Image forming method

Abstract

To provide an image forming method with which image peeling can be prevented, which is caused by bending of a toner image during take-up of a long-sized medium.SOLUTION: An image forming method of the present invention uses a toner for electrostatic latent image development including toner particles having an external additive on a surface of a toner base particle, and a long-sized medium. The number-based median diameter of the external additive is within a range of 60-400 nm. The external additive is contained in an amount of 0.3 mass% or less relative to the toner base particle. The air permeability of the long-sized medium is 20000 sec or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an image forming method, and more particularly to an image forming method that can suppress image peeling caused by a toner image being curved when a long medium is wound up. [Background technology]

[0002] A printing technology using long media is disclosed, for example, in Patent Document 1. In the technology of Patent Document 1, a phenolic resin is used as the binder resin constituting the toner to impart toughness to the rolled printed matter in order to prevent image deterioration even if deformation is applied during post-processing. Furthermore, a technology for fixing toner to plastic media is disclosed, for example, in Patent Document 2. The technology in Patent Document 2 addresses the problem of toner printed on a film being rubbed off, by designing the SP value of the crystalline polyester in the toner and the surface tension of the media, thereby improving the adhesion of the toner to plastic media.

[0003] Furthermore, the speed at which long media is wound up is also increasing to improve productivity, which can cause image distortion due to the toner image being curved when the long media is wound up. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-203964 [Patent Document 2] Japanese Patent Publication No. 2022-54448 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention was made in consideration of the above problems and circumstances, and its problem to be solved is to provide an image forming method that can suppress image peeling caused by the toner image curving when winding up long media. [Means for solving the problem]

[0006] The present inventors have investigated the causes of the above problems in order to solve the above problems, and have found that by using long media with high air permeability and a small amount of external additive with large particle diameters, it is possible to suppress image peeling caused by the toner image bending when the long media is wound up. That is, the above-mentioned problems of the present invention are solved by the following means.

[0007] 1. An image forming method using a toner for developing an electrostatic latent image, which includes toner particles having an external additive on the surface of the toner base particles, and a long medium, the external additive has a number-based median diameter within a range of 60 to 400 nm, and the external additive is contained in an amount of 0.3% by mass or less relative to the toner base particles; The air permeability of the long media is 20,000 sec or more. An image forming method comprising:

[0008] 2. The average coverage S of the external additive in the toner particles determined by image analysis using a scanning electron microscope is 3% by area or less. 2. The image forming method according to claim 1,

[0009] 3. The thickness of the long media is within the range of 20 to 80 μm. 2. The image forming method according to claim 1,

[0010] 4. The toner base particles contain styrene-acrylic resin and polyester. 2. The image forming method according to claim 1,

[0011] 5. The Young's modulus of the image formed on the long medium is within the range of 1.5 to 3.0 MPa. 2. The image forming method according to claim 1,

[0012] 6. The external additive contains silica particles or titania particles. 2. The image forming method according to claim 1, [Effects of the Invention]

[0013] The above-described means of the present invention can provide an image forming method that can suppress image peeling caused by the toner image being curved when the long medium is wound up. The mechanism by which the effects of the present invention are manifested or the mechanism of action is not clear, but is speculated as follows. In the image forming method of the present invention, the median diameter of the external additive based on the number is set to be within the range of 60 to 400 nm, the external additive is contained in an amount of 0.3 mass % or less relative to the toner base particles, and further, the air permeability of the long medium is set to be 20,000 sec or more. This makes it difficult for the air between the toner particles to escape when the toner is fixed, due to the high air permeability of the long media. Furthermore, by combining such long media with a small amount of external additive with a large particle size, it is possible to leave voids in the image after the toner is fixed. The voids in the image disperse external forces, making the image less susceptible to deformation, which means that peeling of the toner image due to bending when the long medium is wound up can be suppressed. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram illustrating an example of the overall configuration of an image forming apparatus. [Figure 2] A diagram showing the main parts of a control system of an image forming apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0015] The image forming method of the present invention is an image forming method using a toner for developing an electrostatic latent image, which includes toner particles having an external additive on the surface of the toner base particles, and a long medium, characterized in that the median diameter based on the number of the external additives is within a range of 60 to 400 nm, the external additives are contained in an amount of 0.3 mass % or less relative to the toner base particles, and the air permeability of the long medium is 20,000 sec or more. This feature is a technical feature common to or corresponding to each of the following embodiments.

[0016] In an embodiment of the present invention, it is preferable that the average coverage S of the external additive in the toner particles, which is determined by image analysis using a scanning electron microscope, is 3 area % or less, which allows voids to remain in the image after fixing, and the voids in the image disperse external forces, making the image less likely to deform.

[0017] It is preferable that the thickness of the long medium is within the range of 20 to 80 μm, since this covers all general-purpose long media and allows images to be obtained without poor fixing.

[0018] The toner base particles preferably contain styrene-acrylic resin and polyester. Polyester has many polar groups, which allows it to easily release accumulated charge. Therefore, the higher the polyester content in the toner base particles, the more electrostatic attraction is suppressed, and blocking is reduced. However, toner base particles made only of polyester are negatively charged on contact with media such as polypropylene. If this contact charge becomes excessively large, even though the polyester charge decays, the residual charge increases, leading to blocking. Therefore, by using a styrene-acrylic resin, which has the property of being positively charged, the maximum contact charge can be reduced.

[0019] It is preferable that the Young's modulus of the image formed on the long medium is within the range of 1.5 to 3.0 MPa, since this prevents image breakage and allows the formation of an image with excellent gloss.

[0020] The external additive preferably contains silica particles or titania particles in view of excellent stability of the charge amount.

[0021] The present invention, its components, and embodiments and modes for carrying out the present invention will be described below. In this application, the symbol "to" is used to mean that the numerical values ​​before and after it are included as lower and upper limits.

[0022] [Outline of the image forming method of the present invention] The image forming method of the present invention is an image forming method using a toner for developing an electrostatic latent image, which includes toner particles having an external additive on the surface of the toner base particles, and a long medium, characterized in that the median diameter based on the number of the external additives is within a range of 60 to 400 nm, the external additives are contained in an amount of 0.3 mass % or less relative to the toner base particles, and the air permeability of the long medium is 20,000 sec or more. This feature is a technical feature common to or corresponding to each of the following embodiments.

[0023] In this specification, the term "toner" refers to a toner for developing an electrostatic latent image. The toner includes toner particles having toner base particles and an external additive disposed on the surface of the toner base particles. "Toner base particles" are the components that make up the base of "toner particles." "Toner base particles" are called "toner particles" when external additives are added. "Toner" refers to an aggregate of toner particles. The term "toner image" refers to a state in which toner is collected in an image shape.

[0024] <Median diameter based on number of external additives> In the present invention, the median diameter of the external additives based on the number of particles is within a range of 60 to 400 nm, and more preferably within a range of 80 to 200 nm. In addition, when the external additive has been subjected to hydrophobic treatment, the median diameter is assumed to be unchanged before and after the hydrophobic treatment. One way to achieve this median diameter within the above range is to control the addition rate of a hydrolysis solution containing tetramethoxysilane (TMOS) added to an alkaline catalyst in the sol-gel process for producing inorganic particles as an external additive. Another method is to control the amount of alkaline catalyst added to TMOS. The addition rate of the hydrolysis solution is preferably within the range of 5.0 to 8.5 mL / min. The method for measuring the median diameter based on the number of external additives will be described later.

[0025] <Average coverage rate of external additives S> The average coverage S of the external additive in the toner particles, determined by image analysis using a scanning electron microscope, is preferably 3% by area or less, and more preferably within the range of 1.5 to 2.5% by area. The average coverage S can be adjusted to 3% by area or less by controlling the median diameter of the external additives based on the number of particles and the amount of the external additives added. The specific ranges of the median diameter and amount of the external additives added are as described above.

[0026] Hereinafter, a method for measuring the median diameter and average coverage S based on the number of external additives will be described. The average coverage rate S of the external additives and the median diameter on a number basis were measured using a scanning electron microscope (SEM) S-4800 (manufactured by Hitachi, Ltd.) The area ratio of the portion derived from the external additives was calculated from image processing of mainly high-brightness portions at an accelerating voltage of 2.0 kV.

[0027] Specifically, the toner was first fixed in one layer on a specimen stage for electron microscope observation with carbon tape, platinum was vapor-deposited, and the toner was observed under the following conditions with a scanning electron microscope S-4800 (manufactured by Hitachi, Ltd.). The observation was performed after a flushing operation. SignalName=SE(U,LA80) AcceleratingVoltage=2000Volt EmissionCurrent=10000nA Working Distance=6000um LensMode=High Condenser1=5 ScanSpeed=Slow4(40 seconds) Magnification=50000 DataSize=1280×960 ColorMode=Grayscale

[0028] The secondary electron image was obtained by adjusting the brightness to 'Contrast 5, Brightness -5' on the control software of the scanning electron microscope S-4800, and obtaining a projection image of the toner as an 8-bit, 256-level grayscale image with an image size of 1280 x 960 pixels, with the capture speed / accumulation number set to 'Slow 4 for 40 seconds'. Next, using the obtained secondary electron projection image, the area ratio (area %) of the portion derived from the inorganic fine particles, which are external additives, was calculated for 100 toner particles. Details of the method for selecting 100 toner particles to analyze will be described later. The area % of the portion derived from the inorganic fine particles was calculated using image processing software Image-Pro Plus 5.1J (manufactured by Media Cybernetics).

