Image formation apparatus

Abstract

To provide an image formation apparatus capable of suppressing the occurrence of white streaks and uneven image density.SOLUTION: An image formation apparatus comprises: a non-magnetic single-component developer; an image carrier; and a development device which supplies the non-magnetic single-component developer to an electrostatic latent image formed on the surface of the image carrier to develop the electrostatic latent image. The development device includes: a development roller which carries the non-magnetic single-component developer; and a regulation member which regulates the thickness of a developer layer formed from the non-magnetic single-component developer. The non-magnetic single-component developer includes positively-charged toner which includes toner particles. The toner particles include toner base particles and external additive particles adhering to the surface of the toner base particles. The external additive particles include resin particles and silica particles. When ultrasonic processing that applies the ultrasonic vibration with the frequency of 28 kHz and the output of 100 W for 5 minutes is performed on the toner, the isolation rate of the resin particles is between 18 mass% and 42 mass%, and the isolation rate of the silica particles is between 5 mass% and 25 mass%.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] An image forming apparatus using an electrophotographic method is equipped with a developing device including, for example, a developing roller that carries a developer, and a regulating member that regulates the thickness of a developer layer (toner layer) made of the developer on the developing roller. The developer may be a one-component developer that contains only toner, or a two-component developer that contains toner and a carrier.

[0003] In addition, one-component developers include magnetic one-component developers in which the toner particles contain magnetic powder, and non-magnetic one-component developers in which the toner particles do not contain magnetic powder. In a method of developing with a non-magnetic one-component developer, a regulating member is provided in a developing device so as to abut against the surface of a developing roller. Hereinafter, a method of developing with a non-magnetic one-component developer using a developing device in which a regulating member is provided so as to abut against the surface of a developing roller may be referred to as a "non-magnetic one-component development method."

[0004] When forming an image using a non-magnetic one-component development method, a phenomenon may occur in which toner particles adhere to the regulating member. Also, when forming an image using a non-magnetic one-component development method, a phenomenon may occur in which external additive particles are detached from the toner particles and the detached external additive particles are retained at the contact portion between the regulating member and the developing roller. These phenomena may cause image defects (especially white streaks and uneven image density).

[0005] As a method for suppressing the phenomenon of toner particles sticking to a regulating member, for example, it has been proposed to use a toner containing resin particles and silica particles as external additive particles as a non-magnetic one-component developer (Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2009-180910 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, even with an image forming apparatus using the toner described in Patent Document 1 as a non-magnetic one-component developer, it is difficult to sufficiently prevent the occurrence of image defects (particularly white streaks and uneven image density).

[0008] The present invention has been made in view of the above-mentioned problems, and has an object to provide an image forming apparatus capable of suppressing the occurrence of white streaks and uneven image density. [Means for solving the problem]

[0009] The image forming apparatus according to the present invention includes a non-magnetic one-component developer, an image carrier, and a developing device that supplies the non-magnetic one-component developer to an electrostatic latent image formed on the surface of the image carrier to develop the electrostatic latent image. The developing device includes a developing roller that carries the non-magnetic one-component developer, and a regulating member that regulates the thickness of a developer layer composed of the non-magnetic one-component developer, and is configured to supply the non-magnetic one-component developer to the electrostatic latent image while forming the developer layer by the regulating member that is in contact with the developing roller. The non-magnetic one-component developer includes a positively charged toner that includes toner particles. The toner particles include toner base particles and external additive particles that are attached to the surfaces of the toner base particles. The external additive particles include resin particles and silica particles. When the toner is subjected to ultrasonic treatment in which ultrasonic vibrations with a frequency of 28 kHz and an output of 100 W are applied for 5 minutes, the liberation rate of the resin particles is 18% by mass or more and 42% by mass or less. The liberation rate of the silica particles is from 5% by mass to 25% by mass. Effect of the Invention

[0010] The image forming apparatus of this embodiment can suppress the occurrence of white streaks and uneven image density. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is a schematic cross-sectional view illustrating an example of a toner particle. [Diagram 2] FIG. 1 illustrates an example of a configuration of an image forming apparatus. [Diagram 3] 3 is a diagram showing a configuration of a developing device included in the image forming apparatus in FIG. 2. [Figure 4] 3 is a schematic cross-sectional view showing a configuration of a developing roller included in the image forming apparatus in FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] First, the meaning of the terms used in this specification and the measurement method will be explained. A toner is an aggregate (e.g., powder) of toner particles. An external additive is an aggregate (e.g., powder) of external additive particles. Unless otherwise specified, values ​​indicating the shape, physical properties, etc. of a powder (more specifically, a powder of toner particles, a powder of external additive particles, etc.) are the number averages of values ​​measured for each of a considerable number of particles selected from the powder. Unless otherwise specified, the "main component" of a material means the component that is contained most abundantly in the material on a mass basis. The compound name may be followed by "based" to collectively refer to the compound and its derivatives. Acrylic and methacrylic may be collectively referred to as "(meth)acrylic". Each component described in this specification may be used alone or in combination of two or more types. The expression "at least one of A and B" is synonymous with "A and / or B".

[0013] Volume median diameter of powder (D 50) is the median diameter measured using a laser diffraction / scattering type particle size distribution analyzer (LA-950 manufactured by Horiba, Ltd.). The number-average primary particle diameter is the number average value of the circle-equivalent diameter of primary particles (Heywood diameter: diameter of a circle having the same area as the projected area of ​​a primary particle) measured using a scanning electron microscope, unless otherwise specified. The number-average primary particle diameter is, for example, the number average value of the circle-equivalent diameter of 100 primary particles. The charge amount (unit: μC / g) is a value measured using a small suction-type charge amount measuring device (MODEL 212HS manufactured by Trek) under an environment of a temperature of 25° C. and a relative humidity of 50% RH, unless otherwise specified. The softening point (Tm) is a value measured using a high-temperature flow tester (for example, CFT-500D manufactured by Shimadzu Corporation). In the S-shaped curve (horizontal axis: temperature, vertical axis: stroke) measured by the Koka flow tester, the temperature at which "(baseline stroke value + maximum stroke value) / 2" is obtained corresponds to Tm (softening point). The meanings of the terms used in this specification and the measurement method have been explained above.

[0014] <Image forming device> An embodiment of the present invention relates to an image forming apparatus. The image forming apparatus of this embodiment includes a non-magnetic one-component developer, an image carrier, and a developing device that supplies the non-magnetic one-component developer to an electrostatic latent image formed on the surface of the image carrier to develop the electrostatic latent image. The developing device has a developing roller that carries the non-magnetic one-component developer, and a regulating member that regulates the thickness of a developer layer composed of the non-magnetic one-component developer, and is configured to supply the non-magnetic one-component developer to the electrostatic latent image while forming a developer layer by the regulating member abutted on the developing roller. The non-magnetic one-component developer includes a positively charged toner including toner particles. The toner particles include toner base particles and external additive particles attached to the surfaces of the toner base particles. The external additive particles include resin particles and silica particles. When ultrasonic treatment is performed on the toner by applying ultrasonic vibrations with a frequency of 28 kHz and an output of 100 W for 5 minutes, the liberation rate of the resin particles is 18% by mass or more and 42% by mass or less, and the liberation rate of the silica particles is 5% by mass or more and 25% by mass or less.

[0015] More specifically, in the measurement of the liberation rate of resin particles, a toner dispersion liquid containing 2 parts by mass of a nonionic surfactant (e.g., Triton (registered trademark)-X100), 98 parts by mass of water, and 2 parts by mass of toner is subjected to ultrasonic treatment by applying ultrasonic vibrations at a frequency of 28 kHz and an output of 100 W for 5 minutes. Next, the mass M of the resin particles contained in the toner particles before the ultrasonic treatment is measured. 1R The mass M of the resin particles detached from the toner base particles after ultrasonic treatment 2R Percentage of (100×M 2R / M 1R ) is calculated. Mass M 1R and mass M 2R can be measured, for example, by GC / MS analysis. Other detailed measurement conditions can be the methods described in the Examples or methods based thereon.

[0016] In measuring the liberation rate of silica particles, a toner dispersion liquid containing 2 parts by mass of a nonionic surfactant (e.g., Triton (registered trademark)-X100), 98 parts by mass of water, and 2 parts by mass of toner is subjected to ultrasonic treatment by applying ultrasonic vibrations at a frequency of 28 kHz and an output of 100 W for 5 minutes. Next, the mass M of silica particles contained in the toner particles before the ultrasonic treatment is measured. 1S The mass M of silica particles detached from the toner base particles after ultrasonic treatment 2S Percentage of (100×M 2S / M 1S ) is calculated. Mass M 1S and mass M 2S can be measured, for example, by fluorescent X-ray analysis using silicon atoms as a detection target. Other detailed measurement conditions can be determined by the method described in the Examples or a method based thereon.

