Image forming method and image forming system

Abstract

To provide an image forming method and an image forming system that can improve the low temperature fixability and heat-resistant storage properties of a toner for electrostatic charge image development and can form an image with a wide color gamut.SOLUTION: An image forming method of the present invention uses a toner for electrostatic charge image development including toner particles. The toner particle contains amorphous polyester and crystalline polyester. A content percentage of a structural unit derived from a bisphenol A derivative is 30 mol% or less based on 100 mol% of all structural units derived from polyhydric alcohols in the amorphous polyester. The image forming method includes: a fixing step of bringing a first fixing member into contact with a recording medium on which a toner image including the toner for electrostatic charge image development is formed and fixing the toner image to the recording medium; and a cooling step of cooling the recording medium by bringing a first cooling member into contact with the recording medium separated from the first fixing member.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an image forming method and an image forming system, and more particularly to an image forming method and an image forming system capable of forming an image having a wide color gamut and excellent low-temperature fixing ability of a toner for developing an electrostatic image. [Background technology]

[0002] Print-on-demand has become increasingly popular in recent years due to its convenience and rapidity in data processing. In the field of print-on-demand, there is a demand for further energy saving and speedup, as well as the provision of images with higher customer satisfaction. For this reason, there is a demand for improved low-temperature fixability in toners for developing electrostatic images (hereinafter also simply referred to as "toners"), and for an expansion of the color gamut of images.

[0003] In order to improve the low-temperature fixing property of a toner, it is necessary to lower the melting temperature and melt viscosity of the binder resin. Toners that have improved low-temperature fixing property by adding a crystalline resin such as crystalline polyester as a plasticizer (fixing aid) have been proposed.

[0004] Amorphous polyesters are widely used as binder resins. From the viewpoint of achieving both low-temperature fixability and heat-resistant storage stability, bisphenol A derivatives are preferably used as the alcohol component of amorphous polyesters (see Patent Document 1). However, amorphous polyesters having structural units derived from bisphenol A derivatives have insufficient low-temperature fixability due to their rigid molecular structure. In the invention described in Patent Document 2, the low-temperature fixability of toners is improved by using amorphous polyesters that do not have structural units derived from bisphenol A derivatives. However, this technology has room for further study from the viewpoint of expanding the color gamut of images. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2016-66018 A [Patent Document 2] JP 2017-062344 A Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an image forming method and an image forming system capable of forming an image having a wide color gamut and having a high low-temperature fixing property of a toner for developing an electrostatic image. [Means for solving the problem]

[0007] In order to solve the above problems, the present inventors have investigated the causes of the above problems, etc. As a result, the present inventors have found that the above problems can be solved by setting the content of structural units derived from bisphenol A derivatives to 30 mol % or less relative to 100 mol % of all structural units derived from polyhydric alcohols in the amorphous polyester, and further cooling the recording medium by bringing a cooling member into contact with the recording medium separated from the fixing member in the cooling step, thereby arriving at the present invention. That is, the above-mentioned problems of the present invention are solved by the following means.

[0008] 1. An image forming method using a toner for developing an electrostatic image containing toner particles, comprising: the toner particles contain an amorphous polyester and a crystalline polyester, the content of structural units derived from bisphenol A derivatives in the amorphous polyester is 30 mol % or less relative to 100 mol % of all structural units derived from polyhydric alcohols; a fixing step of fixing the toner image on the recording medium by contacting a first fixing member with the recording medium on which the toner image containing the electrostatic image developing toner is formed; a cooling step of contacting the recording medium separated from the first fixing member with a first cooling member to cool the recording medium, 1. An image forming method comprising:

[0009] 2. The content of structural units derived from bisphenol A derivatives relative to 100 mol % of all structural units derived from polyhydric alcohols in the amorphous polyester is 10 mol % or less. 2. The image forming method according to claim 1,

[0010] 3. The first fixing member is a fixing belt; In the fixing step, a fixing pad is further used. 3. The image forming method according to claim 1 or 2,

[0011] 4. In the fixing step, fixing is performed in one step. 4. The image forming method according to claim 3,

[0012] 5. In the fixing step, the toner image is heated multiple times. 4. The image forming method according to claim 3,

[0013] 6. The amorphous polyester has a structural unit derived from an aliphatic polyhydric alcohol having 3 to 6 carbon atoms. 3. The image forming method according to claim 1 or 2,

[0014] 7. The crystalline polyester has a structural unit derived from an aliphatic polyhydric alcohol having 6 to 12 carbon atoms and a structural unit derived from an aliphatic polycarboxylic acid having 6 to 12 carbon atoms. 3. The image forming method according to claim 1 or 2,

[0015] 8. In the cooling step, a second cooling member is further used to hold the recording medium together with the first cooling member. 3. The image forming method according to claim 1 or 2,

[0016] 9. An image forming system using a toner for developing an electrostatic image, the toner comprising toner particles, the toner particles contain an amorphous polyester and a crystalline polyester, the content of structural units derived from bisphenol A derivatives in the amorphous polyester is 30 mol % or less relative to 100 mol % of all structural units derived from polyhydric alcohols; a fixing unit that brings a first fixing member into contact with a recording medium on which a toner image containing the electrostatic image developing toner is formed, thereby fixing the toner image to the recording medium; a cooling unit that brings a first cooling member into contact with the recording medium separated from the first fixing member to cool the recording medium, 1. An image forming system comprising: Effect of the Invention

[0017] According to the above-mentioned means of the present invention, it is possible to provide an image forming method and an image forming system which are capable of forming an image having a wide color gamut and which has high low-temperature fixing property of a toner for developing an electrostatic image.

[0018] Although the mechanism by which the effects of the present invention are manifested or the mechanism by which the effects of the present invention are acted upon has not been clearly understood, it is speculated as follows.

[0019] As mentioned above, it is useful to include crystalline polyester in the toner in order to ensure low-temperature fixability. However, when a toner containing crystalline polyester is used, crystalline polyester domains are formed in the image. The crystalline polyester domains are a source of internally scattered light. Therefore, even if the pigment dispersion in the image is good, the saturation is reduced due to the internally scattered light caused by the crystalline polyester domains. For these reasons, when a toner containing crystalline polyester is used, it is difficult to form an image with a wide color gamut.

[0020] In the present invention, the amount of internally scattered light in an image is suppressed, thereby enabling the formation of an image with an expanded color gamut. In order to suppress the amount of internally scattered light in an image, the present inventors focused on crystalline polyester domains, which can be a source of internally scattered light. By suppressing the crystallinity of the crystalline polyester in the crystalline polyester domains to a low level, it is possible to make it difficult for internal scattering to occur in the crystalline regions. In addition, by suppressing the size of the crystalline polyester domains to be small, it is possible to reduce the source of internal scattering.

[0021] First, the present invention is characterized in that the content of structural units derived from bisphenol A derivatives relative to 100 mol % of all structural units derived from polyhydric alcohols in the amorphous polyester (hereinafter also referred to as "BPAD content in APEs") is 30 mol % or less. Since the structural units derived from bisphenol A derivatives are aromatic components, they have lower compatibility with crystalline polyesters than aliphatic components. Therefore, when the BPAD content in APEs is high, the compatibility between crystalline polyesters and amorphous polyesters is low. In the present invention, the BPAD content in APEs is set to 30 mol % or less, so that the compatibility between crystalline polyesters and amorphous polyesters is high. As a result, in the present invention, the crystalline polyester is in a state where it is difficult to crystallize, and the crystallinity (ratio of crystalline regions) of the crystalline polyester in the crystalline polyester domain is likely to be low.

[0022] Secondly, the present invention is characterized in that in the cooling step, the recording medium separated from the fixing member is brought into contact with a cooling member to cool the recording medium. This allows the toner image fixed on the recording medium to be rapidly cooled. The size of the crystalline polyester domains increases through a kinetic process. Therefore, by rapidly cooling the toner image, the size of the crystalline polyester domains can be kept small.

[0023] A sufficient color gamut cannot be obtained with only one of the above two features, but the combination of the two features is most effective. [Brief description of the drawings]

[0024] [Figure 1] Schematic diagram of fixing device 1 [Diagram 2] Schematic diagram of fixing device 2 [Diagram 3] Schematic diagram of fixing device 3 [Figure 4] Schematic diagram of fixing device 4 [Diagram 5] Schematic diagram of the cooling device 5 [Figure 6] Schematic diagram of cooling device 6 [Figure 7A] Schematic diagram of the cooling device 7 [Figure 7B] A top view of the cooling device 7 [Figure 8] Schematic diagram of the fixing-cooling unit 8 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] The image forming method of the present invention is an image forming method using a toner for developing electrostatic images containing toner particles, the toner particles containing an amorphous polyester and a crystalline polyester, the content of structural units derived from bisphenol A derivatives in the amorphous polyester relative to 100 mol % of all structural units derived from polyhydric alcohols is 30 mol % or less, and the image forming method includes a fixing step of contacting a first fixing member with a recording medium on which a toner image containing the toner for developing electrostatic images has been formed, thereby fixing the toner image to the recording medium, and a cooling step of contacting a first cooling member with the recording medium separated from the first fixing member, thereby cooling the recording medium. This feature is a technical feature common to or corresponding to the following embodiments.

[0026] In an embodiment of the present invention, the content of structural units derived from bisphenol A derivatives in the amorphous polyester is preferably 10 mol % or less relative to 100 mol % of all structural units derived from polyhydric alcohols, which leads to improved low-temperature fixability of the toner and a wider color gamut.

[0027] In an embodiment of the present invention, it is preferable that the first fixing member is a fixing belt, and a fixing pad is further used in the fixing step. This makes it easier to sufficiently heat the toner image, and further suppresses the amount of internally scattered light. In addition, it is easier to improve the uniformity of the image surface.

[0028] In an embodiment of the present invention, the fixing step may be performed in one step, which allows the fixing step to be completed in a short time and also simplifies the structure of the fixing device.

[0029] In an embodiment of the present invention, the toner image may be heated multiple times in the fixing step, which makes it easier to heat the toner image sufficiently and further suppresses the amount of internally scattered light.

[0030] In an embodiment of the present invention, the amorphous polyester preferably has a structural unit derived from an aliphatic polyhydric alcohol having 3 to 6 carbon atoms. The structural unit has higher compatibility with crystalline polyester than a structural unit derived from a bisphenol A derivative. Therefore, the structural unit derived from an aliphatic polyhydric alcohol having 3 to 6 carbon atoms can reduce the crystallinity (ratio of crystalline region) of the crystalline polyester in the crystalline polyester domain. This reduces the occurrence of internally scattered light, and exerts the effect of expanding the color gamut. Furthermore, the structural unit is also preferable from the viewpoint of low-temperature fixability.

[0031] In an embodiment of the present invention, the crystalline polyester preferably has a structural unit derived from an aliphatic polyhydric alcohol having 6 to 12 carbon atoms and a structural unit derived from an aliphatic polycarboxylic acid having 6 to 12 carbon atoms. When the structural unit has 12 or less carbon atoms, the polarity of the crystalline polyester increases, and the compatibility between the crystalline polyester and the amorphous polyester increases. This reduces the crystallinity of the crystalline polyester inside the image. This reduces the generation of internal scattered light, and exhibits the effect of expanding the color gamut. In addition, when the structural unit has 12 or less carbon atoms, the low-temperature fixability is also good. When the structural unit has 6 or more carbon atoms, the heat-resistant storage property of the toner is good. Therefore, by using the crystalline polyester, it is possible to expand the color gamut and improve the low-temperature fixability while ensuring the heat-resistant storage property of the toner.

[0032] In an embodiment of the present invention, it is preferable that a second cooling member is further used in the cooling step to sandwich the recording medium together with the first cooling member. By sandwiching the recording medium between the first cooling member and the second cooling member that are in contact with the recording medium, the image cooling speed can be increased.

[0033] The image forming system of the present invention is an image forming system that uses a toner for developing electrostatic images containing toner particles, the toner particles containing an amorphous polyester and a crystalline polyester, and the content of structural units derived from bisphenol A derivatives in the amorphous polyester relative to 100 mol % of all structural units derived from polyhydric alcohols is 30 mol % or less, and the image forming system has a fixing means that brings a first fixing member into contact with a recording medium on which a toner image containing the toner for developing electrostatic images has been formed, thereby fixing the toner image to the recording medium, and a cooling means that brings a first cooling member into contact with the recording medium separated from the first fixing member, thereby cooling the recording medium.

