EP4647843A2

EP4647843A2 - Image forming method

Info

Publication number: EP4647843A2
Application number: EP25169212.5A
Authority: EP
Inventors: Ikuko Sakurada; Kazumi Oura; Tomoko Mine
Original assignee: Konica Minolta Inc
Current assignee: Konica Minolta Inc
Priority date: 2024-04-16
Filing date: 2025-04-08
Publication date: 2025-11-12
Also published as: JP2025162838A; EP4647843A3

Abstract

An image forming method that forms an image on at least a long sheet by using toner containing at least a binding resin, a wax and an external additive is shown. The method includes, preparing the binding resin as a mixture of at least a crystalline polyester resin and an amorphous polyester resin, and preparing a content rate of a saturated hydrocarbon compound having 16 to 35 carbon atoms in the toner to be 1 to 1000 ppm by mass.

Description

BACKGROUND OF THE INVENTION

TECHNICAL FIELD

The present invention relates to an image forming method. In particular, the present invention relates to an image forming method for forming an image on at least a long sheet using toner.

DESCRIPTION OF RELATED ART

In recent years, due to diversification of working ways, a downsized and highly functional printer has been generally required for working at home and for small offices. Examples of the higher functionality include higher speed, energy saving, and media compatibility, and demands regarding toner are also increasing. In particular, in order to support long paper in a small printer, the sheet needs to be conveyed in a limited space, and therefore machine design for smooth sheet feeding is mainly performed (e.g., see Japanese Unexamined Patent Publication No. 2022-115588 ). The long paper refers to, for example, a sheet having a special size that is longer than a sheet feed tray in a conveyance direction of the sheet, and examples thereof include roll sheet and continuous sheet. Hereinafter, the long paper is also referred to as a long sheet.
On the other hand, a toner for use on long paper is required to have excellent fixing performance from a leading end to a trailing end of a sheet. It is generally well known that a crystalline resin is used as a binding resin of a toner in order to realize excellent fixability. Furthermore, when an image is formed on a continuous sheet, the image may be rubbed by winding after fixing. For this reason, excellent image strength is required, and a technique of using two kinds of resins as the binding resins of the toner has been proposed (for example, see Japanese Unexamined Patent Publication No. 2010-117586 ). For example, it has been reported in Japanese Unexamined Patent Publication No. 2010-117586 that the use of two kinds of resins as the above-described binding resins can achieve high hardness of image surfaces.
It has also been reported that a toner for printing on the continuous sheet needs to have not only excellent fixability but also suppression of toner filming associated therewith (see, for example, Japanese Unexamined Patent Publication No. 2009-086642 ). For example, Japanese Unexamined Patent Publication No. 2009-086642 discloses a technique of adjusting the amounts of a crystalline polyester, a wax, and an external additive to be blended in the toner. According to the technology described in Japanese Unexamined Patent Publication No. 2009-086642 , it is said that both fixability and filming resistance can be achieved.
However, in order to perform printing on the long sheet, characteristics for suppressing transfer failure at the trailing end of the image are required in addition to excellent fixability as described above, and there is a problem in that sufficient image stability cannot be realized only by the invention as described above. That is, in the case of printing on a long sheet, there has been a problem that the transfer property is less likely to be stable at the trailing end of the image and transfer failure tends to occur.

SUMMARY OF THE INVENTION

The present invention has been made in consideration of the above-mentioned problems and situations. An object of the present invention is to provide an image forming method capable of forming an image having excellent fixability to a recording medium long in a sheet conveyance direction, such as a long sheet, stable transferability at a leading end and a trailing end, and uniform image density and gloss at the leading end and the trailing end.
In order to solve the above-described problem, the inventor of the present invention focused on an electrical resistance value of a long sheet at the time of printing on the long sheet and conducted intensive studies.
As a result, the present inventors have found that, when printing is performed on a long sheet, the electrical resistance value of the sheet changes depending on the fixed toner image at a leading end portion of the image. Then, it has been found that due to the effect thereof, the electrostatic capacitance of the sheet at the time of transfer at a trailing end portion of the image not fixed yet is changed and therefore electric discharge is liable to occur and thus the transfer failure is liable to occur. With respect to such a transfer failure, it has been found that the transfer property at the leading end and the trailing end of the toner image is stabilized by suppressing an increase in resistance of the toner image printed on the long sheet, and thus the present invention has been achieved. That is, the above-described problems according to the present invention are solved by the following means.
According to one aspect of an image forming method of the present invention, an image forming method forms an image on at least a long sheet by using toner containing at least a binding resin, a wax and an external additive, the method including: preparing the binding resin as a mixture of at least a crystalline polyester resin and an amorphous polyester resin, and preparing a content rate of a saturated hydrocarbon compound having 16 to 35 carbon atoms in the toner to be 1 to 1000 ppm by mass.
According to another aspect, the image forming method according to aspect 1, wherein a length of the long sheet is longer than or equal to 900 mm.
According to another aspect, the image forming method according to aspect 2, wherein the length of the long sheet is longer than or equal to 1300 mm.
According to another aspect, the image forming method according to aspect 1 or 2, wherein the wax includes at least a hydrocarbon wax.
According to another aspect, the image forming method according to aspect 1 or 2, wherein the content rate of the saturated hydrocarbon compound having 16 to 35 carbon atoms in the toner is 100 to 700 ppm by mass.
According to another aspect, the image forming method according to aspect 1 or 2, wherein the toner is charged on a surface of a developing roller using a restricting blade.
According to another aspect, the image forming method according to aspect 1 or 2, wherein the amorphous polyester resin includes the amorphous polyester resin having a vinyl resin segment containing at least a constitutional unit derived from a vinyl monomer.
According to another aspect, the image forming method according to aspect 1 or 2,

wherein the external additive includes at least a fine particle A that has a particle size of 80 nm or more and less than 200 nm which can be confirmed by observing the toner with a scanning electron microscope, and
wherein an average coverage of the fine particle A on the toner as determined by an analysis of the image of the toner by the scanning electron microscope is 5% by area or more and 40% by area or less.

According to another aspect, the image forming method according to aspect 1 or 2,

wherein the external additive includes at least a fine particle B that has a particle size of 200 nm or more and 500 nm or less which can be confirmed by observing the toner with a scanning electron microscope, and
wherein an average coverage of the fine particle B on the toner as determined by an analysis of the image of the toner by the scanning electron microscope is 0.1% by area or more and 5% by area or less.

According to another aspect, the image forming method according to aspect 1 or 2, wherein the toner has a circularity of 0.950 to 0.990.
According to another aspect. the image forming method according to aspect 1 or 2, wherein a content of the crystalline polyester resin in the toner is 2 to 20% by mass.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages and features provided by one or more embodiments of the invention will become more fully understood from the detailed description given hereinafter and the appended drawings which are given by way of illustration only, and thus are not intended as a definition of the limits of the present invention, and wherein:

FIG. 1 is a diagram schematically illustrating a configuration example of an image forming apparatus;
FIG. 2 is an explanatory cross-sectional view illustrating an example of a configuration of a developing cartridge of a mono-component developer;
FIG. 3 is a schematic diagram illustrating behavior of a wax during fixing of a toner image formed by a conventional image forming method;
FIG. 4 is a schematic diagram illustrating the behavior of the wax during fixing of the toner image formed by the conventional image forming method;
FIG. 5 is a schematic diagram illustrating the behavior of the wax during fixing of the toner image formed by the image forming method of the present invention; and
FIG. 6 is a schematic diagram illustrating the behavior of the wax during fixing of the toner image formed by the image forming method of the present invention.

DETAILED DESCRIPTION

Hereinafter, one or more embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the disclosed embodiments.
An embodiment of the image forming method of the present invention is an image forming method for forming an image on at least a long sheet of paper using a toner containing at least a binding resin, a wax, and an external additive. The image forming method of the present embodiment is characterized in that the above-described binding resin is a mixture of at least a crystalline polyester resin and an amorphous polyester resin, and a content rate of a saturated hydrocarbon compound having 16 to 35 carbon atoms in the toner is 1 to 1000 ppm by mass. According to the image forming method configured as described above, it is possible to form the image having excellent fixability to a recording medium which is long in a conveyance direction such as a long sheet, stable transferability at a leading end and a trailing end, and uniform image density and gloss at the leading end and the trailing end.
In the image forming method according to the present embodiment, the long sheet refers to a sheet having a special size whose length in the conveyance direction of the sheet is longer than the sheet feed tray. Furthermore, the long sheet includes a roll-shaped continuous sheet. Hereinafter, the length of the long sheet in the conveyance direction may be simply referred to as the "length of the long sheet". The length of the long sheet is not particularly limited, and for example, the length of the long sheet is preferably equal to or longer than 900 mm, and more preferably equal to or longer than 1300 mm. As the length of the long sheet as a recording material becomes longer, it is possible to suppress an increase in resistance due to the fixed toner image, and the above-described effect of the present invention is easily obtained.
The wax contained in the toner preferably contains at least a hydrocarbon wax. The hydrocarbon wax has a molecular structure similar to that of a saturated hydrocarbon compound having 16 to 35 carbon atoms, and has an advantage that the saturated hydrocarbon compound is easily compatibilized with a release agent.
The content rate of the saturated hydrocarbon compound having 16 to 35 carbon atoms in the toner is preferably 100 to 700 ppm by mass. With this structure, an effect of enhancing releasability of the toner from a fixing member or the like to a predetermined extent can also be expected while an increase in the resistance of the toner image is suppressed.
From the viewpoint of downsizing the image forming apparatus, the toner is preferably charged on a surface of a developing roller by using a restricting blade. A developing device is roughly classified into a two component developing method in which development is performed with a two component developer mainly containing the toner and a carrier, and a mono-component developing method in which development is performed with a mono-component developer mainly containing no carrier. In the developing device of the mono-component developing method, a restricting member such as a blade comes into contact with a toner layer instead of a carrier to charge the toner. In order to reduce the size of the apparatus, mono-component development is preferably adopted.
The amorphous polyester resin preferably includes the amorphous polyester resin having a vinyl resin segment including at least a constituent unit derived from a vinyl monomer. When such an amorphous polyester resin is included, hydrophilicity is high and moisture in the air is more adsorbed, and therefore, an increase in resistance of the toner image is suppressed, and affinity between the resin and the wax is further decreased, and therefore, the wax can be locally disposed.
The external additive may contain at least a fine particle A having a particle size of 80 nm or more and less than 200 nm, which can be confirmed by observing the toner with a scanning electron microscope. In a case where the external additive contains such the fine particle A, an average coverage of the fine particle A on the toner as obtained by an analysis of the image of the toner by the scanning electron microscope is preferably 5% by area or more and 40% by area or less. Such fine particle A serves as a spacer between the toner and the photoreceptor without being buried in the surface of the toner base, and transfer failure is less likely to occur because of improved transferability.
The external additive may contain at least a fine particle B having a particle size of 200 nm or more and 500 nm or less, which can be confirmed by observing the toner with the scanning electron microscope. In a case where the external additive contains such a fine particle B, an average coverage of the fine particle B on the toner as determined by an analysis of the image of the toner by the scanning electron microscope is preferably at least 0.1% by area and no greater than 5% by area. When the fine particle B is added in a small amount, the spacer effect is further exhibited and the transferability can be improved.
Circularity of the toner is preferably 0.950 to 0.990. With such a configuration, the transferability of the toner can be satisfactorily secured, and an appropriate adhesion force can be secured, so that satisfactory transferability can be obtained.
Content of the crystalline polyester resin in the toner is preferably from 2 to 20% by mass from the viewpoint of excellent fixability and suppression of an increase in resistance of the toner.
Hereinafter, the present invention, constituent elements thereof, and forms and aspects for carrying out the present invention will be described in detail. In the present application, "to" representing a numerical range is used to mean that numerical values described before and after "to" are included as a lower limit value and an upper limit value.

[1. Outline of Image Forming Method]

Hereinafter, an embodiment of the image forming method of the present invention will be described, but the present invention is not limited thereto. The image forming method according to the present embodiment is an image forming method in which an image is formed on at least a long sheet using a toner containing at least a binding resin, a wax, and an external additive. The image forming method according to the present embodiment is characterized in that the binding resin contained in the toner is a mixture of at least a crystalline polyester resin and an amorphous polyester resin, and the content rate of a saturated hydrocarbon compound having 16 to 35 carbon atoms in the toner is 1 to 1000 ppm by mass. According to the image forming method configured as described above, it is possible to form the image having excellent fixability to a recording medium which is long in a conveyance direction such as a long sheet, stable transferability at a leading end and a trailing end, and uniform image density and gloss at the leading end and the trailing end.

