Image forming apparatus and image forming method

Abstract

To provide an image forming apparatus that maintains low temperature fixability of toner.SOLUTION: An image forming apparatus is for forming an image by using toner for electrostatic charge image development, and has: a developing unit that stores the toner for electrostatic charge image development for developing an electrostatic latent image formed on the surface of an electrophotographic photoreceptor to form a toner image; and a cooling unit for cooling the toner for electrostatic charge image development. The toner for electrostatic charge image development contains amorphous polyester that is a polycondensate of a polyvalent carboxylic acid and a polyhydric alcohol. The amorphous polyester has a content of a structural unit derived from a bisphenol A derivative relative to 100 mol% of a structural unit derived from the total polyhydric alcohol of 50 mol% or less relative to 100 mol% of a structural unit derived from a primary polyhydric alcohol.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus and an image forming method. [Background technology]

[0002] In recent years, in electrophotographic image forming apparatuses, in order to further increase printing speed and save energy for the purpose of reducing environmental impact, there has been a demand for electrostatic image developing toner (hereinafter also simply referred to as "toner") that can be fixed at a lower temperature by lowering the melting temperature and melt viscosity of the binder resin (see, for example, Patent Documents 1 and 2).

[0003] Patent Document 1 describes an electrophotographic toner (toner) having a binder resin containing crystalline polyester. The electrophotographic toner described in Patent Document 1 exhibits low-temperature fixability due to the plasticizing effect of containing crystalline polyester, which is a crystalline resin.

[0004] Patent Document 2 describes a toner having a binder resin containing a crystalline polyester, which is a crystalline resin, and an amorphous resin, a colorant, and a wax. In the toner manufacturing process described in Patent Document 2, a heat treatment is performed at a temperature lower than the melting point of the crystalline polyester, thereby promoting the incompatibility of the crystalline resin and the amorphous resin, which were previously compatible. This prevents the toner from deteriorating in low-temperature fixability even when stored at temperatures above the glass transition temperature. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-222138 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-42508 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the toner manufacturing process of Patent Document 1, in order to achieve the desired particle size and predetermined circularity, the toner is heated above its melting point and manufactured in a state where it is compatible with the core resin. If the toner manufactured in a state where it is compatible with the core resin is stored under high temperature and high humidity, the core and the crystalline material may become incompatible, and the low-temperature fixability may deteriorate. It is also known that even in toners composed only of amorphous resins, which do not contain crystalline resins, the low-temperature fixability gradually deteriorates even when stored at temperatures below the glass transition temperature. As such, there is still room for further study regarding the low-temperature fixability of toners.

[0007] An object of the present invention is to provide an image forming apparatus and an image forming method that maintain the low-temperature fixability of toner. [Means for solving the problem]

[0008] An image forming apparatus according to one embodiment of the present invention is an image forming apparatus for forming an image using toner for developing electrostatic images, and includes a developing unit that stores toner for developing electrostatic images and develops an electrostatic latent image formed on the surface of an electrophotographic photosensitive member to form a toner image, and a cooling unit that cools the toner for developing electrostatic images. The toner for developing electrostatic images contains an amorphous polyester that is a polycondensation product of a polycarboxylic acid and a polyhydric alcohol, and the amorphous polyester contains structural units derived from bisphenol A derivatives in an amount of 50 mol % or less relative to 100 mol % of structural units derived from first polyhydric alcohols, relative to 100 mol % of all structural units derived from polyhydric alcohols.

[0009] An image forming method according to one embodiment of the present invention is an image forming method using the image forming apparatus described above, and includes the steps of feeding the electrostatic image developing toner to the surface of an electrophotographic photosensitive member, and storing the electrostatic image developing toner and developing an electrostatic latent image formed on the surface of the electrophotographic photosensitive member to form a toner image, wherein in the step of feeding the electrostatic image developing toner to the surface of the electrophotographic photosensitive member, the cooling section cools the electrostatic image developing toner. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an image forming apparatus and an image forming method that maintain the low-temperature fixability of the toner. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram of an image forming apparatus. [Figure 2] 2A and 2B are schematic perspective views for explaining the cooling unit. [Figure 3] 3A and 3B are schematic perspective views for explaining other cooling units. DETAILED DESCRIPTION OF THE INVENTION

[0012] An image forming apparatus and an image forming method according to an embodiment of the present invention will be described in detail below.

[0013] The image forming apparatus and image forming method according to the present invention can exhibit low-temperature fixability, which is believed to be due to the following reasons.

[0014] The toner for developing electrostatic images (hereinafter also simply referred to as "toner") used in the image forming apparatus and image forming method according to the present invention contains a crystalline substance such as wax and an amorphous resin.

[0015] Usually, in the amorphous polyester resin used as the amorphous resin, a bisphenol A derivative is used as an alcohol component. However, since the bisphenol A skeleton contains two rigid benzene rings, it is difficult to reduce the viscosity when heated during fixing, and it has been found that the low-temperature fixability is poor. Therefore, in the present invention, the content of the structural unit derived from the bisphenol A derivative is set to 50 mol% or less relative to 100 mol% of the structural unit derived from the first polyhydric alcohol, thereby improving the low-temperature fixability.

[0016] The inventors also discovered that another factor that causes poor low-temperature fixability when the amorphous polyester resin contains a component derived from a bisphenol A derivative is that the material has a significantly faster enthalpy relaxation rate than aliphatic monomers. For example, in the manufacturing process of toner containing crystalline materials such as wax and amorphous resins, the toner is rapidly cooled to prevent the crystalline materials from precipitating on the toner surface. When the amorphous resin contained in the toner is rapidly cooled during the manufacturing process, it transitions to a glassy state with high enthalpy. The enthalpy of the toner gradually relaxes when exposed to temperatures close to the glass transition temperature (Tg) at which the toner does not melt. The rate of enthalpy relaxation varies depending on the toner's storage temperature, increasing significantly as the toner is exposed to temperatures close to the toner's glass transition temperature and exponentially slowing as the temperature decreases from the glass transition temperature. Heat tends to build up inside image forming devices, with temperatures around 40–50°C near the toner's glass transition temperature. Furthermore, because toner is a mixture of toner and carrier, it is easily heated by contact with the warm carrier, which has a large heat capacity. Therefore, the temperature inside many image forming devices is sufficient to accelerate the rate of toner enthalpy relaxation. As relaxation progresses, the energy required to bring the resin into glass transition increases, resulting in poor fixability. The impact on fixability also occurs with aliphatic monomers, but it is particularly problematic with bisphenol A derivative monomers, which have an extremely fast enthalpy relaxation rate. This is thought to be due to the presence of easily rotatable ether bonds in the main chain of the monomer skeleton, which facilitates rearrangement of the skeleton of molecules frozen in a glassy state due to entanglement of the main chain, making it energetically unstable. For toners whose alcohol component is an aliphatic monomer, enthalpy relaxation occurs in the short period between when the toner is replenished in the developing unit and when it is discharged, but the impact is limited. However, for toners whose alcohol component is a bisphenol A derivative, the rate of enthalpy relaxation is extremely fast, and it is believed that the glass transition temperature rises while the toner remains in the developing unit, resulting in poor fixability. For this reason, it is presumed that in the present invention, low-temperature fixability can be achieved by cooling the toner in the image forming apparatus to suppress a rise in temperature.

[0017] First, the toner for developing electrostatic images used in the image forming apparatus and image forming method will be described.

[0018] [Composition of toner for developing electrostatic images] The toner for developing electrostatic images contains an amorphous polyester resin. The toner for developing electrostatic images (toner) may be a one-component developer or a two-component developer. In the case of a one-component developer, the toner is composed of toner particles. In the case of a two-component developer, the toner is composed of toner particles and carrier particles. The toner particles are composed of toner base particles and external additives attached to the surfaces thereof. In this embodiment, the toner is preferably a two-component developer.

[0019] Examples of carrier particles include magnetic particles made of conventionally known materials such as metals such as iron, ferrite, magnetite, and alloys of these metals with metals such as aluminum and lead. Ferrite particles are preferred as carrier particles.

[0020] Examples of carrier particles include magnetic metals such as iron oxide, nickel, and cobalt, magnetic oxides such as ferrite and magnetite, resin-coated carriers using these as core particles and having a resin coating layer on the surface of the core particles, and magnetic dispersion-type carriers. The carrier particles may also be resin-dispersed carriers in which a conductive material or the like is dispersed in a matrix resin.

[0021] Examples of coating resins used to form the resin coating layer on carrier particles include polyethylene, polypropylene, polystyrene, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl ether, and polyvinyl ketone. Examples of coating resins include vinyl chloride-vinyl acetate copolymers, styrene-acrylic acid copolymers, and straight silicone resins or modified products thereof that are composed of organosiloxane bonds. Examples of coating resins include fluororesins, polyester resins, polycarbonates, phenolic resins, and epoxy resins.

[0022] Examples of the core material of the carrier particles include magnetic metals such as iron, nickel, and cobalt, magnetic oxides such as ferrite and magnetite, and glass beads. When the carrier particles are used in a magnetic brush method, the core material of the carrier particles is preferably a magnetic material. The volume average particle diameter of the core material of the carrier particles is preferably within a range of 10 to 200 μm, and more preferably within a range of 25 to 100 μm.

[0023] Methods for resin-coating the surfaces of the core material of carrier particles include a method of coating with a coating layer-forming solution prepared by dissolving the coating resin and, if necessary, various additives in a suitable solvent. The solvent is not particularly limited and may be selected appropriately taking into consideration the coating resin to be used, coating suitability, etc.

[0024] The average particle size of the carrier particles is preferably in the range of 20 to 100 μm, more preferably 25 to 80 μm, in terms of volume-based median diameter. The volume-based median diameter of the carrier particles can be measured, for example, using a laser diffraction particle size distribution analyzer (HELOS; SYMPATEC) equipped with a wet disperser.

[0025] The mixing ratio (mass ratio) of toner particles to carrier particles is not particularly limited, but from the viewpoints of chargeability and storage stability, the mixing ratio (mass ratio) of toner particles to carrier particles is preferably toner particles:carrier particles=1:100 to 30:100, and more preferably 3:100 to 20:100.

[0026] The toner base particles have a core portion disposed inside and a shell portion disposed so as to cover the surface of the core portion. The core portion has a continuous layer and a dispersion layer dispersed in the continuous layer. The continuous layer is a binder resin, and the dispersion layer contains a release agent (crystalline substance). The core-shell structure of the toner base particles ensures low-temperature fixability and heat-resistant storage stability.

[0027] The binder resin contains an amorphous polyester resin. That is, the electrostatic image developing toner contains an amorphous polyester resin. The binder resin may contain a crystalline polyester resin.

[0028] The amorphous polyester resin is the main component of the binder resin. The amorphous polyester resin improves the low-temperature fixability of the toner for developing electrostatic images and also improves the uniformity of the colorant. The amorphous polyester resin may be, for example, a block polymer with a resin having a skeleton other than a polyester skeleton, as long as it does not interfere with the function and effect of this embodiment. The amorphous polyester resin refers to a polyester resin obtained by a polycondensation reaction between a first polycarboxylic acid and a first polyhydric alcohol that does not exhibit a clear endothermic peak in differential scanning calorimetry (DSC). Here, a clear endothermic peak specifically refers to a peak whose half-width at half maximum is within 15°C when measured in DSC at a heating rate of 10°C / min.