[0034] The present invention will be described in detail below. In this application, the symbol "to" is used to mean that the numerical values ​​before and after it are included as a lower limit and an upper limit.

[0035] [1. Overview of the image forming method of the present invention] The image forming method of the present invention is an image forming method using a toner for developing electrostatic images, which contains toner particles. The toner particles contain an amorphous polyester and a crystalline polyester. The content of structural units derived from bisphenol A derivatives relative to 100 mol % of all structural units derived from polyhydric alcohols in the amorphous polyester is 30 mol % or less. The image forming method includes a fixing step and a cooling step. In the fixing step, a first fixing member is brought into contact with a recording medium on which a toner image containing a toner for developing electrostatic images has been formed, thereby fixing the toner image to the recording medium. In the cooling step, a first cooling member is brought into contact with the recording medium separated from the first fixing member, thereby cooling the recording medium.

[0036] The image forming method of the present invention may include other steps, such as a toner image forming step of forming an unfixed toner image before the fixing step.

[0037] [2. Toner for developing electrostatic images] In the present invention, the term "toner for developing electrostatic images" refers to an aggregate of toner particles. Hereinafter, the term "toner for developing electrostatic images" will also be simply referred to as "toner".

[0038] The toner particles may be composed of only toner base particles, or may be composed of toner base particles and an external additive attached to the surface of the toner base particles. The "toner base particles" are particles that constitute the base of the toner particles. The toner base particles contain a binder resin such as amorphous polyester, and may also contain a colorant, a release agent (wax), a charge control agent, etc., as necessary.

[0039] The toner particles according to the present invention contain an amorphous polyester and a crystalline polyester. Specifically, the toner base particles constituting the toner particles contain an amorphous polyester and a crystalline polyester.

[0040] [2-1. Amorphous polyester] Amorphous polyester is a polyester that exhibits amorphousness and is obtained by a polymerization reaction between a divalent or higher carboxylic acid (polycarboxylic acid) and a divalent or higher alcohol (polyalcohol).

[0041] "Amorphous" means that it does not have a melting point. In other words, "amorphous" means that it does not have a clear endothermic peak when heated in an endothermic curve obtained by differential scanning calorimetry (DSC). "Clear endothermic peak" means a peak with a half-width of 15°C or less in an endothermic curve when heated at a heating rate of 10°C / min.

[0042] The amorphous polyester can be synthesized, for example, by esterifying a polyvalent carboxylic acid and a polyhydric alcohol through polycondensation using a known esterification catalyst.

[0043] In the present invention, the content of structural units derived from bisphenol A derivatives (BPAD) relative to 100 mol % of all structural units derived from polyhydric alcohols in amorphous polyesters (APEs) is also referred to as the "BPAD content in APEs".

[0044] The BPAD content in the APEs in the present invention is 30 mol % or less. From the viewpoints of color gamut and low-temperature fixability, the BPAD content in the APEs is preferably 10 mol % or less, and more preferably 0 mol %.

[0045] The bisphenol A derivative includes bisphenol A and its derivatives. Examples of the bisphenol A derivative include bisphenol A, an ethylene oxide adduct of bisphenol A, and a propylene oxide adduct of bisphenol A. In the present invention, phenols such as bisphenol A are also included in alcohols. This definition is based on the viewpoint that phenols such as bisphenol A can be esterified in the same way as alcohols.

[0046] Examples of polyhydric alcohols other than bisphenol A derivatives that can be used in the synthesis of amorphous polyesters include dihydric or trihydric alcohols such as ethylene glycol, propylene glycol, 1,4-butanediol, 2,3-butanediol, diethylene glycol, triethylene glycol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, glycerin, sorbitol, 1,4-sorbitan, trimethylolpropane, etc. The polyhydric alcohols may be used alone or in combination of two or more.

[0047] The amorphous polyester preferably has a structural unit derived from an aliphatic polyhydric alcohol having 3 to 6 carbon atoms. This structural unit has higher compatibility with crystalline polyester than a structural unit derived from a bisphenol A derivative. Therefore, the structural unit derived from an aliphatic polyhydric alcohol having 3 to 6 carbon atoms can reduce the crystallinity (ratio of crystalline region) of the crystalline polyester in the crystalline polyester domain. This reduces the occurrence of internally scattered light, and exerts the effect of expanding the color gamut. Furthermore, this structural unit is also preferable from the viewpoint of low-temperature fixability.

[0048] For these reasons, it is preferable to use an aliphatic polyhydric alcohol having 3 to 6 carbon atoms in the synthesis of the amorphous polyester.

[0049] Examples of polycarboxylic acids that can be used in the synthesis of the amorphous polyester include phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, naphthalene-2,6-dicarboxylic acid, malonic acid, mesaconic acid, dimethyl isophthalate, fumaric acid, dodecenylsuccinic acid, 1,10-dodecanedicarboxylic acid, etc. The polycarboxylic acids may be used alone or in combination of two or more.

[0050] Examples of catalysts that can be used in the synthesis of amorphous polyesters include metal-containing compounds, phosphorous compounds, phosphoric acid compounds, amine compounds, etc. Examples of metals contained in metal-containing compounds include sodium, lithium, magnesium, calcium, aluminum, zinc, manganese, antimony, titanium, tin, zirconium, germanium, etc. These may be used alone or in combination of two or more.

[0051] The polymerization temperature is not particularly limited, but is preferably within the range of 150 to 250° C. The polymerization time is not particularly limited, but is preferably within the range of 0.5 to 10 hours. During the polymerization, the pressure in the reaction system may be reduced as necessary.

[0052] The glass transition point Tg of the amorphous polyester is preferably in the range of 25 to 60°C, more preferably in the range of 35 to 55°C, from the viewpoint of achieving both sufficient low-temperature fixability and heat-resistant storage stability. The glass transition point Tg can be measured using a differential scanning calorimeter, for example, Diamond DSC (manufactured by PerkinElmer). Specifically, 3.0 mg of a sample is sealed in an aluminum pan, and the temperature is changed in the order of heating, cooling, and heating. During the first and second heating, the temperature is raised from 0°C to 150°C at a heating rate of 10°C / min and held at 150°C for 1 minute. During cooling, the temperature is lowered from 150°C to 0°C at a heating rate of 10°C / min and held at 0°C for 1 minute. The shift of the baseline is observed in the measurement curve obtained during the second heating. The intersection of the extension line of the baseline before the shift and the tangent line showing the maximum slope of the shifted portion of the baseline is taken as the glass transition point Tg. An empty aluminum pan is used as a reference.

[0053] The weight average molecular weight Mw of the amorphous polyester can be, for example, within the range of 10000 to 100000. The weight average molecular weight Mw can be measured by gel permeation chromatography (GPC).

[0054] The amorphous polyester may be a hybrid amorphous polyester having a graft copolymer structure of an amorphous polyester polymer segment and a styrene-acrylic polymer segment.

[0055] The content of the amorphous polyester in the toner base particles is preferably 20% by mass or more, and more preferably 50% by mass or more, from the viewpoint of low-temperature fixability.

[0056] (Method of analyzing components of amorphous polyester) For the analysis of the constituent components of polyester, a pretreatment using chemical decomposition is effective. There are various types of chemical decomposition, but for the composition analysis of polyester, which is a condensation resin, for example, alkaline hydrolysis and supercritical methanol decomposition are effective methods.

[0057] Examples of the alkaline hydrolysis method include the following method. The toner and hydrolysis liquid (alkali agent, water, and organic solvent) are placed in a high-pressure wet decomposition crucible, and heated in an oven at 80 to 150°C for 3 hours. The oven temperature and heating time may be changed depending on the composition of the sample. The alkaline agent is, for example, sodium hydroxide, potassium hydroxide, etc. The organic solvent is, for example, methanol, DMSO (dimethyl sulfoxide), etc. A small autoclave may be used as the container.

[0058] The molar ratio of each component can be calculated from the peaks derived from bisphenol A derivatives and other polyhydric alcohols in the proton nuclear magnetic resonance (1H-NMR) spectrum of the decomposition liquid after hydrolysis of the toner. If the molar ratio of each component cannot be calculated from the 1H-NMR spectrum due to the influence of the matrix components, it is also possible to analyze the composition of the polyhydric alcohol from the GC chromatogram of the decomposition liquid. The BPAD content in APEs can be calculated by the above method. The molar ratio of carboxylic acids can be analyzed in the same way by performing a derivatization treatment on the decomposition liquid.

[0059] The method for measuring the carbon number and content (ratio) of the constituents (constituent units) of polyester is as described above. These can be identified by pyrolysis gas chromatography (GC / MS: Gas Chromatography / Mass Spectrometry) in addition to 1H-NMR measurement.

[0060] [2-2. Crystalline polyester] Crystalline polyester is a polyester that exhibits crystallinity and is obtained by a polymerization reaction between a divalent or higher carboxylic acid (polycarboxylic acid) and a divalent or higher alcohol (polyalcohol).

[0061] "Crystalline" means having a melting point. In other words, "crystalline" means having a clear endothermic peak when heating in an endothermic curve obtained by differential scanning calorimetry (DSC). "Clear endothermic peak" means a peak with a half-width of 15°C or less in an endothermic curve when heated at a heating rate of 10°C / min.

[0062] The melting point Tm of the crystalline polyester is preferably 75°C or less. The melting point Tm is the temperature at the top of the endothermic peak, and can be measured using a differential scanning calorimeter, such as a Diamond DSC (manufactured by PerkinElmer). The specific measurement procedure is as follows. 0.5 mg of the sample is sealed in an aluminum pan KIT NO. B0143013, and the temperature is changed in the order of heating, cooling, and heating. During the first and second heating, the temperature is raised from 0°C to 150°C at a heating rate of 10°C / min and held at 150°C for 1 minute. During the cooling, the temperature is lowered from 150°C to 0°C at a heating rate of 10°C / min and held at 0°C for 1 minute. The temperature at the top of the endothermic peak in the endothermic curve obtained during the second heating is taken as the melting point Tm. An empty aluminum pan is used as a reference.

[0063] The crystalline polyester can be produced by esterifying a polyvalent carboxylic acid and a polyhydric alcohol through polycondensation using a known esterification catalyst.

[0064] Examples of divalent polycarboxylic acids that can be used in the synthesis of crystalline polyesters include saturated aliphatic dicarboxylic acids, unsaturated aliphatic dicarboxylic acids, and unsaturated aromatic dicarboxylic acids. Examples of saturated aliphatic dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid (dodecanedioic acid), 1,11-undecanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,13-tridecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,16-hexadecanedicarboxylic acid, and 1,18-octadecanedicarboxylic acid. Examples of unsaturated aliphatic dicarboxylic acids include methylenesuccinic acid, fumaric acid, maleic acid, 3-hexenedioic acid, 3-octenedioic acid, and dodecenylsuccinic acid. Examples of unsaturated aromatic dicarboxylic acids include phthalic acid, terephthalic acid, isophthalic acid, t-butylisophthalic acid, tetrachlorophthalic acid, chlorophthalic acid, nitrophthalic acid, p-phenylene diacetic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, anthracene dicarboxylic acid, etc. Lower alkyl esters and acid anhydrides of these dicarboxylic acids can also be used as polyvalent carboxylic acids.

[0065] Examples of trivalent or higher polyvalent carboxylic acids that can be used in the synthesis of the crystalline polyester include trimellitic acid, pyromellitic acid, etc. The polyvalent carboxylic acids may be used alone or in combination of two or more kinds.

[0066] Examples of dihydric polyhydric alcohols that can be used in the synthesis of crystalline polyesters include saturated aliphatic diols, unsaturated aliphatic diols, aromatic diols, etc. Examples of saturated aliphatic diols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,18-octadecanediol, 1,20-eicosanediol, neopentyl glycol, etc. Examples of unsaturated aliphatic diols include 2-butene-1,4-diol, 3-butene-1,4-diol, 2-butyne-1,4-diol, 3-butyne-1,4-diol, and 9-octadecene-7,12-diol. Examples of aromatic diols include bisphenols and alkylene oxide adducts of bisphenols. Examples of bisphenols include bisphenol A and bisphenol F. Examples of alkylene oxide adducts of bisphenols include ethylene oxide adducts of bisphenols and propylene oxide adducts of bisphenols. Derivatives of these diols can also be used as polyhydric alcohols. The polyhydric alcohols may be used alone or in combination of two or more.