[2. Long Sheet]

The long sheet is a special size sheet whose length in the sheet conveyance direction is longer than the sheet feeding tray. The length of the long sheet in the conveyance direction is not particularly limited. For example, it may be equal to or longer than 900 mm, or even equal to or longer than 1300 mm, of the long sheet in the conveyance direction. Hereinafter, the length of the long sheet in the conveyance direction may be simply referred to as the "length of the long sheet". Furthermore, the long sheet includes a roll-shaped continuous sheet.
The image forming method according to the present embodiment can more effectively suppress increase in resistance due to the fixed toner image as the length of the long sheet increases. For this reason, in the image forming method of the present embodiment, in particular, in the image forming method of forming the image on the long sheet using the toner, it is easy to obtain an effect that excellent fixability and transferability at the leading end and the trailing end is stabilized and the image having uniform image density and gloss at the leading end and the trailing end can be formed.

[3. Toner]

The toner used in the image forming method according to the present embodiment contains at least the binding resin, the wax, and the external additive. The binding resin contained in the toner is a mixture of at least the crystalline polyester resin and the amorphous polyester resin. Furthermore, the content rate of the saturated hydrocarbon compound having 16 to 35 carbon atoms in the toner is 1 to 1000 ppm by mass. Hereinafter, the saturated hydrocarbon compound having 16 to 35 carbon atoms contained in the toner used in the image forming method of the present embodiment may be referred to as a "specific saturated hydrocarbon compound". That is, in the image forming method of the present embodiment, it is preferable to form the image at least on the long sheet using the toner in which the content rate of the specific saturated hydrocarbon compound is from 1 to 1000 ppm by mass.
In the present invention, the term "toner" refers to an aggregate of toner particles. The toner particles may be formed of only toner base particles, or may be formed of toner base particles and an external additive to be adhered to surfaces of the toner base particles. The "toner base particles" are particles constituting a base of toner particles. Examples of the toner include an electrostatic charge image developing toner for developing an electrostatic charge image (electrostatic latent image) formed on an image bearing member such as a photoreceptor.

Any known polymer can be used as the binding resin contained in the toner particles, and specifically, for example, the following polymers can be used. Examples of polymers that can be used in the binding resin include homopolymers of styrene and substituted derivatives thereof, such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene; styrene-based copolymers such as styrene-p-chlorostyrene copolymers, styrene-vinyltoluene copolymers, styrene-vinylnaphthalene copolymers, styrene-acrylate ester copolymers, styrene-methacrylate ester copolymers, styrene-α-chloromethyl methacrylate copolymers, styrene-acrylonitrile copolymers, styrene-vinyl methyl ether copolymers, styrene-vinyl ethyl ether copolymers, styrene-vinyl methyl ketone copolymers, and styrene-acrylonitrile-indene copolymers; polyvinyl chloride, phenol resins, natural resin-modified phenol resins, natural resin-modified maleic acid resins, acrylic resins, methacrylic resins, polyvinyl acetate, silicone resins, polyesters, polyurethanes, polyamides, furan resins, epoxy resins, xylene resins, polyvinyl butyral, terpene resins, coumarone-indene resins, and petroleum-based resins. These resins may be used alone or in combination of two or more kinds thereof.

(Amorphous Polyester Resin)

The binding resin contains the amorphous polyester resin. The amorphous polyester resin is obtained by a polycondensation reaction using a polyvalent carboxylic acid monomer (derivative) and a polyhydric alcohol monomer (derivative) as raw materials, and does not have a clear melting point. Since the amorphous polyester resin has high hydrophilicity and moisture in the air is more adsorbed, an increase in resistance of the toner image is suppressed, and affinity between the resin and the wax is further decreased, and therefore, the wax can be locally disposed.
The amorphous polyester resin is preferably contained in an amount of 60% by mass or more, and more preferably 80% by mass or more, relative to the total mass of the binding resin.
Furthermore, the amorphous polyester resin is preferably an amorphous polyester resin having a vinyl resin segment containing at least a constituent unit derived from a vinyl monomer. By having a vinyl resin segment, the dispersibility of the wax in the toner is increased, and therefore, an increase in the resistance of the toner image due to the wax domain can be suppressed. The wax domain means a domain phase of the wax in a phase-separated structure in which the domain phase of the wax is dispersed in a matrix phase of the resin.
Examples of the vinyl monomer include styrene-based monomers and (meth) acrylic acid ester-based monomers. Examples of the vinyl monomer include olefins, vinyl esters, vinyl ethers, vinyl ketones, and N-vinyl compounds, in addition to the monomers described above. Examples of the olefins include ethylene, propylene, and isobutylene. Examples of the vinyl esters include vinyl propionate, vinyl acetate, and vinyl benzoate. Examples of the vinyl ethers include vinyl methyl ether and vinyl ethyl ether. Examples of the vinyl ketones include vinyl methyl ketone, vinyl ethyl ketone, and vinyl hexyl ketone. Examples of the N-vinyl compounds include N-vinylcarbazole, N-vinylindole, and N-vinylpyrrolidone. Furthermore, other examples of the vinyl monomer include vinyl compounds such as vinylnaphthalene and vinylpyridine, and acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide.
Examples of the styrene-based monomer include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, p-ethylstyrene, p-n-butylstyrene, p-tert-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene, p-n-dodecylstyrene, 2,4-dimethylstyrene, 3,4-dichlorostyrene and the like, and derivatives thereof.
Examples of the (meth) acrylic acid ester monomer include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, ethyl β-hydroxyacrylate, propyl γ-aminoacrylate, stearyl methacrylate, dimethylaminoethyl methacrylate, and diethylaminoethyl methacrylate.
Each of the styrene-based monomer and the (meth) acrylic acid ester-based monomer described above can be used alone or in combination of two or more kinds thereof.
The polyester resin having a vinyl resin segment may be formed by bonding a vinyl resin segment to a polyester polymerization segment. The vinyl resin segment may be bonded as a branched chain in the chain of the polyester polymerization segment, or may be bonded in a state of constituting a straight chain. In a case of constituting a straight chain, it may constitute any of the middle and the end of the straight chain.
A dually reactive monomer may be used for bonding the polyester polymerization segment and the vinyl resin segment described above. The dually reactive monomer may be any monomer having a polymerizable unsaturated group and a group reactive with a polyvalent carboxylic acid monomer and/or a polyhydric alcohol monomer for forming the polyester polymerization segment. Specifically, for example, acrylic acid, methacrylic acid, fumaric acid, maleic acid, and maleic anhydride can be used.
The amorphous polyester preferably has a softening point of 70°C or higher and 140°C or lower. Furthermore, the temperature is more preferably 90°C or more and 120°C or less. If the softening point is higher than 70°C, the specific hydrocarbon compound included in the toner is likely to be disposed on the surface of the toner image. If the softening point is lower than 140°C, the toner has excellent fixing performance and image gloss difference at the leading end and the trailing end of the long sheet is unlikely to occur.
The amorphous polyester preferably has a glass transition temperature of 30°C or more and 70°C or less. Furthermore, the temperature is more preferably 40°C or more and 60°C or less. When the glass transition temperature is higher than 30°C, even in a case where printing or the like is continuously performed on the long sheet for a long time, the occurrence of toner filming can be effectively suppressed. Furthermore, when the glass transition temperature is lower than 70°C, the toner has excellent fixability, and image gloss difference is less likely to occur between the leading end and the trailing end of the long sheet.

(Crystalline Polyester Resin)

The binding resin contains the crystalline polyester resin. Inclusion of the crystalline polyester resin contributes to excellent fixability and suppression of an increase in resistance of the toner image. The crystalline polyester resin is obtained by a dehydration condensation reaction of a polyvalent carboxylic acid and a polyhydric alcohol. The term "crystalline" means having a melting point. In other words, the term "crystalline" refers to having a clear endothermic peak during temperature increase in an endothermic curve obtained by differential scanning calorimetry (DSC). The "clear endothermic peak" refers to a peak having a half value width of 15°C or less in an endothermic curve when the temperature is increased at a temperature increase rate of 10°C/min.
Preferably, the polyvalent carboxylic acid is a carboxylic acid having a valency of 2 or greater. The polyvalent carboxylic acid may be a carboxylic acid having a valency of 3 or greater, such as trimellitic acid or pyromellitic acid. Among these, a dicarboxylic acid is preferable from the viewpoint of enhancing excellent fixability. Examples of dicarboxylic acids include: aliphatic carboxylic acids such as 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, and 1,18-octadecanedicarboxylic acid; and aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, t-butylisophthalic acid, 2,6-naphthalenedicarboxylic acid, and 4,4'-biphenyldicarboxylic acid.
Among these polyvalent carboxylic acids, an aliphatic carboxylic acid is preferable because excellent fixability is easily obtained. Preferably, the aliphatic carboxylic acid has a linear hydrocarbon group having 6 to 16 carbon atoms, and more preferably, has a linear hydrocarbon group having 10 to 14 carbon atoms. The hydrocarbon structure of the aliphatic carboxylic acid may be partially branched.
Preferably, the polyhydric alcohol is an alcohol having a valency of 2 or greater. The polyhydric alcohol may be an alcohol having a valency of 3 or greater, such as glycerol, pentaerythritol, trimethylolpropane, or sorbitol. Among the above, dihydric alcohols are preferable to increase the crystallinity of the crystalline polyester. Examples of a dihydric alcohol include aliphatic diols such as 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; diols having unsaturated double bonds such as 2-butene-1,4-diol, 3-hexene-1,6-diol, and 4-octene-1,8-diol; and diols having a sulfonic acid group.
The content of the crystalline polyester resin is preferably 2% by mass or more and 20% by mass or less, more preferably 5% by mass or more and 15% by mass or less relative to the total mass of the binding resin. When the content of the crystalline polyester resin is 2% by mass or more, a sufficient amount of the crystalline polyester resin is present in the binding resin, and the effects of excellent fixability and suppressing an increase in resistance of the toner image are more favorably exhibited. When the content of the crystalline polyester resin is more than 20% by mass, the bleeding of the specific hydrocarbon compound is inhibited, and thus the intended effect is not sufficiently exhibited.
A weight-average molecular weight (Mw) of the crystalline polyester resin is preferably 5000 or more and 50000 or less. A number-average molecular weight (Mn) of the crystalline polyester resin is preferably 2000 or more and 10000 or less. When the weight-average molecular weight (Mw) and the number-average molecular weight (Mn) of the crystalline polyester resin are within the aforementioned numerical ranges, the fixing performance becomes satisfactory. The weight-average molecular weight (Mw) and the number-average molecular weight (Mn) can be measured by gel permeation chromatography (GPC).
The melting point of the crystalline polyester resin is preferably 50°C or more and 100°C or less. Furthermore, the temperature is more preferably 60°C or more and 80°C or less. When the melting point of the crystalline polyester resin is higher than 50°C, the specific hydrocarbon compound is likely to be disposed on the surface of the toner image. For example, since the specific hydrocarbon compound is easily disposed on the surface of the toner image, an effect that the wax is not easily volatilized at the time of fixing can also be expected. Excessive volatilization of the wax to form fine particles during fixing is not preferable in terms of environmental load. In addition, when the melting point of the crystalline polyester resin is lower than 100°C, the fixing property becomes satisfactory.

<Wax>

The toner used in the image forming method of the present embodiment contains the wax. The wax is not particularly limited, and examples thereof include low molecular weight polyethylene wax, low molecular weight polypropylene wax, Fischer - Tropsch wax, microcrystalline wax, and hydrocarbon waxes such as paraffin wax, dialkyl ketone wax including distearyl ketone and the like, ester waxes including carnauba wax, montan wax, behenic acid behenate, trimethylolpropane tribehenate, pentaerythritol tetramyristate, pentaerythritol tetrastearate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerol tribehenate, 1,18-octadecanediol distearate, tristearyl trimellitate, and distearyl maleate and the like, and amide waxes including ethylenediamine dibehenylamide, and trimellitic acid tristearylamide, and the like. These may be used alone or in combination of two or more. Among these, the hydrocarbon wax is preferable because the hydrocarbon wax has a molecular structure similar to that of the specific saturated hydrocarbon compound having 16 to 35 carbon atoms and the specific saturated hydrocarbon compound is easily compatible with the release agent (that is, wax). When the specific saturated hydrocarbon compound and the wax are satisfactorily compatible with each other, the wax can be locally disposed on the surface of the toner image, and an increase in resistance can be prevented.
The melting point of the wax is preferably 50°C or more and 100°C or less. Furthermore, the temperature is more preferably 60°C or higher and 90°C or lower. When the melting point of the wax is higher than 50°C, the wax does not excessively ooze out on the surface of the image during fixing, and an increase in resistance can be suppressed. In addition, when the melting point of the wax is lower than 90°C, the wax is melted, and thus it is possible to secure separation performance from the fixing member.
The content ratio of the wax is preferably 2 to 20% by mass, more preferably 3 to 10% by mass with respect to the total amount of the binding resin. If the content of the wax is 2% by mass or more, a sufficient amount of the wax is present and separation performance from the fixing member can be ensured. When the content of the wax is 20% by mass or less, an increase in the resistance of the toner image can be more effectively suppressed.

