Patent Application
20240241460
The present disclosure relates to a toner to be used for developing an electrostatic latent image formed by a method, such as an electrophotographic method, an electrostatic recording method or a toner jet system recording method, to form a toner image.
Energy savings in an electrophotographic apparatus have hitherto been considered to be a large technical problem and hence a significant reduction in quantity of heat to be applied to a fixing device has been investigated. In particular, in a toner, there has been a growing need for so-called “low-temperature fixability” by which the toner can be fixed with lower energy.
A method including using a crystalline resin as a binder resin has been investigated as an approach to enabling fixation at low temperatures. The molecular chains of the crystalline resin are regularly arrayed and hence the resin has such a property as to be substantially free from softening at temperatures lower than its melting point. In addition, when the temperature of the crystalline resin exceeds the melting point, its crystal abruptly melts and an abrupt reduction in viscosity thereof along with the melting occurs. Accordingly, the crystalline resin has been attracting attention as a material that is excellent in sharp melt property and shows low-temperature fixability.
In Japanese Patent Application Laid-Open No. 2014-142632, there is a proposal of a toner characterized in that in the observation of a section of a toner particle, a sea-island structure, which includes a sea portion containing a crystalline resin as a main component and an island portion containing an amorphous resin as a main component, is observed. The toner described in Japanese Patent Application Laid-Open No. 2014-142632 enables fixation at low energy. However, the toner has a problem in that its island portion is liable to adversely affect the dispersion of a colorant such as a pigment to reduce its coloring power.
Meanwhile, in Japanese Patent Application Laid-Open No. 2017-049581, there is a proposal of the following toner: in a toner particle containing a binder resin, a pigment dispersant and a fixing aid, the structure of the adsorption moiety of the pigment dispersant, and a relationship between the hydrophobicity parameters of the pigment dispersant and the fixing aid are specified. The toner described in Japanese Patent Application Laid-Open No. 2017-049581 achieves both of low-temperature fixability and coloring power.
However, in case that a large amount of a crystalline resin has been introduced into a binder resin for further energy savings, even when the pigment dispersant disclosed in Japanese Patent Application Laid-Open No. 2017-049581 is used, its effect is limited. In case that a large amount of a crystalline resin has been introduced into a binder resin, the coloring power of a toner cannot be improved by the pigment dispersant disclosed in Japanese Patent Application Laid-Open No. 2017-049581. Accordingly, improvements in low-temperature fixability and coloring power of the toner have still been required.
The present disclosure provides such a toner that a pigment is dispersed in a toner particle containing a large amount of a crystalline resin, that is, a toner excellent in low-temperature fixability and coloring power.
The present disclosure relates to a toner including a toner particle containing a binder resin, a pigment and a pigment dispersant, wherein the binder resin contains 20.0% by mass or more and 100.0% by mass or less of a crystalline resin, wherein the pigment dispersant is a polymer containing a structure represented by the following formula (1) and a monomer unit represented by the following formula (2), wherein a content of the structure represented by the following formula (1) in the pigment dispersant is 1.0% by mass or more and 15.0% by mass or less, wherein a content of the monomer unit represented by the following formula (2) in the pigment dispersant is 45.0% by mass or more and 80.0% by mass or less, and wherein the pigment dispersant has a weight-average molecular weight (Mw) of 10,000 or more and 50,000 or less:
in the formula (1), X, Y and Z each independently represent one of —O—, a methylene group or —NR5— and R5 represents a hydrogen atom or a linear or branched alkyl group having 1 or more and 4 or less carbon atoms, L1 represents an ester bond or an amide bond, R1 represents a hydrogen atom or a methyl group, R2 represents an alkylene group having 2 or more and 4 or less carbon atoms, R4 represents a substituted or unsubstituted phenyl group, a polycyclic aromatic group or a heterocyclic group, and R3 represents a hydrogen atom, a substituted or unsubstituted phenyl group, an aralkyl group, a linear, branched or cyclic alkyl group having 1 or more and 18 or less carbon atoms or a monovalent group derived by substituting at least one of methylene groups of an alkyl group having 2 or more and 18 or less carbon atoms with an ether bond, an ester bond or an amide bond;
in the formula (2), R6 represents a hydrogen atom or a methyl group, L1 represents an ester bond or an amide bond, and “m” represents an integer of 20 or more and 30 or less.
Further features of the present disclosure will become apparent from the following description of exemplary embodiments.
The description “XX or more and YY or less” or “from XX to YY” representing a numerical range means a numerical range including a lower limit and an upper limit that are end points unless otherwise stated.
The present disclosure relates to a toner including a toner particle containing a binder resin, a pigment and a pigment dispersant,
in the formula (1), X, Y and Z each independently represent one of —O—, a methylene group or —NR5— and R5 represents a hydrogen atom or a linear or branched alkyl group having 1 or more and 4 or less carbon atoms, L1 represents an ester bond or an amide bond, R1 represents a hydrogen atom or a methyl group, R2 represents an alkylene group having 2 or more and 4 or less carbon atoms, R4 represents a substituted or unsubstituted phenyl group, a polycyclic aromatic group or a heterocyclic group, and R3 represents a hydrogen atom, a substituted or unsubstituted phenyl group, an aralkyl group, a linear, branched or cyclic alkyl group having 1 or more and 18 or less carbon atoms or a monovalent group derived by substituting at least one of methylene groups of an alkyl group having 2 or more and 18 or less carbon atoms with an ether bond, an ester bond or an amide bond;
in the formula (2), R6 represents a hydrogen atom or a methyl group, L1 represents an ester bond or an amide bond, and “m” represents an integer of 20 or more and 30 or less, and
The above-mentioned respective requirements are described in detail below.
The toner of the present disclosure is a toner including the toner particle containing the binder resin, which contains 20.0% by mass or more and 100.0% by mass or less of the crystalline resin, the pigment and the pigment dispersant.
The pigment dispersant is a polymer containing a structure represented by the formula (1) and a monomer unit represented by the formula (2).
In addition, the content of the structure represented by the formula (1) in the pigment dispersant is 1.0% by mass or more and 15.0% by mass or less and the content of the monomer unit represented by the formula (2) therein is 45.0% by mass or more and 80.0% by mass or less.
Further, the pigment dispersant has a weight-average molecular weight (Mw) of 10,000 or more and 50,000 or less. The requirements are as described above.
The inventors of the present disclosure have found that the satisfaction of the above-mentioned conditions provides a toner excellent in low-temperature fixability and coloring power. The inventors of the present disclosure have conceived a mechanism therefor to be as described below.
When the pigment is dispersed in the binder resin containing 20.0% by mass or more of the crystalline resin, design taking an interaction between the binder resin and the pigment dispersant into consideration is required. Specifically, there is a need to use a pigment dispersant having: a “moiety that interacts with the pigment,” the moiety being represented by the formula (1); and a “moiety that interacts with the crystalline resin,” the moiety containing the monomer unit represented by the formula (2).
In addition, it is required that the content of the structure represented by the formula (1) in the pigment dispersant be 1.0% by mass or more and 15.0% by mass or less and the content of the monomer unit represented by the formula (2) therein be 45.0% by mass or more and 80.0% by mass or less. The setting of the contents within the ranges can strike a balance between: the interaction between the pigment and the pigment dispersant; and the interaction between the pigment dispersant and the crystalline resin.