[0029] The term "first polycarboxylic acid" refers to a compound containing two or more carboxy groups per molecule. Examples of the first polycarboxylic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelic acid, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, and 1,11-undecanedicarboxylic acid. Examples of the first polycarboxylic acid include saturated aliphatic dicarboxylic acids such as 1,12-dodecanedicarboxylic acid, 1,13-tridecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,16-hexadecanedicarboxylic acid, and 1,18-octadecanedicarboxylic acid. Examples of the first polycarboxylic acid include aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, and naphthalenedicarboxylic acid. Examples of the first polycarboxylic acid include unsaturated aliphatic dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, citraconic acid, glutaconic acid, isododecenylsuccinic acid, n-dodecenylsuccinic acid, and n-octenylsuccinic acid. Examples of the first polycarboxylic acid include trivalent or higher polycarboxylic acids such as trimellitic acid, pyromellitic acid, naphthalenetricarboxylic acid, naphthalenetetracarboxylic acid, pyrenetricarboxylic acid, and pyrenetetracarboxylic acid. One type of first polycarboxylic acid may be used, or two or more types may be used in combination.

[0030] The term "first polyhydric alcohol" refers to a compound containing two or more hydroxyl groups per molecule. Examples of first polyhydric alcohols include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, and 1,9-nonanediol. Examples of first polyhydric alcohols include 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, and 1,13-tridecanediol. Examples of first polyhydric alcohols include aliphatic diols such as 1,14-tetradecanediol, 1,18-octadecanediol, and 1,20-eicosanediol. Examples of the first polyhydric alcohol include bisphenols such as bisphenol A and bisphenol F, and alkylene oxide adducts of bisphenols such as their ethylene oxide adducts and propylene oxide adducts (these are referred to as bisphenol A derivatives). Examples of the first polycarboxylic acid include trivalent or higher polyols such as glycerin, pentaerythritol, hexamethylolmelamine, hexaethylolmelamine, tetramethylolbenzoguanamine, and tetraethylolbenzoguanamine. One type of first polyhydric alcohol may be used, or two or more types may be used in combination.

[0031] The first polyhydric alcohol preferably further contains an aliphatic polyhydric alcohol having 2 to 6 carbon atoms. The aliphatic polyhydric alcohol preferably contains ethylene glycol or 1,3-propanediol. It is particularly preferable to combine a small amount of a bisphenol A derivative, such as ethylene oxide of bisphenol A or propylene oxide of bisphenol A, with an alkylene glycol having 2 to 6 carbon atoms, in order to achieve both low-temperature fixability and heat resistance. The alkylene glycol is preferably an alcohol with a small number of carbon atoms, such as ethylene glycol or 1,3-propanediol.

[0032] The content of structural units derived from bisphenol A derivatives in the amorphous polyester resin is 50 mol% or less, preferably 10 mol% or more, and more preferably in the range of 20 to 40 mol%, relative to 100 mol% of structural units derived from the first polyhydric alcohol. If the content of structural units derived from bisphenol A derivatives is too high, it becomes difficult to ensure low-temperature fixability and the range of fluctuation in fixability also becomes large. If the content of structural units derived from bisphenol A derivatives is 10 mol% or more, it is preferable to ensure heat-resistant storage stability without excessively lowering the Tg of the toner.

[0033] Here, the structural unit derived from the first polyhydric alcohol refers to the structural unit other than the reactive hydroxyl group of the first polyhydric alcohol. Also, the structural unit derived from the bisphenol A derivative refers to the structural unit other than the reactive hydroxyl group of the bisphenol A derivative. Therefore, the structural unit derived from the bisphenol A derivative has approximately the same molecular weight as the bisphenol A derivative.

[0034] The constituent components of amorphous polyester resins can be analyzed, for example, by the following method. Pretreatment using chemical decomposition is effective for analyzing the constituent components of polyesters. Examples of chemical decomposition that are effective for analyzing the composition of polyesters, which are condensation resins, include alkaline hydrolysis and supercritical methanol decomposition.

[0035] Alkaline hydrolysis is carried out, for example, by 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. Examples of alkaline agents include sodium hydroxide and potassium hydroxide. Examples of organic solvents include methanol and DMSO (dimethyl sulfoxide). A small autoclave may be used as the container.

[0036] Then, the proton nuclear magnetic resonance ( 1The molar ratio of each component can be calculated from the peaks derived from bisphenol A derivatives and other polyhydric alcohols in the H-NMR spectrum. 1 If the molar ratio of each component cannot be calculated from the H-NMR spectrum, the polyhydric alcohol composition can be analyzed from the GC chromatogram of the decomposition solution. The content of bisphenol A derivatives in the amorphous polyester resin can be calculated using the method described above. The molar ratio of carboxylic acids can be analyzed in the same way by performing a derivatization treatment on the decomposition solution.

[0037] The method for measuring the carbon number and content (ratio) of the constituent components (constituent units) of the polyester is as described above. 1 In addition to H-NMR measurement, it can be identified by pyrolysis gas chromatography (GC / MS: Gas Chromatography / Mass Spectrometry).

[0038] The glass transition point (Tg) of the amorphous polyester resin is preferably in the range of 30 to 60°C to achieve both low-temperature fixability and heat-resistant storage stability. The glass transition point can be measured using a differential scanning calorimeter (Diamond DSC; PerkinElmer Japan Co., Ltd.). Typically, 3.0 mg of the measurement sample (amorphous resin) is sealed in an aluminum pan and set in a holder. An empty aluminum pan is used as a reference. Measurements are performed at temperatures between 0°C and 100°C, with a heating rate of 10°C / min. Analysis is performed based on the data from Heat. An extension of the baseline before the rise of the first endothermic peak and a tangent line showing the maximum slope between the rise of the first peak and the peak apex are drawn, and the intersection of these lines is determined as the glass transition point.

[0039] The weight-average molecular weight (Mw) of the amorphous polyester resin is preferably in the range of 10,000 to 50,000, more preferably in the range of 25,000 to 35,000. The number-average molecular weight (Mn) of the amorphous polyester resin is preferably in the range of 5,000 to 20,000, more preferably in the range of 6,500 to 12,000. If the molecular weight of the amorphous polyester resin is too large, sufficient low-temperature fixability may not be obtained. On the other hand, if the molecular weight of the amorphous polyester resin is too small, sufficient fixation separation may not be obtained. The weight-average molecular weight and number-average molecular weight of the amorphous polyester resin can be determined from the molecular weight distribution measured by gel permeation chromatography (GPC) as shown below.

[0040] The weight-average molecular weight was determined from the molecular weight distribution measured by gel permeation chromatography (GPC). Specifically, a Tosoh HLC-8120GPC system and a Tosoh TSKguard column with a triple TSKgel Super HZ-M column were used, with the column temperature maintained at 40°C. Tetrahydrofuran (THF) was used as the carrier solvent at a flow rate of 0.2 mL / min. The measurement sample (crystalline polyester resin) was dissolved in tetrahydrofuran at room temperature using an ultrasonic disperser for 5 minutes to a concentration of 1 mg / mL. The solution was then filtered through a 0.2 μm pore membrane filter to obtain a sample solution. 10 μL of the sample solution was injected into the system along with the carrier solvent and detected using a refractive index detector (RI detector). The molecular weight distribution of the measurement sample was calculated using a calibration curve measured using monodisperse polystyrene standard particles. Ten polystyrene samples were used for the calibration curve measurement.

[0041] The content of the amorphous polyester resin in the binder resin is preferably within a range of 70 to 99% by mass. When the content of the amorphous polyester resin is within the above range, sufficient low-temperature fixability, sufficient heat-resistant storage stability of the toner, and sufficient heat resistance of the fixed image can be ensured when the amorphous polyester resin is used as a binder resin together with a crystalline polyester resin.

[0042] Crystalline polyester resins are polyester resins obtained by polycondensation reaction of a second polycarboxylic acid and a second polyhydric alcohol. Crystalline polyester resins are resins that exhibit a clear endothermic peak rather than a stepwise endothermic change in differential scanning calorimetry (DSC) of the crystalline resin or toner base particles. Specifically, a clear endothermic peak means a peak whose half-width is 15°C or less when measured in DSC at a heating rate of 10°C / min. Crystalline polyester resins are crystalline substances that are different from crystalline substances.

[0043] The second polycarboxylic acid refers to a compound containing two or more carboxyl groups per molecule. Examples of dicarboxylic acids include oxalic acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, and 1,12-dodecanedicarboxylic acid. Other examples of dicarboxylic acids include saturated aliphatic dicarboxylic acids such as 1,14-tetradecanedicarboxylic acid and 1,18-octadecanedicarboxylic acid. Other examples of dicarboxylic acids include aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, naphthalene-2,6-dicarboxylic acid, malonic acid, and mesaconic acid. Other examples of dicarboxylic acids include anhydrides of the above-mentioned carboxylic acid compounds and alkyl esters having 1 to 3 carbon atoms. From the viewpoint of intramolecular polarity, adipic acid and sebacic acid having approximately 6 to 10 carbon atoms are preferred as the second polycarboxylic acid.

[0044] Examples of trivalent or higher carboxylic acids include 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, etc., as well as anhydrides and lower (C1 to C3) alkyl esters of these. One type of second polycarboxylic acid may be used alone, or two or more types may be used in combination.

[0045] The secondary polyhydric alcohol refers to a compound containing two or more hydroxyl groups in one molecule. Examples of the secondary polyhydric alcohol include diols and trihydric or higher alcohols.

[0046] Examples of diols include saturated aliphatic diols. Examples of saturated aliphatic diols include linear saturated aliphatic diols and branched saturated aliphatic diols. The saturated aliphatic diol is preferably a linear saturated aliphatic diol, more preferably a linear saturated aliphatic diol having 2 to 6 carbon atoms. If the saturated aliphatic diol is branched, the crystallinity of the crystalline polyester resin may decrease, resulting in a lower melting point. Furthermore, if the carbon number of the saturated aliphatic diol exceeds 12, it becomes difficult to obtain a practical material.

[0047] Examples of saturated aliphatic diols include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, and 1,8-octanediol. Examples of saturated aliphatic diols include 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, and 1,13-tridecanediol. Examples of saturated aliphatic diols include 1,14-tetradecanediol, 1,18-octadecanediol, and 1,14-eicosanedecanediol.

[0048] The saturated aliphatic diol is preferably ethylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, or 1,12-dodecanediol. The saturated aliphatic diol provides high crystallinity to the crystalline polyester resin and excellent sharp melting properties.

[0049] Examples of trihydric or higher alcohols include glycerin, trimethylolethane, trimethylolpropane, and pentaerythritol. The second polyhydric alcohols may be used alone or in combination of two or more.

[0050] The number of carbon atoms in the second polycarboxylic acid and the number of carbon atoms in the second polyhydric alcohol are both preferably 2 to 12 or less. The crystalline polyester resin is preferably composed of a linear saturated aliphatic dicarboxylic acid having 2 to 6 carbon atoms and a linear saturated aliphatic diol having 2 to 6 carbon atoms. This results in high crystallinity and excellent sharp melting properties, allowing for excellent low-temperature fixability. Methods for controlling the crystallinity and softening point of the crystalline polyester resin include the use of a nonlinear polyester. Nonlinear polyesters can be obtained by condensation polymerization of a trivalent or higher polyhydric alcohol, such as glycerin, with a trivalent or higher polycarboxylic acid, such as trimellitic anhydride.