[0029] Next, the toner particle clusters were extracted and the size of each extracted toner particle was counted. Specifically, first, to extract the toner particle clusters to be analyzed, the toner particle clusters were separated from the background. In Image-Pro Plus 5.1J, "Measurement" - "Count / Size" was selected. In "Count / Size," "Brightness Range Selection" was set to a brightness range of 50 to 255, and the low-brightness carbon tape portion that was visible in the background was excluded, allowing the toner particle clusters to be extracted. When the toner particles are fixed by a method other than carbon tape, the background may not necessarily have a low brightness, or it may be possible that some areas have the same brightness as the toner particles. However, the boundary between the toner particles and the background can be easily distinguished from the secondary electron observation image. When performing the extraction, in the "Count / Size" extraction options, "4-connected" was selected, smoothness "5" was entered, and "Fill holes" was checked, so that toner particles located on all boundaries (outer peripheries) of the image and toner particles overlapping with other toner particles were excluded from the calculation.

[0030] Next, in the "Count / Size" measurement items, area and Feret diameter (average) were selected, and the area selection range was set to a minimum of 100 pixels and a maximum of 10,000 pixels, and each toner particle was extracted for image analysis. One toner particle was selected from the extracted toner particle group, and the size ja1 (number of pixels) of the part originating from that particle was calculated.

[0031] Next, in Image-Pro Plus 5.1J's "Count / Size" "Brightness Range Selection," we set the brightness range to 140 to 255, and extracted the high-brightness areas on individual toner particles. By setting the area selection range to a minimum of 1 pixel and a maximum of 200 pixels, we were able to extract the high-brightness areas originating from inorganic fine particles. Then, for the toner particles selected when calculating ja1, the size ma1 (number of pixels) of the area on the toner surface that originates from inorganic fine particles was calculated. In each toner particle, the extracted areas that originate from inorganic fine particles will be scattered and have a certain size, and ma1 is their total area. Using the calculated ma1, the coverage rate s of the inorganic fine particles was calculated using the following formula. s=(ma1 / ja1)×100

[0032] Next, the same process was performed on each particle in the extracted particle group until the number of selected toner particles reached 100. If the number of toner particles in one field of view was less than 100, the same process was repeated for the toner projection image in another field of view. The average value of the coverage ratios s of the 100 toner particles obtained was taken as the average coverage ratio S according to the present invention. In addition, all of the inorganic fine particles in 100 particles of the obtained toner particles were arranged in ascending order of the diameter of a circle equivalent to the projected area, and the diameter of a circle equivalent to the projected area of ​​half of the inorganic fine particles was determined as the median diameter (D50 ) was decided. When external additives other than inorganic particles were present, the inorganic particles were identified based on their shape and size (particles 50 nm or larger). The median diameter and average coverage S of the external additives based on their number can be determined by observing secondary electron images using a scanning electron microscope and subsequent image processing.

[0033] <Air permeability of long media> In the present invention, the air permeability of the long medium is 20,000 sec or more, and preferably within the range of 21,000 to 30,000 sec. Air permeability is an index that indicates the resistance of a recording medium to the passage of air. Air permeability is related to the density, texture, water absorption, and printability of the recording medium, and can be used as a measure of the porous structure of the recording medium. Air permeability is a value measured according to JIS P8117 (revised in 2009). Air permeability is the value at which 100 ml of air passes through a hole of 6.42 cm under a constant pressure. 2 It is defined as the time it takes for air to pass through an area of ​​1000m2. Therefore, a large air permeability value means that it takes longer for air to pass through, meaning that breathability is low. Conversely, a small air permeability value means that breathability is high. In this way, there is an inverse relationship between the air permeability value and breathability.

[0034] The air permeability is measured using an Oken type air permeability meter (manufactured by Kumagai Riki Kogyo Co., Ltd.) as follows. First, start up the air permeability meter and adjust the measurement standard pressure to 500 mmH2O. Cut the paper to A4 size and set the cut sample in the measurement section. The paper should be set with the printed side (front) facing up. Flip the switch on the air permeability meter to the start side. Record the number of seconds calculated by the air permeability meter. This measurement is carried out three times using different cut samples, and the average value is taken as the air permeability [sec].

[0035] The long medium having an air permeability of 20,000 sec or more may be, for example, a film label or a film. A film label refers to a label with a release paper attached, while a film refers to a label with neither a release paper nor an adhesive attached.

[0036] (film) Examples of the film and film portion of the film label having an air permeability of 20,000 sec or more include polypropylene film, polyethylene film, polyvinyl chloride film, polyethylene terephthalate film, polystyrene film, polyester film, polylactic acid film, etc. Among these, polypropylene film or polyethylene terephthalate film is preferred from the viewpoint of versatility, etc.

[0037] Polypropylene films and polyethylene terephthalate films are used for various labels, packages, etc. The polypropylene films and polyethylene films may be subjected to appropriate surface treatment in order to improve printability. The polypropylene film and the polyethylene terephthalate film may be transparent. Furthermore, the polypropylene film and the polyethylene terephthalate film may contain a pigment or the like in the film, and may have any color such as white, and may have a toner-receiving layer formed on the surface.

[0038] The thickness of the long media such as the film or film label is preferably within the range of 20 to 80 μm, since this covers all general-purpose long media and allows for the production of images that do not suffer from fixing problems.

[0039] <Young's modulus> In the image forming method of the present invention, the Young's modulus of the image formed on the long medium is preferably within a range of 1.5 to 3.0 MPa, and more preferably within a range of 2.0 to 2.5 MPa. If the Young's modulus of the image is high, the image becomes more susceptible to cracking, whereas if the Young's modulus is low, the gloss of the image surface deformed by the pressure when the image is wound up will decrease. Therefore, the Young's modulus is preferably within the above range.

[0040] The Young's modulus is measured using a Hysitron TI-980 (manufactured by Bruker Japan Co., Ltd.) as follows. First, to prepare a measurement sample, a toner is produced according to each production method, and a fixed image is produced by the image forming method described below. After cutting the image sample into 5 mm pieces, apply correction fluid to a glass slide and adhere the image sample to it. Similarly, use correction fluid to adhere the image sample to the equipment stage. Wait at least 30 minutes for the sample to solidify before measuring. Next, the sample is mounted on a sample stage, and measurement is started under nanoindentation conditions at room temperature using a Berkovich-type diamond indenter (TI-0283: angle 142.3°). Before starting the measurement, the focus of the measurement sample is set and the measurement is carried out under uniform focus conditions. The focus of the measurement sample is set using a microscope in the software, and the sample position where the focus is achieved is registered. Next, measurements are carried out under the following conditions. Maximum load = 3mN Time to press = 10 seconds Press and hold time = 5 seconds Unloading time = 10 seconds Each sample is measured five times. Young's modulus Er (GPa) is calculated from the measurement results, and the average value of the five measurement data is taken as the Young's modulus of the sample.

[0041] As a means for adjusting the Young's modulus to be within the range of 1.5 to 3.0 MPa, for example, styrene-acrylic resin and polyester may be contained in the toner base particles, as will be described later.

[0042] [Toner composition] The composition of the toner will be described below. The toner includes toner particles having toner base particles and an external additive added to the surface of the toner base particles.

[0043] <Toner base particles> The toner base particles contain at least a binder resin, and may also contain other components such as a colorant, a release agent (wax), and a charge control agent, if necessary.

[0044] (binder resin) The binder resin binds the toner to the recording medium. The binder resin preferably contains a styrene-acrylic resin and a polyester. The composition ratio (mass %) of the styrene-acrylic resin to the polyester in the binder resin (styrene-acrylic resin:polyester) is preferably within a range of 80:20 to 1:99, and more preferably within a range of 60:40 to 5:95. It is not preferable that the binder resin contains a mixture of resins other than styrene-acrylic resin and polyester. There is no restriction on the use of crystalline or amorphous resins in polyester.

[0045] In the present invention, an "amorphous" resin is defined as a resin that does not exhibit a clear endothermic peak when subjected to differential scanning calorimetry (DSC). An amorphous resin is a resin that has a relatively high glass transition temperature.

[0046] Styrene-acrylic resin Examples of monomers for preparing styrene-acrylic resins include the following, which can be used alone or in combination of two or more:

[0047] (1) Styrene-based monomers Examples of styrene-based monomers include monomers having a styrene structure, such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, and derivatives thereof.

[0048] (2) (Meth)acrylic acid ester monomers Examples of (meth)acrylic acid ester monomers include monomers having a (meth)acrylic group, such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isopropyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, phenyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, and derivatives thereof. Among these, the use of methyl methacrylate is preferable, and this can be a means for solving the problems of the present invention.

[0049] "polyester" The polyester can be produced in either an amorphous or crystalline form, and both are applicable to the present invention.

[0050] <Amorphous polyester> It is a polyester resin exhibiting amorphous properties, obtained by the polymerization reaction of a divalent or higher carboxylic acid (polycarboxylic acid) monomer and a divalent or higher alcohol (polyalcohol) monomer. Amorphous polyester can be formed by polymerizing (esterifying) the polycarboxylic acid monomer and the polyalcohol monomer using a known esterification catalyst.

