Toner for electrostatic image development, method of manufacturing toner for electrostatic image development and image forming method

Abstract

To provide: toner for electrostatic image development capable of sufficiently enhancing a heat-resistant storage property and low-temperature fixability; a method of manufacturing the toner for electrostatic image development; and an image forming method using the toner for electrostatic image development.SOLUTION: The present invention relates to toner for electrostatic image development that includes binder resin in toner base particles, wherein the binder resin includes a polymer having a structural unit deriving from a vinyl monomer, and the polymer has a number average molecular weight Mn of 800 to 30,000. The polymer includes, at a molecular terminal of a principal chain, at least one kind of functional group selected from a group of an alicyclic alkyl group with five or more carbons, a branched alkyl group with four or more carbons, a straight chain alkyl group with 10 or more carbons, a hydroxy group, and a carboxyl group.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a toner for electrostatic charge image development, a method for manufacturing the toner for electrostatic charge image development, and an image forming method.

Background Art

[0002] With the decrease in printing volume, the need for digital printing that enables small-lot printing has been increasing in recent years. In the printing business, it is important to increase productivity per unit time, and even in digital printing, speeding up the print output speed is a major issue.

[0003] As one of the toner fixing methods, in the widely used heat fixing method, in recent years, reduction of thermal energy during toner image fixing has been studied for the purpose of speeding up the printing speed and saving energy. In order to reduce the thermal energy during toner image fixing, it is required to improve the low-temperature fixability of the toner, and methods for achieving this have been studied.

[0004] For example, Patent Document 1 discloses a toner containing a colorant and a release agent, in which the release agent melts at a temperature of 65°C to 90°C and precipitates from the inside of the toner to the outside, and the colored particle toner and the release agent form a sea-island structure. In Patent Document 1, it is stated that the low-temperature fixability and the like are enhanced by the toner.

[0005] Also, Patent Document 2 discloses a toner binder containing a hybrid resin (A) of a polyester resin and a vinyl resin, and a resin (B) having a structure in which a vinyl resin (b) having an SP value of 10.0 to 12.6 (cal / cm 3 ) 1 / 2 is grafted, and the pulverization rate is 60% or more. In Patent Document 2, it is stated that the low-temperature fixability is enhanced by the toner containing the toner binder.

[0006] Further, Patent Document 3 discloses a toner binder resin obtained by melt-kneading an amorphous resin (X) containing a specific monomer in a specific amount and having a molecular weight of 20,000 or more, an amorphous resin (Y) containing a specific monomer in a specific amount and having a molecular weight of 10,000 or more, and a crystalline resin (Z). In Patent Document 3, it is said that a toner containing the toner binder resin achieves both low-temperature fixability and offset resistance.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, according to the findings of the present inventors, toners that are said to have enhanced low-temperature fixability, such as those in Patent Documents 1 to 3, may involve lowering the melting point or the glass transition temperature of the resin used in the toner, and there is a problem that the heat-resistant storage property deteriorates.

[0009] The present invention has been made in view of the above problems, and an object thereof is to provide an electrostatic charge image developing toner capable of sufficiently enhancing heat-resistant storage property and low-temperature fixability, a method for producing the electrostatic charge image developing toner, and an image forming method using the electrostatic charge image developing toner.

Means for Solving the Problems

[0010] In order to solve the above problems, there is provided an electrostatic charge image developing toner containing a binder resin in toner base particles, wherein the binder resin contains a polymer having a structural unit derived from a vinyl monomer and having a number average molecular weight Mn of 800 to 30,000, and the polymer contains a polymer having at least one functional group selected from the group consisting of an alicyclic alkyl group having 5 or more carbon atoms, a branched alkyl group having 4 or more carbon atoms, a linear alkyl group having 10 or more carbon atoms, a hydroxy group, and a carboxy group at the molecular terminal of the main chain. The present inventors have found that such an electrostatic charge image developing toner is suitable, and thus completed the present invention.

[0011] The reason for this is not necessarily clear, but it is considered as follows. By using a polymer having a relatively low molecular weight, the molecular mobility of the polymer in the binder resin at the fixing temperature (100 to 150°C) is likely to increase, so that the low-temperature fixability is enhanced. However, at the same time, since the molecular motion is also likely to increase at the storage temperature (around 55°C), the surface of the toner particles is likely to soften during storage, the fusion of the toner particles progresses, and the heat-resistant storage property is likely to deteriorate.

[0012] By introducing a bulky functional group or a functional group that easily forms a hydrogen bond at the main chain terminal of a polymer having a relatively low molecular weight, it becomes easier to inhibit the rotational motion of the main chain with a smaller introduction amount as compared with introducing a similar functional group into the side chain. Therefore, it becomes easier to suppress the molecular motion at the storage temperature (around 55°C) while maintaining the low-temperature fixability. As a result, it is considered that the surface of the toner particles is less likely to soften during storage, the fusion of the toner particles is suppressed, and the heat-resistant storage property is likely to be enhanced. On the other hand, at the fixing temperature (100 to 150°C), the molecular motion becomes active and it becomes a temperature region where the translational motion of the main chain can occur, so that the inhibitory effect of the molecular motion by the molecular terminal becomes less likely to act. As a result, at the fixing temperature (100 to 150°C), the molecular motion is sufficiently likely to increase, and the low-temperature fixability is considered to be enhanced.

[0013] That is, the above problems can be solved by the following configuration.

[0014] [1] An electrostatic charge image developing toner containing a binder resin in toner base particles, The binder resin contains a polymer having a structural unit derived from a vinyl monomer, The number average molecular weight Mn of the polymer is 800 to 30,000, The polymer includes a polymer having at least one functional group selected from the group consisting of an alicyclic alkyl group having 5 or more carbon atoms, a branched alkyl group having 4 or more carbon atoms, a linear alkyl group having 10 or more carbon atoms, a hydroxy group, a hydroxyalkyl group, a carboxy group, and a carboxyalkyl group at the molecular terminal of the main chain, Electrostatic charge image developing toner.

[0015] [2] The polymer includes a polymer having at least one functional group selected from the group consisting of an alicyclic alkyl group having 5 or more carbon atoms, a carboxy group, and a carboxyalkyl group at the molecular terminal of the main chain, The electrostatic charge image developing toner according to [1].

[0016] [3] The polymer includes a polymer having at least one functional group selected from the group consisting of an adamantyl group, a cyclohexyl group, a carboxyalkyl group having a linear alkylene group having 1 to 8 carbon atoms, a carboxyalkyl group having a branched alkylene group having 1 to 8 carbon atoms, and a carboxyalkyl group having an alicyclic alkylene group having 5 or more carbon atoms at the molecular terminal of the main chain, The electrostatic charge image developing toner according to [2].

[0017] [4] The number average molecular weight Mn of the polymer is 800 to 20,000, The electrostatic charge image developing toner according to [1] to [3].

[0018] [5] The structural unit is a structural unit derived from at least one monomer selected from the group consisting of styrenes and (meth)acrylic acid esters, The electrostatic charge image developing toner according to [1] to [4].

[0019] [6] The structural unit is a structural unit derived from at least one monomer selected from the group consisting of methoxystyrene, isobutyl (meth)acrylate, isobornyl (meth)acrylate, phenethyl (meth)acrylate, and methyl (meth)acrylate. The toner for electrostatic charge image development according to [5].

[0020] [7] A method for manufacturing a toner for electrostatic charge image development containing a binder resin in toner base particles, preparing a particle dispersion of a binder resin containing a polymer having at least one functional group selected from the group consisting of an alicyclic alkyl group having 5 or more carbon atoms, a branched alkyl group having 4 or more carbon atoms, a linear alkyl group having 10 or more carbon atoms, a hydroxy group, a hydroxyalkyl group, a carboxy group, and a carboxyalkyl group at the molecular terminal of the main chain; aggregating the particles of the binder resin in the particle dispersion of the binder resin to fuse the particles together, the method comprising: A method for manufacturing a toner for electrostatic charge image development.

