Electrostatic image developing toner, method of manufacturing the same, and image forming method and device using the same

Abstract

To provide an electrostatic image development toner with improved low-temperature fixability while maintaining a good tacking property.SOLUTION: An electrostatic image developing toner is provided, comprising toner base particles containing at least a binder resin, a crystalline additive, and a colorant, the binder resin containing a polymer having a first structural unit represented by a general formula (1) and a second structural unit represented by a specific formula. In the general formula (1), R1 represents a hydrogen atom or methyl group, and R2 represents an alicyclic substituent having 6 to 12 carbon atoms.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a toner for developing electrostatic images, a method for producing the same, and an image forming method and an image forming apparatus using the same. In particular, the present invention relates to a toner for developing electrostatic images that can improve low-temperature fixability, a method for producing the same, and an image forming method and an image forming apparatus using the same. [Background technology]

[0002] As printing volumes have declined in recent years, there has been a growing need for digital printing, which allows for short-run printing. In general, increasing productivity per unit time is crucial to boosting profitability in the printing business. For this reason, increasing print output speeds has also become an essential requirement for digital printing.

[0003] To meet this demand for higher speeds, research has been conducted into toners that can be fixed to media such as paper with a low amount of energy. For example, technical studies have been conducted into low-temperature fixability, which fixes toner images at lower temperatures, and rapid melting of toner (hereinafter also referred to as "sharp melting"). Research has also been conducted into improving the fixing strength of toner. Specific methods include resin design, such as controlling the glass transition temperature and molecular weight distribution, and introducing additives into the toner.

[0004] Toners typically contain a binder resin that functions as a binder. Hereinafter, the binder resin contained in toners is also referred to as the "toner binder." Known binder resins include hybrid resins such as styrene-acrylic resins, polyester resins, and polyester resins with grafted acrylic polymer segments. In response to the above demands, techniques are known for improving low-temperature fixability by improving these binder resins.

[0005] Furthermore, printed materials are output while coming into contact with many transport rollers along the transport path during printing. Contact with these transport rollers and the like causes the printed materials to become charged, resulting in the problem of printed materials electrostatically sticking together. In particular, the faster the printing speed, the shorter the time it takes for the charge to leak, making the above problem more pronounced. Hereinafter, the electrostatic sticking of printed materials together as described above will also be referred to as "electrostatic sticking."

[0006] To address the problem of electrostatic sticking, measures have been taken, such as creating a printing environment that is prone to charge leakage, but these measures have not been sufficient to prevent electrostatic sticking. The present applicant has proposed a technology that uses a resin that is prone to charge leakage as a binder resin (see Patent Document 1). Patent Document 1 discloses a technology that introduces a specific compound that is prone to charge leakage and can maintain low intermolecular forces between polymer chains as a binder resin monomer. It is believed that a toner for developing electrostatic images that includes toner base particles containing such a binder resin can prevent electrostatic sticking. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2022-186013 Summary of the Invention [Problem to be solved by the invention]

[0008] In the technology described in Patent Document 1, isobornyl (meth)acrylate is used as a monomer to be introduced into the binder resin. Hereinafter, isobornyl (meth)acrylate is also referred to as "IBX(M)A." Since IBX(M)A has a bulky substituent, by introducing such a structure, it is possible to keep the intermolecular force between polymer chains low, and it becomes possible to suppress electrostatic sticking.

[0009] Although the technology described in Patent Document 1 can effectively suppress electrostatic sticking, there is still room for further improvement in low-temperature fixability. For example, a toner having an isobornyl substituent with a bulky substituent as described in Patent Document 1 deteriorates in sharp melting properties, and therefore, when printing a darker solid image, a rapid decrease in elasticity is unlikely to occur, and low-temperature fixability may be insufficient.

[0010] The present invention has been made in view of the above problems and circumstances, and aims to provide a toner for developing electrostatic images that can improve low-temperature fixability, a method for producing the toner, and an image forming method and image forming apparatus that use the toner. [Means for solving the problem]

[0011] In order to solve the above-mentioned problems, the present inventors investigated ways to improve the low-temperature fixability of the toner described in Patent Document 1. Specifically, they attempted to improve the low-temperature fixability by introducing an additive into the toner. The additive used had high molecular mobility and was crystalline to maintain the durability of the toner. As a result, the low-temperature fixability was improved, but the compatibility between the binder resin and the additive prevented the additive from crystallizing, resulting in the problem of tacking, in which images stick together at the paper discharge section after fixing. The occurrence of such tacking is thought to result in a decrease in printing efficiency and problems with image quality.

[0012] Therefore, the present inventors discovered that tacking resistance can be improved by copolymerizing a specific monomer with high polarity and minimal steric hindrance in the side chain with a monomer having a bulky substituent such as IBX(M)A, and further introducing a crystalline additive, thereby arriving at the present invention. More specifically, a toner for developing electrostatic images, which includes a binder resin containing a polymer obtained by copolymerizing two specific types of monomers, a crystalline additive, and toner base particles containing a colorant, can achieve both low-temperature fixability and tacking suppression. That is, the above-mentioned problems of the present invention are solved by the following means.

[0013] 1. A toner for developing electrostatic images, comprising toner base particles, the toner base particles contain at least a binder resin, a crystalline additive, and a colorant, The toner for developing electrostatic images, wherein the binder resin contains a polymer having a first structural unit represented by the following general formula (1) and a second structural unit represented by the following general formula (2):

[0014] [ka] [In general formula (1), R1 represents a hydrogen atom or a methyl group, and R2 represents an alicyclic substituent having 6 to 12 carbon atoms.]

[0015] [ka] [In general formula (2), R3 represents a hydrogen atom or a methyl group, and R4 represents a methyl group or an ethyl group.]

[0016] 2. The toner for developing electrostatic images according to item 1, wherein the crystalline additive is at least one selected from the group consisting of fatty acid amides, fatty acid diesters, and fatty acid monoesters.

[0017] 3. The toner for developing electrostatic images according to item 2, wherein the crystalline additive is a fatty acid amide having a linear alkyl group having 18 to 22 carbon atoms as the fatty acid structure.

[0018] 4. The toner for developing electrostatic images according to item 2, wherein the crystalline additive is a fatty acid diester having a linear alkyl group having 18 to 22 carbon atoms as the fatty acid structure.

[0019] 5. The toner for developing electrostatic images according to item 2, wherein the crystalline additive is a fatty acid monoester having a linear alkyl group having 18 to 22 carbon atoms as the fatty acid structure.

[0020] 6. The toner for developing electrostatic images according to item 1 or 2, wherein the polymer has a structural unit different from both the first structural unit and the second structural unit.

[0021] 7. The toner for developing electrostatic images according to item 6, wherein the other structural unit has a structural unit derived from at least one polymerizable monomer selected from the group consisting of styrene, (meth)acrylic acid, and (meth)acrylic acid esters.

[0022] 8. The toner for developing electrostatic images according to item 7, wherein the other structural unit has a structural unit derived from (meth)acrylic acid.

[0023] 9. A method for producing a toner for developing electrostatic images, comprising: step A of copolymerizing a polymerizable monomer represented by the following general formula (3) and a polymerizable monomer represented by the following general formula (4) to obtain a polymer; and step B of forming toner base particles containing the obtained polymer:

[0024] [ka] [In general formula (3), R1 represents a hydrogen atom or a methyl group, and R2 represents an alicyclic substituent having 6 to 12 carbon atoms.]

[0025] [ka] [In general formula (4), R3 represents a hydrogen atom or a methyl group, and R4 represents a methyl group or an ethyl group.]

[0026] 10. A method for producing a toner for developing electrostatic images according to item 9, wherein in step B, the toner base particles are formed containing the polymer obtained in step A, a colorant, and a crystalline additive.

[0027] 11. A method for producing a toner for developing electrostatic images, as described in item 9 or 10, characterized in that step A includes a step of obtaining a dispersion of the polymer, and step B includes a step of mixing the dispersion of the polymer obtained in step A.

[0028] 12. An image forming method comprising the steps of: adhering the electrostatic image developing toner described in item 1 or 2 to a recording medium; and fixing the electrostatic image developing toner adhered to the recording medium to the recording medium.

[0029] 13. An image forming apparatus characterized by having an attachment section that attaches the electrostatic image developing toner described in item 1 or 2 to a recording medium, and a fixing section that fixes the electrostatic image developing toner attached to the recording medium to the recording medium. [Effects of the Invention]

[0030] The above-mentioned means of the present invention can provide a toner for developing electrostatic images capable of improving low-temperature fixability, and a method for producing the same. In particular, the above-mentioned means of the present invention can provide a toner for developing electrostatic images capable of improving low-temperature fixability while maintaining tacking properties, and a method for producing the same. Furthermore, the above-mentioned means of the present invention can provide an image forming method and an image forming apparatus capable of forming an image with excellent low-temperature fixability while maintaining tacking properties.

[0031] The mechanism by which the effects of the present invention are manifested or the mechanism of action is not clear, but is speculated as follows.

[0032] First, in the toner for developing electrostatic images of the present invention, the binder resin contains a polymer having a first structural unit represented by the above general formula (1) and a second structural unit represented by the above general formula (2). The first structural unit is, for example, a structural unit derived from an aliphatic (meth)acrylic acid ester having a bulky substituent. An example of the aliphatic (meth)acrylic acid ester is isobornyl (meth)acrylic acid ester (IBX(M)A). The second structural unit is a structural unit derived from a methyl or ethyl (meth)acrylic acid ester. An example of the methyl or ethyl (meth)acrylic acid ester is methyl (meth)acrylic acid ester (hereinafter also referred to as "M(M)A").

[0033] Here, when IBX(M)A, which easily leaks charge and has low intermolecular forces, is introduced as a binder resin monomer as described in Patent Document 1 for the purpose of suppressing electrostatic sticking, the performance was not deemed sufficient in an evaluation of low-temperature fixability conducted by the present inventors. The reason for this is thought to be that the bulky isobornyl substituent makes the binder resin rigid and makes it difficult for molecular motion to occur, resulting in poor sharp melting properties and making it difficult for a decrease in elasticity to occur when printing a more solid (for example, darker) image.

[0034] Therefore, low-temperature fixability was improved by introducing a crystalline additive. The introduction of a crystalline additive is expected to have the effect of accelerating polymer segment motion through molecular motion at high temperatures, resulting in rapid melting. Furthermore, since the crystalline additive may bleed out with the binder resin during toner fixation, it is desirable to suppress bleed-out and rapidly crystallize it during cooling. To improve low-temperature fixability, it is considered important that the binder resin and the additive are compatible with each other and that the molecular motion of the additive is propagated to the main chain of the polymer.

[0035] When a highly compatible additive (e.g., one with a long-chain alkyl group) was introduced into a binder resin having a structural unit derived from IBX(M)A, the low-temperature fixability was improved, but the occurrence of the tacking phenomenon became a problem. It is thought that the compatibility of the binder resin and the additive, combined with the large steric hindrance in the structure, inhibited crystallization, preventing the crystallization of the additive after fixation.