[0067] The crystalline polyester preferably has a structural unit derived from an aliphatic polyhydric alcohol having 6 to 12 carbon atoms and a structural unit derived from an aliphatic polycarboxylic acid having 6 to 12 carbon atoms. When the structural unit has 12 or less carbon atoms, the polarity of the crystalline polyester increases, and the compatibility between the crystalline polyester and the amorphous polyester increases. This reduces the crystallinity of the crystalline polyester inside the image. This reduces the generation of internal scattered light, and exhibits the effect of expanding the color gamut. In addition, when the structural unit has 12 or less carbon atoms, the low-temperature fixability is also good. When the structural unit has 6 or more carbon atoms, the heat-resistant storage property of the toner is good. Therefore, by using the above crystalline polyester, it is possible to expand the color gamut and improve the low-temperature fixability while ensuring the heat-resistant storage property of the toner.

[0068] For these reasons, in the synthesis of the crystalline polyester, it is preferable to use an aliphatic polyhydric alcohol having 6 to 12 carbon atoms and an aliphatic polycarboxylic acid having 6 to 12 carbon atoms.

[0069] For the synthesis of the crystalline polyester, the above-mentioned catalysts that can be used for the synthesis of the amorphous polyester can be used.

[0070] The polymerization temperature is not particularly limited, but is preferably within the range of 70 to 250° C. The polymerization time is not particularly limited, but is preferably within the range of 0.5 to 10 hours. During the polymerization, the reaction system may be decompressed as necessary.

[0071] The crystalline polyester may be a hybrid crystalline polyester having a graft copolymer structure of a crystalline polyester polymerized segment and a styrene-acrylic polymerized segment.

[0072] The weight average molecular weight Mw of the crystalline polyester is preferably within a range of 1000 to 29000. The weight average molecular weight Mw can be measured by gel permeation chromatography (GPC).

[0073] The content of the crystalline polyester is preferably within a range of 1 to 20% by mass, and more preferably within a range of 3 to 15% by mass, based on the total amount of the resin contained in the toner base particles.

[0074] (Method of analyzing components of crystalline polyester) The structure and content (ratio) of the constituent components (constituent units) of the crystalline polyester can be analyzed by the same method as the above-mentioned method for analyzing the constituent components of the amorphous polyester.

[0075] [2-3. Vinyl resin] The toner particles according to the present invention may contain a vinyl resin.

[0076] The vinyl resin refers to a polymer of a monomer having a vinyl group (hereinafter referred to as a vinyl monomer) that exhibits amorphous properties.

[0077] Examples of vinyl resins that can be used include styrene-acrylic resin, styrene resin, acrylic resin, etc., and among these, styrene-acrylic resin, which has excellent heat resistance, is preferred.

[0078] Usable vinyl monomers include the following, and one of these may be used alone or two or more of them may be used in combination.

[0079] (1) Styrene-based monomers Monomers having a styrene structure, such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, and derivatives thereof (2) (Meth)acrylic acid ester monomers Monomers having a (meth)acrylic group, such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isopropyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, phenyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, and derivatives thereof. (3) Vinyl esters Vinyl propionate, vinyl acetate, vinyl benzoate, etc. (4) Vinyl ethers Vinyl methyl ether, vinyl ethyl ether, etc. (5) Vinyl ketones Vinyl methyl ketone, vinyl ethyl ketone, vinyl hexyl ketone, etc. (6) N-vinyl compounds N-vinylcarbazole, N-vinylindole, N-vinylpyrrolidone, etc. (7)Other Vinyl compounds such as vinylnaphthalene and vinylpyridine, acrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide, and methacrylic acid derivatives, etc.

[0080] As the vinyl monomer, a monomer having an ionically dissociable group such as a carboxy group, a sulfonic acid group, or a phosphoric acid group is preferred because it makes it easier to control the affinity with the crystalline resin.

[0081] Examples of monomers having a carboxy group include acrylic acid, methacrylic acid, maleic acid, itaconic acid, cinnamic acid, fumaric acid, maleic acid monoalkyl esters, and itaconic acid monoalkyl esters.

[0082] Examples of monomers having a sulfonic acid group include styrenesulfonic acid, allylsulfosuccinic acid, and 2-acrylamido-2-methylpropanesulfonic acid.

[0083] An example of a monomer having a phosphoric acid group is acidophosphooxyethyl methacrylate.

[0084] A polymer having a crosslinked structure can be obtained by using a polyfunctional vinyl as the vinyl monomer. Examples of the polyfunctional vinyl include divinylbenzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol diacrylate, neopentyl glycol dimethacrylate, and neopentyl glycol diacrylate.

[0085] [2-4. Release agent] The toner particles according to the present invention preferably contain a release agent.

[0086] The release agent is not particularly limited, and various known waxes can be used.

[0087] Examples of the release agent that can be used include branched chain hydrocarbon waxes, long chain hydrocarbon waxes, dialkyl ketone waxes, ester waxes, amide waxes, etc. Examples of the branched chain hydrocarbon waxes include polyolefin waxes such as polyethylene wax and polypropylene wax, and microcrystalline waxes. Examples of the long chain hydrocarbon waxes include paraffin wax, Fischer-Tropsch wax, and Sasol wax. Examples of the dialkyl ketone waxes include distearyl ketone. Examples of the ester waxes include carnauba wax, montan wax, behenyl behenate, trimethylolpropane tribehenate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecanediol distearate, tristearyl trimellitate, distearyl maleate, and stearyl stearate. Examples of amide waxes include ethylenediamine behenylamide and trimellitic acid tristearylamide.

[0088] These release agents may be used alone or in combination of two or more.

[0089] The melting point Tm of the release agent is preferably 50° C. or more and 100° C. or less. When the melting point Tm is 100° C. or less, the release agent is easily melted during fixing, and the release agent is easily separated from the fixing member. When the melting point Tm is 50° C. or more, the release agent is less likely to volatilize during fixing and is less likely to become fine particles, which is preferable in terms of environmental impact.

[0090] The melting point Tm is the temperature at the top of the endothermic peak, and can be measured by DSC. The specific measurement procedure is as follows. 0.5 mg of the sample is sealed in an aluminum pan, and the temperature is changed in the order of heating, cooling, and heating. During the first and second heating, the temperature is raised from 0°C to 150°C at a heating rate of 10°C / min and held at 150°C for 1 minute. During cooling, the temperature is lowered from 150°C to 0°C at a cooling rate of 10°C / min and held at 0°C for 1 minute. The temperature at the top of the endothermic peak in the endothermic curve obtained during the second heating is taken as the melting point Tm. When multiple endothermic peaks are detected, the peak top temperature of the highest endothermic peak is taken as the melting point Tm of the release agent. An empty aluminum pan is used as a reference.

[0091] The content of the release agent is preferably in the range of 1 to 20% by mass, more preferably in the range of 3 to 18% by mass, based on the total amount of the resin contained in the toner base particles. By having the content of the release agent in the above range, sufficient fixing separation property can be obtained.

[0092] [2-5. Colorants] The toner particles according to the present invention may contain a colorant.

[0093] The colorant may be a known inorganic or organic colorant, such as carbon black, magnetic powder, organic pigments, inorganic pigments, dyes, etc.

[0094] Examples of colorants for obtaining black toner include carbon black such as furnace black and channel black, magnetic materials such as magnetite and ferrite, dyes, inorganic pigments including non-magnetic iron oxide, etc. Examples of colorants for obtaining color toner include known dyes, organic pigments, etc.

[0095] Examples of organic pigments include CI Pigment Red 5, 48:1, 53:1, 57:1, 81:4, 122, 139, 144, 149, 166, 177, 178, 222, 238, 269, CI Pigment Yellow 14, 17, 74, 93, 94, 138, 155, 180, 185, CI Pigment Orange 31, 43, CI Pigment Blue 15:3, 60, and 76.

[0096] Examples of dyes include CI Solvent Red 1, 49, 52, 58, 68, 11, and 122, CI Solvent Yellow 19, 44, 77, 79, 81, 82, 93, 98, 103, 104, 112, and 162, CI Solvent Blue 25, 36, 69, 70, 93, and 95.

[0097] The colorant for obtaining the toner of each color may be contained alone or in combination of two or more kinds for each color.

[0098] The content of the colorant is preferably from 1 to 30% by mass, and more preferably from 2 to 20% by mass, based on the toner particles.

[0099] [2-6. Charge control agents] The toner particles according to the present invention may contain a charge control agent.

[0100] As the charge control agent, known compounds such as nigrosine dyes, metal salts of naphthenic acid, metal salts of higher fatty acids, alkoxylated amines, quaternary ammonium salts, azo metal complexes, and metal salicylate salts can be used. By using a charge control agent, a toner with excellent charging properties can be obtained.

[0101] The content of the charge control agent can usually be within a range of 0.1 to 5.0% by mass based on the total amount of the resin contained in the toner base particles.

[0102] [2-7.External additives] The toner particles according to the present invention preferably contain an external additive.

[0103] Examples of the external additive include inorganic oxide fine particles, inorganic stearic acid compound fine particles, inorganic titanic acid compound fine particles, zirconia particles, etc. The external additives may be used alone or in combination of two or more kinds.

[0104] Examples of inorganic oxide particles include silica particles, alumina particles, titanium oxide particles, zinc oxide particles, chromium oxide particles, cerium oxide particles, antimony oxide particles, tungsten oxide particles, tin oxide particles, tellurium oxide particles, manganese oxide particles, boron oxide particles, etc. Particles mainly composed of these inorganic materials may be hydrophobized with a surface treatment agent such as a silane coupling agent or silicone oil, if necessary. The number-average primary particle size of these particles is preferably within the range of 20 to 200 nm, more preferably within the range of 30 to 150 nm.

[0105] The external additive may be a lubricant such as a metal salt of a higher fatty acid. Examples of the higher fatty acid include stearic acid, oleic acid, palmitic acid, linoleic acid, ricinoleic acid, etc. Examples of the metal constituting the metal salt include zinc, manganese, aluminum, iron, copper, magnesium, calcium, etc.

[0106] Examples of inorganic titanate compound fine particles include strontium titanate and zinc titanate.

[0107] The external additives may be used alone or in combination of two or more.

[0108] The amount of the external additive added is preferably within a range of 0.05 to 5% by mass, more preferably 0.1 to 3% by mass, based on the total amount of the toner base particles. When multiple external additives are used, the amount is the total amount.

[0109] Among the above, the toner particles of the present invention preferably contain silica particles or strontium titanate particles as an external additive.

[0110] (Silica particles) Silica particles are particles mainly composed of silica (SiO2). Silica particles may be either crystalline or amorphous. Silica particles may be particles manufactured using silicon compounds such as water glass and alkoxysilane as raw materials, or may be particles obtained by crushing quartz.

[0111] The silica particles may be, for example, sol-gel silica particles, aqueous colloidal silica particles, alcoholic silica particles, fumed silica particles obtained by a gas phase method, fused silica particles, etc. Among the above, the silica particles are preferably sol-gel silica particles.

[0112] The sol-gel silica particles can be obtained, for example, as follows: Tetraalkoxysilane (TMOS, etc.) is dropped into an alkaline catalyst solution containing an alcohol compound and aqueous ammonia, and the tetraalkoxysilane is hydrolyzed and condensed to obtain a suspension containing sol-gel silica particles. The solvent is then removed from the suspension to obtain a granular material. The granular material is then dried to obtain the sol-gel silica particles.

[0113] The silica particles may be silica particles that have been hydrophobized with a hydrophobizing agent. Examples of the hydrophobizing agent include known organosilicon compounds having an alkyl group (e.g., a methyl group, an ethyl group, a propyl group, a butyl group, etc.). Specific examples of the hydrophobizing agent include an alkoxysilane compound, a siloxane compound, a silazane compound, etc. Among the above, the hydrophobizing agent is preferably at least one of a siloxane compound and a silazane compound. Examples of the siloxane compound include silicone oil, silicone resin, etc. The silicone oil is preferably dimethyl silicone oil. Examples of the silazane compound include hexamethyldisilazane, tetramethyldisilazane, etc. The silazane compound is preferably hexamethyldisilazane (HMDS). The hydrophobizing agent may be used alone or in combination of two or more.