In the image forming method according to the present embodiment, the content rate of the saturated hydrocarbon compound having 16 to 35 carbon atoms in the toner is 1 to 1000 ppm by mass. Due to the above-described operation, the saturated hydrocarbon compound having 16 to 35 carbon atoms suppresses an increase in the resistance of the toner image. On the other hand, the saturated hydrocarbon compound having 16 to 35 carbon atoms also has an effect of enhancing the releasability of the toner from the fixing member or the like to a predetermined extent.
Therefore, the wax (release agent) contained in the toner may be used as the first release agent, and the saturated hydrocarbon compound having 16 to 35 carbon atoms may be contained in the toner base particles as the second release agent. For example, when the wax contained in the toner described above is used as the first release agent, the wax as the first release agent preferably does not contain a saturated hydrocarbon compound having 16 to 35 carbon atoms.
The content of the saturated hydrocarbon compounds having 16 to 35 carbon atoms is 1 ppm or more and 1000 ppm or less relative to the total mass of the toner (mass including the toner base particles and the external additive). The content of the saturated hydrocarbon compounds having 16 to 35 carbon atoms is preferably 50 ppm or more and 900 ppm or less, more preferably 100 ppm or more and 700 ppm or less, relative to the total mass of the toner. When the content is 1 ppm or more, a sufficient amount exists and the intended effect can be exhibited. When the content is 1000 ppm or less, the wax is appropriately locally arranged, and thus an intended effect can be exhibited.
The saturated hydrocarbon compound having 16 to 35 carbon atoms may be, for example, a straight-chain saturated hydrocarbon compound having 16 to 35 carbon atoms, or a saturated hydrocarbon compound having 16 to 35 carbon atoms and including a branched structure. The saturated hydrocarbon compound having 16 to 35 carbon atoms may have a cyclic structure.
The content of the saturated hydrocarbon compounds having 16 to 35 carbon atoms (hereinafter, also referred to as "specific saturated hydrocarbon compounds") can be determined by the following method. First, the specific saturated hydrocarbon compound is separated from the toner using a solvent that dissolves the specific saturated hydrocarbon compound. Next, the specific saturated hydrocarbon compound separated in the solvent is qualified by gas chromatography-mass spectrometry (GC-MS). In addition, the specific saturated hydrocarbon compound separated in the solvent is quantified by gas chromatography (GC-FID) of a hydrogen flame ion detection system using a hydrogen flame ionization detector (FID) as a detector. Since the extracts from the toner may contain unsaturated hydrocarbon compounds, polar groups are applied to the unsaturated bonds after the extraction, so that only the saturated hydrocarbons are separated by column separation utilizing the polarity difference.
At this time, some internal standard substances may be added to (dissolved in) the solvent to determine whether the quantification and the pretreatment thereof have been appropriately performed. Note that the concentration of the internal standard substance to be added may be set according to the amount (the expected amount obtained by preliminary measurement or the like) of the saturated hydrocarbon compound having 16 to 35 carbon atoms.
The internal standard substances are preferably saturated hydrocarbon compounds that are not usually contained in the toner. For example, use of N-undecane or N-tridecane allows detection of disappearance of saturated hydrocarbon compounds during the pretreatment due to volatilization and also allows estimation of an elution time of target saturated hydrocarbon compounds during solid-phase extraction or analysis by GC-FID. Furthermore, elution times of bicyclohexyl and the specific saturated hydrocarbon compound are less likely to overlap each other, and thus the detection accuracy is likely to be increased.
The extraction from the toner can be performed by a conventionally known method such as a solid-liquid extraction method, a method of dissolving or swelling a toner and then separating by centrifugation, a Soxhlet extraction method, or a high-speed solvent extraction method. The method may be selected from these methods according to the predicted number of carbon atoms of the specific saturated hydrocarbon compound or the type of a compound serving as an impurity component such as a binding resin.
The solvent used for the extraction is not particularly limited, but N-hexane in which the specific saturated hydrocarbon compound has high solubility is preferable. To swell the binding resin, a polar solvent such as dichloromethane and ethanol may also be used depending on the type of the binding resin.
The method for introducing the polar group into the unsaturated hydrocarbon compound contained in the extract is not particularly limited. Examples of the method for introducing the polar group into the unsaturated hydrocarbon compound include epoxidation with metachloroperbenzoic acid (mCPBA), addition of hydrogen halide, addition of water or alcohol with an acid catalyst, and derivation to alcohol by oxidation after hydroboration. Among these, the epoxidation reaction using mCPBA is preferable because of high reactivity and reaction selectivity. At this time, it is possible to confirm that the reaction has sufficiently proceeded, for example, by confirming the disappearance of the peak of double bonds by ¹H -NMR measurement. When sufficient detection accuracy can be ensured depending on the type of the saturated hydrocarbon compound or the type of the unsaturated hydrocarbon compound, the addition of the polar group may be omitted.
The separation by a polarity difference can be done according to a known method, such as solid-phase extraction or online or offline GC. When a large amount of impurities is expected to be contained, separation by solid-phase extraction is preferable.
As the solvent used in the separation by solid phase extraction, N-hexane is preferably used in both the conditioning and the extraction of the saturated hydrocarbon compound. A polar solvent may also be used depending on the kind of expected impurities. After the fraction containing the saturated hydrocarbon compound having 16 to 35 carbon atoms is collected, it is preferable that the polarity of the solvent is increased, the fraction is collected, and it is confirmed that the component of the saturated hydrocarbon compound is not contained by qualitative analysis by GC/MS or the like.
As the solid phase for solid-phase extraction, a highly polar solid phase used for separation of a normal phase system using a polar interaction can be used. Examples of the solid phase include silica gel, silica gel activated with a polar substance such as anhydrous sodium sulfate and silver nitrate, diol, cyanopropyl, and magnesium silicate. Of these, silica activated with silver nitrate is preferable. To specifically retain a long-chain N-alkane, alumina is not preferable.
The fraction containing the saturated hydrocarbon compound extracted by the solid-phase extraction is preferably concentrated or diluted to a concentration appropriate for qualitative and quantitative determination by gas chromatography. Examples of the method for concentrating the fraction containing the extracted saturated hydrocarbon compound include, but are not particularly limited to, methods such as concentration under reduced pressure with an evaporator and concentration with a nitrogen airflow. Conditions of concentration are determined such that under the conditions, the internal standard substances do not disappear owing to the concentration of low-boiling-point components.
The fraction after the solid phase extraction is subjected to, for example, GC-FID under the following conditions, and the saturated hydrocarbon compound having 16 to 35 carbon atoms can be quantified.

(GC conditions)

Instrument: GC-2010 Plus manufactured by Shimadzu Corporation
Injection amount: 1µL, concentration of saturated hydrocarbon: 500 to 1,000 mg/L
Guard column: Restek MXT Siltek (10 m × 0.53 mm id)
Column: Restek MTX-1 (15 m × 0.25 mm id) × 0. 1 µm df)
Carrier gas: helium

The quantification of the saturated hydrocarbon compound having 16 to 35 carbon atoms may be performed using an apparatus having the same performance as the above-described apparatus and a column having the same performance as the above-described column as long as a result equivalent to the above-described conditions is obtained.
The elution time of N-alkanes (the number of carbon atoms: 10, 16, 24, 35, and 50) is measured beforehand under the same conditions. Further, only N-hexane is injected in the apparatus beforehand to prepare a blank chromatogram.
To determine a baseline, the blank chromatogram obtained beforehand by measurement with the solvent alone is subtracted from the chromatogram obtained for the toner. It is preferable that the base line be a horizontal line at the lowest point before or after a peak, which is derived from the saturated hydrocarbon compounds. However, in the case where the baseline by the horizontal line cannot be prepared even by subtracting the blank chromatogram due to column bleeding or the like, the baseline may be set as follows. That is, from the elution time of the compound having 10 carbon atoms to the elution time of the compound having 50 carbon atoms, the baseline may be set with a horizontal line from the intensity of the lower signal intensity among the compound having 10 carbon atoms and the compound having 50 carbon atoms.
Next, in the chromatogram, perpendicular lines are drawn at positions corresponding to the elution time of the compound having 16 carbon atoms and the elusion time of the compound having 35 carbon atoms. Then, in the chromatogram above the baseline, the area surrounded by these perpendicular lines is calculated. Peaks not caused by saturated hydrocarbon compounds are excluded from the calculation. From this area, the mass of the saturated hydrocarbon compound having 16 to 35 carbon atoms can be determined. When the internal standard substance is used, the mass of the saturated hydrocarbon compound having 16 to 35 carbon atoms may be obtained from the ratio of the area to the area of the compound added as the internal standard. Then, the amount of the saturated hydrocarbon compound having 16 to 35 carbon atoms in the toner can be obtained by dividing the obtained mass of the saturated hydrocarbon compound having 16 to 35 carbon atoms by the mass of the toner.

The toner used in the image forming method according to the present embodiment contains the external additive. The inclusion of the external additive can enhance the fluidity, chargeability, and cleanability of the toner. The external additive is, for example, attached to the surface of the toner base particles as a post-treatment agent.
As the external additive, conventionally known metal oxide particles can be used. Examples thereof include silica particles, titania 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. Furthermore, the external additive may contain organic fine particles of a homopolymer of styrene, methyl methacrylate, or the like, a copolymer of these, or the like. Further, the external additive may contain organic fine particles such as melamine-based resin fine particles and polytetrafluoroethylene resin fine particles.
The external additive preferably contains at least fine particles A having a particle size of 80 nm or more and less than 200 nm, which can be confirmed by observing the toner with the scanning electron microscope. The average coverage of the fine particles A in the toner as obtained by the analysis of the image of the toner by the scanning electron microscope is more preferably 5% by area or more and 40% by area or less.
When the fine particles A having a particle size of 80 nm or more and less than 200 nm are contained, the transferability of the toner is improved, so that transfer failure hardly occurs. That is, when the particle size of the fine particle A is 80 nm or more, the fine particle A functions as a spacer between the toner and the photoreceptor without being buried in the surface of the toner base, and the transfer property is improved, so that the transfer failure hardly occurs. In addition, when the particle size of the fine particle A is less than 200 nm, the fine particle A is unlikely to be detached from the surface of the toner, and thus it is possible to stably exhibit the intended effect. The particle size of the fine particle A is more preferably 90 nm or more and 150 nm or less.
In addition, when the average coverage of the fine particles A on the toner is 5% by area or more, the fine particles A are uniformly present on the surface of the toner base, and the effect thereof can be favorably exhibited.
On the other hand, when the average coverage of the fine particles A in the toner is 40% by area or less, the aggregation of the fine particles A is easily broken up, and the fine particles A can be uniformly present on the surface of the toner base. The average coverage of the fine particles A in the toner is more preferably 20 to 30% by area.
The type of the fine particles A as the external additive is not particularly limited, and the particles that can be used as the external additive described above can be used. In particular, as the fine particles A as the external additive, silica particles having a specific gravity similar to that of the resin can be more suitably used from the viewpoint of suppression of embedding in the resin constituting the toner under stress and prevention of separation.
In addition, the external additive may contain at least the fine particle B having the particle size of 200 nm or more and 500 nm or less, which can be confirmed by observing the toner with the scanning electron microscope. The toner preferably has the average coverage of the fine particles B of 0.1% by area or more and 5% by area or less as obtained by the analysis of the image of the toner by the scanning electron microscope. When the fine particle B having a particle size of 200 nm or more and 500 nm or less is contained in a small amount relative to the fine particle A, the effect as the spacer described above is more likely to function, and the transferability is further improved. For example, when the particle size of the fine particles B is 200 nm or more, the fine particles B are not buried in the surface of the toner base, and the effect thereof can be effectively exhibited. In addition, when the particle size of the fine particle B is 500 nm or less, the fine particle B is unlikely to be detached from the surface of the toner base, and thus the intended effect can be stably exhibited. In addition, when the average coverage of the fine particles B on the toner is 0.1% by area or more, the fine particles B are uniformly present on the surface of the toner base, and the effect thereof can be exhibited. On the other hand, when the average coverage of the fine particles B in the toner is 5% by area or less, the aggregation of the fine particles B is easily loosened, and the fine particles B can be uniformly present on the surface of the toner base. It is more preferable that the average coverage by the fine particles B of the toner is 1 to 3% by area.
The type of the fine particles B as the external additive is not particularly limited, and the particles that can be used as the external additive described above can be used. The fine particle B is preferably an organic fine particle in order to improve affinity with the toner and prevent separation.