[0017] The image forming apparatus of this embodiment is provided with the above-mentioned configuration, and thus can suppress the occurrence of white streaks and uneven image density. The reason for this is presumed to be as follows. The toner (non-magnetic one-component developer) provided in the image forming apparatus of this embodiment contains silica particles and resin particles as external additive particles. The silica particles impart excellent fluidity to the toner particles and also function to suppress the toner particles from adhering to other members (particularly, the regulating member). The resin particles also function as spacer particles that suppress the silica particles from sinking into the toner base particles. The external additive particles contain resin particles, and thus the function of the silica particles is effectively exerted. In the image forming apparatus of this embodiment, the liberation rates of the resin particles and the silica particles are optimized.

[0018] Specifically, by setting the liberation rate of the resin particles to 18% by mass or more, the resin particles can easily function as spacer particles, and the silica particles can be effectively prevented from sinking into the toner base particles. This allows the silica particles to more effectively function in preventing the toner particles from adhering to other members (particularly, the regulating member). Furthermore, by setting the liberation rate of the silica particles to 5% by mass or more, the toner fluidity can be sufficiently ensured. This allows the thickness of the developer layer formed on the developing roller to be stabilized. As a result, the image forming apparatus of this embodiment can prevent the occurrence of white streaks. Furthermore, by setting the liberation rate of the resin particles to 42% by mass or less, the resin particles can be prevented from detaching from the toner base particles. Furthermore, by setting the liberation rate of the silica particles to 25% by mass or less, the silica particles can be prevented from detaching from the toner base particles. This allows the occurrence of a phenomenon in which the resin particles and silica particles detached from the toner base particles remain at the contact portion between the regulating member and the developing roller to be suppressed. As a result, the image forming apparatus of this embodiment can prevent the occurrence of unevenness in image density. Hereinafter, the toner used in the image forming apparatus of this embodiment will be described in detail, and then the apparatus will be described in detail.

[0019] [Toner particles] The toner is a positively charged toner containing toner particles. An example of the toner particle will be described below with reference to FIG. 1. FIG. 1 shows a toner particle 1 which is an example of the toner particle. The toner particle 1 shown in FIG. 1 includes a toner base particle 2 and an external additive particle 3 attached to the surface of the toner base particle 2. The external additive particle 3 includes a resin particle 4 and a silica particle 5.

[0020] The toner particles have been described above with reference to FIG. 1. However, the toner particles may have a structure different from that of the toner particle 1 described in FIG. 1. For example, the toner particles may be toner particles having a shell layer (hereinafter, may be referred to as capsule toner particles). In the capsule toner particles, the toner mother particles have, for example, a toner core containing a binder resin, and a shell layer that covers at least a part of the surface of the toner core. In addition, the external additive particles may contain particles other than resin particles and silica particles. The toner particles have been described above in detail with reference to FIG. 1.

[0021] [External additive particles] The external additive particles are attached to the surfaces of the toner base particles. The external additive particles include resin particles and silica particles.

[0022] (Resin particles) Examples of the resin contained in the resin particles include (meth)acrylic resin, styrene-(meth)acrylic resin, polyester resin, polyurethane resin, and olefin resin (e.g., polyethylene resin and polypropylene resin). The resin contained in the resin particles is preferably crosslinked. The resin contained in the resin particles is preferably a styrene-(meth)acrylic resin, and more preferably a crosslinked styrene-(meth)acrylic resin. The content of the styrene-(meth)acrylic resin in the resin particles is preferably 70% by mass or more, more preferably 95% by mass or more, and even more preferably 100% by mass.

[0023] Styrene-(meth)acrylic resin is a copolymer of a styrene compound and a (meth)acrylic acid compound. Examples of the (meth)acrylic acid compound include (meth)acrylic acid, (meth)acrylonitrile, and (meth)acrylic acid alkyl esters (particularly, (meth)acrylic acid alkyl esters having an alkyl group having 1 to 4 carbon atoms in the ester moiety).

[0024] The styrene-(meth)acrylic resin preferably has a first repeating unit derived from a styrene compound and a second repeating unit derived from an alkyl (meth)acrylate ester.

[0025] Examples of the styrene compound include styrene, alkylstyrenes (more specifically, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, ethylstyrene, 2,3-dimethylstyrene, 2,4-dimethylstyrene, o-tert-butylstyrene, m-tert-butylstyrene, and p-tert-butylstyrene), and halogenated styrenes (more specifically, α-chlorostyrene, o-chlorostyrene, m-chlorostyrene, and p-chlorostyrene). As the styrene compound, styrene is preferred.

[0026] The content of the first repeating unit relative to all repeating units contained in the styrene-(meth)acrylic resin is preferably from 4.0% by mass to 25.0% by mass, and more preferably from 6.0% by mass to 14.0% by mass.

[0027] Examples of the (meth)acrylic acid alkyl ester include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, iso-propyl (meth)acrylate, butyl (meth)acrylate (specifically, n-butyl (meth)acrylate), iso-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. As the (meth)acrylic acid alkyl ester, butyl (meth)acrylate is preferred.

[0028] The content of the second repeating unit relative to all repeating units contained in the styrene-(meth)acrylic resin is preferably from 30.0% by mass to 95.0% by mass, and more preferably from 45.0% by mass to 60.0% by mass.

[0029] When the styrene-(meth)acrylic resin is crosslinked, the styrene-(meth)acrylic resin further has a third repeating unit derived from a crosslinking agent. The inclusion of the crosslinked styrene-(meth)acrylic resin in the resin particles provides the resin particles with appropriate rigidity, making it easier for the resin particles to function as spacer particles.

[0030] Examples of the crosslinking agent include compounds having two or more vinyl groups.Specific examples of the crosslinking agent include N,N'-methylenebisacrylamide, divinylbenzene, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, 1,4-butanediol dimethacrylate, and 1,6-hexanediol dimethacrylate.As the crosslinking agent, divinylbenzene is preferable.

[0031] The content ratio of the third repeating unit relative to the total repeating units of the styrene-(meth)acrylic resin is preferably 20.0% by mass or more and 45.0% by mass or less, more preferably 32.0% by mass or more and 40.0% by mass or less. By making the content ratio of the third repeating unit 20.0% by mass or more, the rigidity of the resin particles is optimized, and the resin particles can more easily function as spacer particles. By making the content ratio of the third repeating unit 45.0% by mass or less, the hardness of the resin particles becomes excessively high, and the surface of the photoreceptor can be prevented from being polished.

[0032] The styrene-(meth)acrylic resin is preferably a resin having the repeating units of the following combination 1 or 2. In combination 1 or 2, the numerical range shown in parentheses after the repeating unit indicates the preferred content ratio of that repeating unit to all repeating units. Combination 1: Repeating units derived from styrene (e.g., 8.0% by mass or more and 13.0% by mass or less), repeating units derived from n-butyl methacrylate (e.g., 50.0% by mass or more and 55.0% by mass or less), and repeating units derived from divinylbenzene (e.g., 34.0% by mass or more and 40.0% by mass or less) Combination 2: Repeating units derived from styrene (e.g., 8.0% by mass or more and 12.0% by mass or less) and repeating units derived from methyl methacrylate (e.g., 88.0% by mass or more and 92.0% by mass or less)

[0033] The liberation rate of the resin particles is 18% by mass or more and 42% by mass or less, and preferably 25% by mass or more and 35% by mass or less. By making the liberation rate of the resin particles 18% by mass or more, the resin particles can reliably perform the function as spacer particles. By making the liberation rate of the resin particles 42% by mass or less, the resin particles can be prevented from being detached from the toner base particles.

[0034] The liberation rate of the resin particles can be adjusted mainly by the content of the resin particles in the toner particles, the conditions when the resin particles are externally added to the toner base particles (e.g., stirring speed and external addition treatment time), and the number-average primary particle diameter of the resin particles. Specifically, the higher the content of the resin particles in the toner particles, the higher the liberation rate of the resin particles. Furthermore, the faster the above-mentioned stirring speed is, the stronger the resin particles adhere to the toner base particles, and the lower the liberation rate of the resin particles. Furthermore, the longer the above-mentioned external addition treatment time is, the stronger the resin particles adhere to the toner base particles, and the lower the liberation rate of the resin particles. Furthermore, the larger the number-average primary particle diameter of the resin particles, the higher the liberation rate of the resin particles.