[0114] The amount of the hydrophobizing agent such as a silazane compound attached to the surface of the silica particles is preferably within a range of 0.01 to 5 mass %, more preferably within a range of 0.05 to 3 mass %, and even more preferably within a range of 0.10 to 2 mass %, based on the silica particles, from the viewpoint of improving the hydrophobization degree of the silica particles.

[0115] Examples of the method for subjecting silica particles to a hydrophobizing treatment using a hydrophobizing agent include the following methods. (1) A method in which a hydrophobic treatment agent is dissolved in supercritical carbon dioxide and applied to the surface of silica particles. (2) A method in which a solution containing a hydrophobizing agent is applied (for example, sprayed or coated) to the surface of silica particles in the air. (3) A method in which a solution containing a hydrophobizing agent is added to a silica particle dispersion liquid and maintained in the atmosphere, and then the mixed liquid is dried.

[0116] The number-average particle diameter of the silica particles is preferably 90 nm or more and 130 nm or less. By having a number-average particle diameter of 90 nm or more, the silica particles are more likely to exhibit a spacer effect with other toner particles. As a result, even when the toner base particles have high melting properties, the toner particles are less likely to aggregate together, improving heat-resistant storage properties. By having a number-average particle diameter of 130 nm or less, the silica particles are less likely to detach from the toner base particles, and deterioration of heat-resistant storage properties due to exposure of the toner base particles can be suppressed.

[0117] The number average particle size of the silica particles can be determined by the following procedure. (1) Toner particles are dispersed in methanol, stirred at room temperature (23°C), and then treated in an ultrasonic bath to separate the external additives from the toner base particles. The toner base particles are allowed to settle by centrifugation, and the dispersion liquid in which the external additives are dispersed is recovered. Methanol is distilled off from the dispersion liquid, and the external additives are extracted. (2) The extracted external additive is dispersed in resin particles (polyester, weight average molecular weight Mw=50,000) having a volume average particle diameter of 100 μm. (3) The resin particles with the dispersed external additives were analyzed using an energy dispersive X-ray analyzer (EDX device, manufactured by Horiba, Ltd., EMAX Evolution X-Max 80 mm) 2 Images are taken at a magnification of 40,000 times using a scanning electron microscope (SEM, Hitachi High-Technologies Corporation, S-4800) equipped with a 40000 times magnification. At this time, more than 300 primary silica particles are identified within one field of view based on the presence of Si by EDX analysis. SEM observation is performed with an acceleration voltage of 15 kV, an emission current of 20 μA, and a WD of 15 mm. EDX analysis is performed under the same conditions with a detection time of 60 minutes. (4) The obtained images are imported into an image analyzer (LUZEXIII, manufactured by Nireco Corporation). The area of ​​each particle is determined by analyzing the imported images. (5) From the measured area value, the particle diameter of the silica particles is calculated as the equivalent circle diameter. (6) Select 100 silica particles having an equivalent circle diameter of 80 nm or more. (7) The number average particle size is calculated from the particle sizes of the selected silica particles.

[0118] (Strontium titanate particles) Strontium titanate particles are particles whose main component is strontium titanate (SrTiO3). Strontium titanate particles have a rectangular parallelepiped shape with sharp edges, which is effective for fixing and separating properties.

[0119] The number average primary particle diameter of the strontium titanate particles is preferably from 20 to 200 nm, more preferably from 30 to 150 nm.

[0120] The content of the strontium titanate particles is preferably 0.05 to 2.0% by mass, and more preferably 0.1 to 1.0% by mass, relative to the toner base particles, which provides a good polishing effect while maintaining the toner fluidity.

[0121] The strontium titanate particles can be obtained, for example, by a normal pressure heating reaction method. A specific normal pressure heating reaction method is exemplified below.

[0122] As the titanium oxide source, a mineral acid peptized product of a hydrolyzate of a titanium compound can be used. The titanium oxide source is preferably prepared by peptizing metatitanic acid obtained by a sulfuric acid method and having an SO content of 1.0 mass% or less, preferably 0.5 mass% or less, by adjusting the pH to 0.8 to 1.5 with hydrochloric acid.

[0123] As the strontium oxide source, a metal nitrate, a metal hydrochloride, etc., such as strontium nitrate, strontium chloride, etc., can be used.

[0124] As the aqueous alkali solution, a caustic alkali can be used, and among them, an aqueous sodium hydroxide solution is preferable.

[0125] In the method for producing strontium titanate particles, for example, the following factors affect the particle size, which can be adjusted appropriately to obtain the desired particle size and particle size distribution. (1) Mixing ratio of titanium oxide source and strontium oxide source during reaction (2) Titanium oxide source concentration at the beginning of the reaction (3) Temperature and rate of addition of the alkaline aqueous solution

[0126] In order to prevent the formation of carbonate during the reaction process, it is preferable to prevent contamination with carbon dioxide gas, for example by carrying out the reaction under a nitrogen gas atmosphere.

[0127] The mixing ratio of the titanium oxide source and the strontium oxide source during the reaction is preferably 0.90 to 1.40, more preferably 1.05 to 1.20, in terms of the molar ratio of SrO / TiO2. Within the above range, unreacted titanium oxide is unlikely to remain. The concentration of the titanium oxide source at the beginning of the reaction, assuming that the titanium oxide source is TiO2, is preferably 0.05 to 1.3 mol / L, more preferably 0.08 to 1.0 mol / L.

[0128] The temperature when the alkaline aqueous solution is added is preferably 60 to 100°C. The slower the addition rate of the alkaline aqueous solution, the larger the particle size of the strontium titanate particles that can be obtained. The faster the addition rate of the alkaline aqueous solution, the smaller the particle size of the strontium titanate particles that can be obtained. The addition rate of the alkaline aqueous solution is preferably 0.001 to 1.2 equivalents / h, more preferably 0.002 to 1.1 equivalents / h, based on the charged raw material. The addition rate of the alkaline aqueous solution can be appropriately adjusted depending on the particle size to be obtained.

[0129] It is preferable to further treat the strontium titanate particles obtained by the normal pressure heating reaction with an acid. When the mixing ratio of the titanium oxide source and the strontium oxide source exceeds 1.0 in terms of the molar ratio of SrO / TiO2, unreacted metal sources other than titanium remain after the reaction is completed. The residue may react with carbon dioxide gas in the air to generate impurities such as metal carbonates. If impurities such as metal carbonates remain on the surface, the organic surface treatment agent cannot be uniformly coated due to the influence of the impurities when performing an organic surface treatment to impart hydrophobicity. Therefore, it is preferable to perform an acid treatment to remove the unreacted metal source after adding an alkaline aqueous solution. In the acid treatment, it is preferable to use hydrochloric acid. The pH after adjustment is preferably 2.5 to 7.0, more preferably 4.5 to 6.0. In addition to hydrochloric acid, nitric acid, acetic acid, etc. can be used as the acid.

[0130] [2-8. Toner manufacturing method] Toner base particles are produced, and external additives are added thereto as required, thereby producing a toner.

[0131] The method for producing the toner base particles is not particularly limited, and known methods such as an emulsion aggregation method, a pulverization method, and a suspension polymerization method can be used.

[0132] The toner base particles are preferably produced by a pulverization method. The pulverization method includes a step of obtaining a melt-kneaded product, and a step of obtaining toner particles by pulverizing the melt-kneaded product. In the step of obtaining the melt-kneaded product, a mixture containing a binder resin, a colorant, and other components such as a release agent as required is melt-kneaded.

[0133] The following describes the procedure for producing toner base particles using a pulverization method as an example. First, materials constituting the toner base particles, such as binder resin and colorant, and other components such as release agent and charge control agent as necessary, are weighed out in predetermined amounts, blended, and mixed. Examples of mixing devices include double con mixers, V-type mixers, drum mixers, super mixers, Henschel mixers, Nauta mixers, and Mechano Hybrids.

[0134] Next, the mixed materials are melt-kneaded. In the melt-kneading process, a batch-type kneader such as a pressure kneader or a Banbury mixer, or a continuous kneader can be used. From the viewpoint of continuous production, the device used in the melt-kneading process is preferably a single-screw or twin-screw extruder. Examples of twin-screw extruders include a KTK type twin-screw extruder (manufactured by Kobe Steel, Ltd.), a TEM type twin-screw extruder (manufactured by Toshiba Machine Co., Ltd.), a PCM kneader (manufactured by Ikegai Iron Works Co., Ltd.), a twin-screw extruder (manufactured by KCK Corporation), a Co-Kneader (manufactured by Buss Co., Ltd.), and a Kneadex (manufactured by Nippon Coke and Engineering Co., Ltd.). The temperature of the melt-kneading is preferably about 100 to 200°C. The resin composition obtained by melt-kneading is rolled with a two-roller or the like, and quenched with water or the like in a cooling process.

[0135] Next, the cooled resin composition is pulverized to a desired particle size in a pulverization process. In the pulverization process, the cooled resin composition is coarsely pulverized and then finely pulverized. Examples of pulverizers used for coarse pulverization include a crusher, a hammer mill, and a feather mill. Examples of pulverizers used for fine pulverization include a Cryptron System (manufactured by Kawasaki Heavy Industries, Ltd.), a Super Rotor (manufactured by Nisshin Engineering Co., Ltd.), a Turbo Mill (manufactured by Turbo Kogyo Co., Ltd.), and a fine pulverizer using an air jet system.

[0136] The pulverized product is then classified using a classifier and / or sieving machine as necessary. This results in pulverized toner base particles being obtained as classified products. Examples of classifiers or sieving machines include Elbow Jet (manufactured by Nittetsu Mining Co., Ltd.), which uses an inertial classification method, Turboplex (manufactured by Hosokawa Micron Corporation), TSP Separator (manufactured by Hosokawa Micron Corporation), and Faculty (manufactured by Hosokawa Micron Corporation), which uses a centrifugal classification method.

[0137] The toner base particles are desirably surface-treated with hot air. The surface treatment with hot air allows the shape of the classified product to be adjusted and the surface to be treated. The temperature of the hot air is preferably within a range of 100 to 450°C.

[0138] The toner base particles may be used as a toner as it is. If necessary, an external additive may be added to the surface of the toner base particles to form a toner. As a method for adding an external additive, a method of mixing a predetermined amount of the toner base particles and the external additive and stirring and mixing them using a mixing device may be mentioned. Examples of the mixing device include a double con mixer, a V-type mixer, a drum type mixer, a super mixer, a Henschel mixer, a Nauta mixer, a Mechano Hybrid (manufactured by Nippon Coke & Engineering Co., Ltd.), and a Nobilta (manufactured by Hosokawa Micron Corporation).

[0139] [2-9. Developer] The toner of the present invention may be used alone as a magnetic or non-magnetic one-component developer, or may be mixed with carrier particles and used as a two-component developer.

[0140] As the carrier particles, for example, magnetic particles made of a conventionally known material can be used. Examples of magnetic particles include metals such as iron, ferrite, and magnetite, and alloys of these metals with metals such as aluminum and lead. Ferrite particles are particularly preferred as the carrier particles.

[0141] As the carrier particles, coated carrier particles in which the surfaces of magnetic particles are coated with a coating agent such as resin, or dispersed carrier particles in which magnetic fine powder is dispersed in a binder resin may be used. From the viewpoint of suppressing adhesion of the carrier particles to the photoreceptor, coated carrier particles are preferred.

[0142] The resin for coating is not particularly limited. For example, olefin resin, styrene resin, styrene-acrylic resin, silicone resin, polyester resin, fluororesin, etc. can be used as the resin for coating. The resin for constituting the resin dispersion type carrier is not particularly limited. As such a resin, a known one can be used. Specifically, for example, acrylic resin, styrene-acrylic resin, polyester resin, fluororesin, phenolic resin, etc. can be used.

[0143] The volume-based median diameter of the carrier particles is preferably within a range of 20 to 100 μm, and more preferably within a range of 25 to 80 μm. The volume-based median diameter of the carrier particles can be measured, for example, by a laser diffraction particle size distribution measuring device (HELOS, SYMPATEC) equipped with a wet disperser.