[0036] Therefore, to achieve both low-temperature fixability and tacking suppression, IBX(M)A was copolymerized as a binder resin monomer with M(M)A, which has high polarity and minimal steric hindrance in the side chain. By incorporating such a copolymer into the binder resin, the additives were adequately finely dispersed and the crystallinity was increased, thereby improving tacking resistance. In particular, the addition of crystalline additives such as higher fatty acid monoesters, higher fatty acid diesters, and higher fatty acid amides effectively increases the additives' adequate fine dispersion and crystallinity. Specifically, the polar groups (esters and amides) of the fatty acids in the crystalline additives interact intermolecularly with the second structural unit derived from M(M)A, while the long carbon chain portion of the fatty acid interacts intermolecularly with the first structural unit derived from IBX(M)A, facilitating the orientation of the additive. It is believed that this allows the crystalline additives to be adequately finely dispersed and the crystallinity to be increased, thereby achieving both low-temperature fixability and tacking suppression.

[0037] Furthermore, the second structural unit derived from M(M)A, which has little steric hindrance, makes it easier for the additive to act on the polymer main chain (i.e., the molecular motion of the additive / polymer is more easily transmitted), improving sharp melting properties and thereby low-temperature fixability. [Brief explanation of the drawings]

[0038] [Figure 1] 1 is a flowchart illustrating an example of an image forming method. [Figure 2] FIG. 2 is a schematic cross-sectional view showing an example of the internal configuration of the image forming apparatus main body. [Figure 3] FIG. 1 is a diagram for explaining a method for evaluating tacking in the examples. [Figure 4] FIG. 1 is a diagram for explaining a method for evaluating tacking in the examples. [Figure 5] FIG. 1 is a diagram for explaining a method for evaluating tacking in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0039] One embodiment of the toner for developing electrostatic images of the present invention is a toner for developing electrostatic images containing toner base particles. Hereinafter, the toner for developing electrostatic images of this embodiment may be simply referred to as "toner." The toner for developing electrostatic images of this embodiment is characterized in that the toner base particles contain at least a binder resin, a crystalline additive, and a colorant, and the binder resin contains a polymer having a first structural unit represented by the following general formula (1) and a second structural unit represented by the following general formula (2). This feature is a technical feature common to or corresponding to each of the following embodiments.

[0040] [ka] [In general formula (1), R1 represents a hydrogen atom or a methyl group, and R2 represents an alicyclic substituent having 6 to 12 carbon atoms.]

[0041] [ka] [In general formula (2), R3 represents a hydrogen atom or a methyl group, and R4 represents a methyl group or an ethyl group.]

[0042] The toner for developing electrostatic images of this embodiment can improve low-temperature fixability, and in particular can improve low-temperature fixability while maintaining tackiness.

[0043] In the toner for developing electrostatic images, the crystalline additive is preferably at least one selected from the group consisting of fatty acid amides, fatty acid diesters, and fatty acid monoesters. Fatty acid amides, fatty acid diesters, and fatty acid monoesters are crystalline materials having a polar moiety and a non-polar (hydrophobic) moiety. Therefore, such crystalline additives are preferred from the viewpoints of low-temperature fixation and suppression of tacking.

[0044] Furthermore, from the viewpoint of achieving both low-temperature fixability and tacking suppression, the crystalline additive for the electrostatic image developing toner is preferably a fatty acid amide having a linear alkyl group with 18 to 22 carbon atoms in the fatty acid structure. From the same viewpoint, it is also more preferable that the crystalline additive is a fatty acid diester having a linear alkyl group with 18 to 22 carbon atoms in the fatty acid structure. From the same viewpoint, it is also more preferable that the crystalline additive is a fatty acid monoester having a linear alkyl group with 18 to 22 carbon atoms in the fatty acid structure. For example, the larger the carbon number, the easier the crystallization is, which is advantageous in terms of tacking suppression. On the other hand, if the carbon number is excessively large and the length of the linear alkyl group increases, thermal motion becomes difficult, which may be disadvantageous for low-temperature fixability. When the fatty acid amide, fatty acid diester, and fatty acid monoester have a linear alkyl group with 18 to 22 carbon atoms as described above, it is possible to effectively achieve both low-temperature fixability and tacking suppression.

[0045] In the toner for developing electrostatic images, the polymer having the first structural unit and the second structural unit may have another structural unit different from either the first structural unit or the second structural unit. For example, the other structural unit preferably has a structural unit derived from at least one polymerizable monomer selected from the group consisting of styrene, (meth)acrylic acid, and (meth)acrylic acid esters. When the other structural unit has a structural unit derived from styrene, the thermal properties (e.g., glass transition temperature) are similar to those of the other monomers, and the alternating copolymerization with the (meth)acrylic acid esters is enhanced. Therefore, the randomization of the monomer sequences in the polymer allows for fine dispersion of crystalline additives, which is advantageous for low-temperature fixation.

[0046] Next, one embodiment of the method for producing a toner for developing electrostatic images of the present invention will be described. Hereinafter, the method for producing a toner for developing electrostatic images of the present embodiment may be simply referred to as the "production method." The production method of the present embodiment is characterized by having a step A of copolymerizing a polymerizable monomer represented by the following general formula (3) and a polymerizable monomer represented by the following general formula (4) to obtain a polymer, and a step B of forming toner base particles containing the obtained polymer.

[0047] [ka] [In general formula (3), R1 represents a hydrogen atom or a methyl group, and R2 represents an alicyclic substituent having 6 to 12 carbon atoms.]

[0048] [ka] [In general formula (4), R3 represents a hydrogen atom or a methyl group, and R4 represents a methyl group or an ethyl group.]

[0049] In the manufacturing method of the present embodiment, in step B, toner base particles containing the polymer obtained in step A, a colorant, and a crystalline additive are preferably formed.

[0050] In the production method of this embodiment, it is preferable that step A includes a step of obtaining a polymer dispersion, and step B includes a step of mixing the polymer dispersions obtained in step A.

[0051] Next, various embodiments of the image forming method and image forming apparatus of the present invention will be described. The image forming method of the present embodiment is characterized by comprising the steps of adhering the electrostatic image developing toner described above to a recording medium and fixing the electrostatic image developing toner adhered to the recording medium to the recording medium. The image forming apparatus of the present embodiment is characterized by comprising an adhering unit that adhering the electrostatic image developing toner described above to a recording medium and a fixing unit that fixes the electrostatic image developing toner adhered to the recording medium to the recording medium. Such an image forming method and image forming apparatus can form an image with excellent low-temperature fixing ability while maintaining tacking properties.

[0052] The present invention, its constituent elements, and embodiments and modes for carrying out the present invention will be described below. In this specification, the symbol "to" is used to mean that the numerical values ​​before and after it are included as the lower and upper limits. In addition, in this specification, "(meth)acrylic acid" includes both acrylic acid and methacrylic acid.

[0053] [Electrostatic image developing toner] Hereinafter, the embodiments of the toner for developing electrostatic images of the present invention will be described in more detail, but the present invention is not limited thereto.

[0054] The electrostatic image developing toner of this embodiment is a toner for developing electrostatic images containing toner base particles, characterized in that the toner base particles contain at least a binder resin, a crystalline additive, and a colorant, and the binder resin contains a polymer having a first structural unit represented by the following general formula (1) and a second structural unit represented by the following general formula (2):

[0055] In this specification, "toner base particles" refer to particles that constitute the base of "toner particles." "Toner base particles" contain at least a binder resin, a crystalline additive, and a colorant, and may contain other components such as a release agent and a charge control agent as necessary. "Toner base particles" are called "toner particles" when external additives are added. "Toner" refers to an aggregate of "toner particles."

[0056] <Binder resin> The binder resin includes a polymer having a first structural unit represented by the following general formula (1) and a second structural unit represented by the following general formula (2). Hereinafter, the "first structural unit represented by general formula (1)" will also be simply referred to as the "first structural unit." Similarly, the "second structural unit represented by general formula (2)" will also be simply referred to as the "second structural unit." Furthermore, the "polymer having the first structural unit and the second structural unit" will also be referred to as a "specific polymer" or simply as a "polymer."

[0057] (first structural unit) The first structural unit is a structural unit represented by the following general formula (1): For example, the first structural unit is a structural unit derived from an alicyclic (meth)acrylic acid ester.

[0058] [ka]

[0059] In the general formula (1), R1 is a hydrogen atom or a methyl group, and R2 is an alicyclic substituent having 6 to 12 carbon atoms.

[0060] R1 in general formula (1) may be a hydrogen atom or a methyl group and is not particularly limited, but is preferably a hydrogen atom from the viewpoint of low-temperature fixability. For example, if R1 is too bulky, it may be difficult for molecular motion to propagate to additives, which may be disadvantageous for low-temperature fixability. By making R1 a hydrogen atom, it becomes easier for molecular motion to propagate to additives, and low-temperature fixability can be further improved.

[0061] R2 in general formula (1) is not particularly limited as long as it is an alicyclic substituent having 6 to 12 carbon atoms, but from the viewpoint of low-temperature fixation, it is preferably an alicyclic substituent having 6 to 10 carbon atoms. For example, when R2 is an alicyclic substituent having 6 to 12 carbon atoms, the effect of suppressing electrostatic sticking is obtained, but if the bulkiness of R2 increases, the glass transition temperature increases, which may be disadvantageous for low-temperature fixation.

[0062] R2 in general formula (1) is more preferably a substituent having an isobornyl skeleton, a cyclohexane skeleton, or an adamantane skeleton as a cyclic skeleton. Among these substituents, those having an isobornyl skeleton or an adamantane skeleton as a cyclic skeleton are even more preferred from the viewpoint of being a bulkier substituent, and an isobornyl group is particularly preferred from the viewpoint of low-temperature fixability.

[0063] The content of the first structural unit in the specific polymer is not particularly limited. For example, the content of the first structural unit is preferably 10 to 80 mass % and more preferably 20 to 70 mass % relative to the total of all structural units constituting the specific polymer. When the content of the first structural unit is 10 to 80 mass %, the crystalline additive can be well finely dispersed.

[0064] (second structural unit) The second structural unit is a structural unit represented by the following general formula (2): For example, the second structural unit is a structural unit derived from methyl(meth)acrylate or ethyl(meth)acrylate.

[0065] [ka]

[0066] In the general formula (2), R3 represents a hydrogen atom or a methyl group, and R4 represents a methyl group or an ethyl group.

[0067] R3 in general formula (2) may be a hydrogen atom or a methyl group, and is not particularly limited, but is preferably a methyl group from the viewpoint of crystallization of the additive. For example, when comparing a hydrogen atom with a methyl group, a methyl group is bulkier as a substituent and is less likely to transmit molecular motion to the additive, which may be disadvantageous in terms of low-temperature fixation. However, when R3 is a hydrogen atom, the interaction is stronger than when R3 is a methyl group, which may be disadvantageous in terms of crystallization of the additive; therefore, when comparing a hydrogen atom with a methyl group, a methyl group is more preferable.

[0068] R4 in general formula (2) may be a methyl group or an ethyl group, and is not particularly limited, but is preferably a methyl group from the viewpoint of stabilizing the crystalline additive. For example, by making R4 a methyl group, the polarity is increased, and the stabilization of the crystalline additive is promoted.