[0035] The number-average primary particle diameter of the resin particles is preferably 30 nm or more and 130 nm or less, more preferably 50 nm or more and 100 nm or less, and even more preferably 70 nm or more and 90 nm or less. By making the number-average primary particle diameter of the resin particles 30 nm or more, the resin particles can easily function as spacer particles. In addition, by making the number-average primary particle diameter of the resin particles 130 nm or less, the resin particles can be more effectively prevented from being detached from the toner mother particles.

[0036] From the viewpoint of fully exerting the function of the resin particles while suppressing detachment from the toner mother particles, the content of the resin particles in the toner particles is preferably 0.1 parts by mass or more and 4.0 parts by mass or less, more preferably 0.2 parts by mass or more and 1.3 parts by mass or less, even more preferably 0.5 parts by mass or more and 1.0 parts by mass or less, and particularly preferably 0.7 parts by mass or more and 1.0 parts by mass or less, relative to 100 parts by mass of the toner mother particles. By making the content of the resin particles 0.1 parts by mass or more, the resin particles can easily exert their function as spacer particles. By making the content of the resin particles 4.0 parts by mass or less, the resin particles can be more effectively suppressed from being detached from the toner mother particles.

[0037] The resin particles can be produced, for example, by emulsion polymerization of raw material monomers (e.g., a styrene compound, a (meth)acrylic acid compound, and a crosslinking agent) in the presence of an ionic surfactant (emulsifier). Examples of polymerization initiators used in emulsion polymerization include benzoyl peroxide and 2,2'-azobis(2-amidinopropane) dihydrochloride. The amount of the ionic surfactant used is, for example, 1 part by mass or more and 5 parts by mass or less per 100 parts by mass of the raw material monomer. The amount of the polymerization initiator used is, for example, 4 parts by mass or more and 12 parts by mass or less per 100 parts by mass of the raw material monomer.

[0038] (ionic surfactants) The toner particles preferably further have an ionic surfactant attached to the surface of the resin particles. The ionic surfactant is derived from the ionic surfactant used in the production of the resin particles described above. The ionic surfactant adjusts the charging performance of the toner particles. The ionic surfactant may be a cationic surfactant or an anionic surfactant. The ionic surfactant is preferably a cationic surfactant.

[0039] The cationic surfactant may, for example, be an alkyltrimethylammonium salt having an alkyl group having from 10 to 25 carbon atoms. A specific cationic surfactant is preferably a cetyltrimethylammonium salt, and more preferably cetyltrimethylammonium chloride.

[0040] The anionic surfactant may, for example, be an alkylbenzenesulfonate having an alkyl group having from 10 to 25 carbon atoms. A specific anionic surfactant is preferably dodecylbenzenesulfonate, and more preferably sodium dodecylbenzenesulfonate.

[0041] (Silica particles) The silica particles impart fluidity to the toner particles. The silica particles are preferably silica particles that have been subjected to a surface treatment to impart positive charging properties. The number-average primary particle diameter of the silica particles is preferably 10 nm or more and 100 nm or less, more preferably 15 nm or more and 50 nm or less, and even more preferably 15 nm or more and 30 nm or less. By making the number-average primary particle diameter of the silica particles 10 nm or more, it is possible to more effectively suppress embedding of the silica particles in the toner mother particles. In addition, by making the number-average primary particle diameter of the silica particles 100 nm or less, it is possible to more effectively suppress detachment from the toner mother particles.

[0042] The liberation rate of the silica particles is 5% by mass or more and 25% by mass or less, and preferably 7% by mass or more and 15% by mass or less. By making the liberation rate of the silica particles 5% by mass or more, sufficient fluidity can be imparted to the toner particles. As a result, the image forming apparatus of this embodiment can stabilize the thickness of the developer layer made of the developer on the developing roller. By making the liberation rate of the silica particles 25% by mass or less, detachment of the silica particles from the toner mother particles can be suppressed.

[0043] The liberation rate of silica particles can be adjusted mainly by the content of silica particles in the toner particles, the conditions when the silica particles are externally added to the toner base particles (e.g., stirring speed and external addition treatment time), and the number-average primary particle diameter of the silica particles. Specifically, the higher the content of silica particles in the toner particles, the higher the liberation rate of the silica particles. In addition, the faster the above-mentioned stirring speed is, the stronger the silica particles adhere to the toner base particles, and the lower the liberation rate of the silica particles. Furthermore, the longer the above-mentioned external addition treatment time is, the stronger the silica particles adhere to the toner base particles, and the lower the liberation rate of the silica particles. Furthermore, the larger the number-average primary particle diameter of the silica particles, the higher the liberation rate of the silica particles.

[0044] From the viewpoint of fully exerting the function of the silica particles while suppressing detachment from the toner base particles, the content of the silica particles in the toner particles is preferably 0.1 parts by mass or more and 15.0 parts by mass or less, and more preferably 1.0 parts by mass or more and 3.0 parts by mass or less, per 100 parts by mass of the toner base particles.

[0045] (Other external additive particles) The external additive may further include other external additive particles other than the resin particles and the silica particles. Examples of the other external additive particles include particles of metal oxides (specifically, alumina, magnesium oxide, zinc oxide, etc.) and particles of organic acid compounds such as fatty acid metal salts (specifically, zinc stearate, etc.).

[0046] (Toner base particles) The toner base particles contain, for example, a binder resin as a main component. The toner base particles may further contain an internal additive (for example, at least one of a colorant, a release agent, a charge control agent, and a magnetic powder) as necessary. The toner base particles can be produced by a pulverization method or an aggregation method, and the pulverization method is preferred.

[0047] (Binding resin) From the viewpoint of providing a toner having excellent low-temperature fixing properties, the toner base particles preferably contain a thermoplastic resin as a binder resin, and more preferably contain a thermoplastic resin at a ratio of 85% by mass or more of the total binder resin. Examples of the thermoplastic resin include styrene resin, acrylic ester resin, olefin resin (e.g., polyethylene resin and polypropylene resin), vinyl resin (e.g., vinyl chloride resin, polyvinyl alcohol, vinyl ether resin, and N-vinyl resin), polyester resin, polyamide resin, and urethane resin. Copolymers of these resins, that is, copolymers in which any repeating unit is introduced into the above resin (e.g., styrene-acrylic ester resin, and styrene-butadiene resin), can also be used as the binder resin.

[0048] The content of the binder resin in the toner base particles is preferably from 60% by mass to 95% by mass, and more preferably from 80% by mass to 90% by mass.

[0049] From the viewpoint of improving the low-temperature fixability of the toner, the binder resin is preferably a polyester resin. The polyester resin is obtained by polycondensation of one or more polyhydric alcohols and one or more polycarboxylic acids. Examples of the polyhydric alcohols for synthesizing the polyester resin include dihydric alcohols (e.g., diol compounds and bisphenol compounds) and trivalent or higher alcohols. Examples of the polycarboxylic acids for synthesizing the polyester resin include divalent carboxylic acids and trivalent or higher carboxylic acids. Instead of the polycarboxylic acids, polycarboxylic acid derivatives capable of forming ester bonds by polycondensation (e.g., polycarboxylic acid anhydrides and polycarboxylic acid halides) may be used.

[0050] Examples of diol compounds include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 2-butene-1,4-diol, 1,5-pentanediol, 2-pentene-1,5-diol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, 1,4-benzenediol, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

[0051] Examples of bisphenol compounds include bisphenol A, hydrogenated bisphenol A, ethylene oxide adducts of bisphenol A (eg, polyoxyethylene(2,2)-2,2-bis(4-hydroxyphenyl)propane), and propylene oxide adducts of bisphenol A.

[0052] Examples of trihydric or higher alcohols include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-trihydroxymethylbenzene.

[0053] Examples of divalent carboxylic acids include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, succinic acid, alkylsuccinic acids (more specifically, n-butylsuccinic acid, isobutylsuccinic acid, n-octylsuccinic acid, n-dodecylsuccinic acid, isododecylsuccinic acid), and alkenylsuccinic acids (more specifically, n-butenylsuccinic acid, isobutenylsuccinic acid, n-octenylsuccinic acid, n-dodecenylsuccinic acid, isododecenylsuccinic acid).

[0054] Examples of trivalent or higher carboxylic acids include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxylpropane, 1,2,4-cyclohexanetricarboxylic acid, tetra(methylenecarboxyl)methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, and empol trimer acid.

[0055] The polyester resin is preferably a condensation polymer of terephthalic acid, an ethylene oxide adduct of bisphenol A, and trimellitic acid.