[0051] The polycarboxylic acid monomer is a compound containing two or more carboxy groups in one molecule. Examples of polycarboxylic acid monomers that can be used in the synthesis of amorphous polyesters include phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, naphthalene-2,6-dicarboxylic acid, malonic acid, mesaconic acid, dimethyl isophthalate, fumaric acid, dodecenylsuccinic acid, 1,10-dodecanedicarboxylic acid, etc. Among these, dimethyl isophthalate, terephthalic acid, dodecenylsuccinic acid, and trimellitic acid are preferred.

[0052] A polyhydric alcohol monomer is a compound containing two or more hydroxy groups in one molecule. Examples of polyhydric alcohol monomers that can be used in the synthesis of amorphous polyesters include dihydric or trihydric alcohols such as ethylene glycol, propylene glycol, 1,4-butanediol, 2,3-butanediol, diethylene glycol, triethylene glycol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, ethylene oxide adduct of bisphenol A (BPA-EO), propylene oxide adduct of bisphenol A (BPA-PO), glycerin, sorbitol, 1,4-sorbitan, and trimethylolpropane. Of these, the ethylene oxide adduct of bisphenol A and the propylene oxide adduct of bisphenol A are preferred.

[0053] Examples of the usable esterification catalyst include alkali metal compounds such as sodium and lithium; alkaline earth metal compounds such as magnesium and calcium; metal compounds such as aluminum, zinc, manganese, antimony, titanium, tin, zirconium, and germanium; phosphorous compounds; phosphoric acid compounds; and amine compounds. The polymerization temperature is not particularly limited, but is preferably 150 to 250° C. The polymerization time is not particularly limited, but is preferably 0.5 to 10 hours. During the polymerization, the reaction system may be reduced in pressure as needed.

[0054] <Crystalline polyester> In the present invention, the crystalline resin is not limited as long as it is a resin that exhibits crystallinity, and any known crystalline resin can be used. The term "crystalline resin" means that the endothermic curve obtained by DSC shows a clear endothermic peak at the melting point, i.e., during heating, rather than a stepwise endothermic change. It is preferable to use a crystalline polyester as the crystalline material, which can also function as a binder resin. The crystalline polyester used in the present invention is obtained by a polycondensation reaction between a divalent or higher carboxylic acid (a polycarboxylic acid) and a divalent or higher alcohol (a polyhydric alcohol).

[0055] Examples of the polycarboxylic acid include dicarboxylic acids. The dicarboxylic acid may be one or more kinds, and is preferably an aliphatic dicarboxylic acid, and may further contain an aromatic dicarboxylic acid. The aliphatic dicarboxylic acid is preferably a linear type from the viewpoint of enhancing the crystallinity of the crystalline polyester.

[0056] Examples of the aliphatic dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, 1,11-undecanedicarboxylic acid, 1,12-dodecanedicarboxylic acid (dodecanedioic acid), 1,13-tridecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,16-hexadecanedicarboxylic acid, 1,18-octadecanedicarboxylic acid, lower alkyl esters thereof, and acid anhydrides thereof. Among these, aliphatic dicarboxylic acids having 6 to 16 carbon atoms are preferred, and aliphatic dicarboxylic acids having 10 to 14 carbon atoms are more preferred, from the viewpoint of easily achieving both low-temperature fixability and transferability.

[0057] Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, orthophthalic acid, t-butylisophthalic acid, 2,6-naphthalenedicarboxylic acid, and 4,4'-biphenyldicarboxylic acid. Among these, terephthalic acid, isophthalic acid, and t-butylisophthalic acid are preferred from the viewpoints of availability and ease of emulsification. In order to ensure sufficient crystallinity of the crystalline polyester, the content of the aliphatic dicarboxylic acid-derived structural units relative to the dicarboxylic acid-derived structural units is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, and particularly preferably 100 mol%.

[0058] Examples of the polyhydric alcohol component include a diol. The diol may be one or more kinds, and is preferably an aliphatic diol, and may further contain other diols. The aliphatic diol is preferably a linear type from the viewpoint of increasing the crystallinity of the crystalline polyester. Examples of the aliphatic diol include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,18-octadecanediol, and 1,20-eicosanediol. Among these, from the viewpoint of easily achieving both low-temperature fixability and transferability, aliphatic diols having 2 to 12 carbon atoms are preferred, and aliphatic diols having 4 to 6 carbon atoms are more preferred. Examples of the other diols include diols having a double bond and diols having a sulfonic acid group.Specific examples of the diols having a double bond include 2-butene-1,4-diol, 3-butene-1,6-diol, and 4-butene-1,8-diol. The crystalline polyester can be synthesized by polycondensing (esterifying) the above polycarboxylic acid and polyhydric alcohol using a known esterification catalyst.

[0059] The catalyst that can be used in the synthesis of the crystalline polyester may be one or more types, and examples thereof include alkali metal compounds such as sodium and lithium; compounds containing Group 2 elements such as magnesium and calcium; metal compounds such as aluminum, zinc, manganese, antimony, titanium, tin, zirconium, and germanium; phosphorous compounds; phosphoric acid compounds; and amine compounds. Specifically, examples of tin compounds include dibutyltin oxide, tin octoate, tin dioctoate, and salts thereof. Examples of titanium compounds include titanium alkoxides such as tetra-n-butyl titanate, tetraisopropyl titanate, tetramethyl titanate, and tetrastearyl titanate; titanium acylates such as polyhydroxytitanium stearate; and titanium chelates such as titanium tetraacetylacetonate, titanium lactate, and titanium triethanolamine. Examples of germanium compounds include germanium dioxide, and examples of aluminum compounds include oxides such as polyaluminum hydroxide, aluminum alkoxides, and tributylaluminate.

[0060] (coloring agent) A colorant can be added to the toner base particles, and known colorants can be used as the colorant. Specifically, colorants contained in the yellow toner include, for example, CI Solvent Yellow 19, 44, 77, 79, 81, 82, 93, 98, 103, 104, 112, and 162, CI Pigment Yellow 14, 17, and 74, 93, 94, 138, 155, 180, 185, etc. These may be used alone or in combination of two or more.

[0061] Examples of colorants contained in magenta toners include CI Solvent Red 1, 49, 52, 58, 63, 111, and 122, CI Pigment Red 5, 48:1, 53:1, 57:1, 122, 139, 144, 149, 166, 177, 178, and 222. These may be used alone or in combination of two or more. Examples of colorants contained in cyan toners include CI Pigment Blue 15:3.

[0062] Examples of colorants contained in black toner include carbon black, magnetic materials, and titanium black. Examples of carbon black include channel black, furnace black, acetylene black, thermal black, and lamp black. Examples of magnetic materials include ferromagnetic metals such as iron, nickel, and cobalt, alloys containing these ferromagnetic metals, ferromagnetic metal compounds such as ferrite and magnetite, and alloys that do not contain ferromagnetic metals but exhibit ferromagnetism upon heat treatment. Examples of alloys that exhibit ferromagnetism upon heat treatment include Heusler alloys such as manganese-copper-aluminum and manganese-copper-tin, and chromium dioxide.

[0063] The content of the colorant is preferably 1 to 10 parts by mass, more preferably 2 to 9 parts by mass, relative to 100 parts by mass of the binder resin.

[0064] (mold release agent) As the release agent, various known waxes can be used. Examples of waxes include polyolefin waxes such as polyethylene wax and polypropylene wax, branched hydrocarbon waxes such as microcrystalline wax, long-chain hydrocarbon waxes such as paraffin wax and sazol wax, dialkyl ketone waxes such as distearyl ketone, carnauba wax, montan wax, ester waxes such as behenic acid behenate, trimethylolpropane tribehenate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecanediol distearate, trimellitate tristearyl, and distearyl maleate, and amide waxes such as ethylenediamine behenylamide and trimellitate tristearylamide. These release agents may be used alone or in combination of two or more.

[0065] The content of the release agent is preferably 7 parts by mass or less, more preferably 3 to 6 parts by mass, relative to 100 parts by mass of the binder resin.

[0066] (charge control agent) The charge control agent may be any of various known compounds. The content of the charge control agent is preferably within the range of 0.1 to 5.0% by mass relative to the total mass of the binder resin.

[0067] <External additives> As the external additive disposed on the surface of the toner base particles, conventionally known metal oxide particles can be used for the purpose of controlling fluidity and chargeability. In the present invention, the median diameter of the external additive based on the number of particles is in the range of 60 to 400 nm, and preferably in the range of 80 to 200 nm. The method for measuring the median diameter is as described above.

[0068] Examples of the external additive include silica particles, titania (titanium oxide) particles, alumina particles, zirconia particles, zinc oxide particles, chromium oxide particles, cerium oxide particles, antimony oxide particles, tungsten oxide particles, tin oxide particles, tellurium oxide particles, manganese oxide particles, and boron oxide particles. Among these external additives, silica particles or titania particles are preferred. These external additives may be used alone or in combination of two or more. Furthermore, organic fine particles of homopolymers such as styrene and methyl methacrylate, or copolymers thereof may be used as an external additive.