[0051] The molecular weight of a crystalline polyester resin is measured by gel permeation chromatography (GPC). The same measuring device as used to measure the weight-average molecular weight of an amorphous polyester resin can be used. Crystalline polyester resins have a sharp molecular weight distribution and low molecular weights, which provide excellent low-temperature fixability, while a high concentration of low-molecular-weight components leads to poor heat-resistant storage stability. The molecular weight distribution of crystalline polyester resins, as measured by GPC, of ​​the o-dichlorobenzene-soluble fraction is plotted on a molecular weight distribution chart with the horizontal axis representing log(M) and the vertical axis representing weight percent, and the peak position is within the range of 3.5 to 4.0, with a half-width of the peak of 1.5 or less. The weight-average molecular weight (Mw) is preferably within the range of 3,000 to 30,000, the number-average molecular weight (Mn) within the range of 1,000 to 10,000, and the Mw / Mn ratio within the range of 1 to 10. Furthermore, it is preferable that the weight average molecular weight (Mw) is within a range of 5,000 to 15,000, the number average molecular weight (Mn) is within a range of 2,000 to 10,000, and Mw / Mn is within a range of 1 to 5. The weight average molecular weight and number average molecular weight of the crystalline polyester resin can be determined in the same manner as the weight average molecular weight and number average molecular weight of the amorphous polyester resin.

[0052] The content of the crystalline polyester resin in the toner is preferably within the range of 2 to 30% by mass. If the amount of crystalline polyester added is too small, the effect of low-temperature fixability is difficult to exhibit. On the other hand, if the content of the crystalline polyester resin in the toner is too high, it becomes difficult to incorporate the crystalline polyester resin into the toner, and it may be expelled onto the toner surface, causing a decrease in heat resistance.

[0053] The toner particles may further contain a colorant. Known dyes and pigments can be used as the colorant. Examples of colorants include carbon black, nigrosine dye, iron black, naphthol yellow S, Hansa yellow (10G, 5G, G), cadmium yellow, yellow iron oxide, yellow ochre, yellow lead, titanium yellow, polyazo yellow, oil yellow, Hansa yellow (GR, A, RN, R), pigment yellow L, benzidine yellow (G, GR), permanent yellow (NCG), Vulcan fast yellow (5G, R), tartrazine lake, quinoline yellow lake, anthrazan yellow BGL, isoindolinone yellow, red iron oxide, and lead. Red vermilion, cinnabar, cadmium red, cadmium mercury red, antimony vermilion, permanent red 4R, para red, faise red, parachloro orthonitroaniline red, Lithol Fast Scarlet G, Brilliant Fast Scarlet, Brilliant Carmine BS, permanent red (F2R, F4R, FRL, FRLL, F4RH), Fast Scarlet VD, Belcan Fast Rubin B, Brilliant Scarlet G, Lithol Rubin GX, permanent red F5R, Brilliant Carmine 6B , Pogment Scarlet 3B, Bordeaux 5B, Toluidine Maroon, Permanent Bordeaux F2K, Helio Bordeaux BL, Bordeaux 10B, Bon Maroon Light, Bon Maroon Medium, Eosin Lake, Rhodamine Lake B, Rhodamine Lake Y, Alizarin Lake, Thioindigo Red B, Thioindigo Maroon, Oil Red, Quinacridone Red, Pyrazolone Red, Polyazo Red, Chrome Vermilion, Benzidine Orange, Perinone Orange, Oil Orange, Cobalt Blue, Cerulean Blue, Alkali Blue Lu Lake, Peacock Blue Lake, Victoria Blue Lake, Metal-free Phthalocyanine Blue, Phthalocyanine Blue, Fast Sky Blue, Indanthrene Blue (RS, BC), Indigo, Ultramarine, Prussian Blue, Anthraquinone Blue, Fast Violet B, Methyl Violet Lake, Cobalt Purple, Manganese Purple, Dioxane Violet, Anthraquinone Violet, Chrome Green, Zinc Green, Chromium Oxide, Pyridian, Emerald Green, Pigment Green B, Naphthol Green B, Green Gold,Acid green lake, malachite green lake, phthalocyanine green, anthraquinone green, titanium oxide, zinc oxide, lithopone, and mixtures thereof can be used.

[0054] Release agents (crystalline substances) ensure the toner's fixing and separation properties. Examples of release agents include waxes. Examples of release agents include plant-based waxes such as carnauba wax, cotton wax, Japan wax, and rice wax. Examples of release agents include animal-based waxes such as beeswax and lanolin; mineral-based waxes such as ozokerite and cerusine; and natural waxes such as petroleum waxes like paraffin, microcrystalline wax, and petrolatum. Examples of release agents include synthetic hydrocarbon waxes such as Fischer-Tropsch wax and polyethylene wax; and synthetic waxes such as esters, ketones, and ethers. Examples of release agents include fatty acid amides such as 12-hydroxystearic acid amide, stearic acid amide, phthalic anhydride imide, and chlorinated hydrocarbons. Examples of release agents include low molecular weight crystalline polymer resins, such as polyacrylate homopolymers or copolymers (e.g., n-stearyl acrylate-ethyl methacrylate copolymers), polyacrylates such as poly-n-stearyl methacrylate and poly-n-lauryl methacrylate; crystalline polymers having long alkyl groups in their side chains; etc. One type of release agent may be used alone, or two or more types may be used in combination.

[0055] The melting point of the release agent is preferably 50° C. or higher and 120° C. or lower, and more preferably 60° C. or higher and 90° C. or lower. If the melting point is 50° C. or higher, the release agent can be prevented from adversely affecting heat-resistant storage stability, and if the melting point is 120° C. or lower, cold offset during fixation at low temperatures can be effectively prevented.

[0056] The content of the release agent in the toner particles is preferably 0% by mass or more and 20% by mass or less, and more preferably 3% by mass or more and 15% by mass or less. If the content of the release agent in the toner particles is 20% by mass or less, deterioration of the fluidity of the toner can be prevented. By using a biologically or naturally derived compound as the release agent, it is possible to improve the biomass content of the entire toner.

[0057] As described above, the toner base particles have a core-shell structure. Here, the term "core-shell structure" refers to a structure having a core disposed inside and a shell covering the surface of the core. "Core-covering the core" does not necessarily mean covering the entire core, but rather covering the core to an extent that the conductive polymer functions. The core-shell toner base particles have a resin particle (core) containing a colorant, a release agent, etc., and a relatively low glass transition point, and a resin region (shell) on the surface of the core that has a relatively high glass transition point. In the core-shell structure, the shell may completely cover the core, or the shell may not completely cover the core, leaving a portion of the core exposed. The shell can be produced by agglomerating and fusing the core to the surface. The cross-sectional structure of the core-shell structure can be confirmed using known means, such as a transmission electron microscope or a scanning probe microscope.

[0058] Examples of the resin constituting the shell portion include amorphous polyester resin and vinyl resin. The resin constituting the shell portion preferably has an alkyl unit derived from one or more compounds selected from the group consisting of aliphatic monocarboxylic acids having from 10 to 30 carbon atoms and aliphatic monoalcohols having from 10 to 30 carbon atoms.

[0059] The content of the shell portion in the toner base particles is preferably within the range of 5 to 30% by mass. If the content of the shell portion in the toner base particles is less than 5% by mass, the coverage of the core portion decreases, and the conductive polymer is exposed on the toner surface, which may result in an inability to retain the charge amount required for a developer. Furthermore, if the content of the shell portion in the toner base particles exceeds 30% by mass, low-temperature fixability may be reduced.

[0060] In the toner of the present invention, the toner particles can be used as they are, but external additives such as so-called fluidizing agents and cleaning aids may be added to the toner particles to improve fluidity, chargeability, cleaning properties, etc. Various external additives may be used in combination. The total amount of these external additives added is preferably within a range of 0.05 to 5 parts by mass, more preferably 0.1 to 3 parts by mass, per 100 parts by mass of toner particles.

[0061] [Characteristics of electrostatic image developing toner] (Toner particle size) The average particle size of the toner is preferably, for example, a volume-based median diameter in the range of 3 to 10 μm, more preferably 5 to 8 μm. The average particle size of the toner can be controlled by the concentration of the coagulant used during production, the amount of organic solvent added, the fusion time, the composition of the binder resin, etc. By keeping the volume-based median diameter of the toner within the above range, it is possible to faithfully reproduce extremely fine dot images at the 1200 dpi level.

[0062] The volumetric median diameter of toner was measured and calculated using a measuring device connected to a computer system equipped with the data processing software "Software V3.51" (manufactured by Beckman Coulter, Inc.). Specifically, 0.02 g of toner was added to 20 mL of surfactant solution (a surfactant solution prepared by diluting a neutral detergent containing surfactant components 10 times with pure water to disperse the toner particles), and then ultrasonically dispersed for 1 minute to prepare a toner dispersion. This toner dispersion was then pipetted into a beaker containing an "ISOTON II" (manufactured by Beckman Coulter, Inc.) in the sample stand until the measurement device indicated a concentration of 8%. Maintaining this concentration range ensures reproducible measurements. Then, in the measuring device, the number of measured particles is set to 25,000, the aperture diameter is set to 100 μm, the measurement range of 2 to 60 μm is divided into 256 parts, and the frequency value is calculated. The particle diameter of the largest 50% of the volume cumulative fraction is taken as the volume-based median diameter.

[0063] (Average circularity of toner) From the viewpoint of the stability of charging characteristics and low-temperature fixability, the average circularity of the toner particles is preferably in the range of 0.930 to 1.000, more preferably in the range of 0.950 to 0.995. When the average circularity is in the above range, the toner particles are less likely to be crushed, the charging characteristics of the toner are stable, and high-quality images can be formed.

[0064] The average circularity of the toner can be measured using an "FPIA-3000" (Sysmex Corporation). Specifically, the toner is mixed in an aqueous solution containing a surfactant and dispersed by ultrasonic dispersion treatment for 1 minute. Next, using the "FPIA-3000" (Sysmex Corporation), images are taken using the measurement conditions HPF (high magnification imaging) mode at an appropriate density of 3,000 to 10,000 HPF detections. Next, the circularity of each toner particle is calculated according to the following formula (y), and the circularity of each toner particle is added up and divided by the total number of toner particles. If the HPF detection number is within the above range, reproducibility can be obtained. Formula (y): Circularity = (perimeter of a circle with the same projected area as the particle image) / (perimeter of the projected particle image)

[0065] (Charge control agent) A charge control agent may be added to the toner particles. Examples of charge control agents that can be used include known agents. Examples of charge inhibitors include nigrosine dyes, triphenylmethane dyes, chromium-containing metal complex dyes, molybdate chelate pigments, rhodamine dyes, and alkoxyamines. Other examples of charge inhibitors include quaternary ammonium salts (including fluorine-modified quaternary ammonium salts), alkylamides, phosphorus simple substances or compounds, tungsten simple substances or compounds, fluorine-based activators, metal salicylate salts, and metal salts of salicylic acid derivatives. Other examples of charge inhibitors include copper phthalocyanine, perylene, quinacridone, azo pigments, and polymeric compounds having functional groups such as sulfonic acid groups, carboxyl groups, and quaternary ammonium salts.