[0056] (Coloring agent) The toner base particles may contain a colorant. As the colorant, a known pigment or dye can be used according to the color of the toner. From the viewpoint of forming a high-quality image using the toner, the content of the colorant is preferably 1 part by mass or more and 20 parts by mass or less, more preferably 2 parts by mass or more and 10 parts by mass or less, relative to 100 parts by mass of the binder resin.

[0057] The toner base particles may contain a black colorant. Examples of the black colorant include carbon black. The black colorant may be a colorant toned to black using a yellow colorant, a magenta colorant, and a cyan colorant.

[0058] The toner base particles may contain color colorants, including yellow colorants, magenta colorants, and cyan colorants.

[0059] (Release agent) The toner base particles may contain a release agent. The release agent is used, for example, for the purpose of more effectively suppressing offset of the toner. The content of the release agent is preferably 1 part by mass or more and 20 parts by mass or less, more preferably 5 parts by mass or more and 15 parts by mass or less, relative to 100 parts by mass of the binder resin.

[0060] Examples of the release agent include aliphatic hydrocarbon waxes, oxides of aliphatic hydrocarbon waxes, vegetable waxes, animal waxes, mineral waxes, ester waxes mainly composed of fatty acid esters, and waxes in which a part or all of the fatty acid esters are deoxidized. Examples of the aliphatic hydrocarbon waxes include low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymers, polyolefin waxes, microcrystalline waxes, paraffin waxes, and Fischer-Tropsch waxes. Examples of the oxides of aliphatic hydrocarbon waxes include oxidized polyethylene waxes and block copolymers of oxidized polyethylene waxes. Examples of the vegetable waxes include candelilla wax, carnauba wax, Japan wax, jojoba wax, and rice wax. Examples of the animal waxes include beeswax, lanolin, and spermaceti. Examples of the mineral waxes include ozokerite, ceresin, and petrolatum. Examples of the ester waxes mainly composed of fatty acid esters include montan acid ester wax and castor wax. An example of the wax in which the fatty acid esters are partially or completely deoxidized is deoxidized carnauba wax. As the release agent, carnauba wax is preferred.

[0061] When the toner base particles contain a release agent, a compatibilizer may be added to the toner base particles in order to improve the compatibility between the binder resin and the release agent.

[0062] (Charge control agent) The toner base particles may contain a charge control agent. The charge control agent is used, for example, for the purpose of providing a toner having excellent charge stability or excellent charge rise characteristics. The charge rise characteristics of a toner are an index of whether or not the toner can be charged to a predetermined charge level in a short period of time. By incorporating a positively chargeable charge control agent in the toner base particles, the cationic nature of the toner base particles can be enhanced.

[0063] Examples of the positively charged charge control agent include azine compounds, direct dyes, acid dyes, alkoxylated amines, alkylamides, quaternary ammonium salt compounds, and resins containing quaternary ammonium cationic groups. The charge control agent is preferably a quaternary ammonium salt compound.

[0064] Examples of quaternary ammonium salt compounds include benzyldecylhexylmethylammonium chloride, decyltrimethylammonium chloride, 2-(methacryloyloxy)ethyltrimethylammonium chloride, and dimethylaminopropylacrylamide methyl chloride quaternary salt.

[0065] From the viewpoint of providing a toner having even more excellent charging stability, the content of the charge control agent is preferably 1 part by mass to 10 parts by mass, more preferably 1 part by mass to 5 parts by mass, per 100 parts by mass of the binder resin.

[0066] [Toner manufacturing method] The toner can be produced, for example, by a production method including a step of preparing toner base particles and a step of adding an external ingredient.

[0067] (Toner Base Particle Preparation Process) In the toner base particle preparation step, the toner base particles are prepared by, for example, an aggregation method or a pulverization method.

[0068] The aggregation method includes, for example, an aggregation step and a coalescence step. In the aggregation step, fine particles containing components constituting the toner base particles are aggregated in an aqueous medium to form aggregated particles. In the coalescence step, components contained in the aggregated particles are coalesced in the aqueous medium to form the toner base particles.

[0069] Next, the pulverization method will be described. The pulverization method allows the toner base particles to be prepared relatively easily and also allows the production cost to be reduced. When the toner base particles are prepared by the pulverization method, the preparation process of the toner base particles includes, for example, a melt-kneading process and a pulverization process. The preparation process of the toner base particles may further include a mixing process before the melt-kneading process. In addition, the preparation process of the toner base particles may further include at least one of a fine pulverization process and a classification process after the pulverization process.

[0070] In the mixing step, the binder resin and the internal additives added as necessary are mixed to obtain a mixture. In the melting and kneading step, the toner materials are melted and kneaded to obtain a molten and kneaded product. For example, the mixture obtained in the mixing step is used as the toner material. In the pulverizing step, the obtained molten and kneaded product is cooled, for example, to room temperature (25°C), and then pulverized to obtain a pulverized product. If it is necessary to reduce the diameter of the pulverized product obtained in the pulverizing step, a step of further pulverizing the pulverized product (fine pulverizing step) may be performed. In addition, if the particle size of the pulverized product is to be uniform, a step of classifying the obtained pulverized product (classifying step) may be performed. Through the above steps, the pulverized product, that is, toner base particles, is obtained.

[0071] (External addition process) In this process, toner particles are obtained by adhering resin particles and external additive particles containing silica to the surface of toner base particles. The method for adhering the external additive particles to the surface of toner base particles is not particularly limited, but for example, a method of stirring the toner base particles and the external additive particles with a mixer or the like can be mentioned. For example, an FM mixer (manufactured by Nippon Coke & Engineering Co., Ltd.) can be mentioned as a mixer.

[0072] The stirring speed during mixing in the external addition step is preferably from 2000 rpm to 5000 rpm, more preferably from 3000 rpm to 4000 rpm, and the external addition treatment time is preferably from 7 minutes to 38 minutes, more preferably from 20 minutes to 30 minutes.

[0073] This process may be carried out in multiple stages (for example, two stages). When this process is carried out in two stages, for example, in the first external addition process, the toner base particles and some of the external additive particles are stirred with a mixer or the like. Then, in the second external addition process, the mixture obtained in the first external addition process and the remaining external additive particles are stirred with a mixer or the like. In this way, by carrying out this process in multiple stages, the adhesive force of the multiple external additive particles to the toner base particles can be individually adjusted.

[0074] [Equipment details] Next, the configuration of the image forming apparatus according to the present embodiment other than the toner will be described with reference to the drawings. Fig. 2 is a diagram showing an example of the configuration of the image forming apparatus according to the present embodiment. Fig. 3 is a diagram showing the configuration of a developing device provided in the image forming apparatus of Fig. 2. Note that the drawings referred to are mainly shown in a schematic manner for easy understanding, and the size, number, shape, etc. of each illustrated component may differ from the actual size for convenience of drawing.

[0075] 2, the image forming apparatus 100 is a printer using a non-magnetic one-component development method that forms an image on a sheet P as a recording medium. The image forming apparatus 100 includes a feed section 15, a transport section 20, an image forming section 30, and a discharge section 80.

[0076] The feeding section 15 includes a cassette 16 that stores a plurality of sheets P. The sheets P are, for example, sheets made of paper or synthetic resin. The feeding section 15 feeds the sheets P to the conveying section 20. The conveying section 20 conveys the sheets P to the image forming section 30. The image forming section 30 forms an image on the sheets P. The conveying section 20 conveys the sheets P on which the images have been formed to the discharge section 80. The discharge section 80 discharges the sheets P outside the image forming apparatus 100.

[0077] The image forming section 30 includes an exposure unit 32, a first toner image generating unit 34A, a second toner image generating unit 34B, a third toner image generating unit 34C, a fourth toner image generating unit 34D, a first toner container 36A, a second toner container 36B, a third toner container 36C, a fourth toner container 36D, an intermediate transfer belt 62, a secondary transfer roller 64, and a fixing device 70. Here, the image forming apparatus 100 is of a tandem type, and the first toner image generating unit 34A, the second toner image generating unit 34B, the third toner image generating unit 34C, and the fourth toner image generating unit 34D are linearly arranged along the intermediate transfer belt 62.

[0078] In the following description of this specification, to avoid redundancy, the first toner image generating unit 34A, the second toner image generating unit 34B, the third toner image generating unit 34C, and the fourth toner image generating unit 34D may be referred to as the toner image generating unit 34A, the toner image generating unit 34B, the toner image generating unit 34C, and the toner image generating unit 34D, respectively. Similarly, the first toner container 36A, the second toner container 36B, the third toner container 36C, and the fourth toner container 36D may be referred to as the toner container 36A, the toner container 36B, the toner container 36C, and the toner container 36D, respectively.