[0069] (silica particles) The silica particles preferably used as the external additive are particles mainly composed of silica (SiO2). The silica particles may be either crystalline or amorphous. The silica particles may be particles produced using silicon compounds such as water glass or alkoxysilane as raw materials, or may be particles obtained by pulverizing quartz. The silica particles may be, for example, sol-gel silica particles, aqueous colloidal silica particles, alcoholic silica particles, fumed silica particles obtained by a gas phase method or the like, fused silica particles, etc. Among the above, the silica particles are preferably sol-gel silica particles.

[0070] Sol-gel silica particles can be obtained, for example, as follows: Tetraalkoxysilane (e.g., TMOS) is dropped into an alkaline catalyst solution containing an alcohol compound and aqueous ammonia, and the tetraalkoxysilane is hydrolyzed and condensed to obtain a suspension containing sol-gel silica particles. The solvent is then removed from the suspension to obtain granules. The granules are then dried to obtain sol-gel silica particles.

[0071] The silica particles may be silica particles that have been hydrophobized with a hydrophobizing agent, such as a known organosilicon compound having an alkyl group (e.g., a methyl group, an ethyl group, a propyl group, a butyl group, etc.). Specific examples of hydrophobic treatment agents include alkoxysilane compounds, siloxane compounds, silazane compounds, etc. Among the above, the hydrophobic treatment agent is preferably at least one of a siloxane compound and a silazane compound. Examples of siloxane compounds include silicone oil and silicone resin. The silicone oil is preferably dimethylsilicone oil. Examples of silazane compounds include hexamethyldisilazane and tetramethyldisilazane. The silazane compound is preferably hexamethyldisilazane (HMDS). The hydrophobic treatment agents can be used alone or in combination of two or more.

[0072] The amount of the hydrophobic treatment agent such as a silazane compound attached to the surface of the silica particles is preferably in the range of 0.01 to 5 mass %, more preferably in the range of 0.05 to 3 mass %, and even more preferably in the range of 0.10 to 2 mass %, relative to the silica particles, from the viewpoint of improving the hydrophobicity of the silica particles.

[0073] Examples of methods for hydrophobizing silica particles with a hydrophobizing agent include the following methods. (1) A method in which a hydrophobic treatment agent is dissolved in supercritical carbon dioxide and applied to the surface of silica particles. (2) A method in which a solution containing a hydrophobic treatment agent is applied (for example, sprayed or coated) to the surface of silica particles in the atmosphere. (3) A method in which a solution containing a hydrophobic treatment agent is added to a silica particle dispersion in the atmosphere, the mixture is maintained, and then the mixture is dried.

[0074] The external additive may also contain a lubricant to further improve cleaning properties and transfer properties. Examples of the lubricant include metal salts of higher fatty acids such as salts of stearic acid with zinc, aluminum, copper, magnesium, calcium, etc., salts of oleic acid with zinc, manganese, iron, copper, magnesium, etc., salts of palmitic acid with zinc, copper, magnesium, calcium, etc., salts of linoleic acid with zinc, calcium, etc., and salts of ricinoleic acid with zinc, calcium, etc.

[0075] The content of the external additives is 0.3% by mass or less, preferably in the range of 0.1 to 0.2% by mass, based on the toner base particles. The shape of these external additives is not limited, and examples thereof include spherical, flat, plate-like, and needle-like shapes. Furthermore, there is no limit to whether the surfaces of the inorganic fine particles serving as external additives are surface-treated.

[0076] [Toner manufacturing method] The method for producing the toner according to the present invention is not particularly limited, and any known method can be used. Examples of known methods include a kneading and pulverization method, a suspension polymerization method, an emulsion aggregation method, a solution suspension method, a polyester elongation method, and a dispersion polymerization method. Among these, it is preferable to use the emulsion aggregation method from the viewpoint of controlling the internal particle size and shape.

[0077] The emulsion aggregation method is a method for producing toner particles by mixing a dispersion of binder resin particles (hereinafter also referred to as "binder resin particles") dispersed with a surfactant or a dispersion stabilizer with a dispersion of colorant particles (hereinafter also referred to as "colorant particles") as needed, aggregating them to a desired toner particle size, and further controlling the shape by fusing the binder resin particles together. Here, the binder resin particles may optionally contain a release agent, a charge control agent, etc.

[0078] An example of a method for producing a toner will be described below, but the present invention is not limited thereto. In the following example, a method for producing a toner containing a styrene-acrylic resin and a polyester will be described. (1) A step of synthesizing an amorphous polyester and preparing a dispersion of amorphous polyester particles (2) A process for synthesizing styrene-acrylic resin and preparing a dispersion of styrene-acrylic resin particles. (3) A step of preparing a dispersion of colorant particles (4) A process of aggregating amorphous polyester particles, styrene-acrylic resin particles, release agent, and colorant particles to form toner base particles. (5) A process of ripening the toner base particles and controlling their shape using thermal energy. (6) Step of cooling the dispersion of toner base particles (7) A process of filtering the toner base particles from the aqueous medium, washing the toner base particles to remove surfactants, etc., and obtaining wet toner base particles. (8) Step of removing solvent from wet toner base particles (9) A process of drying the wet toner base particles using airflow in the dryer. (10) A step of adding external additives to the dried toner base particles

[0079] (1) A step of synthesizing an amorphous polyester and preparing a dispersion of amorphous polyester particles In this step, an amorphous polyester is synthesized by a conventionally known method, and the amorphous polyester is dispersed in the form of fine particles in an aqueous medium to prepare a dispersion of amorphous polyester particles.

[0080] Specifically, an amorphous polyester is first dissolved or dispersed in an organic solvent to prepare an oil phase liquid. The oil phase liquid is then dispersed in an aqueous medium by phase inversion emulsification or the like to form oil droplets with a desired particle size. The organic solvent is then removed to prepare an aqueous dispersion of amorphous polyester particles.

[0081] The amount of the aqueous medium used is preferably within a range of 50 to 2000% by mass, more preferably within a range of 100 to 1000% by mass, based on the total mass of the oil phase liquid. From the viewpoint of dispersion stability of the oil droplets, a surfactant or the like may be added to the aqueous medium. Examples of the surfactant include various conventionally known anionic surfactants, cationic surfactants, nonionic surfactants, etc.

[0082] From the viewpoint of removal treatment after the formation of oil droplets, the organic solvent used for preparing the oil phase liquid is preferably one having a low boiling point and low solubility in water, such as methyl acetate, ethyl acetate, methyl ethyl ketone, methyl isobutyl ketone, toluene, and xylene. These may be used alone or in combination of two or more.

[0083] The amount of the organic solvent used is preferably within a range of 1 to 300% by mass based on the total mass of the amorphous polyester. The oil phase liquid can be emulsified and dispersed by utilizing mechanical energy.

[0084] The average particle size of amorphous polyester particles is the volume-based median diameter (D 50 ) and is preferably in the range of 100 to 400 nm. 50 ) can be measured using, for example, a "Microtrac UPA-150" (manufactured by Nikkiso Co., Ltd.).

[0085] (2) A process for synthesizing styrene-acrylic resin and preparing a dispersion of styrene-acrylic resin particles. In this process, a styrene-acrylic resin is synthesized by a conventionally known method, and the styrene-acrylic resin is dispersed in the form of fine particles in an aqueous medium to prepare a dispersion of styrene-acrylic resin particles.

[0086] The toner base particles may contain internal additives such as a release agent, a charge control agent, etc. Such internal additives may be incorporated into the toner base particles by, for example, dissolving or dispersing them in advance in a monomer solution used to synthesize the amorphous polyester or styrene-acrylic resin. In addition, when the release agent is not dissolved or dispersed in advance in the monomer solution for synthesizing the amorphous polyester or styrene-acrylic resin, a dispersion of release agent particles may be separately prepared, and this dispersion of release agent particles may be added together with other resin particle dispersions to aggregate the particles as described below.

[0087] When preparing a dispersion of release agent particles, the aqueous dispersion of release agent particles can be prepared by dispersing the release agent in an aqueous medium to which a surfactant has been added at a critical micelle concentration (CMC) or higher. The release agent can be dispersed by utilizing mechanical energy. The dispersing machine is not particularly limited, and examples thereof include ultrasonic dispersing machines, mechanical homogenizers, pressure dispersing machines such as Manton-Gaulin and pressure homogenizers, and media-type dispersing machines such as sand grinders and diamond fine mills.

[0088] The release agent particles have a volume-based median diameter (D 50 The volume-based median diameter (D) of the release agent particles is preferably in the range of 10 to 300 nm, more preferably in the range of 100 to 200 nm, and particularly preferably in the range of 100 to 150 nm. 50 ) can be measured, for example, using an electrophoretic light scattering photometer "ELS-800" (manufactured by Otsuka Electronics Co., Ltd.).

[0089] (3) A step of preparing a dispersion of colorant particles The aqueous dispersion of colorant particles can be prepared in the same manner as the aqueous dispersion of release agent particles. The release agent particles are preferably dispersed by heating to a temperature equal to or higher than their melting point, but the colorant particles do not necessarily need to be heated.

[0090] (4) A process of aggregating amorphous polyester particles, styrene-acrylic resin particles, release agent, and colorant particles to form toner base particles. In this process, a release agent and a flocculating agent at a concentration equal to or greater than the critical flocculation concentration are added to the aqueous dispersion in which the above-mentioned fine particles are dispersed, causing them to flocculate to some extent, and then the shape is controlled by fusing the fine particles together to form toner base particles.