Herein, the structure represented by the formula (1) easily interacts with a functional group of the pigment because the structure expresses strong π-π interactivity and has a strong hydrogen bonding property. The incorporation of a regulated amount of the structure represented by the formula (1) enables the intervention of the pigment dispersant near the pigment. Meanwhile, the incorporation of a regulated amount of the monomer unit represented by the formula (2) improves the affinity of the pigment dispersant for the crystalline resin. Accordingly, even in the binder resin containing 20.0% by mass or more of the crystalline resin, the polymer chain of a polymer moiety derived from the monomer unit represented by the formula (2) can spread in the binder resin. In addition, the spread polymer chain expresses steric hindrance to suppress the aggregation of the molecules of the pigment. Thus, a toner excellent in low-temperature fixability and coloring power, which is an effect of this case, is obtained.
When the content of the structure represented by the formula (1) in the pigment dispersant is less than 1.0% by mass, the effect of the present disclosure is not obtained because the amount of the structure that interacts with the pigment is small and hence the pigment dispersant cannot intervene near the pigment. When the content of the structure represented by the formula (1) in the pigment dispersant is more than 15.0% by mass, the ratio of the structure represented by the formula (1) in the pigment dispersant becomes too large. As the result, the polymer chain (also referred to as “loop length”) of a polymer moiety between one of the structure represented by the formula (1) and another one of the structure represented by the formula (1) is not sufficient. Accordingly, steric hindrance for suppressing the aggregation of the molecules of the pigment is not obtained in the pigment dispersant Thus, the coloring power of the toner reduces.
When the content of the monomer unit represented by the formula (2) in the pigment dispersant is less than 45.0% by mass, the affinity of the pigment dispersant for the binder resin containing 20.0% or more of the crystalline resin is low and hence the polymer moiety shrinks. Accordingly, steric hindrance for suppressing the aggregation of the molecules of the pigment is not obtained. Thus, the coloring power of the toner reduces. In addition, the melting point of the pigment dispersant reduces and hence the heat-resistant storage stability of the toner deteriorates. When the content of the monomer unit represented by the formula (2) in the pigment dispersant is more than 80.0% by mass, the affinity of the pigment dispersant for the crystalline resin becomes so high that the pigment dispersant is taken in the binder resin and hence cannot intervene around the pigment. Thus, the coloring power of the toner reduces.
When the weight-average molecular weight (Mw) of the pigment dispersant is less than 10,000, steric hindrance of the pigment dispersant is not obtained and hence the pigment dispersant cannot suppress the aggregation of the molecules of the pigment. Thus, the coloring power of the toner reduces. In addition, crystallinity derived from a side-chain portion of the polymer moiety is not obtained. Accordingly, when the toner is produced, the pigment dispersant serves as a low-melting point component to deteriorate the heat resistance and storage stability of the toner. When the weight-average molecular weight (Mw) of the pigment dispersant is more than 50,000, an intermolecular interaction between the side-chain portion of the polymer moiety and the crystalline resin in the binder resin enlarges. As a result, the interaction becomes larger than the above-mentioned interaction between the structure represented by the formula (1) of the weight-average molecular weight and the pigment. Accordingly, the pigment dispersant is released from the pigment and is hence taken in the crystalline resin in the binder resin. Thus, the effect of the present disclosure is not obtained and hence the coloring power of the toner reduces. In order that the pigment dispersant of the present disclosure may exhibit its effect in the binder resin containing a large amount of the crystalline resin, a balance between the content of the structure represented by the formula (1) or the formula (2) in the pigment dispersant and the molecular weight thereof is important.
Details about the structure represented by the formula (1) in the pigment dispersant and a preferred aspect thereof are described.
The structure comprising the formula (1) in the pigment dispersant is a moiety to adsorb to the coloring material and is also called “adsorption moiety”. R4 in the formula (1) is a moiety responsible mainly for a π-π interaction with a coloring material. Accordingly, R4 only needs to be a compound having π-planarity. Of those compounds, a heterocyclic compound or an aromatic compound substituted with a polar group is preferred because such compound has a hydrogen bonding property in addition to the π-planarity. The optimum structure of R4 is a benzimidazolinone structure. The structure shows high adsorptivity to the coloring material and hence further improves the coloring power of the toner.
A compound having π-planarity for compensating the adsorptivity to the coloring material of the pigment dispersant may be introduced into R3 or a structure that adjusts the solubility of the pigment dispersant in a dispersion medium such as an alkyl group may be introduced thereinto. At that time, in order not to inhibit the adsorption thereof to the coloring material, a structure that is not bulky is preferred. Specifically, R3 preferably represents an alkyl group having 1 or more and 12 or less carbon atoms or a phenyl group. The number of the carbon atoms is more preferably 2 or more and 12 or less, still more preferably 2 or more and 8 or less. In the case that R3 has such structure, the adsorption ratio of the coloring dispersant to the coloring material can be maintained and hence satisfactory coloring power of the toner is easily obtained. The alkyl group may be substituted or unsubstituted and may be linear or branched. The phenyl group may be substituted or unsubstituted. When the group is substituted the carbon atoms of the substituted group is included in the total number of the carbon atoms.
R2 represents a divalent functional group, specifically, an alkylene group having 2 or more and 4 or less carbon atoms. When R2 represents an alkylene group having 2 or more and 4 or less carbon atoms, the adsorption moiety of the pigment dispersant shows satisfactory solubility. Accordingly, the aggregation of the adsorption moieties of the molecules thereof can be suppressed and hence the coloring power of the toner is easily improved. The alkylene group may be substituted or unsubstituted and may be linear or branched. When the group is substituted the carbon atoms of the substituted group is included in the total number of the carbon atoms.
Although X, Y and Z each represent a divalent linking group, two or more of X, Y and Z each preferably represent —NH— because the structural stability of the compound represented by the formula (1) is improved. In particular, X and Z each preferably represent —NH—. That is because when Z represents —NH—, an amide bond is formed to have an advantageous effect on the adsorption to the coloring material. In addition, X preferably represents —NH— in terms of production. To diversify the structure of R3, Y optimally represents —O— because many commercial reagents in each of which Y represents —O— are available.
L1 is a linking portion to a polymer portion and represents an amide bond or an ester bond from the viewpoint of ease of production.
In view of the foregoing, the adsorption moiety of the pigment dispersant of the present disclosure preferably has a structure represented by the following formula (3):
in the formula (3), L1 represents an ester bond or an amide bond, R1 represents a hydrogen atom or a methyl group, R5 represents an alkylene group having 2 or more and 4 or less carbon atoms, and R7 represents a hydrogen atom, a substituted or unsubstituted phenyl group, an aralkyl group, a linear, branched or cyclic alkyl group having 1 or more and 18 or less carbon atoms or a monovalent group derived by substituting at least one of methylene groups of an alkyl group having 2 or more and 18 or less carbon atoms with an ether bond, an ester bond or an amide bond.
When the coloring dispersant has the structure represented by the formula (3) as the adsorption moiety, the stability of the compound is improved because of the above-mentioned reason and hence the adsorptivity of the pigment dispersant to the coloring material is improved. As a result, the toner with satisfactory coloring power is easily obtained.
In addition, the structure represented by the formula (1) may have such tautomeric structures as represented below. Those tautomers also fall within the scope of the pigment dispersant to be used in the present disclosure.
Next, details about the polymer moiety are described. The polymer moiety (also called “dispersion moiety”) is the structure between the structures represented by the formula (1). The polymer moiety includes the structure represented by the formula (2). The structure represented by the formula (2) can be obtained by polymerizing an ester compound of acrylic acid and long-chain alkyl monoalcohol such as behenyl acrylate as the monomer.
The polymer moiety preferably contains a structure derived from any one of the following monomers in addition to a predetermined amount of the monomer unit represented by the formula (2) described above.