[0079] The exposure unit 32 irradiates each of the toner image generating units 34A to 34D with light based on image data, and forms an electrostatic latent image on each of the toner image generating units 34A to 34D.

[0080] The toner image generating unit 34A forms a yellow toner image based on the electrostatic latent image. The toner image generating unit 34B forms a cyan toner image based on the electrostatic latent image. The toner image generating unit 34C forms a magenta toner image based on the electrostatic latent image. The toner image generating unit 34D forms a black toner image based on the electrostatic latent image.

[0081] The toner container 36A contains toner for forming a yellow toner image. The toner container 36B contains toner for forming a cyan toner image. The toner container 36C contains toner for forming a magenta toner image. The toner container 36D contains toner for forming a black toner image. The toner contained in the toner containers 36A to 36D is the above-mentioned toner (toner T shown in FIG. 3).

[0082] The intermediate transfer belt 62 rotates in the direction of arrow R1. Four color toner images are sequentially transferred onto the outer surface of the intermediate transfer belt 62 from the toner image generating units 34A to 34D. The secondary transfer roller 64 transfers the toner image formed on the outer surface of the intermediate transfer belt 62 onto a sheet P. The fixing device 70 applies heat and pressure to the sheet P to fix the toner image onto the sheet P.

[0083] The image forming apparatus 100 employs an oil-less fixing method that does not include a fixing oil application mechanism. The image forming apparatus 100 employs an oil-less fixing method, and therefore can be made smaller and less expensive. On the other hand, the toner used in the image forming apparatus 100 employing the oil-less fixing method tends to contain a relatively large amount of release agent in order to ensure fixability. In known toners, if the content of the release agent is increased, the toner particles tend to adhere more easily to the regulating blade 54 and the photoconductor drum 40. In contrast, the above-mentioned toner used in the image forming apparatus 100 contains silica particles and resin particles, and the liberation rate thereof is optimized. Therefore, the above-mentioned toner used in the image forming apparatus 100 can suppress the toner particles from adhering to the regulating blade 54 and the photoconductor drum 40.

[0084] Above, we have described the outline of the configuration of the image forming apparatus 100. Next, we will describe the details of the configuration of the image forming apparatus 100. In the following, when there is no need to distinguish between them, each of the toner image generating units 34A, 34B, 34C, and 34D will be referred to as the toner image generating unit 34.

[0085] The toner image generating unit 34 includes a photoconductor drum 40 as an image carrier, a charging device 42, a developing device 50, a primary transfer roller 44, a static eliminator 46, and a cleaner 48. In the toner image generating unit 34, the charging device 42, the developing device 50, the primary transfer roller 44, the static eliminator 46, and the cleaner 48 are disposed along the circumferential surface of the photoconductor drum 40 in this order.

[0086] The photoconductor drum 40 is disposed so as to contact the outer surface of the intermediate transfer belt 62. The primary transfer roller 44 is disposed so as to face the photoconductor drum 40 with the intermediate transfer belt 62 interposed therebetween.

[0087] The photoconductor drum 40 rotates in the direction of arrow R2. The charging device 42 charges the peripheral surface of the photoconductor drum 40. The peripheral surface of the photoconductor drum 40 is irradiated with light by the exposure unit 32, and an electrostatic latent image is formed.

[0088] As the photoreceptor drum 40, for example, a photoreceptor having a photosensitive layer containing amorphous silicon, or a photoreceptor having a photosensitive layer containing an organic photoconductor can be used.

[0089] 3, the developing device 50 has a developing roller 52, a regulating blade 54 (regulating member), a supply roller 56, an agitating member 58, and a housing 60. The developing device 50 supplies toner T to an electrostatic latent image formed on the circumferential surface of the photoconductor drum 40, and develops the electrostatic latent image by adhering the toner T to the electrostatic latent image. As a result, a toner image is formed on the circumferential surface of the photoconductor drum 40.

[0090] The developing roller 52 carries the toner T. The toner T is the above-mentioned toner (non-magnetic one-component developer). The toner T is supplied from a corresponding toner container (any of the toner containers 36A to 36D shown in FIG. 2). The developing roller 52 is disposed so as to come into contact with the photosensitive drum 40, and is provided so as to be rotatable in the direction of arrow R3 in accordance with the rotation of the photosensitive drum 40. The developing roller 52 supplies the carried toner T to the photosensitive drum 40.

[0091] 4, the developing roller 52 preferably has a conductive base material 52a, a silicone rubber layer 52b that covers the surface of the conductive base material 52a, and a urethane layer 52c that covers the surface of the silicone rubber layer 52b. The developing roller 52 has the silicone rubber layer 52b, which allows the elasticity of the developing roller 52 to be optimized. The developing roller 52 has the urethane layer 52c, which allows the surface resistance of the developing roller 52 to be optimized.

[0092] The regulating blade 54 regulates the thickness of a toner layer (not shown) made of toner T. The toner layer is formed on the developing roller 52. One end of the regulating blade 54 abuts against the peripheral surface of the developing roller 52. The regulating blade 54 is, for example, a leaf spring, and is pressed against the developing roller 52 with a predetermined pressure. Examples of materials constituting the regulating blade 54 include resins (more specifically, silicone resins, urethane resins, etc.), metals (more specifically, stainless steel, aluminum, copper, brass, phosphor bronze, etc.), and composite materials thereof.

[0093] The regulating blade 54 is preferably made of SUS. That is, in the image forming apparatus of this embodiment, the regulating member is preferably made of SUS. The SUS blade is conductive and easily elastically deformed to a certain degree, so that the thickness of the toner layer can be appropriately regulated. The contact line pressure of the regulating blade 54 against the developing roller 52 is preferably 15 N / m or more and 45 N / m or less, and more preferably 35 N / m or more and 45 N / m or less. By setting the contact line pressure of the regulating blade 54 to 15 N / m or more, the thickness of the toner layer can be appropriately regulated. By setting the contact line pressure of the regulating blade 54 to 45 N / m or less, the friction between the toner T and the developing roller 52 can be prevented from becoming excessively large, and the thickness of the toner layer can be sufficiently secured.

[0094] The supply roller 56 supplies toner T to the developing roller 52. The supply roller 56 is in contact with the developing roller 52 and is supported so as to be rotatable in the direction of arrow R4.

[0095] The stirring member 58 stirs the toner T and transports the toner T to the supply roller 56. The housing 60 accommodates the components of the developing device 50 and the toner T.

[0096] The developing device 50 is configured to form a toner layer using a regulating blade 54 abutted against the developing roller 52, while supplying toner T (more specifically, toner T contained in the toner layer) to the electrostatic latent image formed on the peripheral surface of the photosensitive drum 40, thereby developing the electrostatic latent image into a toner image.

[0097] 2, the configuration of the image forming apparatus 100 will be described in detail. The primary transfer roller 44 transfers the toner image formed on the circumferential surface of the photoconductor drum 40 to the outer surface of the intermediate transfer belt 62. The static eliminator 46 eliminates static electricity from the circumferential surface of the photoconductor drum 40 after the toner image has been transferred to the intermediate transfer belt 62. The cleaner 48 removes the toner T remaining on the circumferential surface of the photoconductor drum 40. The cleaner 48 has, for example, a cleaning blade.

[0098] The toner image transferred to the outer surface of the intermediate transfer belt 62 is transferred to the sheet P by the secondary transfer roller 64. That is, the secondary transfer roller 64 corresponds to a transfer section that transfers the toner image formed on the circumferential surface of the photosensitive drum 40 to the sheet P via the intermediate transfer belt 62. The sheet P to which the toner image has been transferred is transported to the fixing device 70 by the transport section 20. The fixing device 70 includes a pressure roller 72 that pressurizes the toner image transferred to the sheet P, and a fixing belt 74 that heats the toner image transferred to the sheet P. Note that a fixing roller may be used instead of the fixing belt 74. The sheet P transported to the fixing device 70 is heated and pressed between the pressure roller 72 and the fixing belt 74. As a result, the toner image (image) is fixed to the sheet P. Thereafter, the sheet P is discharged from the discharge section 80 to the outside of the image forming apparatus 100. In the above manner, the image forming apparatus 100 forms an image on the sheet P.

[0099] Since the image forming apparatus 100 uses the above-mentioned toner as a non-magnetic one-component developer, the occurrence of white streaks and uneven image density can be suppressed.