[0021] [8] The step of preparing the particle dispersion of the binder resin is preparing an aqueous medium containing a chain transfer agent having at least one functional group selected from the group consisting of an alicyclic alkyl group having 5 or more carbon atoms, a branched alkyl group having 4 or more carbon atoms, a linear alkyl group having 10 or more carbon atoms, a hydroxy group, and a carboxy group and / or a polymerization initiator having the functional group; polymerizing a vinyl monomer in the prepared aqueous medium to prepare the particle dispersion of the binder resin, the method comprising: The method for manufacturing a toner for electrostatic charge image development according to [7].

[0022] [9] A step of attaching the toner for electrostatic charge image development according to any one of [1] to [6] to a recording medium, a step of fixing the attached toner for electrostatic charge image development to the recording medium, An image forming method having: [Advantages of the Invention]

[0023] According to the present invention, there are provided an electrostatic charge image developing toner capable of sufficiently enhancing heat-resistant storage stability and low-temperature fixing property, a method for manufacturing the electrostatic charge image developing toner, and an image forming method using the electrostatic charge image developing toner.

Brief Description of the Drawings

[0024]

Figure 1

Embodiments for Carrying Out the Invention

[0025] In this specification, a numerical range represented by using "~" means a range including the numerical values described before and after "~" as a lower limit value and an upper limit value.

[0026] 1. Electrostatic Charge Image Developing Toner The electrostatic charge image developing toner according to the present embodiment can develop an electrostatic charge image (electrostatic latent image) formed on an image carrier such as a photoreceptor.

[0027] Further, the electrostatic charge image developing toner according to the present embodiment is an electrostatic charge image developing toner containing a binder resin in toner base particles, the binder resin contains a polymer having a structural unit derived from a vinyl monomer, the number average molecular weight Mn of the polymer is 800 to 30000, and the polymer contains a polymer having at least one kind of functional group selected from the group consisting of an alicyclic alkyl group having 5 or more carbon atoms, a branched alkyl group having 4 or more carbon atoms, a linear alkyl group having 10 or more carbon atoms, a hydroxy group, a hydroxyalkyl group, a carboxy group, and a carboxyalkyl group (hereinafter, these functional group groups are also referred to as "first functional group groups") at the molecular terminal of the main chain.

[0028] The toner may be a one-component developer or a two-component developer having toner base particles and carrier particles.

[0029] Hereinafter, the toner according to the present embodiment will be described in more detail.

[0030] 1-1. Toner Base Particles The toner base particles according to this embodiment contain a binder resin.

[0031] The volume-based median diameter (D 50 ) of the toner base particles is preferably 4.0 μm to 10.0 μm, more preferably 5.0 μm to 9.0 μm. By having the volume-based median diameter of 4.0 μm or more, the transfer efficiency of the toner can be increased. Also, by having the volume average particle diameter of 10.0 μm or less, the image quality of an image including fine lines and dots can be improved.

[0032] The volume-based average particle diameter of the toner base particles can be measured using a particle size distribution measuring device (manufactured by Beckman Coulter, Coulter Multisizer 3). A computer system equipped with data processing software Software V3.51 was connected to the particle size distribution measuring device. Specifically, 0.02 g of a sample (toner base particles) is added to 20 mL of a surfactant solution (for example, a surfactant solution obtained by diluting a neutral detergent containing a surfactant component 10 times with pure water for the purpose of dispersing the toner base particles) and allowed to mix. Then, ultrasonic dispersion treatment is performed for 1 minute to prepare a dispersion of the toner base particles. This dispersion is pipetted into a beaker containing an electrolytic solution (manufactured by Beckman Coulter, ISOTON II) in a sample stand until the display concentration of the measuring device reaches 8%. By setting this concentration, reproducible measurement values can be obtained. Then, in the measuring device, the number of measured particles is set to 25,000, the aperture diameter is set to 100 μm, the measurement range of 2 to 60 μm is divided into 256 segments to calculate frequency values, and based on this, the volume-based average particle diameter is calculated.

[0033] 1-1-1. Binder Resin The binder resin according to this embodiment contains a polymer having a structural unit derived from a vinyl monomer, the number average molecular weight Mn of the polymer is 800 to 30,000, and the polymer contains a polymer having at least one kind of functional group contained in the first functional group group at the molecular terminals of the main chain.

[0034] In addition, the molecular terminals of the main chain in this application do not include the terminal sites of the side chains, but only refer to the terminal sites of the main chain. Generally, a polymer having a linear main chain has two molecular terminals per molecule, and a polymer having a non-linear main chain may have three or more molecular terminals per molecule.

[0035] 1-1-1-1. Monomers Used in Polymers The vinyl monomers used in the polymers are not particularly limited as long as they are known vinyl monomers. Examples of vinyl monomers include styrenes, (meth)acrylate esters, vinyl monomers having acidic groups or alkaline groups, and the like. Examples of styrenes include styrene, methoxystyrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o-ethylstyrene, m-ethylstyrene, p-ethylstyrene, o-acetoxystyrene, m-acetoxystyrene, p-acetoxystyrene, and the like. Examples of (meth)acrylate esters include methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, tert-butyl (meth)acrylate, iso-butyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isobornyl (meth)acrylate, stearyl acrylate, lauryl (meth)acrylate, phenyl (meth)acrylate, phenethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, and the like. Examples of acidic groups or alkaline groups that may be included in the monomers include carboxy groups, sulfo groups, phosphate groups, and the like. Examples of vinyl monomers having acidic groups or alkaline groups include (meth)acrylic acid, maleic acid, itaconic acid, fumaric acid, and the like. Note that “(meth)acryl” is a general term for acrylic and methacrylic, and means one or both of them.

[0036] Among these, from the viewpoint of facilitating the uniform dispersion of the wax, the vinyl monomer preferably contains at least one monomer selected from the group consisting of styrenes and (meth)acrylic acid esters. Also, from the same viewpoint, the vinyl monomer more preferably contains at least one monomer selected from the group consisting of methoxystyrene, isobutyl (meth)acrylate, isobornyl (meth)acrylate, and phenethyl (meth)acrylate.

[0037] Among the structural units contained in the polymer, the structural units derived from styrenes and (meth)acrylic acid esters are preferably 10% by mass to 100% by mass, and more preferably 20% by mass to 90% by mass. When the structural units derived from styrenes and (meth)acrylic acid esters are 10% by mass or more, the release agent is likely to be uniformly dispersed. Also, when it is 90% by mass or less, it is easy to enhance the fixing property. From the same viewpoint, among the structural units contained in the polymer, the structural units derived from methoxystyrene, isobutyl (meth)acrylate, isobornyl (meth)acrylate, phenethyl (meth)acrylate, and methyl (meth)acrylate are preferably 10% by mass to 100% by mass, and more preferably 20% by mass to 90% by mass.

[0038] 1-1-1-2. Molecular Terminals of the Polymer Main Chain The polymer according to this embodiment includes a polymer having at least one functional group contained in the first functional group group at the molecular terminal of the main chain.

[0039] Among the first functional group group, examples of the alicyclic alkyl group having 5 or more carbon atoms include a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, a cyclodecyl group, a norbornyl group, an adamantyl group, and the like. The carbon number of the alicyclic alkyl group is preferably 5 to 15, and more preferably a cyclohexyl group or an adamantyl group.

[0040] Among the first functional groups, examples of branched alkyl groups having 4 or more carbon atoms include a 2-butyl group, a tert-butyl group, a 2-pentyl group, a 3-pentyl group, an isopentyl group, a neopentyl group, a tert-pentyl group, and the like. The number of carbon atoms in the branched alkyl group is preferably 4 to 12.

[0041] Among the first functional groups, examples of linear alkyl groups having 10 or more carbon atoms include a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group, and the like. The number of carbon atoms in the linear alkyl group is preferably 10 to 20.

[0042] Among the first functional groups, examples of hydroxyalkyl groups include a hydroxymethyl group, a hydroxyethyl group, a hydroxypropyl group, a hydroxybutyl group, a hydroxycyclopentyl group, a hydroxytricyclo(3.3.1.13,7)decyl group, and the like. The number of carbon atoms in the alkylene chain contained in the hydroxyalkyl group is preferably 1 to 15.