Examples of the monomer include: styrene and styrene derivatives, such as α-methylstyrene, β-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, p-n-butylstyrene, p-tert-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene, p-n-dodecylstyrene, p-methoxystyrene and p-phenylstyrene; acrylic polymerizable monomers, such as acrylic acid, methyl acrylate, ethyl acrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, iso-butyl acrylate, tert-butyl acrylate, n-amyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, n-nonyl acrylate, n-lauryl acrylate, cyclohexyl acrylate, 2-methoxyethyl acrylate, benzyl acrylate, dimethylphosphate ethyl acrylate, diethylphosphate ethyl acrylate, dibutylphosphate ethyl acrylate and 2-benzoyloxyethyl acrylate; methacrylic polymerizable monomers, such as methacrylic acid, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, iso-propyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate, tert-butyl methacrylate, n-amyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, n-nonyl methacrylate, 2-methoxyethyl methacrylate, diethylphosphate ethyl methacrylate and dibutylphosphate ethyl methacrylate; and acrylonitrile and methacrylonitrile.
The polymer moiety may be produced by using any one of the following polymerization methods: solution polymerization, suspension polymerization, emulsion polymerization, dispersion polymerization, precipitation polymerization and bulk polymerization. Of those, solution polymerization in a solvent that can dissolve the respective components to be used at the time of the production is preferred, though a method for the production is not particularly limited. Specific examples of the solvent include: polar organic solvents including alcohols, such as methanol, ethanol and 2-propanol, ketones, such as acetone and methyl ethyl ketone, ethers, such as tetrahydrofuran and diethyl ether, ethylene glycol monoalkyl ethers or acetates thereof, propylene glycol monoalkyl ethers or acetates thereof and diethylene glycol monoalkyl ethers; and non-polar solvents including toluene and xylene. Those solvents may be used alone or as a mixture thereof.
The pigment dispersant preferably has a melting point derived from the polymer moiety of 50° C. or more and 70° C. or less in DSC measurement. When the pigment dispersant has a melting point of 50° C. or more and 70° C. or less, the pigment dispersant is excellent in thermal deformability and has satisfactory storage stability. The melting point may be adjusted by the content of the monomer unit represented by the formula (2) and the kind and content of any other monomer.
Next, a method of producing the pigment dispersant according to the present disclosure is described. The pigment dispersant to be used in the present disclosure may be obtained by: copolymerizing a compound obtained by introducing a polymerizable group into the adsorption moiety and a monomer for forming a dispersion moiety; or forming a polymer moiety containing a functional group which can react with an intermediate compound of the adsorption moiety in advance and then adding the intermediate compound of the adsorption moiety to the polymer via the functional group. In each of the production methods, the pigment dispersant may be obtained by a known synthesis method or polymerization method. For example, the pigment dispersant may be synthesized in accordance with the following scheme.
In the scheme, the symbol “-co-” means copolymerization and “m” and “n” represent the numbers of repetitions of the respective structural units.
The adsorption moiety having introduced thereinto the polymerizable functional group in the scheme may be polymerized with the dispersion moiety monomer by a conventionally known method, such as radical polymerization, living radical polymerization, anionic polymerization or cationic polymerization, to provide a dispersant. In the dispersant, the adsorption moiety and the dispersion moiety may be present under a random state or may be present under a blocked state.
A reaction temperature and a reaction time in each step, the kinds of a solvent, a catalyst and the like to be used, a purification method after the synthesis and the like only need to be appropriately selected in accordance with a target product. The molecular structure of the synthesized adsorption moiety and the physical properties of the polymerized dispersant may be identified by using, for example, a nuclear magnetic resonator (NMR), an infrared spectrophotometer (IR), a mass spectrometer (MS) and gel permeation chromatography (GPC).
Meanwhile, when the compound of the present disclosure is added to the polymer polymerized in advance, there is a need to cause a functional group, which can subject the polymer before the addition to an addition reaction with the compound, to exist in advance. A known method may be utilized therefor.
Examples of the crystalline resin include a vinyl resin, a polyester resin, a polyurethane resin and an epoxy resin each having crystallinity. Of those, a vinyl resin or a polyester resin having crystallinity is preferred. A vinyl resin having crystallinity is more preferred.
In the case that the crystalline resin has the vinyl resin having crystallinity, a unit represented by the formula (4) is preferably incorporated thereinto:
in the formula (4), R21 represents a hydrogen atom or a methyl group, L2 represents a single bond, an ester bond or an amide bond, and “n” represents an integer of 15 or more and 30 or less.
The presence of the unit represented by the formula (4) facilitates the formation of a side-chain crystal structure. Accordingly, the toner obtains a sharp melt property and is more easily improved in low-temperature fixability. “n” in the formula (4) represents preferably 17 or more and 29 or less, more preferably 19 or more and 23 or less.
The vinyl resin may have any other monomer unit in addition to the unit represented by the formula (4). A method including copolymerizing the unit represented by the formula (4) and any other polymerizable monomer is available as a method for the introduction of the other monomer unit. The structure represented by the formula (4) can be obtained for example by polymerizing behenyl acrylate as the monomer.
Examples of the other polymerizable monomer include the following monomers.
Examples of the monomer include: styrene and styrene derivatives, such as α-methylstyrene, β-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, p-n-butylstyrene, p-tert-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene, p-n-dodecylstyrene, p-methoxystyrene and p-phenylstyrene; acrylic polymerizable monomers, such as acrylic acid, methyl acrylate, ethyl acrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, iso-butyl acrylate, tert-butyl acrylate, n-amyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, n-nonyl acrylate, n-lauryl acrylate, cyclohexyl acrylate, 2-methoxyethyl acrylate, benzyl acrylate, dimethylphosphate ethyl acrylate, diethylphosphate ethyl acrylate, dibutylphosphate ethyl acrylate, 2-benzoyloxyethyl acrylate and acrylonitrile; and methacrylic polymerizable monomers, such as methacrylic acid, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, iso-propyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate, tert-butyl methacrylate, n-amyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, n-nonyl methacrylate, 2-methoxyethyl methacrylate, diethylphosphate ethyl methacrylate, dibutylphosphate ethyl methacrylate and methacrylonitrile.
Of those, styrene, methacrylic acid, acrylic acid, methyl (meth)acrylate, acrylonitrile or methacrylonitrile is preferably used.
A polarity parameter P1 of the pigment dispersant and a polarity parameter P2 of the crystalline resin preferably satisfy the following formula:
|P1−P2|≤0.10
where P1 represents a volume fraction of acetonitrile at a precipitation point of the pigment dispersant determined by adding 0.10 part by mass of acetonitrile to a solution formed of 0.05 part by mass of the pigment dispersant and 1.48 parts by mass of chloroform, and P2 represents a volume fraction of acetonitrile at a precipitation point of the crystalline resin when 0.10 part by mass of acetonitrile is added to a solution formed of 0.05 part by mass of the crystalline resin and 1.48 parts by mass of chloroform.
The values of the polarity parameters of the pigment dispersant and the crystalline resin are preferably as close as possible to each other because the affinity therebetween is improved.
The P1 may be controlled by changing the composition of the polymer moiety of the pigment dispersant. The P2 may be controlled by changing the composition of the crystalline resin. Details about a method of measuring the polarity parameters are described later.
The binder resin preferably contains an amorphous resin as other resin. It is preferred that when a section of the toner particle is observed with a scanning transmission electron microscope, the section have a matrix-domain structure, the crystalline resin be incorporated as a main component into a matrix and the amorphous resin be incorporated as a main component into a domain. In this case, the toner is excellent in durability and hot offset resistance. Examples of the amorphous resin include a vinyl resin, a polyester resin, a polyurethane resin and an epoxy resin. Of those, a vinyl resin is preferred.