[0091] The flocculant is not particularly limited, and is preferably, for example, a metal salt such as an alkali metal salt or an alkaline earth metal salt. Examples of the metal salt include monovalent metal salts such as sodium, potassium, and lithium; divalent metal salts such as calcium, magnesium, manganese, and copper; and trivalent metal salts such as iron and aluminum.

[0092] Specific examples of metal salts include sodium chloride, potassium chloride, lithium chloride, calcium chloride, magnesium chloride, zinc chloride, copper sulfate, magnesium sulfate, manganese sulfate, aluminum chloride, aluminum sulfate, polyaluminum chloride, polyaluminum hydroxide, etc. Among these, trivalent metal salts are preferred from the viewpoint of promoting aggregation with smaller amounts. These may be used alone or in combination of two or more.

[0093] (5) A process of ripening the toner base particles and controlling their shape using thermal energy. This step is carried out as necessary when the toner base particles are aged by thermal energy to control their shape. Specifically, in the aging treatment, the dispersion of the toner base particles is heated and stirred by adjusting the heating temperature, stirring speed, heating time, etc. so that the circularity of the toner base particles reaches a desired value.

[0094] (6) Step of cooling the dispersion of toner base particles In this step, the dispersion of toner base particles is cooled. The cooling rate is preferably within the range of 1 to 20°C / min. The specific cooling method is not particularly limited. Examples include a method of cooling by introducing a refrigerant from the outside of the reaction vessel, a method of cooling by directly adding cold water to the reaction system, and a method of cooling using a heat exchanger.

[0095] (7) A process of filtering the toner base particles from the aqueous medium, washing the toner base particles to remove surfactants, etc., and obtaining wet toner base particles. In this process, the toner base particles are separated from the cooled dispersion liquid of the toner base particles by solid-liquid separation. The resulting toner cake is then washed to remove any adhering substances such as surfactants and aggregating agents, thereby obtaining wet toner base particles. Note that the term "toner cake" used here refers to a cake-like aggregate of toner base particles in a wet state.

[0096] The method for solid-liquid separation is not particularly limited, and examples thereof include centrifugation, vacuum filtration using a Nutsche filter, etc., and filtration using a filter press, etc. In addition, in washing, it is preferable to wash with water until the electrical conductivity of the filtrate becomes 10 μS / cm or less.

[0097] (8) Step of removing solvent from wet toner base particles This step is carried out as necessary when the amount of solvent contained in the wet toner base particles is to be reduced. By performing the solvent removal treatment, the amount of solvent contained in the obtained wet toner base particles can be reduced. In addition, by adjusting the time, rotation conditions, pressure conditions, etc., during the solvent removal treatment, the amount of solvent contained in the obtained wet toner base particles can be adjusted.

[0098] (9) Step of drying the wet toner base particles In this step, the wet toner base particles that have been washed and, in some cases, further treated to remove the solvent are dried in a dryer. Examples of the dryer include a spray dryer, a vacuum freeze dryer, a reduced pressure dryer, etc. In particular, it is preferable to use a stationary shelf dryer, a mobile shelf dryer, a fluidized bed dryer, a rotary dryer, an agitator dryer, etc. The moisture content of the dried toner base particles is preferably 5% by mass or less, and more preferably 2% by mass or less. In addition, when the dried toner base particles are aggregated by weak inter-particle attractive forces, the aggregates may be subjected to a crushing treatment. As the crushing treatment device, a mechanical crushing device such as a jet mill, a Henschel mixer, a coffee mill, or a food processor can be used.

[0099] The drying temperature is preferably within a range of 10 to 45° C., and particularly preferably within a range of 20 to 40° C. If the drying temperature is higher than 45° C., the crystalline components in the toner will be in a molten state, which is thought to make it difficult to control the structure.

[0100] (10) A step of adding external additives to the dried toner base particles The toner base particles can be used as a toner as they are, but from the viewpoint of fluidity, chargeability, cleaning properties, etc., external additives such as so-called fluidizing agents and cleaning aids are added to the toner base particles. Examples of the mixing device for the external additive include mechanical mixers such as a Henschel mixer and a coffee mill.

[0101] The above steps (1) to (10) are an example of a method for producing toner base particles, and the present invention is not limited thereto. The toner base particles according to the present invention may have a core-shell structure. The toner base particles have a shell layer, which allows both low-temperature fixability and heat resistance to be achieved. When a shell layer is formed, it is preferable to form the shell layer after forming the core particles in step (4). The shell layer is preferably made of an amorphous resin. The method for forming the shell layer is not particularly limited, and any conventionally known method can be used.

[0102] [Toner properties] <Volume average particle size of toner particles> The volume average particle diameter of the toner particles is preferably 3.0 to 6.5 μm. From the viewpoint of ease of production, the volume average particle diameter of the toner particles is preferably 3.0 μm or more. Furthermore, from the viewpoint of preventing the charge amount from being too low and thus preventing image defects due to low charge amount components from occurring, the volume average particle diameter of the toner particles is preferably 6.5 μm or less.

[0103] The "volume average particle size" of the toner particles in the present invention is the volume-based median diameter (D 50 The volume-based median diameter can be measured and calculated using, for example, a device such as a Multisizer 3 (manufactured by Beckman Coulter) connected to a computer system for data processing. The measurement procedure involves dispersing 0.02 g of toner particles in 20 ml of surfactant solution. This surfactant solution is typically prepared by diluting a neutral detergent containing surfactant components 10 times with pure water, with the aim of dispersing the toner particles. Then, ultrasonic dispersion is performed for one minute to produce a toner particle dispersion. This toner particle dispersion is then pipetted into a beaker containing an ISOTON II (manufactured by Beckman Coulter) in the sample stand until the measurement concentration reaches 5-10%, and the measurement is performed with the instrument count set to 25,000 particles. The aperture diameter of the Multisizer 3 is 100 μm. The measurement range of 1 to 30 μm is divided into 256 parts, and the frequency is calculated. The particle diameter of the particle with the largest volume fraction (50%) is defined as the volume-based median diameter (D 50 ) The volume average particle size of the toner particles can be controlled by, for example, controlling the concentration of the coagulant, the amount of organic solvent added, or the fusion time during production.

[0104] <Average circularity of toner particles> The average circularity of the toner particles is preferably 0.945 or more, since the closer to a sphere the better from the viewpoint of charge buildup and fluidity. The average circularity is calculated as follows. The toner particles are wetted in a surfactant aqueous solution and dispersed by ultrasonic dispersion for 1 minute. Then, using a flow particle image analyzer "FPIA-3000" (manufactured by Sysmex Corporation), measurements are taken in HPF (high magnification imaging) mode at an appropriate concentration of 3,000 to 10,000 HPF detection particles. Within this range, reproducible measurements can be obtained. Circularity is calculated using the following formula: Circularity = (perimeter of a circle with the same projected area as the particle image) / (perimeter of the projected particle image) The average circularity is the arithmetic mean value obtained by adding up the circularity of each particle and dividing the sum by the total number of particles measured.

[0105] [Developer] The toner can be used as a magnetic or non-magnetic one-component developer, or the toner can be mixed with a carrier to form a two-component developer. When the toner is used as a two-component electrostatic image developer, the carrier may be magnetic particles made of a conventionally known material such as a metal such as iron, ferrite, or magnetite, or an alloy of such a metal with a metal such as aluminum or lead. Ferrite particles are particularly preferred as the carrier.

[0106] As the carrier, a coated carrier in which the surface of magnetic particles is coated with a coating agent such as a resin, or a dispersion type carrier in which magnetic powder is dispersed in a binder resin may be used. The volume-based median diameter of the carrier (D 50 ) is preferably in the range of 20 to 100 μm, more preferably in the range of 25 to 80 μm. The volume-based median diameter of the carrier (D 50 ) can be measured, for example, by a laser diffraction particle size distribution measuring device HELOS (manufactured by SYMPATEC) equipped with a wet disperser.

[0107] [Image forming method and image forming apparatus] As described above, the image forming method of the present invention is characterized in that the median diameter based on the number of external additives is within a range of 60 to 400 nm, the external additives are contained in an amount of 0.3 mass % or less relative to the toner base particles, and the air permeability of the long medium is 20,000 sec or more. An example of an electrophotographic image forming method and image forming apparatus will be described below, but the present invention is not limited to this.

[0108] The electrophotographic image forming method preferably includes a step of adhering the toner to a recording medium and a step of fixing the adhered toner to the recording medium. The image forming method also preferably includes a step of applying varnish to the surface of the toner image formed by fixing the toner to form a varnish coat, in terms of improving image quality and durability. In the present invention, an image forming apparatus for long media that forms an image on long media can be used.

[0109] FIG. 1 is a diagram showing an example of the overall configuration of an image forming apparatus according to this embodiment. The image forming apparatus 100 shown in FIG. 1 is an apparatus that forms images on long media such as roll paper or continuous forms. Image forming apparatus 100 is configured such that, from the upstream side along the transport direction (paper transport direction) of long media M, a paper feeder (paper feed section) 1, a main body section 2, and a winding device (winding section) 3 are connected. Note that while Fig. 1 shows a case where paper feeder 1 and winding device 3 are configured separately from main body section 2, they may also be configured integrally.