[0144] The carrier particles may be mixed in an appropriate amount with the toner particles. Examples of the mixing device used for the mixing include a Nauta mixer, a W-type mixer, a V-type mixer, and the like.

[0145] [3. Fixing process] In the fixing step, a first fixing member is brought into contact with the recording medium on which the toner image is formed, thereby fixing the toner image to the recording medium. The toner image is formed using the toner according to the present invention.

[0146] In the fixing process, the heated first fixing member is brought into contact with the recording medium on which the toner image is formed, thereby heating the toner image and fixing the toner image to the recording medium. The toner image before the fixing process has interfaces between toner particles remaining. If the interfaces between toner particles remain after the fixing process, this will cause internal scattering. Therefore, in order to suppress the amount of internally scattered light, it is preferable to heat the toner image sufficiently in the fixing process so that the interfaces between toner particles are as little as possible remaining. In addition, by heating the toner image sufficiently in the fixing process, the uniformity of the image surface is improved.

[0147] The first fixing member is a fixing member that is brought into contact with the recording medium. The first fixing member is, for example, a fixing belt. In the fixing step, a fixing pad or a fixing roller for pressing the fixing belt against the recording medium may be used together with the fixing belt. When the surface of the recording medium that contacts the fixing belt is the upper surface, a pressure roller for pressing the recording medium from the lower surface may be further used. In addition, in the fixing step, a heating roller for heating the fixing belt may be further used.

[0148] In the fixing step, it is preferable to use a fixing pad together with the fixing belt, which is the first fixing member. This makes it easier to heat the toner image sufficiently and further suppress the amount of internally scattered light. It also makes it easier to improve the uniformity of the image surface.

[0149] Fixing of the toner image in the fixing process may be performed in one step or in two or more steps. Fixing in two or more steps means that the toner image is heated multiple times. From the viewpoint of sufficiently heating the toner image to suppress the amount of internally scattered light, it is preferable to fix in two or more steps, that is, to heat the toner image multiple times.

[0150] When fixing is performed in two or more stages, different fixing methods may be combined, or the same fixing method may be repeated. For example, a fixing method using a fixing belt and a fixing pad may be adopted in the first stage, and a fixing method using a fixing belt and a fixing roller may be adopted in the second stage. In this case, the same fixing belt may be used in the first stage and the second stage, or different fixing belts may be used. Also, a toner image may be heated multiple times using one fixing device.

[0151] An example of a fixing device that can be used in the fixing step will be described.

[0152] (Example 1 of fixing device) 1 is a schematic diagram of a fixing device 1 including a fixing belt 10 as a first fixing member. In FIG. 1, an arrow A indicates a conveying direction of a recording medium P.

[0153] 1, a recording medium P is transported from right to left in the drawing. The fixing device 1 includes a fixing pad 11, a pressure roller 12, a heating roller 13, an oil application roller 14, and a steering roller 15 in addition to a fixing belt 10.

[0154] The fixing belt 10 is an endless, rotatable heating rotor. In the fixing device 1, the fixing belt 10 is the first fixing member that comes into contact with the recording medium P. The fixing belt 10 has thermal conductivity, heat resistance, and the like, and is a thin-walled cylindrical shape. The fixing belt 10 has a three-layer structure having, for example, a base layer, an elastic layer located on the outer periphery of the base layer, and a release layer located on the outer periphery of the elastic layer. The thickness of the base layer is, for example, 60 μm. The material of the base layer is, for example, polyimide resin. The thickness of the elastic layer is, for example, 300 μm. The material of the elastic layer is, for example, silicone rubber. The thickness of the release layer is, for example, 30 μm. The material of the release layer is, for example, PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin), which is a fluororesin. The fixing belt 10 is stretched by a fixing pad 11, a heating roller 13, and a steering roller 15.

[0155] The fixing pad 11 is in pressure contact with the pressure roller 12 via the fixing belt 10 to form a nip portion N of a predetermined width in the transport direction of the recording medium P. The fixing pad 11 is a member having a substantially rectangular cross section and elongated along the width direction of the fixing belt 10. The material of the fixing pad 11 must be heat resistant, and for example, a liquid crystal polymer (LCP) can be used.

[0156] A sliding sheet (not shown) whose surface is coated with polytetrafluoroethylene (PTFE) or the like, and a lubricant may be interposed between the fixing pad 11 and the fixing belt 10. This allows the fixing belt 10 to slide smoothly against the fixing pad 11. The lubricant is, for example, silicone oil, grease, or the like.

[0157] The sliding sheet is formed by coating the surface of a polyimide base material having a thickness of, for example, 70 μm with PTFE. The sliding sheet is disposed to improve the sliding property between the fixing pad 11 and the fixing belt 10. Instead of providing a sliding sheet, a coating that improves the sliding property may be applied to the surface layer of the fixing pad 11.

[0158] The pressure roller 12 includes, for example, an elastic layer located on the outer periphery of the shaft, and a release layer located on the outer periphery of the elastic layer. The shaft is made of, for example, stainless steel. The elastic layer is, for example, 5 mm thick. The elastic layer is, for example, made of conductive silicone rubber. The release layer is, for example, 50 μm thick. The release layer is, for example, made of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin), which is a fluororesin. The pressure roller 12 is driven to rotate.

[0159] The heating roller 13 is, for example, a stainless steel pipe having a thickness of 1 mm. A halogen heater (not shown) is disposed inside the heating roller 13. The halogen heater is capable of generating heat up to a predetermined temperature. The heating roller 13 heats the fixing belt 10. At this time, the fixing belt 10 is controlled to a predetermined target temperature based on, for example, temperature detection by a thermistor. The heating roller 13 may be configured to be driven to rotate, for example. By driving the heating roller 13 to rotate, it is possible to increase the tension of the fixing belt 10 from the nip portion N to the heating roller 13 in the rotation direction of the fixing belt 10. This makes it possible to increase the curvature of the exit of the nip portion N in the rotation direction of the fixing belt 10, thereby improving the separation performance of the recording medium P.

[0160] The oil application roller 14 is formed by impregnating a roller-shaped member wrapped with a nonwoven fabric having a thickness of, for example, 100 μm with oil. The oil is, for example, silicone oil. The oil application roller 14 is brought into contact with the fixing belt 10 by, for example, a pressure spring (not shown). The oil application roller 14 can continuously supply oil to the inner peripheral surface of the fixing belt 10. This maintains a state in which oil is present between the fixing belt 10 and the fixing pad 11, and maintains stable operation of the fixing device 1.

[0161] The steering roller 15 suspends the fixing belt 10. The steering roller 15 is supported by, for example, a steering frame (not shown). The steering frame swings about a rotation shaft as a fulcrum, causing the steering roller 15 to change its alignment with respect to the other suspension members. This generates a tension difference between the front and rear of the fixing belt 10, controlling the position of the fixing belt 10 in the width direction of the fixing belt 10. The steering roller 15 may be biased by a spring supported by the steering frame. This allows the steering roller 15 to also function as a tension roller that applies a predetermined tension to the fixing belt 10. The axial direction of the rotation shaft of the steering frame is the same as the transport direction of the recording medium P.

[0162] The fixing belt 10 is suspended by a fixing pad 11, a heating roller 13, and a steering roller 15. The fixing belt 10 is sandwiched between the fixing pad 11 and a pressure roller 12, and rotates as the pressure roller 12 rotates. The fixing belt 10 stores heat from the heating roller 13. When the recording medium P carrying the unfixed toner image T is sandwiched and conveyed between the pressure roller 12 and the fixing belt 10 at the nip portion N, the recording medium P is given the heat and pressure required for fixing. As a result, the toner image T is fixed to the recording medium P.

[0163] (Example 2 of fixing device) 2 is a schematic diagram of a fixing device 2 including a fixing belt 20 as a first fixing member. In FIG. 2, an arrow A indicates a conveying direction of a recording medium P.

[0164] 1, the recording medium P is conveyed from right to left in the drawing. In addition to the fixing belt 20, the fixing device 2 includes a fixing roller 21, a pressure roller 22, and a heating roller .

[0165] The fixing roller 21 and the pressure roller 22 cooperate to form a nip portion N for sandwiching and transporting the recording medium P carrying the toner image T.

[0166] The fixing belt 20 is an endless belt. The fixing roller 21 and the heating roller 23 are rotated while being stretched over the inner surface of the fixing belt 20.

[0167] The fixing belt 20 is a deformable endless belt having, for example, a circumference of 500 mm and a width of 340 mm. The fixing belt 20 has a multi-layer structure including, for example, a base layer, an elastic layer, and a release layer. The thickness of the base layer is, for example, 70 μm. The material of the base layer is, for example, polyimide resin. The elastic layer is laminated on the outer periphery side of the base layer. The thickness of the elastic body is, for example, 200 μm. The material of the elastic body is, for example, silicone rubber. The release layer is laminated on the elastic layer. The thickness of the release layer is, for example, 30 μm. The material of the release layer is, for example, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA).

[0168] Fixing roller 21 is a hard roller in which a protective layer is formed on a cylindrical core roller (core metal) to prevent metal wear on the surface of the core roller. The core roller is made of aluminum, for example, with an outer diameter of 60 mm, a length of 360 mm, and a thickness of 10 mm. The protective layer is, for example, 200 μm thick. The material of the protective layer is, for example, fluororesin. Fixing roller 21 is not limited to this configuration. It is sufficient that fixing roller 21 is configured such that it hardly deforms due to the pressing force from pressure roller 22 when forming nip portion N between itself and pressure roller 22.

[0169] The fixing roller 21 may or may not have a heat source. The fixing roller 21 receives a driving force from a driving motor (not shown) and rotates at a surface speed of, for example, 440 mm / s.

[0170] The elastic layer deforms the surface of the fixing belt 20 in accordance with the unevenness of the toner image T formed on the recording medium P, and supplies heat uniformly to the entire toner image T. The material, thickness, hardness, etc. of the fixing belt 20 are appropriately selected according to the device design conditions such as the purpose of use and the conditions of use.

[0171] The pressure roller 22 is, for example, a soft roller having a base body, an elastic layer located on the outer periphery of the base body, and a release layer located on the outer periphery of the elastic layer. The base body is, for example, a cylindrical roller made of aluminum with a diameter of 55 mm and a length of 360 mm. The thickness of the elastic layer is, for example, 10 mm. The material of the elastic layer is, for example, silicone rubber. The thickness of the release layer is, for example, 100 μm. The material of the release layer is, for example, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA).

[0172] The pressure roller 22 is disposed so as to be pressed against the fixing roller 21, and rotates following the fixing roller 21. The surface speed of the rotation of the pressure roller 22 is, for example, the same as the surface speed of the fixing roller 21. The pressure roller 22 may or may not have a heating source.

[0173] Heating roller 23 is a cylindrical roller made of aluminum, for example, with an outer diameter of 100 mm, a thickness of 2 mm, and a length of 360 mm. Heating roller 23 has an internal heat source (not shown). The heat source is, for example, a halogen heater rated at 1200 W. Therefore, heating roller 23 has a function of stretching fixing belt 20 and a function of heating fixing belt 20 from the inner peripheral surface side.

[0174] Springs (not shown) for pressing the fixing belt 20 outward may be disposed at both ends of the heating roller 23 in the longitudinal direction. This allows the heating roller 23 to adjust the tension of the fixing belt 20 to a predetermined value (e.g., 15 kgf). Furthermore, the heating roller 23 is provided with a belt deviation control mechanism (not shown). That is, the heating roller 23 also functions as a steering roller for correcting deviation of the fixing belt 20.

[0175] (Example 3 of fixing device) 3 is a schematic diagram of a fixing device 3 including a fixing roller 30 as a first fixing member. In FIG. 3, an arrow A indicates the conveying direction of a recording medium P.

[0176] 3, the recording medium P is transported from right to left in the figure. In addition to the fixing roller 30, the fixing device 3 includes an external heating belt 31, an external heating roller 32, a fixing pad 33, and a fixing belt .

[0177] The fixing roller 30 is heated by an external heating belt 31 that is heated by an external heating roller 32. The fixing roller 30 forms a nip portion N together with a fixing pad 33 via a fixing belt 34. When the recording medium P on which the toner image T is formed passes through the nip portion N, the toner image T is heated and the toner image T is fixed to the recording medium P.