Although the incorporation of the crystalline resin as the main component in the matrix as described above makes the above-mentioned characteristics excellent, the crystalline resin in the matrix is liable to affect the dispersion of the pigment to cause a reduction in coloring power of the toner. However, the use of the pigment dispersant of the present disclosure enables the dispersion of the pigment without any influence of the crystalline resin in the matrix and hence provides the toner with high coloring power.
The pigment preferably contains any of the following groups: carbon black; C.I.Pigment Yellow74, C.I.Pigment Yellow93, C.I.Pigment Yellow139, C.I.Pigment Yellow155, C.I.Pigment Yellow180, C.I.Pigment Yellow185, C.I.Pigment Red31, C.I.Pigment Red122, C.I.Pigment Red150, C.I.Pigment Red170, C.I.Pigment Red258, C.I.Pigment Red269, C.I.Pigment Blue15:3, and C.I.Pigment Blue15:4.
When the pigment is one of the above-mentioned groups, the adsorption of the pigment dispersant to the pigment caused by a π-π interaction or a hydrogen bonding action acts more strongly. Accordingly, the pigment dispersant easily intervenes near the pigment and hence easily improves the dispersibility of the pigment.
Of those, carbon black, C.I. Pigment Yellows 155, 180 and 185, C.I. Pigment Reds 122 and 150 and C.I. Pigment Blue 15:3 are more preferred.
In addition, the content of the pigment dispersant with respect to the pigment is preferably 1.0 part by mass or more and 20 parts by mass or less, more preferably 3.0 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the pigment.
The toner particle according to the present invention can have wax. A wax having a number-average molecular weight (Mn) of 300 or more and 3,000 or less is preferably used as a wax because releasability is easily secured. Although the kind of the wax is not particularly limited, a hydrocarbon-based wax or an ester wax is preferred.
Examples of the hydrocarbon-based wax include the following waxes.
Aliphatic hydrocarbon-based wax: low-molecular-weight polyethylene, low-molecular-weight polypropylene, a low-molecular-weight olefin copolymer, a Fischer-Tropsch wax or a wax obtained by subjecting any one of these compounds to oxidation or acid addition.
The ester wax only needs to have at least one ester bond in a molecule thereof and any one of a natural ester wax and a synthetic ester wax may be used.
Although the ester wax is not particularly limited, the wax is one of an ester of an alcohol that is tetrahydric or more and octahydric or less and an aliphatic monocarboxylic acid or an ester of a carboxylic acid that is tetravalent or more and octavalent or less and an aliphatic monoalcohol. Examples of the ester wax include the following waxes: esters of monohydric alcohols and monocarboxylic acids, such as behenyl behenate, stearyl stearate and palmityl palmitate; esters of divalent carboxylic acids and monoalcohols, such as dibehenyl sebacate; esters of dihydric alcohols and monocarboxylic acids, such as ethylene glycol distearate and hexanediol dibehenate; esters of trihydric alcohols and monocarboxylic acids, such as glycerin tribehenate; esters of tetrahydric alcohols and monocarboxylic acids, such as pentaerythritol tetrastearate and pentaerythritol tetrapalmitate; esters of hexahydric alcohols and monocarboxylic acids, such as dipentaerythritol hexastearate, dipentaerythritol hexapalmitate and dipentaerythritol hexabehenate; esters of polyfunctional alcohols and monocarboxylic acids, such as polyglycerin behenate; and natural ester waxes, such as carnauba wax and rice wax.
Of those, esters of hexahydric alcohols and monocarboxylic acids, such as dipentaerythritol hexastearate, dipentaerythritol hexapalmitate and dipentaerythritol hexabehenate, are preferred. The wax interacts with the pigment dispersant of the present disclosure and hence the domain size of the wax reduces. Accordingly, the uneven distribution of the pigment in the toner particle is eliminated and hence the coloring power and color gamut of the toner are further improved.
Although any production method may be used as a production method for the production of the toner particle according to the present disclosure, the toner particle is preferably obtained by a method of producing a toner particle including granulating a polymerizable monomer composition in an aqueous medium, such as a suspension polymerization method, an emulsion polymerization method or a suspension granulation method.
The method of producing the toner particle is described below by using the suspension polymerization method that is most suitable out of the methods of producing the toner particle to be used in the present disclosure.
In addition to the pigment dispersant, the pigment, the crystalline resin and the wax described above, a polymerizable monomer that produces the other resin of the binder resin and any other additive to be used as required are uniformly dissolved or dispersed with a dispersing machine, such as a homogenizer, a ball mill, a colloid mill or an ultrasonic dispersing machine. A polymerization initiator is dissolved in the resultant to prepare a polymerizable composition. Next, the polymerizable composition is suspended in an aqueous medium containing a dispersion stabilizer and polymerized. Thus, the toner particle is produced.
Examples of a monofunctional polymerizable monomer serving as the polymerizable monomer include: styrene and styrene derivatives, such as α-methylstyrene, β-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, p-n-butylstyrene, p-tert-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene, p-n-dodecylstyrene, p-methoxystyrene and p-phenylstyrene; acrylic polymerizable monomers, such as methyl acrylate, ethyl acrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, iso-butyl acrylate, tert-butyl acrylate, n-amyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, n-nonyl acrylate, cyclohexyl acrylate, benzyl acrylate, dimethylphosphate ethyl acrylate, diethylphosphate ethyl acrylate, dibutylphosphate ethyl acrylate and 2-benzoyloxyethyl acrylate; and methacrylic polymerizable monomers, such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, iso-propyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate, tert-butyl methacrylate, n-amyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, n-nonyl methacrylate, diethylphosphate ethyl methacrylate and dibutylphosphate ethyl methacrylate.
In addition, examples of a polyfunctional polymerizable monomer serving as the polymerizable monomer include diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, tripropylene glycol diacrylate, polypropylene glycol diacrylate, 2,2′-bis(4-(acryloxydiethoxy)phenyl)propane, trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, polypropylene glycol dimethacrylate, 2,2′-bis(4-(methacryloxydiethoxy)phenyl)propane, 2,2′-bis(4-(methacryloxypolyethoxy)phenyl)propane, trimethylolpropane trimethacrylate, tetramethylolmethane tetramethacrylate, divinylbenzene, divinylnaphthalene and divinyl ether.
The monofunctional polymerizable monomers may be used alone or in combination thereof. The monofunctional polymerizable monomer and the polyfunctional polymerizable monomer may be used in combination. Alternatively, the polyfunctional polymerizable monomers may be used alone or in combination thereof. The polymerization initiator may be added simultaneously with the addition of the other additive into the polymerizable monomer or may be mixed immediately before the suspension in the aqueous medium. In addition, the polymerization initiator dissolved in the polymerizable monomer or a solvent may be added immediately after the granulation and before the initiation of the polymerization reaction.
The pigment is preferably used in an amount of 1.0 part by mass or more and 20.0 parts by mass or less with respect to 100.0 parts by mass of the binder resin containing a crystalline resin.
Examples of the polymerization initiator include an organic peroxide-based initiator and an azo-based polymerization initiator. Examples of the organic peroxide-based initiator include the following initiators: benzoyl peroxide, lauroyl peroxide, di-a-cumyl peroxide, 2,5-dimethyl-2,5-bis(benzoylperoxy)hexane, bis(4-t-butylcyclohexyl)peroxydicarbonate, 1,1-bis(t-butylperoxy)cyclododecane, t-butylperoxymaleate, bis(t-butylperoxy)isophthalate, methyl ethyl ketone peroxide, tert-butylperoxy-2-ethylhexanoate, diisopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide and tert-butyl-peroxypivalate.