[0043] Among the first functional groups, examples of carboxyalkyl groups include a carboxymethyl group, a carboxyethyl group, a carboxypropyl group, a carboxybutyl group, a carboxycyclopentyl group, a carboxytricyclo(3.3.1.13,7)decyl group, and the like. The number of carbon atoms in the alkylene chain contained in the carboxyalkyl group is preferably 1 to 15. When the alkylene chain is a linear alkylene chain, the number of carbon atoms in the alkylene chain is preferably 1 to 8. When the alkylene chain is a branched alkylene chain, the number of carbon atoms in the alkylene chain is preferably 1 to 8. When the alkylene chain is an alicyclic alkylene chain, the number of carbon atoms in the alkylene chain is preferably 5 or more, and more preferably 5 to 15.

[0044] Among these first functional group groups, as the functional group contained at the molecular terminal, it is preferable to have an alicyclic alkyl group having 5 or more carbon atoms, a carboxy group, or a carboxyalkyl group having a main chain at the molecular terminal. Further, as the functional group contained at the molecular terminal, an adamantyl group, a cyclohexyl group, a carboxyalkyl group having a linear alkylene group having 1 to 8 carbon atoms, a carboxyalkyl group having a branched alkylene group having 1 to 8 carbon atoms, or a carboxyalkyl group having an alicyclic alkylene group having 5 or more carbon atoms is more preferably present at the molecular terminal of the main chain. By having such a molecular terminal, it becomes easier to increase the rigidity of the functional group, increase the steric hindrance, increase the hydrogen bonding property of the functional group, and easily obtain the inhibitory effect of molecular motion by the molecular terminal, and it becomes easier to improve the heat-resistant storage property.

[0045] The polymer may include a polymer that does not have a functional group contained in the first functional group group at the molecular terminal of the main chain, or may be a mixture of a polymer having at least one kind of functional group contained in the first functional group group at the molecular terminal of the main chain and a polymer that does not have a functional group contained in the first functional group group at the molecular terminal of the main chain. The polymer preferably contains 10 mol% to 75 mol% of the functional group contained in the first functional group group with respect to the total number of moles at the molecular terminal of the main chain. By containing 10 mol% or more of the functional group, it becomes easier to obtain the inhibitory effect of molecular motion by the molecular terminal, and the heat-resistant storage property is likely to increase. Further, by setting the functional group to 75 mol% or less, it becomes easier to fix at low temperature. From the same viewpoint, it is more preferable to contain 20 mol% to 75 mol% of the functional group with respect to the total number of moles at the molecular terminal of the main chain, and it is even more preferable to contain 40 mol% to 75 mol%.

[0046] The structure of the molecular terminal contained in the polymer and the introduction rate of the functional group contained in the first functional group group can be measured by a nuclear magnetic resonance (NMR) method or the like.

[0047] 1-1-1-3. Other properties of the polymer The number average molecular weight Mn of the polymer having a structural unit derived from a vinyl monomer is preferably from 800 to 20,000. When the number average molecular weight Mn is 800 or more, it is easy to enhance the high-temperature storage stability. Also, when the number average molecular weight Mn is 20,000 or less, the melt viscosity of the toner can be appropriately lowered, making it easy to enhance the low-temperature fixability. From the same perspective, it is more preferably from 800 to 8,000.

[0048] The measurement of the number average molecular weight Mn is carried out using the apparatus "HLC-8220" (manufactured by Tosoh Corporation) and the column "TSKguardcolumn + TSKgel SuperHZM-M3 series" (manufactured by Tosoh Corporation). While maintaining the column temperature at 40 °C, tetrahydrofuran (THF) is flowed as the carrier solvent at a flow rate of 0.2 ml / min. The measurement sample is dissolved in tetrahydrofuran to a concentration of 1 mg / ml under the dissolution conditions of being treated with an ultrasonic disperser at room temperature (25 °C) for 5 minutes. Then, it is treated with a membrane filter having a pore size of 0.2 μm. 10 μl of the treated sample solution is injected into the apparatus together with the above-mentioned carrier solvent, and the molecular weight distribution of the measurement sample is detected using a refractive index detector (RI detector), and the number average molecular weight Mn is measured as a standard polystyrene conversion value.

[0049] The content of the polymer having a structural unit derived from a vinyl monomer is preferably from 60% by mass to 100% by mass or less, more preferably from 70% by mass to 100% by mass or less, based on the total mass of the binder resin.

[0050] 1-1-1-4. Other Components Contained in the Binder Resin The binder resin may contain other known resins in addition to the polymer having a structural unit derived from a vinyl monomer.

[0051] The other resin may be a thermoplastic resin or a thermosetting resin, but a thermoplastic resin is preferred.

[0052] Examples of the thermoplastic resin include polyester resins, silicone resins, olefin resins, polyamide resins, and epoxy resins.

[0053] The other resin may be an amorphous resin or a crystalline resin. Alternatively, it may be a composite resin in which a crystalline resin and an amorphous resin are hybridized. Among these, from the viewpoint of further enhancing low-temperature fixability, a crystalline resin is preferable.

[0054] In the present specification, the crystalline resin means a resin in which a melting point is observed in the measurement by differential scanning calorimetry (DSC). Further, the amorphous resin means a resin in which no melting point is observed in the measurement by DSC. In the present specification, that a melting point is observed in the resin means that a peak with a half-value width of the endothermic peak within 15 °C is observed when measured at a heating rate of 10 °C / min in DSC.

[0055] As the crystalline resin, known crystalline resins can be used. Examples of the crystalline resin include crystalline polyester resins, crystalline polyurethane resins, crystalline polyurea resins, crystalline polyamide resins, crystalline polyether resins, and the like. Among these, crystalline polyester resins are preferable.

[0056] The crystalline polyester resin is obtained by a dehydration condensation reaction of a polyvalent carboxylic acid and a polyhydric alcohol.

[0057] The polyvalent carboxylic acid may be a carboxylic acid having a valence of 2 or higher, and may also be a carboxylic acid having a valence of 3 or higher such as trimellitic acid or pyromellitic acid. Among these, from the viewpoint of enhancing the crystallinity of the crystalline polyester, dicarboxylic acids are preferred. 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.

[0058] The polyhydric alcohol may be an alcohol having a valence of 2 or higher, and may also be an alcohol having a valence of 3 or higher such as glycerin, pentaerythritol, trimethylolpropane, and sorbitol. Among these, from the viewpoint of enhancing the crystallinity of the crystalline polyester, dihydric alcohols are preferred. Examples of dihydric alcohols 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 an unsaturated double bond 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.

[0059] The weight average molecular weight Mw of the crystalline polyester is preferably from 5000 to 50000. The number average molecular weight Mn of the crystalline polyester is preferably from 2000 to 10000. When the weight average molecular weight Mw and the number average molecular weight Mn of the crystalline polyester are within the above ranges, the low-temperature fixing property is improved.

[0060] The content of the other resin is preferably from 0% by mass to 40% by mass, more preferably from 0% by mass to 30% by mass, based on the total mass of the binder resin.

[0061] 1-1-2. Release agent The release agent can enhance the releasability of the toner from the fixing member and the like. Further, as described above, in the present embodiment, the release agent is dispersed in the binder resin and can sufficiently plasticize the toner during heat fixing of the toner. The release agent is preferably a wax.

[0062] Examples of the release agent which is a wax include hydrocarbon waxes, dialkyl ketone waxes, fatty acid ester waxes, amide waxes and the like. Examples of hydrocarbon waxes include polyethylene wax, paraffin wax, microcrystalline wax, and Fischer-Tropsch wax. Examples of dialkyl ketone waxes include distearyl ketone. Examples of fatty acid ester waxes include carnauba wax, montan wax, behenic acid behenate, behenyl behenate, trimethylolpropane tribehenate, pentaerythritol tetramyristate, pentaerythritol tetrastearate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecanediol distearate, trimellitic acid tristearyl, and distearyl maleate. Examples of amide waxes include ethylenediamine dibehenylamide, and trimellitic acid tristearylamide.