[0066] Commercially available examples of charge control agents include the nigrosine dye Bontron 03, the quaternary ammonium salt Bontron P-51, and the metal-containing azo dye Bontron S-34 (all from Orient Chemical Industry Co., Ltd.). Other examples of commercially available products include the oxynaphthoic acid metal complex E-82, the salicylic acid metal complex E-84, and the phenol condensate E-89 (all from Orient Chemical Industry Co., Ltd.). Other examples of commercially available products include the quaternary ammonium salt molybdenum complexes TP-302 and TP-415 (both from Hodogaya Chemical Co., Ltd.). Other examples of commercially available products include the quaternary ammonium salt Copy Charge PSY VP2038, the triphenylmethane derivative Copy Blue PR, and the quaternary ammonium salts Copy Charge NEG VP2036 and Copy Charge NX VP434 (all from Hoechst). Other examples of commercially available products include LRA-901 and LR-147, a boron complex (both manufactured by Nippon Carlit Co., Ltd.).

[0067] The content of the charge control agent may be in the range that does not impair low-temperature fixability, and is preferably in the range of 0.5 to 5% by mass, more preferably 0.8 to 3% by mass in the toner.

[0068] [Method of manufacturing electrostatic image developing toner] The toner for developing electrostatic images can be produced, for example, by the following method. The method for producing the toner for developing electrostatic images includes an oil phase preparation step, a phase inversion emulsification step, a solvent removal step, and an aggregation step. The method for producing the toner for developing electrostatic images may also include an aqueous phase preparation step, a fusion step, a shell formation step, a washing step, a drying step, an annealing step, and the like, at any timing, as necessary.

[0069] (Oil phase preparation process) In the oil phase preparation step, a solution is prepared by dissolving or dispersing a binder resin and / or a binder resin precursor (such as a monomer or prepolymer that becomes the binder resin), a colorant, and a release agent in an organic solvent. Specifically, first, an oil phase is prepared by dissolving or dispersing the binder resin, colorant, prepolymer, etc. in an organic solvent. To prepare the oil phase, the resin, colorant, etc. are gradually added to the organic solvent while stirring, and dissolved or dispersed. Known methods can be used for dissolving or dispersing. For example, the dissolving or dispersing method may be performed by stirring using a disperser such as a bead mill or a disk mill.

[0070] The organic solvent used in the oil phase preparation step is preferably a volatile liquid with a boiling point of less than 100°C, so that it can be easily removed in subsequent steps. Examples of organic solvents include toluene, xylene, benzene, carbon tetrachloride, methylene chloride, 1,2-dichloroethane, 1,1,2-trichloroethane, trichloroethylene, chloroform, monochlorobenzene, and dichloroethylidene. Other examples of organic solvents include ester-based solvents such as methyl acetate and ethyl acetate, ketone-based solvents such as methyl ethyl ketone and methyl isobutyl ketone, and alcohol-based solvents such as methanol, ethanol, and isopropyl alcohol. One type of organic solvent may be used alone, or two or more types may be used in combination.

[0071] The organic solvent is preferably an ester solvent or a ketone solvent from the viewpoint of solubility, and particularly preferably methyl acetate, ethyl acetate, or methyl ethyl ketone from the viewpoint of high solvent removability.

[0072] An aqueous phase preparation step may be included after the oil phase preparation step. In the aqueous phase preparation step, an aqueous phase (aqueous medium) is prepared. The aqueous medium can be appropriately selected from known ones. Examples of aqueous media include water, water-miscible solvents, and mixtures thereof. The water-miscible solvent can be appropriately selected from known ones. Examples of water-miscible solvents include alcohol, dimethylformamide, tetrahydrofuran, cellosolves, lower ketones, and esters. Examples of alcohols include methanol, isopropanol, and ethylene glycol. Examples of lower ketones include acetone and methyl ethyl ketone. Examples of esters include ethyl acetate. One type of aqueous solvent may be used alone, or two or more types may be used in combination.

[0073] (Phase inversion emulsification process) In the phase inversion emulsification step, water is added to the solution obtained in the oil phase preparation step to invert the phase from a water-in-oil dispersion to an oil-in-water dispersion. In this embodiment, the oil phase is neutralized with ammonia water or the like, and then ion-exchanged water is added thereto to invert the phase from the water-in-oil dispersion to an oil-in-water dispersion, thereby obtaining a microparticle dispersion by phase inversion emulsification.

[0074] (solvent removal process) In the desolvation step, the organic solvent is removed from the microparticle dispersion obtained in the phase inversion emulsification step to obtain a microparticle dispersion. The first method for removing the organic solvent from the microparticle dispersion is not particularly limited. Examples of methods for removing the organic solvent from the microparticle dispersion include a method in which the temperature is gradually increased while stirring the entire system to completely evaporate the organic solvent in the microparticle dispersion. The second method for removing the organic solvent from the microparticle dispersion includes a method in which the obtained microparticle dispersion is sprayed into a dry atmosphere while stirring to completely remove the organic solvent in the droplets. The third method for removing the organic solvent from the microparticle dispersion includes a method in which the pressure is reduced while stirring the microparticle dispersion to evaporate the organic solvent. The second and third methods can be used in combination with the first method.

[0075] Examples of drying atmospheres into which the microparticle dispersion is sprayed include air, nitrogen, carbon dioxide, heated combustion gases, etc., particularly various air streams heated to a temperature equal to or higher than the boiling point of the highest boiling point solvent used. By using a spray dryer, belt dryer, rotary kiln, etc., the desired quality can be obtained sufficiently in a short treatment time.

[0076] (agglomeration process) In the aggregation process, the fine particles in the fine particle dispersion obtained in the solvent removal process are aggregated to obtain aggregated particles. In the aggregation process, wax may be added as a release agent, or a crystalline resin may be added to improve low-temperature fixability. In this case, a dispersion in which wax is dispersed in an aqueous medium or a dispersion in which a crystalline resin is similarly dispersed is prepared, and these are mixed with the fine particle dispersion and then aggregated to obtain aggregated particles in which the wax or crystalline resin is uniformly dispersed.

[0077] At this time, the microparticle dispersion is agitated to aggregate until the desired particle size is reached. Examples of aggregation methods that can be used include adding a flocculant and adjusting the pH. When adding the flocculant, it may be added directly, but it is preferable to use an aqueous solution of the flocculant, as this can prevent localized high concentrations. It is also preferable to gradually add the flocculating salt while monitoring the particle size of the aggregated particles.

[0078] The temperature of the microparticle dispersion during aggregation is preferably near the Tg of the resin used. If the liquid temperature is too low, aggregation does not proceed very well, resulting in poor efficiency, while if the liquid temperature is too high, the aggregation rate increases, resulting in the generation of coarse particles and a deterioration in particle size distribution.

[0079] When the desired particle size is reached, aggregation is stopped. Examples of methods for stopping aggregation include adding a salt or a chelating agent with a low ionic valence, adjusting the pH, lowering the temperature of the dispersion, or adding a large amount of aqueous medium to dilute the concentration.

[0080] The flocculant used in the flocculation step may be a known one. Examples of the flocculant used in the flocculation step include metal salts of monovalent metals such as sodium and potassium, metal salts of divalent metals such as calcium and magnesium, and metal salts of trivalent metals such as iron and aluminum.

[0081] By adding a metal salt as a flocculant, the metal ions act as a metal crosslinking agent, crosslinking the polymer chains and causing agglomeration. Metal crosslinking by the metal crosslinking agent is expected to improve hot offset resistance, storage stability, and durability.

[0082] (fusion process) The fusion step may include a step of fusing the aggregated particles obtained in the aggregation step by heat treatment to reduce unevenness. In the fusion step, the dispersion of aggregated particles may be heated while being stirred. The heat treatment temperature is preferably near a temperature exceeding the glass transition temperature (Tg) of the resin used.

[0083] (Washing and drying process) The microparticle dispersion contains, in addition to resin particles, secondary materials such as coagulated salts. Therefore, the production method according to this embodiment preferably includes a washing step for extracting only the resin particles from the dispersion. The method for washing the resin particles is not particularly limited. Examples of the method for washing the resin particles include centrifugation, vacuum filtration, and filter press.

[0084] Any of the above-mentioned methods can obtain a cake of resin particles, but if the resin particles cannot be sufficiently washed in one operation, the obtained cake may be dispersed again in an aqueous solvent to form a slurry, and the process of extracting the resin particles (toner base particles) by any of the above-mentioned methods may be repeated. If washing is performed by vacuum filtration or filter press, a method in which the aqueous solvent is passed through the cake to wash away the secondary materials absorbed by the resin particles may also be used.

[0085] The aqueous solvent used in the washing step is water or a mixed solvent of water and an alcohol such as methanol or ethanol, but water is preferred from the viewpoints of cost and environmental load due to wastewater treatment.

[0086] Since the washed resin particles contain a large amount of aqueous medium, the toner particles can be obtained by drying them to remove the aqueous medium. Examples of dryers used for the drying method include spray dryers, vacuum freeze dryers, reduced pressure dryers, stationary shelf dryers, mobile shelf dryers, fluidized bed dryers, rotary dryers, and agitator dryers. The moisture content of the dried resin particles is preferably less than 1%.

[0087] Furthermore, the resin particles after drying may become soft and agglomerated, which may cause inconvenience during use. In such cases, the soft and agglomerated particles may be broken down using a device such as a jet mill, a Henschel mixer, a super mixer, a coffee mill, an Oster blender, or a food processor.

[0088] (Annealing process) When a crystalline resin is added, annealing the material after drying causes phase separation between the amorphous polyester resin and the crystalline resin, improving heat resistance. The annealing process involves storing the material at a temperature near its Tg for 10 hours or more.

[0089] (External addition process) The resin particles (toner base particles) obtained in this embodiment may be mixed with external additives to impart fluidity, chargeability, cleaning properties, etc. This allows for the production of a toner containing resin particles and external additives. Examples of external additives include inorganic fine particles, polymeric fine particles, and cleaning aids. Examples of mixing methods include applying impact force to the mixture using a blade rotating at high speed, and introducing the mixture into a high-speed air stream, accelerating it, and causing particles or composite particles to collide with an appropriate collision plate. Examples of mixing devices include an Ang Mill (Hosokawa Micron Corporation), an I-type Mill (Nippon Pneumatic Mfg. Co., Ltd.), a device with reduced grinding air pressure, and a Hybridization System (Nara Machinery Works, Ltd.). Other examples of mixing devices include a Kryptron System (Kawasaki Heavy Industries, Ltd.) and an automatic mortar.

[0090] The primary particle diameter of the inorganic fine particles as an external additive is preferably 5 nm or more and 2 μm or less, more preferably 5 nm or more and 500 nm or less. 2 / g or more 500m 2 / g or less is preferable. The content of inorganic fine particles is preferably within the range of 0.01 to 5% by mass. Examples of inorganic fine particles include silica, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, tin oxide, silica sand, clay, mica, wollastonite, and diatomaceous earth. Other examples of inorganic fine particles include chromium oxide, cerium oxide, red iron oxide, antimony trioxide, magnesium oxide, zirconium oxide, barium sulfate, barium carbonate, calcium carbonate, silicon carbide, and silicon nitride.