Examples of the azo-based polymerization initiator include 2,2′-azobis-(2,4 dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1′-azobis(cyclohexane-1-carbonitrile), 2,2′-azobis-4-methoxy-2,4-dimethylvaleronitrile and azobismethylbutyronitrile.
In addition, a redox-type initiator obtained by combining an oxidizing substance and a reducing substance may be used as the polymerization initiator. Examples of the oxidizing substance include: inorganic peroxides, such as hydrogen peroxide and persulfate salts (a sodium salt, a potassium salt and an ammonium salt); and an oxidizing metal salt such as a tetravalent cerium salt. Examples of the reducing substance include reducing metal salts (a divalent iron salt, a monovalent copper salt and a trivalent chromium salt), ammonia, lower amines (amines each having about 1 to about 6 carbon atoms, such as methylamine and ethylamine), an amino compound such as hydroxylamine, sodium thiosulfate, sodium hydrosulfite, sodium hydrogen sulfite, sodium sulfite, a reducing sulfur compound such as sodium formaldehyde sulfoxylate, lower alcohols (having 1 to 6 carbon atoms), ascorbic acid and salts thereof and lower aldehydes (having 1 to 6 carbon atoms).
The polymerization initiator is selected with reference to a 10-hour half-life temperature and the initiators are utilized alone or as a mixture thereof. Although the addition amount of the polymerization initiator varies depending on a target polymerization degree, the initiator is generally added in an amount of 0.5 part by mass or more to 20.0 parts by mass or less with respect to 100.0 parts by mass of the polymerizable monomer.
In addition, a known chain transfer agent and a known polymerization inhibitor may be further added and used for controlling a polymerization degree.
Various cross-linking agents may each be used in the polymerization of the polymerizable monomer. Examples of the cross-linking agent include polyfunctional compounds, such as divinylbenzene, 4,4′-divinylbiphenyl, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, glycidyl acrylate, glycidyl methacrylate, trimethylolpropane triacrylate and trimethylolpropane trimethacrylate.
A known inorganic compound dispersion stabilizer and a known organic compound dispersion stabilizer may each be used as the dispersion stabilizer to be used at the time of the preparation of the aqueous medium. Examples of the inorganic compound dispersion stabilizer include tricalcium phosphate, magnesium phosphate, aluminum phosphate, zinc phosphate, calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate, barium sulfate, bentonite, silica and alumina. Meanwhile, examples of the organic compound dispersion stabilizer include polyvinyl alcohol, gelatin, methyl cellulose, methylhydroxypropyl cellulose, ethyl cellulose, carboxymethyl cellulose sodium salt, polyacrylic acid and salts thereof and starch. The usage amount of those dispersion stabilizers is preferably 0.2 part by mass or more and 20.0 parts by mass or less with respect to 100.0 parts by mass of the polymerizable monomer.
When the inorganic compound dispersion stabilizer is used out of those dispersion stabilizers, a commercial product may be used as it is, but the inorganic compound may be produced in the aqueous medium for obtaining a dispersion stabilizer having a smaller particle diameter. In the case of, for example, tricalcium phosphate, the inorganic compound is obtained by mixing an aqueous solution of sodium phosphate and an aqueous solution of calcium chloride under high stirring.
In the present disclosure, the toner preferably includes an external additive externally added to the toner particle for an improvement in image quality. Inorganic fine powder, such as silica fine powder, titanium oxide fine powder or aluminum oxide fine powder, is suitably used as the external additive.
Such inorganic fine powder is preferably subjected to hydrophobic treatment with a hydrophobizing agent, such as a silane coupling agent, a silicone oil or a mixture thereof.
Further, in the toner of the present disclosure, an external additive except those described above may be mixed in the toner particle as required.
The total addition amount of the inorganic fine powder is preferably 1.0 part by mass or more and 5.0 parts by mass or less with respect to 100.0 parts by mass of the toner particle (toner particle before the addition of the external additive).
Methods of measuring various physical properties according to the present disclosure are described below.
The structures of the pigment dispersant and the crystalline resin were determined with the following apparatus. 13C—NMR:
In the 13C—NMR, composition analysis was performed through quantification by an inverse gated decoupling method including using chromium(III) acetylacetonate as a relaxation reagent.
After the molar composition ratios of the respective monomer units of the pigment dispersant and the crystalline resin had been calculated by the above-mentioned measurement, the mass composition ratios thereof were determined from the molecular weights of the respective monomer units.
The weight-average molecular weight (Mw) of each of the toner and the pigment dispersant is measured by gel permeation chromatography (GPC) as described below.
A sample is dissolved in tetrahydrofuran (THF) at room temperature. Then, the resultant solution is filtered with a solvent-resistant membrane filter “Myshoridisk” (manufactured by Tosoh Corporation) having a pore diameter of 0.2 μm to provide a sample solution. The concentration of a THF-soluble component in the sample solution is adjusted to 0.8 mass %. Measurement is performed with the sample solution under the following conditions.
At the time of the calculation of the molecular weight of the sample, a molecular weight calibration curve prepared with standard polystyrene resins (e.g., product names “TSK Standard Polystyrenes F-850, F-450, F-288, F-128, F-80, F-40, F-20, F-10, F-4, F-2, F-1, A-5000, A-2500, A-1000 and A-500” each manufactured by Tosoh Corporation) is used.
The polarity parameter P1 in the present disclosure was measured by the following method.
50 Milligrams (0.05 g) of the pigment dispersant is loaded into an 8-milliliter sample bottle and dissolved in 1.48 g of chloroform, followed by the measurement of the initial mass (W1) of the solution. A stirring bar is loaded into the sample bottle and (a) 100 mg (0.1 g) of acetonitrile is dropped into the solution while the solution is stirred with a magnetic stirrer, followed by the continuation of the stirring for 20 seconds. (b) Whether or not the mixture becomes clouded is visually observed. When the mixture does not become clouded, the operations (a) and (b) are repeatedly performed. At the point (precipitation point) at which the cloudiness is observed, the operations are stopped and the mass (W2) of the mixture is measured. All the measurements are performed at 25° C. and normal pressure.
The P1 is calculated in accordance with the following equation.
The P2 is measured in the same manner except that in the above-mentioned measurement method, the pigment dispersant is changed to the crystalline resin.
The melting point of the pigment dispersant or the like is measured with a differential scanning calorimeter “Q1000” (manufactured by TA Instruments, Inc.) in conformity with ASTM D3418-82.
The melting points of indium and zinc are used for the temperature correction of the detecting portion of the calorimeter and the heat of fusion of indium is used for heat quantity correction.
Specifically, 5 mg of a sample is precisely weighed and the sample is loaded into a pan made of aluminum. An empty pan made of aluminum is used as a reference and the melting point of the sample is measured in the measurement temperature range of from 0° C. or more and 150° C. or less at a rate of temperature increase of 10° C./min. In the measurement, the temperature of the sample is increased to 150° C. once and subsequently decreased to 0° C., followed by the performance of a temperature increase again. The peak temperature of the maximum endothermic peak of a DSC curve in the temperature range of from 0° C. or more and 150° C. or less in the second temperature increase process is defined as the melting point of the sample.
