1 to 12 is more preferable. [Chemical formula]

[0049] In general formula (4), R 1 ~R 4 Each of these independently represents a substituted or unsubstituted hydrocarbon group having 13 to 30 carbon atoms, with a more preferable number of carbon atoms being 17 to 22. 1 ~R 4 They may be the same or different.

[0050] [ka]

[0051] In general formula (5), R 1 ~R 3 Each of these independently represents a substituted or unsubstituted hydrocarbon group having 13 to 30 carbon atoms, with 17 to 22 carbon atoms being more preferred. 1 ~R 3 They may be the same or different.

[0052] [ka]

[0053] In general formula (6), R 1 ~R 4 Each of these independently represents a substituted or unsubstituted hydrocarbon group having 13 to 30 carbon atoms, with 17 to 22 carbon atoms being more preferred. 1 ~R 4 They may be the same or they may be different.

[0054] In the above general formulas (1) to (6), R 1 ~R 4The substituents that may be present are not particularly limited as long as they do not hinder the effects of this embodiment. Examples of substituents include linear or branched alkyl groups, alkenyl groups, alkynyl groups, aromatic hydrocarbon ring groups, aromatic heterocyclic groups, non-aromatic hydrocarbon ring groups, non-aromatic heterocyclic groups, alkoxy groups, cycloalkoxy groups, aryloxy groups, alkylthio groups, cycloalkylthio groups, arylthio groups, alkoxycarbonyl groups, aryloxycarbonyl groups, sulfamoyl groups, acyl groups, acyloxy groups, amide groups, carbamoyl groups, ureido groups, sulfinyl groups, alkylsulfonyl groups, arylsulfonyl groups or heteroarylsulfonyl groups, amino groups, halogen atoms, fluorinated hydrocarbon groups, cyano groups, nitro groups, hydroxyl groups, thiol groups, silyl groups, deuterium atoms, and the like.

[0055] Specific examples of monoesters having the structure represented by the general formula (1) above include compounds having the structures represented by the following formulas (1-1) to (1-8). Formula (1-1) CH3-(CH2) 12 -COO-(CH2) 13 -CH3 Formula (1-2) CH3-(CH2) 14 -COO-(CH2) 15 -CH3 Formula (1-3) CH3-(CH2) 16 -COO-(CH2) 17 -CH3 Formula (1-4) CH3-(CH2) 16 -COO-(CH2) 21 -CH3 Formula (1-5) CH3-(CH2) 20 -COO-(CH2) 17 -CH3 Formula (1-6) CH3-(CH2) 20 -COO-(CH2) 21 -CH3 Formula (1-7) CH3-(CH2) 25 -COO-(CH2) 25 -CH3 Formula (1-8) CH3-(CH2) 28 -COO-(CH2) 29 -CH3

[0056] Specific examples of diesters having the structures represented by the above general formulas (2) and (3) include the structures represented by the following formulas (2-1) to (2-7) and (3-1) to (3-3). Formula (2-1) CH3-(CH2) 20 -COO-(CH2)4-OCO-(CH2) 20 -CH3 Formula (2-2) CH3-(CH2) 18 -COO-(CH2)4-OCO-(CH2) 18 -CH3 Formula (2-3) CH3-(CH2) 20 -COO-(CH2)2-OCO-(CH2) 20 -CH3 Formula (2-4) CH3-(CH2) 22 -COO-(CH2)2-OCO-(CH2) 22 -CH3 Formula (2-5) CH3-(CH2) 16 -COO-(CH2)4-OCO-(CH2) 16 -CH3 Formula (2-6) CH3-(CH2) 26 -COO-(CH2)2-OCO-(CH2) 26 -CH3 Formula (2-7) CH3-(CH2) 20 -COO-(CH2)6-OCO-(CH2) 20 -CH3

[0057] Formula (3-1) CH3-(CH2) 21 -OCO-(CH2)6-COO-(CH2) 21 -CH3 Formula (3-2) CH3-(CH2) 23 -OCO-(CH2)6-COO-(CH2) 23 -CH3 Formula (3-3) CH3-(CH2) 19 -OCO-(CH2)6-COO-(CH2) 19 -CH3

[0058] Specific examples of triesters having the structure represented by the general formula (4) above include compounds with the structures represented by the following formulas (4-1) to (4-6).

[0059] [ka]

[0060] Specific examples of triesters having the structure represented by the general formula (5) above include compounds with the structures represented by the following formulas (5-1) to (5-6).

[0061] [ka]

[0062] Specific examples of tetraesters having the structure represented by the general formula (6) above include compounds with the structures represented by the following formulas (6-1) to (6-5).

[0063] [ka]

[0064] Among the above compounds, the ester wax is preferably a monoester from the viewpoint of fixation and separation properties, and behenyl behenate is particularly preferred from the viewpoint of fixation and separation properties.

[0065] The amount of ester wax in the developer toner (the total amount if multiple types of ester wax are included) should be between 5% and 10% by mass, and more preferably between 7% and 10% by mass, relative to the total amount of developer toner (total amount of toner particles and external additives). When the amount of ester wax is within this range, the fixing and separation properties and post-processing properties of the developer toner are improved, as described above. The amount of ester wax in the developer toner may be determined from the amount prepared, but it can also be determined, for example, by differential scanning calorimetry.

[0066] (Amorphous resin) The toner particles of this embodiment typically contain an amorphous resin in addition to the crystalline polyester resin and release agent mentioned above. The amorphous resin functions as a binder resin together with the crystalline polyester resin. When the toner particles contain an amorphous resin, it is easier to obtain appropriate fixing strength in the developing toner, and the resulting image is more likely to have gloss.

[0067] The amorphous resin content is preferably 65% ​​to 95% by mass, and more preferably 70% to 90% by mass, relative to the total amount of crystalline polyester resin, release agent, and amorphous resin. When the amount of amorphous resin is within this range, the low-temperature fixing properties of the developing toner are improved. In addition, the density of the resulting image tends to be higher.

[0068] In this specification, amorphous resin refers to a resin that does not have a melting point and has a relatively high glass transition temperature (Tg) when differential scanning calorimetry (DSC) is performed. The glass transition temperature (Tg) of amorphous resin is preferably 30 to 80°C, and more preferably 40 to 65°C. The glass transition temperature (Tg) can be measured by a differential calorimetry (DSC). Specifically, a first heating process and a cooling process, as well as a second heating process, are performed in the same manner as for the melting point of the crystalline polyester resin described above, and the onset temperature is taken as the glass transition temperature.