[0178] (Example 4 of fixing device) 4 is a schematic diagram of a fixing device 4 including a fixing belt 40 as a first fixing member. In FIG. 4, an arrow A indicates the conveying direction of a recording medium P.

[0179] 4, the recording medium P is transported from right to left in the drawing. In addition to the fixing belt 40, the fixing device 4 includes a fixing roller 41, an upper heating roller 42, a pressure belt 43, a pressure roller 44, and a lower heating roller 45.

[0180] The fixing belt 40 is heated by the upper heating roller 42. The pressure belt 43 is heated by the lower heating roller 45. The fixing roller 41 and the pressure roller 44 form a nip portion N via the fixing belt 40 and the pressure belt 43. When the recording medium P on which the toner image T has been formed passes through the nip portion N, the toner image T is heated and the toner image T is fixed to the recording medium P.

[0181] [4. Cooling process] In the cooling step, the recording medium separated from the first fixing member is cooled. That is, in the image forming method of the present invention, the first fixing member and the recording medium are separated between the fixing step and the cooling step. By cooling the recording medium after it is separated from the first fixing member, the toner image can be efficiently cooled with little residual heat. Therefore, the mechanism for cooling the recording medium separated from the first fixing member has a high image cooling speed.

[0182] In the cooling step, the recording medium is cooled by contacting the first cooling member with the recording medium. At this time, it is preferable to bring the first cooling member into contact with a portion of the recording medium where the toner image is fixed, thereby cooling the toner image. The first cooling member is a cooling member that is brought into contact with the recording medium. The first cooling member is, for example, a cooling belt. The mechanism that brings the first cooling member into contact with the recording medium has high thermal conduction efficiency and a high image cooling speed.

[0183] A high image cooling rate is effective in reducing the crystal growth rate and keeping the size of the crystallized crystalline polyester domain small. The small size of the crystalline polyester domain suppresses the amount of internally scattered light and expands the color gamut. Therefore, the present invention having the above-mentioned cooling process with a high image cooling rate can form an image with a wide color gamut.

[0184] In the cooling step, it is preferable to further use a second cooling member that holds the recording medium together with the first cooling member. By holding the recording medium between the first cooling member and the second cooling member that are in contact with the recording medium, the image cooling speed can be increased.

[0185] The cooling of the recording medium is in the following order: (1) is the best, (5) is the worst. (1) The recording medium is cooled by bringing cooling members into contact with both sides of the recording medium. (2) The recording medium is cooled by contacting a cooling member on one side of the recording medium, for example, by a cooling device having a heat sink on a lower conveyor belt, which cools the recording medium by contacting one side of the recording medium. (3) Cool the recording medium in a non-contact manner using a cooling fan or the like. (4) The recording medium is not cooled.

[0186] An example of a cooling device that can be used in the cooling step will be described.

[0187] (Example of cooling device 1) 5 is a schematic diagram of a cooling device 5 including a first belt 510 as a first cooling member and a second belt 520 as a second cooling member. In FIG. 5, an arrow A indicates the conveying direction of a recording medium P.

[0188] The cooling device 5 is a cooling device of a belt cooling type. The cooling device 5 includes a first unit 51 and a second unit 52. The first unit 51 includes an endless first belt 510, first belt tension rollers 511a to 511d, and a heat sink 53. The second unit 52 includes an endless second belt 520, second belt tension rollers 521a to 521d, and pressure rollers 521e and 521f. The first belt 510 and the second belt 520 are endless film-like belts formed, for example, from a high-strength polyimide resin.

[0189] The first belt 510 is stretched over a plurality of first belt stretching rollers 511a to 511d. At least one of the first belt stretching rollers 511a to 511d is rotated by a drive motor (not shown). For example, the first belt stretching roller 511d is rotated by the drive motor, thereby moving the first belt 510. The first belt stretching roller 511d as a drive roller has, for example, a rubber layer with a thickness of 1 mm on its surface, and is formed to have an outer diameter of φ40 mm.

[0190] The first belt tension roller 511b is provided so as to be in contact with the inner peripheral surface of the first belt 510 and tension the first belt 510 together with the first belt tension roller 511c. The first belt tension roller 511b is a steering roller that controls the deviation of the first belt 510 in the width direction (the direction of the rotation axis of the first belt tension roller 511c). The first belt tension roller 511b has a rubber layer with a thickness of 1 mm on its surface, for example. The first belt tension roller 511b controls the meandering of the first belt 510 by performing steering control to turn a steering angle with respect to the first belt tension roller 511c.

[0191] The second belt 520 is stretched over a plurality of second belt stretching rollers 521a to 521d and abuts against the outer circumferential surface of the first belt 510. The first belt 510 and the second belt 520 abut against each other to form a nip portion for cooling the recording medium P on which the toner image T is fixed while pinching and conveying it. The second belt stretching roller 521d is connected to a drive motor (not shown) that drives the first belt stretching roller 511d via a drive gear. The second belt stretching roller 521d is rotated by the rotational driving force of the drive motor. Thus, the second belt 520 rotates together with the first belt 510. The second belt stretching roller 521b is a steering roller that controls the shift in the width direction of the second belt 520. The second belt stretching roller 521b performs a steering operation of turning a steering angle with respect to the second belt stretching roller 521c with the center of rotation in the width direction as the center, thereby controlling the meandering of the second belt 520.

[0192] A plurality of pressure rollers 521e, 521f are provided on the inner side of the second belt 520. The plurality of pressure rollers 521e, 521f pressurize the second belt 520 toward the heat sink 53 disposed on the inner side of the first belt 510. The pressure rollers 521e, 521f pressurize the second belt 520 with a pressure of, for example, 4.9 N (0.5 kgf). As a result, the pressure rollers 521e, 521f more reliably bring the first belt 510 into contact with the heat sink 53 via the second belt 520.

[0193] The recording medium P on which the toner image T is fixed is sandwiched between the first belt 510 and the second belt 520 and is transported according to the rotation of these belts. At that time, the recording medium P passes through a nip portion formed by the contact between the first belt 510 and the second belt 520. Then, the first belt 510 forming the nip portion is cooled by the heat sink 53. The heat sink 53 contacts the inner circumferential surface of the first belt 510 at a portion forming the nip portion in order to efficiently cool the recording medium P. When passing through the nip portion, the temperature of the recording medium P is lowered via the first belt 510 cooled by the heat sink 53.

[0194] The heat sink 53 is a heat dissipation plate made of a metal such as aluminum. The heat sink 53 includes a heat absorption portion 53a, a heat dissipation portion 53b, and a fin base 53c. The heat absorption portion 53a is a cooling surface (heat absorption surface) that comes into contact with the first belt 510 and removes heat from the first belt 510 to cool it. The heat dissipation portion 53b dissipates the heat. The fin base 53c conducts the heat from the heat absorption portion 53a to the heat dissipation portion 53b.

[0195] Heat dissipation section 53b is formed of multiple heat dissipation fins to promote efficient heat dissipation by increasing the contact area with the air taken in from the outside by cooling fan 54. For example, the heat dissipation fins have a thickness of 1 mm, a height of 100 mm, and a pitch of 5 mm. The thickness of fin base 53c is, for example, 10 mm.

[0196] Here, an example in which both the first belt 510 and the second belt 520 are driven is shown, but the driving method is not limited to this. For example, only the first belt 510 may be driven so that the second belt 520 is driven by the first belt 510. Also, only the second belt 520 may be driven so that the first belt 510 is driven by the second belt 520. Also, a roller may be used instead of the second belt 520, and may be brought into contact with the first belt 510 to form a nip portion.

[0197] (Cooling device example 2) 6 is a schematic diagram of a cooling device 6 including a heat absorbing belt 610 as a first cooling member and a pressing belt 620 as a second cooling member. In FIG. 6, an arrow A indicates the conveying direction of a recording medium P.

[0198] The cooling device 6 includes a heat absorbing device 61 and a pressing device 62. The heat absorbing device 61 absorbs heat from the recording medium P and the toner image T. The pressing device 62 presses the recording medium P against the heat absorbing device 61. The heat absorbing device 61 is disposed above the pressing device 62.

[0199] The heat absorption device 61 includes a heat absorption belt 610 , a drive roller 611 , a plurality of winding rollers 612 , a steering roller 613 , an upper adjustment mechanism 614 , a heat sink 615 , and a plurality of fans 616 .

[0200] The heat absorbing belt 610 is annular, and comes into contact with the recording medium P to absorb heat from the recording medium P. The driving roller 611 transmits a driving force to the heat absorbing belt 610. The steering roller 613 corrects meandering of the heat absorbing belt 610. The heat absorbing belt 610 is wound around the driving roller 611, a plurality of winding rollers 612, and the steering roller 613.

[0201] The upper adjustment mechanism 614 tilts the steering roller 613 with respect to the belt width direction. The upper adjustment mechanism 614 includes a swing arm 614a, an eccentric cam 614b, and an upper steering drive unit (not shown). The eccentric cam 614b is rotationally driven by the upper steering drive unit (not shown). The upper steering drive unit rotates the eccentric cam 614b to swing one end of the swing arm 614a. As a result, the steering roller 613 provided on the other end of the swing arm 614a is tilted with respect to the width direction of the heat absorption belt 610. For example, when the heat absorption belt 610 meanders, the meandering of the heat absorption belt 610 is corrected by tilting the steering roller 613 as described above.

[0202] The heat sink 615 is provided on the inner circumferential side of the heat absorption belt 610. Although there is a gap between the heat sink 615 and the heat absorption belt 610 in Fig. 2, the heat sink 615 is configured to contact the inner circumferential surface of the heat absorption belt 610. In this way, the heat sink 615 dissipates the heat absorbed by the heat absorption belt 610. The heat sink 615 is formed of, for example, an aluminum material.

[0203] The fan 616 is disposed on the rear side of the heat sink 615. The fan 616 removes heat from the heat sink 615 and expels the hot air to the outside.

[0204] The pressing device 62 includes a pressing belt 620 , a plurality of winding rollers 621 , a steering roller 622 , and a lower adjustment mechanism 623 .

[0205] The pressing belt 620 is circular and conveys the recording medium P while pressing the recording medium P against the heat absorbing belt 610. The steering roller 622 corrects the meandering of the pressing belt 620. The pressing belt 620 is wound around a plurality of winding rollers 621 and a steering roller 622.

[0206] The lower adjustment mechanism 623 tilts the pressing belt 620 with respect to the belt width direction. The lower adjustment mechanism 623 includes a swing arm 623a, an eccentric cam 623b, and a lower steering drive unit (not shown). The eccentric cam 623b is rotationally driven by the lower steering drive unit (not shown). The lower steering drive unit 24 rotates the eccentric cam 623b to swing one end of the swing arm 623a. As a result, the steering roller 622 provided on the other end of the swing arm 623a is tilted with respect to the width direction of the pressing belt 620. For example, when meandering of the pressing belt 620 occurs, the meandering of the pressing belt 620 is corrected by tilting the steering roller 622 as described above.

[0207] An example of the operation of the cooling device 6 will be described. First, the heat absorbing belt 610 rotates by being driven by the driving roller 611, and the pressing belt 620 rotates with the rotation of the heat absorbing belt 610. At this time, the heat absorbing belt 610 moves while its inner circumferential surface is in contact with the heat sink 615. The pressing belt 620 moves while its outer circumferential surface is in contact with the outer circumferential surface of the heat absorbing belt 610. At this time, the fan 616 also operates. Next, the recording medium P on which the toner image T is formed is introduced from the inlet portion where the heat absorbing belt 610 and the pressing belt 620 start to come into contact with each other. The introduced recording medium P is conveyed while being sandwiched between the heat absorbing belt 610 and the pressing belt 620 which are rotating and moving. At this time, the heat of the conveyed recording medium P is absorbed by the heat sink 615 through the heat absorbing belt 610, and the recording medium P is cooled. Then, the recording medium P is discharged to the outside of the cooling device 6 from the outlet portion where the heat absorbing belt 610 and the pressing belt 620 start to separate from each other.