[0069] The content of the second structural unit in the specific polymer is not particularly limited. For example, the content of the second structural unit is preferably 10 to 80 mass% and more preferably 20 to 70 mass% of the total of all structural units constituting the specific polymer. When the content of the second structural unit is 10 to 80 mass%, the crystalline additive can be well finely dispersed.

[0070] There are no particular restrictions on the amounts (compositional ratio) of the first structural unit and the second structural unit contained in the specific polymer. For example, from the viewpoint of stabilizing the crystalline additive, the compositional ratio of the first structural unit and the second structural unit in the specific polymer is preferably 1:9 to 9:1 by mass, more preferably 1:3 to 3:1, and even more preferably 2:3 to 3:2.

[0071] (Third structural unit) In the toner for developing electrostatic images of this embodiment, the "third structural unit" refers to a structural unit that is different from both the first structural unit and the second structural unit among the structural units contained in the specific polymer having the first structural unit and the second structural unit described above.

[0072] For example, it is preferable that the third structural unit has a structural unit derived from at least one polymerizable monomer selected from the group consisting of styrene, (meth)acrylic acid, and (meth)acrylic acid esters (hereinafter also referred to as "third polymerizable monomer").

[0073] Examples of the third polymerizable monomer include styrene-based monomers such as styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o-methoxystyrene, p-methoxystyrene, m-methoxystyrene, o-ethylstyrene, m-ethylstyrene, p-ethylstyrene, o-acetoxystyrene, m-acetoxystyrene, and p-acetoxystyrene; methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, tert-butyl acrylate, isobutyl acrylate (isobutyl acrylate), and acrylic acid. Examples of the acrylate include acrylates such as n-octyl methacrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, and phenyl acrylate; and methacrylates 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, dimethylaminoethyl methacrylate, and diethylaminoethyl methacrylate.

[0074] Furthermore, a monomer having an ionic dissociative group may be used as the third monomer. The monomer having an ionic dissociative group may have, for example, a carboxyl group, a sulfonic acid group, a phosphate group, or the like. Specific examples include acrylic acid, methacrylic acid, maleic acid, itaconic acid, and fumaric acid.

[0075] Among these, styrenes have similar thermal properties, such as glass transition temperature, to other monomers, and also have a high alternating copolymerizability with (meth)acrylic acid esters, which randomizes the arrangement of the monomers in the polymer. This makes it possible to finely disperse crystalline additives, making styrenes advantageous for low-temperature fixing.

[0076] As the (meth)acrylic acid ester, (meth)acrylic acid having a carboxylic acid structure is preferred. The carboxylic acid structure contributes to the stability of polymer particles made of a specific polymer. For example, if the carboxylic acid structure is not present, the particle size of the polymer particles may become large, which may be disadvantageous for low-temperature fixing. In particular, from the viewpoint of suppressing interactions and favoring the crystallization of the crystallization additive, methacrylic acid having a carboxylic acid structure is more preferred.

[0077] For example, the third polymerizable monomer is preferably at least one selected from the group consisting of a styrene-based monomer, acrylic acid, methacrylic acid, and n-butyl acrylate. The third monomer may be used alone or in combination of two or more.

[0078] The content of the third structural unit in the specific polymer is not particularly limited. For example, the content of the third structural unit is preferably 25 to 80% by mass, more preferably 40 to 60% by mass, based on the total of all structural units constituting the specific polymer. Furthermore, for example, when a styrene-based monomer is used as the third polymerizable monomer, the content of the styrene-based monomer as the third structural unit is preferably 10 to 60% by mass, more preferably 15 to 40% by mass, based on the total of all structural units constituting the specific polymer. Furthermore, for example, when (meth)acrylic acid is used as the third polymerizable monomer, the content of (meth)acrylic acid as the third structural unit is preferably 1 to 15% by mass, more preferably 2 to 10% by mass, based on the total of all structural units constituting the specific polymer.

[0079] (peak molecular weight) The specific polymer preferably has a peak molecular weight of 3500 to 35000, more preferably 10000 to 30000, as determined from the molecular weight distribution in terms of polystyrene measured by gel permeation chromatography (GPC). A peak molecular weight within this range is preferable because the polymer has an appropriate melt viscosity during fixing, allowing both good fixing properties and offset resistance to be achieved.

[0080] The "peak molecular weight" refers to the molecular weight corresponding to the elution time of the peak top in the molecular weight distribution. When multiple peaks exist in the molecular weight distribution, the "peak molecular weight" refers to the molecular weight corresponding to the elution time of the peak top with the largest peak area ratio.

[0081] The peak molecular weight of a specific polymer can be measured using the following method. First, a sample to be measured is added to tetrahydrofuran (THF) to a concentration of 1 mg / mL. The mixture is dispersed for 5 minutes using an ultrasonic disperser at room temperature (25°C), and then filtered through a membrane filter with a pore size of 0.2 μm to prepare a sample solution. Next, a GPC system "HLC-8220" (manufactured by Tosoh Corporation) and a column "TSKguard column + TSKgel Super HZM-M triple column" (manufactured by Tosoh Corporation) are used, with tetrahydrofuran as the carrier solvent at a flow rate of 0.2 mL / min. The column temperature is maintained at 40°C. Then, 10 μL of the prepared sample solution is injected into the GPC system together with the carrier solvent, and the molecular weight distribution of the sample to be measured is detected using a refractive index detector (RI detector). The peak molecular weight is measured from the detected molecular weight distribution.

[0082] (Other resins) The toner base particles may contain, as a binder resin, a resin other than the specific polymers described above (hereinafter also referred to as "other resins").

[0083] There are no particular restrictions on the other resins contained in the binder resin, but it is preferable that the binder resin contains, for example, the following resins: That is, it is preferable that at least a styrene-acrylic resin or an amorphous polyester resin is contained, it is more preferable that a styrene-acrylic resin and an amorphous polyester resin are contained, and it is desirable that a crystalline polyester resin is further contained.

[0084] (Crystalline polyester resin) Crystalline polyester resins are resins obtained by polycondensation of divalent or higher carboxylic acids (polycarboxylic acids) and divalent or higher alcohols (polyalcohols). Crystalline polyester resins are a type of crystalline resin. A crystalline resin is a resin that exhibits a clear endothermic peak rather than a stepwise endothermic change in differential scanning calorimetry (DSC). Specifically, a clear melting peak refers to a peak whose half-width during the second heating process is within 15°C in a DSC curve obtained by differential scanning calorimetry of the above-mentioned crystalline polyester resin alone.

[0085] (Melting point of crystalline polyester resin) The melting point of the crystalline polyester resin is preferably 65 to 85°C, more preferably 75 to 85°C. By having the melting point of the crystalline polyester resin within the above range, sufficient low-temperature fixability, transferability, and excellent image storage stability can be obtained. The melting point of the crystalline polyester resin can be controlled by the resin composition. The melting point of the crystalline polyester resin is the peak-top temperature of the melting peak in the second heating process in a DSC curve obtained by differential scanning calorimetry of the above-mentioned crystalline polyester resin alone. When multiple melting peaks exist in the DSC curve, the peak-top temperature of the melting peak with the largest endothermic heat is taken as the melting point.

[0086] The melting point (Tm) of a crystalline polyester resin is the temperature at the top of the endothermic peak and can be measured by DSC using a Diamond DSC (PerkinElmer). Specifically, a sample is sealed in an aluminum pan (KIT No. B0143013) and placed in the sample holder of a Diamond DSC (PerkinElmer) thermal analyzer. The temperature is then cycled through a series of cycles: heating, cooling, and heating. The first heating cycle begins at room temperature (25°C), and the second heating cycle begins at 0°C. The temperature is increased to 150°C at a rate of 10°C / min and held at 150°C for 5 minutes. The cooling cycle begins at 10°C / min and is then lowered from 150°C to 0°C, where it is held for 5 minutes. The melting point is measured as the temperature at the top of the endothermic peak in the endothermic curve obtained during the second heating cycle.

[0087] (Polycarboxylic acid component) The polycarboxylic acid component for forming the crystalline polyester resin is a compound containing two or more carboxy groups per molecule. Specific examples include saturated aliphatic dicarboxylic acids such as succinic acid, sebacic acid, and dodecanedioic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid; aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, and terephthalic acid; trivalent or higher polycarboxylic acids such as trimellitic acid and pyromellitic acid; and anhydrides or alkyl esters of these carboxylic acid compounds having 1 to 3 carbon atoms. The polycarboxylic acid component for forming the crystalline polyester resin is preferably a saturated aliphatic dicarboxylic acid. These may be used alone or in combination of two or more.

[0088] (Polyhydric alcohol component) The polyhydric alcohol component for forming the crystalline polyester resin is a compound containing two or more hydroxyl groups per molecule. Specific examples include aliphatic diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, neopentyl glycol, and 1,4-butenediol; and trihydric or higher polyhydric alcohols such as glycerin, pentaerythritol, trimethylolpropane, and sorbitol. The polyhydric alcohol component for forming the crystalline polyester resin is preferably an aliphatic diol. These may be used alone or in combination of two or more.

[0089] (Method for producing crystalline polyester resin) The method for producing the crystalline polyester resin is not particularly limited, and the crystalline polyester resin can be produced by a general polyester polymerization method in which the above-mentioned polycarboxylic acid and polyhydric alcohol are reacted in the presence of a catalyst. For example, it is preferable to produce the crystalline polyester resin by using a direct polycondensation method or an ester exchange method depending on the type of monomer.

[0090] Furthermore, a linear aliphatic hydroxycarboxylic acid can be used in combination with the polycarboxylic acid and / or polyhydric alcohol. Examples of linear aliphatic hydroxycarboxylic acids for forming the crystalline polyester resin include 5-hydroxypentanoic acid, 6-hydroxyhexanoic acid, 7-hydroxypentanoic acid, 8-hydroxyoctanoic acid, 9-hydroxynonanoic acid, 10-hydroxydecanoic acid, 12-hydroxydodecanoic acid, 14-hydroxytetradecanoic acid, 16-hydroxyhexadecanoic acid, and 18-hydroxyoctadecanoic acid, as well as lactone compounds obtained by cyclizing these hydroxycarboxylic acids, and alkyl esters with alcohols having 1 to 3 carbon atoms. These may be used alone or in combination of two or more.

[0091] Examples of catalysts that can be used in the production of crystalline polyester resins include titanium catalysts and tin catalysts. Examples of titanium catalysts include titanium tetraethoxide, titanium tetrapropoxide, titanium tetraisopropoxide, and titanium tetrabutoxide (Ti(On-Bu)4). Examples of tin catalysts include dibutyltin dichloride, dibutyltin oxide, and diphenyltin oxide.

[0092] The ratio of the polycarboxylic acid component to the polyhydric alcohol component is not particularly limited, but is, for example, as follows: The equivalent ratio [OH] / [COOH] of the hydroxyl group [OH] of the polyhydric alcohol component to the carboxyl group [COOH] of the polycarboxylic acid component is preferably 1.5 / 1 to 1 / 1.5, and more preferably 1.2 / 1 to 1 / 1.2.

[0093] <Coloring agent> The toner base particles contain a colorant, and as the colorant, generally known dyes and pigments can be used.