[0069] The weight-average molecular weight (Mw) of the amorphous resin is not particularly limited, but is preferably in the range of 2,000 to 150,000, and more preferably in the range of 10,000 to 100,000. This weight-average molecular weight is a polystyrene equivalent value measured by gel permeation chromatography (GPC).

[0070] The type of amorphous resin is not particularly limited, but in this embodiment, amorphous polyester resin or vinyl resin is preferred, and it is especially preferred to include both. Styrene-acrylic resin and amorphous polyester resin will be described below, but amorphous resins are not limited to these.

[0071] <Styrene-acrylic resin> Styrene-acrylic resins are formed by addition polymerization of styrene monomers and (meth)acrylic acid ester monomers. The styrene monomers referred to here include not only styrene but also structures having known side chains or functional groups within the styrene structure. Furthermore, the (meth)acrylic acid ester monomers referred to here include not only acrylic acid esters and methacrylic acid esters, but also acrylic acid ester derivatives and methacrylic acid derivatives. The styrene monomers and (meth)acrylic acid ester monomers are the same as those described in the amorphous polymerization segment of crystalline polyester resins above.

[0072] Furthermore, styrene-acrylic resin may contain constituent units derived from vinyl monomers other than styrene monomers and (meth)acrylic acid ester monomers. Examples of these monomers include olefins such as ethylene, propylene, and isobutylene; vinyl esters such as vinyl propionate, vinyl acetate, and vinyl benzoate; vinyl ethers such as vinyl methyl ether and vinyl ethyl ether; vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone, and vinyl hexyl ketone; N-vinyl compounds such as N-vinylcarbazole, N-vinylindole, and N-vinylpyrrolidone; vinyl compounds such as vinylnaphthalene and vinylpyridine; and other compounds such as acrylic acids or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide.

[0073] Furthermore, the styrene-acrylic resin may contain structural units derived from vinyl monomers having carboxyl groups. Examples of vinyl monomers having carboxyl groups include acrylic acid, methacrylic acid, maleic acid, itaconic acid, cinnamic acid, fumaric acid, monoalkyl maleic acid, and monoalkyl itaconic acid. Among these, acrylic acid or methacrylic acid is preferred. The styrene-acrylic resin may also have a crosslinked structure.

[0074] The amount of styrene-derived structural units in the styrene-acrylic resin is preferably 40 to 95% by mass, and more preferably 50 to 80% by mass, relative to the total amount of structural units in the styrene-acrylic resin. Furthermore, the amount of structural units derived from (meth)acrylic acid ester monomers is preferably 5 to 60% by mass, and more preferably 20 to 50% by mass, relative to the total amount of structural units in the styrene-acrylic resin.

[0075] The molecular weight of the styrene-acrylic resin is preferably in the range of 2,000 to 1,000,000 in terms of weight-average molecular weight (Mw). When the weight-average molecular weight (Mw) of the styrene-acrylic resin is within this range, the fixation stability tends to be even better. This weight-average molecular weight is the polystyrene equivalent value measured by gel permeation chromatography (GPC).

[0076] Furthermore, the amount of styrene-acrylic resin relative to the total amount of binder resin (crystalline polyester resin and amorphous resin) is preferably 50 to 95% by mass, from the viewpoint of suppressing the temperature dependence of the gloss of the resulting image and achieving low-temperature fixation.

[0077] <Amorphous polyester resin> The amorphous polyester resin may contain only the structure (amorphous polyester) obtained by the polymerization reaction of polycarboxylic acid and polyhydric alcohol. On the other hand, the amorphous polyester resin may also be a resin containing amorphous polyester polymerization segments and amorphous polymerization segments (hereinafter also referred to as "hybrid amorphous polyester resin"). It is preferable for toner particles to contain hybrid amorphous polyester resin from the viewpoint that they will have good affinity with the above-mentioned styrene-acrylic resin, etc.

[0078] Amorphous polyester resins or amorphous polyester polymerization segments are resins or polymerization segments that do not show a clear endothermic peak in differential scanning calorimetry (DSC).

[0079] Examples of polycarboxylic acids used in these polymerizations include oxalic acid, succinic acid, maleic acid, adipic acid, 6-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, terephthalic acid, tetrachlorophthalic acid, chlorophthalic acid, nitrophthalic acid, p-carboxyphenylacetic acid, p-phenylacetic acid These include dicarboxylic acids such as diacetic acid, m-phenylenediglycolic acid, p-phenylenediglycolic acid, o-phenylenediglycolic acid, diphenylacetic acid, diphenyl-p,p'-dicarboxylic acid, naphthalene-1,4-dicarboxylic acid, naphthalene-1,5-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, anthracenedicarboxylic acid, and dodecenylsuccinic acid; trivalent or higher carboxylic acids such as trimellitic acid, pyromellitic acid, naphthalentricarboxylic acid, naphthalenetetracarboxylic acid, pyrentricarboxylic acid, and pyrenetetracarboxylic acid; and alkyl esters, acid anhydrides, and acid chlorides thereof; etc. These can be used individually or in combination of two or more. Among these, aliphatic unsaturated dicarboxylic acids such as fumaric acid, maleic acid, and mesaconic acid, aromatic dicarboxylic acids such as isophthalic acid and terephthalic acid, succinic acid, and trimellitic acid are preferred.

[0080] Furthermore, examples of polyhydric alcohols used in these polymerizations include dihydric alcohols such as ethylene glycol, propylene glycol, butanediol, diethylene glycol, hexanediol, cyclohexanediol, octanediol, decanediol, dodecanediol, bisphenol A ethylene oxide adduct, and bisphenol A propylene oxide adduct; and trihydric or higher polyols such as glycerin, pentaerythritol, hexamethylolmelamine, hexaethylolmelamine, tetramethylolbenzoguanamine, and tetraethylolbenzoguanamine. These can be used individually or in combination of two or more. Among these, dihydric alcohols such as bisphenol A ethylene oxide adduct and bisphenol A propylene oxide adduct are preferred.

[0081] When the amorphous polyester resin is a hybrid amorphous polyester resin, the content of amorphous polyester polymerization segments is preferably 75 to 98% by mass relative to the total amount of the hybrid amorphous polyester resin. The constituent components and content ratios of each segment in the hybrid amorphous polyester resin can be determined by NMR measurement, methylation reaction Py-GC / MS measurement, etc.

[0082] On the other hand, the amorphous polymerization segment in the hybrid amorphous polyester resin is the same as the amorphous polymerization segment described above for the crystalline polyester resin (hybrid polyester resin), and among these, the styrene-acrylic polymerization segment is preferred. The content of the styrene-acrylic polymerization segment is preferably 5 to 25% by mass relative to the total amount of the hybrid amorphous polyester resin.