The state of presence of the matrix-domain structure (sea-island structure) in the section of the toner is recognized by observing the section of the toner with a scanning transmission electron microscope. The observation of the section of the toner is performed after the performance of ruthenium staining. That is, the sectional image of the toner is a sectional image of the toner subjected to the ruthenium staining. A procedure for the observation of the section of the toner is as described below.
The toner is embedded in a visible light-curable resin (D-800, manufactured by Nisshin-EM) so that a state in which the toner is dispersed therein to the extent possible may be established, followed by the cutting of the embedded product into a thickness of 100 nm with an ultrasonic ultramicrotome (UC7, manufactured by Leica Camera AG).
The resultant flaky sample is stained with a vacuum staining apparatus (VSC4R1H, manufactured by Filgen, Inc.) in a RuO4 gas atmosphere at 500 Pa for 15 minutes and a STEM image thereof is taken with a scanning transmission electron microscope (JEM-2800, JEOL Ltd.). In the above-mentioned staining conditions, a difference in degree of staining occurs between the crystalline resin and the amorphous resin and hence the state of presence of the matrix-domain structure can be recognized by the contrast difference.
Observation conditions are as follows: an acceleration voltage, a STEM probe size, an image size and a magnification are set to 200 kV, 1 nm, 1,024×1,024 pixels and 30,000, respectively; and a dark field (STEM-DF) image is taken.
The contrast and brightness of the microscope are adjusted so that in a brightness histogram obtained with the following ImageJ, a brightness when a portion containing a resin component as a main component has the maximum number of pixels may be 150.
When the brightness is from 140 to 160, the brightness may be adjusted with Microsoft Photo.
A precision particle size distribution-measuring apparatus based on a pore electrical resistance method (product name: Coulter Counter Multisizer 3) and dedicated software (product name: Beckman Coulter Multisizer 3 Version 3.51, manufactured by Beckman Coulter, Inc.) are used. An aperture diameter of 100 μm is used and measurement is performed at a number of effective measurement channels of 25,000, followed by the analysis of measurement data to calculate the weight-average particle diameter (D4) and number-average particle diameter (D1) of the toner particles. An electrolyte aqueous solution prepared by dissolving special-grade sodium chloride in ion-exchanged water so as to have a concentration of 1% by mass, such as ISOTON II (product name) manufactured by Beckman Coulter, Inc., may be used in the measurement. The dedicated software is set as described below prior to the measurement and the analysis.
In the “change standard measurement method (SOM)” screen of the dedicated software, the total count number of a control mode is set to 50,000 particles, the number of times of measurement is set to 1 and a value obtained by using standard particles each having a particle diameter of 10.0 μm (manufactured by Beckman Coulter, Inc.) is set as a Kd value. A threshold and a noise level are automatically set by pressing a threshold/noise level measurement button. In addition, a current is set to 1,600 μA, a gain is set to 2, an electrolyte solution is set to ISOTON II (product name) and a check mark is placed in a check box as to whether the aperture tube is flushed after the measurement.
In the “setting for conversion from pulse to particle diameter” screen of the dedicated software, a bin interval is set to a logarithmic particle diameter, the number of particle diameter bins is set to 256 and a particle diameter range is set to the range of from 2 μm or more and 60 μm or less.
A specific measurement method is as described below.
(1) 200 mL of the electrolyte aqueous solution is charged into a 250 mL round-bottom beaker made of glass dedicated for the Multisizer 3. The beaker is set in a sample stand and the electrolyte aqueous solution in the beaker is stirred with a stirrer rod at 24 rotations/sec in a counterclockwise direction. Then, dirt and bubbles in the aperture tube are removed by the “aperture flush” function of the analysis software.
(2) 30 mL of the electrolyte aqueous solution is charged into a 100 mL flat-bottom beaker made of glass. 0.3 mL of a diluted solution prepared by diluting Contaminon N (product name) (a 10% by mass aqueous solution of a neutral detergent for washing a precision measuring device, manufactured by Wako Pure Chemical Industries, Ltd.) with ion-exchanged water by three mass fold is added to the electrolyte aqueous solution.
(3) A predetermined amount of ion-exchanged water and 2 mL of Contaminon N (product name) are added into the water tank of an ultrasonic dispersing unit (product name: Ultrasonic Dispersion System Tetra 150, manufactured by Nikkaki Bios Co., Ltd.) having an electrical output of 120 W in which two oscillators each having an oscillatory frequency of 50 kHz are built so as to be under the state of being out of phase by 180°.
(4) The beaker in the section (2) is set in the beaker fixing hole of the ultrasonic dispersing unit and the ultrasonic dispersing unit is operated. Then, the height position of the beaker is adjusted in order that the liquid surface of the electrolyte aqueous solution in the beaker may resonate with an ultrasonic wave from the ultrasonic dispersing unit to the fullest extent possible.
(5) 10 mg of the toner (particles) is gradually added to and dispersed in the electrolyte aqueous solution in the beaker in the section (4) under a state in which the electrolyte aqueous solution is irradiated with the ultrasonic wave. Then, the ultrasonic dispersion treatment is continued for an additional 60 seconds. The temperature of water in the water tank is appropriately adjusted to from 10° C. to 40° C. in the ultrasonic dispersion.
(6) The electrolyte aqueous solution in the section (5) in which the toner (particles) has been dispersed is added dropwise with a pipette to the round-bottom beaker in the section (1) placed in the sample stand and the concentration of the particles to be measured is adjusted to 5%. Then, measurement is performed until the particle diameters of 50,000 particles are measured.
(7) The measurement data is analyzed with the dedicated software included with the apparatus and the weight-average particle diameter (D4) is calculated. An “average diameter” on the “analysis/volume statistics (arithmetic average)” screen of the dedicated software when the dedicated software is set to show a graph in a vol % unit is the weight-average particle diameter (D4). An “average diameter” on the “analysis/number statistics (arithmetic average)” screen thereof when the dedicated software is set to show a graph in a number % unit is the number-average particle diameter (D1).
The present disclosure is specifically described by way of Production Examples and Examples described below. However, the present disclosure is by no means limited by those examples. The terms “part(s)” and “%” in Production Examples and Examples mean “part(s) by mass” and “% by mass,” respectively unless otherwise stated.
Compound (A1) was synthesized in accordance with the following synthesis scheme.
First, Intermediate (1) was synthesized with reference to the description of Synthesis Example 1 of Japanese Patent Application Laid-Open No. H10-316643. Specifically, 20.6 parts (0.129 mol) of diethyl malonate, 19.8 parts (0.128 mol) of 2-methacryloyloxyethyl isocyanate (product name: “KARENZ MOI”, manufactured by Showa Denko K.K.) and 0.284 part (1.29 mmol) of 2,6-di-tert-butyl-p-cresol were dissolved in 100 parts (0.942 mol) of xylene and the solution was heated to 60° ° C. 0.214 Part (3.96 mmol) of sodium methoxide was loaded into the solution and the mixture was subjected to a reaction for 8 hours, followed by the loading of 200 parts (11.1 mol) of water to stop the reaction. The organic layer was extracted with toluene and concentrated, followed by the crystallization of the resultant residue with toluene. Thus, Intermediate (1) represented by the above-mentioned formula was obtained.
Next, 19.8 parts (62.8 mmol) of Intermediate (1), 11.4 parts (76.4 mmol) of 5-amino-2-benzimidazolinone and 0.138 part (0.626 mmol) of 2,6-di-tert-butyl-p-cresol were dissolved in 141 parts (1.93 mol) of N,N-dimethylformamide and the solution was stirred under heating at 80° ° C. for 6 hours to be subjected to a reaction. After the reaction, N,N-dimethylformamide was evaporated under reduced pressure and 300 parts (16.7 mol) of water was loaded into the resultant residue. The precipitate was filtered out to provide Compound (A1) represented by the above-mentioned formula.