[0063] Among these, from the viewpoint of further enhancing the low-temperature fixability, the release agent is preferably a hydrocarbon wax or a fatty acid ester wax, and more preferably a fatty acid ester wax. Thereby, since the release agent can be more finely dispersed in the binder resin, the toner base particles can be more sufficiently plasticized, and the low-temperature fixability can be further enhanced.

[0064] The content of the release agent is preferably 1% by mass to 25% by mass, and more preferably 5% by mass to 20% by mass with respect to the total mass of the toner base particles. When the content of the release agent is 1% by mass or more, the toner can be more easily softened during heat fixing of the toner, so that the low-temperature fixability can be easily enhanced. When the content of the release agent is 25% by mass or less, a sufficient amount of binder resin can be contained in the toner base particles, so that the fixability of the image is likely to be enhanced.

[0065] 1-1-3. Other Components The toner base particles may contain a colorant, a charge control agent, an aggregating agent, and the like.

[0066] The colorant may be a dye or a pigment. When the toner is a colored toner that imparts a predetermined color tone to the image, the toner base particles may contain a colorant such as yellow, magenta, cyan, or black according to the color tone to be exhibited by the colored toner. The colorant may be contained in the toner base particles alone or in combination of a plurality of types.

[0067] Examples of the yellow colorant include yellow dyes and yellow pigments. Examples of the yellow dye include C.I. Solvent Yellow 19, 44, 77, 79, 81, 82, 93, 98, 103, 104, 112, and 162. Examples of the yellow pigment include C.I. Pigment Yellow 14, 17, 74, 93, 94, 138, 155, 180, and 185.

[0068] Examples of magenta colorants include magenta dyes and magenta pigments. Examples of magenta dyes include C.I. Solvent Red 1, 49, 52, 58, 63, 111, and 122. Examples of magenta pigments include C.I. Pigment Red 5, 48:1, 53:1, 57:1, 122, 139, 144, 149, 166, 177, 178, and 222.

[0069] Examples of cyan colorants 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.

[0070] Examples of black colorants include carbon blacks such as channel black, furnace black, acetylene black, thermal black, and lamp black, magnetic substances such as ferrite and magnetite, and iron-titanium composite oxides.

[0071] The content of the colorant is preferably 0.5% by mass to 20% by mass, more preferably 2% by mass to 10% by mass, based on the total mass of the toner base particles. When the toner is a clear toner, it is preferable that the toner base particles substantially do not contain a colorant, and the content of the colorant based on the total mass of the toner base particles is preferably 0.1% by mass or less.

[0072] The charge control agent can easily adjust the chargeability of the toner base particles.

[0073] 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, metal salts of salicylic acid or metal complexes thereof.

[0074] The content of the charge control agent is preferably 0.1% by mass to 10% by mass, more preferably 0.5% by mass to 5% by mass, based on the total mass of the binder resin. Note that if an attempt is made to control the chargeability of the toner by methods such as adding an excessive amount of the charge control agent, other properties of the toner base particles may change significantly. In contrast, in the present embodiment, by adjusting the chargeability of the toner with strontium titanate, the chargeability of the toner can be adjusted to a desired level while satisfying other required properties.

[0075] By adding the aggregating agent to a binder resin particle dispersion (a mixed liquid further containing a mold release agent particle dispersion and / or a colorant particle dispersion as necessary), the particles can be aggregated, making it easier for the particles to fuse with each other.

[0076] Examples of the aggregating agent include sodium chloride, potassium chloride, lithium chloride, calcium chloride, magnesium chloride, zinc chloride, polyaluminum chloride, copper sulfate, magnesium sulfate, manganese sulfate, aluminum sulfate, and the like. These aggregating agents can be used alone or in combination of two or more.

[0077] The content of the aggregating agent is preferably 2% by mass to 30% by mass, more preferably 3% by mass to 20% by mass, from the viewpoint of controlling the particle size of the toner, based on the solid content of the binder resin constituting the toner particles.

[0078] 1-2. Externally added agent The toner base particles may contain an externally added agent added as a post-treatment agent to the surface of the toner base particles in order to enhance the fluidity, chargeability, and cleanability of the toner.

[0079] The external additive preferably contains inorganic particles such as silica particles, alumina particles, zirconia particles, titanium oxide particles, strontium titanate 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 inorganic particles may be hydrophobically treated with a surface treatment agent such as a silane coupling agent or silicone oil, if necessary.

[0080] The particle size of the inorganic particles preferably has a number average primary particle size of 10 nm to 200 nm, more preferably 20 nm to 150 nm. The number average primary particle size of the external additive can be measured by a scanning electron microscope (SEM). Specifically, the image data of the inorganic particles captured by SEM can be binarized using an image processing and analysis device (LUZEX AP, manufactured by Nireco Corporation), and the average value of the horizontal Feret diameters measured for 100 particles can be used.

[0081] The external additive may also contain organic particles including homopolymers such as styrene and methyl methacrylate, and copolymers thereof. The particle size of the organic particles preferably has a peak top particle size of 10 nm to 1000 nm, measured by the same method as for strontium titanate.

[0082] The external additive may also contain a lubricant such as a metal salt of a higher fatty acid. Examples of the higher fatty acid include stearic acid, oleic acid, palmitic acid, linoleic acid, and ricinoleic acid. Examples of the metal constituting the metal salt include zinc, manganese, aluminum, iron, copper, magnesium, and calcium.

[0083] The content of the external additive is preferably 0.05% by mass to 5.00% by mass, more preferably 0.10% by mass to 3.00% by mass, based on the total mass of the toner.

[0084] 1-3. Method for manufacturing toner The toner can be manufactured by methods such as the pulverization method, the emulsion polymerization aggregation method, the emulsion aggregation method, the suspension polymerization method, and the dissolution suspension method. Among these, the pulverization method, the emulsion polymerization aggregation method, and the suspension polymerization method are preferred, and from the viewpoints of the uniformity of the particle diameter and the controllability of the shape, the emulsion polymerization aggregation method is more preferred.

[0085] The emulsion polymerization aggregation method is a method of manufacturing toner by performing a step of preparing a binder resin particle dispersion liquid, a step of preparing a release agent particle dispersion liquid as necessary, and a step of preparing a colorant particle dispersion liquid, mixing the obtained respective dispersion liquids, and aggregating them until a predetermined particle diameter is obtained. Hereinafter, the method of manufacturing toner by the emulsion polymerization aggregation method will be described.

[0086] 1-3-1. Step of preparing a binder resin particle dispersion liquid In this step, a dispersion liquid of binder resin particles containing the polymer is prepared.

[0087] This step may be a step of creating a binder resin particle dispersion liquid from a commercially available product of the polymer. This step may be a step of introducing a functional group contained in the first functional group group to the molecular end of the main chain of a commercially available polymer to create a binder resin particle dispersion liquid. This step may be a step separately including a step of obtaining the polymer by polymerization of a vinyl monomer and a step of creating a particle dispersion liquid. This step may be a step of creating a particle dispersion liquid by performing the polymerization of a vinyl monomer in a poor solvent such as an aqueous medium.

[0088] For example, a mode of preparing a dispersion liquid of binder resin particles through (i) a step of preparing an aqueous medium containing a chain transfer agent having at least one kind of functional group selected from the group consisting of an alicyclic alkyl group having 5 or more carbon atoms, a branched alkyl group having 4 or more carbon atoms, a linear alkyl group having 10 or more carbon atoms, a hydroxy group, and a carboxy group and / or a polymerization initiator having the functional group, and (ii) a step of polymerizing a vinyl monomer in the prepared aqueous medium to produce a dispersion liquid of particles of the binder resin is also preferably used.

[0089] In addition, in this specification, the "aqueous medium" refers to a solvent containing at least 50% by mass or more of water. Examples of components other than water in the aqueous medium include methanol, ethanol, isopropanol, acetone, dimethylformamide, methyl cellosolve, tetrahydrofuran, and the like.