[0083] When the amorphous polyester resin is a hybrid amorphous polyester resin, it is preferable that the amorphous polyester polymerization segment and the amorphous polymerization segment are bonded together by both reactive compounds. The types of both reactive compounds are the same as those described for the crystalline polyester resin (hybrid polyester resin) above. Furthermore, the method for preparing the hybrid amorphous polyester resin is the same as the method described for the crystalline polyester resin (hybrid polyester resin) above.

[0084] Furthermore, the amorphous polyester resin may, if necessary, contain other components as long as they do not impair the purpose and effects of this embodiment.

[0085] (Coloring agent) Toner particles may contain a colorant. This colorant may be a known inorganic colorant or an organic colorant. Specific examples of colorants include carbon black, magnetic powder, organic pigments, inorganic pigments, and dyes. Toner particles may contain only one colorant or two or more.

[0086] The amount of colorant relative to the total amount of toner particles is preferably 1 to 30% by mass, and more preferably 2 to 20% by mass. When the amount of colorant is 1% by mass or more, the resulting image is more likely to have the desired color. On the other hand, when the amount of colorant is 30% by mass or less, the amount of amorphous resin, etc., becomes relatively sufficient, and the image fixation tends to be good.

[0087] (Charge control agent) The toner particles may further contain a charge control agent. The charge control agent is a component that enhances the chargeability of the toner particles. Examples of charge control agents include known compounds such as nigrosine dyes, metal salts of naphthenic acid or higher fatty acids, alkoxylated amines, quaternary ammonium salts, azo metal complexes, and metal salicylates. The toner particles may contain only one type of charge control agent, or two or more types.

[0088] The amount of charge control agent is preferably 0.1% by mass or more and 5.0% by mass or less relative to the binder resin (total of crystalline polyester resin and amorphous resin).

[0089] (others) The toner particles may further contain any additional components, such as surfactants and various additives, as needed.

[0090] (Structure of toner particles) Toner particles may have a uniform composition throughout, or they may have a multilayer structure such as a core-shell structure having a core particle and a shell layer covering its surface. The shell layer, which is arranged to cover the core particle, may be arranged to cover only a part of the core particle or to cover the entire surface. The core-shell structure can be confirmed by observing a cross-section of the toner particle using known observation methods such as a transmission electron microscope (TEM) or a scanning probe microscope (SPM).

[0091] When toner particles have a core-shell structure, from the viewpoint of controllability of the dispersion state of the crystalline polyester resin in the toner particles and electrostatic properties, it is preferable that the styrene-acrylic resin (amorphous resin) and the crystalline polyester resin constitute the core portion, and either amorphous resin constitutes the shell layer. In particular, it is more preferable that the styrene-acrylic resin and the crystalline polyester resin constitute the core portion, and the amorphous polyester resin or hybrid amorphous polyester resin constitutes the shell layer. In particular, it is preferable that the styrene-acrylic resin and the crystalline polyester resin constitute the core portion, and the hybrid amorphous polyester resin constitutes the shell layer.

[0092] In the case of a core-shell structure, the core particles and the shell layer can have different properties such as glass transition temperature, melting point, and hardness, allowing for the design of toner particles tailored to specific purposes. For example, a shell layer may be formed by agglomerating and fusing a resin with a relatively high glass transition temperature (Tg) onto the surface of core particles containing a binder resin (crystalline polyester resin and amorphous resin), a colorant, a mold release agent, etc., which have a relatively low glass transition temperature (Tg). In this case, it is preferable that the shell layer contains the amorphous polyester resin mentioned above.

[0093] Furthermore, the average particle size of the toner particles is preferably 3 μm to 10 μm in volume average particle size (D50% diameter), and more preferably 5 μm to 8 μm. This volume average particle size is the value measured by the method described above. When the volume average particle size of the toner particles is within this range, high reproducibility can be obtained even for very small dot images at the 1200 dpi level.

[0094] Furthermore, from the viewpoint of improving the stability of the charging characteristics and low-temperature fixation, the average circularity of the toner particles is preferably in the range of 0.930 to 1.000, and more preferably in the range of 0.950 to 0.995. If the average circularity is within the above range, individual toner particles become less likely to break down. This suppresses contamination of the triboelectric charging member, stabilizes the charging properties of the toner, and improves the image quality of the formed image.

[0095] The average circularity of toner particles can be measured using the FPIA-3000 (Sysmex). Specifically, the sample (toner particles) is soaked in an aqueous solution containing a surfactant and dispersed by ultrasonic dispersion treatment for 1 minute. Then, using the FPIA-3000 (Sysmex), images are taken in HPF (high magnification imaging) mode at an appropriate density with an HPF detection count of 3000 to 10000 particles. From the captured particle images, the circularity of each toner particle is calculated according to the following formula, and the average circularity is obtained by adding the circularity of each toner particle and dividing by the total number of toner particles. Circularity = (Perimeter of a circle with the same projection area as the particle image) / (Perimeter of the particle projection image)

[0096] (Method for manufacturing toner particles) The toner particles described above can be prepared by the following methods, but are not limited to these methods. A dispersion of amorphous resin, a dispersion of crystalline polyester resin, and, if necessary, a dispersion of colorant and a dispersion of mold release agent are prepared. At this time, it is preferable that the amorphous resin, crystalline polyester resin, colorant, and mold release agent exist as fine particles in their respective dispersions. The volume-average particle diameter (D50% diameter) of the amorphous resin fine particles in the amorphous resin dispersion is preferably 50 nm to 500 nm, and more preferably 50 nm to 250 nm. On the other hand, the volume-average particle diameter (D50% diameter) of the crystalline polyester resin fine particles in the crystalline polyester resin dispersion is preferably 50 nm to 500 nm, and more preferably 50 nm to 250 nm. When the volume-average particle diameter (D50% diameter) of these fine particles is within this range, the amorphous resin and crystalline polyester resin can be easily mixed by heating, as described later.

[0097] Furthermore, the volume-average particle size (D50% diameter) of the colorant fine particles in the colorant dispersion is preferably 50 nm to 300 nm, and more preferably 50 nm to 200 nm. In addition, the volume-average particle size (D50% diameter) of the release agent fine particles in the release agent dispersion is preferably 50 nm to 500 nm, and more preferably 50 nm to 300 nm. When other additives are used, it is preferable to prepare the dispersion so that it has substantially the same volume-average particle size (D50% diameter) as described above. This makes it easier to disperse them in the toner particles.