[0094] Examples of colorants for obtaining black toner include carbon black, magnetic materials, iron-titanium composite oxide black, etc. Examples of carbon black include channel black, furnace black, acetylene black, thermal black, and lamp black.

[0095] Examples of colorants for obtaining yellow toner include dyes such as CI Solvent Yellow 19, 44, 77, 79, 81, 82, 93, 98, 103, 104, 112, and 162; and pigments such as CI Pigment Yellow 14, 17, 74, 93, 94, 138, 155, 180, and 185.

[0096] Examples of colorants for obtaining magenta toner include dyes such as CI Solvent Red 1, 49, 52, 58, 63, 111, and 122; and pigments such as CI Pigment Red 5, 48:1, 53:1, 57:1, 122, 139, 144, 149, 166, 177, 178, and 222.

[0097] Examples of colorants for obtaining cyan toner include dyes such as CI Solvent Blue 25, 36, 60, 70, 93, and 95; and pigments such as CI Pigment Blue 1, 7, 15, 60, 62, 66, and 76.

[0098] The colorants for obtaining the toner of each color may be used alone or in combination of two or more kinds for each color.

[0099] The content of the colorant is preferably in the range of 0.5 to 20% by mass, and more preferably in the range of 2 to 10% by mass, with the total mass of the toner base particles being 100% by mass.

[0100] <Crystalline additives> The toner base particles contain a crystalline additive, which may be any compound having crystallinity, such as an organic compound having a long alkyl chain.

[0101] The crystalline additive is preferably at least one selected from the group consisting of fatty acid amides, fatty acid diesters, and fatty acid monoesters. Fatty acid amides, fatty acid diesters, and fatty acid monoesters are crystalline materials having a polar moiety and a non-polar (hydrophobic) moiety. Therefore, such crystalline additives are preferred from the viewpoints of low-temperature fixation and tacking suppression. Fatty acid amides, fatty acid diesters, and fatty acid monoesters can be used alone or in combination of two or more.

[0102] Furthermore, from the viewpoint of achieving both low-temperature fixability and tacking suppression, it is more preferable that the crystalline additive is a fatty acid amide having a linear alkyl group with 18 to 22 carbon atoms in the fatty acid structure. From the same viewpoint, it is also more preferable that the crystalline additive is a fatty acid diester having a linear alkyl group with 18 to 22 carbon atoms in the fatty acid structure. From the same viewpoint, it is also more preferable that the crystalline additive is a fatty acid monoester having a linear alkyl group with 18 to 22 carbon atoms in the fatty acid structure. For example, the larger the carbon number, the easier the crystallization is, which is advantageous in terms of tacking suppression. On the other hand, if the carbon number is excessively large and the length of the linear alkyl group increases, thermal motion becomes difficult, which may be disadvantageous for low-temperature fixability. When the fatty acid amide, fatty acid diester, and fatty acid monoester have a linear alkyl group with 18 to 22 carbon atoms as described above, it is possible to effectively achieve both low-temperature fixability and tacking suppression.

[0103] The fatty acid amide is not particularly limited, but examples thereof include stearic acid amide, stearic acid stearamide, behenic acid amide, behenic acid stearamide, and arachidic acid amide.

[0104] The fatty acid diester is not particularly limited, but examples thereof include ethylene glycol stearate, ethylene glycol behenate, ethylene glycol arachidate, 1,4-butanediol distearate, 1,4-butanediol dibehenate, 1,6-hexanediol distearate, and 1,6-hexanediol dibehenate.

[0105] The fatty acid monoester is not particularly limited, but examples thereof include behenyl stearate, behenyl arachidate, stearyl stearate, stearyl arachidate, and stearyl behenate.

[0106] The crystalline additive preferably contains at least one of a fatty acid amide and a fatty acid diester. This configuration increases the polarity of the crystalline additive, which facilitates interaction with the first structural unit represented by general formula (1), thereby promoting stabilization.

[0107] It is more preferable that the crystalline additive contains at least a fatty acid amide. By configuring in this way, the polarity of the crystalline additive becomes higher, which facilitates interaction with the first structural unit represented by general formula (1), and more effectively promotes stabilization. Furthermore, fatty acid amides in particular have hydrogen bonding sites between amide groups, which has the advantage of easily promoting crystallization.

[0108] The content of the crystalline additive is preferably in the range of 1 to 15% by mass, more preferably in the range of 3 to 9% by mass, and even more preferably in the range of 5 to 7% by mass, when the total mass of the specific polymer is taken as 100% by mass. If the amount of the crystalline additive is too small, the low-temperature fixation effect may not be fully exhibited. On the other hand, if the amount of the crystalline additive is too large, the tacking suppression effect may not be fully exhibited.

[0109] <Release agent> The toner base particles may contain a release agent, which is preferably a fatty acid ester wax.

[0110] Examples of fatty acid ester waxes include behenyl behenate (behenyl behenate), stearyl stearate (stearyl stearate), behenyl stearate, stearyl behenate, butyl stearate, propyl oleate, hexadecyl palmitate (hexadecyl palmitate), methyl lignocerate (methyl lignocerate), glycerin monostearate (glyceryl stearate), diglyceryl distearate (diglyceryl distearate), pentaerythritol tet Examples of such fatty acid ester waxes include trabehenate (pentaerythritol tetrabehenate ester), diethylene glycol monostearate, dipropylene glycol distearate, sorbitan monostearate, cholesteryl stearate, trimethylolpropane tribehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, tristearyl trimellitate (tristearyl trimellitate), distearyl maleate, methyl triacontanate (methyl triacontanoate), etc. These fatty acid ester waxes can be used alone or in combination of two or more.

[0111] These fatty acid ester waxes may be commercially available products or synthetic products.

[0112] The release agent may also be a wax other than the fatty acid ester wax.

[0113] Examples of waxes other than fatty acid ester waxes include polyolefin waxes such as low molecular weight polyethylene and low molecular weight polypropylene, branched chain hydrocarbon waxes such as microcrystalline wax, long chain hydrocarbon waxes such as paraffin wax and sazol wax, dialkyl ketone waxes such as distearyl ketone, and fatty acid amide waxes such as ethylenediamine behenylamide and trimellitic acid tristearylamide.

[0114] From the viewpoint of a balance between fixability and offset resistance, the content of the release agent is preferably in the range of 1 to 25% by mass, and more preferably in the range of 5 to 20% by mass, when the total of the specific polymers is taken as 100% by mass.

[0115] <Charge control agent> The toner base particles may contain a charge control agent.

[0116] The charge control agent used is not particularly limited as long as it is a substance that can impart a positive or negative charge through frictional charging and is colorless, and various known positively charged charge control agents and negatively charged charge control agents can be used.

[0117] Specifically, examples of positively charged charge control agents include nigrosine dyes such as "Nigrosine Base EX" (manufactured by Orient Chemical Industry Co., Ltd.), quaternary ammonium salts such as "Quaternary Ammonium Salt P-51" (manufactured by Orient Chemical Industry Co., Ltd.) and "Copy Charge PX VP435" (manufactured by Hoechst Japan KK), alkoxylated amines, alkylamides, molybdic acid chelate pigments, and imidazole compounds such as "PLZ1001" (manufactured by Shikoku Chemical Industry Co., Ltd.).

[0118] Examples of negatively charged charge control agents include metal complexes such as "Bontron (registered trademark) S-22," "Bontron (registered trademark) S-34," "Bontron (registered trademark) E-81," and "Bontron (registered trademark) E-84" (all manufactured by Orient Chemical Industry Co., Ltd.) and "Spiron Black TRH" (manufactured by Hodogaya Chemical Industry Co., Ltd.), thioindigo pigments, quaternary ammonium salts such as "Copy Charge NX VP434" (manufactured by Hoechst Japan), calixarene compounds such as "Bontron (registered trademark) E-89" (manufactured by Orient Chemical Industry Co., Ltd.), boron compounds such as "LR147" (manufactured by Nippon Carlit Co., Ltd.), and fluorine compounds such as magnesium fluoride and carbon fluoride.

[0119] In addition to the above, metal complexes usable as negatively chargeable charge control agents include oxycarboxylic acid metal complexes, dicarboxylic acid metal complexes, amino acid metal complexes, diketone metal complexes, diamine metal complexes, etc. Furthermore, metal complexes having various structures such as azo group-containing benzene-benzene derivative skeleton metal complexes and azo group-containing benzene-naphthalene derivative skeleton metal complexes can be used.

[0120] By configuring the toner base particles to contain a charge control agent in this way, the chargeability of the toner is improved.

[0121] The content of the charge control agent is preferably in the range of 0.01 to 30% by mass, and more preferably in the range of 0.1 to 10% by mass, with the total mass of the toner base particles being 100% by mass.

[0122] (Mold of toner base particles) The form of the toner base particles according to the present invention is not particularly limited, and may be, for example, a so-called single-layer structure (a homogeneous structure that is not a core-shell type), a core-shell structure, a multi-layer structure of three or more layers, a domain-matrix structure, or the like.

[0123] <External additives> In order to improve the fluidity, chargeability, cleaning properties, etc. of the toner, external additives such as a fluidizing agent, a cleaning aid, etc., which are so-called post-treatment agents, may be added to the toner base particles to form the toner.

[0124] Examples of external additives include inorganic oxide particles such as silica particles, alumina particles, and titanium oxide particles, and inorganic stearic acid compound particles such as aluminum stearate particles and zinc stearate particles. Examples of external additives also include inorganic particles such as inorganic titanic acid compound particles such as strontium titanate particles and zinc titanate particles. These may be used alone or in combination of two or more.

[0125] These inorganic particles may be surface-treated with a silane coupling agent, a titanium coupling agent, a higher fatty acid, a silicone oil, or the like to improve heat-resistant storage properties and environmental stability.

[0126] The amount of the external additive added is preferably within a range of 0.05 to 5 parts by mass, and more preferably within a range of 0.1 to 3 parts by mass, with the total mass of the toner base particles being 100% by mass.

[0127] <Average particle size of toner> The average particle size of the toner is preferably in the range of 4 to 10 μm, more preferably 5 to 9 μm, in terms of volume-based median diameter (D50). When the volume-based median diameter (D50) is in the above range, transfer efficiency is increased, improving halftone image quality and the image quality of fine lines, dots, etc.

[0128] In the present invention, the volume-based median diameter (D50) of the toner is measured and calculated using the following measuring device: A "Coulter Counter 3" (manufactured by Beckman Coulter) connected to a computer system (manufactured by Beckman Coulter) equipped with data processing software "Software V3.51" is used.

[0129] Specifically, the volume-based median diameter (D50) of toner can be measured using the following method. First, 0.02 g of the measurement sample (toner) is added to 20 mL of surfactant solution (for example, a surfactant solution prepared by diluting a neutral detergent containing surfactant components 10 times with pure water to disperse the toner particles) and allowed to mix. Then, ultrasonic dispersion is performed for 1 minute to prepare a toner dispersion. This toner dispersion is then pipetted into a beaker containing an ISOTON II (manufactured by Beckman Coulter) in the sample stand until the concentration indicated on the measuring device reaches 8%.