[0090] The method for introducing the functional group contained in the first functional group into the polymer is not limited to the above method, and known polymer terminal functionalization methods such as the method using a RAFT agent having the functional group contained in the first functional group can be used.

[0091] As the chain transfer agent, a known chain transfer agent can be used. Examples of the chain transfer agent not containing the functional group include n-octyl mercaptan, n-octyl-3-mercaptopropionate, and the like. Examples of the chain transfer agent containing the functional group include thiol compounds having the functional group, thioketone compounds, thioester compounds, thionoester compounds, dithioester compounds, and the like.

[0092] As the polymerization initiator, a known polymerization initiator can be used. Examples of the polymerization initiator not containing the functional group include persulfates such as potassium persulfate and ammonium persulfate, azobisaminodipropanoate, azobiscyanovaleric acid and its salts, hydrogen peroxide, and the like. Examples of the polymerization initiator containing the functional group include diazo compounds having the functional group, peroxides, and the like.

[0093] From the viewpoint of enhancing the dispersibility of the oil droplets, a surfactant may be preliminarily contained in the aqueous medium. Examples of the surfactant include anionic surfactants such as sodium polyoxyethylene(2) dodecyl ether sulfate, sodium dodecyl sulfate, and sodium dodecylbenzenesulfonate.

[0094] When the functional group is included in the chain transfer agent, from the viewpoint of facilitating the adjustment of the molecular weight and the introduction rate of the functional group to the molecular end, the added mass of the chain transfer agent is preferably 0.4 mol% to 10 mol%, more preferably 0.8 mol% to 7 mol%, based on the total number of moles of the vinyl monomer.

[0095] The polymerization temperature is preferably in the range of 50°C to 100°C, more preferably 55°C to 90°C. Also, the polymerization time is preferably 1 hour to 12 hours.

[0096] The volume-based median diameter of the binder resin particles in the binder resin particle dispersion liquid obtained in this step is preferably 30 nm to 300 nm, more preferably 50 nm to 250 nm, and even more preferably 100 nm to 200 nm. The median diameter can be measured using "Microtrac UPA-150" (manufactured by Nikkiso Co., Ltd.).

[0097] In this step, a release agent may be added to the aqueous medium together with the monomer.

[0098] 1-3-2. Step of preparing a release agent particle dispersion liquid In this step, a release agent is added to the aqueous medium and dispersed into particles to prepare a release agent particle dispersion liquid.

[0099] The method of dispersing the release agent into particles is not particularly limited. For example, the release agent can be dispersed using a homogenizer.

[0100] The volume-based median diameter of the release agent particles in the release agent particle dispersion liquid obtained in this step is preferably 100 nm to 1000 nm, more preferably 200 nm to 700 nm. The median diameter of the release agent particles can be measured using a laser diffraction particle size distribution analyzer (LA-750, manufactured by Horiba, Ltd.).

[0101] 1-3-3. Step of preparing a colorant particle dispersion liquid In this process, a colorant is introduced into an aqueous medium and dispersed in particulate form to prepare a colorant particle dispersion liquid.

[0102] The method of dispersing the colorant in particulate form is not particularly limited. For example, a homogenizer can be used to disperse the colorant.

[0103] The median diameter of the colorant particles in the colorant particle dispersion liquid obtained in this process is preferably from 50 nm to 300 nm, more preferably from 50 nm to 200 nm, based on the volume of the colorant particles. The median diameter of the colorant particles can be measured using "Microtrac UPA-150" (manufactured by Nikkiso Co., Ltd.).

[0104] 1-3-4. Step of aggregating resin particles In this process, a flocculant is added to a binder resin particle dispersion liquid (a mixed liquid further added with a release agent particle dispersion liquid and a colorant particle dispersion liquid as necessary), and the particles are aggregated and fused together while heating and stirring.

[0105] Examples of the flocculant include sodium chloride, potassium chloride, lithium chloride, calcium chloride, magnesium chloride, zinc chloride, polyaluminum chloride, copper sulfate, magnesium sulfate, manganese sulfate, aluminum sulfate, etc. These flocculants can be used alone or in combination of two or more.

[0106] The amount of the flocculant used is not particularly limited, but from the viewpoint of controlling the particle size of the toner, it is preferably from 2% by mass to 30% by mass, more preferably from 3% by mass to 20% by mass, based on the solid content of the binder resin constituting the toner particles.

[0107] In this process, after adding the flocculant, it is preferable to rapidly increase the temperature by heating, and the rate of temperature increase is preferably 0.05 °C / min or more. The upper limit of the rate of temperature increase is not particularly limited, but from the viewpoint of suppressing the generation of coarse particles due to the rapid progress of fusion, it is preferably 15 °C / min or less. Further, after the dispersion for flocculation reaches the desired temperature, it is preferable to keep the temperature of the dispersion for flocculation for a certain period of time, preferably until the volume-based median diameter becomes 4.5 μm to 7.0 μm, and continue the fusion.

[0108] After this process, the aggregated particles obtained in this process are aged as necessary, and a toner can be obtained by performing a washing and filtration process, a drying process, and an external additive addition process as necessary.

[0109] 1-3-5. Aging Process In this process, the dispersion in which the aggregated particles are dispersed is heated and stirred, and an aging treatment is performed by adjusting the heating temperature, stirring speed, heating time, etc. until the shape of the aggregated particles reaches the desired circularity. The aging treatment is performed as necessary.

[0110] 1-3-6. Washing and Filtration Process In this process, the toner particles are separated from the dispersion of the toner particles by solid-liquid separation, and the deposits such as surfactants and flocculants are removed and washed from the toner cake (an aggregate obtained by aggregating wet toner particles into a cake shape) obtained by the solid-liquid separation.

[0111] The method of solid-liquid separation is not particularly limited, and examples include a centrifugal separation method, a vacuum filtration method using a Nutsche, etc., and a filtration method using a filter press, etc.

[0112] 1-3-7. Drying Process In this process, the washed toner cake is dried. The drying method is not particularly limited, and examples include a flash jet dryer, a spray dryer, a vacuum freeze dryer, a vacuum dryer, etc.

[0113] 1-3-8. Addition of External Additive This process is carried out as necessary when adding an external additive to toner particles.

[0114] As a mixing device for the external additive, mechanical mixing devices such as a Henschel mixer, a coffee mill, and a sample mill can be used.

[0115] 1-4. Carrier The carrier is mixed with the above-described toner base particles to form a two-component magnetic toner. The carrier may be any known magnetic particles that can be contained in the toner.

[0116] Examples of the magnetic particles include particles containing magnetic substances such as iron, steel, nickel, cobalt, ferrite, and magnetite, and alloys thereof with aluminum and lead. The carrier may be a coated carrier in which the surface of the particles made of the magnetic substance is coated with a resin or the like, or a resin-dispersed carrier in which the magnetic substance is dispersed in a binder resin. Examples of the resin for coating include olefin resins, styrene resins, styrene-acrylic resins, silicone resins, polyester resins, and fluororesins. Examples of the binder resin include acrylic resins, styrene-acrylic resins, polyester resins, fluororesins, and phenol resins.

[0117] The average particle diameter of the carrier preferably has an average particle diameter based on volume of 20 μm to 100 μm, and more preferably 25 μm to 80 μm. The average particle diameter of the carrier can be measured by HELOS manufactured by SYMPATEC, a laser diffraction particle size distribution measuring device equipped with a wet disperser.

[0118] The content of the carrier is preferably 2% by mass to 10% by mass based on the total mass of the toner base particles and the carrier.

[0119] 2. Image Forming Method and Image Forming Apparatus The image forming method according to this embodiment includes a step of attaching toner for developing an electrostatic latent image to a recording medium, and a step of fixing the attached toner for developing an electrostatic latent image to the recording medium.

[0120] Further, the image forming apparatus according to this embodiment includes a toner image forming unit that develops an electrostatic latent image with toner to form a toner image, and a fixing device that fixes the toner image to a recording medium by transferring the toner image to the recording medium. In this embodiment, the fixing device fixes the above-described toner to the recording medium.