[0098] Subsequently, the above dispersion is mixed, and particles are formed by emulsification and agglutination. Specifically, amorphous resin microparticles (dispersion), crystalline polyester resin microparticles (dispersion), colorant microparticles (dispersion), release agent microparticles (dispersion), and surfactants are mixed, and an aqueous medium is further mixed. By stirring the aqueous medium, the microparticles of each component agglutinate and become particulate. At this time, the structure of the toner particles can be controlled by adjusting the order in which each microparticle (dispersion) is added. For example, core particles can be prepared by first agglutinating styrene-acrylic resin microparticles, crystalline polyester microparticles, colorant microparticles, and release agent microparticles, and then amorphous polyester resin dispersion is added to further agglutinate amorphous polyester resin microparticles around the core particles, thereby forming a shell layer containing amorphous polyester resin.

[0099] Then, once the particles generated in the aqueous medium have reached the desired particle size and composition, the dispersion is heated to fuse the fine particles within each particle. The heating temperature at this time is preferably 30°C to 90°C, and more preferably 40°C to 90°C. The heating time at this time is more preferably 10 minutes to 600 minutes, and more preferably 30 minutes to 500 minutes. As a result, the amorphous polyester resin fine particles soften or the amorphous polyester resin melts, and the components mix together.

[0100] Subsequently, the dispersion is cooled to room temperature (e.g., 20°C). The cooling rate at this time is preferably 50°C / min to 100°C / min, and more preferably 60°C / min to 100°C / min. Methods for cooling at such a relatively fast rate include cooling using a gasket plate heat exchanger or cooling using a brazing plate heat exchanger. Next, the particles (dispersion) cooled above are heated again to a temperature of 50°C to 80°C and subjected to heat treatment for 10 minutes to 200 minutes. This heat treatment promotes crystal growth and changes the aspect ratio. When heating, it is preferable to set the heating rate to 5°C / min to 50°C / min. This suppresses thermal aggregation of particles due to heating. After that, the toner particles described above are obtained by performing solid-liquid separation and drying.

[0101] (2) External additives As described above, the developing toner of this embodiment contains an external additive along with the toner particles, and the adhesion strength of the external additive is preferably 15% to 35%, with the adhesion strength being 15% to 25%. The adhesion strength of the external additive is measured before using the developing toner, that is, before stirring in the developing device.

[0102] The adhesion strength of the above external additive is measured by the following method. (i) First, a dispersion is obtained by dispersing 4 g of developing toner in 40 g of an aqueous polyoxyphenyl ether solution having a polyoxyphenyl ether concentration of 0.2% by mass. (ii) The dispersion is subjected to ultrasonic ultrasonic waves at 15 kHz with a current of 60 μA (50 W) for 2 minutes using an ultrasonic homogenizer. After ultrasonic treatment, the supernatant of the dispersion is removed using a centrifuge and the dispersion is redispersed in pure water, and this process is repeated at least three times to remove the external additives detached from the developing toner. (iii) Identify the elements and amounts of external additives in the developing toner before and after ultrasonic irradiation by analyzing them using an X-ray fluorescence spectrometer (fundamental parameter method). (iv) The adhesion strength is defined as the ratio of the external additive in the developing toner after ultrasonic irradiation to the amount of external additive in the developing toner before ultrasonic irradiation. When calculating the content ratio of elements derived from external additives, all elements derived from external additives are assumed to exist as oxides. For example, if the elements derived from external additives are Si and Ti, they are assumed to exist as SiO2 and TiO2, and the content ratio of external additives in the developer toner is calculated accordingly. Furthermore, if there are multiple elements derived from external additives (in this case, Si and Ti), the content ratios of each are added together (the content ratio of SiO2 and the content ratio of TiO2) to calculate the content ratio of external additives in the developer toner. The adhesion strength is calculated using the following formula. Adhesion strength (%) = {(Percentage of external additives (calculated as oxides) in the developer toner after ultrasonic irradiation) / (Percentage of external additives (calculated as oxides) in the developer toner before ultrasonic irradiation)} × 100 Furthermore, when identifying elements derived from external additives in (iii) above, the type of element derived from the external additive may be identified by analyzing the solid content in the supernatant removed after sonication using an X-ray fluorescence spectrometer.

[0103] Here, the adhesion strength of the external additive can be adjusted, for example, by the shear force when mixing the toner particles and the external additive, or by the mixing temperature. For example, mixing the toner particles and the external additive is usually done with a Henschel mixer. The adhesion strength can be adjusted by adjusting the peripheral speed of the Henschel mixer's impeller. For example, the peripheral speed of the Henschel mixer's impeller is preferably 15 m / s to 45 m / s, and more preferably 20 m / s to 40 m / s. Within this range, the adhesion strength tends to fall within the desired range.

[0104] The type of external additive described above is not particularly limited as long as it can achieve the above adhesion strength. Examples of external additives include inorganic oxide microparticles such as silica microparticles, alumina microparticles, and titanium oxide microparticles; inorganic stearic acid compound microparticles such as aluminum stearate microparticles and zinc stearate microparticles; and inorganic titanate compound microparticles such as strontium titanate and zinc titanate. The toner for electrostatic image development may contain only one of these, or it may contain two or more.

[0105] Among these, it is particularly preferable to include silica as an external additive, wherein the number-average particle diameter measured by SEM observation is 90 nm to 130 nm. More preferably, the number-average particle diameter of the silica is 90 nm to 110 nm. When the electrostatic image developing toner contains these silica particles as an external additive, the adhesion strength of the external additive tends to be within the desired range, and furthermore, the silica can act as a spacer between the toner particles, suppressing aggregation of the toner particles. The above spacer effect is more easily exhibited when the number-average particle diameter is 90 nm or more. On the other hand, when the number-average particle diameter is 130 nm or less, the silica is less likely to detach from the electrostatic image developing toner.

[0106] The amount of external additives added (or the total amount of multiple external additives used) is preferably 0.05% by mass or more and 5% by mass or less, and more preferably 0.1% by mass or more and 3% by mass or less, relative to the total amount of developing toner.

[0107] 2. Developer As described above, the developing toner of this embodiment may be used as a one-component developer, or it may be mixed with a carrier to be used as a two-component developer. When the developing toner is used as a two-component developer, the carrier can be a magnetic particle made of conventionally known materials such as metals such as iron, ferrite, and magnetite; alloys of these metals with metals such as aluminum and lead; and ferrite particles are particularly preferred.

[0108] Furthermore, as carriers, coated carriers in which the surface of magnetic particles is coated with a coating agent such as resin, or dispersed carriers in which fine magnetic powder is dispersed in a binder resin may be used. The volume-average particle diameter (D50% diameter) of the carrier is preferably 20 μm or more and 100 μm or less, and more preferably 25 μm or more and 80 μm or less. The volume-average particle diameter (D50% diameter) of the carrier can be measured using a laser diffraction particle size distribution analyzer such as HELOS (manufactured by SYMPATEC Corporation) equipped with a wet disperser.