[0110] The paper feeder 1 is a device that feeds long media M to the main body 2. Driven by a motor (not shown), the paper feeder 1 transports the long media M wound around a support shaft X at a constant speed to the main body 2. The operation of the motor of the paper feeder 1 is controlled by a control unit 10 (see FIG. 2) provided in the main body 2. The paper feeder 1 is also provided with a tension applying mechanism 101 that applies tension to the long media M. The tension applying mechanism 101 is configured to include driven rollers 101a and 101b, a dancer roller 101c, a weight 101d, etc. The fed long media M is wound around the driven roller 101a, the dancer roller 101c, and the driven roller 101b and passed through the main body 2.

[0111] The main body 2 forms an image on the long medium M fed from the paper feeder 1 by an intermediate transfer method using electrophotography. Fig. 2 is a diagram showing the main parts of the control system of the image forming apparatus 100. As shown in Fig. 2, the main body 2 includes a control unit 10, a storage unit 20, an operation display unit 30, an image forming unit 40, a paper conveying unit 50, a fixing unit 60, a communication unit 70, etc.

[0112] The control unit 10 includes a CPU (Central Processing Unit) 10a, a ROM (Read Only Memory) 10b, a RAM (Random Access Memory) 10c, etc. The CPU 10a reads a program corresponding to the processing content from the ROM 10b, loads it into the RAM 10c, and works with the loaded program to centrally control the operations of each part of the main body 2, the paper feeder 1, the winder 3, etc.

[0113] The storage unit 20 is configured by, for example, a non-volatile semiconductor memory (so-called flash memory), a hard disk drive, etc. Input document data, various setting information, image data, etc. are stored in the storage unit 20. Note that these data, etc. may also be stored in the RAM 10c of the control unit 10.

[0114] The operation display unit 30 is configured, for example, by a liquid crystal display (LCD) with a touch panel, and functions as a display unit 31 and an operation unit 32. The display unit 31 displays various operation screens, image states, operation statuses of various functions, etc. in accordance with a display control signal input from the control unit 10. The operation unit 32 includes various operation keys such as a numeric keypad and a start key, and receives various input operations from the user and outputs operation signals to the control unit 10.

[0115] The image forming unit 40 forms (prints) an image by forming toner images of each color, Y (yellow), M (magenta), C (cyan), and K (black), on the photosensitive drums 41Y, 41M, 41C, and 41K based on image data input from an external device (such as a personal computer) via the communication unit 70, and then sequentially transferring the images to the intermediate transfer belt 42 to superimpose the four color toner images, and then performing a second transfer onto the long media M fed from the paper feeder 1 using the transfer roller 43.

[0116] The paper transport section 50 includes a paper path 52 equipped with a plurality of transport rollers. The paper transport unit 50 transports the long medium M transported from the paper feeder 1 to the main body 2 under the control of the control unit 10 to the image forming unit 40, and transports the long medium M on which a toner image has been formed in the image forming unit 40 to the fixing unit 60. Then, the paper transport unit 50 transports the long medium M on which the toner image has been fixed in the fixing unit 60 to the winding device 3.

[0117] At least one pair of nip rollers 53 is provided on the paper path 52 upstream of the fixing unit 60 and downstream of the paper feeder 1. At least one pair of nip rollers 54 is provided downstream of the fixing unit 60 and upstream of the winding device 3. The nip rollers 53, 54 can be pressed together and separated by a pressure drive mechanism. By pressing both nip rollers 53, 54 together while tension is being applied to the long media M by the tension application mechanism 101 and the tension application mechanism 301, it is possible to maintain the tension applied to the long media M between the nip rollers 53, 54 even when the roller rotation is stopped and the tension application by the tension application mechanisms 101, 301 is released.

[0118] The fixing unit 60 fixes the toner image to the long medium M by applying heat and pressure to the long medium M on which the toner image has been formed in a fixing nip. The fixing unit 60 includes a heating roller 61, a heat source 62 for heating the heating roller 61, an upper pressure roller 63, an endless fixing belt 64 stretched between the heating roller 61 and the upper pressure roller 63, and a lower pressure roller 65. The heating roller 61 to the fixing belt 64 are provided on the fixing surface side of the long medium M, and the lower pressure roller 65 is provided opposite the fixing belt 64 across the paper path 52 of the long medium M (i.e., on the back side of the long medium M). A heat source for heating the lower pressure roller 65 may be provided.

[0119] The lower pressure roller 65 is configured to be movable, and the upper pressure roller 63 and the lower pressure roller 65 can be pressed against and separated from each other by driving a pressure drive mechanism (not shown). The upper pressure roller 63 and the lower pressure roller 65 are pressed against and separated from each other, thereby enabling the fixing belt 64 and the lower pressure roller 65 to be pressed against and separated from each other. The fixing belt 64 and the lower pressure roller 65 are pressed against each other to form a fixing nip that sandwiches and transports the long media M. The long media M is heated and pressurized as it passes through the fixing nip formed by the fixing belt 64, which is heated by the heat source 62, and the lower pressure roller 65, and the toner image is fixed thereto.

[0120] The communication unit 70 is configured by a communication control card such as a LAN (Local Area Network) card, and transmits and receives various data to and from an external device (such as a personal computer) connected to a communication network such as a LAN or WAN (Wide Area Network).

[0121] The winding device 3 is a device that winds up the long medium M transported from the main body 2. Driven by a motor (not shown), the winding device 3 winds up the long medium M transported from the main body 2 around the support shaft Y at a constant speed. The winding operation of the winding device 3 is controlled by a control unit 10 provided in the main body 2. The winding device 3 is also provided with a tension applying mechanism 301 that applies tension to the long medium M. The tension applying mechanism 301 is configured with driven rollers 301a and 301b, a dancer roller 301c, a weight 301d, etc. The long medium M transported from the main body 2 is wound around the driven rollers 301a, 301c, and 301b, tension is applied to the long medium M, and the long medium M is transported to the support shaft Y.

[0122] In this embodiment, the tension applying mechanism is provided in the paper feeder 1 and the winder 3, but it may be provided in only one of them. The above-described apparatus configuration and image forming method are exemplary embodiments for carrying out the present invention, and the present invention is not limited to these. [Example]

[0123] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In the following examples, unless otherwise specified, operations were carried out at room temperature (25°C). Furthermore, unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass," respectively.

[0124] <Preparation of styrene-acrylic resin particle dispersion A> (1) First-stage polymerization A reaction vessel equipped with a stirrer, temperature sensor, cooling tube, and nitrogen introduction device was prepared. Eight parts by mass of sodium dodecyl sulfate and 3,000 parts by mass of ion-exchanged water were dissolved in the reaction vessel to prepare a surfactant solution. The surfactant solution was stirred at a stirring speed of 230 rpm under a nitrogen stream while the internal temperature was raised to 80°C. After the temperature was raised, a solution of 10 parts by mass of potassium persulfate (KPS) dissolved in 200 parts by mass of ion-exchanged water was added to the surfactant solution. After the liquid temperature was raised to 80°C again, a polymerizable monomer mixture containing the following compounds was added dropwise over 1 hour. Styrene 480 parts by mass n-Butyl acrylate 250 parts by mass Methacrylic acid 68 parts by mass n-Octyl-3-mercaptopropionate 16 parts by mass After the dropwise addition, the system was heated and stirred at 80° C. for 2 hours to carry out polymerization (first stage polymerization), thereby producing "resin particle dispersion 1h" containing "resin particles 1h".

[0125] (2) Second-stage polymerization In a flask equipped with a stirrer, a surfactant solution prepared by dissolving 7 parts by mass of sodium polyoxyethylene-2-dodecyl ether sulfate in 800 parts by mass of ion-exchanged water was heated to 98° C. To this surfactant solution, 260 parts by mass (solids equivalent) of the "Resin Particle Dispersion 1h" and a polymerizable monomer mixture containing the following compounds were added. Styrene 245 parts by mass n-Butyl acrylate 120 parts by mass n-Octyl-3-mercaptopropionate 1.5 parts by mass Paraffin wax "HNP-11 (manufactured by Nippon Seiro Co., Ltd.)" 67 parts by mass After adding the polymerizable monomer mixture, a mixing and dispersion process was carried out for 1 hour using a mechanical disperser "Clearmix" (manufactured by M Technique Co., Ltd.) with a circulation path to prepare a dispersion containing emulsified particles. Next, a solution prepared by dissolving 6 parts by mass of potassium persulfate in 200 parts by mass of ion-exchanged water was added to the dispersion. Then, the system consisting of the dispersion and the added solution was heated and stirred at 82°C for 1 hour to carry out polymerization (second-stage polymerization), thereby producing "Resin Particle Dispersion 1HM" containing "Resin Particles 1HM".