[0121] The image forming apparatus may be a four-cycle type image forming apparatus configured by four color developing devices of yellow, magenta, cyan, and black, and one electrophotographic photoreceptor. Further, the image forming apparatus may be a tandem type image forming apparatus configured by four color developing devices of yellow, magenta, cyan, and black, and four electrophotographic photoreceptors provided for each color.

[0122] FIG. 1 is a schematic configuration diagram showing an example of an image forming apparatus 1 according to this embodiment. The image forming apparatus 1 shown in FIG. 1 includes an image processing unit 30, an image forming unit 40, a paper conveyance unit 50, a fixing device 60, and an image reading unit 70.

[0123] The image forming unit 40 includes image forming units 41Y, 41M, 41C, and 41K that form images with respective color toners of Y (yellow), M (magenta), C (cyan), and K (black). Since these have the same configuration except for the toner to be accommodated, the symbols representing colors may be omitted hereinafter. The image forming unit 40 further includes an intermediate transfer unit 42 and a secondary transfer unit 43. These correspond to transfer devices.

[0124] The image forming unit 41 includes an exposure device 411, a developing device 412, an electrophotographic photosensitive member (image carrier) 413, a charging device 414, and a drum cleaning device 415. The charging device 414 is, for example, a corona charger. The charging device 414 may be a contact charging device that brings a contact charging member such as a charging roller, a charging brush, or a charging blade into contact with the electrophotographic photosensitive member 413 to charge it. The exposure device 411 includes, for example, a semiconductor laser as a light source and a light deflector (polygon motor) that irradiates the electrophotographic photosensitive member 413 with laser light corresponding to the image to be formed. The electrophotographic photosensitive member 413 is a negatively charged organic photosensitive member having photoconductivity. The electrophotographic photosensitive member 413 is charged by the charging device 414.

[0125] The developing device 412 is a developing device using the two-component development method. The developing device 412 includes, for example, a developing container, a developing roller (magnetic roller), a partition wall, a conveying roller, and a stirring roller. The developing container stores the two-component developer. The developing roller (magnetic roller) is rotatably disposed at the opening of the developing container. The partition wall partitions the inside of the developing container so that the two-component developer can communicate. The conveying roller conveys the two-component developer on the opening side of the developing container toward the developing roller. The stirring roller stirs the two-component developer in the developing container. For example, a two-component developer is stored in the developing container.

[0126] The intermediate transfer unit 42 includes an intermediate transfer belt (intermediate transfer member) 421, a primary transfer roller 422, a plurality of support rollers 423 including a backup roller 423A, and a belt cleaning device 426. The primary transfer roller 422 presses the intermediate transfer belt 421 against the electrophotographic photosensitive member 413. The intermediate transfer belt 421 is looped around a plurality of support rollers 423. When at least one driving roller among the plurality of support rollers 423 rotates, the intermediate transfer belt 421 travels at a constant speed in the direction of arrow A.

[0127] The belt cleaning device 426 has an elastic member 426a. The elastic member 426a abuts against the intermediate transfer belt 421 after secondary transfer and removes the deposits on the surface of the intermediate transfer belt 421. The elastic member 426a is composed of an elastic body and includes a cleaning blade, a brush, etc.

[0128] The secondary transfer unit 43 has an endless secondary transfer belt 432 and a plurality of support rollers 431 including a secondary transfer roller 431A. The secondary transfer belt 432 is looped by the secondary transfer roller 431A and the support rollers 431.

[0129] The fixing device 60 has, for example, a fixing roller 62, a heating belt 10, and a pressure roller 63. The heating belt 10 covers the outer peripheral surface of the fixing roller 62 and heats and melts the toner constituting the toner image on the paper S. The pressure roller 63 presses the paper S toward the fixing roller 62 and the heating belt 10. The paper S corresponds to a recording medium.

[0130] The image forming apparatus 1 further has an image reading unit 70, an image processing unit 30, and a paper conveyance unit 50. The image reading unit 70 has a paper feeding device 71 and a scanner 72. The paper conveyance unit 50 has a paper feeding unit 51, a paper discharging unit 52, and a conveyance path unit 53. Papers S (standard papers, special papers) identified based on basis weight, size, etc. are stored in three paper feeding tray units 51a to 51c constituting the paper feeding unit 51 for each preset type. The conveyance path unit 53 has a plurality of conveyance roller pairs such as a registration roller pair 53a.

[0131] The formation of an image by the image forming apparatus 1 will be described. The scanner 72 optically scans and reads the document D on the contact glass. The reflected light from the document D is read by the CCD sensor 72a and becomes input image data. The input image data is subjected to predetermined image processing in the image processing unit 30 and sent to the exposure device 411.

[0132] The electrophotographic photoreceptor 413 rotates at a constant peripheral speed. The charging device 414 uniformly charges the surface of the electrophotographic photoreceptor 413 negatively. In the exposure device 411, the polygon mirror of the polygon motor rotates at high speed, and the laser light corresponding to the input image data of each color component is developed along the axial direction of the electrophotographic photoreceptor 413 and irradiated onto the outer peripheral surface of the electrophotographic photoreceptor 413 along the axial direction. Thus, an electrostatic latent image is formed on the surface of the electrophotographic photoreceptor 413.

[0133] In the developing device 412, the toner mother particles are charged by stirring and transporting the two-component developer in the developing container, and the two-component developer is transported to the developing roller to form a magnetic brush on the surface of the developing roller. The charged toner mother particles electrostatically adhere from the magnetic brush to the portion of the electrostatic latent image on the electrophotographic photoreceptor 413. Thus, the electrostatic latent image on the surface of the electrophotographic photoreceptor 413 is visualized, and a toner image corresponding to the electrostatic latent image is formed on the surface of the electrophotographic photoreceptor 413. Note that the "toner image" refers to a collection of toners in an image shape.

[0134] The toner image on the surface of the electrophotographic photoreceptor 413 is transferred to the intermediate transfer belt 421 by the intermediate transfer unit 42. The transfer residual toner remaining on the surface of the electrophotographic photoreceptor 413 after transfer is removed by the drum cleaning device 415 having a drum cleaning blade that is in sliding contact with the surface of the electrophotographic photoreceptor 413.

[0135] When the intermediate transfer belt 421 is pressed against the electrophotographic photoreceptor 413 by the primary transfer roller 422, a primary transfer nip is formed for each electrophotographic photoreceptor by the electrophotographic photoreceptor 413 and the intermediate transfer belt 421. In the primary transfer nip, the toner images of each color are sequentially overlapped and transferred to the intermediate transfer belt 421.

[0136] On one hand, the secondary transfer roller 431A is pressed against the backup roller 423A via the intermediate transfer belt 421 and the secondary transfer belt 432. Thereby, a secondary transfer nip is formed by the intermediate transfer belt 421 and the secondary transfer belt 432. The sheet S passes through the secondary transfer nip. The sheet S is conveyed to the secondary transfer nip by the sheet conveyance unit 50. Correction of the inclination of the sheet S and adjustment of the conveyance timing are performed by the registration roller unit provided with the registration roller pair 53a.

[0137] When the sheet S is conveyed to the secondary transfer nip, a transfer bias is applied to the secondary transfer roller 431A. By applying this transfer bias, the toner image carried on the intermediate transfer belt 421 is transferred to the sheet S (the step of attaching the toner for electrostatic charge image development to the recording medium). The sheet S on which the toner image has been transferred is conveyed toward the fixing device 60 by the secondary transfer belt 432.

[0138] Adherents such as residual transfer toner remaining on the surface of the intermediate transfer belt 421 after secondary transfer are removed by the belt cleaning device 426 having a cleaning blade that is in sliding contact with the surface of the intermediate transfer belt 421. At this time, since the above-described intermediate transfer body is used as the intermediate transfer belt, the dynamic frictional force can be reduced over time.