(Method for Measuring Particle Size of External Additive)

The particle size of the particles constituting the external additive (hereinafter, also referred to as "external additive fine particles") can be measured by the following method. Using a scanning electron microscope (SEM) "JEM-7401F" (manufactured by JEOL Ltd), a SEM photograph of the toner is taken at a magnification of 50,000 times. The photographed SEM photograph of the toner is observed, and the particle size (Feret diameter) of a primary particle of the external additive fine particle is measured and obtained. The same operation is performed for 30 toner particles. Among the external additive fine particles whose particle size has been measured in this manner, the external additive fine particles whose particle size is 80 nm or more and less than 200 nm are referred to as the above-described "fine particles A". Among the external additive fine particles whose particle size has been measured, those having a particle size of 200 nm or more and 500 nm or less are referred to as the above-described "fine particles B".

(Method for Calculating Average Coverage of External Additive Fine Particles of Toner)

The average coverage of the external additive fine particles (fine particles A or fine particles B) on the toner can be determined by the following method. First, a coverage area SA of the fine particles A and a coverage area SB of the fine particles B are calculated by image processing using image processing software using the SEM photograph obtained by the above-described method for measuring the particle size of the external additive. As the image processing software, "ImageJ" (open source) is used. To be specific, the fine particles having the particle size corresponding to the fine particles A are manually surrounded by using "Polygon selections tool" of "ImageJ", and the coverage area SA of the fine particles A is calculated. Similarly, the fine particles having the particle size corresponding to the fine particle B are manually surrounded using the tool, and the coverage area SB of the fine particles B is calculated. Further, the area S of the toner surface is also calculated in the same manner. The coverage (% by area) of the fine particles A in the toner can be calculated by SA/S × 100%. The coverage (% by area) of the fine particles B of the toner can be calculated by SB/S × 100%.
Then, the same operation is performed for 30 toner particles, and the coverage (% by area) of the fine particles A and the coverage (% by area) of the fine particles B are calculated for 30 toner particles. Then, the average value of the coverage (% by area) of the fine particles A for 30 toner particle is defined as the average coverage (% by area) of the fine particles A of the toner. Similarly, the average value of the coverage (% by area) of the fine particles B for 30 toner particles is defined as the average coverage (% by area) of the fine particles B of the toner.

(Circularity of Toner)

The toner preferably has a circularity of 0.950 to 0.990. That is, the toner base particles preferably have a circularity of 0.950 or more and 0.990 or less, and more preferably 0.960 or more and 0.980 or less. By setting the circularity of the toner base particles to 0.950 or more, transferability can be secured. By setting the circularity of the toner base particles to 0.990 or less, an appropriate adhesion force is secured, and good transferability is obtained.

(Method for Measuring Circularity of Toner)

The circularity of the toner can be measured using a flow-type particle image analyzer "FPIA 2100" (manufactured by Sysmex Corporation). Specifically, the toner particles are wetted with an aqueous surfactant solution and subjected to ultrasonic dispersion for 1 minute, after the dispersion, measurement is performed with "FPIA-3000" under measurement conditions of an HPF (high-power field imaging) mode at an appropriate concentration with an HPF detection number of 3000 to 10000. Within this range, a reproducible measurement value can be obtained.
The circularity is calculated by the following formula. Circularity = (perimeter of a circle having the same projected area as a particle image)/(perimeter of a particle projection image)
The average circularity is an arithmetic average value obtained by adding up the circularities of the respective particles and dividing the sum by the total number of the measured particles.

(Particle Size of Toner)

The toner base particles preferably have a volume-based average particle size (volume average particle size) of 3.0 µm or more and 10.0 µm or less, more preferably 4.0 µm or more and 8.0 µm or less, still more preferably 4.0 µm or more and 7.0 µm or less. When the volume-based average particle size of the toner base particles is 3.0 µm or more, appropriate adhesive force is ensured, and satisfactory transferability is obtained. On the other hand, setting the volume-based average particle size of the toner base particles to 10.0 µm or less can facilitate the exudation of the saturated hydrocarbon compound having 16 to 35 carbon atoms.
The volume-average particle size of the toner base particles can be measured using a measurement apparatus in which a particle size distribution measurement apparatus (Coulter Multisizer 3, manufactured by Beckman Coulter, Inc.) is connected to a computer system equipped with data-processing software Software V3.51. To be specific, a sample of 0.02 g (toner base particles) is added to and settled in a surfactant solution of 20 mL, and then subjected to ultrasonic dispersion treatment for 1 minute to prepare a dispersion liquid of toner base particles. Note that as the above-described surfactant solution, for example, a surfactant solution obtained by diluting a neutral detergent containing a surfactant component with pure water by 10 times can be used for the purpose of dispersing the toner base particles. The dispersion liquid prepared as described above is poured into a beaker containing an electrolytic solution (ISOTONII, manufactured by Beckman Coulter, Inc.) in a sample stand, with a pipette, until a display concentration on the measurement device becomes 8%. By setting the concentration in this range, a reproducible measurement value can be obtained. Next, in the measurement device, the number of counted measured particles is set to 25000, the aperture diameter is set to 100 µm, the frequency value is calculated by dividing the range of 2 to 60 µm that is the measurement range into 256 parts, and based on this, the volume-based average particle size is calculated.

The toner may contain a colorant, a charge control agent, and the like.

(Colorant)

The coloring agent may be a dye or a pigment. When the toner has a color to impart a predetermined color tone to images, the toner base particles may contain a colorant agent, such as yellow, magenta, cyan, or black, corresponding to the color tone to be imparted by the color toner. The toner base particles may contain a single kind of colorant agent or a combination of multiple kinds of colorant agent.
Examples of yellow colorants include yellow dyes such as C. I. Solvent Yellow 19, 44, 77, 79, 81, 82, 93, 98, 103, 104, 112, and 162. Furthermore, examples of a yellow colorant include yellow pigments such as C. I. Pigment Yellow 14, 17, 74, 93, 94, 138, 155, 180, and 185.
Examples of magenta colorants include magenta dyes such as C. I. Solvent Red 1, 49, 52, 58, 63, 111, and 122. Furthermore, examples of a magenta colorant include magenta pigments such as C. I. Pigment Red 5, 48:1, 53:1, 57:1, 122, 139, 144, 149, 166, 177, 178, and 222.
Examples of a cyan colorant include cyan dyes such as C. I. Solvent Blue 25, 36, 60, 70, 93, and 95, and cyan pigments such as C. I. Pigment Blue 1, 7, 15, 15:3, 60, 62, 66, and 76.
Examples of black colorants include carbon blacks such as channel black, furnace black, acetylene black, thermal black, and lamp black; magnetic materials such as ferrite and magnetite; and iron-titanium composite oxide.
The content of the colorant is preferably 0.5% by mass or more and 20% by mass or less and more preferably 2% by mass or more and 10% by mass or less relative to the total mass of the toner base particles. When the toner is a clear toner, it is preferable that the toner base particles do not substantially contain the colorant agent and that the content of the colorant be preferably equal to or less than 0.1% by mass with respect to the total mass of the toner base particles.

(Charge Control Agent)

The charge control agent can adjust the chargeability of the toner base particles.
Examples of the charge control agent include nigrosine dyes, metal salts of naphthenic acid or higher fatty acids, alkoxylated amines, quaternary ammonium salt compounds, azo metal complexes, and metal salts of salicylic acid or metal complexes thereof.
The content of the charge control agent is preferably 0.1% by mass or more and 10% by mass or less, more preferably 0.5% by mass or more and 5% by mass or less relative to the total mass of the binding resin. Adding an excessive amount of the charge control agent to control the chargeability of the toner may significantly change other properties of the toner base particles. On the other hand, when the chargeability of the toner is adjusted by strontium titanate, the chargeability of the toner can be adjusted to a desired level while satisfying other required characteristics.

(Other External Additives)

As the external additive, other known external additives may be contained in addition to the fine particles A and the fine particles B described above.
As the known external additive, for example, inorganic fine particles, organic fine particles, and a lubricant, which will be described later, can be used.
As the other external additives, conventionally known metal oxide particles can be used for the purpose of controlling fluidity and chargeability. Examples thereof include silica particles, titania 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. These may be used alone or in combination of two or more thereof. Furthermore, the external additive may contain organic fine particles of a homopolymer of styrene, methyl methacrylate, or the like, a copolymer of these, or the like.
The shape of the external additive is also not limited, and may be any of a spherical shape, a flat shape, a plate shape, and a needle shape. The particle size of these external additives is preferably from 3 to 200 nm, and more preferably from 10 to 80 nm, from the viewpoint of imparting fluidity.
The surface of the metal oxide particles used as the external additive is preferably subjected to a hydrophobic treatment with a known surface treatment agent such as a coupling agent. The surface treatment agent includes, dimethyldimethoxysilane, hexamethyldisilazane (HMDS), methyltrimethoxysilane, isobutyltrimethoxysilane, decyltrimethoxysilane and the like.
In addition, silicone oil can also be used as the surface treating agent. Specific examples of the silicone oil include, for example, cyclic compounds and linear or branched organosiloxanes. More specifically, for example, organosiloxane oligomer, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, tetramethylcyclotetrasiloxane, tetravinyltetramethylcyclotetrasiloxane and the like can be mentioned. In addition, a highly reactive silicone oil in which a modifying group is introduced into a side chain, one end, both ends, one end of a side chain, both ends of a side chain, or the like and at least the end is modified may be used. Examples of the modifying group include, but are not particularly limited to, an alkoxy group, a carboxyl group, a carbinol group, a higher fatty acid-modified group, a phenol group, an epoxy group, a methacryl group, and an amino group. In addition, for example, silicone oil having several kinds of modified groups such as amino/alkoxy modification may be used. Furthermore, dimethyl silicone oil and the above-described modified silicone oil, and furthermore, other surface treating agents may be mixed or used in combination. Examples of the treatment agent to be used in combination include a silane coupling agent, a titanate-based coupling agent, an aluminate-based coupling agent, various silicone oils, a fatty acid, a fatty acid metal salt, an esterified product thereof, a rosin acid, and the like.
The lubricant can also be used as the external additive to further improve the cleaning performance and the transferability. Examples of the lubricant include metal salts of higher fatty acids as follows. Examples of the metal salt of a higher fatty acid include salts of stearic acid with zinc, aluminum, copper, magnesium, calcium or the like, and salts of oleic acid with zinc, manganese, iron, copper, magnesium or the like. In addition, examples of the metal salts of higher fatty acids include salts of palmitic acid with zinc, copper, magnesium, calcium, or the like; salts of linoleic acid with zinc, calcium, or the like; and salts of ricinoleic acid with zinc, calcium, or the like. The total amount of these external additives to be added is preferably 0.1 to 10 parts by mass, and more preferably 1 to 5 parts by mass, relative to 100 parts by mass of the toner base particles.

The method for producing the toner is not particularly limited, and the toner can be produced by, for example, a pulverization method, an emulsion dispersion method, a suspension polymerization method, a dispersion polymerization method, an emulsion polymerization method, or an emulsion polymerization aggregation method. Among these, the pulverization method is more preferable. Toner base particles produced by a pulverization method are excellent in dispersing a plurality of materials such as a charge control agent, a pigment, and a crystalline polyester. In particular, since the mono-component development contains a charge control agent, the pulverization method is preferred.
According to the pulverization method, the toner base particles can be obtained through a step of pulverizing a resin composition obtained by melting and kneading the binding resin and the colorant, followed by cooling. Furthermore, after the pulverization treatment, classification treatment or drying treatment may be performed as necessary. Hereinafter, a method for producing a toner by the pulverization method will be described.