[0130] By setting the concentration within this range, reproducible measurement values ​​can be obtained. The measurement device counts 25,000 particles and sets the aperture diameter to 50 μm. The measurement range of 1 to 30 μm is divided into 256 parts to calculate the frequency value. The particle diameter of the largest 50% of the volume fraction is taken as the volume-based median diameter (D50).

[0131] [Toner manufacturing method] Next, an embodiment of the method for producing a toner for developing electrostatic images of the present invention will be described. However, the method for producing a toner for developing electrostatic images is not limited to the following embodiment. The method for producing a toner for developing electrostatic images includes a step A of copolymerizing a polymerizable monomer represented by the following general formula (3) and a polymerizable monomer represented by the following general formula (4) to obtain a polymer, and a step B of forming toner base particles containing the obtained polymer. The polymer obtained in step A is the specific polymer described above, i.e., a polymer having a first structural unit represented by general formula (1) and a second structural unit represented by general formula (2). Step B is a step of forming toner base particles containing the specific polymer obtained in step A. For example, in step B, toner base particles may be formed containing the polymer obtained in step A, a colorant, and a crystalline additive.

[0132] [ka]

[0133] In general formula (3), R1 is a hydrogen atom or a methyl group, and R2 is an alicyclic substituent having 6 to 12 carbon atoms. R1 and R2 in general formula (3) are synonymous with R1 and R2 in general formula (1) above.

[0134] [ka]

[0135] In the general formula (4), R3 represents a hydrogen atom or a methyl group, and R4 represents a methyl group or an ethyl group. R3 and R4 in the general formula (4) have the same meanings as R3 and R4 in the general formula (2).

[0136] Step A may include a step of obtaining a polymer dispersion. For example, it may include a step of preparing a particle dispersion of a specific polymer by polymerizing the monomers represented by the general formula (3) and the general formula (4) as polymerization materials in an aqueous medium by emulsion polymerization, mini-emulsion polymerization, or the like. Then, step B may include a step of mixing the polymer dispersions obtained in step A.

[0137] There are no particular limitations on the polymerization method in step A or the method for forming toner base particles in step B, and methods based on conventionally known toner manufacturing methods can be used. For example, the polymerization method in step A is preferably a method utilizing emulsion aggregation, from the viewpoints that particle size and shape can be easily controlled and energy costs during production can be reduced. As the emulsion aggregation method, methods described in JP-A-5-265252, JP-A-6-329947, JP-A-9-15904, etc. can be used.

[0138] The production method using the emulsion aggregation method will be described in detail below.

[0139] The production method using the emulsion aggregation method can be carried out by the following steps (1A) to (1D). (1A) Binder resin particle dispersion liquid preparation step of preparing a binder resin particle dispersion liquid (1B) Colorant particle dispersion liquid preparation step of preparing a colorant particle dispersion liquid (1C) A crystalline additive dispersion preparation step for preparing a crystalline additive dispersion (1D) A release agent particle dispersion liquid preparation step for preparing a release agent particle dispersion liquid (2) An association process in which a flocculant is added to an aqueous medium containing binder resin particles, colorant particles, crystalline additives, and release agent particles, and salting out is promoted while simultaneously flocculation and fusion are carried out to form associated particles. (3) A ripening process to form toner particles by controlling the shape of aggregated particles (4) A filtering and washing process for filtering toner particles from the aqueous medium and removing surfactants and the like from the toner particles. (5) Drying process to dry the washed toner particles (6) Adding external additives to the dried toner particles

[0140] The steps (1A) to (1D) will be explained below.

[0141] (1A) Binder resin particle dispersion preparation step In this process, resin particles are formed by conventional emulsion polymerization or the like, and then these resin particles are aggregated and fused to form binder resin particles. As an example, a binder resin particle dispersion is prepared by adding and dispersing the monomers that serve as the polymerization materials for the binder resin in an aqueous medium and polymerizing them with a water-soluble radical polymerization initiator. For example, in the case of the specific polymers described above, a first monomer, a second monomer, and, if necessary, a third monomer are used as the monomers that serve as the polymerization materials.

[0142] Each of the monomers may be a commercially available product or a synthetic product.

[0143] As the water-soluble radical polymerization initiator, persulfates such as potassium persulfate and ammonium persulfate, azobisaminodipropane acetate, azobiscyanovaleric acid and its salts, hydrogen peroxide, etc. can be used.

[0144] As a method for preparing a binder resin particle dispersion, in addition to the above-mentioned emulsion polymerization, a binder resin particle dispersion can also be obtained by a method in which a binder resin obtained by radical polymerization or the like is subjected to a dispersion treatment in an aqueous medium without using an organic solvent. Alternatively, a binder resin particle dispersion can be obtained by a method in which a binder resin obtained by radical polymerization or the like is dissolved in an organic solvent such as ethyl acetate to form a solution, the solution is emulsified and dispersed in an aqueous medium using a disperser, and then a solvent removal treatment is performed.

[0145] Even when the binder resin particle dispersion is prepared by a method other than emulsion polymerization, the method for polymerizing the binder resin is preferably radical polymerization from the viewpoint of easy synthesis.

[0146] In addition to the water-soluble radical polymerization initiators described above, the radical polymerization initiator used in the radical polymerization may also be an oil-soluble radical polymerization initiator. Specific examples of the oil-soluble radical polymerization initiator include azo-based or diazo-based polymerization initiators and peroxide-based polymerization initiators.

[0147] Examples of the azo or diazo polymerization initiator include 2,2'-azobis-(2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, and azobisisobutyronitrile.

[0148] Examples of peroxide polymerization initiators include benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, cumene hydroperoxide, t-butyl hydroperoxide, di-t-butyl peroxide, dicumyl peroxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide, 2,2-bis-(4,4-t-butylperoxycyclohexyl)propane, and tris-(t-butylperoxy)triazine.

[0149] For the radical polymerization, a known chain transfer agent such as n-octyl mercaptan or n-octyl-3-mercaptopropionate may be used as needed.

[0150] For dispersion purposes, it is also preferable to carry out the polymerization in the presence of a known surfactant (for example, anionic surfactants such as polyoxyethylene (2) dodecyl ether sodium sulfate, sodium dodecyl sulfate, and sodium dodecylbenzenesulfonate).

[0151] The polymerization temperature varies depending on the types of monomers and polymerization initiators used, but is preferably within a range of 50 to 100° C., and more preferably within a range of 55 to 90° C. The polymerization time also varies depending on the types of monomers and polymerization initiators used, but is preferably, for example, 1 to 12 hours.

[0152] In the binder resin particle dispersion preparation step, a release agent may be added to the binder resin particle dispersion in advance, if necessary.

[0153] The volume-based median diameter (D50) of the binder resin particles in the dispersion is preferably within a range of 50 to 300 nm. The volume-based median diameter (D50) of the binder resin particles in the dispersion can be measured by dynamic light scattering using a "Microtrac UPA-150" (manufactured by Nikkiso Co., Ltd.).

[0154] (1B) Colorant particle dispersion preparation process This colorant particle dispersion preparation step is a step of dispersing a colorant in the form of fine particles in an aqueous medium to prepare a colorant particle dispersion.

[0155] The colorant can be dispersed using mechanical energy. The volume-based median diameter (D50) of the colorant particles in the dispersion is preferably within a range of 10 to 300 nm, and more preferably within a range of 50 to 200 nm.

[0156] The volume-based median diameter (D50) of the colorant particles in the dispersion can be measured by dynamic light scattering using a "Microtrac UPA-150" (manufactured by Nikkiso Co., Ltd.) in the same manner as above.

[0157] (1C) Crystalline additive dispersion preparation step This crystalline additive dispersion preparation step is a step of dispersing the crystalline additive in the form of fine particles in an aqueous medium to prepare a dispersion of the crystalline additive.

[0158] The crystalline additive can be dispersed using mechanical energy. The volume-based median diameter (D50) of the crystalline additive in the dispersion is preferably within a range of 100 to 1000 nm, and more preferably within a range of 200 to 700 nm.

[0159] The volume-based median diameter (D50) of the crystalline additive in the dispersion can be measured, for example, by a laser diffraction particle size distribution analyzer "LA-750" (manufactured by Horiba, Ltd.).

[0160] (1D) Release agent particle dispersion liquid preparation process The release agent particle dispersion preparation step is a step of dispersing the release agent in the form of fine particles in an aqueous medium to prepare a dispersion of the release agent particles.

[0161] The release agent can be dispersed by utilizing mechanical energy. The volume-based median diameter (D50) of the release agent particles in the dispersion is preferably within a range of 100 to 1000 nm, and more preferably within a range of 200 to 700 nm.

[0162] The volume-based median diameter (D50) of the release agent particles in the dispersion can be measured, for example, by a laser diffraction particle size distribution analyzer "LA-750" (manufactured by Horiba, Ltd.).

[0163] (aqueous medium) The aqueous medium used in steps (1A) to (1D) may be water, or an aqueous medium containing water as the main component (50% by mass or more) and optionally containing water-soluble solvents such as alcohols and glycols, surfactants, dispersants, etc. The aqueous medium used is preferably a mixture of water and surfactants.

[0164] Examples of the water-soluble solvent include methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone, tetrahydrofuran, etc. Among these, alcohols such as methanol, ethanol, isopropanol, and butanol, which are organic solvents that do not dissolve the polymer, are preferred.

[0165] Examples of surfactants include cationic surfactants, anionic surfactants, and nonionic surfactants. Examples of cationic surfactants include dodecyl ammonium chloride, dodecyl ammonium bromide, dodecyl trimethyl ammonium bromide, dodecyl pyridinium chloride, dodecyl pyridinium bromide, and hexadecyl trimethyl ammonium bromide. Examples of anionic surfactants include fatty acid soaps such as sodium stearate and sodium dodecanoate, sodium dodecyl benzene sulfonate, and sodium dodecyl sulfate. Examples of nonionic surfactants include polyoxyethylene dodecyl ether, polyoxyethylene hexadecyl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene lauryl ether, polyoxyethylene sorbitan monooleate ether, and monodecanoyl sucrose.

[0166] These surfactants can be used alone or in combination of two or more. Among the surfactants, anionic surfactants are preferred, and sodium dodecylbenzenesulfonate and sodium dodecyl sulfate are more preferred.

[0167] The amount of surfactant added is preferably within a range of 0.01 to 10 parts by mass, and more preferably within a range of 0.04 to 2 parts by mass, relative to 100 parts by mass of the aqueous medium.

[0168] The steps from (2) association step to (6) external additive addition step can be carried out according to various conventionally known methods.

[0169] The flocculant used in the association step (2) is not particularly limited, but is preferably selected from metal salts.

[0170] Examples of metal salts include monovalent metal salts such as salts of alkali metals such as sodium, potassium, and lithium; divalent metal salts such as calcium, magnesium, manganese, and copper; and trivalent metal salts such as iron and aluminum.

[0171] Specific examples of metal salts include sodium chloride, potassium chloride, lithium chloride, calcium chloride, magnesium chloride, zinc chloride, copper sulfate, magnesium sulfate, manganese sulfate, and polyaluminum chloride. Among these, it is particularly preferable to use divalent or trivalent metal salts, since they can promote aggregation with smaller amounts. These can be used alone or in combination of two or more.