[0139] The fixing device 60 sandwiches the heating belt 10 between the rotating fixing roller 62 and the pressure roller 63 to form a fixing nip, and heats and presses the conveyed sheet S at the fixing nip portion. In this way, the toner image is fixed to the sheet S (the step of fixing the toner for electrostatic charge image development to the recording medium). The sheet S on which the toner image has been fixed is discharged outside the machine by the discharging unit 52 provided with the discharging roller 52a.

Example

[0140] Hereinafter, the present invention will be described with reference to the examples. The scope of the present invention is not limitedly interpreted by the examples.

[0141] [Manufacture of Toner 1] <Preparation of Binder Resin Particle Dispersion 1> A 5L stainless steel kettle (SUS kettle) equipped with a stirring device, a temperature sensor, a cooling pipe, and a nitrogen introduction device was charged with a surfactant solution prepared by dissolving 8 g of sodium dodecyl sulfate in 3 L of ion-exchanged water. While stirring this surfactant solution at a stirring speed of 230 rpm under a nitrogen stream, the liquid temperature was raised to 80°C. Then, an initiator solution prepared by dissolving 10 g of potassium persulfate in 200 g of ion-exchanged water was added to this surfactant solution. After setting the temperature to 80°C, the following monomer mixture was added dropwise over 100 minutes. Then, the mixture after the monomer mixture was added dropwise was heated and stirred at 80°C for 2 hours to carry out polymerization, and binder resin particle dispersion 1 was prepared. The median diameter of the binder resin particles in the obtained binder resin particle dispersion 1 based on volume was 115 nm. Also, the number average molecular weight Mn of the polymer contained in the binder resin was 7400.

[0142] -Monomer Mixture- Isobornyl acrylate 370 g Styrene (St) 123 g n-Butyl acrylate (nBA) 297 g Methacrylic acid (MAA) 46 g tert-Dodecyl mercaptan 12.4 g

[0143] The median diameter of the binder resin particles in the above-mentioned binder resin particle dispersion 1 based on volume was measured by the dynamic light scattering method using "Microtrac UPA-150" (manufactured by Nikkiso Co., Ltd.).

[0144] The molecular weight was measured using the apparatus "HLC-8220" (manufactured by Tosoh Corporation) and the column "TSKguardcolumn+TSKgel SuperHZM-M3 series" (manufactured by Tosoh Corporation). While maintaining the column temperature at 40°C, tetrahydrofuran (THF) was flowed as the carrier solvent at a flow rate of 0.2 ml / min. The measurement sample was dissolved in tetrahydrofuran to a concentration of 1 mg / ml under dissolution conditions where it was treated for 5 minutes using an ultrasonic disperser at room temperature (25°C). Subsequently, it was treated with a membrane filter having a pore size of 0.2 μm to obtain a sample solution. 10 μl of this sample solution was injected into the apparatus together with the above-mentioned carrier solvent, and detected using a refractive index detector (RI detector), and the number average molecular weight Mn was measured as a polystyrene equivalent value.

[0145] <Preparation of Colorant Particle Dispersion Liquid 1> The following colorant mixture was dispersed using an SC mill to obtain a colorant particle dispersion liquid 1. The volume-based median diameter of the colorant particles in the colorant particle dispersion liquid 1 was 155 nm.

[0146] -Colorant Mixture- Colorant: 10 parts by mass of carbon black 20% anionic surfactant: 1.5 parts by mass Ion-exchanged water: 90 parts by mass For the colorant, carbon black (Mogul (registered trademark) L, manufactured by Cabot Corporation) was used. For the 20% anionic surfactant, a 20% aqueous solution of sodium dodecylbenzenesulfonate was used.

[0147] The volume-based median diameter of the colorant particles in the above-mentioned colorant particle dispersion liquid 1 was measured by the dynamic light scattering method using "Microtrac UPA-150" (manufactured by Nikkiso Co., Ltd.).

[0148] <Preparation of Release Agent Particle Dispersion Liquid 1> The following mold release agent mixture was dispersed in a round stainless steel flask for 10 minutes using a homogenizer "Ultra Turrax (registered trademark) T50" (manufactured by IKA Corporation), and then subjected to dispersion treatment with a pressure discharge type homogenizer to obtain a mold release agent particle dispersion liquid 1. The median diameter of the mold release agent particles in the mold release agent particle dispersion liquid 1 based on volume was 530 nm.

[0149] - Mold release agent mixture - Behenyl behenate 100 parts by mass Sodium dodecyl sulfate 5 parts by mass Ion-exchanged water 240 parts by mass

[0150] The median diameter of the mold release agent particles in the mold release agent particle dispersion liquid 1 based on volume was measured by a laser diffraction particle size distribution analyzer LA-750 (manufactured by Horiba, Ltd.).

[0151] <Preparation of toner mother particle dispersion liquid 1> The following dispersion liquid mixture was mixed and dispersed in a round stainless steel flask using a homogenizer "Ultra Turrax (registered trademark) T50" (manufactured by IKA), and then heated to 55 °C while stirring the inside of the flask in an oil bath for heating. After holding at 55 °C for 30 minutes, it was confirmed that aggregated particles with a median diameter (D50) of 4.8 μm based on volume were generated in the solution. Further, when the temperature of the oil bath for heating was raised and held at 56 °C for 2 hours, the median diameter (D50) based on volume became 5.9 μm.

[0152] Thereafter, 1 mol / L sodium hydroxide was added to the system to adjust the pH of the system to 5.0 at 56 °C, and then the round stainless steel flask was sealed using a magnetic seal and heated to 98 °C while continuing stirring. By continuing stirring for 6 hours, the fusion (agglomeration) between the binder resin particles was completed, and toner mother particle dispersion liquid 1 was prepared. The median diameter (D50) of the toner mother particles in the toner mother particle dispersion liquid 1 based on volume was 6.1 μm.

[0153] - Dispersion liquid mixture - Binder resin particle dispersion liquid 1 237 parts by mass 142 parts by mass of the colorant particle dispersion liquid 118 parts by mass of the mold release agent particle dispersion liquid 1.8 parts by mass of aluminum polychloride 600 parts by mass of ion-exchanged water

[0154] The median diameter of the toner base particles on a volume basis was measured using a particle size measuring device (Microtrac UPA-150, manufactured by Nikkiso Co., Ltd.).

[0155] <Washing and drying process> The toner base particle dispersion liquid 1 was subjected to solid-liquid separation using a basket-type centrifuge "MARKIII Model Number 60×40" (manufactured by Matsumoto Machinery Sales Co., Ltd.) to form a wet cake of the toner base particles.

[0156] The wet cake was washed with ion-exchanged water at 45°C using the above-mentioned basket-type centrifuge until the electrical conductivity of the filtrate reached 5 μS / cm. Then, it was transferred to a "Flash Jet Dryer" (manufactured by Seishin Enterprise Co., Ltd.) and dried until the moisture content became 0.5% by mass to obtain toner base particles.

[0157] <External additive treatment of toner base particles> To 100 parts by mass of the toner base particles obtained above, 1 part by mass of hydrophobic silica (number average primary particle diameter = 12 nm) and 0.3 part by mass of hydrophobic titania (number average primary particle diameter = 20 nm) were added. Then, it was mixed using a Henschel mixer (registered trademark) to perform an external additive treatment to produce Toner 1.

[0158] [Production of Toners 2 to 22] The monomer composition of the monomer mixture of Toner 1 was changed as shown in Table 1, tert-dodecyl mercaptan was changed to a thiol compound containing the functional groups shown in Table 2, and Toners 2 to 22 were produced in the same manner as the production method of Toner 1 except that the number average molecular weight was adjusted to be as shown in Table 2.

[0159]

Table 1

[0160] [Table 2]

[0161] [Evaluation] Using a two-component developer, the following evaluation items were evaluated. The evaluation results are as shown in Table 3 below.

[0162] (1) Fold fixing property at low temperature (low-temperature fixing property) Toner 1 to 22 were sequentially loaded into a multi-functional machine (bizhub PRO (registered trademark) C6500, manufactured by Konica Minolta, Inc.). The surface temperature of the fixing heating member using the heat roll fixing method was set to 150 °C, and image formation was performed using thick paper with a basis weight of 350 g / m2 as the recording medium in an environment of normal temperature and normal humidity (temperature 20 °C, relative humidity 50% RH), and a solid image with 5 g / m3 of toner fixed was obtained as a visible image.