(Mixing, Melting, and Kneading)

First, the materials forming the toner base particles are mixed. The mixing can be performed by a mixing apparatus such as a double-cone mixer, a V-type mixer, a drum-type mixer, a super mixer, a Henschel mixer, a Nauta mixer, or a mechanohybrid. Examples of the material constituting the toner base particles include the binding resin, the wax as the release agent, and other materials (for example, a colorant) which are arbitrarily added. Note that when the wax as the release agent contains the saturated hydrocarbon compound having 16 to 35 carbon atoms, it is preferable to use the wax in which the content is known. Alternatively, a predetermined amount of the saturated hydrocarbon compound having 16 to 35 carbon atoms may be added to the materials forming the toner base particles such that the content of the saturated hydrocarbon compound having 16 to 35 carbon atoms in the toner falls within a specific numerical range. In this case, it is preferable that the wax as the release agent does not contain the saturated hydrocarbon compound having 16 to 35 carbon atoms, or when the wax contains the saturated hydrocarbon compound having 16 to 35 carbon atoms, the content of the saturated hydrocarbon compound is known.
Next, the mixed materials are melted and kneaded. For the melting-kneading, a batch kneader such as a pressure kneader and a Banbury mixer, or a continuous kneader can be used. In continuous production, a single-screw extruder or a twin-screw extruder is preferably used. Examples of the twin-screw extruder include a KTK-type twin-screw extruder (manufactured by Kobe Steel, Ltd), a TEM-type twin-screw extruder (manufactured by Toshiba Machine Co., Ltd), a PCM kneader (manufactured by Ikegai Corporation), a twin-screw extruder (manufactured by K.C. K.K), a co-kneader (manufactured by Buss), and a Kneadex (manufactured by Nippon Coke & Engineering Co., Ltd). The temperature of the melt-kneading is preferably about 100 to 200°C. The resin composition obtained by melting-kneading is rolled with a two roll mill or the like, and rapidly cooled with water or the like to form a solid.

(Pulverization)

The obtained resin composition is pulverized to a desired particle size. The pulverization may be performed by, for example, performing coarse pulverization with a pulverizer such as a crusher, a hammer mill, or a feather mill, and then performing fine pulverization with a pulverizer or a pulverizer using an air jet method. As the pulverizer, for example, a pulverizer such as Kryptron System (manufactured by Kawasaki Heavy Industries, Ltd), Super Rotor (manufactured by Nisshin Engineering Inc), or Turbo Mill (manufactured by Freund - Turbo Corporation) can be used.

(Classification)

Thereafter, if necessary, particles of the pulverized resin composition are classified. The classification can be performed using a classifier or a sieving machine such as an inertia classification system Elbow Jet (manufactured by Nittetsu Mining Co., Ltd), a centrifugal force classification system Turboplex (manufactured by Hosokawa Micron Corporation), a TSP separator (manufactured by Hosokawa Micron Corporation), or Faculty (manufactured by Hosokawa Micron Corporation).

(Drying)

Furthermore, if necessary, the resin composition after the classification may be dried. The drying method is not particularly limited, and examples thereof include methods using an oven, a spray dryer, a vacuum freeze dryer, a reduced pressure dryer, a stationary shelf dryer, a movable shelf dryer, a fluidized bed dryer, a rotary dryer, and a stirring dryer. In this way, the toner base particles can be produced by the pulverization method.

(Addition of External Additive)

The obtained toner base particles are subjected to an external addition process with an external additive. The external addition process can be performed by blending predetermined amounts of the toner base particles and the external additive, and stirring and mixing them with a mixing device.
Examples of the mixing apparatus include a double cone mixer, a V-type mixer, a drum-type mixer, a super mixer, a Henschel mixer, a Nauta mixer, Mechano Hybrid (manufactured by Nippon Coke & Engineering Co., Ltd.), and Nobilta (manufactured by Hosokawa Micron Corporation).

[4. Image Forming Method and Image Forming Apparatus]

Hereinafter, an image forming apparatus that can be used in the image forming method of the present embodiment will be described. An example of the image forming apparatus includes an image forming apparatus used for a general electrophotographic image forming method. An example of the image forming apparatus includes an image forming apparatus including a photoreceptor that is an electrostatic latent image bearing member, a charger, an exposer, a developer, a transferer, and a fixer. The charger is for providing a uniform potential to the surface of the photoreceptor by corona discharge or discharge by a roller or a brush, having the same polarity as the toner. The exposer is for forming the electrostatic latent image by performing image exposure on the uniformly charged surface of the photoreceptor based on image data. The developer is for conveying the toner to the surface of the photoreceptor and visualizing the electrostatic latent image to form the toner image. The transferer is for transferring the toner image formed by the developer onto a transfer material via an intermediate transfer member as necessary. The fixer is for fixing the toner image on the transfer material. Such an image forming apparatus includes, for example, an image forming apparatus as illustrated in FIG. 1. FIG. 1 is a diagram schematically illustrating a configuration example of the image forming apparatus used in the image forming method. FIG. 1 is an explanatory sectional view showing an example of a configuration of a full-color image forming apparatus using the toner as a non-magnetic mono-component developer.
In the image forming apparatus illustrated in FIG. 1, around a photosensitive drum 10 that is rotationally driven, a charging brush 111 that is a charger for uniformly charging a surface of the photoconductor drum 10 to a predetermined potential is provided. Around the photosensitive drum 10, a cleaner 112 is provided to remove the toner remaining on the photosensitive drum 10.
Furthermore, a laser scanning optical system 20 is provided as the exposer for scanning and exposing the photosensitive drum 10 charged by the charging brush 111 with a laser beam. The laser scanning optical system 20 is a well-known system including a laser diode, a polygon mirror, and an f θ optical element, and print data for each of yellow, magenta, cyan, and black is transferred from a host computer to a controller of the laser scanning optical system 20. The laser scanning optical system 20 sequentially outputs a laser beam based on the print data for each color to scan and expose the photosensitive drum 10, thereby sequentially forming the electrostatic latent image for each color on the photosensitive drum 10.
Further, a full-color developing cartridge 30 is provided as the developer for performing full-color development by supplying toners of respective colors to the photosensitive drum 10 on which the electrostatic latent image is formed. In the full-color developing cartridge 30, developing cartridges 31Y, 31M, 31C, and 31Bk for four colors, which store non-magnetic mono-component toners of yellow, magenta, cyan, and black, respectively, are provided around a support shaft 33. The full-color developing cartridge 30 rotates around the support shaft 33 so that each of the developing cartridges 31Y, 31M, 31C, and 31Bk is guided to a position facing the photosensitive drum 10.
Further, in each of the developing cartridges 31Y, 31M, 31C and 31Bk in the full-color developing cartridge 30, for example, as shown in FIG. 2, a toner restricting member (for example, a restricting blade) is press-contacted (contacted) to an outer peripheral surface of a developer carrying member (developing roller) 25 for conveying the toner by rotation. The toner restricting member regulates the amount of the toner conveyed by the developing roller 25 and charges the conveyed toner. For example, in the image forming method of the present embodiment, the toner is preferably charged on the surface of the developing roller by using the restricting blade.
The full-color developing cartridge 30 is configured to rotate around the support shaft 33 as described above every time the electrostatic latent image in each color is formed on the photosensitive drum 10 by the laser scanning optical system 20 as described above. As a result, the developing cartridges 31Y, 31M, 31C and 31Bk in which the toners of the corresponding colors are accommodated can be sequentially guided to the position opposed to the photosensitive drum 10. Then, the developing rollers 25 in the respective developing cartridges 31Y, 31M, 31C, 31Bk are brought into contact with the photosensitive drum 10 or are not brought into contact with the photosensitive drum 10, and the charged toners of the respective colors are sequentially supplied onto the photosensitive drum 10 on which the electrostatic latent images of the respective colors are sequentially formed as described above to perform the developing.
Further, an endless intermediate transfer belt 40 which is rotationally driven is provided as the intermediate transfer member at a position downstream of the full-color developing cartridge 30 in the rotational direction of the photosensitive drum 10. The intermediate transfer belt 40 is driven to rotate in synchronization with the photosensitive drum 10. The intermediate transfer belt 40 is pressed by a rotatable primary transfer roller 41 so as to contact the photosensitive drum 10. Further, a secondary transfer roller 43 is rotatably provided at a portion of the support roller 42 supporting the intermediate transfer belt 40, and a transfer material S such as a recording sheet is pressed against the intermediate transfer belt 40 by the secondary transfer roller 43.
Further, in a space between the full-color developing cartridge 30 and the intermediate transfer belt 40, a cleaner 50 for scraping off the toner remaining on the intermediate transfer belt 40 is provided so as to be contactable to and separable from the intermediate transfer belt 40.
Further, a sheet feeder 60 for guiding the transfer material S to the intermediate transfer belt 40 is constituted by a sheet feed tray 61 for accommodating the transfer material S, a sheet feed roller 62 and a timing roller 63. The sheet feed roller 62 is for feeding the transfer materials S contained in the sheet feed tray 61 one by one. The timing roller 63 is for sending the transfer material S fed in synchronization with the image formed on the intermediate transfer belt 40 to between the intermediate transfer belt 40 and the secondary transfer roller 43. The transfer material S fed between the intermediate transfer belt 40 and the secondary transfer roller 43 is pressed against the intermediate transfer belt 40 by the secondary transfer roller 43, so that the toner image is pressed and transferred from the intermediate transfer belt 40 onto the transfer material S.
On the other hand, the transfer material S onto which the toner images have been pressed and transferred as described above is guided to fixer 70 by conveyor 66 formed of an air suction belt or the like. In the fixer 70, the transferred toner image is fixed on the transfer material S, and then the transfer material S is ejected onto the upper surface of the apparatus main body 100 through a vertical conveyance path 80.
Next, an operation of forming a full-color image using the full-color image forming apparatus will be specifically described.
First, the photosensitive drum 10 and the intermediate transfer belt 40 are rotationally driven at the same circumferential speed in their respective directions, and the photosensitive drum 10 is charged to a predetermined potential by the charging brush 111.
Next, the photosensitive drum 10 charged in this way is exposed to a yellow image by the laser scanning optical system 20, and the electrostatic latent image of the yellow image is formed on the photosensitive drum 10. Thereafter, the yellow toner charged by a toner restricting member is supplied from the developing cartridge 31Y containing the yellow toner to the photosensitive drum 10, thereby developing the yellow image. Then, the intermediate transfer belt 40 is pressed by the primary transfer roller 41 against the photosensitive drum 10 on which the yellow toner image is thus formed, and the yellow toner image formed on the photosensitive drum 10 is primarily transferred onto the intermediate transfer belt 40.
After the yellow toner image is transferred to the intermediate transfer belt 40 in this way, the full-color developing cartridge 30 is rotated about the support shaft 33, and the developing cartridge 31M containing the magenta toner is guided to a position facing the photosensitive drum 10. Then, as in the case of the yellow image, a magenta image is exposed to the charged photosensitive drum 10 by the laser scanning optical system 20 to form the electrostatic latent image, and the electrostatic latent image is developed by the developing cartridge 31M in which the magenta toner is accommodated. Then, the developed magenta toner image is primarily transferred from the photosensitive drum 10 to the intermediate transfer belt 40. Thereafter, in a similar manner, exposure, development, and primary transfer of a cyan image and a black image are further sequentially performed, and the yellow, magenta, cyan, and black toner images are sequentially superimposed on the intermediate transfer belt 40 to form a full color toner image.
Next, when the final black toner image is primarily transferred onto the intermediate transfer belt 40, the transfer material S is fed between the secondary transfer roller 43 and the intermediate transfer belt 40 by the timing roller 63, and the transfer material S is pressed against the intermediate transfer belt 40 by the secondary transfer roller 43. In this way, the full-color toner image formed on the intermediate transfer belt 40 is secondarily transferred onto the transfer material S.
Then, after the full-color toner image is thus secondarily transferred onto the transfer material S, the transfer material S is guided to the fixer 70 by the above-described conveyor 66, and the full-color toner image transferred by the fixer 70 is fixed onto the transfer material S. Thereafter, the transfer material S is discharged onto the upper surface of the apparatus main body 100 through the vertical conveyance path 80.
Here, FIG. 2 is an explanatory cross-sectional view illustrating an example of a configuration of the developing cartridge of the mono-component developer. The developing cartridge 31 shown in FIG. 2 includes at least the developing roller 25 and a restricting blade 28, and is used as the developing device for a non-magnetic mono-component toner.
The developing cartridge 31 includes a buffer chamber 26 adjacent to the developing roller 25 and a hopper 27 adjacent to the buffer chamber 26.
In the buffer chamber 26, the restricting blade 28 which is the toner restricting member is disposed in a state of being press-contacted (contacted) to the developing roller 25. The restricting blade 28 regulates the charge amount and the adhesion amount (conveyance amount) of the toner on the developing roller 25. Further, on a downstream side of the restricting blade 28 with respect to the rotational direction of the developing roller 25, an auxiliary blade 29 for assisting the regulation of the toner charge amount and the toner adhesion amount on the developing roller 25 may also be provided.
A supply roller 34 is pressed against the developing roller 25. The supply roller 34 is rotationally driven by a motor (not illustrated) in the same direction (the counterclockwise direction in the drawing) as the developing roller 25. The supply roller 34 includes a conductive cylindrical substrate and a foamed layer formed of urethane foam or the like on an outer periphery of the substrate.
The hopper 27 contains a toner T which is a non-magnetic mono-component developer. Furthermore, the hopper 27 is provided with a rotating body 35 that stirs the toner T. A film-like conveyance wing is attached to the rotating body 35, and the toner T is conveyed by rotation of the rotating body 35 in a direction indicated by an arrow. The toner T conveyed by the conveyance wing is supplied to the buffer chamber 26 via a passage 32 provided in a partition wall that separates the hopper 27 from the buffer chamber 26. Note that the shape of the conveyance wing is such that, with the rotation of the rotating body 31, the conveyance wing is bent while conveying the toner T in front of the rotation direction of the wing, and the conveyance wing returns to a straight state when the conveyance wing reaches the left end portion of the passage 32. In this way, the wing supplies the toner T to the passage 32 by returning to the straight state after the curved state.
The passage 32 is provided with a valve 321 for closing the passage 32. The valve 321 is a film-shaped member, and one end thereof is fixed to the upper side of the right side surface of the passage 32 of the partition wall. When the toner T is supplied from the hopper 27 to the passage 28, the valve 321 is pushed to the right by a pressing force from the toner T to open the passage 32. As a result, the toner T is supplied into the buffer chamber 26.
In the developing cartridge 31, at the time of image formation, the developing roller 25 is rotationally driven in the arrow direction, and the toner in the buffer chamber 26 is supplied onto the developing roller 25 by the rotation of the supply roller 34. The toner T supplied onto the developing roller 25 is charged and formed into a thin layer by the restricting blade 28 and the auxiliary blade 29, and then conveyed to a region opposed to the image bearing member to be used for developing the electrostatic latent image on the image bearing member. The toner that has not been used for development is neutralized by a static eliminating blade 24 with the rotation of the developing roller 25. After the electrostatic adhesive force between the developing roller 25 and the toner is reduced, the toner is scraped off and collected from the developing roller 25 by the supply roller 34.
The restricting blade 28 illustrated in FIG. 3 is provided in the developing cartridge 31 for the purpose of uniformly thinning the toner on the surface of the developing roller 25 and uniformly charging the toner.
As the restricting blade 28, it is possible to use phosphor bronze capable of uniformly thinning and charging the non-magnetic mono-component toner and having spring elasticity with which an average contact pressure to the developing roller can be controlled within a specified range. Phosphor bronze can impart more stable charging to nonmagnetic mono-component toner than other metal elastic materials (e.g., stainless steel). This is presumed to be because the triboelectric series of phosphor bronze is more positive than that of stainless steel, and therefore phosphor bronze can impart a more stable charge than stainless steel to the nonmagnetic mono-component toner.
Note that the restricting blade 28 is fixed by a holder, and is used by being attached to the developing cartridge 31 in a state of being fixed to the holder.