[0126] (3) Third-stage polymerization To the above "Resin Particle Dispersion 1HM," an initiator solution prepared by dissolving 11 parts by mass of potassium persulfate in 400 parts by mass of ion-exchanged water was added, and the liquid temperature was raised to 80° C. Thereafter, a polymerizable monomer mixture containing the following compound was added dropwise over 1 hour. Styrene 435 parts by mass n-Butyl acrylate 130 parts by mass Methacrylic acid 33 parts by mass n-Octyl-3-mercaptopropionate 8 parts by mass After the dropwise addition was completed, polymerization (third-stage polymerization) was carried out by heating and stirring for 2 hours, and then the mixture was cooled to 28°C to prepare "resin particle dispersion A" containing "resin particles a". The particle diameter of "resin particles a" contained in the above "resin particle dispersion A" was measured using an electrophoretic light scattering photometer "ELS-800 (Otsuka Electronics Co., Ltd.)" and found to be 150 nm in volume-based median diameter. Furthermore, the glass transition temperature was measured using a known method and found to be 45°C. The weight-average molecular weight of the styrene-acrylic resin that constitutes resin particles a was 32,000.

[0127] <Preparation of Colorant Particle Dispersion P> While stirring a solution prepared by dissolving 90 parts by mass of sodium dodecyl sulfate in 1600 parts by mass of ion-exchanged water, 420 parts by mass of CI Pigment Blue 15:3 (manufactured by Toyo Ink Co., Ltd.) was gradually added. Next, a dispersion process was carried out using a stirring device "Clearmix (manufactured by M Technique Co., Ltd.)" to prepare a colorant particle dispersion liquid P.

[0128] <Preparation of Amorphous Polyester Particle Dispersion B> (Preparation of amorphous polyester) The following compounds were placed in a four-neck flask equipped with a nitrogen inlet tube, a dehydration tube, a stirrer and a thermocouple, and a polycondensation reaction was carried out at 230° C. for 8 hours. Bisphenol A propylene oxide 2 mole adduct 285.7 parts by mass Terephthalic acid 66.9 parts by mass Fumaric acid 47.4 parts by mass Esterification catalyst (tin octoate) 1.43 parts by mass After the 8-hour polycondensation reaction, the reaction was continued at 8 kPa for 1 hour, and the mixture was cooled to 160° C., and then a mixture consisting of the following compounds was added dropwise using a dropping funnel over 1 hour. Acrylic acid 3.3 parts by mass Styrene 26.4 parts by mass Butyl acrylate 6.6 parts by mass Polymerization initiator (di-t-butyl peroxide) 5.3 parts by mass After the dropwise addition, the addition polymerization reaction was continued for 1 hour while maintaining the temperature at 160°C, then the temperature was raised to 200°C and maintained at 10 kPa for 1 hour, after which styrene and butyl acrylate were removed to obtain an amorphous polyester.

[0129] (Preparation of amorphous polyester particle dispersion) Methyl ethyl ketone and isopropyl alcohol were added to a reactor equipped with an anchor blade for stirring. The amorphous polyester coarsely ground in a hammer mill was gradually added and stirred until completely dissolved, yielding a polyester resin solution that would become the oil phase. A small amount of dilute aqueous ammonia was added dropwise to the stirred oil phase. Next, this oil phase was added dropwise to ion-exchanged water to cause phase inversion emulsification, and the solvent was then removed under reduced pressure using an evaporator. Amorphous polyester particles were dispersed in the reaction system, and ion-exchanged water was added to the dispersion to adjust the solid content to 20% by mass, thereby preparing Amorphous Polyester Particle Dispersion B. The volume-based median diameter of the amorphous polyester particles in the dispersion was measured using a particle size distribution analyzer "Nanotrack Wave" (manufactured by Microtrack Bell Co., Ltd.) and was found to be 173 nm.

[0130] <Preparation of Toner Base Particles 1> A reaction vessel equipped with a stirrer, a temperature sensor, a cooling tube, and a nitrogen introducing device was prepared, and the following compounds were charged into the reaction vessel. Styrene-acrylic resin particle dispersion A 150 parts by mass (solid content) Amorphous polyester particle dispersion B 150 parts by mass (solid content equivalent) Ion-exchanged water 1400 parts by mass Colorant particle dispersion P 120 parts by mass (solid content equivalent) Furthermore, a solution of 3 parts by mass of sodium polyoxyethylene-2-dodecyl sulfate dissolved in 120 parts by mass of ion-exchanged water was added, and the liquid temperature was raised to 30° C. Thereafter, a 5 mol / L aqueous solution of sodium hydroxide was added to adjust the pH to 10.

[0131] Next, an aqueous solution of 35 parts by mass of magnesium chloride hexahydrate dissolved in 35 parts by mass of ion-exchanged water was added over 10 minutes at 30°C while stirring, and the temperature was then raised for 3 minutes. The temperature was then raised to 90°C over 60 minutes, and the particles were allowed to aggregate and fuse while maintained at 90°C. The particle size of the particles growing in the reaction vessel was measured using a Multisizer 3 (Beckman Coulter, Inc.). When the volume-based median diameter reached 6.5 μm, an aqueous solution of 150 parts by mass of sodium chloride dissolved in 600 parts by mass of ion-exchanged water was added to stop particle growth. Further, as a maturation treatment, the liquid temperature was raised to 98°C and the mixture was heated and stirred, and the fusion of particles was allowed to proceed until the average circularity measured with "FPIA-2100 (manufactured by Sysmex Corporation)" reached 0.965. Thereafter, the liquid temperature was cooled to 30° C., the pH of the liquid was adjusted to 2 using hydrochloric acid, and stirring was stopped. In this way, a toner base particle dispersion liquid was prepared. The toner base particle dispersion liquid prepared through the above steps was subjected to solid-liquid separation using a basket-type centrifuge "MARKIII Model No. 60x40 (manufactured by Matsumoto Kikai Co., Ltd.)" to form a wet cake of toner base particles 1. This wet cake was washed with ion-exchanged water at 45°C using the basket centrifuge until the electrical conductivity of the filtrate reached 5 μS / cm. Thereafter, the cake was transferred to a "Flash Jet Dryer (manufactured by Seishin Enterprise Co., Ltd.)" and dried until the moisture content reached 0.5% by mass, thereby producing cyan toner base particles 1.

[0132] <Preparation of Toner Base Particles 2> Toner base particles 2 were prepared in the same manner as in the preparation of toner base particles 1, except that the amount of amorphous polyester particle dispersion B was changed to 300 parts by mass (solid content equivalent) and styrene-acrylic resin particle dispersion A was not used.

[0133] <Preparation of Toner Base Particles 3> Toner base particles 3 were prepared in the same manner as in the preparation of toner base particles 1, except that the amount of styrene-acrylic resin particle dispersion A was changed to 300 parts by mass (solid content equivalent) and amorphous polyester particle dispersion B was not used.

[0134] <Preparation of Silica Particles 1> 347.4 g of pure water was weighed into an Erlenmeyer flask, and 110 g of tetramethoxysilane (TMOS) was added to the Erlenmeyer flask with stirring. The mixture was stirred for 1 hour to prepare 457.4 g of a TMOS hydrolyzed solution. Next, 2250 g of water and 112 g of ethylenediamine were mixed in a 3-liter reactor equipped with a stirrer, a dropping funnel, and a thermometer. The temperature of this solution was adjusted to 35°C, and the TMOS hydrolyzed solution was added to the solution at a rate of 5.0 mL / min with stirring. After the addition of the TMOS hydrolyzed liquid was completed, the mixture was maintained in this state for 30 minutes, and then 4.5 g of a 1 mmol / g aqueous solution of ethylenediamine was added to adjust the pH to 8-9. Thereafter, the remaining TMOS hydrolyzed solution was added at a rate of 5.0 mL / min every 3 hours while adding an alkaline catalyst (1 mmol / g aqueous ethylenediamine solution) as needed to maintain the pH at 8. This was continued until a total of 457.4 g was added. After the dropwise addition of the TMOS hydrolyzed solution was completed, stirring was continued for another 0.5 hours to allow hydrolysis and condensation to proceed, yielding a mixed medium dispersion of hydrophilic spherical silica particles. The resulting silica particles had a number-based median diameter of 80 nm.

[0135] (Hydrophobic treatment) A solution was prepared by mixing 50 parts by mass of ethanol with 20 parts by mass of hexamethyldisilazane (HMDS). The solution was sprayed onto the silica particles obtained above with a median diameter of 80 nm using a spray dryer, and the silica particles were subjected to a hydrophobic treatment. After the ethanol was dried and removed at 80°C, the silica particles were treated with hexamethyldisilazane (HMDS) while stirring at 250°C for 2 hours, yielding silica particles 1. The median diameter of silica particles 1 after the hydrophobic treatment was 80 nm. The median diameter of silica particles 1 before and after the hydrophobic treatment remained unchanged. The same applies to silica particles 2 to 6 below.

[0136] <Preparation of Silica Particles 2> Hydrophobized silica particles 2 were obtained in the same manner as in the preparation of silica particles 1, except that the addition rate of the TMOS hydrolyzed liquid was changed from 5.0 mL / min to 8.5 mL / min. The median diameter of the obtained silica particles 2 was 150 nm.

[0137] <Preparation of Silica Particles 3> Hydrophobized silica particles 3 were obtained in the same manner as in the preparation of silica particles 1, except that the addition rate of the TMOS hydrolyzed liquid was changed from 5.0 mL / min to 25 mL / min. The median diameter of the obtained silica particles 3 was 400 nm.