[0163] After that, the obtained solid image was folded using a folding machine, air with a pressure of 0.40 MPa was blown onto it, the state of the fold was observed, and the fold fixing property was evaluated according to the following criteria. In this evaluation, a rank of 3 or higher was considered a pass.

[0164] Rank 5: No peeling was confirmed near the fold Rank 4: Slight peeling along the fold was slightly confirmed Rank 3: Partial peeling along the fold was confirmed Rank 2: Thin linear peeling along the fold was confirmed Rank 1: Thick linear peeling along the fold was confirmed

[0165] (2) Heat-resistant storage stability 0.5 g of toner 1 was placed in a 10 mL glass bottle with an inner diameter of 21 mm, the lid was closed, and it was shaken 600 times at room temperature with a "Tap Denser KYT - 2000" (manufactured by Seishin Enterprise Co., Ltd.). Then, with the lid removed, it was left in an environment of 55 °C and 35% RH for 2 hours.

[0166] Next, the toner 1 after standing was placed on a 48 - mesh (aperture diameter 350 μm) sieve, taking care not to crush the toner aggregates. Then, the toner was set in a powder tester (manufactured by Hosokawa Micron Corporation), fixed with a pressing bar and a knob nut, adjusted to a vibration intensity with a feed width of 1 mm, and vibrated for 10 seconds. Subsequently, the amount of toner remaining on the sieve was measured, and the toner aggregation rate was calculated by dividing the measured amount of toner by the initial weight (0.5 g) of the toner. For the toner aggregation rate, the heat - resistant storage property was evaluated according to the following evaluation criteria. The heat - resistant storage properties of toners 2 to 22 were also evaluated in the same manner.

[0167] 4: Toner aggregation rate is less than 15% by mass (the heat - resistant storage property of the developer is extremely good) 3: Toner aggregation rate is 15% by mass or more and less than 20% by mass (the heat - resistant storage property of the developer is good) 2: Toner aggregation rate is 20% by mass or more and less than 25% by mass (the heat - resistant storage property of the developer is slightly poor) 1: Toner aggregation rate is 25% by mass or more (the heat - resistant storage property of the developer is poor and it cannot be used)

[0168] Table 3 shows the evaluation results for each toner.

[0169]

Table 3

[0170] In Examples 1 to 20, the binder resin contains a polymer having a structural unit derived from a vinyl monomer and a number - average molecular weight Mn of 800 to 30000, and the polymer contains a polymer having a predetermined functional group at the molecular terminals of the main chain, and the low - temperature fixability and the heat - resistant storage property were good.

[0171] In addition, by setting the number average molecular weight Mn of the polymer to 800 to 20,000, the low-temperature fixing property is further enhanced. It has been found that by setting the number average molecular weight Mn of the polymer to 800 to 8,000, the low-temperature fixing property is further enhanced.

[0172] In addition, it has been found that the heat resistance is further enhanced by including a polymer having at least one functional group selected from the group consisting of an adamantyl group, a cyclohexyl group, a carboxyalkyl group having a linear alkylene group with 1 to 8 carbon atoms, a carboxyalkyl group having a branched alkylene group with 1 to 8 carbon atoms, and a carboxyalkyl group having an alicyclic alkyl group with 5 or more carbon atoms at the molecular terminal of the main chain.

Industrial Applicability

[0173] According to the toner for electrostatic charge image development of the present invention, the low-temperature fixing property can be sufficiently enhanced and the heat-resistant storage property can be made good. Therefore, the present invention is useful in the field of image formation.

Explanation of Signs

[0174] 1 Image forming apparatus 10 Heating belt 30 Image processing unit 40 Image forming unit 41Y, 41M, 41C, 41K Image forming unit 42 Intermediate transfer unit 43 Secondary transfer unit 50 Paper conveyance unit 51 Paper feeding unit 51a, 51b, 51c Paper feed tray unit 52 Paper discharge unit 52a Paper discharge roller 53 Conveyance path unit 53a Registration roller pair 60 Fixing device 62 Fixing roller 63 Pressing roller 70 Image reading unit 71 Paper feeding device 72 Scanner 72a CCD sensor 411 Exposure device 412 Developing device 413 Electro-photographic photoreceptor 414 Charging device 415 Drum cleaning device 421 Intermediate transfer belt 422 Primary transfer roller 423, 431 Support roller 423A Backup roller 426 Belt cleaning device 426a Elastic member 431A Secondary transfer roller 432 Secondary transfer belt D Document S Paper

Claims

1. A toner for developing an electrostatic charge image containing a binder resin in toner base particles, wherein the binder resin contains a polymer having a structural unit derived from a vinyl monomer, the number average molecular weight Mn of the polymer is 800 to 30,000, the polymer contains a polymer having at least one functional group selected from the group consisting of an alicyclic alkyl group having 5 or more carbon atoms, a branched alkyl group having 4 or more carbon atoms, a linear alkyl group having 10 or more carbon atoms, a hydroxy group, a hydroxyalkyl group, a carboxy group, and a carboxyalkyl group at a molecular terminal of the main chain, a toner for developing an electrostatic charge image.

2. the polymer contains a polymer having at least one functional group selected from the group consisting of an alicyclic alkyl group having 5 or more carbon atoms, a carboxy group, and a carboxyalkyl group at a molecular terminal of the main chain, the toner for developing an electrostatic charge image according to claim 1.

3. the polymer contains a polymer having at least one functional group selected from the group consisting of an adamantyl group, a cyclohexyl group, a carboxyalkyl group having a linear alkylene group having 1 to 8 carbon atoms, a carboxyalkyl group having a branched alkylene group having 1 to 8 carbon atoms, and a carboxyalkyl group having an alicyclic alkylene group having 5 or more carbon atoms at a molecular terminal of the main chain, the toner for developing an electrostatic charge image according to claim 2.

4. the number average molecular weight Mn of the polymer is 800 to 20,000, the toner for developing an electrostatic charge image according to claim 1.

5. the structural unit is a structural unit derived from at least one monomer selected from the group consisting of styrenes and (meth)acrylic acid esters, the toner for developing an electrostatic charge image according to claim 1.

6. the structural unit is a structural unit derived from at least one monomer selected from the group consisting of methoxystyrene, isobutyl (meth)acrylate, isobornyl (meth)acrylate, phenethyl (meth)acrylate, and methyl (meth)acrylate, the toner for developing an electrostatic charge image according to claim 5.

7. A method for producing a toner for developing an electrostatic charge image containing a binder resin in toner base particles, A step of preparing a particle dispersion of a binder resin containing a polymer having at least one functional group selected from the group consisting of an alicyclic alkyl group having 5 or more carbon atoms, a branched alkyl group having 4 or more carbon atoms, a linear alkyl group having 10 or more carbon atoms, a hydroxy group, a hydroxyalkyl group, a carboxy group, and a carboxyalkyl group at a molecular end of a main chain; A step of aggregating the particles of the binder resin and fusing the particles together in the particle dispersion of the binder resin; A method for producing a toner for electrostatic charge image development.

8. The step of preparing the particle dispersion of the binder resin is A step of preparing an aqueous medium containing a chain transfer agent having at least one functional group selected from the group consisting of an alicyclic alkyl group having 5 or more carbon atoms, a branched alkyl group having 4 or more carbon atoms, a linear alkyl group having 10 or more carbon atoms, a hydroxy group, and a carboxy group and / or a polymerization initiator having the functional group; A step of polymerizing a vinyl monomer in the prepared aqueous medium to produce the particle dispersion of the binder resin; The method for producing a toner for electrostatic charge image development according to claim 7.

9. A step of attaching the toner for electrostatic charge image development according to any one of claims 1 to 6 to a recording medium; A step of fixing the attached toner for electrostatic charge image development to the recording medium; An image forming method comprising:

Images