[Examples]

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited thereto. Note that in the following Examples, operations were performed at room temperature (25°C) unless otherwise specified. In addition, unless otherwise specified, "%," "ppm," and "part (s)" mean "% by mass," "ppm by mass," and "part (s) by mass," respectively.

[Preparation of Materials]

Saturated hydrocarbons having 20 carbon atoms, 26 carbon atoms, 30 carbon atoms, and 34 carbon atoms (manufactured by GL Sciences Inc) were fractionated in a mass ratio of 20:30:30:20, and were melt-mixed at 80°C. Thereafter, the melt-mixed saturated hydrocarbon was cooled and solidified to obtain a saturated hydrocarbon compound having 16 to 35 carbon atoms.

(Hydrocarbon Wax (Microcrystalline Wax))

A microcrystalline wax having a melting point of 82°C was prepared by solvent crystallization and filtration of a vacuum distillation residual oil. The microcrystalline wax was repeatedly subjected to molecular distillation until the average number of carbon atoms became 41 and components having 16 or more and 35 or less carbon atoms became undetectable, thereby obtaining a microcrystalline wax as the release agent. In the molecular distillation, low-molecular-weight components were removed at 240°C and at 0.2 Pa; and other components were removed at 400°C and 0.2 Pa. The number of carbon atoms was qualitatively determined by GC-MS and quantitatively determined by GC-FID. The obtained microcrystalline wax had the melting point of 73°C.

(Ester Wax (Behenic Acid Behenate))

Commercially available behenic acid behenate was used as the behenic acid behenate as the release agent.

<Toner>

(Synthesis of Amorphous Polyester A1)

• Terephthalic acid:	40.2 parts by mass
• Propylene oxide adduct of bisphenol A (BPA-PO):	29.0 parts by mass
• Dipropanol:	30.8 parts by mass
• Tin 2-ethylhexanoate (esterification catalyst):	0.5 parts by mass

The materials described above were weighed in a reaction tank equipped with a cooling tube, a stirrer, a nitrogen introduction tube, and a thermocouple. After replacing the inside of the reaction tank with nitrogen gas, the temperature was gradually raised while stirring, and the above materials were reacted over 3 hours while stirring at a temperature of 140°C.
Next, the pressure in the reaction tank was reduced to 8.0 kPa, the temperature was raised to 200°C while stirring, and the mixture was reacted for four hours.
Thereafter, the pressure in the reaction tank was reduced again to 5 kPa or less, and the mixture was reacted at 200°C for 3 hours to obtain an amorphous polyester resin A1. The amorphous polyester resin had a glass transition temperature of 52°C and a softening point of 110°C.

(Synthesis of Crystalline-Polyester-Resin B1)

• Adipic acid:	40.9 parts by mass
• 1,5- Pentanediol:	59.1 parts by mass
• Tin 2-ethylhexanoate:	0.50 parts by mass

The above-described materials were charged into a reaction tank equipped with a cooling tube, a stirrer, a nitrogen introduction tube, and a thermocouple. Thereafter, the inside of the reaction tank was replaced with nitrogen gas, the temperature was gradually raised while stirring, and the above materials were reacted over three hours while stirring at a temperature of 140°C.
Next, the pressure in the reaction tank was reduced to 8.3 kPa, the temperature was raised to 200°C while stirring, and the mixture was reacted for one hour to obtain a crystalline polyester B1. The melting point of the crystalline polyester resin was 65°C.

(Production of Toner Base 1)

• Amorphous polyester resin A1:	88.2 parts by mass
• Crystalline polyester B1:	11.8 parts by mass
• Hydrocarbon wax:	5.0 parts by mass
• Saturated hydrocarbon compounds having 16 to 35 carbon atoms:	0.05 parts by mass
• Charge control agent (metallic salicylate complex):	1.0 parts by mass
• Colorant:	12 parts by mass

Note that the following pigments were used as the colorants. The yellow toner was prepared using a yellow pigment (Pigment Yellow 74). The magenta toner was prepared using a magenta pigment (quinacridone). The cyan toner was prepared using a cyan pigment (phthalocyanine blue (C. I. Pigment Blue 15:3)). The black toner was prepared using a black pigment (carbon black).
The above materials were mixed in a Henschel mixer at a speed of 40 m·s^-1 for a rotation time of 5 min. Thereafter, the mixture was kneaded with a twin-screw kneader set at a temperature of 130°C. The obtained kneaded product was cooled and coarsely pulverized to 1 mm or less with a hammermill to obtain a coarsely pulverized product. The obtained coarsely pulverized product was finely pulverized with a mechanical pulverizer. Thereafter, the finely pulverized precursor was classified using an air classifier, thereby obtaining particles having a volume-based median diameter of 6.4 µm.
The classified particles were dried with an airflow drying apparatus. Toner particles 1 were obtained by setting the operation conditions to a hot air temperature of 130°C and a drying time of 30 minutes. The toner had a circularity of 0.96.

(Production of Toner Bases 2 to 9)

Toner bases 2 to 9 were prepared in the same manner as the toner base 1 except that the amount of the saturated hydrocarbon compound having 16 to 35 carbon atoms was changed as illustrated in Table 1 in the production of the toner base 1.

(Production of Toner Bases 10 to 14)

Toner bases 10 to 14 were prepared in the same manner as the toner base 1 except that the temperature and time of the drying process were changed to achieve the circularity as indicated in Table 1 in the production of toner base 1.

(Production of Toner Base 15)

Toner base 15 was prepared as in the production of toner base 1, except that the hydrocarbon wax was changed to an ester wax as illustrated in Table 1.

(Production of Toner Base 16)

Toner Base 16 was prepared in the same manner as the toner base 1 except that the hydrocarbon wax was changed to 3.5 parts by mass of a hydrocarbon wax and 1.5 parts by mass of an ester wax as shown in Table 1.

(Production of Toner Bases 17 to 23)

Toner bases 17 to 23 were prepared in the same manner as the toner base 1 except that the amount of crystalline polyester was changed as illustrated in Table 1 in the production of the toner base 1.

(Synthesis of Amorphous Polyester Resin A2 Having Vinyl Resin Segment)

A mixed solution of a monomer of the following vinyl resin, a monomer having a substituent reactive with both the amorphous polyester resin and the vinyl resin, and a polymerization initiator was placed in a dropping funnel.

• Styrene: 80.0 parts by mass

• N-butyl acrylate: 20.0 parts by mass

• Acrylic acid: 10.0 parts by mass

• Di-t-butyl peroxide (polymerization initiator): 16.0 parts by mass

The following monomers of the amorphous polyester resin were placed in a four necked flask equipped with a nitrogen introduction tube, a dehydration tube, a stirrer, and a thermocouple, and were heated to 170°C to be dissolved.

• Bisphenol -A ethylene oxide-2 mol adduct:	59.1 parts by mass
• Bisphenol A-propylene oxide 2 mol adduct:	281.7 parts by mass
• Terephthalic acid:	63.9 parts by mass
• Succinate:	48.4 parts by mass

The mixed liquid in the dropping funnel was added dropwise to the four necked flask over 90 minutes while being stirred, and was ripened for 60 minutes. After the ripening, the unreacted monomer was removed under reduced pressure (8 kPa). Thereafter, 0.4 part by mass of Ti (OBu) ₄ was charged, the temperature was raised to 235°C, and the reaction was carried out under ordinary pressure (101.3 kPa) for 5 hours and further under reduced pressure (8 kPa) for 1 hour.
Next, the mixture was cooled to 200°C and reacted under reduced pressure (20 kPa), and then the solvent was removed to obtain an amorphous polyester resin having a vinyl resin segment.
The glass transition point (Tg) of the obtained amorphous polyester resin was 60°C.

(Production of Toner Base 24)

Toner base 24 was prepared as in the toner 1, except that amorphous polyester A2 having a vinyl segment was used in place of amorphous polyester A1 as indicated in Table 1.

(Synthesis of Styrene-Acrylic Resin C1)

• Styrene:	80.0 parts by mass
• Butyl acrylate:	20.0 parts by mass
• Di-tert-butyl peroxide (Perbutyl D, manufactured by NOF CORPORATION):	1.00 parts by mass

100 parts by mass of propylene glycol monomethyl ether was heated while being replaced with nitrogen and refluxed at a liquid temperature of 120°C or higher, and the mixture of the above materials was added dropwise thereto over 3 hours. After completion of the dropwise addition, the mixture was stirred for 3 hours, then distilled under atmospheric pressure while raising the liquid temperature to 170°C, and after the liquid temperature reached 170°C, distilled under reduced pressure in a 1 hPa for 1 hour to remove the solvents, thereby obtaining a resinous solid. The resin solid was dissolved in tetrahydrofuran and reprecipitated with n-hexane, and the precipitated solid was collected by filtration to obtain a styrene-acrylic resin C1.

(Production of Toner Base 25)

Toner base 25 was prepared in the same manner as the toner 1 except that, in the production of toner base 1, the amorphous polyester resin A1 was changed to the styrene-acrylic resin C1 as illustrated in Table 1.

(Production of Toner Base 26)

Toner base 26 was prepared as in the toner 1, except that in the production of toner base 1, as illustrated in Table 1, the amount of amorphous polyester resin A1 was changed to 80 parts by mass and the amount of styrene-acrylic resin C1 was changed to 8.2 parts by mass in place of the amorphous polyester resin A1.