[0109] 3.Image forming method The toner particles (or developer) described above can be used by setting them in a known image forming apparatus for continuous-print media. The method of forming the image is the same as known methods, and the image formation (process) can be performed on the continuous-print media while moving it in one direction. Furthermore, after the image formation process, a process of applying varnish or lamination may be performed. These processes may be performed in the same image forming apparatus or in different apparatuses.

[0110] The material of the continuous-print medium used in the image forming method is not particularly limited. Examples of materials for the continuous-print medium include paper, resins such as polypropylene and polyethylene terephthalate, or mixtures thereof. As described above, whether the continuous-print medium is made of resin or paper, the toner particles exhibit good fixation and can form high-quality images. [Examples]

[0111] The following describes specific embodiments of the present invention along with comparative examples, but the present invention is not limited to these. In the embodiments, "parts" and "%" mean "parts by mass" and "mass%" respectively, unless otherwise specified.

[0112] 1. Measurement methods for various physical properties The melting point of the crystalline polyester resin used in the manufacture of each toner, the glass transition temperature of the amorphous resin, the volume-based median diameter of the resin particles and colorant particles, and the weight-average molecular weight (Mw) of the resin were measured as follows.

[0113] (1) Method for measuring the melting point (Tm) of crystalline polyester resin and the glass transition temperature (Tg) of amorphous resin The melting points (Tm) of crystalline polyester resins and the glass transition temperatures (Tg) of amorphous resins were measured using a differential scanning calorimeter (DSC-60A, Shimadzu Corporation) in accordance with ASTM D3418. The melting points of indium and zinc were used for temperature correction of the detector section of the device, and the heat of fusion of indium was used for heat quantity correction. For the measurements, an aluminum pan was used, with an empty aluminum pan set up as a control. First, the temperature was increased at a rate of 10°C / min, held at 150°C for 5 minutes from room temperature, then cooled from 150°C to 0°C using liquid nitrogen at a rate of -10°C / min, and held at 0°C for 5 minutes. The temperature was then increased again from 0°C to 200°C at a rate of 10°C / min. Analysis was performed from the endothermic curve during the second heating cycle. For amorphous resins, the onset temperature was defined as Tg. For crystalline polyester resins, the temperature at the peak top of the endothermic peak was defined as the melting point.

[0114] (2) Method for measuring the median diameter of resin particles and colorant particles based on volume The volume-based median diameter of various resin particles, colorant particles, and release agents was measured using a laser diffraction / scattering particle size distribution analyzer (Microtrac UPA-150, manufactured by Nikkiso Co., Ltd.).

[0115] (3) Method for measuring the weight-average molecular weight (Mw) of each resin The weight-average molecular weight (Mw) of each resin was measured using the gel permeation chromatography (GPC) method described below. A high-speed GPC instrument (HLC-8220, Tosoh Corporation) and column (TSKguardcolumn + TSKgelSuperHZM-M3, Tosoh Corporation) were used, and tetrahydrofuran (THF) was flowed at a flow rate of 0.2 mL / min as the carrier solvent while maintaining the column temperature at 40°C. The sample was sonicated at room temperature (25°C) for 5 minutes using an ultrasonic disperser and dissolved in tetrahydrofuran to a concentration of 1 mg / mL. Next, the sample solution was obtained by processing with a membrane filter with a pore size of 0.2 μm. 10 μL of this sample solution was injected into the instrument together with the carrier solvent and detected using a refractive index detector (RI detector). The molecular weight distribution of the sample was then calculated using a calibration curve of monodisperse polystyrene standard particles. For the preparation of the calibration curve, standard particles (molecular weight 6 × 10⁶) from Pressure Chemical were used. 2 , 2.1 × 10 3 , 4×10 3 , 1.75 × 10 4 , 5.1×10 4, 1.1 × 10 5 , 3.9×10 5 , 8.6×10 5 , 2×10 6 , 4.48×10 6 A calibration curve was created by measuring at least 10 standard polystyrene samples. A refractive index detector was used as the detector.

[0116] (4) Measurement of adhesion strength of external additives The adhesion strength of the external additive was measured using the following method. 4 g of toner was dispersed in 40 g of a 0.2 mass% aqueous solution of polyoxyethyl phenyl ether to obtain a dispersion, which was then mixed. The dispersion was treated with an ultrasonic homogenizer (US-1200T, manufactured by Nippon Seiki Co., Ltd., operating frequency 15 kHz), and the irradiation energy was adjusted so that the current meter attached to the device, which indicates the vibration value, showed 60 μA. After applying ultrasound for 2 minutes, the supernatant of the dispersion was removed using a centrifuge, and the dispersion was redispersed in pure water at least three times to remove the external additive detached from the toner. At this time, the supernatant recovered by the above centrifugation was treated with an evaporator to recover the solid content. The recovered solid content was then measured using an X-ray fluorescence spectrometer to identify the elements derived from the external additive. Based on this, the content ratio of elements derived from external additives in the toner before and after ultrasonic irradiation was determined from the analysis results using an X-ray fluorescence spectrometer; ZSX Primus IV (manufactured by Rigaku Corporation). The content ratio of each element was determined using the fundamental parameter method. From the obtained element content ratios, the content ratio of external additives in the toner before ultrasonic irradiation and the content ratio of external additives in the toner after ultrasonic irradiation were determined. At this time, it was assumed that all external additives existed as oxides, and the content ratio was calculated accordingly. Furthermore, if there were multiple types of elements derived from the external additives, the content ratio of each oxide was calculated and these were summed up. Subsequently, the ratio of the content ratio of elements derived from external additives in the toner after ultrasonic irradiation to the content ratio of elements derived from external additives in the toner before ultrasonic irradiation (content ratio of external additives in the toner after ultrasonic irradiation / content ratio of external additives in the toner before ultrasonic irradiation × 100) was calculated as the adhesion strength of the external additives.