[0091] Examples of polymeric fine particles include polymer particles made of polystyrene, methacrylate ester or acrylate ester copolymers obtained by soap-free emulsion polymerization, suspension polymerization, or dispersion polymerization, or polycondensation systems such as silicone, benzoguanamine, or nylon, or thermosetting resins.

[0092] Such fluidizing agents increase hydrophobicity through surface treatment, and can prevent deterioration of flow properties and charging properties even under high humidity. Examples of surface treatment agents include silane coupling agents, silylating agents, silane coupling agents having a fluorinated alkyl group, organic titanate-based coupling agents, aluminum-based coupling agents, silicone oils, and modified silicone oils.

[0093] Examples of cleaning improvers for removing residual developer remaining on the photoreceptor or primary transfer medium after transfer include fatty acid metal salts such as zinc stearate, calcium stearate, and stearic acid. Specific examples of cleaning improvers include polymer microparticles produced by soap-free emulsion polymerization, such as polymethyl methacrylate microparticles and polystyrene microparticles. The volume average particle diameter of the polymer microparticles has a relatively narrow particle size distribution and is preferably within the range of 0.01 to 1 μm.

[0094] [Image forming equipment] Next, an image forming apparatus for forming an image using the above-described electrostatic image developing toner will be described. Fig. 1 is a diagram showing the configuration of an image forming apparatus 1 according to the present embodiment.

[0095] As shown in Fig. 1, image forming apparatus 1 is an intermediate transfer type color image forming apparatus that utilizes electrophotographic process technology. That is, image forming apparatus 1 primarily transfers toner images of each color, Y (yellow), M (magenta), C (cyan), and K (black), formed on photosensitive drum 413, onto intermediate transfer belt 421. Next, the four color toner images are superimposed on intermediate transfer belt 421, and then secondarily transferred onto paper S (recording medium) to form an image. Note that image forming apparatus 1 may also be an apparatus that forms a single-color image (e.g., a monochrome image).

[0096] The image forming apparatus 1 employs a tandem system in which photosensitive drums 413 corresponding to the four colors YMCK are arranged in series in the running direction of an intermediate transfer belt 421, and each color toner image is transferred sequentially to the intermediate transfer belt 421 in a single step.

[0097] The image forming apparatus 1 includes an image reading unit 10, an operation display unit 20, an image processing unit 30, an image forming unit 40, a paper conveying unit 50, and a fixing unit 60.

[0098] The image reading unit 10 has an automatic document feeder 11 called an ADF (Auto Document Feeder) and an original image scanning device 12 (scanner).

[0099] The automatic document feeder 11 transports the documents D placed on the document tray using a transport mechanism and sends them to the document image scanning device 12. The automatic document feeder 11 can continuously read images (including both sides) of multiple documents D placed on the document tray all at once.

[0100] The document image scanning device 12 optically scans a document transported from the automatic document feeder 11 onto the contact glass or a document placed on the contact glass. Then, light reflected from the document is focused on the light receiving surface of a CCD (Charge Coupled Device) sensor 12a, and the document image is read. The image reading unit 10 generates input image data based on the reading result by the document image scanning device 12. This input image data is subjected to predetermined image processing in the image processing unit 30.

[0101] The operation display unit 20 is, for example, a liquid crystal display with a touch panel, and functions as both a display unit 21 and an operation unit 22. The display unit 21 displays various operation screens, image status displays, and the operating status of each function in accordance with a display control signal input from the control unit 100. The operation unit 22 has various operation keys such as a numeric keypad and a start key, and accepts various input operations by the user and outputs operation signals to the control unit 100.

[0102] The image processing unit 30 includes a circuit for performing digital image processing on input image data according to initial settings or user settings. For example, the image processing unit 30 performs gradation correction based on gradation correction data. The image processing unit 30 also performs various correction processes, such as gradation correction, color correction, and shading correction, as well as compression processes, on the input image data. The image forming unit 40 is controlled based on the image data that has undergone these processes.

[0103] The image forming section 40 has image forming units 41Y, 41M, 41C, and 41K for forming images with color toners of Y, M, C, and K components based on input image data, and an intermediate transfer unit .

[0104] Image forming units 41Y, 41M, 41C, and 41K for the Y, M, C, and K components have the same configuration. In the following description, for convenience of illustration and explanation, common components are denoted by the same reference numerals, and when distinguishing between them, the reference numerals are suffixed with Y, M, C, or K. In Figure 1, reference numerals are assigned only to the components of image forming unit 41Y for the Y component, and reference numerals are omitted for the components of the other image forming units 41M, 41C, and 41K.

[0105] The image forming unit 41 includes an exposure device 411, a developing section 412, a photosensitive drum (image forming section) 413, a charging device 414, a drum cleaning device 415, and a cooling section 416.

[0106] Exposure device 411 is, for example, a semiconductor laser, and irradiates photosensitive drum 413 with laser light corresponding to an image of each color component. As a result, an electrostatic latent image of each color component is formed on the surface of photosensitive drum 413 due to a potential difference with the surroundings.

[0107] The developing unit 412 is, for example, a two-component reverse development unit, and visualizes the electrostatic latent image to form a toner image by adhering toner of each color component to the surface of the photosensitive drum 413. The developing unit 412 includes a container 35a for containing a two-component developer, stirring rollers 35b, 35b contained in the container 35a, developing rollers 35c, 35c for transporting the contained developer and supplying toner to the photosensitive drum 32, and a developing sleeve. To the developing sleeve, for example, a DC developing bias having the same polarity as the charging polarity of the charging device 414, or a developing bias obtained by superimposing a DC voltage having the same polarity as the charging polarity of the charging device 414 on an AC voltage, is applied. As a result, reversal development is performed in which toner is adhered to the electrostatic latent image formed by the exposure device 411.

[0108] The photosensitive drum 413 is an organic photosensitive body in which a photosensitive layer made of resin containing an organic photoconductor is formed on the outer peripheral surface of, for example, a drum-shaped metal substrate.

[0109] The charging device 414 is, for example, a charger, and generates a corona discharge to uniformly charge the surface of the photoconductive photosensitive drum 413 to a negative polarity.

[0110] The drum cleaning device 415 is in contact with the surface of the photosensitive drum 413 and has a flat drum cleaning blade made of an elastic material, and removes toner remaining on the surface of the photosensitive drum 413 without being transferred to the intermediate transfer belt 421.

[0111] 2A, 2B, 3A, and 3B are schematic perspective views showing the configuration of cooling unit 416. Cooling unit 416 cools the electrostatic image developing toner sent to photoconductor drum 413 to a temperature below the glass transition temperature. More specifically, cooling unit 416 cools the toner to a temperature lower than the glass transition temperature of the electrostatic image developing toner. The cooling temperature is preferably 20° C. lower than the glass transition temperature, and more preferably 30° C. lower. Cooling unit 416 may cool the electrostatic image developing toner directly or indirectly. Cooling unit 416 preferably cools developing unit 412. By cooling developing unit 412 with cooling unit 416, the function of developing unit 412 is not impaired.

[0112] 2A, the cooling unit 416 may cool the toner for developing electrostatic images by cooling the container 35a of the developing unit 412. In this case, the cooling unit 416 is set to a low temperature. The cooling unit 416 cools the container 35a by coming into contact with the container 35a, and the cooled container 35a cools the toner for developing electrostatic images.

[0113] 2B, cooling section 416 may be disposed inside developing section 412 and cool the toner for developing electrostatic images by cooling the atmosphere inside developing section 412. Cooling section 416 is disposed along the longitudinal direction of developing section 412 or a member in contact with developing section 412. Cooling section 416 is designed to release heat from the end portion thereof.

[0114] As shown in FIG. 3A, cooling unit 416 may be configured such that a hollow tube is disposed in the internal space of development unit 412 and a refrigerant is circulated inside the tube to cool the toner for developing electrostatic images. The tube is disposed along the longitudinal direction of development unit 412 or a member in contact with development unit 412. Examples of refrigerants include low-temperature cooling liquids such as cold water or an aqueous solution of ethylene glycol, and low-temperature gases such as air. The temperature of the refrigerant is preferably lower than the ambient temperature of image forming apparatus 1. Cooling unit 416 may further include a temperature adjustment device for adjusting the temperature of the refrigerant.

[0115] 3B, the cooling unit 416 may have a cooling fan 35d on the upstream side of the hollow tube. In this case, it is preferable to provide an exhaust fan 35e on the opposite side of the cooling fan 35d (downstream side of the hollow tube). This creates an airflow that can effectively cool the toner for developing electrostatic images.

[0116] Although not specifically shown, the agitating roller 35b and the developing roller 35c may be cooled. In this case, a cooling unit 416 is disposed inside the agitating roller 35b and the developing roller 35c, thereby cooling the agitating roller 35b and the developing roller 35c, and the toner for developing electrostatic images on the surfaces of the agitating roller 35b and the developing roller 35c. Alternatively, a hollow tube may be disposed inside the agitating roller 35b and the developing roller 35c, and a refrigerant may be circulated inside the tube to cool the toner for developing electrostatic images. Alternatively, a hollow tube may be disposed in the path of the toner for developing electrostatic images between the toner bottle and the photosensitive drum 413, and a refrigerant may be circulated inside the tube to cool the toner for developing electrostatic images.

[0117] The intermediate transfer unit 42 includes a primary transfer roller 422 , a plurality of support rollers 423 , a secondary transfer roller 424 , and a belt cleaning device 426 that includes the intermediate transfer belt 421 .

[0118] Primary transfer rollers 422 are disposed opposite photosensitive drums 413 of each color component on the inner peripheral side of intermediate transfer belt 421. Primary transfer rollers 422 are pressed against photosensitive drums 413 with intermediate transfer belt 421 sandwiched therebetween, thereby forming a primary transfer nip for transferring a toner image from photosensitive drum 413 to intermediate transfer belt 421.

[0119] Secondary transfer roller 424 is disposed on the outer circumferential surface side of intermediate transfer belt 421, facing backup roller 423B, which is disposed downstream of roller 423A in the belt running direction. Secondary transfer roller 424 is pressed against backup roller 423B with intermediate transfer belt 421 sandwiched therebetween, thereby forming a secondary transfer nip for transferring a toner image from intermediate transfer belt 421 to paper S.

[0120] When intermediate transfer belt 421 passes through the primary transfer nip, the toner images on photosensitive drum 413 are primarily transferred onto intermediate transfer belt 421 in a sequentially overlapping manner. Specifically, a primary transfer bias is applied to primary transfer roller 422, and a charge of the opposite polarity to the toner is applied to the back side of intermediate transfer belt 421 (the side that abuts against primary transfer roller 422), whereby the toner images are electrostatically transferred onto intermediate transfer belt 421.

[0121] Thereafter, when the paper S passes through the secondary transfer nip, the toner image on the intermediate transfer belt 421 is secondarily transferred onto the paper S. Specifically, a secondary transfer bias is applied to the secondary transfer roller 424, and a charge of the opposite polarity to the toner is applied to the back side of the paper S (the side that abuts the secondary transfer roller 424), thereby electrostatically transferring the toner image onto the paper S. The paper S onto which the toner image has been transferred is transported towards the fixing unit 60.

[0122] Belt cleaning device 426 removes residual toner remaining on the surface of intermediate transfer belt 421 after secondary transfer. Intermediate transfer belt 421 is an endless belt that is looped and stretched around multiple support rollers 423. At least one of the support rollers 423 is a drive roller, and the others are driven rollers. For example, roller 423A, which is located downstream of primary transfer roller 422 for the K component in the belt running direction, is preferably the drive roller. This makes it easier to maintain a constant belt running speed in the primary transfer section. As roller 423A rotates, intermediate transfer belt 421 runs at a constant speed in the direction of arrow A (one direction).