[0208] (Cooling device example 3) Fig. 7A is a schematic diagram of a cooling device 7 including an upper conveyor belt 710 as a first cooling member and a lower conveyor belt 720 as a second cooling member. Fig. 7B is a diagram of the cooling device 7 as seen from above. In Figs. 7A and 7B, an arrow A indicates the conveying direction of a recording medium P.

[0209] The cooling device 7 includes an upper transport unit 71 and a lower transport unit 72 .

[0210] The upper conveying unit 71 includes an upper conveying belt 710 , a driving roller 711 , driven rollers 712 , 713 , 714 , and 715 , a cooling plate 731 , heat dissipation fins 732 , and a cooling pipe 733 .

[0211] The lower conveying unit 72 is disposed opposite to the upper conveying unit 71. The lower conveying unit 72 includes a lower conveying belt 720, four opposing rollers 721, four pressure members 722, a driving roller 723, and a driven roller 724.

[0212] As shown in FIG. 7B, the cooling device 7 further includes a liquid reservoir tank 734, a pump 735, a radiator 736, and a fan 737.

[0213] The lower conveyor belt 720 conveys the recording medium P by sandwiching it with the upper conveyor belt 710. The opposing roller 721 is provided inside the lower conveyor belt 720 and between the driving roller 723 and the driven roller 724. The opposing roller 721 is urged upward by a pressure member 722 provided below the opposing roller 721, and presses the lower conveyor belt 720 against the upper conveyor belt 710. Each of the four opposing rollers 721 faces the cooling pipe 733 in the vertical direction via the upper conveyor belt 710 and the lower conveyor belt 720. The opposing roller 721 is in contact with the inner circumferential surface of the lower conveyor belt 720. The opposing roller 721 presses the conveyed recording medium P against the vicinity of the cooling pipe 733 of the cooling plate 731. This allows the cooling device 7 to efficiently cool the recording medium P.

[0214] The cooling plate 731 is a member formed of a metal having high thermal conductivity. The heat receiving surface of the cooling plate 731 that comes into contact with the upper conveyor belt 710 is flat. The cooling plate 731 is provided inside the upper conveyor belt 710 and between the driving roller 711 and the driven roller 715. The cooling plate 731 is provided in contact with the inner circumference of the upper conveyor belt 710. The cooling plate 731 extends to the vicinity of the driving roller 711 and the driven roller 715, so that the recording medium P can be efficiently cooled. The cooling plate 731 is provided with four fitting portions that fit with the cooling pipes 733. The fitting portions are formed on a horizontal plane in a direction perpendicular to the conveying direction of the recording medium P.

[0215] The heat dissipation fins 732 are provided on the cooling plate 731. Specifically, four heat dissipation fins 732 are provided at intervals between the cooling pipes 733. The heat dissipation fins 732 are formed in a direction perpendicular to the transport direction of the recording medium P on a horizontal plane. Between each of the heat dissipation fins 732, an air passage is formed through which air flows along the heat dissipation fins 732. When the cooling plate 731 receives heat from the recording medium P in the region between the adjacent cooling pipes 733, not only is the heat taken away by the cooling pipes 733, but the heat dissipation fins 732 also release heat. This allows the cooling device 7 to efficiently cool the recording medium P.

[0216] The cooling pipe 733, the liquid reservoir tank 734, the pump 735, and the radiator 736 are connected via piping. These constitute a flow path for the cooling medium.

[0217] The cooling pipe 733 is a tubular member made of a metal with high thermal conductivity. The cooling pipe 733 forms a flow path for the cooling medium in a direction intersecting the transport direction of the recording medium P. The cooling medium is mainly composed of water, for example. The cooling medium may contain propylene glycol or ethylene glycol for lowering the freezing temperature, or a rust inhibitor for preventing rust on metal parts.

[0218] The liquid reservoir tank 734 is a tank that contains the cooling medium that has passed through the cooling pipe 733 .

[0219] The pump 735 supplies the cooling medium from the liquid storage tank 734 to the radiator 736. As a result, the cooling medium supplied to the cooling pipe 733 flows from the downstream side to the upstream side in the transport direction of the recording medium P. The driving of the pump 735 is controlled by a control unit (not shown).

[0220] The liquid reservoir tank 734 and the pump 735 are provided at positions where they are not affected by the heat exhausted by the fan 737. This improves the cooling efficiency.

[0221] The radiator 736 is a heat dissipation unit that dissipates heat from the cooling medium. The radiator 736 has fins (not shown) in the flow path. The cooling medium in the flow path is cooled by the air flow passing between the fins.

[0222] Fan 737 draws in outside air from an opening and guides it to radiator 736. Fan 737 is disposed downstream of radiator 736 in the air blowing direction, and rotates to draw airflow from radiator 736. This causes the airflow to pass through radiator 736. The number of fans 737 is not particularly limited.

[0223] The operation of the cooling device 7 will be described. First, the upper conveyor belt 710 and the lower conveyor belt 720 are brought into close proximity to each other. In this state, when the driving roller 711 is rotated, the upper conveyor belt 710 and the lower conveyor belt 720 rotate. The recording medium P is conveyed in the direction of the arrow A by the rotation of the upper conveyor belt 710 and the lower conveyor belt 720. In this state, the pump 735 is driven to circulate the cooling medium in the cooling pipe 733. At this time, the inner surface of the upper conveyor belt 710 slides on the heat absorbing surface of the cooling plate 731. As a result, the cooling plate 731 absorbs heat from the recording medium P through the upper conveyor belt 710. The cooling plate 731 is kept at a low temperature by the cooling medium transporting the heat absorbed by the cooling plate 731 to the outside. The heat absorbed by the cooling medium is dissipated to the outside air by the cooling medium passing through the radiator 736. As a result, the temperature of the cooling medium decreases. The cooling medium, now at a low temperature, flows again through the cooling pipe 733 and absorbs heat from the recording medium P. By repeating this cycle, the recording medium P is cooled.

[0224] A modified example of the cooling device 7 will be described. The cooling device 7 may include three opposed rollers opposed to three heat dissipation fins 732, in addition to the four opposed rollers 721 opposed to the cooling pipe 733. This increases the adhesion between the cooling plate 731 and the recording medium P, improving the cooling efficiency of the recording medium P.

[0225] In the cooling device 7, the lower conveying unit 72, rather than the upper conveying unit 71, may include the cooling plate 731, the heat dissipation fins 732, and the cooling pipe 733. In this case, the upper conveying unit 71 includes the opposing roller 721 and the pressure member 722.

[0226] In the cooling device 7, both the upper conveying unit 71 and the lower conveying unit 72 may include a cooling plate 731, heat dissipation fins 732, and a cooling pipe 733. As a result, the cooling plates 731 are located above and below the recording medium P, thereby improving the cooling efficiency of the recording medium P.

[0227] In the cooling device 7, the flow passage is not limited to the cooling pipe 733. The flow passage may be, for example, a flow passage formed in the cooling plate 731 by cutting.

[0228] [5. Image forming system] The image forming system of the present invention has at least a fixing unit and a cooling unit. The fixing unit is a fixing device that performs the above-mentioned fixing step. The cooling unit is a cooling device that performs the above-mentioned cooling step. The image forming system of the present invention uses the above-mentioned toner according to the present invention.

[0229] The image forming system of the present invention may also include other means, such as a toner image forming means for forming an unfixed toner image. EXAMPLES

[0230] The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. In the following examples, unless otherwise specified, the operations were performed at room temperature (25°C). In the following examples, unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass", respectively.

[0231] <Synthesis of amorphous polyesters A1 to A12> The following materials were placed in a reaction vessel equipped with a condenser, a stirrer, a nitrogen inlet tube, and a thermocouple. Bisphenol A ethylene oxide adduct 0.6 mol parts Bisphenol A propylene oxide adduct 29.4 mol parts Ethylene glycol 47.0 mol parts Propanediol 23.0 mol parts Terephthalic acid 82.8 mole parts Trimellitic acid 17.2 mol parts

[0232] The reaction vessel was further charged with 0.5 parts by mass (1.23 millimoles) of tin 2-ethylhexanoate as an esterification catalyst. The reaction vessel was replaced with nitrogen gas. The temperature in the reaction vessel was gradually increased while stirring. The reaction vessel was stirred at a temperature of 140°C and reacted for 3 hours. The pressure in the reaction vessel was then reduced to 8.3 kPa, and the temperature was increased to 200°C while stirring, and the reaction was carried out for 4 hours. The pressure in the reaction vessel was then reduced to 5 kPa or less, and the reaction was carried out at 200°C for 3 hours. As a result, amorphous polyester A1 was obtained.

[0233] Amorphous polyesters A2 to A12 were each synthesized in the same manner as for the synthesis of amorphous polyester A1, except that the alcohol component was changed as shown in Table I.

[0234] In Table I, "BPA-EO" stands for bisphenol A ethylene oxide adduct, and "BPA-PO" stands for bisphenol A propylene oxide adduct.

[0235] [Table 1]

[0236] In the amorphous polyesters A1 to A12, the content of structural units derived from bisphenol A derivatives relative to 100 mol % of all structural units derived from polyhydric alcohols (BPAD content in APEs) is as shown in Table I.

[0237] <Synthesis of crystalline polyesters C1 to C6> The following materials were placed in a reaction vessel equipped with a condenser, a stirrer, a nitrogen inlet tube, and a thermocouple. 1,6-Hexanediol 60.0 mol parts Adipic acid 40.0 mol parts

[0238] The reactor was further charged with 0.5 parts by mass (1.23 millimoles) of tin 2-ethylhexanoate as an esterification catalyst. The atmosphere in the reactor was replaced with nitrogen gas. The temperature in the reactor was gradually increased while stirring. The reactor was reacted for 3 hours while stirring at a temperature of 140°C. The pressure in the reactor was then reduced to 8.3 kPa, and the temperature was increased to 200°C while stirring, and the reaction was continued for 1 hour. As a result, amorphous polyester A1 was obtained.

[0239] Crystalline polyesters C2 to C6 were each synthesized in the same manner as for crystalline polyester C1, except that the types of the aliphatic polyhydric alcohol component and the aliphatic polycarboxylic acid component were changed as shown in Table II.

[0240] [Table 2]

[0241] <Preparation of Cyan Toners 1 to 19> The following materials were mixed using a Henschel mixer (FM-75 type, manufactured by Mitsui Mining Co., Ltd.) at a rotation speed of 20 s-1 for a rotation time of 5 min. Amorphous polyester A1 100 parts by weight Crystalline polyester C1 5 parts by weight Hydrocarbon wax (melting point: 90°C) 6 parts by weight Cyan colorant (CI Pigment Blue 15:3) 7 parts by weight

[0242] The obtained mixture was kneaded in a twin-screw kneader (PCM-30, manufactured by Ikegai Corporation) set at a temperature of 150°C. The obtained kneaded product was cooled and coarsely crushed to 1 mm or less using a hammer mill to obtain a coarsely crushed product. The obtained coarsely crushed product was finely crushed using a mechanical crusher (T-250, manufactured by Turbo Kogyo Co., Ltd.). The obtained finely crushed product was classified using a zigzag classifier.

[0243] The particles that had been subjected to classification were subjected to heat treatment using a surface treatment device, with the temperature of the heat treatment chamber set to 150° C. and the treatment time set to 30 seconds, thereby obtaining cyan toner base particles 1 with a circularity of 0.96.

[0244] The following materials were mixed in a Henschel mixer (FM-75, manufactured by Mitsui Miike Chemical Engineering Co., Ltd.) at a rotation speed of 30 s. -1 The mixture was mixed with a rotation time of 10 min. Cyan toner base particles 1 100.0 parts by mass Hydrophobic silica fine particles 1.0 parts by weight Titanium oxide fine particles 1.0 parts by mass Strontium titanate 0.5 parts by mass

[0245] The hydrophobic silica particles are hydrophobic silica particles that have been hydrophobized with hexamethyldisilazane. The BET specific surface area of ​​the hydrophobic silica particles is 200 m 2 The titanium oxide particles are surface-treated with isobutyltrimethoxysilane. The BET specific surface area of ​​the titanium oxide particles is 80 m 2 / g.

[0246] From the resulting mixture, coarse particles were removed using a sieve with 45 μm openings, thereby obtaining cyan toner 1.

[0247] Cyan toners 2 to 19 were each prepared in the same manner as for cyan toner 1, except that the amorphous polyester and crystalline polyester were changed as shown in Table III.