[0100] The image forming apparatus 100, which is an example of the image forming apparatus of the present embodiment, has been described above, but the image forming apparatus of the present embodiment is not limited to the image forming apparatus 100 described above. For example, the image forming apparatus of the present embodiment may be a monochrome image forming apparatus. The monochrome image forming apparatus includes, for example, one toner image generating unit and one toner container. The image forming apparatus of the present embodiment may also be a direct transfer type image forming apparatus. In the direct transfer type image forming apparatus, a transfer unit directly transfers a toner image on an image carrier to a recording medium. Furthermore, the developing roller may be a roller having a structure different from the layer structure shown in FIG. 4. Furthermore, the regulating member may be a member other than a regulating blade (for example, a regulating roller). EXAMPLES

[0101] The present invention will be described in more detail below using examples, but the present invention is not limited to the scope of the examples.

[0102] [Measurement of number average primary particle size] The number-average primary particle diameter of each particle (resin particle, silica particle, etc.) described in this example was measured at a magnification of 30,000 times using a scanning electron microscope (field emission scanning electron microscope, "JSM-7600F" manufactured by JEOL Ltd.) In measuring the number-average primary particle diameter, the circle equivalent diameter (Heywood diameter: diameter of a circle having the same area as the projected area of ​​the primary particle) of 100 primary particles was measured, and the number average value was calculated.

[0103] [Ultrasonic treatment of toner] A nonionic surfactant aqueous solution was obtained by mixing 2 parts by mass of a nonionic surfactant ("Emulgen (registered trademark) 120" manufactured by Kao Corporation, component: polyoxyethylene lauryl ether) with 98 parts by mass of ion-exchanged water. A nonionic surfactant aqueous solution (concentration: 2% by mass) was mixed with 100 parts by mass of a nonionic surfactant aqueous solution and 2 parts by mass of a toner to be measured to obtain a toner dispersion. The toner dispersion obtained was subjected to ultrasonic treatment for 5 minutes using an ultrasonic disperser ("Ultrasonic Miniwelder P128" manufactured by Ultrasonic Industries Co., Ltd., output: 100 W, oscillation frequency: 28 kHz). The toner dispersion that had been ultrasonically treated was then subjected to suction filtration using a Buchner funnel and qualitative filter paper ("FILTER PAPER No. 1" manufactured by Advantec Co., Ltd., pore size: approximately 5 μm) (suction filtration operation). Then, a reslurry operation in which 50 mL of ion-exchanged water was added to the filtered matter and the above-mentioned suction filtration operation were repeated three times (washing treatment). The surfactant attached to the surface of the toner particles was removed by the washing treatment. After the cleaning process, the filter cake and the filter paper on which it was placed were placed in an aluminum container. Next, the aluminum container was placed in a vacuum low-temperature dryer and vacuum dried at 40°C for 12 hours. This allowed the filter cake (toner after ultrasonic treatment) to be sufficiently dried. The dried filter cake was used as a measurement sample after ultrasonic treatment. Separately, a toner that had not been subjected to any treatment was prepared and used as an untreated measurement sample.

[0104] [Measurement of the liberation rate of resin particles] The liberation rate of resin particles was measured using the measurement sample after the ultrasonic treatment and the untreated measurement sample. A gas chromatograph mass spectrometer (Shimadzu Corporation, "GCMS-QP2010 Ultra") and a multi-shot pyrolyzer (Frontier Labs, Inc., "PY-3030D") were used as the measurement device. A GC column (Agilent Technologies, Inc., "Agilent (registered trademark) J&W Ultra Inert Capillary GC Column DB-5ms", phase: arylene phase in which arylene is added to siloxane polymer to strengthen the polymer main chain, inner diameter: 0.25 mm, film thickness: 0.25 μm, length: 30 m) was used as the column.

[0105] GC / MS analysis was performed on 100 μg of the measurement sample (either the measurement sample after ultrasonic treatment or the untreated measurement sample) under the following analytical conditions, and a mass spectrum (horizontal axis: ion mass / ion charge number, vertical axis: detection intensity) including peaks derived from the resin particles was obtained. Pyrolysis temperature: Heating furnace "600℃", interface part "320℃" Heating conditions: The temperature was raised from 40°C to 320°C at a rate of 28°C / min, and held at 320°C for 5 minutes. Carrier gas: Helium (He) gas (linear velocity 36.1 cm / min) Column head pressure: 49.7kPa Injection mode: Split injection (split ratio 1:200) Carrier flow rate: Total flow rate "204mL / min", column flow rate "1mL / min", purge flow rate "3mL / min"

[0106] The amount of resin particles contained in the measurement sample was determined based on the mass spectrum (GC / MS mass spectrum) obtained from the measurement sample by the above GC / MS analysis. More specifically, using a calibration curve (calibration curve showing the relationship between the peak area of ​​the GC / MS mass spectrum and the amount of resin particles) created in advance, the amount of resin particles contained in the measurement sample was determined from the peak area derived from the measured resin particles (more specifically, the peak area of ​​n-butyl methacrylate for resin particles (A) to (E), and the peak area of ​​methyl methacrylate for resin particles (F) to (G)). More specifically, by performing the above GC / MS analysis using the measurement sample after ultrasonic treatment, the amount of resin particles M contained in the toner particles after ultrasonic treatment was determined. 3R In addition, the amount of resin particles contained in the untreated toner particles, M 1R And, M 1R From M 3R The mass M of the resin particles detached from the toner base particles after ultrasonic treatment is calculated by subtracting 2R Next, add M 1R and M 2R The liberation rate of the resin particles was calculated by applying the above equation. Free resin particle ratio = 100 x M 2R / M 1R

[0107] [Measurement of the liberation rate of silica particles] The liberation rate of silica particles was measured using the measurement sample after the ultrasonic treatment and the untreated measurement sample. Using a tablet molding compression machine ("BRE-33" manufactured by Mayekawa Test Machinery Manufacturing Co., Ltd.), 1.5 g of the measurement sample (either the measurement sample after ultrasonic treatment or the untreated measurement sample) was pressurized (pressure 20 MPa, pressurization time 3 seconds) to prepare a cylindrical pellet with a diameter of 30 mm. The obtained pellet was subjected to fluorescent X-ray analysis under the following conditions to obtain a fluorescent X-ray spectrum (horizontal axis: energy, vertical axis: intensity (number of photons)) including a peak derived from silicon. The X-ray intensity of the peak derived from the measurement element in the obtained fluorescent X-ray spectrum was converted to a content ratio (unit: mass%) using a calibration curve created in advance. Based on the obtained content ratio, the amount of silica particles in the measurement sample was calculated.

[0108] (X-ray fluorescence analysis conditions) -Analysis equipment: Scanning X-ray fluorescence analyzer (Rigaku Corporation "ZSX") X-ray tube (X-ray source): Rh (rhodium) Excitation conditions: Tube voltage 50 kV, tube current 50 mA Measurement area (X-ray irradiation range): diameter 30 mm Measurement element: Silicon

[0109] In detail, the amount of silica particles contained in the toner particles after ultrasonic treatment, M, was determined by carrying out the above-mentioned fluorescent X-ray analysis using the measurement sample after ultrasonic treatment. 3S In addition, the amount of silica particles contained in the untreated toner particles, M 1S And, M 1S From M 3S The mass M of the silica particles detached from the toner base particles after ultrasonic treatment is calculated by subtracting the mass M 2S Next, add M 1S and M 2SThe liberation rate of silica particles was calculated by applying the above equation. Free silica particle ratio = 100 x M 2R / M 1R

[0110] [Preparation of binder resin] 1.0 mol of bisphenol A ethylene oxide adduct (polyoxyethylene (2,2)-2,2-bis(4-hydroxyphenyl)propane), 4.5 mol of terephthalic acid, 0.5 mol of trimellitic anhydride, and 4 g of dibutyltin oxide were charged into a reaction vessel. After the inside of the reaction vessel was filled with nitrogen, the contents of the reaction vessel were held at 230°C for 8 hours to cause a polycondensation reaction. Next, the inside of the reaction vessel was depressurized until the internal pressure of the reaction vessel became 8.3 kPa. As a result, the unreacted raw materials remaining in the reaction vessel were distilled off. Next, the contents of the reaction vessel were washed and dried. As a result, a binder resin (softening point 120°C), which is a polyester resin, was obtained.