Compound (A2) was synthesized in accordance with the following synthesis scheme.
Compound (A2) represented by the above-mentioned formula was synthesized by the same method as in the synthesis of Compound (A1) described above except that in the synthesis of Compound (A1), 5-amino-2-benzimidazolinone was changed to 3-aminophenyl ureide.
Compound (A3) was synthesized in accordance with the following synthesis scheme.
14.5 Parts (62.4 mmol) of triethyl carboxymalonate, 11.5 parts (76.1 mmol) of 3-aminophenyl ureide and 0.138 part (0.626 mmol) of 2,6-di-tert-butyl-p-cresol were dissolved in 141 parts (1.93 mol) of N,N-dimethylformamide and the solution was stirred under heating at 80° C. for 6 hours to be subjected to a reaction. After the reaction, N,N-dimethylformamide was evaporated under reduced pressure and 300 parts (16.7 mol) of water was loaded into the resultant residue. The precipitate was filtered out to provide Intermediate (2) represented by the above-mentioned formula.
18.9 Parts (56.0 mmol) of Intermediate (2), 50.0 parts (0.684 mol) of N,N-dimethylformamide, 0.124 part (0.563 mmol) of 2,6-di-tert-butyl-p-cresol and 5.05 parts (84.0 mmol) of ethylenediamine were mixed and the mixture was stirred under heating at 80° C. for 6 hours to be subjected to a reaction. After the reaction, N,N-dimethylformamide was evaporated under reduced pressure and 300 parts (16.7 mol) of water was loaded into the resultant residue. The precipitate was filtered out to provide Compound (A3) represented by the above-mentioned formula.
Next, pigment dispersants (Sy-1) to (Sy-12) and (Sy-19) to be used in the present disclosure and pigment dispersants (Sy-13) to (Sy-18) to be used in Comparative Examples were synthesized by using Compounds (A1) to (A3) thus synthesized.
(Synthesis of Pigment Dispersant (Sy-1)) 64.3 Parts of behenyl acrylate, 27.8 parts of styrene, 7.8 parts of Compound (A1) and 1.5 parts of azobisisobutyronitrile were loaded into a recovery flask purged with nitrogen and the mixture was stirred at 80° C. The polymerization of the mixture was advanced while the molecular weight thereof was monitored by GPC. When the molecular weight reached a desired value, the flask was cooled with ice water so that the reaction was stopped. Thus, the pigment dispersant (Sy-1) was obtained.
The resultant pigment dispersant (Sy-1) was subjected to solid-liquid separation in methanol serving as a poor solvent to be purified and then its weight-average molecular weight was measured by using GPC. The weight-average molecular weight (Mw) of the resultant pigment dispersant (Sy-1) is shown in Tables 1-1 and 1-2. In addition, the values of the melting point (Tm) and polarity parameter P1 thereof are also shown in Tables 1-1 and 1-2.
Pigment dispersants (Sy-2) to (Sy-18) and (Sy-19) were each obtained in the same manner as in the pigment dispersant (Sy-1) except that in the production example of the pigment dispersant (Sy-1), the kinds and amounts of the materials were changed so that composition shown in Tables 1-1 and 1-2 was obtained. The composition and physical properties of each of the pigment dispersants (Sy-2) to (Sy-19) are shown in Tables 1-1 and 1-2.
The terms in the table mean:
Under a nitrogen atmosphere, the following materials were loaded into a reaction vessel including a reflux condenser, a stirring machine, a temperature gauge and a nitrogen-introducing tube.
While the materials in the reaction vessel were stirred at 200 rpm, the materials were heated to 70° C. and subjected to a polymerization reaction for 12 hours. Thus, such a dissolved liquid that the polymer of a monomer composition was dissolved in toluene was obtained. After that, toluene and the remaining monomers were evaporated at 160° C. and 1 hPa. Thus, a crystalline resin C-1 was obtained.
A crystalline resin C-2 and C-5 were obtained in the same manner as in the crystalline resin C-1 except that in the preparation of the crystalline resin C-1, the materials were changed as shown in Table 2.
118.0 Parts of sebacic acid and 69.0 parts of 1,6-hexanediol were added to a reaction vessel including a stirring machine, a temperature gauge, a nitrogen-introducing tube, a dewatering tube and a decompressor and the mixture was heated to a temperature of 130° C. while being stirred. After 0.7 part of titanium(IV) isopropoxide had been added as an esterification catalyst to the mixture, the temperature of the mixture was increased to 160° C. and the mixture was subjected to condensation polymerization over 5 hours. After that, the temperature of the resultant was increased to 180° C. and while a pressure in the vessel was reduced, the resultant was subjected to a reaction until a desired molecular weight was obtained. Thus, a crystalline resin C-3 was obtained.
118.0 Parts of sebacic acid and 69.0 parts of 1,6-hexanediol were added to a reaction vessel including a stirring machine, a temperature gauge, a nitrogen-introducing tube, a dewatering tube and a decompressor and the mixture was heated to a temperature of 130° C. while being stirred. After 0.7 part of titanium(IV) isopropoxide had been added to the mixture, the temperature of the mixture was increased to 160° C. and the mixture was subjected to condensation polymerization over 5 hours. Next, 7.0 parts of acrylic acid and 50.0 parts of styrene were dropped into the vessel over 1 hour. While the temperature of the mixture was held at 160° C., the mixture was continuously stirred for 1 hour and then the monomer of a styrene resin component was removed at 8.3 kPa for 1 hour. After that, the temperature of the residue was increased to 210° C. and the residue was subjected to a reaction until a desired molecular weight was obtained. Thus, a crystalline resin C-4 was obtained.
The composition and physical properties of each of the crystalline resins C-1 to C-5 are shown in Table 2.
The above-mentioned materials were introduced into an attritor (manufactured by Mitsui Mining Co., Ltd.) and were stirred with zirconia beads (200 parts) each having a radius of 2.5 mm at 200 rpm and 25° ° C. for 180 minutes to prepare a pigment dispersion liquid 1.
The above-mentioned materials were mixed and the temperature of the mixture was warmed to 65° ° C., followed by uniform dissolution and dispersion with a TK-type homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) at 5,000 rpm for 60 minutes. Thus, a toner composition-dissolved liquid 1 was obtained.
In a 2-liter four-necked flask including a high-speed stirring device TK HOMOMIXER, 450 parts of a 0.1 M aqueous solution of Na3PO4 was loaded into 710 parts of ion-exchanged water and the temperature of the mixture was warmed to 60° ° C. After that, 67.7 parts of a 1.0 M aqueous solution of CaCl2 was gradually added to the mixture to provide an aqueous medium 1 containing a calcium phosphate compound.
While the temperature of the aqueous medium 1 and the number of revolutions of the stirring device were kept at 60° C. and 12,500 rpm, respectively, the toner composition-dissolved liquid 1 was loaded into the aqueous medium 1 and 9.0 parts of t-butylperoxypivalate serving as a polymerization initiator was added to the mixture. The mixture was granulated as it was with the stirring device for 10 minutes while its number of revolutions was maintained at 12,500 rpm.
The high-speed stirring device was changed to a stirring machine including a propeller stirring blade and the granulated product was held at 70° C. and was polymerized for 5.0 hours while being stirred at 200 rpm. After that, the temperature of the resultant was increased to 98° C. and the resultant was heated for 3.0 hours so that the remaining monomers were removed. Thus, a black toner particle dispersion liquid having dispersed therein black toner particles was obtained.