[0123] The fixing section 60 has an upper fixing section 60A having a fixing surface side member arranged on the fixing surface side of the paper S (the surface on which a toner image is formed), a lower fixing section 60B having a back surface side support member arranged on the back surface side of the paper S (the surface opposite the fixing surface), and a heat source 60C. The back surface side support member is pressed against the fixing surface side member to form a fixing nip that holds and transports the paper S.

[0124] The fixing unit 60 fixes the toner image onto the paper S by applying heat and pressure to the conveyed paper S at a fixing nip after the toner image has been secondarily transferred. The fixing unit 60 is disposed as a unit inside the fixing device F. The fixing device F may also be provided with an air separation unit that blows air to separate the paper S from the fixing surface side member or the back surface side support member.

[0125] The paper transport section 50 has a paper feed section 51, a paper discharge section 52, and a transport path section 53. The three paper feed tray units 51a to 51c that make up the paper feed section 51 store paper S (standard paper, special paper) identified based on basis weight, size, etc., by pre-set type. The transport path section 53 has multiple transport roller pairs, such as a registration roller pair 53a.

[0126] The sheets S stored in the sheet feed tray units 51a to 51c are fed out one by one from the top, and are transported to the image forming unit 40 by the transport path unit 53. At this time, a registration roller unit having a registration roller pair 53a corrects the skew of the fed sheets S and adjusts the transport timing. Then, in the image forming unit 40, the toner image on the intermediate transfer belt 421 is secondarily transferred all at once onto one side of the sheets S, and a fixing process is performed in the fixing unit 60. The sheets S with the image formed thereon are discharged outside the apparatus by the sheet discharge unit 52 having a sheet discharge roller 52a.

[0127] (Image forming method) The image forming method of the present invention can be carried out in the same manner as known image forming methods, except that the toner and image forming apparatus described above are used. The image forming method of this embodiment includes a step of sending electrostatic image developing toner from a storage section to an image forming section, and a step of depositing the electrostatic image developing toner on a recording medium in the image forming section to form an image.

[0128] In the process of sending the toner for developing electrostatic images, the toner stored in the storage unit is sent to the photosensitive drum (image forming unit). In this embodiment, the toner stored in the storage unit is sent to the photosensitive drum by multiple developing rollers. At this time, the toner is cooled by the cooling unit. In this embodiment, the toner is cooled by cooling the inside of the container. The cooling temperature is preferably at least 20°C lower than the glass transition temperature of the toner for developing electrostatic images, and more preferably at least 30°C lower.

[0129] In the image forming process, toner is supplied to a photosensitive drum on which an electrostatic latent image has been formed, forming a toner image corresponding to the electrostatic latent image. Charged toner particles are electrostatically attached to the electrostatic latent image portion of the photosensitive drum. In this way, the electrostatic latent image on the surface of the photosensitive drum is visualized, and a toner image corresponding to the electrostatic latent image is formed on the surface of the photosensitive drum. In this embodiment, the term "toner image" refers to the state in which toner is aggregated in an image-like shape. Next, the toner image formed on the photosensitive drum is transferred to an intermediate transfer belt, and then the toner image transferred to the intermediate transfer belt is transferred to a recording medium.

[0130] The image forming method according to the present embodiment may include a process of fixing the toner image transferred onto the recording medium after the toner image has been transferred onto the recording medium. In this process, the recording medium is heated and pressurized in a fixing nip formed in the fixing unit, thereby fixing the toner image onto the recording medium.

[0131] (effect) In the image forming apparatus and image forming method of the present invention, the toner fed to the photosensitive drum is cooled, and therefore, the toner has excellent low-temperature fixability. [Example]

[0132] Examples of the present invention will be described below. The present invention is not limited to the following examples. In the following, when simply referring to "parts" and "%", they mean "parts by mass" and "% by mass", respectively.

[0133] <Synthesis of Ketimine Compounds> A reaction vessel equipped with a stirrer and a thermometer was charged with 170 parts of isophoronediamine and 75 parts of methyl ethyl ketone, and the mixture was reacted at 50°C for 5 hours to obtain a ketimine compound. The amine value of the ketimine compound was 418 mgKOH / g.

[0134] <Synthesis of amorphous polyester resin A-1> A four-neck flask equipped with a nitrogen inlet tube, dehydration tube, stirrer, and thermocouple was charged with the following components: The polyhydric alcohols, bisphenol A ethylene oxide di-adduct (BPA-EO), bisphenol A propylene oxide di-adduct (BPA-PO), 1,4 butanediol, and 1,6 hexanediol, were mixed in a molar ratio of 25 / 25 / 30 / 20; the polycarboxylic acids, terephthalic acid and trimellitic acid, were mixed in a molar ratio of 98 / 2; and the molar ratio of hydroxyl groups to carboxyl groups (OH mole % / COOH mole %) was 1.3. The mixture was then reacted with titanium tetraisopropoxide (500 ppm relative to the resin component) at atmospheric pressure and 230°C for 8 hours, followed by a further 4 hours at a reduced pressure of 10 to 15 mmHg. Next, trimellitic anhydride was added to the reaction vessel so that the amount was 1 mol % relative to the total resin components, and the mixture was reacted at normal pressure and 180°C for 3 hours to obtain amorphous polyester resin A-1. The molecular weight Mw of amorphous polyester resin A-1 was 30,000, and the glass transition temperature Tg was 45°C.

[0135] <Synthesis of amorphous polyester resin A-2> In the synthesis of amorphous polyester resin A-1, the molar ratio of polyhydric alcohols BPA-EO, BPA-PO, 1,4 butanediol, and 1,6 hexanediol was changed to 15 / 15 / 20 / 50. Furthermore, the molar ratio of polycarboxylic acid terephthalic acid to trimellitic acid was changed to 94 / 6. Amorphous polyester resin A-2 was obtained in the same manner. The molecular weight Mw of amorphous polyester resin A-2 was 28,000, and the glass transition temperature Tg was 46°C.

[0136] <Synthesis of amorphous polyester resin A-3> In the synthesis of amorphous polyester resin A-1, the molar ratio of polyhydric alcohols BPA-EO, BPA-PO, 1,4 butanediol, and 1,6 hexanediol was changed to 5 / 5 / 20 / 70. Furthermore, the molar ratio of polycarboxylic acid terephthalic acid to trimellitic acid was changed to 87 / 13. Amorphous polyester resin A-3 was obtained in the same manner. The molecular weight Mw of amorphous polyester resin A-3 was 30,000, and the glass transition temperature Tg was 43°C.

[0137] <Synthesis of amorphous polyester resin A-4> In the synthesis of amorphous polyester resin A-1, the molar ratio of polyhydric alcohol BPA-EO, BPA-PO, ethylene glycol, and 1,6-hexanediol was changed to 15 / 15 / 20 / 50. Furthermore, the molar ratio of polycarboxylic acid terephthalic acid and trimellitic acid was changed to 86 / 14, but the same procedure was used to obtain amorphous polyester resin A-4. The molecular weight Mw of amorphous polyester resin A-4 was 31,000, and the glass transition temperature Tg was 43°C.

[0138] <Synthesis of amorphous polyester resin A-5> In the synthesis of amorphous polyester resin A-1, the molar ratio of polyhydric alcohols BPA-EO, BPA-PO, 1,3 propanediol, and 1,6 hexanediol was changed to 15 / 15 / 20 / 50. Furthermore, the molar ratio of polycarboxylic acid terephthalic acid to trimellitic acid was changed to 86 / 14. Amorphous polyester resin A-5 was obtained in the same manner. The molecular weight Mw of amorphous polyester resin A-5 was 33,000, and the glass transition temperature Tg was 44°C.

[0139] <Synthesis of amorphous polyester resin A-6> In the synthesis of amorphous polyester resin A-1, the molar ratio of polyhydric alcohols BPA-EO, BPA-PO, 1,8 octanediol, and 1,10 decanediol was changed to 15 / 15 / 30 / 40. Furthermore, the molar ratio of polycarboxylic acid terephthalic acid to trimellitic acid was changed to 98 / 2. Amorphous polyester resin A-6 was obtained in the same manner. The molecular weight Mw of amorphous polyester resin A-6 was 31,000, and the glass transition temperature Tg was 51°C.

[0140] <Synthesis of amorphous polyester resin A-7> In the synthesis of amorphous polyester resin A-1, the molar ratio of the polyhydric alcohol was changed to 50 / 50 between 1,4 butanediol and 1,6 hexanediol. The molar ratio of the polycarboxylic acid was changed to 75 / 25 between terephthalic acid and trimellitic acid. Amorphous polyester resin A-7 was obtained in the same manner. The molecular weight Mw of amorphous polyester resin A-7 was 28,000, and the glass transition temperature Tg was 45°C.

[0141] <Synthesis of amorphous polyester resin A-8> In the synthesis of amorphous polyester resin A-1, the molar ratio of polyhydric alcohol BPA-EO to BPA-PO was changed to 50 / 50. Furthermore, the molar ratio of polycarboxylic acid terephthalic acid to trimellitic acid was changed to 87 / 13. Amorphous polyester resin A-8 was obtained in the same manner. The molecular weight Mw of amorphous polyester resin A-8 was 25,000, and the glass transition temperature Tg was 50°C.

[0142] <Synthesis of amorphous polyester resin A-9> In the synthesis of amorphous polyester resin A-1, the molar ratio of polyhydric alcohols BPA-EO, BPA-PO, 1,4 butanediol, and 1,6 hexanediol was changed to 30 / 30 / 10 / 30. Amorphous polyester resin A-9 was obtained in the same manner, except that the molar ratio of polycarboxylic acid terephthalic acid to trimellitic acid was changed to 100 / 0. The molecular weight Mw of amorphous polyester resin A-9 was 28,000, and the glass transition temperature Tg was 47°C.

[0143] <Preparation of Amorphous Polyester Dispersion A'-1> A container equipped with a stirring rod and thermometer was charged with 308 parts of amorphous polyester A-1 and 1,900 parts of ethyl acetate. The mixture was then heated to 80°C with stirring, maintained for 5 hours, and then cooled to 30°C over 1 hour. Next, a bead mill, Ultraviscomill (Imex Co., Ltd.), was used to fill the container with 80% by volume of zirconia beads with a diameter of 0.5 mm, and the mixture was dispersed under three passes to obtain amorphous polyester dispersion A'-1. The solids content of amorphous polyester dispersion A'-1 was 13.9%.

[0144] <Preparation of Amorphous Polyester Dispersions A'-2 to A'-9> Dispersions of amorphous polyesters A'-2 to A'-9 were obtained in the same manner as in the preparation of the dispersion of amorphous polyester A'-1, except that the amorphous polyester A-1 was changed to amorphous polyesters A-2 to A-9, respectively.

[0145] The amorphous polyester resin No., amorphous polyester resin dispersion No., and physical properties are shown in Tables 1 and 2.