[0111] [Preparation of toner base particles] Using an FM mixer ("FM-20B" manufactured by Nippon Coke & Engineering Co., Ltd.), 100 parts by mass of the above-mentioned binder resin (polyester resin), 5 parts by mass of carbon black ("REGAL (registered trademark) 330R" manufactured by Cabot Corporation) as a colorant, 10 parts by mass of carnauba wax ("Carnauba No. 1" manufactured by Kato Yoko Co., Ltd.) as a release agent, and 3 parts by mass of a quaternary ammonium salt compound ("FCA210PS" manufactured by Fujikura Kasei Co., Ltd.) as a charge control agent were mixed. The mixture obtained was then melt-kneaded at 150°C using a twin-screw extruder ("TEM45" manufactured by Toshiba Machine Co., Ltd.). The kneaded product obtained was then cooled. The kneaded product after cooling was coarsely pulverized using a Feather Mill (registered trademark) ("350 x 600" manufactured by Hosokawa Micron Corporation). The coarsely pulverized product obtained was finely pulverized using an airflow type pulverizer ("Jet Mill IDS-2" manufactured by Nippon Pneumatic Mfg. Co., Ltd.). The resulting finely ground material was classified using an elbow jet classifier (Nippon Steel Mining Co., Ltd., "Elbow Jet EJ-LABO type"). 50The volume median diameter was measured using a particle size meter (Beckman Coulter, Inc.'s "Coulter Counter Multisizer 3").

[0112] [Preparation of resin particles] Resin particles (A) to (G) used as external additive particles were prepared by the following method. Details are shown in Table 1. In Table 1, "particle size" refers to the number average primary particle size. "BMA" refers to n-butyl methacrylate. "MM" refers to methyl methacrylate. "DBS" refers to sodium dodecylbenzenesulfonate. "CPC" refers to cetylpyridinium chloride. "BC" refers to stearylbenzyldimethylammonium chloride.

[0113] (Resin particles (A)) Into a 1 L four-neck flask equipped with a stirring blade, a cooling tube, a thermometer, and a nitrogen inlet tube, 600 parts by mass of ion-exchanged water, 6 parts by mass of sodium dodecylbenzenesulfonate as an emulsifier (anionic surfactant), 100 parts by mass of n-butyl methacrylate, 20 parts by mass of styrene, 70 parts by mass of divinylbenzene, and 15 parts by mass of a polymerization initiator (benzoyl peroxide) were added while stirring the flask contents at a rotation speed of 100 rpm.

[0114] Next, while stirring the contents of the flask (rotation speed 100 rpm), nitrogen gas was introduced into the flask to create a nitrogen atmosphere in the flask. Furthermore, while stirring the contents of the flask, the temperature of the contents of the flask was raised to 90°C in a nitrogen atmosphere. Thereafter, the contents of the flask were reacted (specifically, polymerized) for 150 minutes while stirring under conditions of a nitrogen atmosphere and a temperature of 90°C. As a result, an emulsion containing a reaction product (resin particles (A) having a number-average primary particle diameter of 80 nm) was obtained. Next, the obtained emulsion was cooled and then subjected to solid-liquid separation. Next, the solid obtained by solid-liquid separation was thoroughly washed. Next, the solid content after washing was thoroughly dried to obtain a powder of resin particles (A). The resin particles (A) contained a crosslinked styrene-methacrylic resin.

[0115] (Resin particles (B)~(E)) Resin particles (B) to (E) were prepared in the same manner as in the preparation of resin particles (A), except that the reaction time was changed as shown in Table 1.

[0116] (Resin particles (F)) In a three-neck flask (reaction vessel) equipped with a nitrogen inlet tube, a reflux tube, and a dropping funnel, 4.0 parts by mass of cetylpyridinium chloride as an emulsifier (cationic surfactant) and 1230.0 parts by mass of ion-exchanged water were charged, and the cationic surfactant was dissolved in the ion-exchanged water. Separately, 1.5 parts by mass of 2,2'-azobis(2-amidinopropane) dihydrochloride as a polymerization initiator and 15.0 parts by mass of ion-exchanged water were mixed to prepare a polymerization initiator solution. Next, after the inside of the reaction vessel was made into a nitrogen atmosphere, the reaction vessel was heated until the temperature of the contents of the reaction vessel reached 70°C. Next, 16.5 parts by mass of the polymerization initiator solution (1.5 parts by mass of 2,2'-azobis(2-amidinopropane) dihydrochloride and 15.0 parts by mass of ion-exchanged water), 30.0 parts by mass of styrene, and 270.0 parts by mass of methyl methacrylate were dropped into the reaction vessel over 90 minutes. Next, the contents of the reaction vessel were reacted at 70°C for 60 minutes. This resulted in an emulsion containing a reaction product (resin particles (F) having a number average primary particle diameter of 60 nm). The resulting emulsion was then cooled and subjected to solid-liquid separation. Next, the solid matter obtained by solid-liquid separation was thoroughly washed. Next, the washed solid matter was thoroughly dried to obtain a powder of resin particles (F). The resin particles (F) contained a styrene-methacrylic resin.

[0117] (Resin particles (G)) Resin particles (G) powder was prepared in the same manner as in the preparation of resin particles (F), except that 1.5 parts by mass of stearylbenzyldimethylammonium chloride was used as an emulsifier (cationic surfactant) instead of 4.0 parts by mass of cetylpyridinium chloride (number average primary particle diameter 120 nm). Resin particles (G) contained styrene-methacrylic resin.

[0118] [Table 1]

[0119] In the crosslinked styrene-methacrylic resin contained in the resin particles (A) to (E), the content ratio of the first repeating unit (the repeating unit derived from a styrene compound) to the total repeating units was 10.5 mass%. In the above-mentioned crosslinked styrene-methacrylic resin, the content ratio of the second repeating unit (the repeating unit derived from an (meth)acrylic acid alkyl ester) to the total repeating units was 52.6 mass%. In the above-mentioned crosslinked styrene-methacrylic resin, the content ratio of the third repeating unit (the repeating unit derived from a crosslinking agent) to the total repeating units was 36.8 mass%.

[0120] In the styrene-methacrylic resin contained in the resin particles (F) to (G), the content ratio of the first repeating unit (the repeating unit derived from a styrene compound) to the total repeating units was 10.0 mass%. In the above-mentioned styrene-methacrylic resin, the content ratio of the second repeating unit (the repeating unit derived from an (meth)acrylic acid alkyl ester) to the total repeating units was 90.0 mass%.

[0121] <Toner manufacturing> Toners (T-1) to (T-6) and toners (t-1) to (t-6) shown in Table 2 were prepared by the following method. Toners (T-1) to (T-6) were used in the image forming apparatuses of Examples 1 to 6. Toners (t-1) to (t-6) were used in the image forming apparatuses of Comparative Examples 1 to 6. Table 2 also shows the liberation rate [mass %] of resin particles and the liberation rate [mass %] of silica particles in each toner measured by the above-mentioned method. In Table 2, "diameter" indicates the number-average primary particle diameter. "Amount" of resin particles or silica particles indicates the content [parts by mass] of resin particles or silica particles relative to 100 parts by mass of toner mother particles.

[0122] [Toner (T-1)] Using an FM mixer ("FM-10B" manufactured by Nippon Coke & Engineering Co., Ltd.), 100 parts by mass of the above-mentioned toner base particles, 2.0 parts by mass of silica particles (X) ("CAB-O-SIL (registered trademark) TG-7120" manufactured by Cabot Corporation, number average primary particle diameter 20 nm, hydrophobic silica particles), and 0.8 parts by mass of resin particles (A) were mixed at a rotation speed of 3,500 rpm for 25 minutes (time for the first external addition treatment). The resulting mixture was sieved through a 200 mesh (75 μm opening) sieve. This resulted in the production of toner (T-1).

[0123] [Toners (T-2) to (T-6) and (t-1) to (t-3)] Toners (T-2) to (T-6) and (t-1) to (t-3) were prepared in the same manner as in the preparation of toner (T-1), except that the types of resin particles and silica particles and the time of the first external addition treatment were changed as shown in Table 2. The silica particles (Y) are "AEROSIL (registered trademark) REA90" (dry silica particles to which positive charging has been imparted by surface treatment, number average primary particle diameter: 20 nm) manufactured by Nippon Aerosil Co., Ltd.

[0124] [Toner (t-4)] Using the FM mixer, 100 parts by mass of the above-mentioned toner base particles and 2.0 parts by mass of silica particles (X) were mixed at a rotation speed of 3,500 rpm for 10 minutes (first external addition treatment). Next, 0.6 parts by mass of resin particles (G) were added to the mixture obtained by the first external addition treatment, and the mixture was mixed at a rotation speed of 3,500 rpm for 25 minutes (second external addition treatment) using the FM mixer. The mixture obtained by the second external addition treatment was sieved using the sieve described above. This resulted in the toner (t-4).