[0117] 2. Toner preparation (1) Preparation of crystalline polyester resin and its dispersion (1-1) Synthesis of crystalline polyester resin c The monomers that will be used as raw materials for the styrene-acrylic polymerization segment below, along with the radical polymerization initiator, were placed in a dropper funnel. 36 parts by mass of styrene n-butyl acrylate 13 parts by mass Acrylic acid 2 parts by mass Radical polymerization initiator (di-t-butyl peroxide) 7 parts by mass

[0118] Furthermore, monomers to be used as raw materials for crystalline polyester polymerization segments were placed in a four-necked flask equipped with a nitrogen gas inlet tube, a dehydration tube, a stirrer, and a thermocouple, and heated to 170°C to dissolve them. Tetradecanedioic acid 440 parts by mass 1,4-Butanediol 153 parts by mass

[0119] Next, under stirring, the raw materials for the styrene-acrylic polymerization segment were added dropwise from the dropping funnel over 90 minutes, and the mixture was allowed to mature for 60 minutes. After that, the unreacted raw materials for the styrene-acrylic polymerization segment were removed under reduced pressure (8 kPa). The amount of raw materials removed at this time was very small compared to the raw materials used in the initial preparation. One part by mass of titanium tetrabutoxide (Ti(OBu)4) was added as a catalyst, and the mixture was heated to 235°C and reacted under atmospheric pressure (101.3 kPa) for 5 hours, followed by a reaction under reduced pressure (8 kPa) for 1 hour. After cooling to 200°C, the mixture was reacted under reduced pressure (20 kPa) for 1 hour to obtain crystalline polyester resin c (hybrid crystalline polyester resin). The obtained crystalline polyester resin had a weight-average molecular weight of 24,500 and a melting point of 75°C.

[0120] (1-2) Preparation of crystalline polyester resin particle dispersion C 100 parts by mass of the crystalline polyester resin c obtained above was dissolved in 400 parts by mass of ethyl acetate. This was then mixed with 638 parts by mass of a pre-prepared 0.26% by mass aqueous solution of sodium dodecyl sulfate. The resulting mixture was subjected to ultrasonic dispersion treatment for 30 minutes at V-LEVEL 300 μA using an ultrasonic homogenizer (US-150T, manufactured by Nippon Seiki Seisakusho Co., Ltd.) while stirring. Subsequently, the ethyl acetate was completely removed under reduced pressure for 3 hours using a diaphragm vacuum pump (V-700, manufactured by BUCHI Co., Ltd.) while being heated to 40°C. This prepared a dispersion of crystalline polyester resin particles C. The median diameter of the crystalline polyester resin particles c in this dispersion was 160 nm by volume.

[0121] (1) Preparation of amorphous polyester resin and its dispersion (2-1) Synthesis of amorphous polyester resin a A mixture of the raw materials for the styrene-acrylic polymerization segment, both reactive compounds (acrylic acid), and polymerization initiator was placed in a dropper funnel in the composition ratios shown below. 80 parts by mass of styrene n-butyl acrylate 20 parts by mass Acrylic acid 10 parts by mass Di-t-butyl peroxide (polymerization initiator) 16 parts by mass

[0122] Meanwhile, the raw materials for the amorphous polyester resin segments described below were placed in a four-necked flask equipped with a nitrogen inlet tube, a dehydration tube, a stirrer, and a thermocouple, and heated to 170°C to dissolve them. Bisphenol A propylene oxide 2 molar adduct: 286 parts by mass Terephthalic acid 67 parts by mass Fumaric acid 47 parts by mass

[0123] While stirring the above mixture, the raw materials for the styrene-acrylic polymerization segment, placed in a dropping funnel, were added dropwise to a four-necked flask over 90 minutes, and the mixture was allowed to mature for 60 minutes. Unreacted monomers were then removed under reduced pressure (8 kPa). Next, 1 part by mass of titanium tetrabutoxide (Ti(OBu)4) was added as an esterification catalyst, and the mixture was heated to 235°C and reacted under atmospheric pressure (101.3 kPa) for 5 hours, followed by 1 hour under reduced pressure (8 kPa). The mixture was then cooled to 200°C, and the reaction was carried out under reduced pressure (20 kPa). Finally, the solvent was removed to obtain amorphous polyester resin a. The weight-average molecular weight of the obtained amorphous polyester resin a was 25,000, and its glass transition temperature was 60°C.

[0124] (2-2) Preparation of amorphous polyester resin particle dispersion A 100 parts by mass of amorphous polyester resin a obtained above was dissolved in 400 parts by mass of ethyl acetate. This solution was mixed with 638 parts by mass of a pre-prepared 0.26% by mass sodium dodecyl sulfate solution. The resulting mixture was subjected to ultrasonic dispersion treatment for 30 minutes at V-LEVEL 300 μA using an ultrasonic homogenizer (US-150T, manufactured by Nippon Seiki Seisakusho Co., Ltd.) while stirring. Subsequently, the ethyl acetate was completely removed under reduced pressure for 3 hours using a diaphragm vacuum pump (V-700, manufactured by BUCHI Co., Ltd.) while stirring, with the mixture heated to 40°C. This yielded amorphous polyester resin particle dispersion A (hybrid amorphous polyester resin particle dispersion for shells) with a solid content of 13.5% by mass. The amorphous polyester resin particles in this dispersion had a median diameter of 160 nm by volume.

[0125] (3) Preparation of a coloring agent particle dispersion A solution was prepared by adding 90 parts by mass of sodium dodecyl sulfate to 1600 parts by mass of deionized water. While stirring, 420 parts by mass of a coloring agent (CI pigment blue 15:3) was gradually added. The solution was dispersed using a stirring device (CLEARMIX®, manufactured by M-Technique Co., Ltd.) to prepare a dispersion of coloring agent particles. The median diameter of the coloring agent particles in the dispersion was 110 nm by volume.

[0126] (4) Preparation of styrene-acrylic resin particle dispersion (4-1) Preparation of Styrene-Acrylic Resin Particle Dispersion B1 A reaction vessel equipped with a stirrer, temperature sensor, condenser, and nitrogen introduction device was charged with a solution of 18 parts by mass of sodium polyoxyethylene(2) dodecyl ether sulfate dissolved in 2500 parts by mass of deionized water, and heated to 80°C. After heating, a mixture of the monomers listed below, a chain transfer agent (n-octyl mercaptan), and a release agent (behenyl behenate) dissolved at 80°C was added. 804 parts by mass of styrene 2-Ethylhexyl acrylate 261 parts by mass Methacrylic acid (MAA) 68 parts by mass n-octyl mercaptan 11 parts by mass Behenyl behenate "WEP-3" (manufactured by NOF Corporation) 67 parts by mass

[0127] A dispersion containing emulsified particles (oil droplets) was prepared by mixing and dispersing for 1 hour using a mechanical disperser with a circulation path (CLEARMIX®, manufactured by M-Technique). To this dispersion, a polymerization initiator solution was added, which consisted of 16 parts by mass of sodium peroxo-disulfate dissolved in 306 parts by mass of deionized water. This system was then heated and stirred at 84°C for 3 hours to obtain styrene-acrylic resin particle dispersion B (styrene-acrylic resin particle dispersion for cores). The styrene-acrylic resin particles B in this dispersion had a volume-based median diameter of 145 nm. The weight-average molecular weight of the obtained styrene-acrylic resin was 35,000, and the glass transition temperature (Tg) was 37°C.