[0146] [Table 1]

[0147] [Table 2]

[0148] <Synthesis of crystalline polyester resin C-1> A 5L four-neck flask equipped with a nitrogen inlet, dehydration tube, stirrer, and thermocouple was charged with a 50 / 50 molar ratio of ethylene glycol and 1,6-hexanediol as polyhydric alcohols, a 50 / 50 molar ratio of adipic acid and sebacic acid as polycarboxylic acids, and a 0.9 molar ratio of hydroxyl to carboxyl groups (OH / COOH). The mixture was reacted with titanium tetraisopropoxide (500 ppm of resin components) at 180°C for 10 hours, then heated to 200°C for 3 hours, and then further reacted at 8.3 kPa for 2 hours to obtain crystalline polyester resin C-1. The molecular weight (Mw) of crystalline polyester resin C-1 was 20,000, and the melting temperature (Tm) was 77°C.

[0149] <Synthesis of crystalline polyester resin C-2> Crystalline polyester resin C-2 was obtained in the same manner as in the synthesis of crystalline polyester resin C-1, except that the molar ratio of the polyhydric alcohol used was changed to 50 / 50 between 1,3-propanediol and 1,6-hexanediol. The molar ratio of the polycarboxylic acid used was also changed to 50 / 50 between adipic acid and sebacic acid. The molecular weight Mw of crystalline polyester resin C-2 was 21,000, and the melting temperature Tm was 75°C.

[0150] <Synthesis of crystalline polyester resin C-3> Crystalline polyester resin C-3 was obtained in the same manner as in the synthesis of crystalline polyester resin C-1, except that the molar ratio of the polyhydric alcohol used was changed to 50 / 50 between 1,3 propanediol and 3-methyl-1,5 pentanediol. The molar ratio of the polycarboxylic acid used was also changed to 50 / 50 between adipic acid and sebacic acid. The molecular weight Mw of crystalline polyester resin C-3 was 19,000, and the melting temperature Tm was 74°C.

[0151] <Synthesis of crystalline polyester resin C-4> Crystalline polyester resin C-4 was obtained in the same manner as in the synthesis of crystalline polyester resin C-1, except that the molar ratio of the polyhydric alcohol to ethylene glycol and 1,9-nonanediol was changed to 50 / 50. The molar ratio of the polycarboxylic acid to sebacic acid and dodecanedioic acid was also changed to 50 / 50. The molecular weight Mw of crystalline polyester resin C-4 was 20,000, and the melting temperature Tm was 78°C.

[0152] <Synthesis of crystalline polyester resin C-5> Crystalline polyester resin C-5 was obtained in the same manner as in the synthesis of crystalline polyester resin C-1, except that the molar ratio of polyhydric alcohol to ethylene glycol and 1,12-dodecanediol was changed to 50 / 50. The molar ratio of polycarboxylic acid to sebacic acid was also changed to 50 / 50. Crystalline polyester resin C-4 had a molecular weight Mw of 22,000 and a melting temperature Tm of 80°C.

[0153] <Synthesis of crystalline polyester resin C-6> In the synthesis of crystalline polyester resin C-1, the molar ratio of the polyhydric alcohol used was changed to 100, and the molar ratio of the polycarboxylic acid used was changed to 50 / 50, so that sebacic acid and succinic acid were used. Crystalline polyester resin C-6 was obtained in the same manner. The molecular weight Mw of crystalline polyester resin C-6 was 25,000, and the melting temperature Tm was 86°C.

[0154] <Preparation of Crystalline Polyester Dispersion C'-1> A vessel equipped with a stirring rod and a thermometer was charged with 308 parts of crystalline polyester C-1 and 1,900 parts of ethyl acetate. The mixture was then heated to 80°C with stirring, maintained at this temperature for 5 hours, and then cooled to 30°C over 1 hour. Next, a bead mill, Ultraviscomill (Imex Co., Ltd.), was used to fill the mixture with 0.5 mm diameter zirconia beads at 80% by volume, and the mixture was dispersed under three passes to obtain crystalline polyester dispersion C'-1. The solids content was 13.9%.

[0155] <Preparation of Crystalline Polyester Dispersions C'-2 to C'-6> Dispersions of crystalline polyesters C'-2 to C'-6 were obtained in the same manner as in the preparation of the crystalline polyester C'-1 dispersion, except that the crystalline polyester C-1 was replaced with crystalline polyesters C-2 to C-6, respectively.

[0156] Tables 3 and 4 show the crystalline polyester resin number, the crystalline polyester resin dispersion number, and the physical properties.

[0157] [Table 3]

[0158] [Table 4]

[0159] <Preparation of Masterbatch (MB-1)> 1200 parts of water, 500 parts of carbon black (Printex 35, manufactured by Degussa) (DBP oil absorption = 42 mL / 100 mg, pH = 9.5), and 500 parts of amorphous polyester resin A-1 were added and mixed in a Henschel mixer (Nippon Coke and Engineering Co., Ltd.). The resulting mixture was kneaded using a two-roll mill at 150°C for 30 minutes, then rolled and cooled, and pulverized in a pulverizer to obtain MB-1. The pigment solids content of MB-1 was 22.7%.

[0160] <Preparation of MB-2 to MB-9> In the preparation of MB-1, MB-2 to MB-9 were obtained in the same manner except that the amorphous polyester A-1 was changed to amorphous polyesters A-2 to A-9, respectively.

[0161] <Preparation of wax dispersion> In a container equipped with a stirrer and a thermometer, 42 parts of carnauba wax (Cerica Noda Co., Ltd., RN-5, plant-based wax, melting point 82°C) and 420 parts of ethyl acetate were charged as a mold release agent, heated to 80°C with stirring, and held at 80°C for 5 hours. Then, it was cooled to 30°C in 1 hour, and dispersion was carried out using a bead mill (Ultraviscomill, Imex Co., Ltd.) under the conditions of a liquid feeding rate of 1 kg / hr, a disk peripheral speed of 6 m / sec, 80% filling of zirconia beads with a diameter of 0.5 mm, and 3 passes to obtain a wax dispersion. The solid content of the WAX dispersion was 9.1%.

[0162] (Example 1) <Preparation of aqueous phase> 600 parts of water, 23.5 parts of a 48.5% aqueous solution of sodium dodecyl diphenyl ether disulfonate Ereminol MON-7 (Sanyo Chemical Industries, Ltd.), and 90 parts of ethyl acetate were mixed and stirred to obtain a milky white aqueous phase.

[0163] <Emulsification and desolventization> After adding 0.2 parts of a ketimine compound and 2000 parts of the aqueous phase to the container containing the oil phase, it was mixed at 13,000 rpm for 20 minutes using a TK homomixer to obtain Emulsion Slurry 1. Emulsion Slurry 1 was charged into a container equipped with a stirrer and a thermometer, desolventized at 30°C for 8 hours, and then aged at 45°C for 4 hours to obtain Dispersion Slurry 1.

[0164] <Washing, heat treatment, and drying> 100 parts of the dispersion slurry 1 were filtered under reduced pressure. Next, 100 parts of ion-exchanged water were added to the filter cake, and the mixture was mixed using a TK homomixer at 12,000 rpm for 10 minutes, followed by filtration (hereinafter referred to as washing step (1)). Furthermore, 100 parts of a 10% aqueous sodium hydroxide solution were added to the filter cake, and the mixture was mixed using a TK homomixer at 12,000 rpm for 30 minutes, followed by filtration under reduced pressure (hereinafter referred to as washing step (2)). Next, 100 parts of 10% hydrochloric acid were added to the filter cake, and the mixture was mixed using a TK homomixer at 12,000 rpm for 10 minutes, followed by filtration (hereinafter referred to as washing step (3)). Furthermore, 300 parts of ion-exchanged water were added to the filter cake, and the mixture was mixed using a TK homomixer at 12,000 rpm for 10 minutes, followed by filtration (hereinafter referred to as washing step (4)). At this time, the operations of washing steps (1) to (4) were repeated twice.

[0165] 100 parts of ion-exchanged water was added to the filter cake, and the mixture was mixed for 10 minutes at 12,000 rpm using a TK homomixer, heated for 4 hours at 50°C, and then filtered. The filter cake was then dried for 48 hours at 45°C using a circulating air dryer, and then sieved through a mesh with 75 μm openings to obtain toner base particles 1.

[0166] <External additive processing process> 100 parts of toner base particles 1 were mixed with 2.0 parts of hydrophobic silica (HDK-2000, Clariant Co., Ltd.) in a Henschel mixer, and the mixture was passed through a 500 mesh sieve to obtain toner 1.

[0167] Example 2 Emulsified slurry 2, dispersed slurry 2, toner base particles 2, and toner 2 were obtained in the same manner as in Example 1, except that MB-1 in Example 1 was changed to MB-2 and the amorphous polyester A'-1 dispersion was changed to the amorphous polyester A'-2 dispersion.

[0168] Example 3 Emulsified slurry 3, dispersed slurry 3, toner base particles 3, and toner 3 were obtained in the same manner as in Example 1, except that MB-1 in Example 1 was changed to MB-3 and the amorphous polyester A'-1 dispersion was changed to the amorphous polyester A'-3 dispersion.

[0169] Example 4 Emulsified slurry 4, dispersed slurry 4, toner base particles 4, and toner 4 were obtained in the same manner as in Example 1, except that MB-1 in Example 1 was changed to MB-4 and the amorphous polyester A'-1 dispersion was changed to the amorphous polyester A'-4 dispersion.

[0170] Example 5 Emulsified slurry 5, dispersed slurry 5, toner base particles 5, and toner 5 were obtained in the same manner as in Example 1, except that MB-1 in Example 1 was changed to MB-5 and the amorphous polyester A'-1 dispersion was changed to the amorphous polyester A'-5 dispersion.

[0171] Example 6 Emulsified slurry 6, dispersed slurry 6, toner base particles 6, and toner 6 were obtained in the same manner as in Example 2, except that the crystalline polyester C'-1 dispersion in Example 2 was changed to the crystalline polyester C'-2 dispersion.

[0172] Example 7 Emulsified slurry 7, dispersed slurry 7, toner base particles 7, and toner 7 were obtained in the same manner as in Example 2, except that the crystalline polyester C'-1 dispersion in Example 2 was changed to the crystalline polyester C'-3 dispersion.

[0173] Example 8 Emulsified slurry 8, dispersed slurry 8, toner base particles 8, and toner 8 were obtained in the same manner as in Example 2, except that the crystalline polyester C'-1 dispersion in Example 2 was changed to the crystalline polyester C'-4 dispersion.

[0174] Example 9 Emulsified slurry 9, dispersed slurry 9, toner base particles 9, and toner 9 were obtained in the same manner as in Example 2, except that the crystalline polyester C'-1 dispersion in Example 2 was changed to the crystalline polyester C'-5 dispersion.

[0175] Example 10 The amount of amorphous polyester A'-2 dispersion liquid used in Example 2 was changed from 2141 g to 1588 g, and the amount of crystalline polyester C'-1 dispersion liquid used was changed from 275 g to 828 g. Except for this, emulsified slurry 10, dispersed slurry 10, toner base particles 10, and toner 10 were obtained in the same manner as in Example 2.

[0176] Example 11 The amount of amorphous polyester A'-2 dispersion liquid used in Example 2 was changed from 2141 g to 2416 g, and the amount of crystalline polyester C'-1 dispersion liquid used was changed from 275 g to 0 g. Except for this, emulsified slurry 11, dispersed slurry 1, toner base particles 11, and toner 11 were obtained in the same manner as in Example 2.