[0125] [Toner (t-5)] Using the FM mixer, 100 parts by mass of the above-mentioned toner base particles and 2.0 parts by mass of silica particles (X) were mixed at a rotation speed of 3,500 rpm for 10 minutes (first external addition treatment). Next, 0.6 parts by mass of resin particles (F) were added to the mixture obtained by the first external addition treatment, and the mixture was mixed at a rotation speed of 3,500 rpm for 30 minutes (second external addition treatment) using the FM mixer. The mixture obtained by the second external addition treatment was sieved using the sieve described above. This resulted in the toner (t-5).

[0126] [Toner (t-6)] Using the FM mixer, 100 parts by mass of the above toner base particles and 0.8 parts by mass of resin particles (A) were mixed at a rotation speed of 3,500 rpm for 25 minutes (first external addition treatment). Next, 2.0 parts by mass of silica particles (Y) were added to the mixture obtained by the first external addition treatment, and the mixture was mixed at a rotation speed of 3,500 rpm for 25 minutes (second external addition treatment). The mixture obtained by the second external addition treatment was sieved using the sieve described above. This resulted in toner (t-6).

[0127] [Table 2]

[0128] <Evaluation> The toners (T-1) to (T-6) and (t-1) to (t-6) were fed into the developing device of an evaluation machine described later to form image forming apparatuses of Examples 1 to 6 and Comparative Examples 1 to 6, respectively. A first image formation test and a second image formation test were carried out for each image forming apparatus by the following method, and the formed images were evaluated for image defects (white streaks or uneven image density). The evaluation results are shown in Table 3.

[0129] [Evaluation machine] The evaluation machine used was a Kyocera Document Solutions Inc. "PA-2000" monochrome printer using a non-magnetic one-component developer. The evaluation machine was equipped with at least a developing device having a regulating blade and a developing roller, and a fixing roller. The regulating blade was a SUS blade. The developing roller had a conductive base material, a silicone rubber layer covering the surface of the conductive base material, and a urethane layer covering the surface of the silicone rubber layer. The contact line pressure of the regulating blade against the developing roller was 40 N / m. The recording medium used was Askul Corporation's "Multi Paper Super White A4."

[0130] [First image formation test] The first image formation test was performed at a temperature of 23°C and a relative humidity of 50%RH. Using an evaluation machine, 1,500 pattern images (printing rate of 5%) were intermittently printed on a recording medium. In the intermittent printing, two sheets were printed in succession, followed by a 300-second interval, and this set was repeated.

[0131] [Second image formation test] The second image formation test was carried out at a temperature of 10° C. and a relative humidity of 10% RH. Using an evaluation machine, 1500 pattern images (printing rate of 1%) were continuously printed on a recording medium.

[0132] [judgement] The images formed in the first image formation test or the second image formation test were visually observed every 50th sheet to confirm the occurrence of image defects (white streaks or uneven density). In the first image formation test or the second image formation test, the evaluation object in which no image defects were confirmed even in the last image formed (the image formed on the 1500th recording medium) was judged as "A (pass)". In the first image formation test or the second image formation test, the evaluation object in which the occurrence of image defects was confirmed was judged as "B (fail)".

[0133] In Table 3, "Judgment" indicates in parentheses which image defect occurred among the evaluation objects where image defects occurred. In Table 3, "Number of sheets" indicates the number of sheets on which image defects occurred. However, an evaluation object with a "Number of sheets" of 1500 indicates that no image defects were confirmed even in the last image formed (image formed on the 1500th recording medium).

[0134] [Table 3]

[0135] As shown in Tables 1 to 3, the image forming apparatuses of Examples 1 to 6 were provided with a non-magnetic one-component developer, an image carrier, and a developing device that supplies the non-magnetic one-component developer to an electrostatic latent image formed on the surface of the image carrier to develop the electrostatic latent image. The developing device had a developing roller that carried the non-magnetic one-component developer, and a regulating member that regulated the thickness of a developer layer composed of the non-magnetic one-component developer, and was configured to supply the non-magnetic one-component developer to the electrostatic latent image while forming a developer layer by the regulating member abutted on the developing roller. The non-magnetic one-component developer contained a positively charged toner containing toner particles. The toner particles had toner base particles and external additive particles attached to the surfaces of the toner base particles. The external additive particles contained resin particles and silica particles. When the toner was subjected to ultrasonic treatment for 5 minutes by applying ultrasonic vibrations at a frequency of 28 kHz and an output of 100 W, the liberation rate of the resin particles was 18% by mass or more and 42% by mass or less, and the liberation rate of the silica particles was 5% by mass or more and 25% by mass or less. Each of the image forming apparatuses of Examples 1 to 6 was able to suppress the occurrence of white streaks and uneven image density.

[0136] On the other hand, the toners (t-1) and (t-5) used in the image forming apparatuses of Comparative Examples 1 and 5 had a resin particle liberation rate of less than 18% by mass. It is judged that the resin particles of the toners (t-1) and (t-5) adhered relatively strongly to the toner base particles, making it difficult for the resin particles to function as spacer particles. As a result, it is judged that the silica particles of the toners (t-1) and (t-5) were embedded in the toner base particles as the image was formed, making the surface of the toner base particles more likely to adhere to other members (especially the regulating blade). As a result, it is judged that the toner particles of the image forming apparatuses of Comparative Examples 1 and 5 adhered to the regulating blade, causing white streaks in the formed images.

[0137] The toners (t-2) and (t-6) used in the image forming apparatuses of Comparative Examples 2 and 6 had a liberation rate of silica particles of less than 5% by mass. It is judged that the toner particles of the toners (t-2) and (t-6) had insufficient fluidity because the silica particles adhered relatively strongly to the toner base particles. As a result, it is judged that the image forming apparatuses of Comparative Examples 2 and 6 could not maintain a constant thickness of the developer layer (toner layer) formed on the developing roller, causing white streaks in the formed images.

[0138] The toners (t-3) and (t-4) used in the image forming apparatuses of Comparative Examples 3 and 4 had a resin particle liberation rate of more than 42% by mass. It is determined that the resin particles of the toners (t-3) and (t-4) did not adhere strongly enough to the toner base particles, and therefore the resin particles were detached from the toner base particles during image formation. It is determined that the resin particles detached from the toner base particles were retained at the position where the developing roller and the regulating blade were in contact. As a result, it is determined that the image forming apparatuses of Comparative Examples 3 and 4 caused uneven image density in the images formed. [Industrial Applicability]

[0139] The image forming apparatus of this embodiment can be used as, for example, a copier, a printer, or a multifunction machine. [Explanation of symbols]

[0140] 1 Toner particles 2. Toner base particles 3. External additives 5. Resin particles 6. Silica particles 40 Photoconductor drum (image carrier) 50 Developing device 52 Developing roller 54 Regulating blade (regulating member) 100 Image forming device T Toner

Claims

1. A non-magnetic one-component developer; An image carrier; a developing device that supplies the non-magnetic one-component developer to an electrostatic latent image formed on a surface of the image carrier to develop the electrostatic latent image, the developing device includes a developing roller that carries the non-magnetic one-component developer, and a regulating member that regulates a thickness of a developer layer composed of the non-magnetic one-component developer, and is configured to supply the non-magnetic one-component developer to the electrostatic latent image while forming the developer layer by the regulating member that is in contact with the developing roller, The non-magnetic one-component developer contains a positively charged toner containing toner particles, The toner particles include toner base particles and external additive particles attached to the surfaces of the toner base particles, The external additive particles include resin particles and silica particles, When the toner was subjected to ultrasonic treatment in which ultrasonic vibrations at a frequency of 28 kHz and an output of 100 W were applied for 5 minutes, the liberation rate of the resin particles is 18% by mass or more and 42% by mass or less; The liberation rate of the silica particles is 5% by mass or more and 25% by mass or less.

2. 2. The image forming apparatus according to claim 1, wherein the developing roller has a conductive base material, a silicone rubber layer covering a surface of the conductive base material, and a urethane layer covering a surface of the silicone rubber layer.

3. The regulating member is a stainless steel blade, 3. The image forming apparatus according to claim 1, wherein the contact line pressure of the regulating member against the developing roller is 15 N / m or more and 45 N / m or less.

4. 3. The image forming apparatus according to claim 1, wherein the content of the resin particles relative to 100 parts by mass of the toner base particles is 0.2 parts by mass or more and 1.3 parts by mass or less.

5. 3. The image forming apparatus according to claim 1, wherein the number average primary particle diameter of the resin particles is 30 nm or more and 130 nm or less.

6. 3. The image forming apparatus according to claim 1, wherein the resin particles contain a crosslinked styrene-(meth)acrylic resin.

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