[0138] <Preparation of Silica Particles 4> Hydrophobized silica particles 4 were obtained in the same manner as in the preparation of silica particles 1, except that the addition rate of the TMOS hydrolyzed liquid was changed from 5.0 mL / min to 3.5 mL / min. The median diameter of the obtained silica particles 4 was 60 nm.

[0139] <Preparation of Silica Particles 5> Hydrophobized silica particles 5 were obtained in the same manner as in the preparation of silica particles 1, except that the addition rate of the TMOS hydrolyzed liquid was changed from 5.0 mL / min to 2.5 mL / min. The median diameter of the obtained silica particles 5 was 50 nm.

[0140] <Preparation of Silica Particles 6> Hydrophobized silica particles 6 were obtained in the same manner as in the preparation of silica particles 1, except that the addition rate of the TMOS hydrolyzed liquid was changed from 5.0 mL / min to 30 mL / min in the preparation of silica particles 1. The median diameter of the obtained silica particles 6 was 500 nm.

[0141] <Preparation of titania particles 1> As titania particles 1, TAF-520 (manufactured by Fuji Titanium Co., Ltd., number-based median diameter 100 nm) was used. The number-based median diameters of the silica particles and titania particles were measured using a scanning electron microscope (SEM) S-4800 (manufactured by Hitachi, Ltd.) as described above.

[0142] [Table 1]

[0143] <Preparation of Toner 1> (External addition treatment) The following toner base particles and silica particles were mixed in a Henschel mixer (FM-75, manufactured by Mitsui Miike Chemical Engineering Co., Ltd.) at a rotation speed of 30 s -1 The mixture was mixed for 10 minutes, and a toner 1 was obtained. Toner base particles 1 100 parts by mass Silica particles 1 0.15 parts by mass

[0144] <Preparation of Toners 2 to 14> Toners 2 to 14 were obtained in the same manner as in the preparation of Toner 1, except that the types and added parts of the toner base particles and external additives were changed as shown in Table II below. In Table II below, the added parts of the external additive refer to the added parts per 100 parts by mass of the toner base particles.

[0145] <Preparation of developer> 100 parts by mass of ferrite particles (volume-based median diameter: 50 μm (manufactured by Powder Tech Co., Ltd.)) and 4 parts by mass of methyl methacrylate-cyclohexyl methacrylate copolymer resin (volume-based median diameter of primary particles: 85 nm) were placed in a high-speed mixer with horizontal mixing blades and mixed for 15 minutes at a mixing blade peripheral speed of 8 m / s and a temperature of 30°C. The mixture was then heated to 120°C and stirred for 4 hours. The mixture was then cooled, and fragments of the methyl methacrylate-cyclohexyl methacrylate copolymer resin were removed using a 200-mesh sieve to produce a resin-coated carrier. This resin-coated carrier was mixed with each of the above toners 1 to 14 so that the toner concentration was 7% by mass relative to the total mass of the toner and carrier, to produce two-component developers 1 to 14, respectively.

[0146] [Table 2]

[0147] [evaluation] <Image forming device> The image forming apparatus used was a color label printer, Accurio Label 230 (manufactured by Konica Minolta, Inc.), modified to allow the surface temperature and toner adhesion amount of the upper and lower fixing rollers to be changed. The two-component developer described above was sequentially loaded into this image forming apparatus. In the image forming apparatus, the long media was transported through the apparatus in a rolled state, and after the toner image was formed, it was rerolled. In this way, an image was formed on the long media that was set up in a rolled state and then rerolled and stored after printing. The long media used were the types shown in Table III below.

[0148] [Table 3]

[0149] <Average coverage rate of external additives S> The average coverage S of the external additive was measured using a scanning electron microscope (SEM) S-4800 (manufactured by Hitachi, Ltd.) as described above.

[0150] <Young's modulus of image> The Young's modulus of the image formed on the long medium was measured using a Hysitron TI-980 (manufactured by Bruker Japan Co., Ltd.) as described above. The measurement was performed five times for each sample. Young's modulus Er (GPa) was calculated from the measurement results, and the average value of the five measurement data was taken as the Young's modulus of the sample.

[0151] <Image peeling> The temperature of the upper fixing belt was set to a temperature (UO avoidance temperature) 25°C higher than the temperature at which under-offset does not occur (UO avoidance temperature), and the temperature of the lower fixing roller was set to 90°C. Continuous output was then performed on Media 1 (media width 320 mm). The fixing speed was a linear speed of 230 mm / sec. After a total of 100m of images had been output, the roll was removed from the winder and the image was inspected visually and with a magnifying glass. Grades "A", "B" and "C" were considered acceptable based on the following criteria. (standard) A: No image peeling can be detected even when observed under a microscope at 100x magnification. B: Even when observed under a 20x magnification, no image peeling can be detected. C: When magnified with a 20x loupe, slight image peeling can be detected, but it is completely undetectable with the naked eye and does not affect image quality. D: Slight image peeling can be detected by visual observation. E: Image peeling can be clearly detected visually.

[0152] <Image distortion> In the evaluation method for image peeling, the image immediately after fixing and before being wound up was observed using a microscope to determine whether there were any holes with a diameter of about 0.1 to 0.5 mm in the image, and the evaluation was made. "A", "B", and "C" were considered acceptable based on the following criteria. (standard) A: There are no holes and no problems. B: 4cm 2 There are 1-2 holes per square meter, but they are barely noticeable unless you look closely, so there are no practical issues. C:4cm 2 There are 3 to 5 holes per square meter, but they are barely noticeable unless you look closely, so there are no practical issues. D:4cm 2 There were six or more clear holes per square meter, which was problematic for practical use. Visual inspection and observation with a magnifying glass were carried out.

[0153] <Fixation> The image forming apparatus used was the one modified as described above, and the two-component developers were sequentially loaded into the image forming apparatus. In the image forming apparatus, the recording medium is transported through the image forming apparatus in a rolled state, and after the toner image is formed, it is rolled up again. In this way, an image is formed on the recording medium that is set up in a rolled state, and after printing, is rolled up again and stored. The long media shown in the table below were used as recording media. The toner adhesion amount on the long media was 8.0 g / m. 2 A test was conducted in which a solid image was output at a fixing temperature of 130 to 190°C, and the fixing temperature was changed in 5°C increments. The lowest fixing temperature at which image staining due to fixing offset was not visually confirmed was taken as the minimum fixing temperature, and the low-temperature fixability was evaluated according to the following evaluation criteria. "A", "B" and "C" in the following criteria were considered to be acceptable. (standard) A: Minimum fixing temperature is less than 130°C (extremely good low-temperature fixing properties of the toner) B: Minimum fixing temperature is 130°C or higher and lower than 150°C (good low-temperature fixing properties of the toner) C: Minimum fixing temperature is 150°C or higher and lower than 170°C (low temperature fixing ability of toner is somewhat good) D: Minimum fixing temperature is 170°C or higher (the toner has poor low-temperature fixing properties and cannot be used)

[0154] <Gloss change> In the method for evaluating the image peeling, a roll that has finished outputting a total of 1000 m with the temperature of the fixing upper belt being 25°C higher than the temperature at which the under offset occurred is taken out from the winder, and the glossiness is measured for each of the solid images at the 10 m output point and the solid image at the 1000 m output point, and the gloss change is evaluated as follows. The glossiness was measured using a Micro-Gloss (75°) manufactured by BYK Gardner, and three points were measured in the axial direction of the photoreceptor, and the glossiness (unit: %) of each image was calculated by averaging these values. The gloss change (gloss unevenness) was calculated as the glossiness difference (Gloss difference) between the solid images at 1000 m and 10 m, and evaluated according to the following criteria. "A", "B", and "C" of the following criteria were considered acceptable. (Criteria) A: Gloss difference ≤ 3 (The optical difference between 1000 m and 10 m is hardly noticeable) B: 3 < Gloss difference ≤ 8 (There is a slight optical difference between 1000 m and 10 m, but there is no problem in practical use) C: 8 < Gloss difference ≤ 15 (There is an optical difference between 1000 m and 10 m, but there is no problem in practical use) D: 15 < Gloss difference (The optical difference between 1000 m and 10 m is clear, and there is a problem in practical use)

[0155] [Table 4] <�

[0156] [Table 5]

[0157] As shown in the above results, it is recognized that the image forming method of the present invention can reduce image peeling, image roughness, and gloss unevenness, and has excellent low-temperature fixing properties as compared with the comparative examples.

Explanation of Signs

Claims

1. An image forming method using a toner for developing an electrostatic latent image, the toner including toner particles having an external additive on the surface of the toner base particles, and a long medium, comprising: the external additive has a number-based median diameter within a range of 60 to 400 nm, and the external additive is contained in an amount of 0.3% by mass or less relative to the toner base particles; The air permeability of the long media is 20,000 sec or more. An image forming method comprising:

2. The average coverage S of the external additive in the toner particles determined by image analysis using a scanning electron microscope is 3% by area or less.

2. The image forming method according to claim 1.

3. The thickness of the long media is within the range of 20 to 80 μm.

2. The image forming method according to claim 1.

4. The toner base particles contain a styrene-acrylic resin and a polyester.

2. The image forming method according to claim 1.

5. The Young's modulus of the image formed on the long medium is within a range of 1.5 to 3.0 MPa.

2. The image forming method according to claim 1.

6. The external additive contains silica particles or titania particles.

2. The image forming method according to claim 1.

Images