[0128] (4-2) Preparation of Styrene-Acrylic Lipid Particle Dispersions B2-B12 In the preparation of styrene-acrylic resin particle dispersion B1, the type and amount of release agent used were changed as shown in Table 1 below. Otherwise, styrene-acrylic resin particle dispersions B2 to B12 were prepared in the same manner as described above. For styrene-acrylic resin particle dispersion B8, paraffin wax (HNP-51, manufactured by Nippon Seiro Co., Ltd.) was used as the release agent.

[0129] [Table 1]

[0130] (5) Manufacturing of toner for developing (5-1) Manufacturing of developer toner 1 • Manufacturing of toner particles In a reaction vessel equipped with a stirrer, temperature sensor, and cooling tube, 577 parts by mass (solid content) of the styrene-acrylic resin particle dispersion B1 prepared above, 36 parts by mass (solid content), and 500 parts by mass of deionized water were added. The pH was adjusted to 10 by adding a 5 mol / L sodium hydroxide aqueous solution. Furthermore, a solution of 80 parts by mass of magnesium chloride hexahydrate dissolved in 80 parts by mass of deionized water was added over 10 minutes at 30°C while stirring. After standing for 3 minutes, the temperature was raised to 80°C over 60 minutes. Subsequently, 3 parts by mass (solid content) of crystalline polyester resin dispersion C was mixed with 10 parts by mass (solid content) of sodium dodecyldiphenyl ether disulfonate, and this solution was added over 10 minutes. When the supernatant of the reaction mixture became clear, the stirring speed was adjusted so that the particle size growth rate was 0.02 μm / min. Furthermore, when the volume-based median diameter, measured using a particle size distribution analyzer (Coulter Multisizer 3, Beckman Coulter), reached 5.8 μm, the stirring speed was adjusted to stop particle size growth. Next, 60 parts by mass (solid content equivalent) of amorphous polyester resin particle dispersion A was added over 30 minutes. When the supernatant of the reaction solution became clear, an aqueous solution of 80 parts by mass of sodium chloride dissolved in 320 parts by mass of ion-exchanged water was added to stop particle size growth. Next, the temperature was raised to 80°C and the mixture was stirred. Using a flow-type particle image analyzer (FPIA-3000, Sysmex Corporation), when the average circularity reached 0.970, the reaction solution was cooled to 25°C at a cooling rate of 10°C / min to obtain a dispersion of toner particles 1.

[0131] The resulting dispersion was subjected to solid-liquid separation, and the dehydrated toner cake was redispersed in ion-exchanged water at 35°C. This solid-liquid separation process was repeated three times for washing. After washing, the toner particles 1 (volume-based median diameter 5.8 μm) were obtained by drying at 40°C for 24 hours.

[0132] (Adhesion of external additives) To 100 parts by mass of the toner particles 1 obtained above, 1.0 part by mass of hydrophobic silica particles (number mean primary particle size: 12 nm, degree of hydrophobicity: 68) and 1.0 part by mass of sol-gel silica (number mean primary particle size: 110 nm, degree of hydrophobicity: 63) were added. Then, the mixture was mixed for 20 minutes using a Henschel mixer (manufactured by Nippon Coke Industries Co., Ltd.) at a rotor blade peripheral speed of 20 m / sec and an internal temperature of 32°C. After mixing, coarse particles were removed using a sieve with a mesh size of 45 μm to obtain developer toner 1. The adhesion strength of the external additive was 15%.

[0133] (5-2) Manufacturing of Developer Toners 2-16 In the production of developer toner 1, the same procedure as described above was followed, except that the solid content of the styrene-acrylic resin particle dispersion and the crystalline polyester resin particle dispersion and the peripheral speed of the Henschel mixer were changed as shown in Table 2 below, to obtain developer toners 2 to 16. The adhesion strength of each developer toner is shown in Table 2.

[0134] [Table 2]

[0135] 2. Manufacturing of Developers To prepare the developers 1 to 16, each of the developing toners 1 to 16 obtained above was mixed with a ferrite carrier coated with silicone resin and having a volume-average particle size of 30 μm, so that the concentration of each toner was 6% by mass.

[0136] 3. Evaluation Images were formed using the obtained developers, and the low-temperature fixing properties, fixing separation noise, varnish application properties, varnish staining, and image density stability of each developer were evaluated. The results are shown in Table 3.

[0137] (1) Low temperature fixation The above developer was loaded into an image forming apparatus (AccurioLabel 400, manufactured by Konica Minolta). Images were then formed on two continuous-feed media (PPC50 / OPT1 / T38, manufactured by Oji Tack Co., Ltd., and N-Mirror 73 / P22 / L8W, manufactured by Oji Tack Co., Ltd.) under normal temperature and humidity conditions (temperature 22°C, humidity 50%RH). At this time, the amount of developer adhering to the image before fixing was 12g / m². 2 The settings were adjusted accordingly. Subsequently, the surface temperature of the fixing heating element was changed in 1°C increments from 130°C to 200°C, and the image was fixed at each temperature. During this process, visual evaluation was performed, and the temperature at which no offset occurred was defined as the minimum fixing temperature. Rank 7: Minimum fixing temperature is below 155°C. Rank 6: Minimum fixing temperature is 155°C or higher but less than 160°C. Rank 5: Minimum fixing temperature is 160°C or higher but less than 165°C. Rank 4: Minimum fixing temperature is 165°C or higher but less than 170°C. Rank 3: Minimum fixing temperature is 170°C or higher but less than 175°C. Rank 2: Minimum fixing temperature is 175°C or higher but less than 180°C. Rank 1: Minimum fixing temperature is 180°C or higher. Furthermore, it was determined that a minimum fixing temperature of less than 180°C (rank 2) indicates sufficient low-temperature fixing capability.

[0138] (2) Fixing separation noise The above developer was loaded into an image forming apparatus (AccurioLabel 400, manufactured by Konica Minolta). Then, under normal temperature and humidity conditions (temperature 22°C, humidity 50%RH), images were formed on continuous-feed media (PPC50 / OPT1 / T38, manufactured by Oji Tack Co., Ltd.). At this time, the amount of developer adhering to the image before fixing was 18 g / m². 2 The settings were adjusted accordingly. Subsequently, the surface temperature of the fixing heating element was set to 200°C, and a solid color image was output. Streaks on the image surface caused by poor fixing and separation in the direction perpendicular to the paper feeding direction were visually evaluated. Rank 4: No streaks Rank 3: A slight line is visible from a specific angle. Rank 2: Lines are visible from a specific angle. Rank 1: Clear lines are visible from any angle. A rank of 2 or higher was considered a passing grade.