(Production of Toner 1)

The following external additive A, external additive B, and external additive C were added to 100 parts by mass of the particles of the toner base 1, and mixed for 1 minute with a Henschel mixer at a circumferential speed of 35 m/s. Thereafter, the Henschel mixer was stopped, and mixing was further performed for 5 minutes. The resultant was sieved using a mesh having an opening of 43 µm to obtain the toner particles 1.

• External additive A (R972 (manufactured by Nippon Aerosil Co., Ltd)):	1.0 parts by mass
• External additive B (X24 9600A (Shin -Etsu Chemical Co., Ltd)):	1.5 parts by mass
• External additive C (EPOSTAR S (Nippon Shokubai Co., Ltd)):	0.4 parts by mass

(Production of Toners 2 to 14 and 25 to 36)

Toners 2 to 14 and 25 to 36 were prepared in the same manner as the toner 1 except that the toner base material was changed as illustrated in Table 1 in the production of the toner 1.
The column of "binding resin" in "Toner Base" in Table 1 shows the type of resin used as the binding resin. Provided that whether or not the crystalline polyester B1 is used is indicated in the "crystalline Pes" under the "toner base" in Table 1, and the column entitled "binding resins" indicates the types of resins other than the crystalline polyester B1 among the resins used as the binding resins. Here, "Pes" in the column "binding resins" indicates that the amorphous polyester resin A1 was used as the binding resin. Similarly, hereinafter, in the aforementioned field, "vinyl Pes" indicates that the amorphous polyester resin A2 having a vinyl resin segment was used as the binding resin. "Pes/StAc" indicates that the amorphous polyester resin A1 and the styrene-acrylic resin C1 were used as the binding resins.
"StAc" indicates that the styrene-acrylic resin C1 was used as the binding resin. In addition, "yes" is given in the column of "crystalline Pes" described above in a case where the crystalline polyester B1 is used as the binding resin. On the other hand, in a case where the crystalline polyester B1 was not used as the binding resin, it is described as "no" in the column of the above-described "crystalline Pes".

(Production of Toners 15 to 24)

Toners 15 to 24 were prepared in the same manner as the toner 1, except that the number of parts of the external additive B and the external additive C added was changed as illustrated in Table 1 in the production of the toner 1.

(Content Rate Of Saturated Hydrocarbon Compound Having 16 to 35 Carbon Atoms in Toner)

The toners 1 to 36 were measured for the content rate of the saturated hydrocarbon compound having 16 to 35 carbon atoms in the toner by the following method. First, the saturated hydrocarbon compound was separated from the toner using a solvent that dissolves the saturated hydrocarbon compound. Then, the saturated hydrocarbon compound separated in the solvent was qualitatively analyzed by gas chromatography mass spectrometry (GC-MS). In addition, the specific saturated hydrocarbon compound separated in the solvent was quantified by gas chromatography (GC-FID) of a hydrogen flame ion detection system using a hydrogen flame ionization detector (FID) as a detector. A specific method for qualitative and quantitative determination of the saturated hydrocarbon compounds was performed in accordance with the measurement method described in the present embodiment. The results are shown in the column "C16 to 35 hydrocarbons (ppm by mass)" in Table 1.

(Average Coverage of External Additives (Fine Particle A and Fine Particle B) on Toner)

For each of the toners 1 to 36, the average coverage (% by area) of the toner fine particles A and the average coverage (% by area) of the toner fine particles B were determined by the analysis of the image by the scanning electron microscope. Note that the fine particles A are fine particles having a particle size of 80 nm or more and less than 200 nm, as confirmed by observing the toner with the scanning electron microscope. The fine particles B have a particle size, which can be confirmed by observing the toner with the scanning electron microscope, of 200 nm or more and 500 nm or less. The measurement of the particle size of the particles constituting the external additive and the calculation of the average coverage (% by area) of the fine particles A and the fine particles B are performed by the method described in the image forming method of the present embodiment. The average coverage (% by area) of the fine particles A in the toner is shown in the column of "average coverage (% by area)" of "fine particles A" in Table 2. The average coverage (% by area) of the fine particles B in the toner is shown in the column of "average coverage (% by area)" of "fine particles A" in Table 2.

[Evaluation Method (Image Formation)]

As the image forming apparatus, commercially available printers "COREFIDO C844dnw" (manufactured by Oki Electric Co., Ltd) and "PLAVI Pro1040" (manufactured by Oki Electric Co., Ltd) were used, and printing for forming a solid image on the entire surface was performed on one sheet under the following conditions. The printer was set so that the yellow toner was 4.0 g and the cyan toner was 4.0 g in a normal-temperature, normal-humidity environment (temperature of 20°C and relative humidity of 50%). Then, as a test image, printing for forming an entire solid image in which each solid image of yellow single color (Y), cyan single color (C), and green (G) was printed was performed on one sheet.
The recording medium used in printing to form the image is as follows.

Long sheet 1: 297 × 900 mm high-quality paper (manufactured by Nakagawa Seisakusho Co., Ltd., basis weight 128 g·m²)
Long sheet 2: 297 × 1200 mm high-quality paper (manufactured by Nakagawa Seisakusho Co. Ltd. basis weight: 128 g·m²)
Roll sheet: npi high-quality paper (manufactured by Nippon Paper Industries Co., Ltd., basis weight 127.9 g·m²)

(Evaluation of Image Density Difference Between Leading End and Trailing End)

The output (printed) test images were measured with "Spectrolina/Scan Bundle (manufactured by Gretag Macbeth)". Note that the measurement was performed under the following conditions.

light source: D50 light source
Field of View: 2 °
Concentration: ANSI T
White reference: Abs
filter: UV Cut
Measurement Mode: reflectance
Language: Japanese

In the measurement, a difference in image density (ID) between a solid image of the cyan single color (C) provided at the leading end portion of the image and the same image provided at the trailing end portion of the image was calculated. Then, the image density difference between the leading end and the trailing end was evaluated according to the following evaluation criteria. In the following evaluation criteria, evaluation A indicates that the image density difference between the leading end and the trailing end is the smallest and is good. The image density difference between the leading end and the trailing end increases in the order of evaluation B, evaluation C, and evaluation D. In the evaluation of the image density difference between the leading end and the trailing end, evaluations A to C were regarded as passing.

-Evaluation Criteria-

A: The image density difference is 0 to 0.03.
B: The image density difference is 0.04 to 0.10.
C: The image density difference is 0.11 to 0.20.
D: The image density difference is 0.21 or more.

(Evaluation of Occurrence of Transfer Failure)

The presence or absence of occurrence of transfer failure of the output (printed) test image was visually confirmed, and the occurrence of transfer failure was evaluated according to the following evaluation criteria. Note that the presence or absence of the occurrence of transfer failure was evaluated by checking discharge noise and insufficient transfer of green and yellow, and the case where no transfer failure occurred was regarded as good and evaluated as A. On the other hand, when generation of discharge noise was confirmed, L * a* b* was measured with a spectrophotometer "Spectrolina/Scan Bundle (manufactured by Gretag Macbeth)". Then, the color difference (Δ Eab) between the leading end and the trailing end was calculated and evaluated according to the following evaluation criteria. In the evaluation of the occurrence of transfer failure, evaluations A and B were regarded as passed.

-Evaluation Criteria-

A: No transfer failure occurs, and the transfer is satisfactory.
B: The color difference (Δ Eab) between the leading end and the trailing end is 5 or less.
C: The color difference (Δ Eab) between the leading end and the trailing end is more than 5.

(Evaluation of Filming)

Printing for forming a cyan single color (C) entirely solid image as a test image was performed, and the presence or absence of the occurrence of toner filming on the photoreceptor was visually confirmed. The filming was visually confirmed until the number of continuously printed sheets reached 50, and the filming was evaluated according to the following evaluation criteria. In the evaluation of filming, evaluations A and B were regarded as passing.

-Evaluation Criteria-

A: Even when the number of continuously printed sheets reached 50, no toner filming occurred, and good printing was performed.
B: There is no practical problem in a case where slight toner filming occurs until the number of continuously printed sheets reaches 50, but an image defect due to the toner filming does not occur.
C: An image defect occurred before the number of continuously printed sheets reached 50.

[Table 1]

TABLE I

	TONER No.	TONER BASE
	TONER No.	TONER BASE No.	BINDING RESIN	CRYSTALLINE Pes	*1	*2	WAX TYPE	CIRCULARITY
EXAMPLE 1	1	1	Pes	YES	10	400	HYDROCARBON	0.96
EXAMPLE 2	2	24	VINYL	YES	10	400	HYDROCARBON	0.96
EXAMPLE 3	3	26	Pes/StAc	YES	10	400	HYDROCARBON	0.96
EXAMPLE 4	4	2	Pes	YES	10	700	HYDROCARBON	0.96
EXAMPLE 5	5	3	Pes	YES	10	900	HYDROCARBON	0.96
EXAMPLE 6	6	4	Pes	YES	10	980	HYDROCARBON	0.96
EXAMPLE 7	7	5	Pes	YES	10	100	HYDROCARBON	0.96
EXAMPLE 8	8	6	Pes	YES	10	50	HYDROCARBON	0.96
EXAMPLE 9	9	7	Pes	YES	10	1	HYDROCARBON	0.96
EXAMPLE 10	10	10	Pes	YES	10	400	HYDROCARBON	0.951
EXAMPLE 11	11	11	Pes	YES	10	400	HYDROCARBON	0.945
EXAMPLE 12	12	12	Pes	YES	10	400	HYDROCARBON	0.98
EXAMPLE 13	13	13	Pes	YES	10	400	HYDROCARBON	0.989
EXAMPLE 14	14	14	Pes	YES	10	400	HYDROCARBON	0.991
EXAMPLE 15	15	1	Pes	YES	10	400	HYDROCARBON	0.96
EXAMPLE 16	16	1	Pes	YES	10	400	HYDROCARBON	0.96
EXAMPLE 17	17	1	Pes	YES	10	400	HYDROCARBON	0.96
EXAMPLE 18	18	1	Pes	YES	10	400	HYDROCARBON	0.96
EXAMPLE 19	19	1	Pes	YES	10	400	HYDROCARBON	0.96
EXAMPLE 20	20	1	Pes	YES	10	400	HYDROCARBON	0.96
EXAMPLE 21	21	1	Pes	YES	10	400	HYDROCARBON	0.96
EXAMPLE 22	22	1	Pes	YES	10	400	HYDROCARBON	0.96
EXAMPLE 23	23	1	Pes	YES	10	400	HYDROCARBON	0.96
EXAMPLE 24	24	1	Pes	YES	10	400	HYDROCARBON	0.96
EXAMPLE 25	25	15	Pes	YES	10	400	ESTER	0.96
EXAMPLE 26	26	16	Pes	YES	10	400	HYDROCARBON + ESTER	0.96
EXAMPLE 27	27	17	Pes	YES	1	400	HYDROCARBON	0.96
EXAMPLE 28	28	18	Pes	YES	2	400	HYDROCARBON	0.96
EXAMPLE 29	29	19	Pes	YES	5	400	HYDROCARBON	0.96
EXAMPLE 30	30	20	Pes	YES	14	400	HYDROCARBON	0.96
EXAMPLE 31	31	21	Pes	YES	18	400	HYDROCARBON	0.96
EXAMPLE 32	32	22	Pes	YES	21	400	HYDROCARBON	0.96
COMPARATIVE EXAMPLE 1	33	25	StAc	YES	10	400	HYDROCARBON	0.96
COMPARATIVE EXAMPLE 2	34	23	Pes	NO	-	400	HYDROCARBON	0.96
COMPARATIVE EXAMPLE 3	35	8	Pes	YES	10	1010	HYDROCARBON	0.96
COMPARATIVE EXAMPLE 4	36	9	Pes	YES	10	0.8	HYDROCARBON	0.96

*1: CRYSTALLINE Pes CONTENT (% BY MASS) *2: C16 TO 35 HYDROCARBONS (PPM BY MASS)

[Table 2]