[0248] [Table 3]

[0249] <Preparation of Magenta Toners 1 to 19> Magenta toners 1 to 19 were prepared in the same manner as for the preparation of cyan toners 1 to 19, except that the colorant was changed to a magenta colorant (CI Pigment Red 57:1) (12 parts by mass).

[0250] <Preparation of Yellow Toners 1 to 19> Yellow toners 1 to 19 were prepared in the same manner as for cyan toners 1 to 19, except that the colorant was changed to a yellow colorant (CI Pigment Yellow 180) (6 parts by mass).

[0251] <Preparation of Black Toner 1-19> Black toners 1 to 19 were prepared in the same manner as cyan toners 1 to 19, except that the colorant was changed to a black colorant (carbon black) (8 parts by mass).

[0252] <Preparation of developer> The various toners thus prepared were mixed with ferrite carriers coated with acrylic resin and having a volume average particle size of 36 μm so that the toner particle concentration was 6% by mass. In this way, various two-component developers containing various toners were prepared.

[0253] <Color gamut evaluation> A multifunction printer (Konica Minolta, bizhub PRESS C1070) was modified so that an image (unfixed image) could be collected before the fixing process. The modified printer was used as an unfixed image forming device. POD Gloss Coat 128 (Oji Paper, 128 g / m 2 ) was used. A developer was loaded into the unfixed image forming apparatus. An unfixed image was formed in the default mode using the unfixed image forming apparatus. The unfixed image was an image including each of the color regions of yellow (Y), magenta (M), cyan (C), red (R), blue (B), and green (G). The pixel rate of each color region was 100%. The area of ​​each color region was 2 cm x 2 cm.

[0254] The fixing and cooling steps were carried out using the fixing devices A to C, the cooling devices D and E, and the fixing-cooling device F in the combinations shown in Table IV. Details of each device are as follows.

[0255] (Fuser A) Fixing device A is a fixing device taken from an imagePRESS V1000 (manufactured by Canon Inc.) that has been modified so that it can be driven independently. Fixing device A has the same configuration as fixing device 1 shown in Figure 1. Fixing device A forms a fixing nip with a non-rotating pressure pad.

[0256] (Fuser B) Fixing device B is a fixing device taken from a bizhub PRESS C8000 (manufactured by Konica Minolta) that has been modified so that it can be driven by itself. Fixing device B is a combination of two fixing devices, and performs fixing in two stages. The first stage fixing device has the same configuration as fixing device 3 shown in FIG. 3. The second stage fixing device has the same configuration as fixing device 4 shown in FIG. 4.

[0257] (Fixing device C) The fixing device C has the same configuration as the fixing device 2 shown in FIG.

[0258] (Cooling device D) Cooling device D is a cooling device taken from an imagePRESS V1000 (manufactured by Canon Inc.) that has been modified so that it can be driven independently. Cooling device D has the same configuration as cooling device 5 shown in Fig. 5. Cooling device D cools the recording medium by a contact method.

[0259] (Cooling device E) Cooling device E is a cooling device taken from a bizhub PRO C6500 (manufactured by Konica Minolta) that has been modified so that it can operate independently. Cooling device E cools the recording medium using a non-contact method.

[0260] (Fixing-cooling unit F) The fixing-cooling device F has the same configuration as the fixing-cooling device 8 shown in Fig. 8. The fixing-cooling device 8 includes a fixing-cooling belt 81, a fixing roller 82, a pressure roller 83, winding rollers 84 and 85, and a cooling section 86. The fixing-cooling belt 81 serves both as a fixing belt and a cooling belt. The recording medium P and the fixing-cooling belt 81 are not separated between the fixing step and the cooling step, but in the vicinity of the winding roller 84. The cooling section 86 cools the recording medium P by a contact method.

[0261] The fixing temperature was 165° C. in the fixing process using any of the fixing devices.

[0262] The color gamut of the image after cooling, consisting of Y / M / C / R / G / B, is called a * -b * The area was measured as the color gamut area. The color gamut area of ​​the image of Comparative Example 1 was set to 100, and the color gamut of each image was evaluated as a relative value. The measurement device used was a fluorescent spectrodensitometer FD-7 (manufactured by Konica Minolta). The measurement conditions were as follows:

[0263] (Measurement conditions) Light source: D50 light source Field of view: 2° Concentration: ANSI T White standard: ABS Filter:UV Cut Measurement mode: Reflectance Language:Japanese

[0264] Based on the relative value of the color gamut, the color gamut was evaluated according to the following criteria, with A and B being pass levels. The evaluation results are shown in Table IV. A: The relative value of the color gamut is 111 or more. (A level that can be judged as a very vivid image.) B: The relative value of the color gamut is 101 to 110. (A level that feels beautiful compared to conventional images) C: The relative value of the color gamut is below 100. (The same level as a conventional image or lower)

[0265] <Low temperature fixability evaluation> A4 size high-quality paper (NPI high-quality, 127.9 g / m 2 A 100 mm x 100 mm unfixed image was formed in an environment of normal temperature and humidity (temperature 20°C, humidity 50% RH) using the same unfixed image forming device as that used for the color gamut evaluation. The developer used contained cyan toner. The set value for the amount of cyan toner adhesion was 11.3 g / m 2 It was decided.

[0266] A fixing test was performed on the unfixed image using the same fixing device as in the color gamut evaluation. The fixing test was repeatedly performed by changing the fixing temperature from 110°C to 180°C in 1°C increments. In the fixing test, the recording medium was not cooled using a cooling device, but was cooled at room temperature.

[0267] The lowest fixing temperature at which image staining due to fixing offset was not visually confirmed was defined as the minimum fixing temperature (UO avoidance temperature). Based on the minimum fixing temperature, the low-temperature fixing ability was evaluated according to the following criteria. A, B, and C are acceptable levels. The evaluation results are shown in Table IV. A: The minimum fixing temperature is less than 130°C. B: The minimum fixing temperature is 130°C or higher and lower than 135°C. C: The minimum fixing temperature is 135°C or higher and lower than 140°C. D: The minimum fixing temperature is 140° C. or higher.

[0268] <Evaluation of toner heat resistance> The heat resistance of the prepared cyan toner was evaluated by the following method. 0.5 g of toner particles were placed in a 10 mL glass bottle with an inner diameter of 21 mm, the lid was closed, and the bottle was shaken 600 times at room temperature using a shaker. The shaker was a Tap Denser KYT-2000 (manufactured by Seishin Enterprise Co., Ltd.). After that, the glass bottle was left for 2 hours in an environment with a temperature of 55°C and a humidity of 35% RH with the lid open. Next, the toner particles were transferred from the glass bottle onto a 48 mesh (opening 350 μm) sieve while being careful not to break up the toner aggregates. This was set in a powder tester (manufactured by Hosokawa Micron Co., Ltd.) and fixed with a pressing bar and a knob nut. The vibration intensity was adjusted to a feed width of 1 mm, and vibration was applied for 10 seconds, after which the ratio [mass %] of the toner amount remaining on the sieve was measured. The toner aggregation rate was calculated by the following formula (A).

[0269] Formula (A): Toner cohesion rate [%] = (mass of toner remaining on sieve [g] / 0.5g) x 100

[0270] Similar measurements were performed at temperatures of 57.5°C, 60.0°C, and 62.5°C. A plot was created with temperature on the X-axis and toner cohesion rate on the Y-axis. An approximate straight line was drawn between two temperatures between which the toner cohesion rate of 50% was sandwiched among the temperatures of 55°C, 57.5°C, 60.0°C, and 62.5°C. The temperature at which the toner cohesion rate was 50% (hereinafter also referred to as the "50% cohesion temperature") was calculated by interpolation.

[0271] The heat resistance of the toner was evaluated based on the 50% coagulation temperature according to the following criteria, with A, B and C being acceptable levels. The evaluation results are shown in Table IV.

[0272] A: The 50% coagulation temperature is 59°C or higher. B: The 50% coagulation temperature is 58°C or higher and lower than 59°C. C: The 50% coagulation temperature is 57°C or higher and lower than 58°C. D: The 50% coagulation temperature is less than 57°C.

[0273] [Table 4]

[0274] From the above results, it can be confirmed that the image forming method of the present invention provides a toner for developing an electrostatic image with high low-temperature fixability and can form an image with a wide color gamut. [Explanation of symbols]

[0275] 1 Fixing device 10 Fixing belt 11 Fixing pad 12 Pressure roller 13 Heating roller 14 Oil application roller 15 Steering roller 2 Fixing device 20 Fixing belt 21 Fixing roller 22 Pressure roller 23 Heating roller 3 Fixing device 30 Fixing roller 31 External heating belt 32 External heating roller 33 Fixing Pad 34 Fixing belt 4 Fixing device 40 Fixing belt 41 Fixing roller 42 Upper heating roller 43 Pressure Belt 44 Pressure Roller 45 Lower Heating Roller 5 Cooling device 51 First Unit 510 First Belt 511a~511d First belt tension roller 53 Heat sink 53a Heat absorption part 53b Heat dissipation part 53c fin base 52 Second Unit 520 Second Belt 521a~521d Second belt tension roller 521e, 521f Pressure roller 6 Cooling device 61 Heat sink 610 Heat absorbing belt 611 Drive roller 612 Winding roller 613 Steering roller 614 Upper adjustment mechanism 614a Swing arm 614b Eccentric Cam 615 Heatsink 616 Fans 62 Pressing device 620 Pressing Belt 621 Winding roller 622 Steering roller 623 Lower adjustment mechanism 623a Swing Arm 623b Eccentric Cam 7 Cooling device 71 Upper transport unit 710 Upper conveyor belt 711 Drive roller 712~715 Driven roller 731 Cooling plate 732 Heat dissipation fin 733 Cooling pipe 734 Liquid storage tank 735 Pump 736 Radiator 737 Fan 72 Lower transport unit 720 Lower conveyor belt 721 Opposing Roller 722 Pressure Member 723 Drive Roller 724 Driven Roller T Toner Image P Recording medium N Nip section

Claims

1. An image forming method using a toner for developing an electrostatic image, the toner comprising toner particles, the toner particles contain an amorphous polyester and a crystalline polyester, the content of structural units derived from bisphenol A derivatives relative to 100 mol % of all structural units derived from polyhydric alcohols in the amorphous polyester is 30 mol % or less; a fixing step of fixing the toner image on the recording medium by contacting a first fixing member with the recording medium on which the toner image containing the electrostatic image developing toner is formed; a cooling step of contacting a first cooling member with the recording medium separated from the first fixing member to cool the recording medium, 1. An image forming method comprising:

2. the content of structural units derived from bisphenol A derivatives relative to 100 mol % of all structural units derived from polyhydric alcohols in the amorphous polyester is 10 mol % or less; 2. The image forming method according to claim 1.

3. the first fixing member is a fixing belt, In the fixing step, a fixing pad is further used.

3. The image forming method according to claim 1 or 2.

4. In the fixing step, fixing is performed in one step.

4. The image forming method according to claim 3.

5. In the fixing step, the toner image is heated multiple times.

4. The image forming method according to claim 3.

6. The amorphous polyester has a structural unit derived from an aliphatic polyhydric alcohol having 3 to 6 carbon atoms.

3. The image forming method according to claim 1 or 2.

7. the crystalline polyester has a structural unit derived from an aliphatic polyhydric alcohol having 6 to 12 carbon atoms and a structural unit derived from an aliphatic polycarboxylic acid having 6 to 12 carbon atoms; 3. The image forming method according to claim 1 or 2.

8. In the cooling step, a second cooling member is further used to hold the recording medium together with the first cooling member.

3. The image forming method according to claim 1 or 2.

9. An image forming system using a toner for developing an electrostatic image, the toner comprising toner particles, the toner particles contain an amorphous polyester and a crystalline polyester, the content of structural units derived from bisphenol A derivatives relative to 100 mol % of all structural units derived from polyhydric alcohols in the amorphous polyester is 30 mol % or less; a fixing unit that brings a first fixing member into contact with a recording medium on which a toner image containing the electrostatic image developing toner is formed, thereby fixing the toner image onto the recording medium; a cooling unit that brings a first cooling member into contact with the recording medium separated from the first fixing member to cool the recording medium, 1. An image forming system comprising:

Images