[0139] (3) Varnish application The above developer was loaded into an image forming apparatus (AccurioLabel 400, manufactured by Konica Minolta). Then, under normal temperature and humidity conditions (temperature 22°C, humidity 50%RH), images were formed on continuous-feed media (N-Mirror 73 / P22 / L8W, manufactured by Oji Tack Co., Ltd.). At this time, the amount of developer adhering to the image before fixing was 12 g / m². 2 The settings were adjusted to achieve the desired result, and the surface temperature of the fixing and heating element was set to 200°C to print a solid color image. Subsequently, a varnish coater was used to apply UV clear coat (manufactured by Sakata Inx Co., Ltd.) to a thickness of 1 μm, and the coating was applied to 200 m of continuous sheet paper. The processed images were evaluated using the following criteria. Rank 4: No pinholes in a 10cm x 10cm area. Rank 3: One to two tiny pinholes within a 10cm x 10cm area. Rank 2: 3 to 10 tiny pinholes within a 10cm x 10cm area. Rank 1: 11 or more pinholes within a 10cm x 10cm area, or rejected. A rank of 2 or higher was considered a passing grade.

[0140] (4) Varnish stains The above developer was loaded into an image forming apparatus (AccurioLabel 400, manufactured by Konica Minolta). Then, under normal temperature and humidity conditions (temperature 22°C, humidity 50%RH), images were formed on continuous-feed media (N-Mirror 73 / P22 / L8W, manufactured by Oji Tack Co., Ltd.). At this time, the amount of developer adhering to the image before fixing was 12 g / m². 2The settings were adjusted to achieve the desired result, and the surface temperature of the fixing and heating element was set to 200°C to print a solid color image. Subsequently, a varnish coater was used to apply UV clear coat (manufactured by Sakata Inx Co., Ltd.) to a thickness of 1 μm, and the coating was applied to 200 m of continuous sheet paper. After that, the transmittance at 350 nm of the varnish recovered from the varnish vase was measured using a UV-Vis spectrophotometer, and the decrease in transmittance was calculated using the varnish before use as a reference to evaluate the degree of varnish contamination. Rank 7: Transmittance reduction is less than 5% Rank 6: Transmittance reduction is 5% or more but less than 10% Rank 5: Transmittance reduction is between 10% and 15%. Rank 4: Transmittance reduction is between 15% and 20%. Rank 3: Transmittance reduction is between 20% and 25%. Rank 2: Transmittance reduction is between 25% and 30%. Rank 1: Transmittance reduction is 30% or more. A rank of 2 or higher was considered a passing grade.

[0141] (5) Stability of image density The above developer was loaded into an image forming apparatus (AccurioLabel 400, manufactured by Konica Minolta). Then, under normal temperature and humidity conditions (temperature 22°C, humidity 50%RH), images were formed on continuous-feed media (PPC50 / OPT1 / T38, manufactured by Oji Tack Co., Ltd.). At this time, the amount of developer adhering to the image before fixing was 4g / m². 2 The settings were adjusted accordingly. Subsequently, the surface temperature of the fixing heating element was set to 200°C, and a solid image was printed across 200m of continuous paper. The image density at the start and end of image formation was measured using a fluorescence spectrophotometer (FD-7, Konica Minolta Corporation), and the change in image density was evaluated. Rank 7: Image density change is less than 0.05 Rank 6: Image density change is between 0.05 and less than 0.10. Rank 5: Image density change is between 0.10 and less than 0.15. Rank 4: Image density change is between 0.15 and less than 0.20. Rank 3: Image density change is between 0.20 and less than 0.25. Rank 2: Image density change is between 0.25 and less than 0.30. Rank 1: Image density change is 0.30 or greater. A rank of 2 or higher was considered a passing grade.

[0142] 4.Results [Table 3]

[0143] As shown in Table 3 above, when paraffin wax was used as a release agent, the varnish application performance decreased (Comparative Example 1). Furthermore, even when ester wax was included as a release agent, if the amount was small, the adhesion and separation performance was poor, and if it was too large, the varnish application performance was poor (Comparative Examples 2 and 3). In addition, when crystalline polyester resin was not included, the adhesion to Cascoat paper was poor (Comparative Example 4), and when crystalline polyester resin was present in large quantities, the adhesion to polypropylene resin was poor (Comparative Example 5). Moreover, if the adhesion strength of the external additive was too low, varnish staining occurred (Comparative Example 6), and if it was too high, the concentration stability was poor (Comparative Example 7).

[0144] In contrast, the toners of Examples 1 to 9 all exhibited excellent low-temperature fixation, fixation separation, varnish application, and image density stability. [Industrial applicability]

[0145] The electrostatic image developing toner of the present invention exhibits excellent low-temperature adhesion and fixation / separation properties with paper and resin media, and furthermore, even when continuous image formation is performed, it shows little change in image density and has good post-processing properties. Therefore, it is useful for image formation in various industrial fields.

Claims

1. Toner particles containing a release agent comprising crystalline polyester resin and ester wax, External additives and, This is a toner for electrostatic image development for continuous-form media, which includes the following: The amount of crystalline polyester resin in the electrostatic image developing toner is 0.5% by mass or more and 5% by mass or less. The amount of the ester wax in the electrostatic image developing toner is 5% by mass or more and 10% by mass or less. The aforementioned external additive has an adhesion strength of 15% or more and 35% or less, as measured by the following test method. Toner for developing electrostatic images. (Method for measuring adhesion strength) (i) A dispersion is obtained by dispersing 4 g of electrostatic image developing toner in 40 g of an aqueous polyoxyphenyl ether solution having a polyoxyphenyl ether concentration of 0.2% by mass. (ii) The dispersion is irradiated with ultrasound at a frequency of 15 kHz and a current of 60 μA (50 W) for 2 minutes using an ultrasonic homogenizer. (iii) Identify the elements derived from the external additives in the electrostatic image developing toner before and after ultrasonic irradiation. (iv) Determine the ratio of the external additive in the electrostatic image developing toner after ultrasonic irradiation to the amount of the external additive in the electrostatic image developing toner before ultrasonic irradiation, and define this ratio as the adhesion strength.

2. The amount of the crystalline polyester resin is 1% by mass or more and 3% by mass or less. The toner for developing electrostatic images according to claim 1.

3. The aforementioned adhesion strength is 20% or more and 30% or less. The toner for developing electrostatic images according to claim 1.

4. The process includes forming an image on a continuous-print medium containing resin using an electrostatic image developing toner according to any one of claims 1 to 3, Image forming method.

Images