[0172] [Developer] The toner may be used, for example, as a one-component magnetic toner containing a magnetic material, as a two-component developer mixed with so-called carrier particles, or as a non-magnetic toner alone, and any of these may be suitably used.

[0173] As the magnetic material, for example, magnetite, γ-hematite, or various ferrites can be used.

[0174] As the carrier particles constituting the two-component developer, magnetic particles made of conventionally known materials such as metals such as iron, steel, nickel, cobalt, ferrite, and magnetite, and alloys of these metals with metals such as aluminum and lead can be used.

[0175] As the carrier particles, it is preferable to use coated carrier particles in which the surfaces of magnetic particles are coated with a coating agent such as resin, or so-called resin-dispersed carrier particles in which magnetic powder is dispersed in a binder resin.

[0176] The resin for coating is not particularly limited, but examples thereof include olefin resin, styrene resin, styrene-acrylic resin, silicone resin, polyester resin, and fluororesin.

[0177] Furthermore, the resin for constituting the resin-dispersed carrier particles is not particularly limited and any known resin can be used, such as acrylic resin, styrene-acrylic resin, polyester resin, fluororesin, and phenolic resin.

[0178] The volume-based median diameter (D50) of the carrier particles is preferably within a range of 20 to 100 μm, and more preferably within a range of 25 to 60 μm.

[0179] The volume-based median diameter (D50) of the carrier particles can be measured typically by a laser diffraction particle size distribution measuring device "HELOS" (manufactured by SYMPATEC) equipped with a wet disperser.

[0180] The amount of toner particles mixed with carrier particles is preferably within the range of 2 to 10% by mass, with the total mass of toner particles and carrier particles being 100% by mass.

[0181] [Image forming method] Next, an embodiment of the image forming method of the present invention will be described. As shown in Fig. 1, the image forming method of this embodiment includes a step S01 of adhering the electrostatic image developing toner of this embodiment described above to a recording medium, and a step S02 of fixing the electrostatic image developing toner adhered to the recording medium to the recording medium. Fig. 1 is a flowchart showing an example of the image forming method.

[0182] The toner for developing electrostatic images can be suitably used in an image forming method including a fixing step S02 using a heat and pressure fixing method in which heat and pressure are applied simultaneously. In particular, the toner can be suitably used in an image forming method in which fixing is performed at a relatively low fixing temperature in the fixing step, such that the surface temperature of the heating member in the fixing nip is within a range of 80 to 110°C, preferably 80 to 95°C.

[0183] Furthermore, it can also be suitably used in an image forming method with high-speed fixing in which the fixing linear speed is within the range of 200 to 600 mm / sec.

[0184] Specifically, in the image forming method of this embodiment, for example, an electrostatic image formed on a photoreceptor is developed using the toner described above to obtain a toner image, and this toner image is then transferred to an image support. Thereafter, the toner image transferred to the image support is fixed to the image support by a heat and pressure fixing process, thereby obtaining a printed matter on which a visible image is formed.

[0185] The toner of the present invention can be used in a monochrome image forming method and a full-color image forming method.

[0186] The full-color image forming method can be applied to any image forming method, such as a four-cycle image forming method or a tandem image forming method. The four-cycle image forming method is an image forming method that uses four types of color developing devices for yellow, magenta, cyan, and black, and one photoconductor. The tandem image forming method is an image forming method that uses image forming units each having a color developing device and photoconductor for each color, one for each color.

[0187] [Image forming device] Next, an embodiment of an image forming apparatus of the present invention will be described. The image forming apparatus of this embodiment includes an attachment unit that attaches the electrostatic image developing toner of this embodiment described above to a recording medium, and a fixing unit that fixes the electrostatic image developing toner attached to the recording medium to the recording medium. Examples of such an image forming apparatus include an image forming unit that forms a toner image on a transfer material using the electrostatic image developing toner, a fixing member that faces the upper surface of the transfer material, and a pressure member that faces the fixing member to form a fixing nip. Furthermore, such an image forming apparatus may further include a drive source that drives each of the fixing member and the pressure member, and a drive control unit that controls the surface speed of each of the fixing member and the pressure member.

[0188] As an example of an image forming apparatus, an example of the schematic configuration of a color tandem type image forming apparatus 100 equipped with a fixing member and a pressure member will be described with reference to Fig. 2. Fig. 2 is a schematic cross-sectional view showing an example of the internal configuration of the image forming apparatus main body. This image forming apparatus is a multifunction machine equipped with functions such as a scanner, copier, and printer, and is called an MFP (Multi Function Peripheral or Multi Function Printer).

[0189] As shown in FIG. 2, the image forming apparatus 100 is provided with an annular intermediate transfer belt 108 wound around two rollers 102 and 106 and moving in the circumferential direction, located approximately in the center of a main body casing 101.

[0190] Of the two rollers 102 and 106, the roller 102 is located on the left side in Fig. 2, and the other roller 106 is located on the right side in Fig. 2. The intermediate transfer belt 108 is supported by these rollers 102 and 106 and is driven to rotate in the direction of arrow X.

[0191] Below the intermediate transfer belt 108, image forming segments 110Y, 110M, 110C, and 110K corresponding to the toner colors yellow (Y), magenta (M), cyan (C), and black (K) are arranged in order from the left in FIG. 2.

[0192] The image forming segments 110Y, 110M, 110C, and 110K are configured similarly to one another except for the toner colors they handle.

[0193] For example, the yellow image forming segment 110Y is configured by integrating a photosensitive drum 190, a charging device 191, an exposure device 192, a developing device 193 that develops using toner, and a cleaner device 195.

[0194] A primary transfer roller 194 is provided at a position facing the photosensitive drum 190 across the intermediate transfer belt 108 .

[0195] During image formation, first, the surface of the photosensitive drum 190 is uniformly charged by the charging device 191, and then the surface of the photosensitive drum 190 is exposed by the exposure device 192, and a latent image is formed thereon. Next, the latent image on the surface of the photosensitive drum 190 is developed into a toner image by the developing device 193. This toner image is transferred to the intermediate transfer belt 108 by applying a voltage between the photosensitive drum 190 and a primary transfer roller 194. Residual toner on the surface of the photosensitive drum 190 after transfer is cleaned by the cleaning device 195.

[0196] As the intermediate transfer belt 108 moves in the direction of arrow X, four color toner images are formed on the intermediate transfer belt 108 as an output image by the image forming segments 110Y, 110M, 110C, and 110K in a superimposed manner.

[0197] On the left side of the intermediate transfer belt 108, a cleaning device 125 that removes residual toner from the surface of the intermediate transfer belt 108 and a toner recovery box 126 that recovers the toner removed by the cleaning device 125 are provided.

[0198] A secondary transfer roller 112 is provided on the right side of the intermediate transfer belt 108, with a transport path 124 for the transfer material sandwiched therebetween. A transport roller 120 is provided in the transport path 124 at a position corresponding to the upstream side of the secondary transfer roller 112. An optical density sensor 115 is provided to detect the toner pattern on the intermediate transfer belt 108.

[0199] A fixing device 130 for fixing the toner onto the transfer material is provided in the upper right portion of the main body casing 101 .

[0200] The fixing device 130 includes a pair of fixing members, a fixing roller and a pressure roller, which are extending perpendicular to the paper surface in Fig. 2. In Fig. 2, the fixing roller includes a heating roller 132 and the other is a pressure roller 131.

[0201] The heating roller 132 and the pressure roller 131 each have a drive unit (not shown) and a drive control unit (control unit 200 in FIG. 2) that controls the surface speed of the heating roller 132 and the pressure roller 131 that are driven to rotate.

[0202] Heating roller 132 is heated to a predetermined target temperature (for example, a fixing temperature in the range of 180 to 200°C) by heater 133. Pressure roller 131 is urged toward heating roller 132 by a spring (not shown). This causes pressure roller 131 and heating roller 132 to form a nip portion for fixing.

[0203] When the transfer material 90 onto which the toner image has been transferred passes through this nip, the toner image is fixed onto the transfer material 90. The temperatures of the pressure roller 131 and the heating roller 132 are detected by temperature sensors 135 and 136, respectively.

[0204] Two sheet feed cassettes 116A and 116B for storing transfer materials 90 are provided in the lower part of the main body casing 101. In Fig. 2, the transfer material 90 is stored only in the sheet feed cassette 116A.

[0205] Each of the paper feed cassettes 116A and 116B is provided with a paper feed roller 118 for feeding out the transfer material, and a paper feed sensor 117 for detecting the fed out transfer material.

[0206] A control unit 200 consisting of a CPU (Central Processing Unit) that controls the operation of the entire image forming apparatus is provided inside the main body casing 101. The control unit 200 also has a function of controlling the rotational drive of the drive source, and changes the difference between the surface speed of the fixing member and the surface speed of the pressure member when an image is clamped between the fixing member and the pressure member by inputting conditions in advance.

[0207] During image formation, under the control of the control unit 200, the transfer material 90 is sent out one by one by the paper feed roller 118 from the paper feed cassette 116A to the conveying path 124. The transfer material 90 sent out to the conveying path 124 is fed by the conveying roller 120 to the toner transfer position between the intermediate transfer belt 108 and the secondary transfer roller 112, with timing determined by the resist sensor 114.

[0208] Meanwhile, as described above, four-color toner images are formed on the intermediate transfer belt 108 by the image forming segments 110Y, 110M, 110C, and 110K in a superimposed manner. As a result, the four-color toner images on the intermediate transfer belt 108 are transferred by the secondary transfer roller 112 onto the transfer material 90 sent to the toner transfer position.

[0209] The transfer material 90 onto which the toner image has been transferred is conveyed through a nip portion formed by a pressure roller 131 and a heating roller 132 of a fixing device 130, and is subjected to heat and pressure. As a result, the toner image is fixed onto the transfer material 90 .

[0210] Finally, the transfer material 90 on which the toner image has been fixed is discharged by a discharge roller 121 through a discharge path 127 onto a discharge tray portion 122 provided on the top surface of the main body casing 101 .

[0211] In the image forming apparatus 100, a switchback conveying path 128 is provided for feeding the transfer material 90 again to the toner transfer position in the case of double-sided printing.

[0212] As described above, the pressure roller 131 constitutes one of the fixing rollers, and here a roller made of silicone rubber is used.

[0213] The embodiments to which the present invention can be applied are not limited to the above-described embodiments, and can be modified as appropriate without departing from the spirit of the present invention.

[0214] In the above description, a heating roller is used as the fixing member and a pressure roller is used as the pressure member, but a conventionally known fixing belt system can also be manufactured and used in the same manner. The fixing belt referred to in this specification is a fixing belt made of silicone rubber that is used in an image forming apparatus when fixing toner to a transfer material.

[0215] Specifically, it refers to known fixing belts used in fixing devices, such as those described in JP-A-2017-194550, JP-A-2017-173445, and JP-A-2017-97187. [Example]

[0216] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In the following examples, unless otherwise specified, operations were carried out at room temperature (25°C). Furthermore, unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass," respectively.