Hydrochloric acid was added to the resultant black toner particle dispersion liquid to set its pH to 1.4 and the mixture was stirred for 1 hour so that the calcium phosphate salt was dissolved. The solution was subjected to solid-liquid separation with a pressure filter under a pressure of 0.4 MPa to provide a toner cake. Next, ion-exchanged water was added to the pressure filter until the filter was filled with the water, followed by the washing of the cake at a pressure of 0.4 MPa. The washing operation was repeated three times and then the washed product was dried to provide black toner particles 1. The weight-average particle diameter (D4) of the resultant black toner particles 1 was 6.9 μm.
1.5 Parts of hydrophobic silica fine powder (number-average primary particle diameter: 10 nm) subjected to surface treatment with hexamethyldisilazane was added to 100.0 parts of the resultant black toner particles 1 and a mixing step was performed with a Henschel mixer (manufactured by Mitsui Mining Co., Ltd.) for 300 seconds to provide a black toner 1. The composition and physical properties of the black toner 1 are shown in Tables 3-1 to 3-4.
Black toners 2 to 29 were each obtained in the same manner as in the production example of the black toner 1 except that the composition of the black toner particles 1 was changed as shown in Tables 3-1 to 3-4. The composition and physical properties of each of the black toners 2 to 29 are shown in Tables 3-1 to 3-4.
StBAR measns Styrene-Butyl Acrylate Resin.
The above-mentioned materials were introduced into an attritor (manufactured by Mitsui Mining Co., Ltd.) and were stirred with zirconia beads (200 parts) each having a radius of 2.5 mm at 200 rpm and 25° ° C. for 180 minutes to prepare a pigment dispersion liquid 2.
From then on, a magenta toner 1 was obtained in the same manner as in the black toner 1. The composition and physical properties of the resultant magenta toner 1 are shown in Tables 4-1 and 4-2.
Magenta toners 2 to 5 were each obtained in the same manner as in the production example of the magenta toner 1 except that the pigment dispersant of the magenta toner 1 was changed as shown in Tables 4-1 and 4-2. The composition and physical properties of each of the magenta toners 2 to 5 are shown in Tables 4-1 and 4-2.
The above-mentioned materials were introduced into an attritor (manufactured by Mitsui Mining Co., Ltd.) and were stirred with zirconia beads (200 parts) each having a radius of 2.5 mm at 200 rpm and 25° C. for 180 minutes to prepare a pigment dispersion liquid 2.
From then on, a yellow toner 1 was obtained in the same manner as in the black toner 1. The composition and physical properties of the resultant yellow toner 1 are shown in Tables 5-1 and 5-2.
Yellow toners 2 to 5 were each obtained in the same manner as in the production example of the yellow toner 1 except that the pigment of the yellow toner 1 was changed as shown in Tables 5-1 and 5-2. The composition and physical properties of each of the yellow toners 2 to 5 are shown in Tables 5-1 and 5-2.
The above-mentioned materials were introduced into an attritor (manufactured by Mitsui Mining Co., Ltd.) and were stirred with zirconia beads (200 parts) each having a radius of 2.5 mm at 200 rpm and 25° ° C. for 180 minutes to prepare a pigment dispersion liquid 2.
From then on, a cyan toner 1 was obtained in the same manner as in the black toner 1. The composition and physical properties of the resultant cyan toner 1 are shown in Tables 6-1 and 6-2.
Cyan toners 2 to 5 were each obtained in the same manner as in the production example of the cyan toner 1 except that the pigment dispersant of the cyan toner 1 was changed as shown in Tables 6-1 and 6-2. The composition and physical properties of each of the cyan toners 2 to 5 are shown in Tables 6-1 and 6-2.
An image evaluation was performed by partially reconstructing a commercially available color laser printer [HP LaserJet Enterprise Color M555dn]. The printer was reconstructed so as to operate even when mounted only with a process cartridge for one color. In addition, the printer was reconstructed so that the temperature of its fixing unit was able to be changed to an arbitrary value.
A toner stored in a process cartridge for a black toner mounted on the color laser printer was removed from the cartridge and the inside of the cartridge was cleaned by air blowing. After that, each toner (250 g) was introduced into the process cartridge and the process cartridge refilled with the toner was mounted on the color laser printer, followed by the following image evaluations. Specific image evaluation items are as described below.
A rectangular solid image (toner laid-on level: 0.45 mg/cm2) measuring 6.5 cm by 14.0 cm was output at the center of a transfer material and used as an evaluation image. The coloring power of the toner was evaluated by measuring an image density in the evaluation image. The image density was measured with “X-Rite Color Reflection Densitometer (X-Rite 404A).” Densities were measured at the following five points of the solid image portion and their average was evaluated as the image density: upper right, upper left, central, lower right and lower left portions. Letter-size gloss paper (HP Brochure Paper 150 g, Glossy) was used as the transfer material.
A solid image (toner laid-on level: 0.45 mg/cm2) was printed on a transfer material while a fixation temperature was changed in increments of 5° C., followed by an evaluation by the following criteria. The fixation temperature is a value obtained by measuring the temperature of the surface of a fixing roller with a noncontact temperature gauge. Letter-size plain paper (Vitality, manufactured by Xerox Corporation, 75 g/m2) was used as the transfer material.
A fixed image was produced in the same manner as in the above-mentioned evaluation method and the maximum fixation temperature of the toner was evaluated. The maximum fixation temperature is defined as the maximum temperature at which no offset occurs.
5 Grams of each toner was loaded into a 50-milliliter resin-made cup and left to stand at a temperature of 60° C. and a humidity of 10% RH for 3 days. The presence or absence of an aggregate was examined and was evaluated by the following criteria.
The following test was performed: under a high-temperature and high-humidity environment (at a temperature of 32° C. and a humidity of 85% RH), a horizontal line image having a print percentage of 1% was printed out on 30,000 sheets. After the completion of the test, a halftone (toner laid-on level: 0.25 mg/cm2) image was printed out on letter-size plain paper (Vitality, manufactured by Xerox Corporation, 75 g/m2). The presence or absence of a vertical streak in a sheet delivery direction in the halftone image was observed and the developability of the toner was evaluated as described below.
The above-mentioned evaluations were performed by using the black toners 1 to 20 as toners in Examples 1 to 20, respectively by using the black toner 28 as a toner in Example 21 and by using the black toner 29 as a toner in Example 22. The evaluation results are shown in Tables 7-1 and 7-2.
The above-mentioned evaluations were performed by using the black toners 21 to 27 as toners in Comparative Examples 1 to 7, respectively. The evaluation results are shown in Tables 7-1 and 7-2. In Comparative Example 4, the evaluations of the low-temperature fixability, hot offset resistance and developability of the black toner 24 were not performed because the particles of the toner completely aggregated in the evaluation of its heat resistance.
The above-mentioned evaluations were performed by using the magenta toners 1 to 5 as toners in Examples 22 to 26, respectively. The above-mentioned evaluations were performed by using the yellow toners 1 to 5 as toners in Examples 27 to 31, respectively. The above-mentioned evaluations were performed by using the cyan toners 1 to 5 as toners in Examples 32 to 36, respectively. The evaluation results are shown in Table 8.
According to the present disclosure, the toner excellent in low-temperature fixability and coloring power can be provided.
While the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the disclosure is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2022-204137, filed Dec. 21, 2022, and Japanese Patent Application No. 2023-212233, filed Dec. 15, 2023, which are hereby incorporated by reference herein in their entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-204137 | Dec 2022 | JP | national |
| 2023-212233 | Dec 2023 | JP | national |