[0177] Example 12 Toner 2 was used as the toner to verify different types of refrigerant in the cooling section.

[0178] Example 13 Emulsified slurry 12, dispersed slurry 12, toner base particles 12, and toner 12 were obtained in the same manner as in Example 1, except that MB-1 in Example 1 was changed to MB-6 and the amorphous polyester A'-1 dispersion was changed to the amorphous polyester A'-6 dispersion.

[0179] Example 14 Emulsified slurry 13, dispersed slurry 13, toner base particles 13, and toner 13 were obtained in the same manner as in Example 2, except that the crystalline polyester C'-1 dispersion in Example 2 was changed to the crystalline polyester C'-6 dispersion.

[0180] Example 15 Emulsified slurry 14, dispersed slurry 14, toner base particles 14, and toner 14 were obtained in the same manner as in Example 1, except that MB-1 in Example 1 was changed to MB-7 and the amorphous polyester A'-1 dispersion was changed to the amorphous polyester A'-7 dispersion.

[0181] (Comparative Example 1) Emulsified slurry 15, dispersed slurry 15, toner base particles 15, and toner 15 were obtained in the same manner as in Example 1, except that MB-1 in Example 1 was changed to MB-8 and the amorphous polyester A'-1 dispersion was changed to the amorphous polyester A'-8 dispersion.

[0182] (Comparative Example 2) Emulsified slurry 16, dispersed slurry 16, toner base particles 16, and toner 16 were obtained in the same manner as in Example 1, except that MB- in Example 1 was changed to MB-9 and amorphous polyester A-1 was changed to amorphous polyester A-9.

[0183] (Comparative Example 3) Toner 2 was used as the toner to verify the presence or absence of a cooling unit.

[0184] Tables 5 and 6 show the composition of each toner, the amount (mass %) of each material in the entire toner, and whether or not a cooling unit is provided.

[0185] [Table 5]

[0186] [Table 6]

[0187] <Low temperature fixability> For the low-temperature fixability, a commercially available copier "bizhub PRO C6550" (Konica Minolta, Inc.) was used as an image evaluation device, which had been modified so that the surface temperature of the heat-fixing roller (measured at the center of the roller) could be changed between 100 and 200°C. Each toner was installed, and the toner adhesion amount was measured on A4-size fine paper in an environment of normal temperature and humidity (temperature 20°C, humidity 50% RH) at 8 mg / cm. 2 A fixing experiment was conducted to fix a solid image of the above. The fixing temperature was increased in 1°C increments from 125°C up to 200°C. The lowest temperature in the fixing experiment at which image staining due to low-temperature offset was not visually observed was evaluated as the minimum fixing temperature (UO / under-offset). The minimum fixing temperature was evaluated according to the following criteria. A minimum fixing temperature (UO / under-offset) of less than 140°C was considered to be acceptable. ◎: Less than 130℃ 〇: 130 to less than 135℃ △: 135 to less than 140℃ ×: 140℃ or higher

[0188] After the minimum fixing temperature was determined, the same image (toner adhesion amount 8 mg / cm 2 After 5,000 continuous prints of the same image (solid image), the minimum fixing temperature (UO / under offset) was measured again to evaluate the fluctuation in fixability. The fluctuation in fixability was evaluated according to the following criteria. A minimum fixing temperature change of 2°C or less was considered to be acceptable. ○: The change is 2°C or less ×: The change is more than 2°C

[0189] <Folding fixation> The fixing device of the multifunction printer "bizhub PRESS (registered trademark) C1070" (Konica Minolta, Inc.) was modified to be able to change the surface temperatures of the upper fixing belt and the lower fixing roller, and two-component developers were loaded sequentially. The device was also modified to be able to freely set the fixing temperature, toner adhesion amount, and system speed. Under normal temperature and humidity conditions (temperature 20°C, humidity 50% RH), A4 size high-quality paper "NPI high-quality (127.9 g / m 2) (Nippon Paper Industries Co., Ltd.) with a deposition rate of 11.3 g / m 2 A fixing experiment was carried out to output a solid image of 100°C. The fixing temperature was increased from 100°C to 200°C in increments of 5°C. Next, the prints obtained in the fixing experiments at each fixing temperature were subjected to a folding machine with a pressure of 10 g / cm 2 The sheet was folded under a considerable weight load so that the solid images would contact each other, forming a valley fold, and compressed air of 0.35 MPa was blown onto the sheet. The fold fixability was evaluated according to the following criteria. 5: No creases at all 4: Some peeling along the fold 3: Fine linear peeling along the fold 2: Thick linear peeling along the fold 1: Large peeling along the fold The lowest fixing temperature in the fixing experiment among the images that were ranked 3 or higher was determined as the minimum fixing temperature. The fold fixability was evaluated according to the following evaluation criteria. A minimum fixing temperature of 145°C or higher was determined to be acceptable. 〇: Less than 145℃ △: 145 or more and 150℃ or less × : 150 or more

[0190] <Heat-resistant storage> 0.5 g of each toner was 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 Tap Denser KYT-2000 (Seishin Enterprise Co., Ltd.). The bottle was then left with the lid removed for 2 hours at three different temperatures: 57.5°C, 60.0°C, and 62.5°C, and at 35% RH. Each toner was then placed on a 48-mesh (350 μm mesh) sieve, taking care not to break up the toner aggregates, and placed in a powder tester (Hosokawa Micron Corporation). The sieve was then secured with a pressure bar and knob nut, and the vibration intensity was adjusted to a feed width of 1 mm. After 10 seconds of vibration, the percentage of the toner remaining on the sieve (mass %) was measured. The toner cohesion ratio was calculated using the following formula: Toner cohesion rate (%) = mass of toner remaining on sieve (g) / 0.5 (g) x 100 The toner aggregation rate was measured at the above three temperature levels, and the temperature at which the aggregation rate reached 50% was estimated and designated as the 50% aggregation temperature. The heat-resistant storage stability (50% aggregation temperature) of the toner was evaluated according to the following criteria. A 50% aggregation temperature of 56°C or higher was deemed to be acceptable. ◎: 60℃ or higher 〇: 58 to less than 60℃ △: 56 to less than 58°C ×: Less than 56℃

[0191] The toner numbers and the evaluation results are shown in Table 7.

[0192] [Table 7]

[0193] In Examples 1 to 15, in which the electrostatic image developing toner contained a crystalline substance and the image forming apparatus had a cooling unit, the low-temperature fixing property was good. This is thought to be because the temperature rise of the electrostatic image developing toner in the image forming apparatus was suppressed. In particular, the low-temperature fixability, fixability fluctuation, fold fixability, and heat-resistant storage stability were all good in Examples 4 to 7. This is thought to be because the content of structural units derived from bisphenol A derivatives was 30 mol %, and the carbon numbers of the aliphatic alcohols contained in the amorphous polyester resin and the crystalline polyester resin were both within the range of 2 to 6.

[0194] On the other hand, in Comparative Examples 1 and 2, in which the content of structural units derived from bisphenol A derivatives was not within the predetermined range, the low-temperature fixability or heat-resistant storage stability was poor. This is thought to be because the viscosity did not decrease easily when heated during fixation, or the glass transition temperature increased. Furthermore, in Comparative Example 3, in which the image forming apparatus did not have a cooling unit, the low-temperature fixing property was poor. This is thought to be because the temperature of the electrostatic image developing toner rose in the image forming apparatus. [Industrial Applicability]

[0195] According to the present invention, an image forming apparatus and an image forming method that are excellent in low-temperature fixing ability are provided. [Explanation of symbols]

[0196] 1. Image forming device 10 Image reading unit 11 Automatic document feeder 12 Original image scanning device 12a CCD sensor 20 Operation display section 21 Display section 22 Control section 30 Image processing section 35a container 35b Stirring roller 35c developing roller 35d cooling fan 35e exhaust fan 40 Image forming unit 41Y, 41M, 41C, 41K Image forming units 42 Intermediate transfer unit 50 Paper transport section 51 Paper feed section 51a~51c Paper feed tray unit 52a Paper ejection roller 53a Registration roller 52 Paper ejection section 53 Conveying path section 60 Fixing unit 60A Upper fixing part 60C heating source 60B Lower fixing part 411 Exposure equipment 412 Development Unit 413 Photosensitive drum 414 Charging device 415 Drum cleaning device 416 Cooling section 421 Intermediate transfer belt 422 Primary transfer roller 423 Support Roller 423 423A Roller 423B Backup Roller 424 Secondary transfer roller 426 Belt Cleaning D Manuscript S Paper (recording medium)

Claims

1. An image forming apparatus for forming an image using a toner for developing an electrostatic image, a developing section that stores the toner for developing an electrostatic image and develops an electrostatic latent image formed on the surface of an electrophotographic photosensitive member to form a toner image; a cooling unit for cooling the toner for developing an electrostatic image, the toner for developing electrostatic images contains an amorphous polyester resin which is a polycondensate of a polycarboxylic acid and a polyhydric alcohol, and the amorphous polyester resin contains structural units derived from bisphenol A derivatives in an amount of 50 mol % or less relative to 100 mol % of all structural units derived from polyhydric alcohols; Image forming device.

2. The image forming apparatus according to claim 1 , wherein the cooling section cools the developing section.

3. 2. The image forming apparatus according to claim 1, wherein the content of the structural unit derived from the bisphenol A derivative in the amorphous polyester resin is 10 mol % or more relative to 100 mol % of the structural unit derived from the first polyhydric alcohol.

4. 2. The image forming apparatus according to claim 1, wherein the content of the structural unit derived from the bisphenol A derivative in the amorphous polyester resin is in the range of 20 to 40 mol % or less relative to 100 mol % of the structural unit derived from the first polyhydric alcohol.

5. The image forming apparatus according to claim 1 , wherein the first polyhydric alcohol includes an aliphatic polyhydric alcohol having 2 to 6 carbon atoms.

6. 2. The image forming apparatus according to claim 1, wherein the first polyhydric alcohol includes ethylene glycol or 1,3 propanediol.

7. 2. The image forming apparatus according to claim 1, wherein the toner for developing an electrostatic image further contains a crystalline polyester resin.

8. 8. The image forming apparatus according to claim 7, wherein the content of the crystalline polyester resin in the electrostatic image developing toner is within a range of 2 to 30% by mass.

9. the crystalline polyester resin is a polycondensate of a second polycarboxylic acid and a second polyhydric alcohol, the second polyhydric alcohol comprises an aliphatic alcohol; the number of carbon atoms of the second polycarboxylic acid and the number of carbon atoms of the aliphatic alcohol are both within the range of 2 to 12; The image forming apparatus according to claim 7 .

10. 2. The image forming apparatus according to claim 1, wherein the cooling section cools the toner for developing the electrostatic image with an aqueous solution of ethylene glycol.

11. 2. The image forming apparatus according to claim 1, wherein the cooling section cools the toner for developing the electrostatic image with air.

12. An image forming method using the image forming apparatus according to claim 1, a step of delivering the electrostatic image developing toner to the surface of an electrophotographic photoreceptor; a step of storing the toner for developing an electrostatic image and developing an electrostatic latent image formed on the surface of an electrophotographic photosensitive member to form a toner image; and In the step of feeding the toner to the surface of the electrophotographic photosensitive member, the toner for developing an electrostatic image is cooled by the cooling unit. Image forming method.

Images