[0217] [Production of Toner 1 (Example 1)] <Preparation of Binder Resin Particle Dispersion 1> First, a surfactant solution prepared by dissolving 8 g of sodium dodecyl sulfate in 3 L of ion-exchanged water was placed in a 5 L stainless steel pot (SUS pot) equipped with a stirrer, a temperature sensor, a cooling tube, and a nitrogen introducing device. After that, the liquid temperature was raised to 80°C while stirring at a stirring speed of 230 rpm under a nitrogen stream.

[0218] Next, an initiator solution prepared by dissolving 10 g of potassium persulfate in 200 g of ion-exchanged water was added to the surfactant solution, and the temperature was raised to 80° C. Thereafter, the following monomer mixture was added dropwise over 100 minutes.

[0219] -Monomer mixture- First monomer M: Isobornyl acrylate (IBXA) 160g Second monomer M: methyl methacrylate (MMA) 408g ·Third monomer M: butyl acrylate (BA) 184g ·Methacrylic acid (MAA) 48g n-Octyl-3-mercaptopropionate 5.5g

[0220] The system to which the monomer mixture liquid was added dropwise was heated and stirred at 80° C. for 2 hours to carry out polymerization, thereby preparing binder resin particle dispersion liquid 1.

[0221] The volume-based median diameter (D50) of the binder resin particles in the obtained binder resin particle dispersion 1 was measured by dynamic light scattering using "Microtrac UPA-150" (manufactured by Nikkiso Co., Ltd.) and was found to be 115 nm.

[0222] The peak molecular weight of the polymer contained in the binder resin was measured as follows and was found to be 21,100.

[0223] First, a measurement sample was added to tetrahydrofuran (THF) to a concentration of 1 mg / mL. The mixture was dispersed for 5 minutes using an ultrasonic disperser at room temperature (25°C), and then filtered through a 0.2 μm pore membrane filter to prepare a sample solution. A GPC system "HLC-8220" (Tosoh Corporation) and a column "TSKguard column + TSKgel Super HZM-M triple column" (Tosoh Corporation) were used, with tetrahydrofuran as the carrier solvent at a flow rate of 0.2 mL / min. The column temperature was maintained at 40°C. 10 μL of the prepared sample solution was injected into the GPC system together with the carrier solvent, and the molecular weight distribution of the measurement sample was detected using a refractive index detector (RI detector). The peak molecular weight was determined from the detected molecular weight distribution.

[0224] <Preparation of Colorant Particle Dispersion 1> Colorant: Carbon black 10 parts by weight 20% anionic surfactant 1.5 parts by weight Ion-exchanged water 90 parts by weight

[0225] Carbon black (Mogul (registered trademark) L manufactured by Cabot Corporation) was used as the colorant. Furthermore, a 20% aqueous solution of sodium dodecylbenzenesulfonate was used as the 20% anionic surfactant.

[0226] The above components were mixed and dispersed in an SC mill to obtain colorant particle dispersion 1. The volume-based median diameter (D50) of the colorant particles in the dispersion was measured by dynamic light scattering using a Microtrac UPA-150 (manufactured by Nikkiso Co., Ltd.) and was found to be 155 nm.

[0227] <Preparation of Release Agent Particle Dispersion 1> Behenyl behenate 100 parts by mass Sodium dodecyl sulfate 5 parts by mass Ion-exchanged water 240 parts by weight

[0228] The above components were dispersed in a round stainless steel flask for 10 minutes using a homogenizer "Ultra Turrax (registered trademark) T50" (manufactured by IKA), and then dispersed using a pressure discharge homogenizer to obtain a release agent particle dispersion 1. The volume-based median diameter (D50) of the release agent particles in the dispersion was measured using a laser diffraction particle size distribution analyzer LA-750 (manufactured by Horiba, Ltd.) and was found to be 530 nm.

[0229] <Preparation of Crystalline Additive Dispersion 1> Stearamide stearate 100 parts by mass Sodium dodecyl sulfate 5 parts by mass Ion-exchanged water 240 parts by weight

[0230] The above components were dispersed in a round stainless steel flask using a homogenizer "Ultra Turrax (registered trademark) T50" (manufactured by IKA) for 10 minutes, and then dispersed using a pressure discharge homogenizer to obtain crystalline additive dispersion 1. The volume-based median diameter (D50) of the crystalline additive particles in the dispersion was measured using a laser diffraction particle size distribution analyzer LA-750 (manufactured by Horiba, Ltd.) and was found to be 400 nm.

[0231] <Preparation of Crystalline Polyester Resin Particle Dispersion 1> (Synthesis of crystalline polyester resin 1) 281 parts by weight of dodecanedioic acid and 107 parts by weight of 1,4-butanediol were placed in a reaction vessel equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet tube. After purging the reaction vessel with dry nitrogen gas, 0.1 parts by weight of Ti(On-Bu)4 was added, and the resulting mixture was stirred at approximately 180°C for 8 hours under a nitrogen gas flow to carry out the reaction. Further, 0.2 parts by weight of Ti(On-Bu)4 was added to the mixture, and the temperature of the mixture was raised to approximately 220°C. The mixture was stirred for 6 hours, and the reaction was continued until the acid value reached 20 mgKOH / g. The pressure inside the reaction vessel was then reduced to 1333.2 Pa, and the reaction was continued under reduced pressure to obtain crystalline polyester resin 1. Crystalline polyester resin 1 had an acid value of 20 mgKOH / g, a number average molecular weight (Mn) of 5,500, a weight average molecular weight (Mw) of 18,000, and a melting point (Tm) of 72°C.

[0232] 30 parts by mass of the crystalline polyester resin 1 obtained by the synthesis above was melted and transferred to an emulsifier / disperser "Cavitron CD1010" (manufactured by Eurotech) at a transfer rate of 100 parts by mass per minute. Simultaneously, 120 parts by mass of dilute aqueous ammonia with a concentration of 0.37% by mass was heated to 100°C using a heat exchanger and transferred to the emulsifier / disperser at a transfer rate of 0.1 liters per minute. The dilute aqueous ammonia was prepared by diluting 70 parts by mass of reagent aqueous ammonia with ion-exchanged water in an aqueous solvent tank.

[0233] The emulsifying and dispersing machine was operated at a rotor speed of 60 Hz and a pressure of 5 kg / cm. 2 (490 kPa) to prepare a crystalline polyester resin particle dispersion 1 having a solid content of 30 parts by mass (solid content concentration: 20% by mass). The volume-based median diameter (D50) of the crystalline polyester resin particles in dispersion 1 was measured using a Microtrac particle size distribution analyzer "UPA-150" (manufactured by Nikkiso Co., Ltd.) and found to be 200 nm.

[0234] <Preparation of Toner Base Particle Dispersion 1> Binder resin particle dispersion liquid 1 237 parts by mass Colorant particle dispersion 1 42 parts by weight Release agent particle dispersion 1 18 parts by weight Crystalline additive dispersion 1 71 parts by mass Polyaluminum chloride 1.8 parts by mass Ion-exchanged water 600 parts by weight

[0235] The above components were mixed and dispersed in a round stainless steel flask using a homogenizer "Ultra-Turrax (registered trademark) T50" (manufactured by IKA), and then the temperature in the flask was raised to 55°C while stirring in a heating oil bath. After the mixed liquid was heated to 55°C in this way, 60 parts by mass of crystalline polyester resin particle dispersion 1 (solid content equivalent) was added to this mixed liquid over 10 minutes to promote particle aggregation.

[0236] After that, the solution was kept at 55°C for 30 minutes, and it was confirmed that aggregated particles with a volume-based median diameter (D50) of 4.8 µm were formed in the solution.

[0237] Furthermore, when the temperature of the heating oil bath was increased to 56°C and held for 2 hours, the volumetric The median diameter (D50) was 5.9 μm.

[0238] Thereafter, 1 mol / L of sodium hydroxide was added to the system to adjust the pH of the system to 5.0 at 56°C, and the round stainless steel flask was then sealed using a magnetic seal and heated to 98°C with continued stirring. Stirring was continued for 6 hours to complete fusion (coagulation) between the binder resin particles, thereby preparing toner base particle dispersion 1. The volume-based median diameter (D50) of the toner base particles in the dispersion was 6.1 μm.

[0239] <Cleaning and drying process> The toner base particle dispersion 1 was subjected to solid-liquid separation using a basket-type centrifuge "MARKIII Model No. 60x40" (manufactured by Matsumoto Kikai Hanbai Co., Ltd.) to form a wet cake of toner base particles.

[0240] The wet cake obtained as described above was washed with ion-exchanged water at 45°C using the basket centrifuge until the electrical conductivity of the filtrate reached 5 μS / cm, and then transferred to a "Flash Jet Dryer" (manufactured by Seishin Enterprise Co., Ltd.) and dried until the moisture content reached 0.5% by mass, yielding toner base particles.

[0241] <External additive treatment of toner base particles> Toner 1 was produced by adding 1 part by mass of hydrophobic silica and 0.3 parts by mass of hydrophobic titania to 100 parts by mass of the toner base particles obtained above and mixing them in a Henschel mixer (registered trademark) to carry out an external additive treatment. The hydrophobic silica used had a number average primary particle diameter of 12 nm. The hydrophobic titania used had a number average primary particle diameter of 20 nm.

[0242] [Production of Toners 2 to 35 (Examples 2 to 35)] <Preparation of Binder Resin Particle Dispersions 2 to 35> Binder resin particle dispersions 2 to 32 were prepared in the same manner as binder resin particle dispersion 1, except that the combinations and addition amounts [mass %] of the first monomer M, the second monomer M, and the third monomer M were changed as shown in Tables 1 to 3 below. In Tables 1 to 3, each monomer is shown by an abbreviation, and the compound names corresponding to each abbreviation are as follows: IBXA: Isobornyl acrylate IBXMA: Isobornyl methacrylate CHA: Cyclohexyl acrylate CHMA: Cyclohexyl methacrylate ADMA: Adamantyl acrylate ADMMA: Adamantyl methacrylate MA: methyl acrylate MMA: methyl methacrylate EA: Ethyl acrylate EMA: Ethyl methacrylate AA: acrylic acid MAA: methacrylic acid BA: n-butyl acrylate

[0243] <Production of Toners 2 to 32 (Examples 2 to 32)> Toners 2 to 32 were prepared in the same manner as Toner 1, except that binder resin particle dispersions 2 to 32 prepared as described above were used, and the types and amounts [mass %] of the crystalline additives were set as shown in Tables 4 to 6 below. In the preparation of Toners 7 and 21, a fatty acid ester (behenyl stearate) was used as the crystalline additive, as shown in Tables 4 and 5. In the preparation of Toners 8 and 22, a fatty acid diester (ethylene glycol stearate) was used as the crystalline additive, as shown in Tables 4 and 5. In the preparation of Toners 9 and 23, a fatty acid diester (ethylene glycol behenate) was used as the crystalline additive, as shown in Tables 4 and 5. In the preparation of Toners 10 and 24, a fatty acid amide (stearamide) was used as the crystalline additive, as shown in Tables 4 and 5.