TABLE II

	TONER No.	TONER BASE No.	EXTERNAL ADDITIVE
			EXTERNAL ADDITIVE B	EXTERNAL ADDITIVE C	FINE PARTICLE A	FINE PARTICLE B
			*1	*1	*2	*2
EXAMPLE 1	1	1	1.5	0.4	22	2
EXAMPLE 2	2	24	1.5	0.4	22	2
EXAMPLE 3	3	28	1.5	0.4	22	2
EXAMPLE 4	4	2	1.5	0.4	22	2
EXAMPLE 5	5	3	1.5	0.4	22	2
EXAMPLE 6	6	4	1.5	0.4	22	2
EXAMPLE 7	7	5	1.5	0.4	22	2
EXAMPLE 8	8	6	1.5	0.4	22	2
EXAMPLE 9	9	7	1.5	0.4	22	2
EXAMPLE 10	10	10	1.5	0.4	15	1.5
EXAMPLE 11	11	11	1.5	0.4	19	1.8
EXAMPLE 12	12	12	1.5	0.4	25	2.5
EXAMPLE 13	13	13	1.5	0.4	27	2.7
EXAMPLE 14	14	14	1.5	0.4	30	2.8
EXAMPLE 15	15	1	1.5	0.1	17	0.1
EXAMPLE 16	16	1	1.5	-	15	-
EXAMPLE 17	17	1	1.5	0.7	25	3.1
EXAMPLE 18	18	1	1.5	0.9	29	4.8
EXAMPLE 19	19	1	1.5	1	33	5.1
EXAMPLE 20	20	1	0.2	0.4	5.1	2
EXAMPLE 21	21	1	0.3	0.4	4.8	2
EXAMPLE 22	22	1	2	0.4	30	2
EXAMPLE 23	23	1	3.4	0.4	39	2
EXAMPLE 24	24	1	3.5	0.4	41	2
EXAMPLE 25	25	15	1.5	0.4	22	2
EXAMPLE 26	26	16	1.5	0.4	22	2
EXAMPLE 27	27	17	1.5	0.4	22	2
EXAMPLE 28	28	18	1.5	0.4	22	2
EXAMPLE 29	29	19	1.5	0.4	22	2
EXAMPLE 30	30	20	1.5	0.4	22	2
EXAMPLE 31	31	21	1.5	0.4	22	2
EXAMPLE 32	32	22	1.5	0.4	22	2
COMPARATIVE EXAMPLE 1	33	25	1.5	0.4	22	2
COMPARATIVE EXAMPLE 2	34	23	1.5	0.4	22	2
COMPARATIVE EXAMPLE 3	35	8	1.5	0.4	22	2
COMPARATIVE EXAMPLE 4	36	9	1.5	0.4	22	2

*1: NUMBER OF PARTS ADDED (PARTS BY MASS) *2: AVERAGE COVERAGE (AREA%)

[Table 3]

TABLE III

	TONER No.	EVALUATOR	EVALUATION
		DEVELOPING METHOD	IMAGE DENSITY DIFFERENCE BETWEEN LEADING END AND TRAILING END			OCCURRENCE OF TRANSFER FAILURE	FILMING
		DEVELOPING METHOD	LONG SHEET 1 LENGTH 900 mm	LONG SHEET 2 LENGTH 1300 mm	ROLL PAPER	OCCURRENCE OF TRANSFER FAILURE	FILMING
EXAMPLE 1	1	*1	B : 0.05	A: 0.03	A : 0.02	A	A
EXAMPLE 2	2	*1	A : 0.01	A : 0.01	A : 0.01	A	A
EXAMPLE 3	3	*1	B : 0.04	A : 0.03	A : 0.03	A	A
EXAMPLE 4	4	*1	B : 0.07	B : 0.06	B:0.06	A	A
EXAMPLE 5	5	*1	C : 0.13	C : 0.15	B : 0.10	A	B
EXAMPLE 6	6	*1	C : 0.19	C : 0.19	C : 0.20	B	B
EXAMPLE 7	7	*1	B : 0.07	B : 0.06	B : 0.04	A	A
EXAMPLE 8	8	*1	B : 0.09	B : 0.10	B : 0.10	A	A
EXAMPLE 9	9	*1	C : 0.16	C : 0.20	C : 0.20	B	A
EXAMPLE 10	10	*1	B : 0.10	B : 0.09	B : 0.08	A	A
EXAMPLE 11	11	*1	C : 0.20	C:0.19	C : 0.18	B	A
EXAMPLE 12	12	*1	B : 0.04	A: 0.03	A: 0.03	A	A
EXAMPLE 13	13	*1	C : 0.15	C : 0.12	B : 0.10	A	A
EXAMPLE 14	14	*1	C : 0.20	C : 0.19	B : 0.13	B	B
EXAMPLE 15	15	*1	B : 0.09	B : 0.10	B : 0.10	B	A
EXAMPLE 16	16	*1	C : 0.18	C : 0.20	C : 0.20	B	B
EXAMPLE 17	17	*1	B : 0.05	B : 0.04	B : 0.04	A	A
EXAMPLE 18	18	*1	C : 0.15	B : 0.10	B : 0.10	A	A
EXAMPLE 19	19	*1	C : 0.20	C : 0.19	C : 0.18	B	A
EXAMPLE 20	20	*1	B : 0.09	B : 0.10	B : 0.10	B	A
EXAMPLE 21	21	*1	C : 0.18	C : 0.20	C : 0.20	B	B
EXAMPLE 22	22	*1	B : 0.07	B : 0.06	B : 0.06	A	A
EXAMPLE 23	23	*1	C : 0.15	B : 0.10	B : 0.10	A	A
EXAMPLE 24	24	*1	C : 0.20	C : 0.19	C : 0.18	B	A
EXAMPLE 25	25	*1	B : 0.05	B : 0.04	B : 0.04	A	A
EXAMPLE 26	26	*1	B : 0.04	A: 0.03	A : 0.03	A	A
EXAMPLE 27	27	*1	C : 0.20	C : 0.19	C : 0.18	B	A
EXAMPLE 28	28	*1	C : 0.13	B : 0.07	B : 0.08	A	A
EXAMPLE 29	29	*1	B : 0.05	B : 0.04	B:0.04	A	A
EXAMPLE 30	30	*1	B : 0.05	B : 0.04	B : 0.04	A	A
EXAMPLE 31	31	*1	C:0.15	C : 0.11	B : 0.10	A	A
EXAMPLE 32	32	*1	C:0.19	C : 0.17	C : 0.16	B	B
COMPARATIVE EXAMPLE 1	33	*1	D : 0.21	D : 0.21	D : 0.25	C	A
COMPARATIVE EXAMPLE 2	34	*1	D : 0.22	D : 0.25	D : 0.28	C	A
COMPARATIVE EXAMPLE 3	35	*1	D : 0.25	D : 0.28	D : 0.28	C	C
COMPARATIVE EXAMPLE 4	36	*1	D : 0.26	D : 0.28	D : 0.28	C	A

*1 : NONMAGNETIC 1 COMPONENT

(Result)

The images formed in Examples 1 to 32 showed good results in all of the evaluations of the image density difference between the leading end and the trailing end, the occurrence of transfer failure, and the filming. On the other hand, in the images formed in Comparative Examples 1 to 4, the image density difference between the leading end and the trailing end was extremely large, and the evaluation of the occurrence of transfer failure was also failed. Furthermore, also in the evaluation of filming, the image formed in Comparative Example 3 had image failure until the number of sheets continuously printed reached 50.

(Effect)

According to the present invention, it is possible to form an image having excellent fixability to a recording medium which is long in a sheet conveyance direction such as the long sheet, stable transferability at the leading end and the trailing end, and uniform image density and gloss at the leading end and the trailing end.
Although the realization mechanism or action mechanism of the effect of the present invention is not clear, the inventors infer the mechanism as follows.
In order to stabilize the transferability of the toner image printed on the long sheet at the leading end portion and the trailing end portion, it is necessary to suppress an increase in the resistance of the toner image. As the binding resin contained in the toner, the crystalline resin is used in order to impart fixability to the toner. Such crystalline resin has lower resistance than other amorphous resins and therefore can serve as a conductive path in the toner image.
Incidentally, for example, the toner containing wax may be used in image formation by an electrophotographic method or the like. The wax is melted from the toner by heating during fixing and exudes to the surface of the sheet. For example, when a wax 220 is contained in a toner image 210 as illustrated in FIG. 3, the wax 220 in the toner image 210 may melt and exude to a surface 210A of the toner image 210 during fixing, as illustrated in FIG. 4. Here, FIG. 3 and FIG. 4 are schematic diagrams for illustrating the behavior of wax during fixing of the toner image formed by a conventional image forming method.
However, as illustrated in FIG. 4, the presence of the highly hydrophobic wax 220 on the surface 210A of the toner image 210 hinders the adsorption of moisture from the surface 210A into the toner image 210, making it difficult to reduce the resistance of the toner image 210.
Therefore, the present inventors incorporated a small amount of a short chain saturated hydrocarbon compound into the toner, and performed image formation using the toner. By performing image formation using such toner, at the time of fixing, first, as illustrated in FIG. 5, the short chain length saturated hydrocarbon compound 130 having a low melt viscosity are dissolved and exude to a surface 110A of the toner image 110. Thereafter, the wax 120 in the toner image 110 melts and seeps out onto the surface 110A of the toner image 110. However, as illustrated in FIG. 6, when the wax 120 exudes to the surface 110A of the toner image 110, it is localized in a region where the short chain length saturated hydrocarbon compounds 130 having close polarities are present. Therefore, it is possible to suppress the wax 120 from exuding to the surface 110A of the toner image 110. As a result, an increase in the resistance of the toner image 110 can be suppressed. Here, FIG. 5 and FIG. 6 are schematic diagrams for illustrating the behavior of the wax during fixing of the toner image formed by the image forming method of the present invention.
When a saturated hydrocarbon compound having 16 to 35 carbon atoms was used as the short chain length saturated hydrocarbon compound 130, the exudation of the wax 120 could be effectively suppressed and an increase in the resistance of the toner image 110 could be suppressed. For example, saturated hydrocarbon compounds having 16 or more carbon atoms are unlikely to exude to the surface 110A of the toner image 110 and are not sublimated by fixing heat, which is presumed to enable the above-described intended effects to be effectively exhibited. Furthermore, saturated hydrocarbon compounds having 35 or less carbon atoms have low viscosity and thus can be locally disposed on the surface 110A of the toner image 110 before the wax 120 melts. Furthermore, when the content rate of the saturated hydrocarbon compound having 16 to 35 carbon atoms in the toner is 1 to 1000 ppm by mass, the exudation of the wax 120 could be effectively suppressed, and the increase in the resistance of the toner image 110 could be suppressed. For example, it is presumed that when the content rate of the saturated hydrocarbon compound having 16 to 35 carbon atoms is 1 ppm by mass or more, a sufficient amount of the saturated hydrocarbon compound exists and the intended effect can be exhibited. It is presumed that when the content rate of the saturated hydrocarbon compound having 16 to 35 carbon atoms is 1000 ppm by mass or less, the wax 120 is appropriately and locally disposed, thus achieving the intended effect.
Although embodiments of the present invention have been described and shown in detail, the disclosed embodiments are made for purposes of illustration and example only and not limitation. The scope of the present invention should be interpreted by terms of the appended claims.

Claims

An image forming method that forms an image on at least a long sheet by using toner containing at least a binding resin, a wax and an external additive, the method comprising:
preparing the binding resin as a mixture of at least a crystalline polyester resin and an amorphous polyester resin, and preparing a content rate of a saturated hydrocarbon compound having 16 to 35 carbon atoms in the toner to be 1 to 1000 ppm by mass.
The image forming method according to claim 1, wherein a length of the long sheet is longer than or equal to 900 mm.
The image forming method according to claim 2, wherein the length of the long sheet is longer than or equal to 1300 mm.
The image forming method according to claim 1 or 2, wherein the wax includes at least a hydrocarbon wax.
The image forming method according to claim 1 or 2, wherein the content rate of the saturated hydrocarbon compound having 16 to 35 carbon atoms in the toner is 100 to 700 ppm by mass.
The image forming method according to claim 1 or 2, wherein the toner is charged on a surface of a developing roller using a restricting blade.
The image forming method according to claim 1 or 2, wherein the amorphous polyester resin includes the amorphous polyester resin having a vinyl resin segment containing at least a constitutional unit derived from a vinyl monomer.
The image forming method according to claim 1 or 2,
wherein the external additive includes at least a fine particle A that has a particle size of 80 nm or more and less than 200 nm which can be confirmed by observing the toner with a scanning electron microscope, and

wherein an average coverage of the fine particle A on the toner as determined by an analysis of the image of the toner by the scanning electron microscope is 5% by area or more and 40% by area or less.
The image forming method according to claim 1 or 2,
wherein the external additive includes at least a fine particle B that has a particle size of 200 nm or more and 500 nm or less which can be confirmed by observing the toner with a scanning electron microscope, and

wherein an average coverage of the fine particle B on the toner as determined by an analysis of the image of the toner by the scanning electron microscope is 0.1% by area or more and 5% by area or less.
The image forming method according to claim 1 or 2, wherein the toner has a circularity of 0.950 to 0.990.
The image forming method according to claim 1 or 2, wherein a content of the crystalline polyester resin in the toner is 2 to 20% by mass.