[0244] <Production of Toner 33 (Example 33)> Toner 33 was prepared in the same manner as Toner 1, except that binder resin particle dispersion 33 prepared as described above was used, the type and amount [mass %] of the crystalline additive were as shown in Table 6 below, and crystalline polyester resin particle dispersion 1 was not added. In Tables 4 to 6, the column "CPEs" under "Other Resins" indicates whether crystalline polyester resin particle dispersion 1 was added or not. If crystalline polyester resin particle dispersion 1 was added, "Yes" is entered, and if crystalline polyester resin particle dispersion 1 was not added, "No" is entered.

[0245] <Production of Toner 34 (Example 34)> Toner 34 was prepared in the same manner as Toner 1, except that binder resin particle dispersion 34 prepared as described above was used and myricyl lignocerate was used as the crystalline additive, and the amount added [mass %] was changed as shown in Table 6 below. Myricyl lignocerate has a linear alkyl group having 24 or more carbon atoms as a fatty acid structure.

[0246] <Production of Toner 35 (Example 35)> Toner 35 was prepared in the same manner as Toner 1, except that binder resin particle dispersion 35 prepared as described above was used and stearyl palmitate was used as the crystalline additive, and the amount added [mass %] was changed as shown in Table 6 below. Stearyl palmitate has a linear alkyl group having 16 or less carbon atoms as a fatty acid structure.

[0247] [Production of Toners 36 to 39 (Comparative Examples 1 to 4)] <Preparation of Binder Resin Particle Dispersions 36 to 39> Binder resin particle dispersions 36 to 39 were prepared in the same manner as for the binder resin particle dispersion 1, except that the combinations and addition amounts [mass %] of the first monomer M, the second monomer M, and the third monomer M were changed as shown in Table 3 below.

[0248] <Production of Toner 36 (Comparative Example 1)> Using the binder resin particle dispersion 36 prepared as described above, toner 36 was prepared in the same manner as toner 1, except that no crystalline additive was used, as shown in Table 6 below.

[0249] <Production of Toners 37 and 38 (Comparative Examples 2 and 3)> Using the binder resin particle dispersions 37 and 38 prepared as described above, toners 37 and 38 were prepared in the same manner as toner 1, as shown in Table 6 below.

[0250] <Production of Toner 39 (Comparative Example 4)> Toner 39 was prepared in the same manner as Toner 1, except that the binder resin particle dispersion 39 prepared as described above was used, n-docosane (a linear alkane having 22 carbon atoms) was used as an additive, and the amount added [mass %] was changed as shown in Table 6 below.

[0251] The low-temperature fixability and tackiness of the thus prepared toners 1 to 39 of Examples 1 to 35 and Comparative Examples 1 to 4 were evaluated by the following methods. The results are shown in Tables 4 to 6.

[0252] [evaluation] (1) Low-temperature fixability Using the image forming device described below, an A4 size Mondi Color Copy (basis weight 90 g / m) manufactured by Mondi was printed under an environment of normal temperature and normal humidity (temperature 20°C, humidity 50% RH). 2 ) on an unfixed solid image (toner adhesion amount 11.3 g / m 2 As the image forming apparatus, a commercially available full-color multifunction printer "bizhub PRESS C1070" (manufactured by Konica Minolta, Inc.) was used.

[0253] Next, the surface temperature of the pressure roller of the fixing device was set to 100°C, and the surface temperature of the heating roller was changed in 2°C increments within the range of 100 to 150°C, and fixing was performed. The lowest fixing temperature at which image contamination due to fixing offset was not visually confirmed was defined as the minimum fixing temperature. If the minimum fixing temperature is less than 135°C, the toner is excellent in low-temperature fixing ability (A), and if it is 135°C or higher but less than 140°C, it is at a practically problematic level (B). Toners at 140°C or higher are not sufficiently fixed at the target paper feed speed, and are at a practically problematic level (C).

[0254] (2) Tacking ability Using the following image forming device, a 24 lb (90 g / m) A4 HAMMERMILL Laser Print (based on a basis weight of 90 g / m) manufactured by HAMMERMILL was printed in an environment of normal temperature and humidity (temperature 20°C, humidity 50% RH). 2 ), the image shown in Figure 3 (toner adhesion amount 10.0 g / m 2 ) was formed. As the image forming apparatus, a commercially available full-color multifunction printer "bizhub PRESS C1070" (manufactured by Konica Minolta, Inc.) was used. Figures 3 to 5 are diagrams for explaining the method for evaluating tacking in the examples.

[0255] Next, the surface temperature of the pressure roller of the fixing device was set to 100°C, and the surface temperature of the heating roller was set to the temperature at which image contamination due to fixing offset was no longer visually confirmed in the low-temperature fixing test + 25°C, and fixing was performed on two sheets.

[0256] Next, a weight (201), an aluminum plate (202), paper inserts (203), and a thermocouple (204) were set as shown in Figure 4. The paper inserts (203) were five sheets of A4 HAMMERMILL Laser Print 24 lb, stacked together, with the edges secured with tape (205). The thermocouple (204) was inserted between the third and fourth sheets from the top of the paper inserts (203).

[0257] The clamping tool was placed in an Advantec oven "DRM420DD" and heated. After preheating for two hours at a temperature higher than the target temperature, the temperature was adjusted to the set temperature. Once the set temperature was confirmed to be stable, the oven was opened, and the two fixed images (206), (206) were placed one on top of the other so that the image areas overlapped, as shown in Figure 5. The clamping tool was then placed between the sheets, and the oven was closed and left to stand. Once the temperature inside the oven was confirmed to have stabilized at the set temperature again, the sheets were left to stand for five minutes. The overlapping fixed images (206), (206) were then removed, and the degree of adhesion between the images was evaluated using the following criteria. A rating indicates the best tack resistance, with B, C, and D indicating the worst tack resistance. A, B, and C were considered acceptable. (Evaluation criteria) A: It can be easily peeled off by hand (no peeling noise). B: It takes some force, but it can be peeled off (no peeling noise). C: It can be peeled off, but there is a peeling sound. D: The toner image surface is rough after peeling.

[0258] [Table 1]

[0259] [Table 2]

[0260] [Table 3]

[0261] [Table 4]

[0262] [Table 5]

[0263] [Table 6]

[0264] (result) Toners 1 to 35 of Examples 1 to 35 showed good results in both low-temperature fixability and tackiness. In particular, by using, as the crystalline additive, a fatty acid amide, a fatty acid diester, or a fatty acid monoester having a linear alkyl group with 18 to 22 carbon atoms as the fatty acid structure, it was possible to further improve low-temperature fixability while maintaining excellent tackiness.

[0265] Toner 36 of Comparative Example 1 did not contain a crystalline additive, and therefore had poor low-temperature fixability, and fixation was insufficient at the target paper feed speed. Toner 37 of Comparative Example 2 had insufficient tacking properties because the binder resin did not contain the second structural unit represented by the general formula (2) above. Toner 38 of Comparative Example 3 had poor low-temperature fixability and insufficient tackiness because the binder resin did not contain the first structural unit represented by the general formula (1) above. Toner 39 of Comparative Example 4 used n-docosane (a linear alkane having 22 carbon atoms) as additive C, but no improvement in tackiness was observed. [Industrial Applicability]

[0266] According to the present invention, it is possible to provide a toner for developing electrostatic images that can improve low-temperature fixability while maintaining tackiness. [Explanation of symbols]

[0267] 90 Transfer material 100 Image forming device 101 Main casing 108 Intermediate transfer belt 110Y, 110M, 110C, 110K image forming segments 112 Secondary transfer roller 120 Transport roller 125 Cleaning Device 126 Toner collection box 130 Fixing device 131 Pressure roller 132 heated roller 190 Photosensitive drum 191 Charging device 192 Exposure equipment 193 Developing device 194 Primary transfer roller 195 Cleaning Device 200 control section 201 Weight 202 Aluminum plate 203 Inserted paper 204 Thermocouple 205 Tape 206 Fixed image

Claims

1. A toner for developing electrostatic images, comprising toner base particles, the toner base particles contain at least a binder resin, a crystalline additive, and a colorant, The toner for developing electrostatic images, wherein the binder resin contains a polymer having a first structural unit represented by the following general formula (1) and a second structural unit represented by the following general formula (2): 【Chemical 1】 [In general formula (1), R １ is a hydrogen atom or a methyl group, and R ２ represents an alicyclic substituent having 6 to 12 carbon atoms.] 【Chemistry 2】 [In general formula (2), R ３ is a hydrogen atom or a methyl group, and R ４ represents a methyl group or an ethyl group.

2. 2. The toner for developing electrostatic images according to claim 1, wherein the crystalline additive is at least one selected from the group consisting of fatty acid amides, fatty acid diesters, and fatty acid monoesters.

3. 3. The toner for developing electrostatic images according to claim 2, wherein the crystalline additive is a fatty acid amide having a linear alkyl group having 18 to 22 carbon atoms as a fatty acid structure.

4. 3. The toner for developing electrostatic images according to claim 2, wherein the crystalline additive is a fatty acid diester having a linear alkyl group having 18 to 22 carbon atoms as a fatty acid structure.

5. 3. The toner for developing electrostatic images according to claim 2, wherein the crystalline additive is a fatty acid monoester having a linear alkyl group having 18 to 22 carbon atoms as a fatty acid structure.

6. 3. The toner for developing electrostatic images according to claim 1, wherein the polymer has a structural unit different from both the first structural unit and the second structural unit.

7. 7. The toner for developing electrostatic images according to claim 6, wherein the other structural unit has a structural unit derived from at least one polymerizable monomer selected from the group consisting of styrene, (meth)acrylic acid, and (meth)acrylic acid esters.

8. 8. The toner for developing electrostatic images according to claim 7, wherein the other structural unit has a structural unit derived from (meth)acrylic acid.

9. A method for producing a toner for developing electrostatic images, comprising: a step A of copolymerizing a polymerizable monomer represented by the following general formula (3) and a polymerizable monomer represented by the following general formula (4) to obtain a polymer; and a step B of forming toner base particles containing the obtained polymer: 【Chemistry 3】 [In general formula (3), R １ is a hydrogen atom or a methyl group, and R ２ represents an alicyclic substituent having 6 to 12 carbon atoms.] 【Chemistry 4】 [In general formula (4), R ３ is a hydrogen atom or a methyl group, and R ４ represents a methyl group or an ethyl group.

10. 10. The method for producing a toner for developing an electrostatic image according to claim 9, wherein in the step B, the toner base particles are formed containing the polymer obtained in the step A, a colorant, and a crystalline additive.

11. 11. The method for producing a toner for developing electrostatic images according to claim 9, wherein the step A includes a step of obtaining a dispersion of the polymer, and the step B includes a step of mixing the dispersion of the polymer obtained in the step A.

12. 3. An image forming method comprising: a step of adhering the electrostatic image developing toner according to claim 1 or claim 2 to a recording medium; and a step of fixing the electrostatic image developing toner adhered to the recording medium to the recording medium.

13. 3. An image forming apparatus comprising: an attachment unit that attaches the electrostatic image developing toner according to claim 1 or 2 to a recording medium; and a fixing unit that fixes the electrostatic image developing toner attached to the recording medium to the recording medium.

Images